CA2933303A1 - Tire for vehicle bearing heavy loads - Google Patents
Tire for vehicle bearing heavy loads Download PDFInfo
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- CA2933303A1 CA2933303A1 CA2933303A CA2933303A CA2933303A1 CA 2933303 A1 CA2933303 A1 CA 2933303A1 CA 2933303 A CA2933303 A CA 2933303A CA 2933303 A CA2933303 A CA 2933303A CA 2933303 A1 CA2933303 A1 CA 2933303A1
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- styrene
- elastomer
- tyre according
- diene
- segment
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L7/00—Compositions of natural rubber
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
- B60C1/0016—Compositions of the tread
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
- C08L53/02—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes
- C08L53/025—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes modified
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
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- Polymers & Plastics (AREA)
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- Engineering & Computer Science (AREA)
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Abstract
The present invention relates to a tire for vehicles bearing heavy loads. The tread of said tire contains a composition made of at least one elastomer matrix containing a first diene elastomer and a thermoplastic styrene elastomer. Said thermoplastic styrene elastomer is at most 50 wt% of the elastomer matrix and contains at least one rigid styrene segment and at least one flexible diene segment. The at least one flexible diene segment contains at least 20 wt% combined diene units. The combined diene units can be totally or partially hydrogenated. Said first diene elastomer is at least 50 wt% of the elastomer matrix and is selected from among the group made up of polybutadienes, butadiene copolymers, and the mixtures thereof. Said composition is also made of: at least one reinforcing filler that contains a carbon black, which is more than 50 wt% of the reinforcing filler; and a cross-linking system. Such a tire has enhanced resistance to crack propagation.
Description
Tire for vehicle bearing heavy loads The field of the present invention is that of tyres for vehicles which are intended to bear heavy loads, in particular buses, lorries, agricultural vehicles or civil engineering vehicles.
These tyres are provided with treads which exhibit, in comparison with the thicknesses of the treads of the tyres for light vehicles, in particular for passenger vehicles or vans, great thicknesses of rubber material. Typically, the wearing part of the tread of a heavy-duty vehicle has a thickness of at least 15 mm and that of a civil engineering vehicle is at least 30 mm, indeed even up to 120 mm.
During running, a tread is subjected to mechanical stresses and to attacks resulting from direct contact with the ground. In the case of a tyre fitted to a vehicle bearing heavy loads, the mechanical stresses and the attacks undergone by the tyre are magnified under the effect of the weight borne by the tyre. The consequence of this is that the incipient cracks which are created in the tread under the effect of these strains and these attacks have a tendency to further propagate at the surface of or inside the tread. Crack propagation in the tread can result in damage to the tread and can thus reduce the lifetime of the tread or of the tyre.
A tyre running over a stony ground surface is highly exposed to incipient cracks. The actual aggressive nature of the stony ground surface exacerbates not only this type of attack on the tread but also its consequences with regard to the tread. This is particularly true for the tyres equipping civil engineering vehicles which are moving about generally in mines. This is also true for the tyres which are fitted to agricultural vehicles, due to the stony ground surface of arable land. The tyres which equip heavy-duty vehicles of worksites, which are moving both on stony ground surfaces and on bituminous ground surfaces, also experience these same attacks. Due to the two aggravating factors, which are the weight borne by the tyre and the aggressive nature of the running ground surface, the resistance to crack propagation of a tread of a tyre for a civil engineering vehicle, an agricultural vehicle or a worksite heavy-duty vehicle proves to be crucial in minimizing the impact of the attacks undergone by the tread.
It is thus important to have available tyres for vehicles bearing heavy loads, the tread of which exhibits a resistance to crack propagation which is sufficiently strong to minimize the effect of an incipient crack on the lifetime of the tread. In order to solve this problem, tyre manufacturers use, for example, natural rubber in the treads due to the properties of resistance to crack propagation of natural rubber, as mentioned in Table 3.7, Comparison of elastomers properties, pp 162-163, Rubber Technology Handbook, Hofmann, Hanser Publishers (1989).
These tyres are provided with treads which exhibit, in comparison with the thicknesses of the treads of the tyres for light vehicles, in particular for passenger vehicles or vans, great thicknesses of rubber material. Typically, the wearing part of the tread of a heavy-duty vehicle has a thickness of at least 15 mm and that of a civil engineering vehicle is at least 30 mm, indeed even up to 120 mm.
During running, a tread is subjected to mechanical stresses and to attacks resulting from direct contact with the ground. In the case of a tyre fitted to a vehicle bearing heavy loads, the mechanical stresses and the attacks undergone by the tyre are magnified under the effect of the weight borne by the tyre. The consequence of this is that the incipient cracks which are created in the tread under the effect of these strains and these attacks have a tendency to further propagate at the surface of or inside the tread. Crack propagation in the tread can result in damage to the tread and can thus reduce the lifetime of the tread or of the tyre.
A tyre running over a stony ground surface is highly exposed to incipient cracks. The actual aggressive nature of the stony ground surface exacerbates not only this type of attack on the tread but also its consequences with regard to the tread. This is particularly true for the tyres equipping civil engineering vehicles which are moving about generally in mines. This is also true for the tyres which are fitted to agricultural vehicles, due to the stony ground surface of arable land. The tyres which equip heavy-duty vehicles of worksites, which are moving both on stony ground surfaces and on bituminous ground surfaces, also experience these same attacks. Due to the two aggravating factors, which are the weight borne by the tyre and the aggressive nature of the running ground surface, the resistance to crack propagation of a tread of a tyre for a civil engineering vehicle, an agricultural vehicle or a worksite heavy-duty vehicle proves to be crucial in minimizing the impact of the attacks undergone by the tread.
It is thus important to have available tyres for vehicles bearing heavy loads, the tread of which exhibits a resistance to crack propagation which is sufficiently strong to minimize the effect of an incipient crack on the lifetime of the tread. In order to solve this problem, tyre manufacturers use, for example, natural rubber in the treads due to the properties of resistance to crack propagation of natural rubber, as mentioned in Table 3.7, Comparison of elastomers properties, pp 162-163, Rubber Technology Handbook, Hofmann, Hanser Publishers (1989).
- 2 -The Applicant Companies have discovered that the combined use of a carbon black in a predominant amount as reinforcing filler, of a polybutadiene or of a butadiene copolymer and of a certain content of a specific thermoplastic elastomer in a tread makes it possible to improve the resistance to crack propagation of the tread of a tyre for a vehicle intended to bear heavy loads, without substantial damage to the other performances of the tread, which are the wear and the rolling resistance.
Thus, a first subject-matter of the invention is a tyre for vehicles which are intended to bear heavy loads, the tread of which comprises a composition based on at least:
- an elastomer matrix comprising a first diene elastomer and a thermoplastic styrene elastomer, o which thermoplastic styrene elastomer represents at most 50% by weight of the elastomer matrix and comprises at least one rigid styrene segment and at least one flexible diene segment, which at least one flexible diene segment comprises at least 20%
by weight of conjugated diene units, it being possible for the conjugated diene units to be all or in part hydrogenated, o which first diene elastomer represents at least 50% by weight of the elastomer matrix and is chosen from the group consisting of polybutadienes, butadiene copolymers and their mixtures, - a reinforcing filler which comprises a carbon black which represents more than 50% by weight of the reinforcing filler, - a crosslinking system.
Another subject-matter of the invention is a process for preparing the tyre in accordance with the invention.
I. MEASUREMENTS AND TESTS USED
Resistance to crack propagation:
The rate of cracking was measured on test specimens of rubber compositions using a cyclic fatigue device (Elastomer Test System) of the 381 type from MTS, as explained below.
The resistance to cracking is measured using repeated tensile actions on a test specimen initially accommodated (after a first tensile cycle) and then notched. The tensile test specimen is composed of a rubber plaque of parallelepipedal shape, for example with a thickness of between 1 and 2 mm, with a length between 130 and 170 mm and with a width between 10 and 15 mm, the two side edges each being covered in the direction of the length with a cylindrical rubber strip (diameter 5 mm) making possible anchoring in the jaws of the tensile testing device. The test specimens thus prepared are tested in the fresh state. The test was carried out in air, at a temperature of 20 C.
After accommodation, 3 very fine notches with a length of between 15 and 20 mm are produced using a razor blade, at mid-width and aligned in the direction of the length of the test specimen, . - 3 -one at each end and one at the centre of the latter, before starting the test.
At each tensile cycle, the degree of deformation of the test specimen is automatically adjusted so as to keep the energy restitution level (amount of energy released during the progression of the crack) constant at a value of less than or equal to approximately 500 J/m2. The crack propagation rate is measured in nanometres per cycle. The resistance to crack propagation will be expressed in relative units (r.u.) by dividing the propagation rate of the control by that of the mixture, the rates being measured at the same energy restitution level. A value greater than that of the control, arbitrarily set at 100, indicates an improved result, that is to say a greater resistance to crack propagation.
II- DETAILED DESCRIPTION OF THE INVENTION
In the present description, unless expressly indicated otherwise, all the percentages (%) shown are % by weight. The abbreviation "phr" means parts by weight per hundred parts of elastomers present in the elastomer matrix, the elastomer matrix denoting all of the elastomers present in the rubber composition.
Furthermore, any interval of values denoted by the expression "between a and b" represents the range of values greater than "a" and lower than "b" (that is to say, limits a and b excluded), whereas any interval of values denoted by the expression "from a to b" means the range of values extending from "a" up to "b" (that is to say, including the strict limits a and b).
The expression "composition based on" should be understood as meaning, in the present description, a composition comprising the mixture and/or the in situ reaction product of the various constituents used, some of these base constituents (for example the elastomer, the filler or other additive conventionally used in a rubber composition intended for the manufacture of tyres) being capable of reacting or intended to react with one another, at least in part, during the various phases of manufacture of the composition intended for the manufacture of tyres.
The elastomer matrix of the rubber composition has the essential characteristic of comprising a first diene elastomer chosen from the group consisting of polybutadienes (BRs), butadiene copolymers and their mixtures.
Suitable in particular as polybutadienes are those having a content of 1,2-units of between 4% and 80% by weight of the weight of the polybutadiene or those having a content of cis-1,4- bonds of at least 90% by weight of the weight of the polybutadiene.
Suitable in particular as butadiene copolymers are the copolymers of butadiene and styrene (SBR).
The copolymers can be prepared in emulsion (ESBR) or in solution (SSBR).
