Rubber composition comprising masterbatch

Abstract

The present invention relates to a rubber composition comprising a masterbatch. The invention relates to a rubber composition based on at least one diene elastomer, a filler comprising at least carbon black and an inorganic filler, and a cross-linking system, the inorganic filler content being less than or equal to 50 parts by weight per 100 parts of elastomer (phr).

Description

Technical Field

[0001] The present invention relates to a rubber composition based on at least one diene elastomer, a filler comprising at least carbon black and an inorganic filler, in particular silica, this composition having a very good dispersion of the filler in the elastomeric matrix. The invention more particularly relates to the preparation of such a composition based on at least one masterbatch comprising a diene elastomer and carbon black, said masterbatch itself having a very good dispersion of the carbon black in the elastomeric matrix.

[0002] The term "masterbatch" is understood to mean a composite material based on an elastomer into which fillers and optionally other additives have been introduced.

[0003] The invention relates in particular to the use of such a masterbatch for the manufacture of a diene rubber composition reinforced with a blend of organic and inorganic fillers, intended for the manufacture of tires or semifinished products of tires, in particular the treads of these tires. Background Art

[0004] It is known that in order to obtain the best possible reinforcing and hysteresis properties imparted by a filler to a tire tread, and thus to achieve high wear resistance and low rolling resistance, it is generally recommended that this filler be present in the elastomeric matrix in its final form, as finely divided as possible and as uniformly distributed as possible. However, such conditions can only be achieved if the filler has a very good capacity, on the one hand, to be incorporated into the matrix and deagglomerated during mixing with the elastomer, and, on the other hand, to be uniformly dispersed in this matrix.

[0005] This has been achieved, inter alia, by using novel rubber compositions reinforced at least in part with inorganic fillers, in particular silica, which are comparable from a reinforcement point of view to conventional tire-grade carbon black.

[0006] However, due to mutual affinity, these inorganic filler particles have an annoying tendency to clump together in the elastomer matrix. These interactive harmful consequences are that the dispersion of filler and therefore the reinforcing properties are limited to a level that is substantially lower than that which would theoretically be achieved if all (inorganic filler / elastomer) keys that can be formed during the compounding operation were actually obtained. In addition, these interactions tend to increase the viscosity of the rubber composition under uncured conditions, making them more difficult to process than when there is carbon black, even in the case of highly dispersible silica.

[0007] There are various methods for obtaining masterbatches of diene elastomers and reinforcing fillers. In particular, to improve the dispersion of the filler in the elastomeric matrix, one type of solution consists in compounding the elastomer and filler in a "liquid" phase. To this end, this method involves the elastomer in the form of a latex, in the form of water-dispersible elastomeric particles, and an aqueous dispersion of the filler, i.e., the filler dispersed in water, commonly known as a "slurry." Certain methods, such as those described in document US Pat. No. 6,048,923, make it possible to obtain masterbatches of elastomer and filler that exhibit a very good dispersion of the filler in the elastomeric matrix, a significant improvement over the dispersion of the filler in the elastomeric matrix that can be obtained during solid-phase compounding of the elastomer and the reinforcing filler. This process consists in particular in introducing a continuous flow of a first fluid consisting of an elastomer latex into a compounding zone of a coagulant reactor, introducing a second continuous flow of a second fluid consisting of an aqueous dispersion of a filler into the compounding zone under pressure so as to form a mixture with the elastomer latex, the compounding of these two fluids being sufficiently intense to enable almost complete coagulation of the elastomer latex with the filler before the outlet orifice of the coagulant reactor, and then drying the resulting coagulant.

[0008] This method is particularly suitable for producing a masterbatch with excellent dispersion from natural rubber latex and carbon black. In fact, the ability of natural rubber latex and carbon black to spontaneously cohere makes the application of this method particularly advantageous. However, this method is limited by the carbon black content present in the masterbatch. A method is needed to regulate the total filler content in the rubber composition comprising the carbon black masterbatch without affecting the processability. Summary of the Invention

[0009] Contrary to the effect of adding carbon black in solid form and contrary to the knowledge of those skilled in the art regarding the difficulties of dispersing and processing silica in an elastomeric matrix, the introduction of silica into a diene elastomer / carbon black masterbatch with very good dispersion of the carbon black in the diene elastomer matrix, in particular a masterbatch prepared according to the process described above, makes it possible to obtain novel masterbatches having improved hysteresis properties after the introduction of silica in solid form, while maintaining very good dispersion of all the fillers in the elastomeric matrix.

[0010] A subject of the present invention is therefore a rubber composition based on at least one diene elastomer, a filler comprising at least carbon black and an inorganic filler, and a crosslinking system, wherein the inorganic filler content is less than or equal to 50 parts by weight per 100 parts of elastomer (phr), characterized in that the dispersion of the filler in the elastomeric matrix has a Z value greater than or equal to 60, more preferably 80.

[0011] Preferably, this composition is obtained from a first masterbatch comprising at least a diene elastomer and carbon black, the dispersion of the carbon black in the elastomeric matrix having a Z value greater than or equal to 60, more preferably greater than or equal to 90, even more preferably, this first masterbatch is obtained by liquid phase compounding of an aqueous dispersion of a diene elastomer latex and of carbon black.

[0012] According to an advantageous embodiment, such a first masterbatch is obtained according to the following process steps: feeding a continuous flow of diene elastomer latex into the mixing zone of a coagulant reactor, said coagulant reactor defining an elongated coagulant zone extending between said mixing zone and an outlet, feeding a continuous flow of a fluid containing filler under pressure into the mixing zone of the coagulant reactor to form a coagulant mixture, and drying the coagulant obtained above to recover the first masterbatch.

[0013] According to one preferred embodiment, the diene elastomer of the composition is chosen from polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and blends of these elastomers, more preferably the diene elastomer is natural rubber.

[0014] According to another preferred embodiment, the inorganic filler of the composition is silica or chemically treated silica.

[0015] Another subject of the present invention is a process for preparing a composition comprising at least one diene elastomer and a filler, said filler comprising at least one carbon black and an inorganic filler, and a crosslinking system, wherein the content of inorganic filler is less than or equal to 50 parts by weight per 100 parts of elastomer, said process comprising the steps of: preparing a first masterbatch of diene elastomer and carbon black, comprising feeding a continuous stream of diene elastomer latex into a mixing zone of a coagulant reactor, said coagulant reactor defining an elongated coagulant zone extending between said mixing zone and an outlet, and feeding a continuous stream of a fluid containing a filler including carbon black into the mixing zone of the coagulant reactor under pressure to form a coagulant mixture; drying the coagulant obtained above to recover the first masterbatch; incorporating the inorganic filler and the other ingredients of the composition, except the crosslinking system, into the first masterbatch obtained above by thermomechanically kneading all the materials until a maximum temperature of between 130° C. and 200° C. in a mixer, to produce a nonproductive compound. compound); cooling the combined mixture to a temperature of less than 100° C. before incorporating a crosslinking system; and subsequently incorporating the crosslinking system and an additional diene elastomer, which is identical to or different from the at least one diene elastomer, into the non-productive compound and kneading all the materials to a maximum temperature of less than 120° C. In other words, according to one embodiment, the additional elastomer is added in the productive pass.

[0016] Advantageously, the additional diene elastomer is incorporated into the compound in an amount that reduces the carbon black in the masterbatch to a predetermined level in the rubber composition.

