Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/54—Silicon-containing compounds
  • C08K5/541—Silicon-containing compounds containing oxygen
  • C08K5/5415—Silicon-containing compounds containing oxygen containing at least one Si—O bond
  • C08K5/5419—Silicon-containing compounds containing oxygen containing at least one Si—O bond containing at least one Si—C bond
• • 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
• • 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
• • 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
  • B60C1/0025—Compositions of the sidewalls
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/54—Silicon-containing compounds
  • C08K5/544—Silicon-containing compounds containing nitrogen
  • C08K5/5465—Silicon-containing compounds containing nitrogen containing at least one C=N bond
• • 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
  • B60C15/00—Tyre beads, e.g. ply turn-up or overlap
  • B60C15/06—Flipper strips, fillers, or chafing strips and reinforcing layers for the construction of the bead
  • B60C2015/0614—Flipper strips, fillers, or chafing strips and reinforcing layers for the construction of the bead characterised by features of the chafer or clinch portion, i.e. the part of the bead contacting the rim
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
  • Y10T428/2991—Coated
  • Y10T428/2993—Silicic or refractory material containing [e.g., tungsten oxide, glass, cement, etc.]
  • Y10T428/2995—Silane, siloxane or silicone coating

Definitions

• the present invention relates to diene elastomer compositions reinforced with an inorganic filler, such as silica, intended for the manufacture of tyres or tyre semi-finished products, in particular for the treads of these tyres.
• an inorganic filler such as silica
• Such a coupling agent which is at least bifunctional, has as simplified general formula “Y-W-X”, in which:
• the coupling agents should in particular not be confused with simple covering agents for the inorganic filler which, in a known way, may comprise the Y functional group, active with regard to the inorganic filler, but are in all cases devoid of the X functional group, active with regard to the diene elastomer.
• Coupling agents in particular (silica/diene elastomer) coupling agents
• silane bifunctional sulphides in particular alkoxysilanes, regarded today as the products contributing, for vulcanisates comprising silica as filler, the best compromise in terms of scorch safety, of ease of processability and of reinforcing power.
• TESPT bis(3-triethoxysilylpropyl)tetrasulphide
• a first subject-matter of the invention is a rubber composition intended for the manufacture of tyres or of tyre semi-finished products, based on at least one isoprene elastomer, an inorganic filler as reinforcing filler and a polyfunctional organosiloxane coupling agent comprising per molecule, to provide the bonding between the reinforcing inorganic filler and the isoprene elastomer, grafted to its silicon atoms, on the one hand at least one hydroxyl or hydrolysable functional group allowing it to be grafted to the reinforcing inorganic filler and, on the other hand, at least one group bearing at least one functional group allowing it to be grafted to the isoprene elastomer, the said composition being characterized in that the said functional group is an azodicarbonyl group —CO—N ⁇ N—CO—.
• Another subject-matter of the invention is a process for preparing a rubber composition intended for the manufacture of tyres or of tyre semi-finished products exhibiting an improved hysteresis, this composition being based on an isoprene elastomer, on a reinforcing inorganic filler and on a polyfunctional organosiloxane coupling agent, the said process comprising the following stages:
• compositions according to the invention for the manufacture of tyres or of semi-finished products made of rubber intended for these tyres, these semi-finished products being chosen in particular from the group consisting of treads, crown reinforcement plies, side walls, carcass reinforcement plies, beads, protectors, underlayers, rubber blocks and other internal rubbers, in particular decoupling rubbers, intended to provide the bonding or the interface between the abovementioned regions of the tyres.
• Another subject-matter of the invention is these tyres and these semi-finished products themselves when they comprise a rubber composition in accordance with the invention.
• the invention relates in particular to tyre treads, it being possible for these treads to be used during the manufacture of new tyres or for the retreading of waste tyres; by virtue of the compositions of the invention, these treads exhibit both high wear resistance and reduced rolling resistance.
• composition in accordance with the invention is particularly suitable for the manufacture of tyres or of tyre treads intended for equipping passenger vehicles, vans, for 4 ⁇ 4 (4-wheel drive) vehicles, two-wheel vehicles, heavy-duty vehicles, that is to say underground, bus, heavy road transport vehicles (lorries, tractors, trailers) or off-road vehicles, aircraft, earthmoving equipment, heavy agricultural vehicles or handling vehicles.
