rubber compound and tires

Abstract

The invention relates to a sulfur-crosslinkable rubber compound, in particular for the tread of vehicle tires, comprising at least the following components: - 50 to 100 phr (parts by weight, based on 100 parts by weight of the total rubbers in the compound) of at least one solid, solution-polymerized butadiene rubber (BR) with a cis content of less than 90 wt.%, - up to 20 phr of at least one natural polyisoprene (NR), - up to 40 phr of at least one solution-polymerized styrene-butadiene rubber (SSBR), - 1 to 40 phr of at least one liquid polybutadiene, which is organosilicon-modified and has a mean molecular weight Mw according to GPC of 500 to 18000 g / mol, and - 10 to 300 phr of at least one silica.

Description

The invention relates to a sulfur-crosslinkable rubber mixture, in particular for the tread of vehicle tires. The invention further relates to a pneumatic vehicle tire having a tread which consists at least in part of such a rubber mixture vulcanized with sulfur.Since the driving properties of a tire, in particular pneumatic vehicle tires, are to a large extent dependent on the rubber composition of the tread, particularly high requirements are placed on the composition of the tread mixture. Thus, various attempts have been made to positively influence the properties of the tire by varying the polymer components, the fillers and the other additives in the tread mixture. In this case, it must be taken into account that an improvement in one tire property often brings about a deterioration of another property, for example an improvement in the abrasion behavior is usually associated with a deterioration in the braking behavior on a dry roadway. For example, the highest requirements are placed on tread mixtures for passenger cars and van tires with regard to wet and dry braking, abrasion resistance, cut-and-chip behavior, rolling resistance, durability and handling.In order to influence tire properties such as abrasion, wet skid properties and rolling resistance, it is known, for example, to use solution-polymerized styrene-butadiene copolymers having different microstructure. Diene rubbers can also be modified by end group modifications, couplings or hydrogenations. The different types of copolymer have different influences on the vulcanisate and thus also on the tire properties.Functionalized diene elastomers for siliceous rubber mixtures for tires are described, for example, in EP 3 150 403 A1, EP 3 150 402 A1, EP 3 150 401 A1, DE 10 2015 218 745 A1 and DE 10 2015 218 746 A1.Furthermore, U.S. Pat. No. 2021347206 A1 and U.S. Pat. No. 2021230403 A1 describe rubber mixtures for tire treads which comprise butadiene rubber (polybutadiene, BR) having a low cis content.For improving the balance of durability and hysteresis properties of rubber mixtures for tire treads, WO2020218601 A1 discloses mixtures with 70 phr of styrene-butadiene copolymer (SSBR), 30 phr of high-cis butadiene rubber (polybutadiene, BR), silica, vegetable oil, resin and 3,3'-bis(triethoxysilylpropyl)tetrasulfide (TESPT) as a silane coupling agent.The object of the invention is to provide rubber mixtures for the treads of vehicle tires, in particular pneumatic vehicle tires, which in tires lead to improved rolling resistance with low abrasion at the same time.This object is achieved according to the invention by a sulfur-crosslinkable rubber mixture, in particular for the tread of vehicle tires, which contains at least the following constituents:50 to 100 phr (parts by weight, based on 100 parts by weight of the total rubbers in the mixture) of at least one solid, solution-polymerized butadiene rubber (BR) having a cis fraction of less than 90% by weight,up to 20 phr of at least one natural polyisoprene (NR),up to 40 phr of at least one solution polymerized styrene butadiene rubber (SSBR),1 to 40 phr of at least one liquid polybutadiene which is organosilicon-modified and has an average molecular weight M w according to GPC of 500 to 1800 g / mol, and10 to 300 phr of at least one silica.The stated phr (parts per hundred parts of rubber by weight) used in this specification is the stated amount of mixture formulations customary in the rubber industry. The dosage of the parts by weight of the individual substances is always based on 100 parts by weight of the total mass of all solid rubbers present in the mixture. Liquid polybutadienes are not included in the total mass of the solid rubbers.Surprisingly, it has been found that the specific combination of a solid, solution-polymerized