Rubber mixture and vehicle tyre

Abstract

The invention relates to a sulfur-crosslinkable rubber mixture, in particular for the tread of vehicle tyres, 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 polyisoprene, - up to 40 phr of at least one solution-polymerized styrene-butadiene rubber (SSBR), - 5 to 70 phr of at least one terpene resin based to an extent of more than 95% on biologically renewable raw materials, and - 10 to 300 phr of at least one silica.

Description

[0001] Description

[0002] Rubber compound and vehicle tires

[0003] The invention relates to a sulfur-crosslinkable rubber mixture, in particular for the tread of vehicle tires.

[0004] The invention further relates to a vehicle tire, in particular a pneumatic vehicle tire, with a tread which consists at least partially of such a rubber mixture vulcanized with sulfur.

[0005] Since the driving characteristics of a tire, especially pneumatic tires, depend to a large extent on the rubber composition of the tread, particularly high demands are placed on the composition of the tread compound. Numerous attempts have been made to positively influence the tire's properties by varying the polymer components, fillers, plasticizers, and other additives in the tread compound. It must be considered that an improvement in one tire property often results in a deterioration in another. For example, an improvement in rolling resistance is usually associated with a deterioration in braking and abrasion performance.

[0006] Tread compounds intended for use in winter or all-season tires must meet stringent requirements for braking performance on ice and snow, while at the same time ensuring that rolling resistance and other desired tire properties, such as wet and dry braking, cut-and-chip performance, durability, and handling, are not adversely affected.

[0007] To influence tire properties such as rolling resistance, it is known, for example, to use solution-polymerized styrene-butadiene copolymers with different microstructures. Diene rubbers can also be modified by end-group modification, coupling, or hydrogenation. The different copolymer types have different influences on the vulcanizate and thus also on the tire properties.

[0008] Functionalized diene elastomers for silicic acid rubber compounds 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.

[0009] Furthermore, US 2021347206 A1 and US 2021230403 A1 describe rubber mixtures for tire treads that contain butadiene rubber (polybutadiene, BR) with a low cis content.

[0010] To improve the balance between durability and hysteresis properties of rubber compounds for tire treads, WO 2020218601 A1 discloses mixtures with 70 phr styrene-butadiene copolymer (SSBR), 30 phr high-cis butadiene rubber (polybutadiene, BR), silica, vegetable oil, resin and 3,3'-bis(triethoxysilylpropyl)tetrasulfide (TESPT) as silane coupling agent.

[0011] EP 4 310 139 A1 describes rubber compounds containing 70 phr high-cis butadiene rubber (polybutadiene, BR), 10 phr NR, 20 phr SSBR, 12.5 phr rapeseed oil and 115 phr silica for improved rolling resistance combined with good handling and low abrasion.

[0012] The invention is based on the object of providing rubber mixtures for the treads of vehicle tires, in particular pneumatic vehicle tires, which lead to an improvement in the winter properties and rolling resistance of tires.

[0013] 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 components: 50 to 100 phr (parts by weight, based on 100 parts by weight of the total rubber in the mixture) 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 polyisoprene, up to 40 phr of at least one solution-polymerized styrene-butadiene rubber (SSBR),

[0014] 5 to 70 phr of at least one terpene resin based on more than 95% bio-renewable raw materials and 10 to 300 phr of at least one silica.

[0015] The term phr (parts per hundred parts of rubber by weight) used in this document is the standard quantity used in the rubber industry for compound formulations. 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 compound.

[0016] In the context of the present invention, the term “a terpene resin based on more than 95% biologically renewable raw materials” is to be understood as meaning a terpene resin which is materially produced from renewable raw materials as a source, with plant sources being particularly preferred.

[0017] Surprisingly, it has been found that the special combination of a solid, solution-polymerized butadiene rubber (BR, polybutadiene) with a cis content of less than 90 wt.% and a terpene resin based on more than 95% biorenewable raw materials, in the specified amounts, leads to an increase in rebound resilience at 70°C in siliceous mixtures after vulcanization. This increased rebound resilience at 70°C can be correlated with reduced rolling resistance when the mixture is used in tire treads. At the same time, the vulcanizates made from the mixture are characterized by lower dynamic stiffness, which equates to good braking performance on snowy and icy surfaces. The rubber mixture according to the invention is also characterized by improved sustainability due to the special terpene resin used.

