Sulfur-crosslinkable rubber mixture and vehicle tire

Abstract

The invention relates to a sulfur-crosslinkable rubber mixture and to a vehicle tire. The sulfur-crosslinkable rubber mixture contains: - at least one diene rubber; - 10 to 500 phr silicic acid; - at least one organosilicon compound of the general formula (I), where R is the same or different and H is a cyclic, straight-chain or branched C1 to C12, preferably C1 to C8, more preferably C1, alkyl group, a carboxyl group (-COOH), a substituted or unsubstituted aryl group, preferably a phenyl group, or a substituted or unsubstituted aralkyl group, R' is the same or different and is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic / aromatic bivalent C1-C30, preferably C1-C20, more preferably C2-C20, most preferably C3-C15, hydrocarbon group, and x is an average chain length of 1 to 10; - 0.5-5 phr zinc stearate; and - less than 0.5 phr of a vulcanization accelerator selected from the group of the guanidines and aldehydamines.

Description

[0001] 202402850

[0002] 1

[0003] Description

[0004] Sulfur-crosslinkable rubber compound and vehicle tires

[0005] The invention relates to a sulfur-curable rubber compound and a vehicle tire, in particular a pneumatic vehicle tire, with at least one component consisting of such a sulfur-vulcanized rubber compound.

[0006] Since the driving characteristics of a tire, especially a pneumatic vehicle tire, depend to a large extent on the rubber composition of the tread, particularly high demands are placed on the composition of the tread compound. This creates conflicting objectives between most of the known tire properties, such as wet grip, braking performance, handling, rolling resistance, winter performance, abrasion resistance, and tear resistance. Numerous attempts have already been made to positively influence the tire's properties by varying the polymer components, fillers, and other additives in the tread compound. It must be considered, however, that an improvement in one tire property often leads to a deterioration in another.

[0007] Silica, also known as silicic acid, is a filler that has been used for many years in rubber compounds to reduce the rolling resistance of vehicle tires. Silica is typically used in combination with a silane coupling agent in rubber compounds to improve the processability of the compound and to enable the silica to bond to the surrounding diene rubber.

[0008] The silane coupling agents react with the surface silanol groups of 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). Such coupling agents known from the prior art are bifunctional organosilanes, which have at least one alkoxy group on the silicon atom.

[0009] 2

[0010] These compounds possess a cycloalkoxy or phenoxy group as a leaving group and, as a secondary functional group, a group that, if cleaved, can undergo a chemical reaction with the polymer's double bonds. This latter group can be, for example, the following chemical groups: -SCN, -SH, -NH2, or -Sx- (where x = 2-8). Thus, silane coupling agents can 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, or mixtures of the sulfides with 1 to 8 sulfur atoms and varying concentrations of the different sulfides. The mercaptosilanes can also be used in block form. B. as 3-octanoylthiopropyltriethoxysilane.

[0011] Many silane coupling agents used in the rubber industry have ethoxy or methoxy groups as leaving groups, which release ethanol or methanol, respectively, during the production of the rubber compound. These silane coupling agents include, for example, 3,3'-bis(triethoxysilylpropyl)polysulfides with 2 to 8 sulfur atoms or 3-octanoylthiopropyltriethoxysilane. For environmental reasons, efforts are being made to reduce the emission of volatile organic compounds (VOCs).

[0012] For this purpose, for example, the alternative silane coupling agent of formula II is available. A silane coupling agent is available, which is marketed by Evonik under the name Si 466™ EXT, for example. However, this silane coupling agent greatly accelerates the vulcanization rate, which can lead to processing problems.

[0013] From DE 10 2006 004 062 A1, it is known to provide a rubber mixture with silatrans, such as those of Form II, which is characterized by very good vulcanization behavior. In addition to rubber, silatran, and filler, the rubber mixture contains certain quantities and types of vulcanization accelerators, wherein less than 1.5 phr of secondary accelerators, selected from the group of guanidines and aldehyde amines, are present in the mixture.

[0014] The present invention is based on the objective of providing a rubber compound that, compared to the prior art, exhibits improved vulcanization behavior with low emission of volatile organic compounds. At the same time, properties of the rubber compound that are advantageous for use in tires should not be impaired or should even be further enhanced.