butadiene rubber (BR, polybutadiene) having a cis fraction of less than 90% by weight with a liquid polybutadiene which is organosilicon-modified and has an average molecular weight M w according to GPC of 500 to 18000 g / mol, in the amounts specified in siliceous mixtures, leads to a reduced loss factor tan δ (10%) from RPA measurement (=cl. "rubber process analyzer") on the conditioned sample on the basis of ASTM D6601. This reduced loss factor tan δ (10%) can be correlated with a reduced rolling resistance when the mixture is used in tire treads. At the same time, the abrasion is reduced, whereby higher tire durability is achieved.The rubber mixture contains 50 to 100 phr of at least one solid, solution-polymerized butadiene rubber (BR) having a cis fraction of less than 90% by weight, preferably having a cis fraction of between 20 and 50% by weight. It is also possible to use a plurality of solution-polymerized butadiene rubbers.The butadiene rubber (polybutadiene, BR) used may be any types known to those skilled in the art which have a cis fraction of less than 90% by weight. These include the so-called low-cis types, butadiene rubber having a cis content of less than 90% by weight being referred to as low-cis type. Preferably, a low-cis butadiene rubber with a cis content between 20 and 50 wt %, e.g. Li-BR (lithium-catalyzed butadiene rubber), is used.According to a preferred development of the invention, the solution-polymerized, functionalized butadiene rubbers are functionalized with a group which enables interaction with the silica. The butadiene rubbers can be end group-modified and / or functionalized along the polymer chains with a wide variety of functionalizations (modifications) which make possible an interaction with the silica. The functionalization can be those with hydroxyl groups and / or ethoxy groups and / or epoxy groups and / or siloxane groups and / or aminosiloxane and / or carboxy groups and / or silane sulfide groups. However, other modifications or functionalizations known to the person skilled in the art are also possible. Different functionalizations can also be provided at both chain ends. Metal atoms can also be a constituent of the functionalizations.In addition to the functionalizations which enable interaction with silica, the butadiene rubber may also have further functionalizations which enable interactions with nonpolar fillers, such as carbon black.The rubber mixture according to the invention contains up to 20 phr of at least one natural polyisoprene (natural rubber, NR). Natural polyisoprene is understood as rubber which can be obtained by harvesting sources such as rubber trees (Hevea brasiliensis) or non-rubber tree sources (such as guayule or löwen tooth (e.g. Taraxacum kokoaghyz)). Natural polyisoprene (NR) is understood to mean nonsynthetic polyisoprene. Natural polyisoprenes from various sources can also be used in blends. The cis-1,4 content in the natural polyisoprene is greater than 99% by weight.The rubber mixture according to the invention contains up to 40 phr of at least one solution-polymerized styrene-butadiene rubber (SSBR). The styrene-butadiene copolymers can be end group-modified and / or functionalized along the polymer chains with a wide variety of functionalizations (modifications) which enable interaction with the silica. The functionalization can be those with hydroxyl groups and / or ethoxy groups and / or epoxy groups and / or siloxane groups and / or aminosiloxane and / or carboxy groups and / or silane sulfide groups. However, other modifications or functionalizations known to the person skilled in the art are also possible. Different functionalizations can also be provided at both chain ends. Metal atoms can also be a constituent of the functionalizations.In addition to the aforementioned types of rubber, the rubber mixture can optionally be further diene elastomers such as synthetic polyisoprene and / or high-cis butadiene rubbers and / or emulsion-polymerized styrene-butadiene rubbers and / or styrene-isoprene rubbers and / or halobutyl rubbers and / or polynorbornene and / or isoprene-isobutylene copolymers and / or ethylene-propylene-diene rubbers. The rubbers can be used as pure rubbers or in oil-extended form.For a particularly low rolling resistance and low abrasion when used as tire tread, it has proven advantageous if the rubber mixture is at least one of low rolling resistance and low abrasion.60 to 95 phr of at least one solid, solution-polymerized butadiene rubber (BR) having a cis content of less than 90% by