[0018] The rubber mixture contains 50 to 100 phr of at least one solid, solution-polymerized butadiene rubber (BR) with a cis content of less than 90 wt.%, preferably with a cis content of between 20 and 50 wt.%. Multiple solution-polymerized butadiene rubbers can also be used.

[0019] All types of butadiene rubber (polybutadiene, BR) known to those skilled in the art that have a cis content of less than 90 wt.% can be used. These include the so-called low-cis types, with butadiene rubber with a cis content of less than 90 wt.% being referred to as a low-cis type. A low-cis butadiene rubber with a cis content of between 20 and 50 wt.%, e.g., Li-BR (lithium-catalyzed butadiene rubber), is preferably used.

[0020] According to a preferred embodiment of the invention, the solution-polymerized, functionalized butadiene rubbers are functionalized with a group that 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) that enable interaction with the silica. The functionalization can be with hydroxyl groups and / or ethoxy groups and / or epoxy groups and / or siloxane groups and / or aminosiloxane and / or carboxyl 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 part of the functionalizations.In addition to the functionalizations that enable interaction with silica, the butadiene rubber can also have further functionalizations that enable interactions with non-polar fillers, such as carbon black.

[0021] The rubber mixture according to the invention contains up to 20 phr of at least one polyisoprene. This can be either natural polyisoprene (NR) and / or synthetic polyisoprene (IR). Natural polyisoprene is understood to be rubber that can be obtained by harvesting sources such as rubber trees (Hevea brasiliensis) or non-rubber tree sources (such as guayule or dandelion (e.g., Taraxacum koksaghyz)). Natural polyisoprene (NR) is understood to mean non-synthetic polyisoprene.

[0022] Natural polyisoprenes from various sources can also be used in blends. The cis-1,4 content in natural polyisoprene is greater than 99 wt.%.

[0023] 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 rubbers can be end-group modified and / or functionalized along the polymer chains with a wide variety of functionalizations (modifications) that enable interaction with the silica. The functionalizations can be those with hydroxyl groups and / or ethoxy groups and / or epoxy groups and / or siloxane groups and / or aminosiloxane and / or carboxyl 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 part of the functionalizations.

[0024] In addition to the rubber types already mentioned, the rubber mixture may optionally contain other 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 polynorbornenes and / or isoprene-isobutylene copolymers and / or ethylene-propylene-diene rubbers. These rubbers can be used as pure rubbers or in oil-extended form.

[0025] For particularly low rolling resistance and low abrasion when used as a tire tread, it has proven advantageous if the rubber mixture contains at least

[0026] - 60 to 95 phr of at least one solid, solution-polymerized butadiene rubber (BR) with a cis content of less than 90 wt.%,

[0027] - 5 to 15 phr of at least one polyisoprene and

[0028] - 0 to 30 phr of at least one solution-polymerized styrene-butadiene rubber (SSBR).

[0029] The rubber mixture according to the invention contains 5 to 70 phr, preferably 20 to 60 phr, particularly preferably 30 to 50 phr, of at least one terpene resin based on more than 95% biorenewable raw materials. Several different terpene resins can also be used in the mixture. The terpene resin is preferably based 100% on biorenewable raw materials.

[0030] Terpene resins that are more than 95% based on renewable raw materials can be obtained, for example, from raw materials obtained during the production of fragrances from orange peels. However, the terpene resin is preferably based on byproducts from the pulp production of softwoods. Such byproducts are available in large quantities on the market and can be industrially refined into terpene resins. The terpene resins can be based on α- and / or β-pinene.

[0031] According to a preferred embodiment of the invention, the terpene resin is not based on limonene.

[0032] The terpene resin is preferably based on α-pinene. Such terpene resins can be produced from byproducts generated during the pulp production of softwoods. Such terpene resins are available, for example, as resins of the Sylvatraxx® 8000 series from Kraton Chemicals SAS.

[0033] The terpene resin, which is based on more than 95% biorenewable raw materials, preferably has an average molecular weight (Mw) according to GPC of 800 to 1500 g / mol. Such terpene resins are easy to process and exhibit good tensile properties.