Mention may be made of butadiene/styrene copolymers and in particular of those having a glass transition temperature Tg, = - 4 -measured according to ASTM D3418, of between 0 C and -90 C and more particularly between -C and -80 C, a styrene content of between 5% and 60% by weight and more particularly between 5% and 40%, a content (mol%) of 1,2- bonds of the butadiene part of between 4% and 75% of the butadiene part and a content (mol%) of trans-1,4- bonds of between 10% and 80% of 5 the butadiene part.
The first diene elastomer, whether it is a polybutadiene or a butadiene copolymer, can be modified by a modifying agent, such as, for example, a coupling, star-branching or functionalizing agent.
Mention may be made, as modifying agent, of compounds comprising a C-Sn bond or those 10 comprising an amine, silanol or alkoxysilane functional group. Such elastomers are, for example, described in Patents EP 0 778 311 B1, EP 0 890 607 B1, EP 0 692 492 B1, EP 1 000 970 B1 and EP 1 457 501 B1 or Patent Applications WO 2009/000750 and WO 2009/133068.
According to a preferred embodiment of the invention, the first diene elastomer is a polybutadiene, preferably exhibiting a content of cis-1,4- bonds of greater than or equal to 90% by weight of the weight of polybutadiene. This preferred embodiment of the invention can be combined with any one of the embodiments of the invention.
The first diene elastomer represents at least 50% by weight of the elastomer matrix. According to this embodiment, suitable as elastomer matrix is, for example, a mixture consisting of 40% by weight of the thermoplastic styrene elastomer, of 55% by weight of the first diene elastomer and of 5% by weight of a second diene elastomer, the percentages being calculated on the basis of the total weight of the elastomer matrix.
Second diene elastomer (or without distinction rubber) should be understood, in a known way, as meaning an (or several) elastomer composed, at least in part (i.e., a homopolymer or a copolymer), of diene monomer units (monomers bearing two conjugated or non-conjugated carbon-carbon double bonds), the second diene elastomer being different from the first diene elastomer and not being a thermoplastic styrene elastomer.
According to a preferred embodiment of the invention, only the first diene elastomer and the thermoplastic styrene elastomer constitute the elastomer matrix, which means that the elastomer matrix does not contain other elastomers than the first diene elastomer and the thermoplastic styrene elastomer.
The thermoplastic styrene elastomer comprises at least one rigid styrene segment and at least one flexible diene segment comprising at least 20% by weight of conjugated diene units, it being possible for the conjugated diene units to be all or in part hydrogenated. The rigid and flexible segments can be positioned linearly, or in a star or branched configuration.
A flexible segment refers to a polymer block of elastomer type and a rigid segment refers to a polymer block of thermoplastic type.
According to one embodiment of the invention, the thermoplastic styrene elastomer is a diblock.
The diblock comprises just one rigid styrene segment connected to just one flexible diene segment.
According to a preferred embodiment of the invention, the thermoplastic styrene elastomer comprises at least two rigid styrene segments. According to this preferred embodiment of the invention, generally at least two ends of chains of the thermoplastic styrene elastomer are each provided with a rigid styrene segment and the rigid styrene segments are connected via the flexible diene segment or segments. According to this preferred embodiment of the invention, the thermoplastic styrene elastomer is preferably a triblock. The triblock is then composed of two rigid styrene segments and of one flexible diene segment.
In the case where the thermoplastic styrene elastomer is a diblock, the designation of "the at least one rigid segment" denotes the rigid segment present in the thermoplastic styrene elastomer. In the cases other than a diblock, for example in the case of a triblock, the designation of "the at least one rigid segment" denotes the rigid segments present in the thermoplastic styrene elastomer.
In the case where the thermoplastic styrene elastomer is a diblock or a triblock, the designation of "the at least one flexible segment" denotes the flexible segment present in the thermoplastic styrene elastomer. In the case where the thermoplastic styrene elastomer is neither a diblock nor a triblock, the designation of "the at least one flexible segment" denotes the flexible segments present in the thermoplastic styrene elastomer.
The at least one rigid styrene segment is the homopolymer of a styrene monomer or the block or random copolymer of several styrene monomers or also the copolymer of one or more styrene monomers and of another non-styrene monomer, such as a 1,3-diene.
Styrene monomer should be understood, in the present description, as meaning styrene or a substituted styrene. Mention may be made, among substituted styrenes, for example, of methylstyrenes (for example, o-methylstyrene, m-methylstyrene or p-methylstyrene, a-methylstyrene, a,2-dinnethylstyrene, a,4-dimethylstyrene or diphenylethylene), para-(tert-butyl)styrene, chlorostyrenes (for example, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene or 2,4,6-trichlorostyrene), bromostyrenes (for example, o-bromostyrene, m-bromostyrene, p-bromostyrene, 2,4-dibromostyrene, 2,6-dibromostyrene or 2,4,6-tribromostyrene), fluorostyrenes (for example, o-fluorostyrene, m-fluorostyrene, p-fluorostyrene, 2,4-difluorostyrene, 2,6-difluorostyrene or 2,4,6-trifluorostyrene) or also para-hydroxystyrene.
According to a preferred embodiment of the invention, the at least one rigid styrene segment exhibits a glass transition temperature of greater than 80 C. Preferably, the at least one rigid styrene segment is a polystyrene.
The at least one flexible diene segment comprises at least 20% by weight of conjugated diene monomer units (also known as conjugated diene units). The at least one flexible diene segment can be the homopolymer of a conjugated diene or the block or random copolymer of several conjugated dienes or also the copolymer of one or more conjugated dienes and of at least one other non-diene monomer, such as a styrene monomer.
The content of conjugated diene units which form the flexible diene segment is preferably at least 50%, more preferably at least 60% and more preferably still at least 70% by weight of the weight of the flexible diene segment. Advantageously, it is at least 80% by weight of the weight of the flexible diene segment. These contents, whether or not they are preferred, apply to any one of the embodiments of the invention.
Suitable in particular as conjugated diene units are 1,3-butadiene units and isoprene units. The at least one flexible diene segment can be a polybutadiene, a polyisoprene or a copolymer of 1,3-butadiene and of isoprene. The copolymer of 1,3-butadiene and of isoprene can be block or random in nature.
Suitable as thermoplastic styrene elastomer are diblock copolymers, such as styrene/butadiene (SB), styrene/isoprene (SI) or styrene/butadiene/isoprene (SBI) block copolymers, or the mixture of these copolymers. In this designation, the flexible diene block is a random or block copolymer.
Suitable in particular as thermoplastic styrene elastomer are copolymers, such as styrene/butadiene/styrene (SBS), styrene/isoprene/styrene (SIS) or styrene/butadiene/isoprene/styrene (SBIS) block copolymers, or the mixture of these copolymers.
In this designation, the flexible diene block is a random or block copolymer.
Very particularly suitable is a styrene/butadiene/isoprene/styrene (SBIS) block copolymer.
According to a first alternative form of the invention, a fraction of the conjugated diene units of the at least one flexible diene segment is hydrogenated. A person skilled in the art will understand that he can equivalently use a thermoplastic styrene elastomer, the double bonds of a fraction of the conjugated diene units of the flexible diene segment of which will have been reduced to a single bond by a process other than a hydrogenation. Mention may be made, among the processes which make it possible to reduce the double bonds of the diene units to a single bond, of reductions with an aluminium hydride or with diimine, for example.
According to a second alternative form of the invention, all of the conjugated diene units of the at least one flexible diene segment are hydrogenated. A person skilled in the art will understand that he can equivalently use a thermoplastic styrene elastomer, the double bonds of all of the conjugated diene units of the flexible diene segment of which will have been reduced to a single bond by a process other than a hydrogenation.
According to this second alternative form of the invention, suitable as thermoplastic elastomer are styrene/ethylene/butylene (SEB), styrene/ethylene/propylene (SEP) or styrene/ethylene/ethylene/propylene (SEEP) block copolymers or the mixtures of these copolymers. In this designation, the hydrogenated flexible diene block is a random or block copolymer.
According to this second alternative form of the invention, also suitable as thermoplastic elastomer are styrene/ethylene/butylene/styrene (SEBS), styrene/ethylene/propylene/styrene (SEPS) or styrene/ethylene/ethylene/propylene/styrene (SEEPS) block copolymers or the mixtures of these copolymers. In this designation, the hydrogenated flexible diene block is a random or block copolymer.
Any one of the embodiments of the invention applies to the first alternative form of the invention or to the second alternative form of the invention.
Also suitable as thermoplastic styrene elastomer are the mixtures of an abovementioned triblock copolymer and of an abovementioned diblock copolymer. This is because the triblock copolymer can comprise a minor fraction by weight of diblock copolymer consisting of a rigid styrene segment and of a flexible diene segment, the rigid block and the flexible block being respectively of the same chemical nature, in particular of the same microstructure, as the rigid and flexible blocks of the triblock. The presence of the diblock copolymer in the triblock copolymer generally results from the process of synthesis of the triblock copolymer, which can result in the formation of byproduct, such as the diblock copolymer. Generally, the percentage of diblock copolymer in the triblock copolymer does not exceed 40% by weight of triblock copolymer.
According to a preferred embodiment of the invention, the content by weight of the at least one rigid styrene segment is between 5 and 40% of the weight of the thermoplastic styrene elastomer.
Below the minimum indicated, there is a risk of the thermoplastic nature of the thermoplastic styrene elastomer being substantially reduced while, above the recommended maximum, the elasticity of the composition can be affected. For these reasons, the content by weight of the at least one rigid styrene segment in the thermoplastic styrene elastomer is preferably within a range extending from 10 to 35%, more preferably from 10 to 20%, of the weight of the thermoplastic styrene elastomer. These contents, whether or not they are preferred, apply to any one of the embodiments of the invention, very particularly when the polystyrene forms the at least one rigid styrene segment of the thermoplastic styrene elastomer.
The number-average molar mass (denoted Mn) of the thermoplastic styrene elastomer is preferably between 50 000 and 500 000 g/mol, more preferably between 60 000 and 450 000 g/mol and more preferably still between 80 000 and 300 000 g/mol.
Advantageously, it is between 100 000 and 200 000 g/mol. These preferred ranges of number-average molar mass values apply whatever the embodiment of the invention.
The molar mass is determined, in a known way, by size exclusion chromatography (SEC). The sample is dissolved beforehand in tetrahydrofuran at a concentration of approximately 1 g/I and then the solution is filtered through a filter with a porosity of 0.45 p.m before injection. The apparatus used is a Waters Alliance chromatographic line. The elution solvent is tetrahydrofuran, the flow rate is 0.7 ml/min, the temperature of the system is 35 C and the analytical time is 90 min.