[0017] The present invention also relates to a process for preparing a composition comprising at least one diene elastomer and a filler, said filler comprising at least one carbon black and an inorganic filler, wherein the content of the inorganic filler is less than or equal to 50 parts by weight per 100 parts of elastomer, and a crosslinking system, said process comprising the following steps: preparing a first masterbatch of diene elastomer and carbon black, comprising: feeding a continuous stream of diene elastomer latex into a mixing zone of a coagulant reactor, said coagulant reactor defining an elongated coagulant zone extending between said mixing zone and an outlet, and feeding a continuous stream of a fluid comprising a filler containing carbon black under pressure into the mixing zone of the coagulant reactor to form a coagulant mixture; drying the coagulant obtained in order to recover a first masterbatch of diene elastomer and carbon black; a masterbatch; incorporating the inorganic filler and the other ingredients of the composition except the crosslinking system into the first masterbatch obtained above by thermomechanically kneading all the materials until a maximum temperature between 130° C. and 200° C. in a mixer to produce a first non-productive compound; cooling the first non-productive compound to a temperature below 100° C.; incorporating at least one additional ingredient of the composition into the first non-productive compound to produce at least a second non-productive compound; and cooling the combined mixture to a temperature below 100° C., subsequently incorporating all or part of the crosslinking system into the at least second non-productive compound and kneading all the materials until a maximum temperature of below 120° C.

[0018] In one embodiment, the additional ingredient is an additional diene elastomer, which may be identical to or different from the at least one diene elastomer. In another embodiment, the additional ingredient is part of a crosslinking system. In another embodiment, the additional ingredient is not part of a crosslinking system or an additional elastomer, but rather an additive such as an antiozonant, wax, oil, etc.

[0019] The present invention also relates to a process for preparing a composition comprising at least one diene elastomer and a filler, said filler comprising at least one carbon black and an inorganic filler, and a crosslinking system, wherein the content of inorganic filler is less than or equal to 50 parts by weight per 100 parts of elastomer, said process comprising the following steps: preparing a first masterbatch of diene elastomer and carbon black, comprising: feeding a continuous stream of diene elastomer latex into a mixing zone of a coagulant reactor, said coagulant reactor defining an elongated coagulant zone extending between said mixing zone and an outlet, and feeding a continuous stream of a fluid containing a filler including carbon black under pressure into the mixing zone of the coagulant reactor to form a coagulant mixture; drying the coagulant obtained in this manner to recover the first masterbatch;

[0020] The inorganic filler and the other ingredients of the composition, a part of the crosslinking system are incorporated into the first masterbatch obtained above by thermomechanically kneading all the materials until a maximum temperature of between 130°C and 200°C is reached in a mixer to produce a non-productive compound; the combined mixture is cooled to a temperature below 100°C and the remaining part of the crosslinking system is subsequently incorporated into the non-productive compound and all the materials are kneaded until a maximum temperature of below 120°C is reached.

[0021] According to a preferred embodiment of the process, the diene elastomer is natural rubber and the inorganic filler is silica or silica-coated carbon black.

[0022] According to one embodiment of the method, the carbon black content in the masterbatch is between 1 and 100 phr, and the inorganic filler content is between 0.25 and 50 phr.

[0023] In one embodiment, the composition can be incorporated into the carcass, a portion of the belt structure, and / or the tread. For example, as part of the carcass, the component can be an apex, wirecoat, ply coat, squeegee compounds, gum strips, chafer, reinforcing sidewall inserts, or an exposed sidewall. As part of the tread area, the component can be the tread base or tread cap. The composition can also be an innerliner.

[0024] A final subject of the invention is a finished or semi-finished article, a tire tread, a tire component or a semi-finished product comprising a composition as described above or a masterbatch as described above.

[0025] The present invention discloses the following solutions:

[0026] Option 1. A method for preparing a rubber composition based on at least one diene elastomer, a filler comprising at least carbon black and an inorganic filler, and a crosslinking system, wherein the content of inorganic filler is less than or equal to 50 parts by weight per 100 parts of elastomer, the method comprising:

[0027] A first masterbatch of diene elastomer and carbon black is prepared, comprising:

[0028] feeding a continuous flow of diene elastomer latex into a mixing zone of a coagulant reactor, said coagulant reactor defining an elongated coagulant zone extending between said mixing zone and an outlet, and

[0029] feeding a continuous stream of a fluid containing a filler comprising carbon black under pressure into a mixing zone of a coagulant reactor to form a coagulant mixture,

[0030] drying the coagulant obtained above to recover the first masterbatch;

[0031] incorporating the inorganic filler and the other ingredients of the composition, except the crosslinking system, into the first masterbatch obtained above by thermomechanically kneading all the materials until a maximum temperature of between 130° C. and 200° C. is reached in a mixer, so as to produce a non-productive compound;

[0032] Cooling the combined mixture to a temperature below 100°C before incorporating the crosslinking system;

[0033] The crosslinking system and an additional diene elastomer, which is identical or different from the at least one diene elastomer, are subsequently incorporated into the non-productive compound and all materials are kneaded until a maximum temperature of less than 120° C.

[0034] Option 2. The method of Option 1, wherein the additional diene elastomer is incorporated into the non-productive compound in an amount to reduce the carbon black in the masterbatch to a predetermined level in the rubber composition.

[0035] 3. A method for preparing a rubber composition based on at least one diene elastomer, a filler comprising at least carbon black and an inorganic filler, and a crosslinking system, wherein the content of inorganic filler is less than or equal to 50 parts by weight per 100 parts of elastomer, the method comprising:

[0036] A first masterbatch of diene elastomer and carbon black is prepared, comprising:

[0037] feeding a continuous flow of diene elastomer latex into a mixing zone of a coagulant reactor, said coagulant reactor defining an elongated coagulant zone extending between said mixing zone and an outlet, and

[0038] feeding a continuous stream of a fluid containing a filler containing carbon black under pressure into a mixing zone of a coagulant reactor to form a coagulant mixture,

[0039] drying the coagulant obtained above to recover the first masterbatch;

[0040] incorporating the inorganic filler and the other ingredients of the composition, except the crosslinking system, into the first masterbatch obtained above by thermomechanically kneading all the materials until a maximum temperature of between 130° C. and 200° C. is reached in a mixer, so as to produce a first non-productive compound;

[0041] cooling the first non-productive compound to a temperature below 100° C.;

[0042] incorporating at least one additional ingredient of the composition into the first non-productive compound to produce at least a second non-productive compound; and

[0043] The combined mixture is cooled to a temperature below 100°C,

[0044] All or part of the crosslinking system is then incorporated into the at least second non-productive compound and all materials are kneaded until a maximum temperature of less than 120°C.

[0045] Option 4. The process according to option 3, wherein the at least one additional ingredient is an additional diene elastomer, the additional diene elastomer being the same as or different from the at least one diene elastomer.

[0046] Item 5. The method of item 4, wherein the additional diene elastomer is incorporated into the first non-productive compound in an amount to reduce the carbon black in the masterbatch to a predetermined level in the rubber composition.

[0047] Option 6. The method according to Option 3, wherein the at least one additional ingredient is part of a crosslinking system, and the at least one additional ingredient is selected from sulfur, sulfur donors, accelerators and vulcanization activators.

[0048] Item 7. The process according to item 1, wherein the diene elastomer is chosen from polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymers, isoprene copolymers, and blends of these elastomers.

[0049] Item 8. The method of item 7, wherein the diene elastomer is natural rubber.

[0050] Item 9. The process according to item 3, wherein the diene elastomer is chosen from polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymers, isoprene copolymers and blends of these elastomers.

[0051] Item 10. The method of item 9, wherein the diene elastomer is natural rubber.

[0052] Option 11. The method according to Option 1, wherein the inorganic filler is silica or silica-coated carbon black.

[0053] Option 12. The method according to Option 1, wherein the inorganic filler is silica or silica-coated carbon black.

[0054] Option 13. The method according to Option 1, wherein the carbon black content in the masterbatch is between 30 and 80 phr, and the inorganic filler content is between 5 and 50 phr.

[0055] Option 14. The method according to Option 3, wherein the carbon black content in the masterbatch is between 30 and 80 phr, and the inorganic filler content is between 5 and 50 phr.