• the rubber compositions are characterized, before and after curing, as indicated below.
• the measurements are carried out at 150° C. with an oscillating disc rheometer, according to Standard DIN 53529-part 3 (June 1983).
• the change in the rheometric torque as a function of time describes the change in the stiffening of the composition as a result of the vulcanization reaction.
• the measurements are processed according to Standard DIN 53529-part 2 (March 1983): Ti is the induction time, that is to say the time necessary at the starting of the vulcanization reaction; T ⁇ (for example T 99 ) is the time necessary to achieve a conversion of ⁇ %, that is to say ⁇ % (for example 99%) of the difference between the minimum and maximum torques.
• the conversion rate constant, recorded as K (expressed as min ⁇ 1 ), which is first order, calculated between 30% and 80% conversion, which makes it possible to assess the vulcanization kinetics, is also measured.
• the dynamic properties ⁇ G* and tan( ⁇ ) max are measured on a viscosity analyser (Metravib VA4000) according to Standard ASTM D 5992-96.
• the response of a sample of vulcanized composition (cylindrical test specimen with a thickness of 4 mm and with a cross section of 400 mm 2 ), subjected to a simple alternating sinusoidal shear stress, at a frequency of 10 Hz, at 60° C. is recorded.
• a strain amplitude sweep is carried out from 0.1% to 50% (outward cycle) and then from 50% to 1% (return cycle).
• the results made use of are the complex dynamic shear modulus (G*) and the loss factor tan ⁇ .
• the maximum value of tan ⁇ observed (tan( ⁇ ) max ) and the difference in complex modulus ( ⁇ G*) between the values at 0.1% and at 50% strain (Payne effect) are shown for the return cycle.
• the rubber compositions according to the invention are based on at least an (that is to say at least one) isoprene elastomer; an (at least one) inorganic filler as reinforcing filler; and an (at least one) organosiloxane coupling agent as described in detail below, which provide the bonding between the said inorganic filler and the isoprene elastomer.
• composition “based on” is to be understood as meaning a composition comprising the mixture and/or the reaction product of the various constituents used, some of these base constituents (for example, the coupling agent and the reinforcing inorganic filler) being capable of reacting or intended to react together, at least in part, during the various phases of manufacture of the compositions, in particular during their vulcanization (curing).
• diene elastomer or rubber, the two terms being regarded here as synonymous
• elastomer should be understood as meaning by definition an elastomer resulting at least in part (i.e., a homopolymer or a copolymer) from diene monomers, that is to say from monomers bearing two carbon-carbon double bonds which may or may not be conjugated.
• essentially unsaturated diene elastomer is understood here to mean a diene elastomer resulting at least in part from conjugated diene monomers having a level of units of diene origin (conjugated dienes) which is greater than 15% (mol %).
• the term “highly unsaturated” diene elastomer is understood to mean in particular a diene elastomer having a level of units of diene origin (conjugated dienes) which is greater than 50%.
• isoprene elastomer is understood to mean, in the present patent application, in a known way, an isoprene homopolymer or copolymer, in other words a diene elastomer chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), the various copolymers of isoprene and the blends of these elastomers.
• NR natural rubber
• IR synthetic polyisoprenes
• isoprene copolymers of isobutene/isoprene copolymers (butyl rubber-IIR), isoprene/styrene copolymers (SIR), isoprene/butadiene copolymers (BIR) or isoprene/butadiene/styrene copolymers (SBIR).
• isoprene copolymers of isobutene/isoprene copolymers (butyl rubber-IIR), isoprene/styrene copolymers (SIR), isoprene/butadiene copolymers (BIR) or isoprene/butadiene/styrene copolymers (SBIR).
• This isoprene elastomer is preferably natural rubber or a synthetic polyisoprene of the cis-1,4 type. Use is preferably made, among these synthetic polyisoprenes, of polyisoprenes having a level (mol %) of cis-1,4 bonds of greater than 90%, more preferably still of greater than 98%.
• compositions of the invention may contain, as a blend with the above isoprene elastomer, diene elastomers other than isoprene elastomers, as the minor component (i.e., for less than 50% by weight) or as the major component (i.e., for more than 50% by weight), according to the applications targeted. They might also comprise nondiene elastomers, indeed even polymers other than elastomers, for example thermoplastic polymers.
