rubber compound and vehicle tires

Abstract

Containing sulfur-crosslinkable rubber compound - 20 to 70 phr of at least one functionalized styrene-butadiene copolymer A, wherein the functionalized styrene-butadiene copolymer is functionalized at at least one end of each polymer chain with an amino group-containing alkoxysilyl group and at least one further alkoxysilyl group(s) and / or at least one further amino group-containing alkoxysilyl group(s), and - 10 to 50 phr of at least one emulsion-polymerized styrene-butadiene rubber B, which in the unvulcanized state has a styrene content of 5 to 30 wt.%, and a vinyl content based on the butadiene content of 5 to 70 wt.%, and - 20 to 300 phr silica and / or carbon black.

Description

[0001] The invention relates to a sulfur-crosslinkable rubber compound, in particular for treads of vehicle tires, and to a vehicle tire.

[0002] The rubber composition of the tread largely determines the driving characteristics of a vehicle tire, especially a pneumatic tire. Similarly, the rubber compounds used in belts, hoses, and straps, particularly in areas subject to high mechanical stress, are essential for the stability and durability of these rubber products. Therefore, very high demands are placed on these rubber compounds used in vehicle tires, belts, and hoses.

[0003] The partial or complete replacement of carbon black with silica in rubber compounds has, for example, improved the overall driving characteristics of tires in recent years. However, the well-known conflicts of objectives regarding opposing tire properties still exist, even with silica-containing tread compounds. Thus, improvements in wet grip and dry braking performance generally still result in a deterioration of rolling resistance, winter performance, and wear characteristics. These properties are also important quality criteria for technical rubber products such as belts, straps, and hoses.

[0004] Particularly with vehicle tires, numerous attempts have been made to positively influence tire properties by varying the polymer components, fillers, and other additives, especially in the tread compound. The focus here is primarily on rolling resistance and abrasion. It must be considered that an improvement in one tire property often leads to a deterioration of another. For example, within a given compound system, several well-known methods exist to optimize rolling resistance. These include lowering the glass transition temperature of the rubber compound, reducing the filler content, and changing the polymer system.All of the above measures inevitably lead to a deterioration of at least one of the other tire properties, such as abrasion behavior and / or wet grip and / or tearing properties and / or handling behavior of the given compound.

[0005] To optimize the rolling resistance behavior or to optimize various other properties of rubber compounds relevant for use in tires without deteriorating the rolling resistance behavior, it is known to functionalize the diene rubber used in such a way that it bonds to the filler(s).

[0006] For example, EP 2357211 A1 discloses a rubber compound containing at least one aliphatic and / or aromatic hydrocarbon resin, at least one filler, and at least one functionalized diene monomer rubber, the functionalization of which is present along the polymer chain and / or at the end and enables bonding to fillers. Hydroxyl groups are disclosed in Table 1 as functionalizations for bonding the polymers to silica. As the examples show, 20 phr of a hydrocarbon resin are necessary as a plasticizer to achieve the desired improvement in abrasion resistance and wet grip, although this negatively impacts rolling resistance.

[0007] EP 0806452 A1 also describes a rubber mixture containing a functionalized diene rubber which carries, among other things, hydroxy groups as functional groups for bonding to silica.

[0008] EP 1457501 A1 discloses a functionalized styrene-butadiene copolymer, which, per styrene-butadiene copolymer chain, contains a primary amino group and an alkoxysilyl group as functional groups. EP 1457501 A1 also discloses rubber compounds containing this styrene-butadiene copolymer, as well as tires whose treads are made of this rubber compound. The tires are said to be characterized by a good balance between abrasion resistance, durability, hysteresis loss, and wet grip.

[0009] EP 1837370 A1 also discloses a rubber compound containing such a functionalized styrene-butadiene copolymer, which has a primary amino group and an alkoxysilyl group as functional groups on each styrene-butadiene copolymer chain. In combination with a specific type of carbon black, this rubber compound exhibits improved tire properties such as wet braking, abrasion resistance, and rolling resistance.

[0010] EP 2098384 B1 also discloses a rubber compound containing a solution-polymerized styrene-butadiene copolymer, which carries an amino group and an alkoxysilyl group (amino-siloxane group) as functional groups. This results in improvements in dry braking, handling, wet braking, and abrasion resistance, although the effect on rolling resistance is not disclosed due to the conflict of objectives.

[0011] US patent 20070185267 A1 discloses a rubber compound which may contain a conjugated diene-based copolymer which may be functionalized with an alkoxysilyl group and two amino groups.

[0012] DE 11 2011 101 778 T5 discloses a rubber composition comprising a diene rubber containing three types of rubber (E-SBR, modified S-SBR and natural rubber (NR)) in a total amount of 80 wt.% or more; and a filler material in an amount of 100 to 140 parts by weight, based on 100 parts by weight of the diene rubber, wherein the filler material contains 70 wt.% or more silicon dioxide.

[0013] German patent DE 102013105193 A1 describes a rubber compound characterized by a further improvement in rolling resistance, while the other physical properties remain at the same level, and in particular the abrasion resistance and / or wet grip properties are also further optimized. For this purpose, the rubber compound contains functionalized styrene-butadiene copolymer, which is functionalized at at least one end of each polymer chain with an amino-group-containing alkoxysilyl group and at least one further amino group(s) and / or at least one further alkoxysilyl group(s) and / or at least one further amino-group-containing alkoxysilyl group(s).