[0034] According to a preferred embodiment of the invention, the terpene resin has a softening point of 100 to 140 °C, preferably 110 to 130 °C.

[0035] For good braking performance of the tire whose tread consists of the rubber mixture according to the invention, the terpene resin has a glass transition temperature Tg according to DSC of 50 to 100 °C, preferably 50 to 80 °C.

[0036] Terpene resins that can be used according to the invention include, for example, those of the type Sylvatraxx® 8115 and Sylvatraxx® 8125 from Kraton Chemicals SAS. These are based 100% on renewable raw materials and not on limonene.

[0037] 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.

[0038] A wide variety of silicas, such as low surface area or highly dispersible silica, can be used, even in mixtures. It is particularly preferred to use a finely dispersed, precipitated silica with a CTAB surface area (according to ASTM D 3765) of 30 to 350 m². 2 / g, preferably from 110 to 250 m 2 / g. Both conventional silicas such as type VN3 from Evonik and highly dispersible silicas, so-called HD silicas (e.g., Ultrasil® 7000 from Evonik), can be used as silicas. To improve processability and to bond the silica to the diene rubber in silica-containing mixtures, at least one silane coupling agent is preferably used in the rubber mixture in amounts of 1-15 phf (parts by weight, based on 100 parts by weight of silica). The silane coupling agents can also be used in the mixture.

[0039] The term phf (parts per hundred parts of filler by weight) used in this document is the quantity commonly used in the rubber industry for coupling agents used in fillers. In the context of this application, phf refers to the silica present, meaning that other fillers that may be present, such as carbon black, are not included in the calculation of the amount of silane coupling agent.

[0040] The silane coupling agents react with the surface silanol groups of the silica or other polar groups during mixing of the rubber or rubber mixture (in situ) or even before the addition of the filler to the rubber, in the sense of pretreatment (premodification). Silane coupling agents that can be used are all silane coupling agents known to the person skilled in the art for use in rubber mixtures. 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 have, as another functionality, a group that can, optionally after cleavage, 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, -NH2, or -Sx- (where x = 2-8). For example, silane coupling agents such as3-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, or mixtures of sulfides with 1 to 8 sulfur atoms with varying contents of the various sulfides, can be used. TESPT can also be added, for example, as a mixture with carbon black (trade name X50S from Degussa). Blocked mercaptosilanes, such as those known from WO 99 / 09036, can also be used as silane coupling agents. Silanes such as those described in WO 2008 / 083241 A1, WO 2008 / 083242 A1, WO 2008 / 083243 A1, and WO 2008 / 083244 A1 can also be used. Examples include silanes marketed under the name NXT® in various versions by Momentive, USA, or those marketed under the name VP Si 363 by Evonik Industries.So-called “silated core polysulfides” (SCP, polysulfides with a silylated core) can also be used, which are described, for example, in US 20080161477 A1 and EP 2 114 961 B1.

[0041] Preferably, at least one silane coupling agent in the rubber mixture is 3,3'-bis(triethoxysilylpropyl) disulfide (TESPD).

[0042] The rubber mixture may also contain other fillers, such as carbon black, aluminosilicates, chalk, starch, magnesium oxide, titanium dioxide, rubber gels, carbon nanotubes, graphite, graphene or so-called “carbon-silica dual-phase fillers” in usual quantities, whereby the fillers can be used in combination.

[0043] If the rubber mixture contains carbon black, all types of carbon black known to those skilled in the art can be used. However, preference is given to using a carbon black that 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 m 1 / 100 g, preferably 100 to 200 m 1 / 100 g, particularly preferably 100 to 180 ml / 100 g. This achieves particularly good rolling resistance indicators for use in vehicle tires, along with good other tire properties.

[0044] To further improve the winter properties of the compound, the rubber compound according to the invention preferably contains 5 to 40 phr of at least one plasticizer that is not a mineral oil plasticizer. It is possible to use one plasticizer or several plasticizers in combination.

[0045] A wide variety of plasticizers other than mineral oil plasticizers can be used, such as vegetable oils, factises, or liquid polymers with a weight-average molecular weight distribution (Mw) according to GPC of 60,000 g / mol or less, such as liquid polybutadiene. The plasticizer(s) are preferably added in at least one basic mixing stage during the production of the rubber mixture according to the invention.