[0015] This task is solved by a sulfur-crosslinkable rubber compound containing

[0016] - at least one diene rubber,

[0017] - 10 to 500 phr silica,

[0018] - at least one organosilicon compound of general formula I

[0019] - where R is the same or different and H is a cyclic, straight-chain or branched Ci to C12, preferably Ci to Cs, particularly preferably Ci, -alkyl group, a carboxyl group (-COOH), a substituted or unsubstituted aryl group, preferably a phenyl group, or a substituted or unsubstituted aralkyl group,

[0020] R' the same or different and a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic / aromatic divalent C1-C30, preferably C1-C20, particularly 202402850

[0021] 4 preferably C2-C20, most preferably Cs-Cis hydrocarbon group, x is an average chain length of 1 to 10,

[0022] - 0.5 - 5 phr zinc stearate and

[0023] - less than 0.5 phr of a vulcanization accelerator selected from the group of guanidines and aldehydes.

[0024] Surprisingly, it has been found that combining specific organosilicon compounds according to formula I as silane coupling agents with small amounts of vulcanization accelerators from the guanidine and aldehyde group, but simultaneously with 0.5 to 5 phr of zinc stearate in the mixture, further improves the vulcanization behavior. At the same time, the organosilicon compounds according to formula I release no or very few volatile organic compounds, thus offering environmental advantages.

[0025] The compounds according to the invention are also characterized by advantageous vulcanizate properties. When used in vehicle tires, these vulcanizate properties lead to improved rolling resistance and improved braking performance.

[0026] 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 parts by weight of each substance is always based on 100 parts by weight of the total mass of all solid rubber components present in the mixture.

[0027] The unit pph (parts per hundred parts of filler by weight) used in this document is the quantity commonly used in the rubber industry for coupling agents for polar fillers. In the context of this application, pph refers to the silica / silica present, meaning that other fillers that may be present, such as carbon black, are not included in the calculation of the quantity of silane coupling agent. 202402850

[0028] 5

[0029] According to the invention, the rubber mixture contains at least one diene rubber. 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.

[0030] The diene rubber(s) is / are preferably selected from the group consisting of natural polyisoprene (NR), synthetic polyisoprene (IR), epoxidized polyisoprene (ENR), butadiene rubber (BR), butadiene-isoprene rubber, styrene-butadiene rubber (SBR), in particular solution-polymerized styrene-butadiene rubber (SSBR) and emulsion-polymerized styrene-butadiene rubber (ESBR), styrene-isoprene rubber, liquid rubbers with a molecular weight Mw of greater than 20,000 g / mol, halobutyl rubber, polynorbornene, isoprene-isobutylene copolymer, ethylene-propylene-diene rubber, nitrile rubber, chloroprene rubber, acrylate rubber. Fluorocarbon rubber, silicone rubber, polysulfide rubber, epichlorohydrin rubber, styrene-isoprene-butadiene terpolymer, hydrogenated acrylonitrile butadiene rubber and hydrogenated styrene-butadiene rubber.

[0031] According to a particularly preferred embodiment of the invention, the diene rubber(s) is / are selected from the group consisting of natural polyisoprene (NR), synthetic polyisoprene (IR), butadiene rubber (BR), solution-polymerized styrene-butadiene rubber (SSBR), and emulsion-polymerized styrene-butadiene rubber (ESBR). Such a rubber compound is particularly suitable for the tread of vehicle tires.

[0032] Natural polyisoprene is understood to be rubber that can be obtained by harvesting from sources such as rubber trees (Hevea brasiliensis) or non-rubber tree sources (such as guayule or dandelion (e.g., Taraxacum koksaghyz)). Natural polyisoprene (NR) refers to non-synthetic polyisoprene. 202402850

[0033] 6

[0034] All types of butadiene rubber (polybutadiene, BR) known to those skilled in the art can be used, both high-cis and low-cis types. Butadiene rubbers can also be used in functionalized form. These butadiene rubbers can be end-group modified and / or functionalized along the polymer chains with a wide variety of functionalizations. These functionalizations can include hydroxy groups, ethoxy groups, epoxy groups, siloxane groups, aminosiloxane groups, carboxy groups, and / or silane sulfide groups. Other modifications and functionalizations known to those skilled in the art are also possible. Different functionalizations can be present at the ends of the chain. Metal atoms can also be part of the functionalizations. Different butadiene rubbers can be blended together.