• nonisoprene diene elastomers of any highly unsaturated diene elastomer chosen in particular from the group consisting of polybutadienes (BR), butadiene copolymers, in particular styrene/butadiene copolymers (SBR), and the blends of these various elastomers.
• BR polybutadienes
• SBR styrene/butadiene copolymers
• the improvement in the coupling contributed by the invention is particularly notable with regard to rubber compositions for which the elastomeric base is composed predominantly (i.e., to more than 50% by weight) of polyisoprene, i.e., natural rubber or synthetic polyisoprene.
• composition in accordance with the invention is intended in particular for a tyre tread, whether a new tyre or a waste tyre (retreading), in particular for a tyre intended for commercial or utility vehicles, such as heavy-duty vehicles, i.e. underground, bus, heavy road transport vehicles (lorries, tractors, trailers) or off-road vehicles.
• heavy-duty vehicles i.e. underground, bus, heavy road transport vehicles (lorries, tractors, trailers) or off-road vehicles.
• the best embodiment known of the invention consists in using, as isoprene elastomer, solely polyisoprene, more preferably natural rubber. It is for such conditions that the best performance in terms of rolling resistance and wear resistance has been observed.
• the composition in accordance with the invention may contain at least one essentially saturated diene elastomer, in particular at least one EPDM copolymer or one butyl rubber (optionally chlorinated or brominated), whether these copolymers are used alone or as a blend with highly unsaturated diene elastomers as mentioned above, in particular NR or IR, BR or SBR.
• any inorganic or mineral filler whatever its colour and its origin (natural or synthetic), also known as “white” filler, “clear” filler or even “nonblack” filler, in contrast with carbon black, this inorganic filler being capable of reinforcing, by itself alone, without means other than an intermediate coupling agent, a rubber composition intended for the manufacture of a tyre tread, in other words capable of replacing, in its reinforcing role, a conventional tyre-grade carbon black for a tread.
• Such a filler is generally characterized by the presence of functional groups, in particular hydroxyl (—OH) groups, at its surface, thus requiring the use of a coupling agent or system intended to provide a stable chemical bond between the isoprene elastomer and the said filler.
• functional groups in particular hydroxyl (—OH) groups
• the reinforcing inorganic filler is a filler of the siliceous or aluminous type or a mixture of these two types of fillers.
• the silica (SiO 2 ) used can be any reinforcing silica known to a person skilled in the art, in particular any precipitated or pyrogenic silica exhibiting a BET specific surface and a CTAB specific surface which are both less than 450 m 2 /g, preferably from 30 to 400 m 2 /g.
• HDSs Highly dispersible precipitated silicas
• the Ultrasil 7000 silicas from Degussa the Zeosil 1165 MP, 1135 MP and 1115 MP silicas from Rhodia
• the Hi-Sil EZ150G silica from PPG the Zeopol 8715, 8745 or 8755 silicas from Huber or the silicas as described in Application WO 03/016387.
• the reinforcing alumina (Al 2 O 3 ) preferably used is a highly dispersible alumina having a BET specific surface ranging from 30 to 400 m 2 /g, more preferably between 60 and 250 m 2 /g, and a mean particle size at most equal to 500 nm, more preferably at most equal to 200 nm. Mention may in particular be made, as nonlimiting examples of such reinforcing aluminas, of the “Baikalox A125” or “CR125” (Ba ⁇ kowski), “APA-100RDX” (Condea), “Aluminoxide C” (Degussa) or “AKP-G015” (Sumitomo Chemicals) aluminas.
• inorganic filler capable of being used in the rubber compositions of the invention, of aluminium (oxide) hydroxides, aluminosilicates, titanium oxides, silicon carbides or nitrides, all of the reinforcing type as described, for example, in Applications WO 99/28376, WO 00/73372, WO 02/053634, WO 2004/003067 and WO 2004/056915.
• the reinforcing inorganic filler used in particular if it is silica, preferably has a BET specific surface of between 60 and 350 m 2 /g.
• An advantageous embodiment of the invention consists in using a reinforcing inorganic filler, in particular a silica, having a high BET specific surface within a range from 130 to 300 m 2 /g, due to the high reinforcing power recognized for such fillers.
• a reinforcing inorganic filler in particular a silica, exhibiting a BET specific surface of less than 130 m 2 /g, preferably in such a case of between 60 and 130 m 2 /g (see, for example, Applications WO03/002648 and WO03/002649).