[0056] Option 15. The method according to Option 1, wherein the carbon black content in the rubber composition is between 30 and 80 phr, and the inorganic filler content is between 5 and 50 phr.

[0057] Option 16. The method according to Option 3, wherein the carbon black content in the rubber composition is between 30 and 80 phr, and the inorganic filler content is between 5 and 50 phr.

[0058] 17. A method for preparing a rubber composition based on at least one diene elastomer, a filler comprising at least carbon black and an inorganic filler, and a crosslinking system, wherein the inorganic filler content is less than or equal to 50 parts by weight per 100 parts of elastomer, the method comprising:

[0059] A first masterbatch of diene elastomer and carbon black is prepared, comprising:

[0060] feeding a continuous flow of diene elastomer latex into a mixing zone of a coagulant reactor, said coagulant reactor defining an elongated coagulant zone extending between said mixing zone and an outlet, and

[0061] feeding a continuous stream of a fluid containing a filler comprising carbon black under pressure into a mixing zone of a coagulant reactor to form a coagulant mixture,

[0062] drying the coagulant obtained above to recover the first masterbatch;

[0063] incorporating the inorganic filler and the other ingredients of the composition, a part of the crosslinking system, into the first masterbatch obtained above by thermomechanically kneading all the materials until a maximum temperature of between 130° C. and 200° C. is reached in a mixer, so as to produce a non-productive compound;

[0064] Cooling the combined mixture to a temperature below 100°C;

[0065] The remainder of the crosslinking system is subsequently introduced into the non-productive compound and all materials are kneaded until a maximum temperature of less than 120° C. is achieved.

[0066] Item 18. The method of item 17, wherein the diene elastomer is natural rubber.

[0067] Option 19. The method according to Option 17, wherein the inorganic filler is silica or silica-coated carbon black.

[0068] Option 20. The method according to Option 17, wherein the carbon black content in the rubber composition is between 30 and 80 phr, and the inorganic filler content is between 5 and 50 phr. Specific implementation plan

[0069] The present invention relates to a composition based on a masterbatch of a diene elastomer and a reinforcing filler, comprising at least one diene elastomer and a filler comprising at least carbon black and an inorganic filler, wherein the content of inorganic filler is less than or equal to 50 parts by weight per 100 parts of elastomer, and wherein the dispersion of the filler in the elastomeric matrix has a Z value greater than or equal to 60, more preferably greater than or equal to 80, more preferably greater than or equal to 90. As is known, the dispersion of the filler in the elastomeric matrix can be expressed by the Z value, measured after crosslinking according to the method described by S. Otto et al. in Kautschuk Gummi Kunststoffe, 58th edition, NR 7-8 / 2005, which is in accordance with ISO 11345 standard.

[0070] The calculation of the Z value is based on the percentage of surface area in which the filler is not dispersed ("% Undispersed Surface Area"), as measured by Dynisco's "disperGRADER+" machine and its operating method and its "disperDATA" operating software, according to the equation: Z = 100 - (% Undispersed Surface Area) / 0.35.

[0071] The percentage of undispersed surface area is itself measured by a camera observing the sample surface area at 30° incident light. Bright spots are associated with fillers and agglomerates, while dark spots are associated with the rubber matrix; digital processing converts the image into a black and white image, as described in the aforementioned document by S. Otto, and the percentage of undispersed surface area can be determined.

[0072] According to one embodiment of the invention, such a composition is obtained by adding an inorganic filler to a first masterbatch comprising at least a diene elastomer and carbon black and having a dispersion of the carbon black in the elastomeric matrix having a Z value greater than or equal to 60, more preferably 90.

[0073] In this specification, unless expressly stated otherwise, all percentages (%) shown are % by weight. In addition, any numerical range represented by the expression "between a and b" represents a numerical range from greater than a to less than B (that is, excluding the limits a and b), while any numerical range represented by the expression "a to b" refers to a numerical range from a up to b (that is, including the strict limits a and b).

[0074] I. Diene Elastomer

[0075] By convention, the interchangeable terms "elastomer" and "rubber" are used without distinction herein.

[0076] In practice, various conjugated diene-based elastomers may be used in the rubber composition, such as polymers and copolymers of at least one of isoprene and 1,3-butadiene, polymers and copolymers of styrene copolymerized with at least one of isoprene and 1,3-butadiene, and mixtures thereof.

[0077] Representatives of such conjugated diene-based elastomers are, for example, composed of at least one of cis-1,4-polyisoprene (natural and synthetic), cis-1,4-polybutadiene, styrene / butadiene copolymers (prepared by aqueous emulsion polymerization and prepared by organic solvent solution polymerization), medium-vinyl polybutadiene having a vinyl 1,2 content of about 10 to about 90%, isoprene / butadiene copolymers, and styrene / isoprene / butadiene terpolymers.

[0078] Cis-1,4-polyisoprene and cis-1,4-polyisoprene natural rubber are well known to those skilled in the rubber art.

[0079] Representative synthetic polymers are butadiene and its homologues and derivatives, such as homopolymerization products of methylbutadiene, dimethylbutadiene and pentadiene, and copolymers, such as those formed from butadiene or its homologues or derivatives with other unsaturated monomers. Other unsaturated monomers include acetylenes, such as vinylacetylene; olefins, such as isobutylene, which is copolymerized with isoprene to form butyl rubber; vinyl compounds, such as acrylic acid, acrylonitrile (which is polymerized with butadiene to form NBR), methacrylic acid, and styrene (the latter compound is polymerized with butadiene to form SBR), as well as vinyl esters and various unsaturated aldehydes, ketones, and ethers, such as acrolein, methyl isopropenyl ketone, and vinyl ethyl ether.

[0080] Specific examples of synthetic rubbers include chloroprene rubber (polychloroprene), polybutadiene (including cis-1,4-polybutadiene), polyisoprene (including cis-1,4-polyisoprene), butyl rubber, halogenated butyl rubbers such as chlorobutyl rubber or bromobutyl rubber, styrene / isoprene / butadiene rubber, copolymers of 1,3-butadiene or isoprene with monomers such as styrene, acrylonitrile and methyl methacrylate, and ethylene / propylene terpolymers, also known as ethylene / propylene / diene monomer (EPDM), particularly ethylene / propylene / dicyclopentadiene terpolymers. Additional examples of rubbers that can be used include alkoxy-silyl end-functionalized solution-polymerized polymers (SBR, PBR, IBR and SIBR), silicon-coupled and tin-coupled star-branched polymers.

[0081] In practice, the preferred rubbers or elastomers are polyisoprene (natural or synthetic), polybutadiene and SBR.

[0082] In one embodiment, one elastomer is SBR, more preferably solution polymerized SBR (SSBR).SSBR can be conveniently prepared, for example, by organolithium catalysis in the presence of an organic hydrocarbon solvent.

[0083] In one embodiment, at least one elastomer is functionalized to react with the silica filler. Representative functionalized elastomers are, for example, styrene / butadiene elastomers containing one or more functional groups including:

[0084] (A) an amine functional group that can react with the hydroxyl groups on the precipitated silica,

[0085] (B) siloxy functional groups reactive with hydroxyl groups on precipitated silica, including terminal siloxy groups,

[0086] (C) a combination of amine and siloxy functional groups reactive with hydroxyl groups on the precipitated silica,

[0087] (D) a combination of thiol and siloxy (e.g., ethoxysilane) functional groups that can react with hydroxyl groups on the precipitated silica,

[0088] (E) a combination of imine and siloxy functional groups that can react with hydroxyl groups on the precipitated silica,

[0089] (F) Hydroxyl functional groups reactive with precipitated silica.

[0090] With respect to the functionalized elastomer, amine-functionalized SBR elastomers are represented by, for example, the intra-chain functionalized SBR elastomers mentioned in US Pat. No. 6,936,669, the disclosure of which is incorporated herein in its entirety.