[0035] If solution-polymerized styrene-butadiene rubbers (SSBRs) are present in the rubber compound, they can be functionalized with a wide variety of modifications, including end-group modifications and / or functionalizations along the polymer chains. These functionalizations can involve hydroxy groups, ethoxy groups, epoxy groups, siloxane groups, aminosiloxane groups, carboxy groups, and / or silane sulfide groups. Other modifications and functionalizations known to a qualified professional are also possible. Different functionalizations may also be present at the ends of the polymer chains. Metal atoms may also be incorporated into the functionalizations.

[0036] The rubber compound according to the invention contains 10 to 500 phr, preferably 50 to 200 phr, silica to achieve good processability with good tire properties.

[0037] The silicic acids that can be used can be based on a wide variety of silicic acids, which are produced, for example, by precipitation from the liquid phase or pyrogenically or 202402850

[0038] 7. They are produced from rice husk ash (“rice husk ash silica” (RHAS)). Precipitated silica is preferably used.

[0039] Various types of silica, such as low surface area or highly dispersible silica, can be used, even in mixtures. It is particularly preferred to use 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 270 m 2 / g. Both conventional silicas such as those of type VN3 from Evonik and highly dispersible silicas, so-called HD silicas (e.g. Ultrasil® 7000 from Evonik), can be used as silicas.

[0040] The rubber compound according to the invention contains at least one organosilicon compound of general formula I where R is the same or different and H is a cyclic, straight-chain or branched Ci to C12, preferably Ci to Cs, particularly preferably Ci, -alkyl group, a carboxyl group (-COOH), a substituted or unsubstituted aryl group, preferably a phenyl group, or a substituted or unsubstituted aralkyl group,

[0041] R' is the same or different and is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic / aromatic dicovalent C1-C30, preferably C1-C20, particularly preferably C2-C20, most preferably Cs-Cis hydrocarbon group, x is a mean chain length of 1 to 10.

[0042] R' can be, for example, CH2, CH2CH2, CH2CH2CH2, CH2CH2CH2CH2, CH(CH3), CH2CH(CH3), CH(CH3)CH2, C(CH3)2, CH(C2H5), CH2CH2CH(CH3), CH(CH3)CH2CH2, CH2CH(CH3)CH2 or 202402850 mean.

[0043] Organosilicon compounds of general formula I can be used as mixtures of organosilicon compounds of general formula I. The compounds can also have different x values ​​within the mixture.

[0044] The index x represents the average sulfur chain length in the substance mixture and can be 1.1 to 5, preferably 1.5 to 4.5, particularly preferably 3 to 4 or 1.8 to 3, and most preferably 3.5 to 3.8 or 1.9 to 2.6. The proportion of S₂ compounds in mixtures of the organosilicon compounds of general formula I can be more than 50 wt.%, preferably more than 60 wt.%, particularly preferably more than 70 wt.%, and most preferably more than 80 wt.%, based on the amount of organosilicon compound of general formula I used. The proportion of S₃ compounds in mixtures of the organosilicon compounds of general formula I can be 0.5 to 60 wt.%, preferably 1 to 50 wt.%, particularly preferably 1 to 45 wt.%, and most preferably 1 to 40 wt.%, based on the amount of organosilicon compound of general formula I used.The proportion of S4 compounds in mixtures of organosilicon compounds of general formula I can be more than 0.5 wt.%, preferably more than 5 wt.%, particularly preferably more than 9 wt.%, very preferably more than 15 wt.%, and extraordinarily preferably more than 25 wt.%, based on the amount of organosilicon compound of general formula I used.

[0045] For particularly good vulcanization behavior combined with good tire properties, it has proven advantageous if the rubber compound contains at least one organosilicon compound of general formula II: 202402850

[0046] 9 where x is an average chain length from 1 to 10.

[0047] Silatrans of this type are available, for example, under the name SI466™ EXT from the company Evonik.

[0048] The organosilicon compounds of formula I can be used in varying amounts in the rubber mixture.

[0049] According to a preferred embodiment of the invention, the rubber compound contains 4 to 12 pphf at least one organosilicon compound of general formula II. Very good results with such compounds have been achieved with regard to processing behavior and tire properties, wet grip and rolling resistance.

[0050] The rubber compound according to the invention contains 0.5 - 5 phr, preferably 1 to 3 phr, zinc stearate.