A set of four Waters columns in series, with the Styragel tradenames (HMW7, HMW6E and two HT6E), is used. The injected volume of the solution of the polymer sample is 100 pl. The detector is a Waters 2410 differential refractometer and its associated software, for making use of the chromatographic data, is the Waters Millennium system. The calculated number-average molar masses are relative to a calibration curve produced with polystyrene standards.
The thermoplastic styrene elastomer is present in a proportion by weight of at most 50% of the weight of the elastomer matrix of the rubber composition of the tread. Above the maximum value indicated, there is no longer a benefit with regard to the resistance to crack propagation of the rubber composition forming the tread of a tyre intended to bear heavy loads.
The content of thermoplastic styrene elastomer varies within a range extending preferably from 5 to 50%, more preferably from 10 to 45% and more preferably still from 20 to 45% by weight of the weight of the elastomer matrix. Advantageously, it varies from 25 to 45% by weight of the weight of the elastomer matrix. When the thermoplastic styrene elastomer is a mixture of unsaturated thermoplastic styrene elastomers in accordance with the invention, the contents shown apply to the mixture and not to each of the thermoplastic styrene elastomers. These contents, whether or not they are preferred, apply to any one of the embodiments of the invention.
According to a specific embodiment of the invention, the thermoplastic styrene elastomer exhibits a glass transition temperature of less than -20 C. This glass transition temperature is generally attributed to the glass temperature of the flexible diene segment of the thermoplastic styrene elastomer. The glass transition temperature is measured by means of a differential calorimeter (differential scanning calorimeter) according to Standard ASTM D3418 (1999).
According to this specific embodiment of the invention, the thermoplastic styrene elastomer exhibits a Tg preferably of less than -30 C, more preferably of less than -40 C and more preferably still of less than -50 C.
The reinforcing filler can be any type of "reinforcing" filler known for its abilities to reinforce a rubber composition which can be used for the manufacture of tyres, for example an organic filler, such as carbon black, a reinforcing inorganic filler, such as silica, with which is combined, in a known way, a coupling agent, or also a mixture of these two types of fillers.
A reinforcing filler typically consists of nanoparticles, the (weight-)average size of which is less than a micrometre, generally less than 500 nm, generally between 20 and 200 nm, in particular and more preferably between 20 and 150 nm.
According to the present invention, the reinforcing filler comprises a carbon black which represents more than 50% by weight of the reinforcing filler. Carbon black is understood to mean one or more carbon blacks. The carbon black is then regarded as the predominant reinforcing filler.
The carbon black exhibits a BET specific surface preferably of at least 90 m2/g, more preferably of at least 100 m2/g. The blacks conventionally used in tyres or their treads ("tyre-grade" blacks) are suitable as such. Mention will more particularly be made, among the latter, of the reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grade), such as, for example, the N115, N134, N234 or N375 blacks. The carbon blacks can be used in the isolated state, as available commercially, or in any other form, for example as support for some of the rubber additives used.
The carbon blacks might, for example, be already incorporated in an isoprene elastomer in the form of a masterbatch (see, for example, Application WO 97/36724 or WO
99/16600). The BET
specific surface of the carbon blacks is measured according to Standard D6556-10 [multipoint (at a minimum 5 points) method ¨ gas: nitrogen ¨ relative pressure p/po range: 0.1 to 0.3].
According to one embodiment of the invention, the reinforcing filler also comprises a reinforcing inorganic filler. The term "reinforcing inorganic filler" should be understood here as meaning any inorganic or mineral filler, whatever its colour and its origin (natural or synthetic), also known as "white filler", "clear filler" or even "non-black filler", in contrast to carbon black, capable of reinforcing, by itself alone, without means other than an intermediate coupling agent, a rubber composition intended for the manufacture of pneumatic tyres, in other words capable of replacing, in its reinforcing role, a conventional tyre-grade carbon black; such a filler is generally characterized, in a known way, by the presence of hydroxyl (¨OH) groups at its surface.
Mineral fillers of the siliceous type, preferably silica (S102), are suitable in particular as reinforcing inorganic fillers. The silica used can be any reinforcing silica known to a person skilled in the art, in particular any precipitated or fumed silica exhibiting a BET specific surface and a CTAB specific surface both of less than 450 m2/g, preferably from 30 to 400 m2/g, in particular between 60 and 300 m2/g. Mention may be made, as example of silica of use for the requirements of the invention, of the Ultrasil VN3 silica sold by Evonik. Mention will be made, as highly dispersible precipitated silicas ("HDSs"), for example, of the Ultrasil 7000 and Ultrasil 7005 silicas from Degussa, the Zeosil 1165MP, 1135MP and 1115MP silicas from Rhodia, the Hi-Sil EZ150G silica from PPG, the Zeopol 8715, 8745 and 8755 silicas from Huber or the silicas having a high specific surface as described in Application WO 03/016387.
The physical state under which the reinforcing inorganic filler is provided is not important, whether it is in the form of a powder, microbeads, granules or also beads. Of course, reinforcing inorganic filler is also understood to mean mixtures of different reinforcing inorganic fillers, in particular of highly dispersible silicas as described above.
A person skilled in the art will understand that use might be made, as filler equivalent to the reinforcing inorganic filler described in the present section, of a reinforcing filler of another nature, in particular organic nature, such as carbon black, provided that this reinforcing filler is covered with an inorganic layer, such as silica, or else comprises, at its surface, functional sites, in particular hydroxyl sites, requiring the use of a coupling agent in order to establish the bond between the filler and the elastomer. Mention may be made, by way of example, for example, of carbon blacks for tyres, such as described, for example, in patent documents WO 96/37547 and WO 99/28380.
In the present account, as regards the silica, the BET specific surface is determined in a known way by gas adsorption using the Brunauer-Emmett-Teller method described in The Journal of the American Chemical Society, Vol. 60, page 309, February 1938, more specifically according to French Standard NF ISO 9277 of December 1996 (multipoint (5 point) volumetric method -gas: nitrogen -degassing: 1 hour at 160 C - relative pressure p/po range: 0.05 to 0.17). The CTAB specific surface is the external surface determined according to French Standard NF T 45-007 of November 1987 (method B).
In order to couple the reinforcing inorganic filler to the diene elastomer, use is made, in a well-known way, of an at least bifunctional coupling agent, in particular a silane, (or bonding agent) intended to provide a satisfactory connection, of chemical and/or physical nature, between the inorganic filler (surface of its particles) and the diene elastomer. Use is made in particular of at least bifunctional organosilanes or polyorganosiloxa nes.
Use is made in particular of silane polysulphides, referred to as "symmetrical" or "unsymmetrical"
depending on their specific structure, such as described, for example, in Applications WO
03/002648 (or US 2005/016651) and WO 03/002649 (or US 2005/016650).
Particularly suitable, without the definition below being limiting, are silane polysulphides corresponding to the general formula (V):
Z - A - Sx - A - Z (V) in which:
- x is an integer from 2 to 8 (preferably from 2 to 5);
- the A symbols, which are identical or different, represent a divalent hydrocarbon radical (preferably a C1-C18 alkylene group or a C6-C12 arylene group, more particularly a C1-C10, in particular Ci-C4, alkylene, especially propylene);
- the Z symbols, which are identical or different, correspond to one of the three formulae below:
=
¨ = Si¨R1 ¨Si¨R2 ¨Si¨R2 , in which:
- the R2 radicals, which are substituted or unsubstituted and identical to or different from one another, represent a C1-C18 alkyl, C5-C18 cycloalkyl or C6-C18 aryl group (preferably C1-C6 alkyl, cyclohexyl or phenyl groups, in particular C1-C4 alkyl groups, more particularly methyl and/or ethyl);
- the R2 radicals, which are substituted or unsubstituted and identical to or different from one another, represent a C1-C18 alkoxyl or C5-C18 cycloalkoxyl group (preferably a group chosen from Ci-C8 alkoxyls and C5-C8 cycloalkoxyls, more preferably still a group chosen from C1-C4alkoxyls, in particular methoxyl and ethoxyl).
In the case of a mixture of alkoxysilane polysulphides corresponding to the above formula (I), in particular normal commercially available mixtures, the mean value of the "x"
indices is a fractional number preferably of between 2 and 5, more preferably of approximately 4.
However, the invention can also advantageously be carried out, for example, with alkoxysilane disulphides (x =
2).
Mention will more particularly be made, as examples of silane polysulphides, of bis((C1-C4)alkoxyl(C1-C4)alkylsilyl(C1-C4)alkyl) polysulphides (in particular disulphides, trisulphides or tetrasulphides), such as, for example, bis(3-trimethoxysilylpropyl) or bis(3-triethoxysilylpropyl) polysulphides. Use is made in particular, among these compounds, of bis(3-triethoxysilylpropyl) tetrasulphide, abbreviated to TESPT, of formula ((C2H50)3Si(CH2)3S2h, or bis(3-triethoxysilylpropyl) disulphide, abbreviated to TESPD, of formula [(C2H50)3Si(CH2)3Sk.
Mention will in particular be made, as coupling agent other than alkoxysilane polysulphide, of bifunctional POSs (polyorganosiloxanes), or else of hydroxysilane polysulphides, such as described in Patent Applications WO 02/30939 (or US 6 774 255) and WO 02/31041 (or US
2004/051210), or else of silanes or POSs bearing azodicarbonyl functional groups, such as described, for example, in Patent Applications WO 2006/125532, WO 2006/125533 and WO 2006/125534.
= - 12 -The content of coupling agent is advantageously less than 20 phr, it being understood that it is generally desirable to use as little as possible of it. Typically, the content of coupling agent represents from 0.5% to 15% by weight, with respect to the amount of inorganic filler. Its content is preferably between 0.5 and 12 phr, more preferably within a range extending from 3 to 10 phr.
This content is easily adjusted by a person skilled in the art depending on the content of inorganic filler used in the composition.
The rubber composition in accordance with the invention can also comprise, in addition to the coupling agents, coupling activators, agents for covering the inorganic fillers or more generally processing aids capable, in a known way, by virtue of an improvement in the dispersion of the filler in the rubber matrix and of a lowering in the viscosity of the compositions, of improving their ease of processing in the raw state, these processing aids being, for example, hydrolysable silanes, such as alkylalkoxysilanes (in particular alkyltriethoxysilanes), polyols, polyethers (for example, polyethylene glycols), primary, secondary or tertiary amines (for example, trialkanolamines), hydroxylated or hydrolysable POSs, for example a,w-dihydroxypolyorganosiloxanes (in particular a,w-dihydroxypolydimethylsiloxanes), or fatty acids, such as, for example, stearic acid.