weight,5 to 15 phr of at least one natural polyisoprene (NR), and10 to 30 phr of at least one solution-polymerized styrene-butadiene rubber (SSBR).To further improve the tire properties, the solid rubbers in the blend together have a blend glass transition temperature Tg (blend) of -90 to -77°C. The blend glass transition temperature Tg (blend) results from the glass transition temperatures of the individual solid rubbers and their proportions in the blend. The glass transition temperature (Tg) of the polymers is determined by means of differential scanning calorimetry (Engl. Dynamic scanning calorimetry, DSC according to DIN 53765: 1994-03 or ISO 11357-2: 1999-03, calibrated DSC with low-temperature device, calibration according to the type of instrument and manufacturer specifications, sample in the aluminium crucible with aluminium lid, cooling to temperatures lower than -120° C. at 10° C. / min).The rubber mixture according to the invention comprises 1 to 40 phr, preferably 2 to 17 phr, of at least one liquid polybutadiene which is organosilicon-modified and has an average molecular weight M w according to GPC of 500 to 18000 g / mol. The abbreviation M w stands for the weight-average molecular weight of polymers. The weight average M w is determined by means of gel permeation chromatography (GPC using polybutadiene standard). The range of values of M w from 500 to 18000 g / mol includes that room temperature is a liquid polybutadiene. For the sake of simplicity, the short term "liquid polybutadiene" is therefore also used in the context of the present invention. The M w is reported as referring to the polybutadiene including the organosilicon modification.The liquid polybutadiene can be organosilicon-modified terminally and / or along the chain.The liquid polybutadiene is preferably modified with at least one radical of the formula I): (R 1 R 2 R 3) Si-I) where R 1, R 2, R 3 may be identical or different in the structures and may be selected from linear or branched alkoxy, cycloalkoxy, alkyl, cycloalkyl or aryl groups having 1 to 20 carbon atoms, and where the radical of the formula I) is bonded directly or via a bridge to the polymer chain of the polybutadiene, and where the bridge consists of a saturated or unsaturated carbon chain which may also contain cyclic and / or aliphatic and / or aromatic elements and also heteroatoms in or on the chain. Such a modification provides advantages in rolling resistance of tires.According to a preferred development of the invention, the liquid polybutadiene is terminally modified with a triethoxysilane group. These polybutadienes are easily prepared and are available on the market on an industrial scale, for example under the name Polyvest® EP ST-E 60 from Evonik.For improvement of winter properties and rolling resistance, the liquid polybutadiene which is organosilicon-modified has a glass transition temperature T g according to DSC of -85 to -30° C. The glass transition temperature (T g) of the polymers is determined by means of differential scanning calorimetry (Engl. Dynamic scanning calorimetry, DSC according to DIN 53765: 1994-03 or ISO 11357-2: 1999-03, calibrated DSC with low-temperature device, calibration according to the type of instrument and manufacturer specifications, sample in the aluminium crucible with aluminium lid, cooling to temperatures lower than -120° C. at 10° C. / min).The liquid, organosilicon-modified polybutadiene preferably has a vinyl content (content of 1,2-bonded butadiene, based on the monomers of the polymer chain of the polybutadiene) of from 5 to 30%, particularly preferably from 10 to 25%. The liquid polybutadiene preferably has a 1,4-trans proportion of 40 to 75% (based on the monomers of the polymer chain of the polybutadiene). The cis content of the liquid polybutadiene is preferably 5 to 30% (based on the monomers of the polymer chain of the polybutadiene).The rubber mixture according to the invention preferably contains 5 to 40 phr, particularly preferably 10 to 30 phr, of at least one plasticizer which is not a mineral oil plasticizer. It is possible to use one or more plasticizers in combination.As plasticizers which are not mineral oil plasticizers, a wide variety of plasticizers can be used, such as vegetable oils, factissates or liquid polymers. The plasticizer or plasticizers are preferably added in at least one basic mixing stage in the preparation of the rubber mixture of the invention.According to an advantageous development of the invention, the plasticizer used is a liquid polybutadiene without