[0051] The rubber compound according to the invention contains less than 0.5 phr, preferably less than 0.1 phr, of a vulcanization accelerator selected from the group of guanidines and aldehydes.

[0052] The vulcanization accelerators selected from the group of guanidines and aldehydeamines can be, for example, diphenylguanidine, di-o-tolylguanidine, o-tolylbiguanidine, N,N'-diphenylguanidine, hexamethylenetetramine, condensation products of homologous acroleins with aromatic bases or condensation products of aldehydes with amines.

[0053] Such vulcanization accelerators are present in the mixture only in very small quantities or not at all.

[0054] In addition to the ingredients already mentioned, the rubber mixture may contain further additives, which are listed below.

[0055] The rubber compound may contain further fillers such as carbon black, aluminosilicates, chalk, starch, magnesium oxide, titanium dioxide, rubber gels, carbon nanotubes, 202402850

[0056] 10

[0057] Contains graphite, graphene or so-called "carbon-silica dual-phase filler" in typical quantities, and the fillers can be used in combination.

[0058] If carbon black is present in the rubber compound, all types of carbon black known to those skilled in the art can be used. However, a carbon black is preferably used that has an iodine adsorption value according to ASTM D 1510 of 30 to 180 g / kg, preferably 30 to 130 g / g, and a DBP value 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 results in particularly good rolling resistance indicators for use in vehicle tires, along with good other tire properties.

[0059] The rubber compound according to the invention may further contain various plasticizers. These are preferably present in quantities of up to 70 phr in the compound.

[0060] Suitable plasticizers include those selected from the group consisting of plasticizers derived from renewable raw materials such as rapeseed oil or sunflower oil, mineral oils, phosphate esters such as tri(2-ethylhexyl) phosphate, and liquid polymers with a weight-average molecular weight distribution (Mw) according to GPC of 60,000 g / mol or less. Preferably, DAE (distilled aromatic extracts), RAE (residual aromatic extract), TDAE (treated distilled aromatic extracts), MES (mild extracted solvents), rapeseed oil, and / or liquid diene polymers are used.

[0061] Furthermore, the rubber compound may contain common additives in common proportions by weight, which are preferably added in at least one basic mixing stage during its manufacture. 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), 202402850

[0062] 11 b) Activators, such as zinc oxide and fatty acids (e.g. stearic acid) or zinc complexes such as zinc ethylhexanoate, c) resins, such as terpene resins, d) mastication aids, such as 2,2'-dibenzamidodiphenyl disulfide (DBD), and e) processing aids.

[0063] 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.

[0064] The vulcanization of the rubber compound 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, and / or xanthate accelerators. If vulcanization accelerators from the group of guanidines and aldehydes are used, their quantity must not exceed 0.5 phr according to the invention.

[0065] Preferably, a sulfenamide accelerator is used which is 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).

[0066] Furthermore, the rubber compound may contain vulcanization retarders.

[0067] 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 consisting of, for example, thiuram disulfides, such as tetrabenzylthiuram disulfide (TBzTD), tetramethylthiuram disulfide (TMTD) or tetraethylthiuram disulfide (TETD), thiuram tetrasulfides, such as 202402850

[0068] 12

[0069] Dipentamethylenethiuramtetrasulfide (DPTT), dithiophosphates, such as DipDis (bis-(diisopropyl)thiophosphoryldisulfide), bis(O,O-2-ethylhexyl-thiophosphoryl)polysulfide (e.g., Rhenocure SDT 50®, Rheinchemie GmbH), zinc dichloroyldithiophosphate (e.g., Rhenocure ZDT / S®, Rheinchemie GmbH) or zinc alkyldithiophosphate, and 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane and diarylpolysulfides and dialkylpolysulfides.

[0070] 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.

[0071] The rubber compound is produced according to standard rubber industry processes, in which a base mixture containing all components except the vulcanization system (sulfur and vulcanization-influencing substances) is prepared in one or more mixing stages. The finished compound is then produced by adding the vulcanization system in a final mixing stage. This finished compound is further processed, for example, by extrusion, and formed into the desired shape. Subsequent processing is carried out by vulcanization, whereby sulfur crosslinking occurs due to the vulcanization system added according to the present invention.

[0072] The rubber compound can be used for a wide variety of rubber products.