[0091] Representative of the combination of amino-siloxy functionalized SBR elastomers having one or more amino-siloxy groups attached to the elastomer is, for example, HPR355 from JSR TM and amino-siloxy functionalized SBR elastomers as described in US Pat. No. 7,981,966, the disclosure of which is incorporated herein in its entirety.

[0092] Representative styrene / butadiene elastomers end-functionalized with silane-sulfide groups are mentioned, for example, in US Pat. Nos. 8,217,103 and 8,569,409, the disclosures of which are incorporated herein in their entireties.

[0093] Tin-coupled elastomers prepared by organic solvent polymerization may also be used, such as tin-coupled organic solution polymerization prepared styrene / butadiene copolymers, isoprene / butadiene copolymers, styrene / isoprene copolymers, polybutadiene, and styrene / isoprene / butadiene terpolymers, including the functionalized styrene / butadiene elastomers described above.

[0094] Tin-coupled styrene / butadiene copolymers can be prepared, for example, by introducing a tin coupling agent during the copolymerization of styrene / 1,3-butadiene monomers in an organic solvent solution, typically at or near the end of the polymerization reaction. Such coupling of styrene / butadiene copolymers is well known to those skilled in the art.

[0095] In practice, it is generally preferred that at least 50%, and more typically between about 60 and about 85%, of the Sn (tin) linkages in the tin-coupled elastomer are bonded to butadiene units of the styrene / butadiene copolymer to form Sn-dienyl linkages, such as butadienyl linkages.

[0096] The formation of the tin-dienyl bond can be achieved in a variety of ways, for example, by sequential addition of butadiene to the copolymerization system or by using a modifier to change the reactivity ratio of styrene and / or butadiene for the copolymerization. It is believed that these techniques are well known to those skilled in the art, whether for batch copolymerization or continuous copolymerization systems.

[0097] Various tin compounds, particularly organotin compounds, can be used for coupling elastomers. Representatives of such compounds are, for example, alkyltin trichlorides, dialkyltin dichlorides, to obtain tin-coupled styrene / butadiene copolymer elastomer variants, although trialkyltin monochlorides can be used, which simply give tin-terminated copolymers.

[0098] Examples of tin-modified or coupled styrene / butadiene copolymer elastomers may be found, for example, in US Pat. No. 5,064,901, the disclosure of which is incorporated herein in its entirety, but are not intended to be limiting.

[0099] Emulsion polymerization prepared styrene / butadiene / acrylonitrile copolymer rubbers containing from about 2 to about 40 weight percent bound acrylonitrile in the copolymer are also contemplated as diene-based rubbers for use in this invention.

[0100] Emulsion-polymerized E-SBR refers to the copolymerization of styrene and 1,3-butadiene in an aqueous emulsion. This is well known to those skilled in the art. The bound styrene content can range from, for example, about 5% to about 50%. In one aspect, the E-SBR can also contain acrylonitrile as the E-SBAR to form a terpolymer rubber. The amount of bound acrylonitrile in the terpolymer can range from, for example, about 2 to about 30% by weight.

[0101] It is further contemplated that in certain embodiments the rubber elastomer may be a butyl-type rubber, particularly a copolymer of isobutylene with minor amounts of dienes such as isoprene and halogenated butyl rubber.

[0102] These diene elastomers can be divided into two categories: “essentially unsaturated” or “essentially saturated”. In general, the expression “essentially unsaturated” is understood to mean a diene elastomer derived at least partly from conjugated diene monomers, having a content of units of diene origin (conjugated dienes) greater than 15% (mol %); thus, diene elastomers such as butyl rubber or EPDM-type diene / α-olefin copolymers do not fall within the aforementioned definition and can in particular be described as “essentially saturated” diene elastomers (low or very low content of units of diene origin, always less than 15%). Within the category of “essentially unsaturated” diene elastomers, the expression “highly unsaturated” diene elastomer is understood to mean in particular a diene elastomer having a content of units of diene origin (conjugated dienes) greater than 50%.

[0103] In general, the synthetic diene elastomer according to the invention is preferably chosen from highly unsaturated diene elastomers formed from polybutadiene (abbreviated as "BR"), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers and blends of these elastomers. Such copolymers are more preferably chosen from butadiene / styrene copolymers (SBR), isoprene / butadiene copolymers (BM), isoprene / styrene copolymers (SIR) and isoprene / butadiene / styrene copolymers (SBIR).

[0104] As specified above, preference is given to using liquid phase compounding methods in order to be able to obtain masterbatches based on diene elastomer and carbon black with very good dispersion of the carbon black in the elastomer. Thus, in particular for the production of the first masterbatch of diene elastomer and carbon black, use is made more particularly of diene elastomer latex, which is a specific form of elastomer in the form of water-dispersed elastomeric particles.

[0105] The invention therefore preferably relates to latexes of diene elastomers, such as those defined above.

[0106] More particularly, with regard to natural rubber (NR) being particularly suitable for the present invention, such natural rubber exists in various forms as explained in detail in Chapter 3 “Latex concentrates: properties and composition” by KF Gaseley, AD T Gordon and TD Pendle in “Natural Rubber Science and Technology”, AD Roberts, Oxford University Press—1988.

[0107] In particular, natural rubber latex is sold in several forms: natural rubber latex known as "field latices", natural rubber latex known as "concentrated natural rubber latex", epoxidized latex (ENR), deproteinized latex or pre-vulcanized latex. Field latices are latexes to which ammonia has been added to prevent premature coagulation, concentrated natural rubber latexes correspond to field latices that have undergone a treatment corresponding to washing and subsequent further concentration. Various classes of concentrated natural rubber latex are listed in particular according to standard ASTM D 1076-06. Among these concentrated natural rubber latexes, a distinction is made in particular between the quality known as "HA" (high ammonia) and the quality known as "LA" concentrated natural rubber latex; for the present invention, the concentrated natural rubber latex of the HA quality is advantageously used.

[0108] NR latex can be previously physically or chemically modified (centrifugation, enzyme treatment, chemical modifiers, etc.).

[0109] The latex can be used directly or can be first diluted in water to facilitate its processing.

[0110] Thus, as a synthetic elastomeric latex, the latex may consist in particular of a synthetic diene elastomer already provided in the form of an emulsion (for example a butadiene / styrene copolymer SBR prepared in emulsion) or of a synthetic diene elastomer initially in solution (for example an SBR prepared in solution) emulsified in a mixture of an organic solvent and water, generally with the aid of a surfactant.

[0111] SBR latexes, particularly SBR prepared in emulsion ("ESBR") or SBR prepared in solution ("SSBR"), more particularly SBR prepared in emulsion, are particularly suitable for the present invention.

[0112] There are two main types of emulsion copolymerization processes for styrene and butadiene, one of which, or the hot process (carried out at temperatures close to 50°C), is suitable for preparing highly branched SBR, while the other, or the cold process (carried out at temperatures that can range from 15°C to 40°C), is able to obtain more linear SBR.

[0113] For a detailed description of the effectiveness of several emulsifiers that can be used in the thermal process (depending on the emulsifier content), reference can be made, for example, to two articles by CW Carr, IM Kolthoff, EJ Meehan, University of Minnesota, Minneapolis, Minn., which appeared in the Journal of Polymer Science, Vol. V, No. 2, pp. 201-206, 1950, and in the Journal of Polymer Science, Vol. VI, No. 1, pp. 73-81, 1951.

[0114] For comparative examples of the implementation of the cold process, reference can be made, for example, to the article 1 / 2 Industrial and Engineering Chemistry, 1948, Vol. 40, No. 5, pp. 932-937, EJ Vandenberg, GE Hulse, Hercules Powder Company, Wilmington, Del.+ and the reference article 1 / 2 Industrial and Engineering Chemistry, 1954, Vol. 46, No. 5, pp. 1065-1073, JR Miller, H.E. Diem, BF Goodrich Chemical Co., Akron, Ohio+.