• reinforcing inorganic filler is not important, whether it is in the form of a powder, of microbeads, of granules, of balls or any other appropriate densified form.
• reinforcing inorganic filler is also understood to mean mixtures of different reinforcing inorganic fillers, in particular of highly dispersible siliceous and/or aluminous fillers as described above.
• this level of reinforcing inorganic filler will be chosen between 20 and 200 phr, more preferably between 30 and 150 phr, in particular greater than 40 phr (for example between 40 and 120 phr, in particular between 40 and 80 phr).
• 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 volumetric method (5 points)-gas: nitrogen-degassing: 1 hour at 160° C.-relative pressure range p/po: 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).
• a reinforcing filler of another nature in particular an organic filler
• 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 bonding between the filler and the elastomer.
• an (inorganic filler/diene elastomer) coupling agent carries, in a known way, at least two functional groups, recorded here as “Y” and “X”, which allow it to be able to be grafted, on the one hand, to the reinforcing inorganic filler by means of the “Y” functional group and, on the other hand, to the diene elastomer by means of the “X” functional group.
• a covering agent for the inorganic filler comprises the “Y” functional group alone, for example a hydroxyl group or a hydrolysable group, active with regard to the functional sites (for example hydroxyl —OH sites) of the inorganic filler, but is in any case devoid of the second “X” functional group, active with regard to the diene elastomer.
• the coupling agent used in the rubber compositions in accordance with the invention is a polyfunctional (that is to say, at least bifunctional) organosiloxane comprising per molecule, grafted to its silicon atoms, on the one hand at least one hydroxyl or hydrolysable functional group (“Y” radical or functional group above) allowing it to be grafted to the reinforcing inorganic filler and, on the other hand, which is the essential characteristic of this organosiloxane for the targeted application, at least one group bearing at least one azodicarbonyl functional group —CO—N ⁇ N—CO— (“X” radical or functional group) allowing it to be grafted to the isoprene elastomer.
• Y hydroxyl or hydrolysable functional group
• polyfunctional organosiloxane is thus understood to mean any siloxane compound bearing, as “Y” functional group, at least one siloxyl unit equipped with one, two or three OH group(s) or hydrolysable monovalent group(s) and, as “X” functional group, at least one siloxyl unit equipped with at least one azo double bond activated by the presence of a carbonyl group (>C ⁇ O) on each of the two nitrogen atoms, allowing the formation of a covalent bond with the isoprene elastomer.
• the polyfunctional organosiloxane which can be used in the composition of the invention is an organosiloxane composed of identical or different siloxyl units of the following average formula (I):
• G 2 and G 3 radicals can be carried by the same silicon atom or by two different silicon atoms.
• G 3 has the specific formula (II):
• the organosiloxane is composed of identical or different siloxyl units of average formula (III):
• the preferred organosiloxane above is composed of identical or different siloxyl units of equivalent average formula (IV) or (V):
• G 2 b G 1 a (A-CO—N ⁇ N—CO-Z)SiO (3-a-b)/2 (V)
• organosiloxane of formula (IV) or (V) may also be represented, in accordance with another symbolic representation well known to a person skilled in the art for organosiloxane compounds, according to the equivalent formula (VI) or (VII) respectively:
• the organosiloxane is preferably a siloxane oligomer comprising from 2 to 20, more preferably from 2 to 12 (for example from 2 to 6), silicon atoms (number corresponding to the sum m+n+o+p+q of the formula VII).
• Such preferred siloxane oligomers are, for example, those in the formula (VII) of which:
• the divalent group Z is preferably chosen from saturated or unsaturated aliphatic hydrocarbon groups, saturated, unsaturated and/or aromatic, monocyclic or polycyclic, carbocyclic groups and groups exhibiting a saturated or unsaturated aliphatic hydrocarbon part and a carbocyclic part as defined above.
• This group Z preferably comprises from 1 to 18 carbon atoms; more preferably it represents an alkylene chain, a saturated cycloalkylene group, an arylene group or a divalent group composed of a combination of at least two of these groups.
• the monovalent hydrocarbon group which may be represented by A may be linear or branched, aliphatic or carbocyclic, in particular aromatic; it can be saturated or unsaturated and substituted or unsubstituted.
• the term aliphatic hydrocarbon group is understood to mean an optionally substituted linear or branched group preferably comprising from 1 to 18 carbon atoms.