[0046] According to an advantageous development of the invention, a vegetable oil, such as sunflower oil, linseed oil, rapeseed oil, or similar, is used as the plasticizer. This is advantageous from an ecological and economic perspective and offers advantageous properties in tires. It is particularly preferred if the vegetable oil is rapeseed oil.

[0047] In addition to the aforementioned plasticizers, the rubber mixture may also contain mineral oil plasticizers. Mineral oil plasticizers that can be used include all mineral oil plasticizers known to the person skilled in the art, such as aromatic, naphthenic, or paraffinic mineral oil plasticizers, such as MES (mild extraction solvate) or RAE (residual aromatic extract) or TDAE (treated distillate aromatic extract), preferably with a polycyclic aromatics content of less than 3 wt. % according to method IP 346. However, the rubber mixture according to the invention is preferably free of mineral oil plasticizers.

[0048] Furthermore, the rubber mixture can contain customary additives in customary parts by weight, which are preferably added in at least one basic mixing stage during its production. These additives include a) ageing inhibitors, 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) or zinc complexes such as zinc ethylhexanoate, c) waxes, d) other resins, such as tackifier resins, e) mastication aids, such as B. 2,2'-dibenzamidodiphenyl disulfide (DBD), and f) processing aids, such as fatty acid salts, such as zinc soaps, and fatty acid esters and their derivatives.

[0049] The proportion of the total amount of other additives is 3 to 150 phr, preferably 3 to 100 phr and particularly preferably 5 to 80 phr.

[0050] The vulcanization of the rubber compound is carried out in the presence of sulfur and / or sulfur donors using vulcanization accelerators, whereby some vulcanization accelerators can also act 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.

[0051] Preference is given to using a sulfenamide accelerator selected from the group consisting of N-cyclohexyl-2-benzothiazolesufenamide (CBS) and / or N,N-dicyclohexylbenzothiazole-2-sulfenamide (DCBS) and / or benzothiazyl-2-sulfenemorpholide (MBS) and / or N-tert-butyl-2-benzothiazylsulfenamide (TBBS).

[0052] The rubber compound may also contain vulcanization retarders.

[0053] Any sulfur-donating substance known to the person 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 consisting of, for example, thiuram disulfides, such as tetrabenzylthiuram disulfide (TBzTD), tetramethylthiuram disulfide (TMTD) or tetraethylthiuram disulfide (TETD), thiuram tetrasulfides, such as, for example,

[0054] Dipentamethylenethiuram tetrasulfide (DPTT), dithiophosphates such as DipDis (bis-(diisopropyl)thiophosphoryl disulfide), bis(O,O-2-ethylhexylthiophosphoryl)polysulfide (e.g. Rhenocure SDT 50®, Rheinchemie GmbH), zinc dichloryldithiophosphate (e.g. Rhenocure ZDT / S®, Rheinchemie GmbH) or zinc alkyldithiophosphate, and 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane and diarylpolysulfides and dialkylpolysulfides.

[0055] 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. The latter system contains a vulcanizing agent that crosslinks with a functionality greater than four and at least one vulcanization accelerator.

[0056] During the final mixing stage, at least one vulcanizing agent selected from the group consisting of sulfur, sulfur donor, vulcanization accelerator, and vulcanizing agents that crosslink with a functionality greater than four is preferably added to the rubber mixture during its production. This allows the mixed final mixture to be vulcanized to produce a sulfur-crosslinked rubber mixture for use in rubber products, particularly vehicle tires.

[0057] The terms “vulcanized” and “crosslinked” are used synonymously in the context of the present invention.

[0058] The rubber compound is produced according to a process commonly used in the rubber industry, in which a base compound containing all components except the vulcanization system (sulfur and vulcanization-influencing substances) is first prepared in one or more mixing stages. The finished compound is created by adding the vulcanization system in a final mixing stage. The finished compound is further processed, for example, by an extrusion process, and formed into the appropriate shape. Further processing then takes place by vulcanization, with sulfur crosslinking occurring due to the vulcanization system added within the scope of the present invention.