organosilicon modification, which has an average molecular weight M w according to GPC of 500 to 18000 g / mol. These liquid polybutadienes are well compatible with the other polymers of the rubber mixture and have a low tendency to diffuse. As liquid polybutadiene without organosilicon modification, it is possible to use, for example, Ricon® 130 from Cray Valley.In addition to the aforementioned plasticizers, mineral oil plasticizers may also be present in the rubber mixture. As mineral oil softeners, it is possible to use all mineral oil softeners known to the skilled worker, such as aromatic, naphthenic or paraffinic mineral oil softeners, such as, for example, MES (mild extraction solvate) or RAE (residual aromatic extract) or TDAE (treated distillate aromatic extract), preferably having a content of polycyclic aromatics of less than 3% by weight according to method IP 346. Preferably, however, the rubber composition of the invention is free of mineral oil softeners.The rubber mixture according to the invention contains 10 to 300 phr, preferably 50 to 200 phr, of silica in order to achieve good processability with good tire properties.A wide variety of silicas, such as low surface area or highly dispersible silica, can be used, including as a mixture. It is particularly preferred if a finely divided, precipitated silica is used which has a CTAB surface area (according to ASTM D 3765) of from 30 to 350 m 2 / g, preferably from 110 to 250 m 2 / g. The silicas used may be either conventional silicas or those of the type VN3 from Evonik, or highly dispersible silicas, known as HD silicas (e.g. Ultrasil ®7000 from Evonik).To improve the processability and to attach the silica to the diene rubber in siliceous mixtures, at least one silane coupling agent is preferably used in amounts of 1-15 phf (parts by weight, based on 100 parts by weight of silica) in the rubber mixture. The silane coupling agents can also be used in a mixture.The stated phf (parts per hundred parts of filler by weight) used in this specification is the stated amount of coupling agents for fillers which is customary in the rubber industry. Within the scope of the present application, phf refers to the silica present, i.e. that other fillers that may be present, such as carbon black, do not participate in the calculation of the amount of silane coupling agent.The silane coupling agents react with the surface silanol groups of the silica or other polar groups during the mixing of the rubber or of the rubber mixture (in situ) or already before the addition of the filler to the rubber in the sense of a pretreatment (pre-modification). The silane coupling agents used can be all silane coupling agents known to the skilled person for use in rubber mixtures. Such coupling agents known from the prior art are bifunctional organosilanes which have at least one alkoxy, cycloalkoxy or phenoxy group as leaving group on the silicon atom and which have as other functionality a group which, if appropriate after cleavage, can enter into a chemical reaction with the double bonds of the polymer. The latter group can be, for example, the following chemical groups: -SCN, -SH, -NH 2 or -S x- ( where x=2-8). Thus, for example, 3-mercaptopropyltriethoxysilane, 3-thiothionopropyltrimethoxysilane or 3,3'-bis(triethoxysilylpropyl)polysulfides having 2 to 8 sulfur atoms, such as, for example, 3,3'-bis(triethoxysilylpropyl)tetrasulfide (TESPT), the corresponding disulfide or else mixtures of the sulfides having 1 to 8 sulfur atoms with different contents of the various sulfides, can be used as silane coupling agents. TESPT can also be added, for example, as a mixture with carbon black (trade name X50S from Degussa). Blocked mercaptosilanes, as are known, for example, from WO 99 / 09036, can also be used as silane coupling agent. It is also possible to use silanes as described in WO 2008 / 083241 A1, WO 2008 / 083242 A1, WO 2008 / 083243 A1 and WO 2008 / 083244 A1. Usable are, for example, silanes sold under the name NXT ® in various variants by Momentive, USA, or those sold under the name VP Si 363 by Evonik Industries. It is also possible to use so-called "silylated core polysulfides" (SCP), which are described, for example, in U.S. Pat. No. 20080161477 A1 and EP 2 114 961 B1.Preferably, at least one silane coupling agent in the rubber mixture is 3,3'-bis(triethoxysilylpropyl) disulfide (TESPD).The rubber mixture may also comprise further fillers, such as carbon blacks, aluminosilicates, chalk, starch, magnesium oxide, titanium dioxide, rubber gels, carbon