[0014] Based on the aforementioned prior art, the present invention is based on the objective of providing a sulfur-crosslinkable rubber compound, in particular for vehicle tires, belts, straps and hoses, whose vulcanizate exhibits an improvement compared to the prior art in the conflict of objectives between rolling resistance, wet grip and the predictors for handling behavior, especially when the rubber compound is used in vehicle tires.

[0015] This task is solved by a sulfur-crosslinkable rubber compound containing: - 20 to 70 phr of at least one functionalized styrene-butadiene copolymer A, wherein the functionalized styrene-butadiene copolymer is functionalized at at least one end of each polymer chain with an amino group-containing alkoxysilyl group and at least one further alkoxysilyl group(s) and / or at least one further amino group-containing alkoxysilyl group(s), and - 10 to 50 phr of at least one emulsion-polymerized styrene-butadiene rubber B, which in the unvulcanized state has a styrene content of 5 to 30 wt.%, and a vinyl content based on the butadiene content of 5 to 70 wt.%, and - 20 to 300 phr silica and / or carbon black.

[0016] Surprisingly, it was found that the combination of at least one functionalized styrene-butadiene copolymer (A) with the above-mentioned features with at least one emulsion-polymerized styrene-butadiene rubber (B) (ESBR) and 20 to 300 phr silica and / or carbon black in the rubber mixture according to the invention results in an optimization in the conflict of objectives between rolling resistance behavior, wet grip and the handling predictors.

[0017] Another object of the present invention is a vehicle tire comprising at least one component, in particular at least the tread, at least one vulcanizate of at least one sulfur-curable rubber compound with the aforementioned features. In the case of treads with a cap / base construction, the cap is preferably at least one component.

[0018] Vehicle tires containing the rubber compound according to the invention, at least in the tread, exhibit an improvement in the conflict of objectives between handling behavior, wet braking and rolling resistance.

[0019] Within the scope of the present invention, the term "vehicle tires" refers to all vehicle tires known to those skilled in the art, in particular pneumatic vehicle tires and solid rubber tires, including tires for industrial and construction vehicles, truck, car and two-wheeler tires.

[0020] The rubber compound according to the invention is also suitable for other components of vehicle tires, such as, in particular, the sidewall, horn profile, and inner tire components.

[0021] The rubber compound according to the invention is also suitable for other technical rubber articles, such as bellows, conveyor belts, air springs, belts, straps or hoses, as well as shoe soles, and is particularly suitable for conveyor belts due to its requirements profile.

[0022] The components of the sulfur-curable rubber compound according to the invention are described in more detail below. All descriptions also apply to the vehicle tire according to the invention, which incorporates the rubber compound according to the invention in at least one component.

[0023] The unit phr (parts per hundred parts of rubber by weight) used in this document is the standard unit of measurement for compound formulations in the rubber industry. The dosage of the individual substances by weight is based on 100 parts by weight of the total mass of all high-molecular-weight (average weight Mw of the molecular weight according to GPC from 250,000 to 5,000,000 g / mol) and therefore solid rubbers present in the mixture.

[0024] In the context of the present invention, the term “functionalized styrene-butadiene copolymer” means that the degree of functionalization of the total amount of styrene-butadiene copolymer is 30 to 100 mol%, i.e., that 30 to 100 mol%, preferably 70 to 100 mol% of the polymer chains are functionalized.

[0025] Essential to the invention is that the functionalized styrene-butadiene copolymer is functionalized at at least one end of each polymer chain with an amino-group-containing alkoxysilyl group and at least one further alkoxysilyl group(s) and / or at least one further amino-group-containing alkoxysilyl group(s). Thus, in addition to the necessarily present amino-group-containing alkoxysilyl group, at least one further functional group is attached to the end of the functionalized styrene-butadiene copolymer, which can interact, in particular, with silica.

[0026] All possible combinations of the aforementioned functional groups are conceivable. According to a preferred embodiment of the invention, in addition to the necessarily present amino-group-containing alkoxysilyl group, a further group selected from the group consisting of alkoxysilyl groups and amino-group-containing alkoxysilyl groups is attached to the chain end of each polymer chain of the functionalized styrene-butadiene rubber.

[0027] According to a further preferred embodiment of the invention, in addition to the necessarily present amino group-containing alkoxysilyl group, two further groups selected from alkoxysilyl groups and amino group-containing alkoxysilyl groups are linked to the chain end of each polymer chain of the functionalized styrene-butadiene rubber.

[0028] The functional groups of the functionalized styrene-butadiene copolymer can therefore be amino-group-containing alkoxysilyl group(s) and alkoxysilyl group(s). All amino groups of the functionalized styrene-butadiene copolymer can be attached to the end of the polymer chain with or without a spacer. Attachment with a spacer means that there is no direct bond between the carbon atom of the polymer chain end and the nitrogen atom of the amino group, but rather a group of one or more atoms is positioned between them. For example, an organic group that also carries the alkoxysilyl group could act as a spacer between the polymer chain end and the amino group.

[0029] The amino group-containing alkoxysilyl group(s) and the alkoxysilyl group(s) can also carry protecting groups.