[0115] In the case of SBR elastomers (ESBR or SSBR), use is especially made of SBR having an average styrene content, for example, between 20% and 35% by weight, or a high styrene content, for example, between 35% and 45%, a vinyl bond content of the butadiene portion between 10% and 70%, a trans-1,4-bond content (mol %) between 15% and 75% and a Tg between -10°C and -55°C; such SBR can advantageously be used in blends with BR having preferably greater than 90% (mol %) of cis-1,4-bonds.

[0116] It is noted that it is contemplated to use one or more natural rubber latexes as a blend, one or more synthetic rubber latexes as a blend, or a blend of one or more natural rubber latexes and one or more synthetic rubber latexes.

[0117] II. Filler

[0118] Suitable carbon blacks are all carbon blacks conventionally used in tires, in particular carbon blacks of the HAF, ISAF or SAF type (“tire-grade” blacks). Among the latter, mention is made more particularly of reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), such as N110, N121, N134, N220, N231, N234, N242, N293, N299, S315, N326, N330, M332, N339, N343, N347, N351, N358 or N375 blacks, or, depending on the intended application, of higher series such as N400, N539, N550, N582, N630, N642, N650, N683, N754, N762, N765, N774, N787, N907, N908, N990 and N991.

[0119] Mass balance carbon black or ISCC carbon black is also suitable, such as carbon black derived at least in part from non-traditional feedstocks such as tall oil, methane, or waste tire oil. ASTM-D6866 method for determining the radiocarbon content of an unknown sample ( 14 C) to a modern reference standard. The ratio is reported as a percentage in units of "pMC" (percent modern carbon). If the material being analyzed is a mixture of present-day radiocarbon and fossil carbon (fossil carbon is derived from petroleum, coal or natural gas sources), the resulting pMC value is directly related to the amount of biomass material present in the sample. The result provided by ASTM D6866 is the amount of biobased component "present" in the material - not the amount of biobased material "used" in the manufacturing process. In one embodiment, the carbon black has a modern carbon content as defined by ASTM D6866 of greater than one percent (1%). The carbon black is produced from a biobased feedstock before it is added to the masterbatch and / or rubber composition. In one embodiment, the carbon black is at least partially derived from a biobased feedstock and in a preferred embodiment is completely free of fossil carbon.

[0120] Also suitable as carbon black are carbon blacks which have been partially or completely covered with silica by post-treatment or which have been modified in situ with silica, such as, but not limited to, carbon blacks produced by Cabot Corporation under the name Ecoblack TM Fillers sold as "CRX 2000" or "CRX4000."

[0121] Various combinations of carbon blacks (having different particle sizes and / or other properties, including conventional petroleum blacks and bio-derived carbon blacks) can also be used in the disclosed rubber compositions. Representative examples of rubber-reinforced carbon blacks are, for example, but not limited to, reference to The Vanderbilt Rubber Handbook, 13th edition, 1990, pages 417 and 418, with their ASTM designations. Such rubber-reinforced carbon blacks can have, for example, iodine absorptions of 9 to 240 g / kg and DBP values ​​of 34 to 150 cc / 100 g.

[0122] The expression "inorganic filler" is understood here in a known manner to mean any inorganic or mineral filler, whatever its color and whatever its origin (natural or synthetic), also called "white filler", "transparent filler" or even "non-black filler", in contrast to carbon black, capable of reinforcing the rubber composition intended for use in the manufacture of tire treads alone, without the need for intermediate coupling agents, in other words, capable of replacing conventional tire-grade carbon blacks used for treads in its reinforcing effect. Such fillers are generally characterized by the presence of functional groups on their surface, in particular hydroxyl groups (—OH), and, in order to act as reinforcing fillers, require the use of a coupling agent or a coupling system in order to provide a stable chemical bond between the isoprene elastomer and the filler.

[0123] Such inorganic fillers can therefore be used with a coupling agent in order to be able to reinforce the rubber composition in which they are included. In addition to a coupling agent, they can also be used with a covering agent (which does not provide a bond between the filler and the elastomeric matrix) or without a coupling agent (in which case the inorganic filler does not play a reinforcing role).

[0124] The physical state in which the inorganic filler is present is not important, whether it is in the form of a powder, microbeads, granules, balls or any other suitable densified form. Of course, the expression "inorganic filler" is also understood to mean a mixture of various inorganic fillers, in particular silica, such as conventional silica, precipitated silica, treated silica and / or highly dispersible silica, and very high surface area HDS (BET nitrogen surface area> 250 m 2 / g) siliceous and / or aluminous fillers.

[0125] Siliceous mineral fillers, in particular silicon dioxide (SiO2), or aluminous mineral fillers, in particular aluminum oxide (Al2O3), are particularly suitable as inorganic fillers. The silicon dioxide used can be any silicon dioxide known to those skilled in the art, in particular one having a BET surface area and a CTAB specific surface area of ​​less than 450 m 2 / g, preferably 30 to 400m 2 / g of any precipitated or fumed silica. Highly dispersible precipitated silicas ("HDS") include, for example, Ultrasil 7000 and Ultrasil 7005 silicas from Evonik, Zeosil 1165MP, 1135MP, 1115 and 1200MP silicas from Rhodia, Hi-Sil EZ150G silica from PPG, Zeopol 8715, 8745 and 8755 silicas from Huber, or silicas with a high specific surface area as described in application WO 03 / 16837. Other suitable fillers include Premium SW, Zeosil 115, 125 and 200MP from Solvay.

[0126] When the composition of the invention is intended for use in tire treads having low rolling resistance, the inorganic filler used, especially if it is silica, preferably has a viscosity ranging from 45 to 400 m 2 / g, more preferably 60 to 300m 2 The BET surface area is between 1.17 and 1.17 g.

[0127] Preferably, inorganic fillers having an average size (by weight) between 20 and 300 nm, more preferably between 20 and 150 nm, are particularly suitable for use in the present invention. This average size is conventionally measured after the filler to be analyzed has been dispersed in water or an aqueous solution containing a surfactant by ultrasonic deagglomeration. For inorganic fillers such as silica, the measurement is performed using an X-ray detection centrifugal sedimentation instrument of the "XDC" ("X-ray Disc Centrifuge") type sold by Brookhaven Instruments according to the following procedure. A suspension of 3.2 g of the inorganic filler sample to be analyzed in 40 ml of water is produced by the action of a 1500 W ultrasonic probe (3 / 4 inch Vibracell sonicator sold by Bioblock) at 60% power (60% of the maximum position of the "output control") for 8 minutes; 15 ml of the suspension are introduced, after the ultrasonic treatment, into a disc rotating at speeds varying between 3000 and 6000 rpm (the speed is adjusted according to the average size of the filler: the smaller the size, the higher the speed); after 120 minutes of sedimentation, the weight distribution of the particle sizes and the average size by weight dw of the particles are calculated by the software of the "XDC" sedimentometer (dw=Σ(nidi5) / Σ(ni di4), where ni is the number of objects of size class or diameter di).

[0128] Preferably, the total filler content (carbon black and inorganic fillers such as silica) is between 1 and 200 phr, more preferably between 30 and 150 phr, even more preferably between 30 and 100 phr, the optimum value varying in a known manner according to the specific application targeted: for example, the desired reinforcement level on a bicycle tire is of course lower than that required for a tire capable of being driven at high speed in a sustained manner, such as a motorcycle tire, a passenger car or a utility vehicle such as a heavy vehicle.

[0129] According to a preferred embodiment of the invention, carbon black is used in a content varying from 1 to 100 phr, preferably from 30 to 80 phr, in the masterbatch and / or the rubber composition, and an inorganic filler, in particular silica, in a content varying from 5 to 50 phr. More particularly, the total filler of the composition comprises a content varying from 35 to 70 phr of carbon black and a content varying from 5 to 35 phr of inorganic filler, in particular silica. Even more preferably, the total filler comprises a content varying from 35 to 65 phr of carbon black and a content varying from 1 to 30 phr of inorganic filler, in particular silica.