• the said aliphatic hydrocarbon group comprises from 1 to 12 carbon atoms, better still from 1 to 8 carbon atoms and more preferably still from 1 to 6 carbon atoms.
• the unsaturated aliphatic hydrocarbon groups which may be used comprise one or more unsaturations, preferably one, two or three unsaturations of ethylenic (double bond) and/or acetylenic (triple bond) type. Examples thereof are the alkenyl or alkynyl groups deriving from the alkyl groups defined above by removal of two or more hydrogen atoms.
• the unsaturated aliphatic hydrocarbon groups comprise a single unsaturation.
• carbocyclic radical is understood to mean an optionally substituted, preferably C 3 -C 50 , monocyclic or polycyclic radical.
• it is a C 3 -C 18 radical which is preferably mono-, bi- or tricyclic.
• the carbocyclic radical comprises more than one cyclic nucleus (case of polycyclic carbocycles)
• the cyclic nuclei are fused in pairs. Two fused nuclei can be ortho-fused or peri-fused.
• the carbocyclic radical may comprise, unless otherwise indicated, a saturated part and/or an aromatic part and/or an unsaturated part.
• saturated carbocyclic radicals are cycloalkyl groups.
• the cycloalkyl groups are C 3 -C 18 , better still C 5 -C 10 , cycloalkyl groups.
• the unsaturated carbocycle or any unsaturated part of carbocyclic type exhibits one or more ethylenic unsaturations, preferably one, two or three. It advantageously comprises from 6 to 50 carbon atoms, better still from 6 to 20 carbon atoms, for example from 6 to 18 carbon atoms.
• Examples of unsaturated carbocycles are C 6 -C 10 cycloalkenyl groups.
• Examples of aromatic carbocyclic radicals are C 6 -C 18 aryl groups and in particular phenyl, naphthyl, anthryl and phenanthryl.
• a group exhibiting both an aliphatic hydrocarbon part as defined above and a carbocyclic part as defined above is, for example, an arylalkyl group, such as benzyl, or an alkylaryl group, such as tolyl.
• the substituents of the aliphatic hydrocarbon groups or parts and of the carbocyclic groups or parts are, for example, alkoxyl groups in which the alkyl part is preferably as defined above.
• Z′ can be identical to Z or different from the latter; it makes it possible to connect the azodicarbonyl functional group to an Si atom of the organosiloxane, it being possible for the latter to be identical to or different from the Si atom connected to Z.
• Z′ has the same definition and the same preferred characteristics as those described above for Z.
• At least one of the A, Z and, if applicable, Z′ groups comprises a (at least one) heteroatom preferably chosen from O, S and N. This heteroatom is preferably connected directly to the adjacent carbonyl bond.
• the monovalent hydrocarbon radical A When such a heteroatom is carried by the monovalent hydrocarbon radical A, it is preferably carried in the form of a monovalent hydrocarbon residue chosen from —OR, —NR and —SR (R being any monovalent hydrocarbon radical preferably comprising from 1 to 18 carbon atoms), the free valency of which is more preferably directly connected to the adjacent carbonyl bond; the —OR residue is preferred, with R representing a C 1 -C 6 alkyl, preferably a C 1 -C 4 alkyl (methyl, ethyl, propyl, butyl), more preferably a C 1 alkyl (methyl) or a C 2 alkyl (ethyl).
• R being any monovalent hydrocarbon radical preferably comprising from 1 to 18 carbon atoms
• the —OR residue is preferred, with R representing a C 1 -C 6 alkyl, preferably a C 1 -C 4 alkyl (methyl, ethyl, propyl, butyl), more
• Z′ When such a heteroatom is carried by Z and/or, if applicable, Z′ (i.e., by Z only, by Z′ only or by both), it is preferably carried in the form of a divalent hydrocarbon residue chosen from the —R′—NH—; —R′—O; and —R′—S— residues (R′ being any divalent hydrocarbon radical preferably comprising from 1 to 18 carbon atoms); the —R′—NH— residue is preferred, with R′ representing a C 1 -C 6 alkylene, preferably a C 1 -C 4 alkylene (methylene, ethylene, propylene, butylene), more preferably a C 3 alkylene (propylene).