[0030] Such functionalized styrene-butadiene copolymers are obtained by the following process: - Anionic polymerization of styrene and butadiene monomers to form a styrene-butadiene copolymer chain using an alkali or alkaline earth metal and - Reaction of the living end of the polymer chain, activated via alkali or alkaline earth metal, with an alkoxysilane, wherein at least one alkoxysilyl group of the alkoxysilane is protected by a protecting group containing amino groups, and - Reaction of the alkoxysilyl-functionalized polymer chain with another alkoxysilane to form a polymer chain functionalized with an amino group-containing alkoxysilyl group and at least one other alkoxysilyl group.

[0031] In this manufacturing process of the functionalized styrene-butadiene copolymer, the additional alkoxysilyl group can, for example, also bear an amino-group-containing protecting group, so that the polymer in this case is functionalized with two amino-group-containing alkoxysilyl groups. The amino groups can also bear protecting groups.

[0032] The functionalized styrene-butadiene copolymer A can be solution-polymerized or emulsion-polymerized. Preferably, it is a solution-polymerized styrene-butadiene copolymer (SSBR).

[0033] Within the scope of the present invention, the functionalized styrene-butadiene copolymer is also referred to as "functionalized styrene-butadiene rubber A". The copolymer or rubber mentioned is a diene rubber.

[0034] The functionalized styrene-butadiene copolymer A preferably has a weight average Mw of the molecular weight according to GPC of 300000 to 500000 g / mol, particularly preferably 300000 to 400000 g / mol, and can therefore also be described as a rubber that is solid at least at room temperature.

[0035] The functionalized styrene-butadiene copolymer A, in its unvulcanized state, preferably has a styrene content of 5 to 45 wt.%, particularly preferably a styrene content of 5 to 30 wt.%, and a vinyl content, based on the butadiene content, of 5 to 80 wt.%, particularly preferably a vinyl content of 10 to 70 wt.%. The glass transition temperature T gThe temperature of the functionalized styrene-butadiene copolymer in the unvulcanized state is preferably -10 °C to -80 °C, particularly preferably -15 °C to -70 °C. According to a preferred embodiment of the invention, the functionalized styrene-butadiene copolymer A preferably has a styrene content of 5 to 15 wt.% and a vinyl content of 30 to 50 wt.%, as well as a T g from -50 °C to -70 °C. With such a preferred and in particular especially preferred microstructure of the functionalized styrene-butadiene copolymer, advantages can be achieved in the rubber compounds according to the invention compared to the prior art with regard to the conflict of objectives between rolling resistance behavior and wet grip as well as the handling predictors.

[0036] The determination of the styrene content and the vinyl content of the polymers discussed within the scope of the present invention is carried out by means of 13C-NMR (solvent deuterochloroform CDCl3; NMR: nuclear magnetic resonance) and comparison with data from infrared spectrometry (IR; Nicolet FT-IR spectrometer, KBr window 25 mm diameter x 5 mm, 80 mg sample in 5 mL 1,2-dichlorobenzene). Determination of the glass transition temperature (T g ) is carried out using Dynamic Differential Calorimetry (DSC according to DIN 53765: 1994-03 or ISO 11357-2: 1999-03, calibrated DSC with low-temperature device, calibration according to device type and manufacturer's specifications, sample in aluminum crucible with aluminum lid, cooling to temperatures lower than -120 °C at 10 °C / min).

[0037] The functionalized styrene-butadiene copolymer (A) is present in the rubber mixture according to the invention in amounts of 20 to 70 phr, preferably 30 to 60 phr, and particularly preferably 40 to 60 phr. In combination, the rubber mixture according to the invention contains 10 to 50 phr of at least one emulsion-polymerized styrene-butadiene rubber (B), preferably 20 to 50 phr, and particularly preferably 20 to 40 phr of at least one ESBR (B).

[0038] The emulsion-polymerized styrene-butadiene rubber can be any type known to those skilled in the art. The at least one ESBR, in its unvulcanized state, has a styrene content of 5 to 30 wt.%, most preferably 10 to 30 wt.%, and a vinyl content, based on the butadiene content, of 5 to 70 wt.%, most preferably 5 to 50 wt.%, most preferably 5 to 30 wt.%, wherein the methods mentioned above apply to the determination of these parameters.

[0039] In particular, with an ESBR of the most preferred embodiments with regard to styrene content and vinyl content, in combination with the aforementioned functionalized SBR (A) in the rubber compound according to the invention, an optimization in the conflict of objectives between rolling resistance behavior, wet grip and the handling predictors is achieved.

[0040] Emulsion-polymerized styrene-butadiene rubber can be functionalized. However, unfunctionalized ESBR is preferred. Such types are relatively inexpensive and satisfactorily solve the underlying technical problem.

[0041] According to a preferred embodiment of the invention, the sulfur-crosslinkable rubber compound contains at least one further diene rubber.

[0042] Diene rubbers are rubbers that are formed by polymerization or copolymerization of dienes and / or cycloalkenes and thus have C=C double bonds either in the main chain or in the side groups.