[0130] III. Masterbatch-Rubber Composition

[0131] Advantageously, the masterbatches and compositions thus produced can be used in tire applications.

[0132] The rubber composition for tires based on a masterbatch and an inorganic filler according to the invention may also contain coupling agents and / or covering agents and a vulcanization system in a known manner.

[0133] In one embodiment, the rubber composition may include a silane coupling agent.In one embodiment, the response enhancing filler is silica, and the rubber composition may include a silane coupling agent.

[0134] The silane coupling agent can be any suitable silane coupling agent, such as bis(ω-trialkoxyalkylsilyl)polysulfide, ω-mercaptoalkyl-trialkoxysilane, or a combination thereof. In one example, the bis-(ω-trialkoxysilylalkyl)polysulfide has an average of about 2 to about 4 connected sulfur atoms in its polysulfide bridge. In another example, the bis-(ω-trialkoxysilylalkyl)polysulfide has an average of about 2 to about 2.6 connected sulfur atoms in its polysulfide bridge. In yet another example, the bis-(ω-trialkoxysilylalkyl)polysulfide has an average of about 3.3 to about 3.8 connected sulfur atoms in its polysulfide bridge. The alkyl group of the silylalkyl portion of the bis-(ω-trialkoxysilylalkyl)polysulfide can be a saturated C2-C6 alkyl group, such as a propyl group. Furthermore, at least one alkyl group of the trialkoxy moiety of the bis-(ω-trialkoxysilylalkyl) polysulfide may be an ethyl group, and the remaining alkyl groups of the trialkoxy moiety may independently be saturated C2-C 18 In another example, at least two alkyl groups of the trialkoxy portion of the bis-(ω-trialkoxysilylalkyl) polysulfide are ethyl groups, and the remaining alkyl groups of the trialkoxy portion are independently saturated C3-C 18 Alkyl. In one example, the bis-(ω-trialkoxysilylalkyl) polysulfide coupling agent is bis-3-(triethoxysilylpropyl) tetrasulfide ("TESPD"). In another example, the bis-(ω-trialkoxysilylalkyl) polysulfide coupling agent is bis-3-(triethoxysilylpropyl) tetrasulfide ("TESPT"). The ω-mercaptoalkyltrialkoxysilane can block its mercapto moiety to prevent the blocked mercapto moiety from being deblocked at elevated temperatures before pre-reacting with hydroxyl groups (e.g., silanol groups) contained on the precipitated silica aggregates. In one example, the blocked ω-mercaptoalkyl-trialkoxysilane is NXT or NXT-LoV available from GE Silicones of Tarrytown, NY.

[0135] Sulfur Curative

[0136] The rubber composition for tire components may preferably additionally contain conventional sulfur-containing organosilicon compounds. Examples of suitable sulfur-containing organosilicon compounds have the formula:

[0137] Z-Alk-S n -Alk-Z I

[0138] Where Z is selected from

[0139]

[0140] where R 6is an alkyl group of 1 to 4 carbon atoms, a cyclohexyl group or a phenyl group; R 7 is an alkoxy group of 1 to 8 carbon atoms or a cycloalkoxy group of 5 to 8 carbon atoms; Alk is a divalent hydrocarbon group of 1 to 18 carbon atoms and n is an integer of 2 to 8.

[0141] Specific examples of sulfur-containing organosilicon compounds that can be used in the present invention include: 3,3′-bis(trimethoxysilylpropyl) disulfide, 3,3′-bis(triethoxysilylpropyl) disulfide, 3,3′-bis(triethoxysilylpropyl) tetrasulfide, 3,3′-bis(triethoxysilylpropyl) octasulfide, 3,3′-bis(trimethoxysilylpropyl) tetrasulfide, 2,2′-bis(triethoxysilylethyl) tetrasulfide, 3,3′-bis(trimethoxysilylpropyl) trisulfide, 3,3′-bis(triethoxysilylpropyl) trisulfide, 3,3′-bis(tributoxysilylpropyl) disulfide, 3,3′-bis(tributoxysilylpropyl) -bis(trimethoxysilylpropyl) hexasulfide, 3,3′-bis(trimethoxysilylpropyl) octasulfide, 3,3′-bis(trioctyloxysilylpropyl) tetrasulfide, 3,3′-bis(trihexyloxysilylpropyl) disulfide, 3,3′-bis(tri-2″-ethylhexyloxysilylpropyl) trisulfide, 3,3′-bis(triisooctyloxysilylpropyl) tetrasulfide, 3,3′-bis(tri-tert-butoxysilylpropyl) disulfide, 2,2′-bis(methoxydiethoxysilylethyl) tetrasulfide, 2,2′-bis(tripropoxysilylethyl) pentasulfide, 3,3′-bis(tricyclohexyloxysilylpropyl) tetrasulfide 2,2′-bis(tri-2″-methylcyclohexyloxysilylethyl) tetrasulfide, bis(trimethoxysilylmethyl) tetrasulfide, 3-methoxyethoxypropoxysilyl 3′-diethoxybutoxy-silylpropyl tetrasulfide, 2,2′-bis(dimethylmethoxysilylethyl) disulfide, 2,2′-bis(dimethylsec-butoxysilylethyl) trisulfide, 3,3′-bis(methylbutylethoxysilylpropyl) tetrasulfide, 3,3′-bis(di-tert-butylmethoxysilylpropyl) tetrasulfide, 2,2′-bis(phenylmethylmethoxysilylethyl) trisulfide Sulfide, 3,3′-bis(diphenylisopropoxysilylpropyl) tetrasulfide, 3,3′-bis(diphenylcyclohexyloxysilylpropyl) disulfide, 3,3′-bis(dimethylethylmercaptosilylpropyl) tetrasulfide, 2,2′-bis(methyldimethoxysilylethyl) trisulfide, 2,2′-bis(methylethoxypropoxysilylethyl) tetrasulfide, 3,3′-bis(diethylmethoxysilylpropyl) tetrasulfide, 3,3′-bis(ethyldi-sec-butoxysilylpropyl) disulfide, 3,3′-bis(propyldiethoxysilylpropyl) disulfide, 3,3′-bis(butyldimethoxysilylpropyl) trisulfide, 3,3′-Bis(phenyldimethoxysilylpropyl)tetrasulfide, 3-phenylethoxybutoxysilyl 3′-trimethoxysilylpropyl tetrasulfide, 4,4′-bis(trimethoxysilylbutyl)tetrasulfide, 6,6′-bis(triethoxysilylhexyl)tetrasulfide, 12,12′-bis(triisopropoxysilyldodecyl)disulfide, 18,18′-bis(trimethoxysilyloctadecyl)tetrasulfide, 18, 18′-Bis(tripropoxysilyloctadecenyl) tetrasulfide, 4,4′-bis(trimethoxysilyl-buten-2-yl) tetrasulfide, 4,4′-bis(trimethoxysilylcyclohexylene) tetrasulfide, 5,5′-bis(dimethoxymethylsilylpentyl) trisulfide, 3,3′-bis(trimethoxysilyl-2-methylpropyl) tetrasulfide, 3,3′-bis(dimethoxyphenylsilyl-2-methylpropyl) disulfide.

[0142] The preferred sulfur-containing organosilicon compound is 3,3′-bis(trimethoxy or triethoxysilylpropyl)sulfide. The most preferred compounds are 3,3′-bis(triethoxysilylpropyl)disulfide and 3,3′-bis(triethoxysilylpropyl)tetrasulfide. Therefore, with respect to formula I, Z is preferably

[0143]

[0144] where R 7 is an alkoxy group of 2 to 4 carbon atoms, with 2 carbon atoms being particularly preferred; alk is a divalent hydrocarbon group of 2 to 4 carbon atoms, with 3 carbon atoms being particularly preferred; and n is an integer of 2 to 5, with 2 to 4 being particularly preferred.