[0073] Preferably, it is used in vehicle tires, in particular pneumatic vehicle tires, with at least one component consisting of the sulfur-vulcanized rubber compound according to the invention. It can also be used in several different components of vehicle tires. Within the scope of the present invention, vehicle tires are defined as pneumatic vehicle tires.

[0074] 13 and solid rubber tires, including tires for industrial and construction vehicles, truck, car and two-wheeler tires.

[0075] Preferably, it is a vehicle pneumatic tire, such as a car, van, truck or two-wheeler tire with a tread, the part of which comes into contact with the road surface consists of the sulfur-vulcanized rubber compound according to the invention.

[0076] In a pneumatic tire, the tread can consist of a single compound designed according to the invention. However, modern pneumatic tires often feature a tread with a so-called cap / base construction. The "cap" refers to the part of the tread that comes into contact with the road surface and is located radially outside (tread cap). The "base" refers to the part of the tread that is located radially inside and therefore does not come into contact with the road surface during operation, or only at the end of the tire's service life (tread base). In a pneumatic tire with such a cap / base construction, at least the rubber compound for the cap is designed according to claim 1.

[0077] The vehicle pneumatic tire according to the invention can also have a tread consisting of different tread compounds arranged next to and / or one above the other (multi-component tread).

[0078] In the manufacture of the vehicle tire, the compound is formed as a ready-mixed mixture into the shape of a tread strip, preferably at least into the shape of a tread cap, before vulcanization and applied to the vehicle tire blank in a known manner. The tread strip, preferably at least the tread cap, can also be wound onto a tire blank in the form of a narrow strip of rubber compound. 202402850

[0079] 14

[0080] The rubber compound according to the invention is also suitable for other components of vehicle tires, such as, in particular, the rim profile, as well as for inner tire components. 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.

[0081] The invention encompasses all advantageous embodiments, which are reflected, inter alia, in the claims. In particular, the invention also encompasses embodiments resulting from the combination of different features, for example, components of the rubber compound, and different degrees of preference given to these features, such that a combination of a first feature designated as "preferred" or described within the framework of an advantageous embodiment with a further feature designated, for example, as "particularly preferred," is also covered by the invention.

[0082] The invention will now be explained in more detail with reference to comparative and exemplary embodiments, which are summarized in Tables 1 and 2.

[0083] The comparison mixture is marked with V, the mixture according to the invention is marked with E.

[0084] The compound was prepared according to standard rubber industry procedures under typical 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.

[0085] The Mooney viscosity of the mixtures was determined according to ASTM D1646; e.g. ML1 +4 at 100 °C (Mooney units ME).

[0086] The mixtures were evaluated with respect to their turnover times of 10% turnover (tio vulcanization time), 40% turnover (t4o) and 90% turnover (too, 202402850).

[0087] 15

[0088] vulcanization time) was investigated using a rotorless vulcanometer (MDR = Moving Disc Rheometer) according to ASTM D5289 and ISO 6502.

[0089] Furthermore, test specimens were produced from all mixtures by optimal vulcanization under pressure at 160 °C and the material properties typical for the rubber industry were determined using these test specimens with the test procedures specified below:

[0090] - Shore A hardness at room temperature according to ISO 868

[0091] - Rebound elasticity at room temperature and 70 °C according to ISO 4662 - Stress value (modulus) at 100, 200 and 300 % elongation at room temperature according to ISO 37

[0092] - Tensile strength at room temperature according to ISO 37

[0093] - Elongation at break at room temperature according to ISO 37. A low rebound elasticity at room temperature can be correlated with good wet grip when the compound is used in the treads of vehicle pneumatic tires, whereas a high rebound elasticity at 70 °C suggests low rolling resistance.