• At least one, more preferably all, of the following characteristics is/are confirmed in the formulae (I) to (VII) above:
• At least one, more preferably all, of the following characteristics is/are confirmed in the formulae (I) to (VII) above:
• G 1 and G 2 might also form, together and with the silicon atom which carries them, a monocyclic or polycyclic carbocyclic group having from 2 to 10 cyclic carbon atoms and being able to comprise one or more cyclic heteroatom(s) which is/are oxygen(s). Mention will be made, by way of example, of, for example, the rings:
• Azosilanes of formula (V) in the structure of which the A symbol comprises an oxygen atom as heteroatom and which correspond to the preferred characteristics set out above are in particular those composed of identical or different siloxyl units of average formula (VIII) which follows:
• Z (and, if applicable, Z′) is a divalent radical chosen from the group consisting of —(CH 2 ) y —, —NH—(CH 2 ) y — and —O—(CH 2 ) y —, y being an integer from 1 to 6, in particular from 1 to 4, especially equal to 3.
• organosiloxane coupling agents described above can be prepared, for example, according to a synthetic process which consists in oxidizing the hydrazo group of a precursor reactant of formula (X):
• an oxidizing system comprising at least one oxidizing agent (for example a halogen, such as bromine) and at least one base (for example an inorganic base, such as Na 2 CO 3 ), while involving an additional reactant chosen from mono- and polyalkoxysilanes (by way of example, trimethylethoxysilane) and while preferably operating in an organic liquid medium (for example while using a solvent, such as dichloromethane).
• oxidizing agent for example a halogen, such as bromine
• base for example an inorganic base, such as Na 2 CO 3
• an additional reactant chosen from mono- and polyalkoxysilanes by way of example, trimethylethoxysilane
• an organic liquid medium for example while using a solvent, such as dichloromethane
• An advantageous procedure for bearing out this process consists in charging to the reactor, at ambient temperature (23° C.): the precursor reactant (X) above, the base (its amount depending on the oxidizing agent employed; for example, in the case of bromine, two molar equivalents of base are used with respect to the bromine), the organic solvent and the additional reactant (its amount corresponding, for example, to at least one molar equivalent with respect to the precursor), and in then gradually adding the oxidizing system to the reaction medium (the molar amount of oxidizing system being, for example, stoichiometric with respect to that of the precursor).
• the overall content of coupling system is preferably between 2 and 15 phr, more preferably between 2 and 12 phr (for example between 4 and 8 phr). However, it is generally desirable to use as little as possible thereof.
• the level of coupling system typically represents between 0.5 and 15% by weight, with respect to the amount of inorganic filler; preferably, it is less than 12% by weight, more preferably less than 10% by weight, with respect to this amount of filler.
• All or a portion of the coupling system according to the invention might be pregrafted (via the “X” functional groups) to the isoprene elastomer of the composition of the invention, the elastomer thus functionalized or “precoupled” then comprising the free “Y” functional groups for the reinforcing inorganic filler. All or a portion of this coupling system might also be pregrafted (via the “Y” functional groups) to the reinforcing inorganic filler, it being possible for the filler thus “precoupled” subsequently to be bonded to the diene elastomer via the free “X” functional groups.
• the rubber compositions in accordance with the invention also comprise all or a portion of the usual additives generally used in elastomer compositions intended for the manufacture of tyres or tyre semi-finished products, such as, for example, plasticizing agents or extending oils, whether the latter are aromatic or nonaromatic in nature, pigments, protection agents, such as antiozone waxes, chemical antiozonants, antioxidants, which it is preferable to keep present in the body, antifatigue agents, reinforcing or plasticizing resins, bismaleimides, methylene acceptors (for example, phenolic novolak resin) or methylene donors (for example, HMT or H3M), such as described, for example, in the abovementioned Application WO 02/10269, a crosslinking system based either on sulphur or on sulphur donors and/or on peroxides and/or on bismaleimides, vulcanization accelerators and/or activators, or antireversion agents, such as, for example, sodium
• these compositions comprise, as preferred nonaromatic or very slightly aromatic plasticizing agent, at least one compound chosen from the group consisting of naphthenic oils, paraffinic oils, MES oils, TDAE oils, glycerol esters (in particular trioleates), plasticizing hydrocarbon resins exhibiting a high Tg preferably of greater than 30° C., and the mixtures of such compounds.
• the overall level of such a preferred plasticizing agent is preferably between 15 and 45 phr, more preferably between 20 and 40 phr.