nanotubes, graphite, graphenes or what are known as "carbon-silica dual-phase filler" in customary amounts, it being possible for the fillers to be used in combination.If carbon black is present in the rubber mixture, all carbon black types known to the skilled worker can be used. However, preference is given to using a carbon black which has an iodine adsorption number according to ASTM D 1510 of 30 to 180 g / kg, preferably 30 to 130 kg / g, and a DBP number according to ASTM D 2414 of 80 to 200 ml / 100 g, preferably 100 to 200 ml / 100 g, particularly preferably 100 to 180 ml / 100 g. Particularly good rolling resistance indicators with good other tire properties are thereby achieved for use in the vehicle tire.In order to improve the rubber mixtures with regard to damping and thus wet braking when used as tire tread strips, it has proven advantageous if the rubber mixture comprises 20 to 60 phr of at least one resin. Suitable resins are, for example, resins based on isopropenylbenzene, aromatic hydrocarbon resins, such as aromatic C9 hydrocarbon resins, aliphatic hydrocarbon resins, such as aliphatic C5 hydrocarbon resins, or Cumeron-Inden resins. The resins can also be used in a mixture.In order to further improve the abrasion behavior and the rolling resistance, it has proven advantageous if at least one resin is one based on isopropenylbenzene. Resins based on isopropenylbenzene, also called AMS resins (α-methylstyrene resins), are obtained as copolymers in the polymerization of the unsaturated compounds present in the light oil of the coal tar. They are available, for example, under the name Sylvatrix ®4401 from Kraton Chemicals SAS.The rubber mixture may furthermore comprise customary additives in customary parts by weight, which are preferably added in at least one basic mixing stage during the preparation thereof. These additives include a) anti-ageing agents, such as N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PP), 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), or zinc complexes, such as zinc ethylhexanoate, c) waxes, d) masticating auxiliaries, such as 2,2'-dibenzamidodiphenyl disulfide (DBD), and e) processing auxiliaries, such as fatty acid salts, such as zinc soaps, and fatty acid esters and derivatives thereof.The proportion of the total amount of further additives is 3 to 150 phr, preferably 3 to 100 phr and particularly preferably 5 to 80 phr.The vulcanization of the rubber mixture is carried out in the presence of sulfur and / or sulfur donors with the aid of vulcanization accelerators, it being possible for some vulcanization accelerators to act simultaneously as sulfur donors. The accelerator is selected from the group consisting of thiazole accelerators and / or mercapto accelerators and / or sulfenamide accelerators and / or thiocarbamate accelerators and / or thiuram accelerators and / or thiophosphate accelerators and / or thiourea accelerators and / or xanthate accelerators and / or guanidine accelerators. Preference is given to the use of a sulfenamide accelerator selected from the group consisting of N-cyclohexyl-2-benzothiazolesulfenamide (CBS) and / or N,N-dicyclohexylbenzothiazole-2-sulfenamide (DCBS) and / or benzothiazyl-2-sulfenomorpholide (MBS) and / or N-tert-butyl-2-benzothiazylsulfenamide (TBBS).In addition, the rubber mixture may contain vulcanization retarders.All sulfur-donating substances known to the skilled person can be used as sulfur-donating substance. If the rubber mixture contains a sulfur-donating substance, this is preferably selected from the group consisting of, for example, thiuram disulfides, such as, for example, tetrabenzylthiuram disulfide (TBzTD), tetramethylthiuram disulfide (TMTD) or tetraethylthiuram disulfide (TETD), thiuram tetrasulfides, such as, for example, dipentamethylenethiuram tetrasulfide (DPTT), dithiophosphates, such as, for example, DipDis (bis-(diisopropyl)thiophosphoryl disulfide), bis(O,O-2-ethylhexylthiophosphoryl)dithiophosphoryl)dithioamines (for example Rhenocure SDT 50 ®, Rheinchemie GmbH, Zinc dichlorodithiophosphate (e.g. Rhenocure ZDT / S ®, Rheinchemie GmbH) or zinc alkyldithiophosphate, and 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane and diaryl polysulfides and dialkyl polysulfides.Other network-forming systems, as are available, for example, under the trade names Vulkuren ®, Duralink ® or Perkalink ® or network-forming systems, as are described in WO 2010 / 049216 A2, can also be used in the rubber mixture. The latter system contains a vulcanization agent which crosslinks with a