According to a specific embodiment of the invention, the silica can be used at contents ranging from 2 to 35 phr, preferably from 3 to 25 phr and in particular from 5 to 20 phr. According to this embodiment, preferably, the rubber composition comprises from 0 to less than 2 phr of a coupling agent, more preferably from 0 to less than 1 phr of a coupling agent; more preferably still, it does not comprise a coupling agent. In the case where the rubber composition does not comprise a coupling agent, the silica is not regarded as a reinforcing filler and the rubber composition preferably comprises a covering agent which is preferably a polyethylene glycol. This specific embodiment of the invention, in or not in its preferred forms, can be combined with any one of the embodiments of the invention.
The content of reinforcing filler is preferably within a range extending from 10 to 90 phr. Below 10 phr, the reinforcement of the rubber composition can be insufficient to contribute an appropriate level of cohesion or wear resistance of the rubber component of the tyre comprising this composition. Above 90 phr, there exists a risk of increasing the hysteresis of the rubber composition and thus a risk of heating the tread and the tyre. The content of total reinforcing filler is more preferably from 25 to 70 phr, more preferably still from 35 to 60 phr.
These contents of reinforcing filler, whether or not they are preferred, apply to any one of the embodiments of the invention.
The rubber composition can also comprise all or a portion of the usual additives customarily used in elastomer compositions, such as, for example, plasticizers, pigments, protective agents, such as antiozone waxes, chemical antiozonants or antioxidants, antifatigue agents, a crosslinking system, vulcanization accelerators or retardants, or vulcanization activators.
According to any one = - 13 -embodiment of the invention, the crosslinking system is preferably based on sulphur but it can also be based on sulphur donors, on peroxide, on bismaleimides or on their mixtures.
The rubber composition can be manufactured in appropriate mixers, using two successive phases of preparation well known to a person skilled in the art: a first phase of thermomechanical working or kneading ("non-productive" phase) at high temperature, up to a maximum temperature of between 130 C and 200 C, followed by a second phase of mechanical working ("productive" phase) down to a lower temperature, typically below 110 C, for example between 40 C
and 100 C, during which finishing phase the crosslinking system is incorporated.
The process for preparing the tyre in accordance with the invention comprises, for example, the following stages:
- adding, during a first "non-productive" stage, to the first diene elastomer, the thermoplastic styrene elastomer and the reinforcing filler, by kneading thermomechanically until a maximum temperature of between 130 C and 200 C is reached, - cooling the combined mixture to a temperature of less than 70 C, - subsequently incorporating the crosslinking system, - kneading everything up to a maximum temperature of less than 90 C in order to obtain a mixture, - then calendering or extruding the mixture obtained in order to form a tread.
Whatever the embodiment of the invention, the tyre for vehicles intended to bear heavy loads in accordance with the invention is preferably an off-road tyre, tyre for vehicles running over non-bituminous ground surfaces, such as civil engineering vehicles, worksite heavy-duty vehicles or agricultural vehicles. The tyre is preferably a tyre for a civil engineering vehicle, whatever the embodiment of the invention.
The invention relates to the tyres described above, both in the raw state (that is to say, before curing) and in the cured state (that is to say, after crosslinking or vulcanization).
The abovementioned characteristics of the present invention, and also others, will be better understood on reading the following description of several implementational examples of the invention, given by way of illustration and without limitation.
III. IMPLEMENTATIONAL EXAMPLES OF THE INVENTION
The formulation of compositions Ti, A and B is described in Table I and that of compositions 12 and C is described in Table II.
Compositions A to C are in accordance with the invention in that the elastomer matrix comprises a polybutadiene or a butadiene copolymer and at most 50% by weight of a thermoplastic styrene =
elastomer in accordance with the invention and in that the reinforcing filler comprises more than 50% by weight of a carbon black. A and B differ from one another in the nature of the thermoplastic styrene elastomer. C differs from A and B in that it comprises an SBR instead of a BR
as a first diene elastomer.
Composition Ti, devoid of thermoplastic styrene elastomer, is the control composition for compositions A and B; composition T2, devoid of thermoplastic styrene elastomer, is the control composition for C.
Compositions Ti, T2, A, B and C are prepared in accordance with the process described above.
The compositions thus obtained are subsequently calendered, either in the form of plaques (with a thickness ranging from 2 to 3 mm) or thin sheets of rubber, for the measurement of their physical or mechanical properties, or in the form of profiled elements which can be used directly, after cutting and/or assembling to the desired dimensions, as tyre tread.
The results are recorded in Table III for A and B and the control Ti and in Table IV for C and the control T2.
The results which appear in Tables III and IV show a very strong improvement in the resistance to crack propagation for A, B and C, in comparison with their respective controls. The improvement is outstanding when the first diene elastomer is a polybutadiene and even more outstanding when the thermoplastic styrene elastomer is an SBIS.
The invention makes it possible to significantly improve the lifetime of tyres bearing heavy loads, in particular moving off-road, such as tyres equipping heavy-duty vehicles, in particular agricultural vehicles, civil engineering vehicles and worksite heavy-duty vehicles, since these tyres become much less sensitive to crack propagation at their treads.
Table I
Ti A
BR (1) 100 70 70 SBS (2) 30 SBIS (3) 30 Silica (4) 15 15 15 Carbon black (5) 40 40 40 Antioxidant 2.5 2.5 2.5 Paraffin 1 1 1 PEG (6) 2.5 2.5 2.5 Stearic acid 1 1 1 ZnO 2.7 2.7 2.7 CBS (7) 1 1 1 Sulphur 1.7 1.7 1.7 (1) BR comprising 4.3% of 1,2-; 2.7% of trans-1,4-; 93% of cis-1,4- (Tg -106 C) (2) SBS, D1101, sold by Kraton
Thus, a first subject-matter of the invention is a tyre for vehicles which are intended to bear heavy loads, the tread of which comprises a composition based on at least:
- an elastomer matrix comprising a first diene elastomer and a thermoplastic styrene elastomer, o which thermoplastic styrene elastomer represents at most 50% by weight of the elastomer matrix and comprises at least one rigid styrene segment and at least one flexible diene segment, which at least one flexible diene segment comprises at least 20%
by weight of conjugated diene units, it being possible for the conjugated diene units to be all or in part hydrogenated, o which first diene elastomer represents at least 50% by weight of the elastomer matrix and is chosen from the group consisting of polybutadienes, butadiene copolymers and their mixtures, - a reinforcing filler which comprises a carbon black which represents more than 50% by weight of the reinforcing filler, - a crosslinking system.
Another subject-matter of the invention is a process for preparing the tyre in accordance with the invention.
I. MEASUREMENTS AND TESTS USED
Resistance to crack propagation:
The rate of cracking was measured on test specimens of rubber compositions using a cyclic fatigue device (Elastomer Test System) of the 381 type from MTS, as explained below.
The resistance to cracking is measured using repeated tensile actions on a test specimen initially accommodated (after a first tensile cycle) and then notched. The tensile test specimen is composed of a rubber plaque of parallelepipedal shape, for example with a thickness of between 1 and 2 mm, with a length between 130 and 170 mm and with a width between 10 and 15 mm, the two side edges each being covered in the direction of the length with a cylindrical rubber strip (diameter 5 mm) making possible anchoring in the jaws of the tensile testing device. The test specimens thus prepared are tested in the fresh state. The test was carried out in air, at a temperature of 20 C.
After accommodation, 3 very fine notches with a length of between 15 and 20 mm are produced using a razor blade, at mid-width and aligned in the direction of the length of the test specimen, . - 3 -one at each end and one at the centre of the latter, before starting the test.
At each tensile cycle, the degree of deformation of the test specimen is automatically adjusted so as to keep the energy restitution level (amount of energy released during the progression of the crack) constant at a value of less than or equal to approximately 500 J/m2. The crack propagation rate is measured in nanometres per cycle. The resistance to crack propagation will be expressed in relative units (r.u.) by dividing the propagation rate of the control by that of the mixture, the rates being measured at the same energy restitution level. A value greater than that of the control, arbitrarily set at 100, indicates an improved result, that is to say a greater resistance to crack propagation.
II- DETAILED DESCRIPTION OF THE INVENTION
In the present description, unless expressly indicated otherwise, all the percentages (%) shown are % by weight. The abbreviation "phr" means parts by weight per hundred parts of elastomers present in the elastomer matrix, the elastomer matrix denoting all of the elastomers present in the rubber composition.
Furthermore, any interval of values denoted by the expression "between a and b" represents the range of values greater than "a" and lower than "b" (that is to say, limits a and b excluded), whereas any interval of values denoted by the expression "from a to b" means the range of values extending from "a" up to "b" (that is to say, including the strict limits a and b).
The expression "composition based on" should be understood as meaning, in the present description, a composition comprising the mixture and/or the in situ reaction product of the various constituents used, some of these base constituents (for example the elastomer, the filler or other additive conventionally used in a rubber composition intended for the manufacture of tyres) being capable of reacting or intended to react with one another, at least in part, during the various phases of manufacture of the composition intended for the manufacture of tyres.
The elastomer matrix of the rubber composition has the essential characteristic of comprising a first diene elastomer chosen from the group consisting of polybutadienes (BRs), butadiene copolymers and their mixtures.
Suitable in particular as polybutadienes are those having a content of 1,2-units of between 4% and 80% by weight of the weight of the polybutadiene or those having a content of cis-1,4- bonds of at least 90% by weight of the weight of the polybutadiene.
Suitable in particular as butadiene copolymers are the copolymers of butadiene and styrene (SBR).
The copolymers can be prepared in emulsion (ESBR) or in solution (SSBR).
Mention may be made of butadiene/styrene copolymers and in particular of those having a glass transition temperature Tg, = - 4 -measured according to ASTM D3418, of between 0 C and -90 C and more particularly between -C and -80 C, a styrene content of between 5% and 60% by weight and more particularly between 5% and 40%, a content (mol%) of 1,2- bonds of the butadiene part of between 4% and 75% of the butadiene part and a content (mol%) of trans-1,4- bonds of between 10% and 80% of 5 the butadiene part.
The first diene elastomer, whether it is a polybutadiene or a butadiene copolymer, can be modified by a modifying agent, such as, for example, a coupling, star-branching or functionalizing agent.
Mention may be made, as modifying agent, of compounds comprising a C-Sn bond or those 10 comprising an amine, silanol or alkoxysilane functional group. Such elastomers are, for example, described in Patents EP 0 778 311 B1, EP 0 890 607 B1, EP 0 692 492 B1, EP 1 000 970 B1 and EP 1 457 501 B1 or Patent Applications WO 2009/000750 and WO 2009/133068.
According to a preferred embodiment of the invention, the first diene elastomer is a polybutadiene, preferably exhibiting a content of cis-1,4- bonds of greater than or equal to 90% by weight of the weight of polybutadiene. This preferred embodiment of the invention can be combined with any one of the embodiments of the invention.