• Inert fillers i.e., nonreinforcing fillers
• nonreinforcing fillers such as particles of clay, bentonite, talc, chalk, kaolin, which can be used, for example, in side walls or treads of coloured tyres
• inert fillers can also be added, depending on the targeted application, to the reinforcing filler described above, that is to say the nonblack reinforcing filler (in particular inorganic filler) plus carbon black, if applicable.
• compositions can also comprise, in addition to the coupling agents, coupling activators, covering agents (comprising, for example, just the “Y” functional group) of the nonblack reinforcing filter and more generally processing aids capable, in a known way, by virtue of an improvement in the dispersion of the nonblack filler in the rubber matrix and of a lowering in the viscosity of the compositions, of improving their processing property in the raw state, these agents being, for example, hydroxylated or hydrolysable silanes, such as hydroxysilanes, or alkylalkoxysilanes (in particular alkyltriethoxysilanes), polyols, polyethers (for example polyethylene glycols), primary, secondary or tertiary amines (for example trialkanolamines), hydroxylated or hydrolysable polyorganosiloxanes, for example ⁇ , ⁇ -dihydroxypolyorganosiloxanes (in particular ⁇ , ⁇ -dihydroxypolydi
• compositions are manufactured in appropriate mixers using two successive preparation phases well known to a person skilled in the art: a first phase of thermomechanical working or kneading (sometimes referred to as “nonproductive” phase) at high temperature, up to a maximum temperature (recorded as T max ) of between 110° C. and 190° C., preferably between 130° C. and 180° C., followed by a second phase of mechanical working (sometimes referred to as “productive” phase) at a lower temperature, typically of less than 120° C., for example between 60° C. and 100° C., finishing phase during which the crosslinking or vulcanization system is incorporated.
• a first phase of thermomechanical working or kneading (sometimes referred to as “nonproductive” phase) at high temperature, up to a maximum temperature (recorded as T max ) of between 110° C. and 190° C., preferably between 130° C. and 180° C.
• T max maximum temperature
• the manufacturing process according to the invention is characterized in that at least the reinforcing inorganic filler and all or a portion of the coupling agent are incorporated by kneading with the diene elastomer, during the first “nonproductive” phase, that is to say that at least these various base constituents are introduced into the mixer and that kneading is carried out thermomechanically, in one or more stages, until a maximum temperature of between 1110° C. and 190° C., preferably between 130° C. and 180° C., is reached.
• the first (nonproductive) phase is carried out in a single thermomechanical stage during which, in a first step, all the necessary base constituents (diene elastomer, reinforcing inorganic filler and all or a portion of the coupling agent) are introduced into an appropriate mixer, such as a normal internal mixer, followed, in a second step, for example after kneading for one to two minutes, by the optional additional covering agents or processing aids and various other additives, with the exception of the vulcanization system.
• the total duration of the kneading, in this nonproductive phase is preferably between 2 and 10 min.
• the second part of the coupling agent, if applicable, and then the vulcanization system are then incorporated at low temperature, generally in an external mixer such as an open mill; the entire mixture is then mixed (productive phase) for a few minutes, for example between 5 and 15 minutes.
• all of the organosiloxane coupling agent can be introduced during the nonproductive phase, at the same time as the inorganic filler, or otherwise in a form divided up (for example in a proportion of 75/25, 50/50 or 25/75 respective parts by weight) over the two phases, respectively nonproductive (i.e., in the internal mixer) and then productive (for example, in the external mixer).
• organosiloxane in a form supported (placing on the support being carried out beforehand) on a solid compatible with the chemical structures corresponding to this compound; such a support is in particular carbon black.
• a support is in particular carbon black.
• the final composition thus obtained is subsequently calendered, for example in the form of a sheet, or else extruded, for example to form a rubber profiled element used for the manufacture of semi-finished products, such as treads, crown reinforcement plies, side walls, carcass reinforcement plies, beads, protectors, air chambers or airtight internal rubbers for a tubeless tyre.
• a rubber profiled element used for the manufacture of semi-finished products, such as treads, crown reinforcement plies, side walls, carcass reinforcement plies, beads, protectors, air chambers or airtight internal rubbers for a tubeless tyre.