functionality greater than four and at least one vulcanization accelerator.During their production, at least one vulcanizing agent selected from the group consisting of sulfur, sulfur donors, vulcanization accelerators and vulcanizing agents which crosslink with a functionality of greater than four is preferably added to the rubber mixture in the finish mixing stage. As a result, a sulfur-crosslinked rubber mixture for use in rubber products, in particular in vehicle tires, can be produced from the mixed ready-to-use mixture by vulcanization.The terms "vulcanized" and "crosslinked" are used interchangeably within the scope of the present invention.The rubber mixture is produced by the process customary in the rubber industry, in which a masterbatch is first prepared in one or more mixing stages with all constituents other than the vulcanization system (sulfur and vulcanization-influencing substances). By adding the vulcanization system in a final mixing stage, the final mixture is produced. The finished mixture is further processed, for example, by an extrusion process and is brought into the corresponding shape. The further processing is then carried out by vulcanization, wherein sulfur crosslinking takes place on account of the vulcanization system added in the context of the present invention.The rubber mixture can be used for a wide variety of rubber products. It is preferably used for the production of pneumatic vehicle tires, such as passenger car, van, truck or two-wheeler tires, the rubber mixture forming at least that part of the tread which comes into contact with the roadway. However, the rubber mixture can also be used in other tires, such as solid tires and non-pneumatic tires. Similarly, use in the case of round renewal is possible.In the preferred embodiment of the pneumatic vehicle tire, the tread may be made of a single compound formed in accordance with the invention. However, pneumatic vehicle tires today frequently have a tread with a so-called cap / base construction. The term "cap" is understood here to mean that part of the tread which comes into contact with the roadway and is arranged radially on the outside (tread cap or tread cap). The term "base" is understood here to mean that part of the tread which is arranged radially on the inside and therefore does not come into contact with the roadway during driving operation or comes into contact with the roadway only at the end of tire life (lower tread part or tread base). In a pneumatic vehicle tire having such a cap / base construction, at least the rubber compound for cap is formed according to claim 1.The pneumatic vehicle tire according to the invention can also have a tread which consists of various tread mixtures arranged alongside one another and / or under one another (multi-component tread strips).In the production of the pneumatic vehicle tire, the mixture is brought as a ready-mix before vulcanization into the form of a tread, preferably at least into the form of a tread cap, and is applied as known in the production of the green vehicle tire. The tread, preferably at least the tread cap, can also be wound onto a tyre blank in the form of a narrow rubber compound strip.The invention includes all advantageous embodiments which are reflected, inter alia, in the patent claims. In particular, the invention also includes configurations which result from a combination of different features, for example of constituents of the rubber mixture, different gradations when preference is given to these features, with the result that the invention also covers a combination of a first feature which is referred to as "preferred" or, within the scope of an advantageous embodiment, a further feature which is referred to as "particularly preferred", for example.The invention will now be explained in more detail with reference to comparative and exemplary embodiments, which are summarized in Table 1. The comparative mixtures are marked V, the mixture according to the invention is marked E.The production of the mixture was carried out according to the methods customary in the rubber industry under customary conditions in three stages in a laboratory mixer in which, first, in the first mixing stage (basic mixing stage), all constituents except for the vulcanization system (sulfur and vulcanization-influencing substances) were mixed. In the second mixing stage, the base mixture was mixed again. By adding the vulcanization system in the third stage (finish mixing stage), the finish mixture was produced while mixing at 90 to 