[0059] The rubber compound can be used for a wide variety of rubber products. It is primarily used for the production of pneumatic vehicle tires, such as car, van, truck, or two-wheeler tires, where the rubber compound forms at least the part of the tread that comes into contact with the road surface. However, the rubber compound can also be used in other tires, such as solid tires and non-pneumatic tires. It can also be used in retreading.

[0060] In the preferred embodiment of the pneumatic vehicle tire, the tread can consist of a single compound formed according to the invention. However, pneumatic vehicle tires today often have a tread with a so-called cap / base construction. The term "cap" refers to the part of the tread that comes into contact with the road surface and is arranged radially on the outside (upper tread section or tread cap). The term "base" refers to the part of the tread that is arranged radially on the inside and thus does not come into contact with the road surface during driving or only at the end of the tire's life (lower tread section or tread base). In a pneumatic vehicle tire with such a cap / base construction, at least the rubber compound for the cap is designed according to claim 1.

[0061] The pneumatic vehicle tire according to the invention can also have a tread consisting of different tread compounds arranged side by side and / or one below the other (multi-component tread).

[0062] During the production of the pneumatic vehicle tire, the mixture is formed as a ready-mixed compound into the shape of a tread, preferably at least into the shape of a tread cap, prior to vulcanization and is applied during the production of the green vehicle tire as known in the art. The tread, preferably at least the tread cap, can also be wound onto a green tire in the form of a narrow strip of rubber compound.

[0063] The invention encompasses all advantageous embodiments, which are reflected, inter alia, in the patent claims. In particular, the invention also encompasses embodiments that result from the combination of different features, for example, components of the rubber mixture, with varying degrees of preference for these features, so that a combination of a first feature designated as "preferred" or described within the scope of an advantageous embodiment with another feature designated, for example, as "particularly preferred" is also encompassed by the invention.

[0064] The invention will now be explained in more detail using comparative and exemplary embodiments, which are summarized in Table 1.

[0065] The comparison mixtures are marked with V, the mixture according to the invention is marked with E.

[0066] The compound was manufactured according to standard rubber industry procedures under standard conditions in three stages in a laboratory mixer. In the first mixing stage (basic mixing stage), all components except the vulcanization system (sulfur and vulcanization-influencing substances) were mixed. In the second mixing stage, the base mixture was thoroughly mixed again. The final mixture was created by adding the vulcanization system in the third stage (final mixing stage), which was mixed at 90 to 120 °C.

[0067] Subsequently, the loss factor tan δ (10%) of the compound was determined using an RPA (rubber process analyzer) based on ASTM D6601 from the second elongation run at 1 Hz, 70°C, and 10% elongation in the vulcanized, conditioned state. Furthermore, test specimens were prepared from all compounds by vulcanization under pressure at 160°C for 20 minutes. These specimens were used to determine material properties typical for the rubber industry using the test methods specified below:

[0068] - Shore A hardness at room temperature according to ISO 868

[0069] - Rebound resilience at room temperature and 70 °C according to ISO 4662

[0070] - Tensile strength (modulus) at 300% elongation at room temperature according to ISO 37

[0071] - Tensile strength at room temperature according to ISO 37

[0072] - Elongation at break at room temperature according to ISO 37

[0073] - dynamic storage modulus E' at -15 °C and a strain of 0.15% (E'(0.15%)) from dynamic mechanical measurement based on ISO 4664-1, strain sweep at a pre-compression of 20%, a frequency of 10 Hz and a strain range between 0.15% and 8%

[0074] The loss factor tan δ (10%) measured using RPA can be correlated with rolling resistance. A low loss factor tan δ (10%) measured using RPA indicates low rolling resistance.

[0075] Another indicator of rolling resistance is the rebound resilience at 70°C. A high value correlates with good rolling resistance performance. The dynamic storage modulus E' at -15°C can serve as an indicator of suitability for braking on icy and snowy surfaces, thus indicating good winter performance. The lower the dynamic storage modulus E' at -15°C, the better the winter performance.