• the vulcanization (or curing) is carried out in a known way at a temperature generally of between 130° C. and 200° C., preferably under pressure, for a sufficient time which can vary, for example, between 5 and 90 min, depending in particular on the curing temperature, the vulcanization system adopted and the vulcanization kinetics of the composition under consideration.
• the vulcanization system proper is preferably based on sulphur and on a primary vulcanization accelerator, in particular an accelerator of the sulphenamide type.
• a primary vulcanization accelerator in particular an accelerator of the sulphenamide type.
• Various known vulcanization activators or secondary accelerators such as zinc oxide, stearic acid, guanidine derivatives (in particular diphenylguanidine), optional antireversion agents, and the like, incorporated during the first nonproductive phase and/or during the productive phase, are additional to this crosslinking system.
• Sulphur is used at a preferable level of between 0.5 and 10 phr, more preferably of between 0.5 and 5.0 phr, for example between 0.5 and 3.0 phr, when the invention is applied to a tyre tread.
• the primary vulcanization accelerator is used at a preferable level of between 0.5 and 10 phr, more preferably of between 0.5 and 5.0 phr in particular when the
• the invention relates to the rubber compositions described above both in the “raw” state (i.e., before curing) and in the “cured” or vulcanized state (i.e., after crosslinking or vulcanization).
• the compositions in accordance with the invention can be used alone or as a blend (i.e., as a mixture) with any other rubber composition which can be used for the manufacture of tyres.
• reaction mixture is subsequently filtered and then concentrated under vacuum. 9.77 g of a bright orange fluid liquid are obtained.
• 1 H NMR analysis shows that the compound 1 has been completely consumed, that the azo group has been selectively formed and that the SiOEt loss is limited.
• the final product obtained is a mixture of the two siloxane entities of formulae (XI-1) and (XII-1):
• the tests which follow are carried out in the following way: the natural rubber, the reinforcing filler, a portion (approximately 1 ⁇ 3) of the coupling agent and then, after kneading for one to two minutes, the various other ingredients, with the exception of the vulcanization system, are introduced into an internal mixer, 70% filled and having an initial vessel temperature of approximately 80° C. Thermomechanical working (nonproductive phase) is then carried out in one stage (total duration of the kneading equal to approximately 4 min) until a maximum “dropping” temperature of approximately 160° C. is reached.
• the mixture thus obtained is recovered and cooled and then the remainder of the coupling agent and then the vulcanization system (sulphur and sulphenamide accelerator) are added on an external mixer (homofinisher), the combined mixture being mixed (productive phase) for approximately 5-10 min.
• compositions thus obtained are subsequently calendered, either in the form of sheets (thickness of 2 to 3 mm) or of fine 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, for example as tyre semi-finished products, in particular as tyre treads.
• the aim of this test is to demonstrate the improved coupling performance contributed by the siloxane coupling agent synthesized above (paragraph III-1), compared with a conventional coupling agent of the alkoxysilane type (TESPT).
• compositions based on natural rubber which are reinforced with an HDS silica are prepared, these two compositions differing only in the nature of the coupling agents used:
• Tables 1 and 2 give the formulations of the various compositions (Table 1—levels of the various products, expressed in phr—parts by weight per one hundred parts of elastomer) and also their rheometric properties and properties after curing (at 150° C. for approximately 20 min); the vulcanization system is composed of sulphur and sulphenamide.
• Table 2 shows first of all, for the composition in accordance with the invention C-2 compared with the control composition C-1, markedly faster vulcanization kinetics, illustrated by a conversion rate constant K which is markedly greater (multiplied by approximately 1.8) and by a markedly reduced curing time (T 99 -Ti) (divided by 1.8).
• the composition in accordance with the invention exhibits substantially equivalent properties at break, but the highest values for modulus under strong strain (M100 and M300) and for M300/M100 ratio, a clear indicator to a person skilled in the art of better reinforcing contributed by the inorganic filler and the siloxane coupling agent.
• composition of the invention reveals a markedly improved hysteresis, as is shown by substantially reduced values for tan( ⁇ ) max and ⁇ G*, which is the recognized indicator of a reduction in the rolling resistance of tyres and consequently in the energy consumption of the motor vehicles equipped with such tyres.
• the invention has particularly advantageous applications in rubber compositions intended for the manufacture of tyre treads based on isoprene elastomer, in particular when these treads are intended for tyres for commercial vehicles of the heavy-duty type.

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