The first diene elastomer represents at least 50% by weight of the elastomer matrix. According to this embodiment, suitable as elastomer matrix is, for example, a mixture consisting of 40% by weight of the thermoplastic styrene elastomer, of 55% by weight of the first diene elastomer and of 5% by weight of a second diene elastomer, the percentages being calculated on the basis of the total weight of the elastomer matrix.
Second diene elastomer (or without distinction rubber) should be understood, in a known way, as meaning an (or several) elastomer composed, at least in part (i.e., a homopolymer or a copolymer), of diene monomer units (monomers bearing two conjugated or non-conjugated carbon-carbon double bonds), the second diene elastomer being different from the first diene elastomer and not being a thermoplastic styrene elastomer.
According to a preferred embodiment of the invention, only the first diene elastomer and the thermoplastic styrene elastomer constitute the elastomer matrix, which means that the elastomer matrix does not contain other elastomers than the first diene elastomer and the thermoplastic styrene elastomer.
The thermoplastic styrene elastomer comprises at least one rigid styrene segment and at least one flexible diene segment comprising at least 20% by weight of conjugated diene units, it being possible for the conjugated diene units to be all or in part hydrogenated. The rigid and flexible segments can be positioned linearly, or in a star or branched configuration.
A flexible segment refers to a polymer block of elastomer type and a rigid segment refers to a polymer block of thermoplastic type.
According to one embodiment of the invention, the thermoplastic styrene elastomer is a diblock.
The diblock comprises just one rigid styrene segment connected to just one flexible diene segment.
According to a preferred embodiment of the invention, the thermoplastic styrene elastomer comprises at least two rigid styrene segments. According to this preferred embodiment of the invention, generally at least two ends of chains of the thermoplastic styrene elastomer are each provided with a rigid styrene segment and the rigid styrene segments are connected via the flexible diene segment or segments. According to this preferred embodiment of the invention, the thermoplastic styrene elastomer is preferably a triblock. The triblock is then composed of two rigid styrene segments and of one flexible diene segment.
In the case where the thermoplastic styrene elastomer is a diblock, the designation of "the at least one rigid segment" denotes the rigid segment present in the thermoplastic styrene elastomer. In the cases other than a diblock, for example in the case of a triblock, the designation of "the at least one rigid segment" denotes the rigid segments present in the thermoplastic styrene elastomer.
In the case where the thermoplastic styrene elastomer is a diblock or a triblock, the designation of "the at least one flexible segment" denotes the flexible segment present in the thermoplastic styrene elastomer. In the case where the thermoplastic styrene elastomer is neither a diblock nor a triblock, the designation of "the at least one flexible segment" denotes the flexible segments present in the thermoplastic styrene elastomer.
The at least one rigid styrene segment is the homopolymer of a styrene monomer or the block or random copolymer of several styrene monomers or also the copolymer of one or more styrene monomers and of another non-styrene monomer, such as a 1,3-diene.
Styrene monomer should be understood, in the present description, as meaning styrene or a substituted styrene. Mention may be made, among substituted styrenes, for example, of methylstyrenes (for example, o-methylstyrene, m-methylstyrene or p-methylstyrene, a-methylstyrene, a,2-dinnethylstyrene, a,4-dimethylstyrene or diphenylethylene), para-(tert-butyl)styrene, chlorostyrenes (for example, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene or 2,4,6-trichlorostyrene), bromostyrenes (for example, o-bromostyrene, m-bromostyrene, p-bromostyrene, 2,4-dibromostyrene, 2,6-dibromostyrene or 2,4,6-tribromostyrene), fluorostyrenes (for example, o-fluorostyrene, m-fluorostyrene, p-fluorostyrene, 2,4-difluorostyrene, 2,6-difluorostyrene or 2,4,6-trifluorostyrene) or also para-hydroxystyrene.
According to a preferred embodiment of the invention, the at least one rigid styrene segment exhibits a glass transition temperature of greater than 80 C. Preferably, the at least one rigid styrene segment is a polystyrene.
The at least one flexible diene segment comprises at least 20% by weight of conjugated diene monomer units (also known as conjugated diene units). The at least one flexible diene segment can be the homopolymer of a conjugated diene or the block or random copolymer of several conjugated dienes or also the copolymer of one or more conjugated dienes and of at least one other non-diene monomer, such as a styrene monomer.
The content of conjugated diene units which form the flexible diene segment is preferably at least 50%, more preferably at least 60% and more preferably still at least 70% by weight of the weight of the flexible diene segment. Advantageously, it is at least 80% by weight of the weight of the flexible diene segment. These contents, whether or not they are preferred, apply to any one of the embodiments of the invention.
Suitable in particular as conjugated diene units are 1,3-butadiene units and isoprene units. The at least one flexible diene segment can be a polybutadiene, a polyisoprene or a copolymer of 1,3-butadiene and of isoprene. The copolymer of 1,3-butadiene and of isoprene can be block or random in nature.
Suitable as thermoplastic styrene elastomer are diblock copolymers, such as styrene/butadiene (SB), styrene/isoprene (SI) or styrene/butadiene/isoprene (SBI) block copolymers, or the mixture of these copolymers. In this designation, the flexible diene block is a random or block copolymer.
Suitable in particular as thermoplastic styrene elastomer are copolymers, such as styrene/butadiene/styrene (SBS), styrene/isoprene/styrene (SIS) or styrene/butadiene/isoprene/styrene (SBIS) block copolymers, or the mixture of these copolymers.
In this designation, the flexible diene block is a random or block copolymer.
Very particularly suitable is a styrene/butadiene/isoprene/styrene (SBIS) block copolymer.
According to a first alternative form of the invention, a fraction of the conjugated diene units of the at least one flexible diene segment is hydrogenated. A person skilled in the art will understand that he can equivalently use a thermoplastic styrene elastomer, the double bonds of a fraction of the conjugated diene units of the flexible diene segment of which will have been reduced to a single bond by a process other than a hydrogenation. Mention may be made, among the processes which make it possible to reduce the double bonds of the diene units to a single bond, of reductions with an aluminium hydride or with diimine, for example.
According to a second alternative form of the invention, all of the conjugated diene units of the at least one flexible diene segment are hydrogenated. A person skilled in the art will understand that he can equivalently use a thermoplastic styrene elastomer, the double bonds of all of the conjugated diene units of the flexible diene segment of which will have been reduced to a single bond by a process other than a hydrogenation.
According to this second alternative form of the invention, suitable as thermoplastic elastomer are styrene/ethylene/butylene (SEB), styrene/ethylene/propylene (SEP) or styrene/ethylene/ethylene/propylene (SEEP) block copolymers or the mixtures of these copolymers. In this designation, the hydrogenated flexible diene block is a random or block copolymer.
According to this second alternative form of the invention, also suitable as thermoplastic elastomer are styrene/ethylene/butylene/styrene (SEBS), styrene/ethylene/propylene/styrene (SEPS) or styrene/ethylene/ethylene/propylene/styrene (SEEPS) block copolymers or the mixtures of these copolymers. In this designation, the hydrogenated flexible diene block is a random or block copolymer.
Any one of the embodiments of the invention applies to the first alternative form of the invention or to the second alternative form of the invention.
Also suitable as thermoplastic styrene elastomer are the mixtures of an abovementioned triblock copolymer and of an abovementioned diblock copolymer. This is because the triblock copolymer can comprise a minor fraction by weight of diblock copolymer consisting of a rigid styrene segment and of a flexible diene segment, the rigid block and the flexible block being respectively of the same chemical nature, in particular of the same microstructure, as the rigid and flexible blocks of the triblock. The presence of the diblock copolymer in the triblock copolymer generally results from the process of synthesis of the triblock copolymer, which can result in the formation of byproduct, such as the diblock copolymer. Generally, the percentage of diblock copolymer in the triblock copolymer does not exceed 40% by weight of triblock copolymer.
According to a preferred embodiment of the invention, the content by weight of the at least one rigid styrene segment is between 5 and 40% of the weight of the thermoplastic styrene elastomer.
Below the minimum indicated, there is a risk of the thermoplastic nature of the thermoplastic styrene elastomer being substantially reduced while, above the recommended maximum, the elasticity of the composition can be affected. For these reasons, the content by weight of the at least one rigid styrene segment in the thermoplastic styrene elastomer is preferably within a range extending from 10 to 35%, more preferably from 10 to 20%, of the weight of the thermoplastic styrene elastomer. These contents, whether or not they are preferred, apply to any one of the embodiments of the invention, very particularly when the polystyrene forms the at least one rigid styrene segment of the thermoplastic styrene elastomer.
The number-average molar mass (denoted Mn) of the thermoplastic styrene elastomer is preferably between 50 000 and 500 000 g/mol, more preferably between 60 000 and 450 000 g/mol and more preferably still between 80 000 and 300 000 g/mol.
Advantageously, it is between 100 000 and 200 000 g/mol. These preferred ranges of number-average molar mass values apply whatever the embodiment of the invention.
The molar mass is determined, in a known way, by size exclusion chromatography (SEC). The sample is dissolved beforehand in tetrahydrofuran at a concentration of approximately 1 g/I and then the solution is filtered through a filter with a porosity of 0.45 p.m before injection. The apparatus used is a Waters Alliance chromatographic line. The elution solvent is tetrahydrofuran, the flow rate is 0.7 ml/min, the temperature of the system is 35 C and the analytical time is 90 min.
A set of four Waters columns in series, with the Styragel tradenames (HMW7, HMW6E and two HT6E), is used. The injected volume of the solution of the polymer sample is 100 pl. The detector is a Waters 2410 differential refractometer and its associated software, for making use of the chromatographic data, is the Waters Millennium system. The calculated number-average molar masses are relative to a calibration curve produced with polystyrene standards.
The thermoplastic styrene elastomer is present in a proportion by weight of at most 50% of the weight of the elastomer matrix of the rubber composition of the tread. Above the maximum value indicated, there is no longer a benefit with regard to the resistance to crack propagation of the rubber composition forming the tread of a tyre intended to bear heavy loads.
The content of thermoplastic styrene elastomer varies within a range extending preferably from 5 to 50%, more preferably from 10 to 45% and more preferably still from 20 to 45% by weight of the weight of the elastomer matrix. Advantageously, it varies from 25 to 45% by weight of the weight of the elastomer matrix. When the thermoplastic styrene elastomer is a mixture of unsaturated thermoplastic styrene elastomers in accordance with the invention, the contents shown apply to the mixture and not to each of the thermoplastic styrene elastomers. These contents, whether or not they are preferred, apply to any one of the embodiments of the invention.