[0043] The other diene rubber can be natural polyisoprene and / or synthetic polyisoprene and / or epoxidized polyisoprene and / or butadiene rubber (BR, polybutadiene) and / or styrene-isoprene rubber and / or halobutyl rubber and / or polynorbornene and / or isoprene-isobutylene copolymer and / or ethylene-propylene diene rubber and / or nitrile rubber and / or chloroprene rubber and / or acrylate rubber and / or fluorocarbon rubber and / or silicone rubber and / or polysulfide rubber and / or epichlorohydrin rubber and / or styrene-isoprene-butadiene terpolymer and / or hydrogenated acrylonitrile butadiene rubber and / or hydrogenated trade in styrene-butadiene rubber and / or butadiene-isoprene rubber.In particular, nitrile rubber, hydrogenated acrylonitrile butadiene rubber, chloroprene rubber, butyl rubber, halobutyl rubber or ethylene propylene diene rubber are used in the manufacture of technical rubber articles, such as belts, straps and hoses, and / or shoe soles.

[0044] Preferred is the further diene rubber selected from the group consisting of natural polyisoprene, synthetic polyisoprene and butadiene rubber.

[0045] According to a preferred embodiment of the invention, the further diene rubber is selected from the group consisting of natural polyisoprene and synthetic polyisoprene. Natural polyisoprene is particularly preferred as the further diene rubber. The rubber mixture according to the invention particularly preferably contains 3 to 30 phr of natural polyisoprene.

[0046] This results in optimized processability of the rubber compound according to the invention, in particular optimized mixing behavior, improved green strength and improved extrusion behavior.

[0047] The natural and / or synthetic polyisoprene used in all embodiments can be either cis-1,4-polyisoprene or 3,4-polyisoprene. However, the use of cis-1,4-polyisoprenes with a cis-1,4 content > 90 wt.% is preferred. Such polyisoprene can be obtained by stereospecific polymerization in solution with Ziegler-Natta catalysts or using finely divided lithium alkyls. Alternatively, natural rubber (NR) is such a cis-1,4-polyisoprene, with a cis-1,4 content greater than 99 wt.%.

[0048] Furthermore, a mixture of one or more natural polyisoprenes with one or more synthetic polyisoprene(s) is also conceivable.

[0049] Butadiene rubber (BR, polybutadiene) can be any type known to those skilled in the art. This includes, among others, the so-called high-cis and low-cis types, whereby polybutadiene with a cis content greater than or equal to 90 wt.% is referred to as high-cis type and polybutadiene with a cis content less than 90 wt.% as low-cis type. For example, Li-BR (lithium-catalyzed butadiene rubber) with a cis content of 20 to 50 wt.% is a low-cis polybutadiene. High-cis BR offers particularly good abrasion resistance and low hysteresis of the rubber compound.

[0050] The polybutadiene(s) used may be end-modified and / or functionalized along the polymer chains. These modifications may involve hydroxy groups, ethoxy groups, epoxy groups, siloxane groups, amino groups, aminosiloxane, carboxy groups, phthalocyanine groups, and / or silane sulfide groups. Other modifications, also known as functionalizations, are also possible and are known to a qualified professional. Metal atoms may be part of such functionalizations.

[0051] In a preferred embodiment of the invention, the functionalized styrene-butadiene copolymer (A) is present in the rubber compound according to the invention in amounts of 20 to 70 phr, preferably 30 to 60 phr, and particularly preferably 40 to 60 phr, and the at least one ESBR (B) is present in amounts of 10 to 50 phr, preferably 20 to 50 phr, and particularly preferably 20 to 40 phr, and the further diene rubber is present in amounts of 3 to 30 phr, particularly preferably 3 to 25 phr. Preferably, the further diene rubber is also natural polyisoprene in this embodiment, with the advantages mentioned above.

[0052] In a particularly preferred embodiment of the invention, the amount of functionalized styrene-butadiene copolymer (A) contained in the rubber mixture is 45 to 55 phr and the amount of ESBR (B) is 25 to 35 phr. The rubber mixture preferably contains 15 to 25 phr of at least one natural polyisoprene.

[0053] The rubber compound according to the invention contains 20 to 300 phr of silica and / or carbon black. Preferably, the rubber compound contains at least one silica compound.

[0054] The terms “silica” and “silicic acid” are used synonymously within the scope of the present invention, as is also customary in the field.

[0055] The rubber mixture can contain 0 to 270 phr, preferably 0 to 200 phr, particularly preferably 0 to 150 phr, silica.

[0056] According to a preferred embodiment of the invention, the rubber compound contains at least 0.1 phr, and more preferably at least 0.5 phr, of silica. In this embodiment, the rubber compound more preferably contains 20 to 150 phr, and more preferably 60 to 150 phr, and again more preferably 70 to 90 phr of silica. This results in particularly good rolling resistance properties combined with good abrasion resistance. In this preferred embodiment, the rubber compound more preferably contains 2 to 20 phr, and more preferably 10 to 17 phr of carbon black.

[0057] The silicas in question can be those known to experts as fillers suitable for tire rubber compounds. However, it is particularly preferred to use finely dispersed, precipitated silica with a nitrogen surface area (BET surface area) (according to DIN ISO 9277 and DIN 66132) of 35 to 400 m².2 / g, preferably from 60 to 350 m 2 / g, especially preferably from 120 to 320 m 2 / g, and a CTAB surface area (according to ASTM D 3765) of 30 to 380 m² 2 / g, preferably from 50 to 330 m 2 / g, especially preferably from 110 to 300 m 2 / g, exhibits.