120° C.Subsequently, the loss factor tan δ (10%) of the mixture was determined by means of RPA (= "rubber process analyzer") in accordance with ASTM D6601 from the second elongation cycle at 1 Hz, 70° C. and 10% elongation in the vulcanized, conditioned state.Furthermore, test specimens were produced from all the mixtures by vulcanization under pressure at 160° C. for 20 minutes, and typical material properties for the rubber industry were determined with these test specimens by the test methods given below:Shore A hardness at room temperature according to ISO 868rebound elasticity at room temperature and 70° C. according to ISO 4662Stress value (modulus) at 300% elongation at room temperature according to ISO 37maximum loss factor tan δ max at 55° C. as maximum value over the strain sweep from dynamic mechanical measurement at a frequency of 10 Hz according to ISO 4664-1abrasion at room temperature according to DIN / ISO 4649The maximum loss factor tan δ max at 55° C. (Eplexor) and the loss factor tan δ (10%) by means of RPA can be correlated with the rolling resistance. A low loss factor tan δ max at 55° C. and a low loss factor tan δ (10%) by means of RPA stand for a low rolling resistance. A further indicator of the rolling resistance is rebound elasticity at 70° C. A high value correlates here with good rolling resistance performance. Table 1 Table 1Natural Rubberphr phr phr phr phr phr phr phr phr phr10101010high-cis BR aphr phr phr phr phr phr phr phr phr phr3030--low-cis BR bphr phr phr phr phr phr phr phr phr phr--7070SSBR cphr phr phr phr phr phr phr phr phr phr60602020mod. liquid BR dphr phr phr phr phr phr phr phr phr phr-8-8Liquid BR ephr phr phr phr phr phr phr phr phr phr12,512,512,512,5Carbon blackphr phr phr phr phr phr phr phr phr phr5555Silicaphr phr phr phr phr phr phr phr phr phr115115115115Silane coupling agent fphr phr phr phr phr phr phr phr phr phr8,28,28,28,2Resin gphr phr phr phr phr phr phr phr phr phr40404040Anti-ageing agents are anti-ageing agentsphr phr phr phr phr phr phr phr phr phr4444Anti-ozone waxphr phr phr phr phr phr phr phr phr phr2222Zinc oxidephr phr phr phr phr phr phr phr phr phr2222Stearic acid stearic acidphr phr phr phr phr phr phr phr phr phr1111Processing Aidphr phr phr phr phr phr phr phr phr phr6666Accelerator Acceleratorphr phr phr phr phr phr phr phr phr phr3,73,73,73,7Sulfurphr phr phr phr phr phr phr phr phr phr1,61,61,61,6PropertiesTg (blend)°C-73-73-81-81tan δ (10%)-0,2030,1870,2020,156Shore hardness at RTShore A63626162Rebound load at RT%20,623,426,032,2Rebound load at 70° C.%41,942,843,948,7Modulus: 300%MPa5,45,44,76,9tan δ max-0,2420,2180,2310,195Abrasion3 mm 3 mm57756634 a Buna CB 1203, Arlanxeo, T g= -105 ° C., cis fraction > 95% b Asaprene ® YB03, Asahi, functionalized, solution polymerized butadiene rubber with functionalization for the polymer / silica interaction, T g= -90 ° C., cis fraction = 38.6% c Sprintan ® SLR-3402, Trinseo, functionalized, solution polymerized styrene-butadiene copolymer with functionalization for the polymer / silica and the polymer / carbon black interaction, T g= -62 ° C. d Polyvest® EP ST-E 60, Evonik, liquid polybutadiene terminally modified with triethoxysilane, Tg=-80 ° C., average molar mass M w about. 13600 g / mol (GPC, polybutadiene standard) e Ricon® 130, Cray Valley, liquid polybutadiene, unmodified, Tg=-90° C., M w about. 6400 g / mol f bis(triethoxysilylpropyl) disulphide (TESPD), Si261® Evonik g Sylvatrix ®4401, Kraton Chemicals SAS, alpha-methyl styrene resin, softening point=85 °C (according to ASTM E 28)It is evident from the data of Table 1 that the combined presence of the solid, solution-polymerized butadiene rubber (BR, polybutadiene) having a cis fraction of 38.6% with 8 phr of the liquid polybutadiene, which is terminally modified with triethoxysilane and has an average molecular weight M w according to GPC of about 1360 g / mol, in the siliceous mixture 4(E) makes it possible to greatly reduce the loss factor tan δ (10%) as a measure of the rolling resistance. This effect was by no means to be expected from the individual measures as shown by mixtures 2(V) (only addition of the specific liquid BR) and 3(V) (only altered polymer system). The same applies to the tan δ max- value. Another indicator of the unexpectedly good rolling resistance is rebound at 70° C. At the same time, there is significantly reduced abrasion in the mixture 4(E). The durability of tires having such a compound as a tread is thereby greatly improved.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedEP 3 150 403 A1