According to a specific embodiment of the invention, the thermoplastic styrene elastomer exhibits a glass transition temperature of less than -20 C. This glass transition temperature is generally attributed to the glass temperature of the flexible diene segment of the thermoplastic styrene elastomer. The glass transition temperature is measured by means of a differential calorimeter (differential scanning calorimeter) according to Standard ASTM D3418 (1999).
According to this specific embodiment of the invention, the thermoplastic styrene elastomer exhibits a Tg preferably of less than -30 C, more preferably of less than -40 C and more preferably still of less than -50 C.
The reinforcing filler can be any type of "reinforcing" filler known for its abilities to reinforce a rubber composition which can be used for the manufacture of tyres, for example an organic filler, such as carbon black, a reinforcing inorganic filler, such as silica, with which is combined, in a known way, a coupling agent, or also a mixture of these two types of fillers.
A reinforcing filler typically consists of nanoparticles, the (weight-)average size of which is less than a micrometre, generally less than 500 nm, generally between 20 and 200 nm, in particular and more preferably between 20 and 150 nm.
According to the present invention, the reinforcing filler comprises a carbon black which represents more than 50% by weight of the reinforcing filler. Carbon black is understood to mean one or more carbon blacks. The carbon black is then regarded as the predominant reinforcing filler.
The carbon black exhibits a BET specific surface preferably of at least 90 m2/g, more preferably of at least 100 m2/g. The blacks conventionally used in tyres or their treads ("tyre-grade" blacks) are suitable as such. Mention will more particularly be made, among the latter, of the reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grade), such as, for example, the N115, N134, N234 or N375 blacks. The carbon blacks can be used in the isolated state, as available commercially, or in any other form, for example as support for some of the rubber additives used.
The carbon blacks might, for example, be already incorporated in an isoprene elastomer in the form of a masterbatch (see, for example, Application WO 97/36724 or WO
99/16600). The BET
specific surface of the carbon blacks is measured according to Standard D6556-10 [multipoint (at a minimum 5 points) method ¨ gas: nitrogen ¨ relative pressure p/po range: 0.1 to 0.3].
According to one embodiment of the invention, the reinforcing filler also comprises a reinforcing inorganic filler. The term "reinforcing inorganic filler" should be understood here as meaning any inorganic or mineral filler, whatever its colour and its origin (natural or synthetic), also known as "white filler", "clear filler" or even "non-black filler", in contrast to carbon black, capable of reinforcing, by itself alone, without means other than an intermediate coupling agent, a rubber composition intended for the manufacture of pneumatic tyres, in other words capable of replacing, in its reinforcing role, a conventional tyre-grade carbon black; such a filler is generally characterized, in a known way, by the presence of hydroxyl (¨OH) groups at its surface.
Mineral fillers of the siliceous type, preferably silica (S102), are suitable in particular as reinforcing inorganic fillers. The silica used can be any reinforcing silica known to a person skilled in the art, in particular any precipitated or fumed silica exhibiting a BET specific surface and a CTAB specific surface both of less than 450 m2/g, preferably from 30 to 400 m2/g, in particular between 60 and 300 m2/g. Mention may be made, as example of silica of use for the requirements of the invention, of the Ultrasil VN3 silica sold by Evonik. Mention will be made, as highly dispersible precipitated silicas ("HDSs"), for example, of the Ultrasil 7000 and Ultrasil 7005 silicas from Degussa, the Zeosil 1165MP, 1135MP and 1115MP silicas from Rhodia, the Hi-Sil EZ150G silica from PPG, the Zeopol 8715, 8745 and 8755 silicas from Huber or the silicas having a high specific surface as described in Application WO 03/016387.
The physical state under which the reinforcing inorganic filler is provided is not important, whether it is in the form of a powder, microbeads, granules or also beads. Of course, reinforcing inorganic filler is also understood to mean mixtures of different reinforcing inorganic fillers, in particular of highly dispersible silicas as described above.
A person skilled in the art will understand that use might be made, as filler equivalent to the reinforcing inorganic filler described in the present section, of a reinforcing filler of another nature, in particular organic nature, such as carbon black, provided that this reinforcing filler is covered with an inorganic layer, such as silica, or else comprises, at its surface, functional sites, in particular hydroxyl sites, requiring the use of a coupling agent in order to establish the bond between the filler and the elastomer. Mention may be made, by way of example, for example, of carbon blacks for tyres, such as described, for example, in patent documents WO 96/37547 and WO 99/28380.
In the present account, as regards the silica, the BET specific surface is determined in a known way by gas adsorption using the Brunauer-Emmett-Teller method described in The Journal of the American Chemical Society, Vol. 60, page 309, February 1938, more specifically according to French Standard NF ISO 9277 of December 1996 (multipoint (5 point) volumetric method -gas: nitrogen -degassing: 1 hour at 160 C - relative pressure p/po range: 0.05 to 0.17). The CTAB specific surface is the external surface determined according to French Standard NF T 45-007 of November 1987 (method B).
In order to couple the reinforcing inorganic filler to the diene elastomer, use is made, in a well-known way, of an at least bifunctional coupling agent, in particular a silane, (or bonding agent) intended to provide a satisfactory connection, of chemical and/or physical nature, between the inorganic filler (surface of its particles) and the diene elastomer. Use is made in particular of at least bifunctional organosilanes or polyorganosiloxa nes.
Use is made in particular of silane polysulphides, referred to as "symmetrical" or "unsymmetrical"
depending on their specific structure, such as described, for example, in Applications WO
03/002648 (or US 2005/016651) and WO 03/002649 (or US 2005/016650).
Particularly suitable, without the definition below being limiting, are silane polysulphides corresponding to the general formula (V):
Z - A - Sx - A - Z (V) in which:
- x is an integer from 2 to 8 (preferably from 2 to 5);
- the A symbols, which are identical or different, represent a divalent hydrocarbon radical (preferably a C1-C18 alkylene group or a C6-C12 arylene group, more particularly a C1-C10, in particular Ci-C4, alkylene, especially propylene);
- the Z symbols, which are identical or different, correspond to one of the three formulae below:
=
¨ = Si¨R1 ¨Si¨R2 ¨Si¨R2 , in which:
- the R2 radicals, which are substituted or unsubstituted and identical to or different from one another, represent a C1-C18 alkyl, C5-C18 cycloalkyl or C6-C18 aryl group (preferably C1-C6 alkyl, cyclohexyl or phenyl groups, in particular C1-C4 alkyl groups, more particularly methyl and/or ethyl);
- the R2 radicals, which are substituted or unsubstituted and identical to or different from one another, represent a C1-C18 alkoxyl or C5-C18 cycloalkoxyl group (preferably a group chosen from Ci-C8 alkoxyls and C5-C8 cycloalkoxyls, more preferably still a group chosen from C1-C4alkoxyls, in particular methoxyl and ethoxyl).
In the case of a mixture of alkoxysilane polysulphides corresponding to the above formula (I), in particular normal commercially available mixtures, the mean value of the "x"
indices is a fractional number preferably of between 2 and 5, more preferably of approximately 4.
However, the invention can also advantageously be carried out, for example, with alkoxysilane disulphides (x =
2).
Mention will more particularly be made, as examples of silane polysulphides, of bis((C1-C4)alkoxyl(C1-C4)alkylsilyl(C1-C4)alkyl) polysulphides (in particular disulphides, trisulphides or tetrasulphides), such as, for example, bis(3-trimethoxysilylpropyl) or bis(3-triethoxysilylpropyl) polysulphides. Use is made in particular, among these compounds, of bis(3-triethoxysilylpropyl) tetrasulphide, abbreviated to TESPT, of formula ((C2H50)3Si(CH2)3S2h, or bis(3-triethoxysilylpropyl) disulphide, abbreviated to TESPD, of formula [(C2H50)3Si(CH2)3Sk.
Mention will in particular be made, as coupling agent other than alkoxysilane polysulphide, of bifunctional POSs (polyorganosiloxanes), or else of hydroxysilane polysulphides, such as described in Patent Applications WO 02/30939 (or US 6 774 255) and WO 02/31041 (or US
2004/051210), or else of silanes or POSs bearing azodicarbonyl functional groups, such as described, for example, in Patent Applications WO 2006/125532, WO 2006/125533 and WO 2006/125534.
= - 12 -The content of coupling agent is advantageously less than 20 phr, it being understood that it is generally desirable to use as little as possible of it. Typically, the content of coupling agent represents from 0.5% to 15% by weight, with respect to the amount of inorganic filler. Its content is preferably between 0.5 and 12 phr, more preferably within a range extending from 3 to 10 phr.
This content is easily adjusted by a person skilled in the art depending on the content of inorganic filler used in the composition.
The rubber composition in accordance with the invention can also comprise, in addition to the coupling agents, coupling activators, agents for covering the inorganic fillers or more generally processing aids capable, in a known way, by virtue of an improvement in the dispersion of the filler in the rubber matrix and of a lowering in the viscosity of the compositions, of improving their ease of processing in the raw state, these processing aids being, for example, hydrolysable silanes, such as alkylalkoxysilanes (in particular alkyltriethoxysilanes), polyols, polyethers (for example, polyethylene glycols), primary, secondary or tertiary amines (for example, trialkanolamines), hydroxylated or hydrolysable POSs, for example a,w-dihydroxypolyorganosiloxanes (in particular a,w-dihydroxypolydimethylsiloxanes), or fatty acids, such as, for example, stearic acid.
According to a specific embodiment of the invention, the silica can be used at contents ranging from 2 to 35 phr, preferably from 3 to 25 phr and in particular from 5 to 20 phr. According to this embodiment, preferably, the rubber composition comprises from 0 to less than 2 phr of a coupling agent, more preferably from 0 to less than 1 phr of a coupling agent; more preferably still, it does not comprise a coupling agent. In the case where the rubber composition does not comprise a coupling agent, the silica is not regarded as a reinforcing filler and the rubber composition preferably comprises a covering agent which is preferably a polyethylene glycol. This specific embodiment of the invention, in or not in its preferred forms, can be combined with any one of the embodiments of the invention.
The content of reinforcing filler is preferably within a range extending from 10 to 90 phr. Below 10 phr, the reinforcement of the rubber composition can be insufficient to contribute an appropriate level of cohesion or wear resistance of the rubber component of the tyre comprising this composition. Above 90 phr, there exists a risk of increasing the hysteresis of the rubber composition and thus a risk of heating the tread and the tyre. The content of total reinforcing filler is more preferably from 25 to 70 phr, more preferably still from 35 to 60 phr.