[0058] Such silicas, for example, result in particularly good physical properties of vulcanizates in rubber compounds for tire treads. Furthermore, advantages in compound processing can arise from a reduction in mixing time while maintaining consistent product properties, leading to improved productivity. Suitable silicas include, for example, those of the Ultrasil® VN3 type (trade name) from Evonik, as well as highly dispersible silicas, so-called HD silicas (e.g., Zeosil® 1165 MP from Solvay).

[0059] Within the scope of the present invention, all types of carbon black known to those skilled in the art are conceivable. However, a carbon black is preferably used that has an iodine adsorption number according to ASTM D 1510 of 20 to 180 g / kg, particularly preferably 30 to 140 g / kg, and a DBP number according to ASTM D 2414 of 30 to 200 ml / 100 g, preferably 90 to 180 ml / 100 g, particularly preferably 90 to 150 ml / 100 g. A particularly suitable carbon black within the scope of the present invention is, for example, a carbon black of ASTM type N339 with an iodine adsorption number of 90 g / kg and a DBP number of 120 ml / 100 g. This provides particularly good properties for use in vehicle tires, especially in the tread, with regard to the technical objective.

[0060] The rubber compound according to the invention can contain further fillers, preferably in the smallest possible amounts, i.e., preferably 0 to 2 phr. Further (non-reinforcing) fillers within the scope of the present invention include aluminosilicates, kaolin, chalk, starch, magnesium oxide, titanium dioxide, or rubber gels, as well as fibers (such as aramid fibers, glass fibers, carbon fibers, cellulose fibers).

[0061] Other potentially reinforcing fillers include, for example, carbon nanotubes (CNTs) including discrete CNTs, so-called hollow carbon fibers (HCF) and modified CNTs containing one or more functional groups, such as hydroxy, carboxy and carbonyl groups), graphite and graphene and so-called “carbon-silica dual-phase fillers”.

[0062] Zinc oxide is not one of the fillers in the present invention.

[0063] To improve processability and to bind silica and any other polar fillers present to the diene monomer, silane coupling agents can be used in rubber compounds. One or more different silane coupling agents can be used in combination. The rubber compound can thus contain a mixture of different silanes. The silane coupling agents react with the surface silanol groups of the silica or other polar groups during the mixing of the rubber or rubber compound (in situ) or even before the addition of the filler to the rubber as a pretreatment (pre-modification). Any silane coupling agents known to those skilled in the art for use in rubber compounds can be used as such.Such coupling agents known from the prior art are bifunctional organosilanes that possess at least one alkoxy, cycloalkoxy, or phenoxy group as a leaving group on the silicon atom and that exhibit as a further functionality a group which, if necessary after cleavage, can undergo a chemical reaction with the double bonds of the polymer. The latter group can be, for example, the following chemical groups: -SCN, -SH, -NH2 or -S x - (with x = 2 to 8).

[0064] Suitable silane coupling agents include, for example, 3-mercaptopropyltriethoxysilane, 3-thiocyanatopropyltrimethoxysilane, or 3,3'-bis(triethoxysilylpropyl)polysulfides with 2 to 8 sulfur atoms, such as 3,3'-bis(triethoxysilylpropyl)tetrasulfide (TESPT), the corresponding disulfide (TESPD), or mixtures of sulfides with 1 to 8 sulfur atoms and varying concentrations of the different sulfides. TESPT can also be added, for instance, as a mixture with carbon black (trade name X50S® from Evonik).

[0065] Preferably, a silane mixture is used which contains 40 to 100 wt% disulfides, particularly preferably 55 to 85 wt% disulfides, and most preferably 60 to 80 wt% disulfides. Such a mixture is available, for example, under the trade name Si 261® from Evonik, which is described, for example, in DE 102006004062 A1.

[0066] Blocked mercaptosilanes, such as those known from WO 99 / 09036, can also be used as silane coupling agents. Silanes as described in WO 2008 / 083241 A1, WO 2008 / 083242 A1, WO 2008 / 083243 A1, and WO 2008 / 083244 A1 can also be used. Suitable silanes include those marketed under the name NXT (e.g., 3-(octanoylthio)-1-propyl-triethoxysilane) in various formulations by Momentive, USA, or those marketed under the name VP Si 363® by Evonik Industries.

[0067] Furthermore, it is conceivable that one of the above-mentioned mercaptosilanes, in particular 3-mercaptopropyltriethoxysilane, may be used in combination with processing aids (listed below), in particular PEG carboxylic acid esters.

[0068] According to a preferred embodiment of the invention, the rubber mixture contains a combination of 3-mercaptopropyltriethoxysilane and PEG carboxylic acid ester, resulting in particularly good properties, especially with regard to the technical problem to be solved, as well as an overall good level of properties with regard to the other properties.

[0069] Furthermore, the rubber compound may contain additional activators and / or agents for binding fillers, in particular carbon black. These may include, for example, the compound S-(3-Aminopropyl)thiosulfuric acid disclosed in EP 2589619 A1 and / or its metal salts, which, especially in combination with at least one carbon black as a filler, result in very good physical properties of the rubber compound.

[0070] The silanes and activators mentioned are preferably added in at least one basic mixing stage during the production of the rubber compound.

[0071] According to a preferred embodiment, the rubber compound according to the invention contains at least one plasticizer, wherein the total amount of plasticizer is preferably 1 to 50 phr, more preferably 10 to 50 phr. This results, particularly in combination with the above-mentioned components, in particularly good processability of the rubber compound, especially of the extrudates before crosslinking, with simultaneously good rolling resistance indicators and good (and therefore low) heat build-up.