[0145] In another embodiment, suitable sulfur-containing organosilicon compounds include compounds disclosed in U.S. Patent No. 6,608,125. In one embodiment, the sulfur-containing organosilicon compound includes 3-(octanoylthio)-1-propyltriethoxysilane, CH3(CH2)6C(=O)-S-CH2CH2CH2Si(OCH2CH3)3, which can be used as NXT TM Purchased from Momentive Performance Materials.

[0146] In another embodiment, suitable sulfur-containing organosilicon compounds include compounds disclosed in U.S. Publication No. 2006 / 0041063, the disclosure of which is incorporated herein by reference in its entirety. In one embodiment, the sulfur-containing organosilicon compound includes the reaction product of a hydrocarbon diol (e.g., 2-methyl-1,3-propanediol) and S-[3-(triethoxysilyl)propyl]thiooctanoate. In one embodiment, the sulfur-containing organosilicon compound is NXT-Z from Momentive Performance Materials. TM .

[0147] In another embodiment, suitable sulfur-containing organosilicon compounds include those disclosed in US Patent Publication No. 2003 / 0130535, which is incorporated herein by reference in its entirety.In one embodiment, the sulfur-containing organosilicon compound is Si-363 from Degussa.

[0148] The amount of the sulfur-containing organosilicon compound of formula I in the rubber composition varies with the amount of other additives used. The amount of the compound of formula I is 0.5 to 20 phr. The amount is preferably 1 to 10 phr.

[0149] According to some embodiments of the rubber composition of the present invention, the content of the coupling agent is preferably 2 / g of inorganic filler, more preferably in a CTAB surface area of ​​160m 2 / g of inorganic filler 4 wt% to 10 wt%; and / or the content of the covering agent is preferably in the range of 160m 2 / g of inorganic filler, more preferably in a CTAB surface area of ​​160m 2 The content of the coupling agent can be adjusted according to the specific surface area of ​​the filler.

[0150] It will be understood by those skilled in the art that fillers of another nature, in particular fillers of an organic nature, may be used as equivalent fillers to the inorganic fillers described in this section, provided that such fillers are covered with an inorganic layer such as silica, or contain functional sites on their surface, in particular hydroxyl groups, which require the use of a coupling agent to form a link between the filler and the elastomer.

[0151] IV. Mixing

[0152] The rubber compositions according to the invention may also contain all or some of the standard additives conventionally used in elastomeric compositions intended for the manufacture of tires, in particular treads, such as plasticizers or extender oils (whether the latter are of aromatic or non-aromatic nature), pigments, protective agents such as anti-ozon waxes, chemical antiozonants, antioxidants, anti-fatigue agents, reinforcing resins, methylene acceptors (for example novolac resins) or methylene donors (for example HMT or H3M), crosslinking systems based on sulfur or sulfur donors, and / or on peroxides and / or on bismaleimides, as described, for example, in application WO 02 / 10269, and vulcanization accelerators.

[0153] In a contemplated embodiment, these compositions may comprise, as preferred non-aromatic or very weakly aromatic plasticizer, at least one compound chosen from naphthenic oils, paraffinic oils, MES oils, TDAE oils, glycerides (in particular trioleates), hydrocarbon-based plasticizing resins exhibiting a high Tg, preferably above 30° C., and mixtures of these compounds.

[0154] It should be noted that it is also possible to envisage producing a masterbatch according to the invention by introducing additives as described above (oils, antioxidants, coupling agents, covering agents, etc.) before the drying phase in which the masterbatch is produced, in particular in the liquid phase.

[0155] V. Production of Rubber Compositions and Masterbatches

[0156] The rubber composition of the present invention is manufactured in a suitable mixer using two sequential preparation stages according to a general procedure well known to those skilled in the art: a first stage (sometimes called a "non-productive" stage) of thermomechanical processing or kneading at a high temperature (maximum between 130° C. and 200° C., preferably at a maximum temperature between 145° C. and 185° C.) of at least one pass, followed by a second stage (sometimes called a "productive" stage) of mechanical processing at a lower temperature (generally below 120° C., for example between 60° C. and 100° C.), during which a crosslinking or vulcanization system is incorporated. Embodiments are envisioned to include one or more non-productive stages or passes.

[0157] According to one embodiment of the invention, all the essential ingredients of the composition of the invention, with the exception of the vulcanization / crosslinking system, in particular the masterbatch comprising carbon black and inorganic fillers, and, where appropriate, coupling agents, are intimately incorporated into the diene elastomer by kneading during a so-called non-productive first stage, that is to say, at least these various essential ingredients are introduced into a mixer in one or more steps and thermomechanically kneaded until a maximum temperature of between 130° C. and 200° C., preferably between 145° C. and 185° C., is reached.

[0158] According to another embodiment of the invention, all the essential ingredients of the composition of the invention, including at least one component of the crosslinking / vulcanization system, in particular a masterbatch containing carbon black and an inorganic filler, and, where appropriate, a coupling agent, are intimately incorporated into the diene elastomer by kneading during a so-called non-productive first stage, that is to say, at least these various essential ingredients are introduced into a mixer in one or more steps and thermomechanically kneaded until a maximum temperature of between 130° C. and 200° C., preferably between 145° C. and 185° C., is reached.

[0159] According to another embodiment of the invention, at least one essential component of the composition of the invention, optionally including at least one component of the crosslinking / vulcanization system, in particular a masterbatch containing carbon black and an inorganic filler, and where appropriate a coupling agent, is intimately incorporated into the diene elastomer by kneading during a so-called non-productive first stage. That is, at least one essential component is introduced into a mixer in one or more steps and thermomechanically kneaded until a maximum temperature of between 130° C. and 200° C., preferably between 145° C. and 185° C., is reached to produce a first non-productive compound or composition. During another non-productive stage (or second non-productive stage), at least a second essential component of the rubber composition of the invention is incorporated into the first non-productive compound by any method known to those skilled in the art or by kneading. Said at least second essential component is introduced into a mixer in one or more steps and thermomechanically kneaded until a maximum temperature of between 130° C. and 200° C. is reached to produce a second non-productive compound.

[0160] According to one preferred embodiment of the invention, the inorganic filler is incorporated into the diene elastomer and the carbon black that have been prepared beforehand in the form of a first masterbatch.

[0161] Preferably, this first masterbatch is produced in the “liquid” phase. To this end, the process involves a diene elastomer in latex form, in the form of water-dispersed elastomeric particles, and an aqueous dispersion of carbon black, that is, a filler dispersed in water, generally called a “slurry”. More preferably, the process steps described in document US Pat. No. 6,048,923 are followed, consisting in particular in incorporating into the compounding zone of a coagulant reactor a continuous flow of a first fluid consisting of the elastomer latex, into which a second continuous flow of a second fluid consisting of an aqueous dispersion of carbon black is incorporated under pressure to form a mixture with the elastomer latex, the compounding of the two fluids being sufficiently vigorous to enable almost complete coagulation of the elastomer latex with the carbon black before the outlet orifice of the coagulant reactor, and then drying the resulting coagulant.

[0162] In particular, the incorporation of the inorganic filler can be carried out simultaneously with the introduction of the other ingredients (especially the diene elastomer, either alone or in the form of a first masterbatch) into the mixer, and advantageously, this incorporation can be staggered in time by a few tens of seconds to a few minutes.