[0004] EP 3 150 402 A1

[0004] EP 3 150 401 A1

[0004] DE 10 2015 218 745 A1

[0004] DE 10 2015 218 746 A1

[0004] US 2021347206 A1

[0005] US 2021230403 A1

[0005] WO2020218601 A1

[0006] WO 99 / 09036

[0034] WO 2008 / 083241 A1

[0034] WO 2008 / 083242 A1

[0034] WO 2008 / 083243 A1

[0034] WO 2008 / 083244 A1

[0034] US 20080161477 A1

[0034] EP 2 114 961 B1

[0034] WO 2010 / 049216 A2

[0045] Cited Non-Patent LiteratureDIN 53765:1994-03 and ISO 11357-2:1999-03

[0024]

Claims

Sulfur-crosslinkable rubber mixture, in particular for the tread of pneumatic vehicle tires, comprising at least the following constituents: - 50 to 100 phr (parts by weight, based on 100 parts by weight of the total rubbers in the mixture) of at least one solid, solution-polymerized butadiene rubber (BR) having a cis fraction of less than 90% by weight, - up to 20 phr of at least one natural polyisoprene (NR), - up to 40 phr of at least one solution-polymerized styrene-butadiene rubber (SSBR), - 1 to 40 phr of at least one liquid polybutadiene which is organosilicon-modified and has an average molecular weight M w according to GPC of 500 to 18000 g / mol, and - 10 to 300 phr of at least one silica.Sulfur-crosslinkable rubber mixture according to Claim 1, characterized in that the at least one solid, solution-polymerized butadiene rubber has a cis fraction of between 20 and 50% by weight.Sulfur-crosslinkable rubber mixture according to Claim 1 or 2, characterized in that the at least one solid, solution-polymerized butadiene rubber is functionalized with a group which permits interaction with the silica.Sulfur-crosslinkable rubber mixture according to at least one of the preceding claims, comprising at least the following constituents: - 60 to 95 phr of at least one solid, solution-polymerized butadiene rubber (BR) having a cis fraction of less than 90% by weight, - 5 to 15 phr of at least one natural polyisoprene (NR) and - 10 to 30 phr of at least one solution-polymerized styrene-butadiene rubber (SSBR).Sulfur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that the solid rubbers in the mixture together have a blend glass transition temperature Tg (blend) of -90 to -77°C.Sulfur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that it comprises 5 to 40 phr, preferably 10 to 30 phr, of at least one plasticizer which is not a mineral oil plasticizer.Sulfur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that the at least one plasticizer, which is not a mineral oil plasticizer, is a liquid polybutadiene without organosilicon modification and which has an average molecular weight M w according to GPC of 500 to 18000 g / mol.Sulfur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that it comprises 50 to 200 phr of silica.Sulfur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that it comprises 1-15 phf (parts by weight, based on 100 parts by weight of silica) of at least one silane coupling agent.Sulfur-crosslinkable rubber mixture according to Claim 9, characterized in that at least one silane coupling agent is 3,3'-bis(triethoxysilylpropyl) disulfide (TESPD).Sulfur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that it comprises 20 to 60 phr of at least one resin.Sulfur-crosslinkable rubber mixture according to Claim 11, characterized in that at least one resin is one based on isopropenylbenzene.Pneumatic vehicle tyre having a tread, the part of which at least coming into contact with the road consists of a rubber mixture vulcanized with sulphur according to one of Claims 1 to 12.