[0072] The plasticizers used in the present invention include all plasticizers known to those skilled in the art, such as aromatic, naphthenic, or paraffinic mineral oil plasticizers, e.g., MES (mild extraction solvate), RAE (residual aromatic extract), or TDAE (treated distillate aromatic extract), or rubber-to-liquid (RTL) oils or biomass-to-liquid (BTL) oils, preferably with a polycyclic aromatic content of less than 3 wt.% according to method IP 346, or rapeseed oil or Faktisse, or plasticizer resins, or liquid polymers whose mean molecular weight (determined by GPC = gel permeation chromatography, in accordance with BS ISO 11344:2004) is between 500 and 20,000 g / mol. If additional liquid polymers are used as plasticizers in the rubber compound according to the invention, these are not included as rubber in the calculation of the polymer matrix composition.

[0073] The plasticizer resins can be, in particular and preferably, unmodified phenolic resins.

[0074] The plasticizer is preferably selected from the group consisting of the plasticizers mentioned above.

[0075] Mineral oils are particularly preferred as plasticizers.

[0076] When using mineral oil, it is preferably selected from the group consisting of DAE (Destilled Aromatic Extracts) and / or RAE (Residual Aromatic Extract) and / or TDAE (Treated Destillated Aromatic Extracts) and / or MES (Mild Extracted Solvents) and / or naphthenic oils.

[0077] According to a preferred embodiment of the invention, the rubber compound contains at least one mineral oil plasticizer, preferably at least TDAE and / or RAE as plasticizers. This results in particularly good processability, especially good miscibility of the rubber compound.

[0078] The plasticizer(s) are preferably added in at least one basic mixing stage during the production of the rubber compound according to the invention.

[0079] Furthermore, the rubber compound may contain common additives in usual proportions by weight, which are preferably added during its manufacture in at least one basic mixing stage. These additives include: a) Antioxidants, such as N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditolyl-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ), b) Activators, such as zinc oxide and fatty acids (e.g. stearic acid) and / or other activators, such as zinc complexes such as zinc ethylhexanoate, c) Waxes, d) Resins, e) Mastication aids, such as 2,2'-dibenzamidodiphenyldisulfide (DBD) and f) Process aids, in particular fatty acid esters and metal soaps, such as zinc soaps and / or calcium soaps.

[0080] The quantity of other additives in the total quantity is 3 to 150 phr, preferably 3 to 100 phr and particularly preferably 5 to 80 phr.

[0081] Zinc oxide (ZnO) may be present in the total quantity of other additives in the amounts mentioned above.

[0082] This can include all types of zinc oxide known to experts, such as ZnO granules or powder. The zinc oxide used conventionally typically has a BET surface area of ​​less than 10 m². 2 / g. However, it can also be a zinc oxide with a BET surface area of ​​10 to 100 m². 2 / g, such as so-called “nano-zinc oxides”, are used.

[0083] The vulcanization of the sulfur-crosslinkable rubber compound according to the invention is carried out in the presence of sulfur and / or sulfur donors using vulcanization accelerators, some of which can also act as sulfur donors. The accelerator is selected from the group consisting of thiazole accelerators, mercapto accelerators, sulfenamide accelerators, thiocarbamate accelerators, thiuram accelerators, thiophosphate accelerators, thiourea accelerators, xanthate accelerators, and / or guanidine accelerators.

[0084] The use of a sulfenamide accelerator selected from the group consisting of N-cyclohexyl-2-benzothiazole sulfenamide (CBS) and / or N,N-dicyclohexylbenzothiazole-2-sulfenamide (DCBS) and / or benzothiazole-2-sulfene morpholide (MBS) and / or N-tert-butyl-2-benzothiazole sulfenamide (TBBS) is preferred.

[0085] Any sulfur-donating substance known to those skilled in the art can be used as the sulfur-donating substance. If the rubber mixture contains a sulfur-donating substance, it is preferably selected from the group containing, for example, thiuram disulfides, such as tetrabenzylthiuram disulfide (TBzTD) and / or tetramethylthiuram disulfide (TMTD) and / or tetraethylthiuram disulfide (TETD), and / or thiuram tetrasulfides, such as dipentamethylenethiuram tetrasulfide (DPTT), and / or dithiophosphates, such as...

[0086] DipDis (Bis-(Diisopropyl)thiophosphoryldisulfide) and / or Bis(O,O-2-ethylhexylthiophosphoryl)Polysulfide (e.g. Rhenocure SDT 50®, Rheinchemie GmbH) and / or Zinc dichloroyldithiophosphate (e.g. Rhenocure ZDT / S®, Rheinchemie GmbH) and / or Zinc alkyldithiophosphate, and / or 1,6-Bis(N,N-dibenzylthiocarbamoyldithio)hexane and / or Diarylpolysulfides and / or Dialkylpolysulfides.

[0087] Other network-forming systems, such as those available under the trade names Vulkuren®, Duralink®, or Perkalink®, or network-forming systems as described in WO 2010 / 049216 A2, can also be used in the rubber compound. This system contains a vulcanizing agent that crosslinks with a functionality greater than four and at least one vulcanization accelerator. The vulcanizing agent that crosslinks with a functionality greater than four has, for example, the general formula D): D) G[C a H 2a -CH2-S b Y] c where G is a polyvalent cyclic hydrocarbon group and / or a polyvalent heterohydrocarbon group and / or a polyvalent siloxane group containing 1 to 100 atoms; where each Y is independently selected from a rubber-active group containing sulfur-containing functionalities; and where a, b and c are integers such that independently: a equals 0 to 6; b equals 0 to 8; and c equals 3 to 5.