These contents of reinforcing filler, whether or not they are preferred, apply to any one of the embodiments of the invention.
The rubber composition can also comprise all or a portion of the usual additives customarily used in elastomer compositions, such as, for example, plasticizers, pigments, protective agents, such as antiozone waxes, chemical antiozonants or antioxidants, antifatigue agents, a crosslinking system, vulcanization accelerators or retardants, or vulcanization activators.
According to any one = - 13 -embodiment of the invention, the crosslinking system is preferably based on sulphur but it can also be based on sulphur donors, on peroxide, on bismaleimides or on their mixtures.
The rubber composition can be manufactured in appropriate mixers, using two successive phases of preparation well known to a person skilled in the art: a first phase of thermomechanical working or kneading ("non-productive" phase) at high temperature, up to a maximum temperature of between 130 C and 200 C, followed by a second phase of mechanical working ("productive" phase) down to a lower temperature, typically below 110 C, for example between 40 C
and 100 C, during which finishing phase the crosslinking system is incorporated.
The process for preparing the tyre in accordance with the invention comprises, for example, the following stages:
- adding, during a first "non-productive" stage, to the first diene elastomer, the thermoplastic styrene elastomer and the reinforcing filler, by kneading thermomechanically until a maximum temperature of between 130 C and 200 C is reached, - cooling the combined mixture to a temperature of less than 70 C, - subsequently incorporating the crosslinking system, - kneading everything up to a maximum temperature of less than 90 C in order to obtain a mixture, - then calendering or extruding the mixture obtained in order to form a tread.
Whatever the embodiment of the invention, the tyre for vehicles intended to bear heavy loads in accordance with the invention is preferably an off-road tyre, tyre for vehicles running over non-bituminous ground surfaces, such as civil engineering vehicles, worksite heavy-duty vehicles or agricultural vehicles. The tyre is preferably a tyre for a civil engineering vehicle, whatever the embodiment of the invention.
The invention relates to the tyres described above, both in the raw state (that is to say, before curing) and in the cured state (that is to say, after crosslinking or vulcanization).
The abovementioned characteristics of the present invention, and also others, will be better understood on reading the following description of several implementational examples of the invention, given by way of illustration and without limitation.
III. IMPLEMENTATIONAL EXAMPLES OF THE INVENTION
The formulation of compositions Ti, A and B is described in Table I and that of compositions 12 and C is described in Table II.
Compositions A to C are in accordance with the invention in that the elastomer matrix comprises a polybutadiene or a butadiene copolymer and at most 50% by weight of a thermoplastic styrene =
elastomer in accordance with the invention and in that the reinforcing filler comprises more than 50% by weight of a carbon black. A and B differ from one another in the nature of the thermoplastic styrene elastomer. C differs from A and B in that it comprises an SBR instead of a BR
as a first diene elastomer.
Composition Ti, devoid of thermoplastic styrene elastomer, is the control composition for compositions A and B; composition T2, devoid of thermoplastic styrene elastomer, is the control composition for C.
Compositions Ti, T2, A, B and C are prepared in accordance with the process described above.
The compositions thus obtained are subsequently calendered, either in the form of plaques (with a thickness ranging from 2 to 3 mm) or thin sheets of rubber, for the measurement of their physical or mechanical properties, or in the form of profiled elements which can be used directly, after cutting and/or assembling to the desired dimensions, as tyre tread.
The results are recorded in Table III for A and B and the control Ti and in Table IV for C and the control T2.
The results which appear in Tables III and IV show a very strong improvement in the resistance to crack propagation for A, B and C, in comparison with their respective controls. The improvement is outstanding when the first diene elastomer is a polybutadiene and even more outstanding when the thermoplastic styrene elastomer is an SBIS.
The invention makes it possible to significantly improve the lifetime of tyres bearing heavy loads, in particular moving off-road, such as tyres equipping heavy-duty vehicles, in particular agricultural vehicles, civil engineering vehicles and worksite heavy-duty vehicles, since these tyres become much less sensitive to crack propagation at their treads.
Table I
Ti A
BR (1) 100 70 70 SBS (2) 30 SBIS (3) 30 Silica (4) 15 15 15 Carbon black (5) 40 40 40 Antioxidant 2.5 2.5 2.5 Paraffin 1 1 1 PEG (6) 2.5 2.5 2.5 Stearic acid 1 1 1 ZnO 2.7 2.7 2.7 CBS (7) 1 1 1 Sulphur 1.7 1.7 1.7 (1) BR comprising 4.3% of 1,2-; 2.7% of trans-1,4-; 93% of cis-1,4- (Tg -106 C) (2) SBS, D1101, sold by Kraton
(3) SBIS, D1170, sold by Kraton
(4) Ultrasil VN3, sold by Evonik
(5) N115
(6) polyethylene glycol with an Mn of 6000-20 000 g/mol, from Sasol Marl
(7) N-cyclohexy1-2-benzothiazolesulphenamide, Santocure CBS, sold by Flexsys , Table II
SBR (1) 100 70 SBS (2) 30 Silica (3) 15 15 Carbon black (7) 40 40 Antioxidant 2.5 2.5 Paraffin 1 1 PEG (8) 2.5 2.5 Stearic acid 1 1 ZnO 2.7 2.7 CBS (9) 1 1 Sulphur 1.7 1.7 (1) SBR with 25% of styrene (% by weight relative to the weight of SBR) and 40% of 1,2-butadiene units (% by weight of the butadiene part) (2) SBS, D1101, sold by Kraton (3) Ultrasil VN3, sold by Evonik (4) Zeosil 1165 MP, from Rhodia (HDS type) (5) TESPT, Si69, from Evonik (6) diphenylguanidine, Perkacit DPG, from Flexsys (7) N115
SBR (1) 100 70 SBS (2) 30 Silica (3) 15 15 Carbon black (7) 40 40 Antioxidant 2.5 2.5 Paraffin 1 1 PEG (8) 2.5 2.5 Stearic acid 1 1 ZnO 2.7 2.7 CBS (9) 1 1 Sulphur 1.7 1.7 (1) SBR with 25% of styrene (% by weight relative to the weight of SBR) and 40% of 1,2-butadiene units (% by weight of the butadiene part) (2) SBS, D1101, sold by Kraton (3) Ultrasil VN3, sold by Evonik (4) Zeosil 1165 MP, from Rhodia (HDS type) (5) TESPT, Si69, from Evonik (6) diphenylguanidine, Perkacit DPG, from Flexsys (7) N115
(8) polyethylene glycol with an Mn of 6000-20 000 g/mol, from Sasol Marl
(9) N-cyclohexy1-2-benzothiazolesulphenamide, Santocure CBS, sold by Flexsys Table III
Resistance to crack Ti A
propagation at 20 C 100 430 778 Table IV
Resistance to crack T2 propagation at 20 C 100 312
Resistance to crack Ti A
propagation at 20 C 100 430 778 Table IV
Resistance to crack T2 propagation at 20 C 100 312
Claims (26)
1. Tyre for vehicles which are intended to bear heavy loads, the tread of which comprises a composition based on at least:
- an elastomer matrix comprising a first diene elastomer and a thermoplastic styrene elastomer, .circle. which thermoplastic styrene elastomer represents at most 50% by weight of the elastomer matrix and comprises at least one rigid styrene segment and at least one flexible diene segment, which at least one flexible diene segment comprises at least 20%
by weight of conjugated diene units, it being possible for the conjugated diene units to be all or in part hydrogenated, .circle. which first diene elastomer represents at least 50% by weight of the elastomer matrix and is chosen from the group consisting of polybutadienes, butadiene copolymers and their mixtures, - a reinforcing filler which comprises a carbon black which represents more than 50% by weight of the reinforcing filler, - a crosslinking system.
- an elastomer matrix comprising a first diene elastomer and a thermoplastic styrene elastomer, .circle. which thermoplastic styrene elastomer represents at most 50% by weight of the elastomer matrix and comprises at least one rigid styrene segment and at least one flexible diene segment, which at least one flexible diene segment comprises at least 20%
by weight of conjugated diene units, it being possible for the conjugated diene units to be all or in part hydrogenated, .circle. which first diene elastomer represents at least 50% by weight of the elastomer matrix and is chosen from the group consisting of polybutadienes, butadiene copolymers and their mixtures, - a reinforcing filler which comprises a carbon black which represents more than 50% by weight of the reinforcing filler, - a crosslinking system.
2. Tyre according to Claim 1, wherein the elastomer matrix consists of a mixture of the first diene elastomer and of the thermoplastic styrene elastomer.
3. Tyre according to any one of Claims 1 to 2, wherein the content of thermoplastic styrene elastomer represents from 5 to 50% by weight, preferably from 10 to 45% by weight, more preferably from 20 to 45% by weight and more preferably still from 25 to 45%
by weight of the elastomer matrix.
by weight of the elastomer matrix.
4. Tyre according to any one of Claims 1 to 3, wherein the at least one rigid styrene segment exhibits a glass transition temperature of greater than 80°C.
5. Tyre according to any one of Claims 1 to 4, wherein the at least one rigid styrene segment is a polystyrene.
6. Tyre according to any one of Claims 1 to 5, wherein the conjugated diene units of the at least one flexible diene segment are 1,3-butadiene units or isoprene units.
7. Tyre according to any one of Claims 1 to 6, wherein the thermoplastic styrene elastomer is a diblock comprising just one rigid styrene segment connected to just one flexible diene segment.
8. Tyre according to Claim 7, wherein the thermoplastic styrene elastomer is a styrene/butadiene (SB), styrene/isoprene (SI) or styrene/butadiene/isoprene (SBI) block copolymer or the mixture of these copolymers.
9. Tyre according to any one of Claims 1 to 6, wherein the thermoplastic styrene elastomer comprises at least two rigid styrene segments.
10. Tyre according to Claim 9, wherein the thermoplastic styrene elastomer is a triblock composed of two rigid styrene segments and of one flexible diene segment.
11. Tyre according to Claim 10, wherein the thermoplastic styrene elastomer is a styrene/butadiene/styrene (SBS), styrene/isoprene/styrene (SIS) or styrene/butadiene/isoprene/styrene (SBIS) block copolymer or the mixture of these copolymers.
12. Tyre according to Claim 11, wherein the thermoplastic styrene elastomer is a styrene/butadiene/isoprene/styrene (SBIS) block copolymer.
13. Tyre according to any one of Claims 1 to 12, wherein a fraction of the conjugated diene units of the at least one flexible diene segment is hydrogenated.
14. Tyre according to any one of Claims 1 to 12, wherein all of the conjugated diene units of the at least one flexible diene segment are hydrogenated.