[0163] For example, the (non-productive) first stage is carried out in a single thermomechanical stage, during which at least one essential ingredient (if appropriate in the form of a masterbatch as described above), an optional additional coating agent or processing aid, and various other additives (optionally including components of the vulcanization system) are introduced into a suitable mixer, such as a standard internal mixer. The total duration of kneading in this non-productive stage is preferably between 1 and 15 minutes. After cooling the mixture thus obtained during the final non-productive stage, the remaining active ingredients of the vulcanization system are then incorporated at low temperature, generally in an internal mixer; all the ingredients are then mixed (productive stage) for a few minutes, for example between 2 and 15 minutes. In one embodiment, an additional diene elastomer may also be incorporated into the final non-productive compound during the productive stage, which comprises a step of kneading all the materials to a maximum temperature of less than 120° C. In one embodiment, the additional diene elastomer may be identical to or different from the at least one diene elastomer. In a preferred embodiment, the additional diene elastomer serves to dilute the amount of filler contained in the original masterbatch. Therefore, the additional diene elastomer is incorporated into the compound in an amount that reduces the carbon black in the masterbatch to a predetermined level in the rubber composition. It will be readily understood by those skilled in the art that the rubber composition is compounded by methods well known in the art of rubber compounding, such as mixing various sulfur-vulcanizable component rubbers with various conventional additive materials, such as sulfur donors, vulcanizing aids (such as activators and retarders) and processing additives, fillers, pigments, fatty acids, zinc oxide, waxes, antioxidants and antiozonants with peptizers. The crosslinking system is preferably a vulcanization system, i.e., a system based on sulfur (or based on sulfur donors) and based on a primary vulcanization accelerator. Representative examples of sulfur donors include elemental sulfur (free sulfur), disulfide amines, polymeric polysulfides, and sulfur olefin adducts. Preferably, the sulfur vulcanizing agent is elemental sulfur. The sulfur vulcanizing agent can be used in an amount of 0.01 to 12 phr, particularly between 1 and 10 phr. As described later, various known auxiliary vulcanization accelerators or vulcanization activators are added to this basic vulcanization system, such as zinc oxide, stearic acid or equivalent compounds, or guanidine derivatives (particularly diphenylguanidine), which are incorporated during the non-productive first stage and / or during the productive stage. As known to those skilled in the art, the above-mentioned additives are selected according to the intended use of the sulfur-vulcanizable and sulfur-vulcanized materials (rubbers) and are generally used in conventional amounts.

[0164] Typical amounts of antioxidants comprise about 1 to about 5 phr. Representative antioxidants can be, for example, diphenyl-p-phenylenediamine, for example The Vanderbilt Rubber Handbook (1978), pp. 344-346. If fatty acids (which may include stearic acid) are used, typical amounts comprise from about 0.1 to about 5 phr. Typical amounts of waxes comprise from about 1 to about 5 phr. Microcrystalline wax is commonly used. Typical amounts of peptizers comprise from about 0.1 to about 1 phr. Typical peptizers include, for example, pentachlorothiophenol and dibenzamidodiphenyl disulfide.

[0165] Accelerators are used to control the time and / or temperature required for vulcanization and improve the properties of the vulcanized rubber. In one embodiment, a single accelerator system, i.e., a primary accelerator, can be used. The primary accelerator can be used in an amount of about 0.1 to about 10 phr, more preferably in an amount of 0.5 to 5.0 phr. In another embodiment, a combination of a primary accelerator and an auxiliary accelerator can be used, and the auxiliary accelerator is used in a smaller amount to activate and improve the properties of the vulcanized rubber. The combination of these accelerators may be expected to produce a synergistic effect on the final properties and slightly better than the effect produced by using any accelerator alone. In addition, an after-effect accelerator that is not affected by normal processing temperature but produces satisfactory vulcanization at ordinary vulcanization temperatures can be used. Vulcanization delay agents may also be used. Accelerators that can be used for the appropriate type of the present invention are amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates, and xanthates. Preferably, the primary accelerator is a sulfenamide. If an auxiliary accelerator is used, the auxiliary accelerator is preferably guanidine, dithiocarbamate, or a thiuram compound.

[0166] The final composition thus obtained is then calendered, for example, into the form of a sheet or plate, or extruded into the form of a rubber profile element, which can be used, for example, as a tread for tires of passenger cars, heavy vehicles, and the like.

[0167] In light of the description provided herein, it is possible to make changes to the present invention. Although certain representative embodiments and details have been shown for the purpose of illustrating the present invention, it will be apparent to those skilled in the art that various changes and modifications may be made thereto without departing from the scope of the present invention. It will therefore be understood that changes may be made to the specific embodiments described within the full intended scope of the present invention as defined by the following claims.

Claims

1. A method for preparing a rubber composition based on at least one diene elastomer, a filler comprising at least carbon black and an inorganic filler, and a crosslinking system, wherein the content of the inorganic filler is less than or equal to 50 parts by weight per 100 parts of elastomer, the method comprising: A first masterbatch of diene elastomer and carbon black is prepared, comprising: feeding a continuous flow of diene elastomer latex into a mixing zone of a coagulant reactor, said coagulant reactor defining an elongated coagulant zone extending between said mixing zone and an outlet, and feeding a continuous stream of a fluid containing a filler comprising carbon black under pressure into a mixing zone of a coagulant reactor to form a coagulant mixture, drying the coagulant obtained above to recover the first masterbatch; incorporating the inorganic filler and the other ingredients of the composition, except the crosslinking system, into the first masterbatch obtained above by thermomechanically kneading all the materials until a maximum temperature of between 130° C. and 200° C. is reached in a mixer, so as to produce a non-productive compound; Cooling the combined mixture to a temperature below 100°C before incorporating the crosslinking system; The crosslinking system and an additional diene elastomer, which is identical or different from the at least one diene elastomer, are subsequently incorporated into the non-productive compound and all materials are kneaded until a maximum temperature of less than 120° C. 2 . The process according to claim 1 , wherein the additional diene elastomer is incorporated into the non-productive compound in an amount that reduces the carbon black in the masterbatch to a predetermined level in the rubber composition.

3. A method for preparing a rubber composition based on at least one diene elastomer, a filler comprising at least carbon black and an inorganic filler, and a crosslinking system, wherein the content of inorganic filler is less than or equal to 50 parts by weight per 100 parts of elastomer, the method comprising: A first masterbatch of diene elastomer and carbon black is prepared, comprising: feeding a continuous flow of diene elastomer latex into a mixing zone of a coagulant reactor, said coagulant reactor defining an elongated coagulant zone extending between said mixing zone and an outlet, and feeding a continuous stream of a fluid containing a filler containing carbon black under pressure into a mixing zone of a coagulant reactor to form a coagulant mixture, drying the coagulant obtained above to recover the first masterbatch; incorporating the inorganic filler and the other ingredients of the composition, except the crosslinking system, into the first masterbatch obtained above by thermomechanically kneading all the materials until a maximum temperature of between 130° C. and 200° C. is reached in a mixer, so as to produce a first non-productive compound; cooling the first non-productive compound to a temperature below 100° C.; incorporating at least one additional ingredient of the composition into the first non-productive compound to produce at least a second non-productive compound; and The combined mixture is cooled to a temperature below 100°C, All or part of the crosslinking system is then incorporated into the at least second non-productive compound and all materials are kneaded until a maximum temperature of less than 120°C. 4 . The process according to claim 3 , wherein the at least one additional component is an additional diene elastomer, identical to or different from the at least one diene elastomer. 5 . The method according to claim 4 , wherein the additional diene elastomer is incorporated into the first non-productive compound in an amount that reduces the carbon black in the masterbatch to a predetermined level in the rubber composition.

6. The method according to claim 3, wherein the at least one additional ingredient is part of a crosslinking system, the at least one additional ingredient being selected from the group consisting of sulfur, sulfur donors, accelerators and vulcanization activators. 7 . The process according to claim 1 , wherein the diene elastomer is chosen from polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymers, isoprene copolymers and blends of these elastomers.

8. The process according to claim 7, wherein the diene elastomer is natural rubber.

9. The process according to claim 3, wherein the diene elastomer is chosen from polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymers, isoprene copolymers and blends of these elastomers. 10 . The process according to claim 9 , wherein the diene elastomer is natural rubber.

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