[0088] The rubber-active group is preferably selected from a thiosulfonate group, a dithiocarbamate group, a thiocarbonyl group, a mercapto group, a hydrocarbon group, and a sodium thiosulfonate group (Bunte salt group). This results in very good abrasion and tear properties of the rubber compound according to the invention.

[0089] Within the scope of the present invention, sulfur and sulfur donors, including sulfur-donating silanes such as TESPT, and vulcanization accelerators as described above, and vulcanizing agents that crosslink with a functionality greater than four, as described in WO 2010 / 049216 A2, such as a vulcanizing agent of formula D), as well as the above-mentioned systems Vulkuren®, Duralink® and Perkalink®, are conceptually grouped together as vulcanizing agents.

[0090] In the production of the rubber compound according to the invention, at least one vulcanizing agent selected from the group consisting of, and particularly preferably comprising, sulfur and / or sulfur donors and / or vulcanization accelerators and / or vulcanizing agents that crosslink with a functionality greater than four, is preferably added in the final mixing stage. This allows a sulfur-crosslinked rubber compound, particularly for use in vehicle tires, to be produced from the mixed final mixture by vulcanization.

[0091] The use of the accelerators TBBS and / or CBS and / or diphenylguanidine (DPG) is particularly preferred.

[0092] Furthermore, vulcanization retarders may be present in the rubber compound.

[0093] The terms “vulcanized” and “crosslinked” are used synonymously within the scope of the present invention.

[0094] According to a preferred embodiment of the invention, several accelerators are added in the final mixing stage during the production of the sulfur-crosslinkable rubber mixture.

[0095] The production of the sulfur-curable rubber compound according to the invention is carried out according to a process customary in the rubber industry, in which a base mixture is first produced in one or more mixing stages with all components except the vulcanization system (sulfur and vulcanization-influencing substances). The finished compound is produced by adding the vulcanization system in a final mixing stage. The finished compound is further processed, for example, by extrusion or calendering and formed into the desired shape. Subsequent processing is carried out by vulcanization, whereby sulfur crosslinking occurs due to the vulcanization system added within the scope of the present invention.

[0096] The rubber compound according to the invention described above is particularly suitable for use in vehicle tires, especially pneumatic tires. Its application in all tire components is conceivable in principle, particularly in the tread, and especially in the cap of a tread with a cap / base construction. The cap is the part of the tire tread that comes into contact with the road surface, while the base is the radially located inner part of the tread that does not come into contact with the road surface.

[0097] For use in vehicle tires, the mixture is preferably formed into the shape of a tread strip as a ready-made mixture before vulcanization and applied during the production of the vehicle tire blank as is known.

[0098] The production of the rubber compound according to the invention for use as a body compound in vehicle tires is carried out as already described. The difference lies in the shaping after the extrusion process or the calendering of the compound. The resulting shapes of the still unvulcanized rubber compound for one or more different body compounds then serve to construct a tire blank.

[0099] The term "body compound" refers to the rubber compounds used for the other external and internal components of a tire, such as essentially the squeegee, sidewall, inner liner (inner layer), core profile, belt, shoulder, belt profile, carcass, bead reinforcement, bead profile, horn profile and bandage.

[0100] For the use of the rubber compound according to the invention in belts and straps, particularly in conveyor belts, the extruded, still unvulcanized compound is formed into the appropriate shape and is often provided with reinforcing elements, e.g., synthetic fibers or steel cords, either during or after this process. This usually results in a multi-layered structure consisting of one and / or more layers of rubber compound, one and / or more layers of the same and / or different reinforcing elements, and one and / or more further layers of the same and / or a different rubber compound.

[0101] The invention will now be explained in more detail with reference to comparative and exemplary embodiments, which are summarized in Table 1.

[0102] The comparison mixtures are marked with V, the mixtures according to the invention are marked with E.

[0103] The compound was prepared according to standard rubber industry procedures under normal conditions in three stages using a laboratory mixer. In the first stage (base mix), all components except the vulcanization system (sulfur and vulcanization-influencing substances) were mixed. In the second stage, the base mix was thoroughly blended again. Finally, in the third stage (final mix), the vulcanization system was added, and the mixture was blended at 90 to 120 °C.