[0076] Table 1 a llbepol BR® 150, Ube Corporation, cobalt-catalyzed, T g = -105 °C, cis content > 95 % b Asaprene® YB03, Asahi, functionalized, solution-polymerized butadiene rubber with functionalization for the polymer / silica interaction, T g = -90 °C, cis content = 38.6 % c Sprintan® SLR-3402, Trinseo, functionalized, solution-polymerized styrene-butadiene copolymer with functionalization for the polymer / silica and polymer / carbon black interaction, T g = -59 °C d ZEOSIL® 1165 MP, Solvay SA, BET surface area = 155 m 2 / g (measured with nitrogen), CTAB surface area = 156-157 m 2 / G; e 3, 3'-Bis(triethoxysilylpropyl) disulfide (TESPD) f Sylvatraxx® 4401 , Kraton Chemicals SAS, Alpha-Methyl-Styrene resin, softening point = 85 °C (according to ASTM E 28), T g= 45 °C s Sylvatraxx® 8115, Kraton Chemicals SAS, non-limonene-based terpene resin (based on a-pinene), softening point = 115 °C (according to ASTM E 28), T g = 66 °C

[0077] The data in Table 1 demonstrates that the combined presence of solid, solution-polymerized butadiene rubber (BR, polybutadiene) with a cis content of 38.6% and a terpene resin based on more than 95% biorenewable raw materials in the siliceous mixture 4(E) significantly reduces the dynamic storage modulus E' at -15 °C, an indicator of improved winter properties. This effect was by no means to be expected from the individual measures, as demonstrated by mixtures 2(V) (only addition of the special terpene resin) and 3(V) (only modified polymer system). This is especially true since a calculated glass transition temperature for mixture 3(V) also yielded the lowest value, so that the expert would have expected the best winter properties for mixture 3(V).

[0078] The effect of the individual measures also exceeds the expected effect of the loss factor tan δ (10%) and the rebound resilience at 70 °C as a measure of rolling resistance. Both values ​​change when the two measures interact in a way that the individual measures would not have predicted. Tires with a tread made of compound 4(E) are therefore characterized by improved winter performance with low rolling resistance.

Claims

Patent claims 1. Sulphur-crosslinkable rubber mixture, in particular for the tread of vehicle tires, containing at least the following components: - 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-polymerised butadiene rubber (BR) with a cis content of less than 90% by weight, - up to 20 phr of at least one polyisoprene, - up to 40 phr of at least one solution-polymerised styrene-butadiene rubber (SSBR), - 5 to 70 phr of at least one terpene resin based on more than 95% bio-renewable raw materials and - 10 to 300 phr of at least one silica.

2. Sulphur-crosslinkable rubber mixture according to claim 1, characterized in that the at least one solid, solution-polymerized butadiene rubber has a cis content of between 20 and 50 wt.%.

3. 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 enables interaction with the silica.

4. Sulphur-crosslinkable rubber mixture according to at least one of the preceding claims, containing at least the following components: - 60 to 95 phr of at least one solid, solution-polymerized Butadiene rubber (BR) with a cis content of less than 90 wt.%, - 5 to 15 phr of at least one polyisoprene and - 0 to 30 phr of at least one solution-polymerized styrene-butadiene rubber (SSBR).

5. Sulphur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that it contains 20 to 60 phr, preferably 30 to 50 phr, of at least one terpene resin based to more than 95% on biologically renewable raw materials.

6. Sulphur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that the terpene resin is based 100% on biologically renewable raw materials.

7. Sulphur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that the terpene resin is not based on limonene.

8. Sulphur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that the terpene resin is based on a-pinene.

9. Sulphur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that the terpene resin has an average molecular weight Mw according to GPC of 800 to 1500 g / mol.

10. Sulphur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that the terpene resin has a softening point of 100 to 140 °C, preferably 110 to 130 °C.

11. Sulphur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that it contains 50 to 200 phr of silica.

12. Sulphur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that it contains 1 - 15 phf (parts by weight, based on 100 parts by weight of silica) of at least one silane coupling agent.

13. Sulphur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that it contains 5 to 40 phr of at least one plasticizer which is not a mineral oil plasticizer.

14. Sulphur-crosslinkable rubber mixture according to at least one of the preceding claims, characterized in that the plasticizer is a vegetable oil, preferably rapeseed oil.

15. Vehicle tyres, in particular pneumatic vehicle tyres, with a tread whose part at least coming into contact with the road surface consists of a sulphur-vulcanised rubber mixture according to one of claims 1 to 14.

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