15. Tyre according to Claims 7 and 14, wherein the thermoplastic styrene elastomer is a styrene/ethylene/butylene (SEB), styrene/ethylene/propylene (SEP) or styrene/ethylene/ethylene/propylene (SEEP) block copolymer or their mixture.
16. Tyre according to Claims 10 and 14, wherein the thermoplastic styrene elastomer is a styrene/ethylene/butylene/styrene (SEBS), styrene/ethylene/propylene/styrene (SEPS) or styrene/ethylene/ethylene/propylene/styrene (SEEPS) block copolymer or their mixture.
17. Tyre according to any one of Claims 1 to 16, wherein the thermoplastic styrene elastomer exhibits a glass transition temperature of less than -20°C, preferably of less than -30°C.
18. Tyre according to Claim 17, wherein the thermoplastic styrene elastomer exhibits a glass transition temperature of less than -40°C, preferably of less than -50°C.
19. Tyre according to any one of Claims 1 to 18, wherein the carbon black exhibits a BET specific surface of at least 90 m2/g, preferably of at least 100 m2/g.
20. Tyre according to any one of Claims 1 to 19, wherein the composition comprises between 2 and 35 phr of a silica.
21. Tyre according to Claim 20, wherein the rubber composition comprises from 0 to less than 2 phr of a coupling agent, preferably from 0 to less than 1 phr of a coupling agent.
22. Tyre according to Claim 21, wherein the content of coupling agent is equal to 0 phr.
23. Tyre according to Claim 22, wherein the rubber composition comprises a covering agent, preferably a polyethylene glycol.
24. Tyre according to any one of Claims 1 to 23, wherein the tyre is an off-road tyre.
25. Tyre according to Claim 24, wherein the tyre is a tyre for a civil engineering vehicle.
26. Process for manufacturing the tyre according to any one of Claims 1 to 25, which comprises the following stages:
- adding, during a first "non-productive" stage, to the first diene elastomer, the thermoplastic styrene elastomer and the reinforcing filler, by kneading thermomechanically until a maximum temperature of between 130°C and 200°C is reached, - cooling the combined mixture to a temperature of less than 70°C, - subsequently incorporating the crosslinking system, - kneading everything up to a maximum temperature of less than 90°C
in order to obtain a mixture, - then calendering or extruding the mixture obtained in order to form a tread.
- adding, during a first "non-productive" stage, to the first diene elastomer, the thermoplastic styrene elastomer and the reinforcing filler, by kneading thermomechanically until a maximum temperature of between 130°C and 200°C is reached, - cooling the combined mixture to a temperature of less than 70°C, - subsequently incorporating the crosslinking system, - kneading everything up to a maximum temperature of less than 90°C
in order to obtain a mixture, - then calendering or extruding the mixture obtained in order to form a tread.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR1363147A FR3015499B1 (en) | 2013-12-20 | 2013-12-20 | PNEUMATIC FOR VEHICLES INTENDED TO WEAR HEAVY LOADS |
| FR1363147 | 2013-12-20 | ||
| PCT/EP2014/078696 WO2015091929A1 (en) | 2013-12-20 | 2014-12-19 | Tire for vehicle bearing heavy loads |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2933303A1 true CA2933303A1 (en) | 2015-06-25 |
Family
ID=50489252
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2933303A Abandoned CA2933303A1 (en) | 2013-12-20 | 2014-12-19 | Tire for vehicle bearing heavy loads |
Country Status (4)
| Country | Link |
|---|---|
| AU (1) | AU2014368468B2 (en) |
| CA (1) | CA2933303A1 (en) |
| FR (1) | FR3015499B1 (en) |
| WO (1) | WO2015091929A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10961374B2 (en) * | 2016-12-22 | 2021-03-30 | Compagnie Generale Des Etablissements Michelin | Rubber composition with a good dispersion of large amounts of reinforcing inorganic filler |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| MX2017013016A (en) * | 2015-04-24 | 2018-07-04 | Pirelli | High-performance tyre. |
| FR3037593A1 (en) * | 2015-06-18 | 2016-12-23 | Michelin & Cie | PNEUMATIC FOR VEHICLES INTENDED TO WEAR HEAVY LOADS |
| FR3045636B1 (en) * | 2015-12-22 | 2017-12-29 | Michelin & Cie | TIRE FOR VEHICLE CARRYING HEAVY LOADS COMPRISING A NEW BEARING BAND |
| FR3062083A1 (en) * | 2017-01-20 | 2018-07-27 | Compagnie Generale Des Etablissements Michelin | PNEUMATIC FLANK FOR HEAVY VEHICLE TYPE GENIE CIVIL |
Family Cites Families (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5204407A (en) * | 1990-06-11 | 1993-04-20 | Bridgestone Corporation | Pneumatic tires |
| FR2722505B1 (en) | 1994-07-15 | 1996-09-27 | Michelin & Cie | SILICA-FILLED ELASTOMERIC COMPOSITIONS FOR USE IN TIRE TIRES |
| ATE304576T1 (en) | 1995-05-22 | 2005-09-15 | Cabot Corp | RUBBER COMPOSITIONS CONTAINING SILICON-MODIFIED CARBON |
| FR2740778A1 (en) | 1995-11-07 | 1997-05-09 | Michelin & Cie | SILICA-BASED RUBBER COMPOSITION AND FUNCTIONALIZED DIENE POLYMER HAVING TERMINAL SILANOL FUNCTION |
| JP4234200B2 (en) | 1996-04-01 | 2009-03-04 | キャボット コーポレイション | Novel elastomer composite and method for producing the same |
| FR2765882B1 (en) | 1997-07-11 | 1999-09-03 | Michelin & Cie | CARBON BLACK-BASED RUBBER COMPOSITION HAVING SILICA ATTACHED TO ITS SURFACE AND ALCOXYSILANE FUNCTIONALIZED DIENE POLYMER |
| CN1285454C (en) | 1997-09-30 | 2006-11-22 | 卡伯特公司 | Elastomer composite blends and method for producing them |
| KR20010032540A (en) | 1997-11-28 | 2001-04-25 | 로버트 히에벨 | Rubber composition for tyres, reinforced with a carbon black coated with an aluminous layer |
| US6344518B1 (en) | 1998-11-10 | 2002-02-05 | Jsr Corporation | Conjugated diolefin copolymer rubber and rubber composition |
| ES2256317T3 (en) | 2000-10-13 | 2006-07-16 | Societe De Technologie Michelin | ORGANOSILANO POLIFUNCIONAL USABLE AS A COUPLING AGENT AND ITS OBTAINING PROCEDURE. |
| ATE330993T1 (en) | 2000-10-13 | 2006-07-15 | Michelin Soc Tech | RUBBER COMPOSITION WITH A POLYFUNCTIONAL ORGANOSILANE AS ADHESION PROMOTER |
| CN1547601B (en) | 2001-06-28 | 2012-09-05 | 米其林技术公司 | Tyre tread reinforced with silica having a low specific surface area |
| EP1404755A1 (en) | 2001-06-28 | 2004-04-07 | Société de Technologie Michelin | Tyre tread reinforced with silica having a very low specific surface area |
| DE60225300T2 (en) | 2001-08-13 | 2009-02-26 | Société de Technologie Michelin | VEHICLE COMPOSITION FOR TIRES WITH A SPECIAL SILICONE AS REINFORCING FILLER |
| EP1457501B1 (en) | 2001-09-27 | 2009-04-08 | JSR Corporation | Conjugated diolefin (co) polymer rubber, process for producing (co) polymer rubber, rubber composition, composite and tire |
| FR2886305B1 (en) | 2005-05-26 | 2007-08-10 | Michelin Soc Tech | PNEUMATIC RUBBER COMPOSITION COMPRISING AN ORGANOSILICALLY COUPLED AGENT AND AN INORGANIC CHARGE RECOVERY AGENT |
| FR2886304B1 (en) | 2005-05-26 | 2007-08-10 | Michelin Soc Tech | RUBBER COMPOSITION FOR PNEUMATIC COMPRISING AN ORGANOSILICIC COUPLING SYSTEM |
| FR2886306B1 (en) | 2005-05-26 | 2007-07-06 | Michelin Soc Tech | PNEUMATIC RUBBER COMPOSITION COMPRISING AN ORGANOSILOXANE COUPLING AGENT |
| FR2918064B1 (en) | 2007-06-28 | 2010-11-05 | Michelin Soc Tech | PROCESS FOR THE PREPARATION OF POLYETHER BLOCK DIENE COPOLYMER, REINFORCED RUBBER COMPOSITION AND PNEUMATIC WRAPPING. |
| FR2930554B1 (en) | 2008-04-29 | 2012-08-17 | Michelin Soc Tech | ELASTOMERIC MIXTURE COMPRISING MAJORITARILY AN AMINO-ALCOXYSILANE GROUP-COUPLED DIENE ELASTOMER, RUBBER COMPOSITION COMPRISING SAME AND METHODS OF OBTAINING SAME |
| FR2956119B1 (en) * | 2009-12-23 | 2012-12-28 | Michelin Soc Tech | PNEUMATIC HAVING THE TOP ZONE PROVIDED WITH A SUB-LAYER COMPRISING A THERMOPLASTIC ELASTOMER |
| FR2961818B1 (en) * | 2010-06-23 | 2012-07-20 | Michelin Soc Tech | RUBBER COMPOSITION COMPRISING A THERMOPLASTIC LOAD AND COMPATIBILIZING AGENT |
| FR2966384A1 (en) * | 2010-10-22 | 2012-04-27 | Michelin Soc Tech | PNEUMATIC COMPRISING A BUFFER ZONE BETWEEN THE CARCASE FRAME AND THE TOP FRAME |
-
2013
- 2013-12-20 FR FR1363147A patent/FR3015499B1/en not_active Expired - Fee Related
-
2014
- 2014-12-19 WO PCT/EP2014/078696 patent/WO2015091929A1/en active Application Filing
- 2014-12-19 CA CA2933303A patent/CA2933303A1/en not_active Abandoned
- 2014-12-19 AU AU2014368468A patent/AU2014368468B2/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10961374B2 (en) * | 2016-12-22 | 2021-03-30 | Compagnie Generale Des Etablissements Michelin | Rubber composition with a good dispersion of large amounts of reinforcing inorganic filler |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2015091929A1 (en) | 2015-06-25 |
| AU2014368468A1 (en) | 2016-06-30 |
| FR3015499A1 (en) | 2015-06-26 |
| AU2014368468B2 (en) | 2018-03-29 |
| FR3015499B1 (en) | 2017-04-28 |
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| EEER | Examination request |
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| FZDE | Discontinued |
Effective date: 20220412 |