[0094] 202402850

[0095] 16

[0096] Table 1 a Sprintan® SLR-4602, Trinseo, functionalized, solution-polymerized styrene-butadiene copolymer with functionalization for polymer / silica and polymer / carbon black interactions, T g = -23 °C b Sprintan® SLR-3402, Trinseo, functionalized, solution-polymerized styrene-butadiene copolymer with functionalization for polymer / silica and polymer / carbon black interactions, T g = -59 °C c Ultrasil® VN3 Evonik, BET surface area = 167-193 m² 2 / g (measured with nitrogen), CTAB surface area = 157-177 m² 2 / G; d TDAE (Treated Distilled Aromatic Extracts) e 3,3'-Bis(triethoxysilylpropyl)disulfide (TESPD), Si 266®, Evonik 202402850

[0097] 17 f Si 466™, Evonik, with 15 m% SSBR

[0098] 9 N-Cyclohexyl-2-benzothiazole sufenamide (vulcanization accelerator) h N-(Cyclohexylthio)phthalimide (vulcanization retarder)

[0099] Table 2

[0100] The data in Tables 1 and 2 show that replacing the conventional silane coupling agent TESPD (see 1(V)) with an organosilicon compound of general formula I, namely a silatran according to formula II (see 2(V)), leads to a significant reduction in vulcanization times, which is accompanied by processing problems. To slow down vulcanization, a secondary accelerator such as DPG can be omitted (see 3(V)); however, this simultaneously reduces the rebound elasticity at 70 °C, which correlates with an increase in rolling resistance when used as a tire tread. The addition of slightly more stearic acid (see 4(V)) or of N-202402850

[0101] 18

[0102] (Cyclohexylthio)phthalimide (CTP) as a vulcanization retarder (see 5(V)) has only a minor effect on the vulcanization rate, and even with these compounds, the rebound elasticity at 70 °C decreases, indicating a deterioration in rolling resistance. In contrast, a compound with the special Silatran in combination with 2 phr zinc stearate without DPG (see 6(E)) surprisingly leads to significantly longer vulcanization times, comparable to those of compound 1(V). Furthermore, there is a large difference between the rebound elasticity at room temperature and the rebound elasticity at 70 °C, suggesting a significantly improved performance profile with regard to wet grip and rolling resistance when used in tires.

[0103] Mixture 6(E) thus enables the provision of a mixture with lower emission of volatile organic substances, good vulcanization behavior and improved wet grip and rolling resistance property profile.

Claims

202402850 19 Patent claims 1. Sulfur-curable rubber compound, containing - at least one diene rubber, - 10 to 500 phr silica, - at least one organosilicon compound of general formula I - wherein R is the same or different and H is a cyclic, straight-chain or branched Ci to C12, preferably Ci to Cs, particularly preferably Ci, -alkyl group, a carboxyl group (-COOH), a substituted or unsubstituted aryl group, preferably a phenyl group, or a substituted or unsubstituted aralkyl group, R' is the same or different and is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic / aromatic dicovalent C1-C30, preferably C1-C20, particularly preferably C2-C20, most preferably Cs-Cis hydrocarbon group, x is an average chain length of 1 to 10, - 0.5 - 5 phr zinc stearate and - less than 0.5 phr of a vulcanization accelerator selected from the group of guanidines and aldehydes.

2. Sulfur-curable rubber compound according to claim 1, characterized in that it contains at least one organosilicon compound of general formula II: 202402850 20 where x is an average chain length of 1 to 10.

3. Sulfur-crosslinkable rubber compound according to claim 2, characterized in that it contains 4 to 12 pphf of at least one organosilicon compound of general formula II.

4. Sulfur-curable rubber compound according to at least one of the preceding claims, characterized in that it contains 1 to 3 phr zinc stearate.

5. Sulfur-curable rubber compound according to at least one of the preceding claims, characterized in that it contains less than 0.1 phr of a vulcanization accelerator selected from the group consisting of guanidines and aldehydeamines.

6. Sulfur-curable rubber compound according to at least one of the preceding claims, characterized in that it contains 50 to 200 phr silica.

7. Sulfur-curable rubber compound according to at least one of the preceding claims, characterized in that the diene rubber(s) is / are selected from the group consisting of natural polyisoprene (NR), synthetic polyisoprene (IR), butadiene rubber (BR), solution-polymerized styrene-butadiene rubber (SSBR), emulsion-polymerized styrene-butadiene rubber (ESBR), butyl rubber (HR) and halobutyl rubber.

8. Vehicle tires, in particular pneumatic vehicle tires, comprising at least one component consisting of a sulfur-vulcanized rubber compound according to any one of claims 1 to 7. 202402850 21 9. Vehicle pneumatic tire according to claim 8 with a tread, the part of which comes into contact with the road surface at least consists of a sulfur-vulcanized rubber compound according to one of claims 1 to 7.

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