[0104] Test specimens were produced from all mixtures by vulcanization after 20 minutes under pressure at 160°C and material properties typical for the rubber industry were determined using these test specimens with the test procedures specified below. • Shore A hardness at room temperature (RT) according to DIN ISO 7619-1 and conditioned Shore A hardness in accordance with DIN ISO 7619-1, preconditioned ten times with 5 MPa and then tested according to ISO 868. • Rebound elasticity at room temperature and 70°C according to ISO 4662 or ASTM D 1054 • Tensile strength, elongation at break and stress value at 300% elongation (M300) at room temperature according to DIN 53 504 • Maximum (max) loss factor tan δ (tanens delta, tan d max) and mean dynamic storage modulus E' from dynamic-mechanical measurement at 55 °C according to DIN 53 513, strain sweep at a pre-compression of 20%, a frequency of 10 Hz and a strain range of 0.1% to 12%. Substances used: • a) SBR: SSBR, Nipol NS 612 • b) ESBR: SBR 1723; oil-diluted with 37.5 phr TDAE per 100 phr of SBR: in the mixture, 41.2 phr SBR 1723 = 30 phr ESBR, 11.2 phr TDAE, styrene content = 16 wt.%, vinyl content = 16 wt.% • c) SBR: SSBR HPR 840, JSR Corporation: solution-polymerized functionalized styrene-butadiene copolymer, which is functionalized at at least one end of each polymer chain with an amino-group-containing alkoxysilyl group and another functional group selected from the group consisting of alkoxysilyl groups and amino-group-containing alkoxysilyl groups; styrene content: 10 wt%, vinyl content approx. 40%, T g = -60 °C • d) Silica VN3, Evonik • e) TDAE • f) Process aids: fatty acid esters and zinc soaps • g) Silane 75% S2-Silane, Si75®, Evonik • h) Anti-aging agents: 6PPD, ozone-protecting wax • i) Vulcanization accelerators: CBS, MBT (2-Mercaptobenzothiazole) and DPG Table 1 Components Unit V1 V2 V3 E1 NR TSR phr 20 20 20 20 SBR a) phr 80 - 50 - ESBR b) phr - - 41,2 41,2 SBR c) phr - 80 - 50 Soot N339 phr 14 14 14 14 Silica d) phr 85 85 85 85 Öl e) phr 40 40 28,7 28,7 ZnO phr 3 3 3 3 Stearic acid phr 2 2 2 2 Process aids f) phr 5 5 5 5 Powerful g) phr 6 6 6 6 Age protection h) phr 4 4 4 4 accelerator i) phr 3,8 3,8 3,8 3,8 sulfur phr 2,1 2,1 2,1 2,1 Physical properties Shore hardness A Shore A 62 62 60 62 cond. Sh A Shore A 59 59 55 59 Rebound RT % 38 44 37 41 Rebound 70 °C % 49 54 47 53 Differential return 11 10 10 12 Tensile strength MPa 10 14 14 16 Elongation at break % 446 537 649 575 M300 MPa 6,8 7,2 5,8 7,8 E' (medium) MPa 8,3 7,9 7,6 8,1 tan d max. 0,19 0,16 0,20 0,16

[0105] As can be seen in Table 1, the rubber compound E1 according to the invention achieves an improvement in the trade-off between rolling resistance and wet grip indicators (difference in rebound elasticities; rebound elasticity at 70 °C minus rebound elasticity at room temperature). At the same time, the rubber compound E1 surprisingly exhibits a comparatively high stiffness (M300, E'), thus providing improved or surprisingly good handling indicators.

[0106] This improvement in the indicators for rolling resistance, wet grip, and handling behavior would not have been expected based on the individual measures, namely functionalized SBR (A) alone as in V2 or ESBR (B) alone as in V3, as Table 1 shows. Thus, the combination of the components of the rubber compound according to the invention shows an unexpected synergistic effect.

[0107] A vehicle tire which incorporates the rubber compound according to the invention in at least one component, preferably at least in the tread and at least in the cap in the case of cap / base construction, has a lower and therefore optimized rolling resistance compared to the prior art, with good wet grip and handling properties.

Claims

Sulfur-crosslinkable rubber compound containing: - 20 to 70 phr of at least one functionalized styrene-butadiene copolymer A, wherein the functionalized styrene-butadiene copolymer is functionalized at at least one chain end per polymer chain with an amino group-containing alkoxysilyl group and at least one further alkoxysilyl group(s) and / or at least one further amino group-containing alkoxysilyl group(s), and - 10 to 50 phr of at least one emulsion-polymerized styrene-butadiene rubber B, which in the unvulcanized state has a styrene content of 5 to 30 wt.%, and a vinyl content based on the butadiene content of 5 to 70 wt.%, and - 20 to 300 phr of silica and / or carbon black. Rubber compound according to claim 1, characterized in that the functionalized styrene-butadiene copolymer A is a solution polymerized styrene-butadiene copolymer. Rubber compound according to one of the preceding claims, characterized in that the functionalized styrene-butadiene copolymer A has a styrene content of 5 to 30 wt.%. Rubber compound according to one of the preceding claims, characterized in that the functionalized styrene-butadiene copolymer A has a glass transition temperature of -15 to -70 °C. Rubber compound according to one of the preceding claims, characterized in that the functionalized styrene-butadiene copolymer A comprises a further group selected from the group consisting of alkoxysilyl groups and amino group-containing alkoxysilyl groups. Rubber compound according to one of the preceding claims, characterized in that it contains 3 to 30 phr of natural polyisoprene. Rubber compound according to one of the preceding claims, characterized in that it contains 45 to 55 phr of the functionalized styrene-butadiene copolymer (A) and 25 to 35 phr of the ESBR (B) and 15 to 25 phr of at least one natural polyisoprene. Rubber compound according to one of the preceding claims, characterized in that it contains 70 to 90 phr silica. Vehicle tire comprising in at least one component at least one vulcanizate of at least one sulfur-crosslinkable rubber compound according to at least one of claims 1 to 8. Vehicle tire according to claim 9, characterized in that the component is at least the tread.