Sulfur-crosslinkable rubber compound, vulcanized rubber compound, and vehicle tires

Description

[0001] The invention relates to a sulfur-crosslinkable rubber mixture, its vulcanizate, and a vehicle tire. Furthermore, the invention relates to a process for producing the sulfur-crosslinkable rubber mixture and the use of the sulfur-crosslinkable rubber mixture.

[0002] It is known that anti-aging agents are added to rubber compounds for vehicle tires and other technical rubber products. Antioxidants, including polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, play a particularly important role. Commercially available 2,2,4-trimethyl-1,2-dihydroquinoline, abbreviated to TMQ, exists as an oligomer mixture, with the anti-aging properties being achieved primarily through the dimer and trimer.

[0003] The disadvantage of anti-aging agents is that they can bloom and thus cause discoloration of the rubber articles.

[0004] EP 3517570 A1 discloses the use of the age-protecting agent N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD) in combination with an oligomer mixture of 2,2,4-trimethyl-1,2-dihydroquinoline, the mixture containing 61 wt.% of dimers and trimers of 2,2,4-trimethyl-1,2-dihydroquinoline.

[0005] Such an anti-aging system is intended to improve blooming behavior and crack resistance. At the same time, other tire properties, such as handling, wet grip, abrasion, and rolling resistance, are also expected to be improved.

[0006] When comparing the mixtures containing either a mixture containing 35 wt.% of dimers and trimers of TMQ or a mixture containing 61 wt.% of dimers and trimers of TMQ with otherwise identical components, no influence on the rolling resistance is observed.

[0007] JP 6642067 B2 discloses a rubber mixture containing 100 phr of natural rubber (NR) and, among other ingredients, an oligomer mixture of 2,2,4-trimethyl-1,2-dihydroquinoline, wherein the mixture contains 70 to 97 wt. % of dimers and trimers of 2,2,4-trimethyl-1,2-dihydroquinoline. According to JP 6642067 B2, this is intended to prevent the conversion of insoluble sulfur into soluble sulfur, thus improving steel cord adhesion by preventing sulfur blooming, combined with good processability and heat resistance.

[0008] The object of the present invention was to provide a rubber mixture which, compared to the prior art, has a further improvement in rolling resistance behavior and handling behavior, in particular a higher stiffness.

[0009] The object is achieved by the sulfur-crosslinkable rubber mixture according to claim 1 and the process for producing a sulfur-crosslinkable rubber mixture according to claim 13.

[0010] It was also an object of the present invention to provide a vulcanizate and a vehicle tire which have improved rolling resistance behavior and handling behavior.

[0011] This object is achieved by the vulcanizate according to claim 10 and the vehicle tire according to claim 11.

[0012] Furthermore, it was an object of the present invention to provide technical rubber articles, such as bellows, conveyor belts, air springs, belts, straps or hoses, as well as shoe soles, which are characterized by an improvement in handling behavior and heat build-up.

[0013] This object is achieved by using the sulfur-crosslinkable rubber mixture according to the invention for producing the technical rubber articles mentioned.

[0014] Surprisingly, the rubber mixture according to the invention comprising a combination of a) 30 to 95 phr of at least one butadiene rubber and c) 0.1 to 3.0 phr of an oligomer mixture of TMQ, wherein the mixture contains 70 to 100 wt. % of dimers and trimers of TMQ, exhibits a further improvement in heat build-up and thus in rolling resistance behavior as well as in stiffness and thus in handling behavior compared to the prior art.

[0015] It is also a particular advantage of the present invention that the amount of oligomer mixture of TMQ used can be reduced, in particular halved, while at the same time the rolling resistance of the rubber mixture is improved and the aging behavior remains the same, and thus the oligomer mixture shows a comparable effect in a reduced, in particular halved, amount.

[0016] According to some embodiments, surprisingly improved tear properties, in particular improved fatigue resistance, in particular against cracking and possibly fracture, are also obtained after aging.

[0017] The invention encompasses all advantageous embodiments, which are reflected, among other things, 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 different 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.

[0018] The components of the sulfur-crosslinkable rubber mixture according to the invention are described in more detail below.

[0019] All information on the components of the rubber mixture according to the invention, regardless of the degree of preference given to these features, also applies accordingly to the process according to the invention for producing the sulfur-crosslinkable rubber mixture, as well as to the vulcanizate according to the invention, the vehicle tire according to the invention and the use according to the invention.

[0020] 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 in this document is based on 100 parts by weight of the total mass of all rubbers present in the compound with a molecular weight Mw according to GPC of greater than 20,000 g / mol.

[0021] According to the invention, the rubber mixture contains a) 30 to 95 phr of at least one butadiene rubber (= BR, polybutadiene). In principle, this can be any type known to the person skilled in the art. These include, among others, the so-called high-cis and low-cis types, with polybutadiene with a cis content greater than or equal to 90% being referred to as the high-cis type and polybutadiene with a cis content less than 90% being referred to as the low-cis type. An example of a low-cis polybutadiene is Li-BR (lithium-catalyzed butadiene rubber) with a cis content of 20 to 50%. With a high-cis BR, particularly good properties and low hysteresis of the rubber mixture are achieved.

[0022] It is therefore preferred that the at least one butadiene rubber a) has a cis-1,4 content of 90 to 98%, preferably 94 to 98%.

[0023] The figures in % refer to the monomers of the polymer chain of polybutadiene.

[0024] The cis-part of the polybutadiene is determined by 13< C-NMR (125.77 MHz; relaxation agent Cr(acac) 3 ; solvent CDCl 3 , Bruker 500 MHz).

[0025] The rubber mixture preferably contains 40 to 95 phr, particularly preferably 50 to 95 phr of at least one butadiene rubber.

[0026] In particular with an increased amount of at least one butadiene rubber, such as in particular 50 to 95 phr, the object underlying the invention is achieved particularly well.

[0027] The polybutadiene(s) used can be end-group modified and / or functionalized along the polymer chains. The modifications can include hydroxyl groups, ethoxy groups, epoxy groups, siloxane groups, amino groups, aminosiloxane, carboxyl groups, phthalocyanine groups, and / or silane sulfide groups. Metal atoms can also be part of the functionalizations.

[0028] According to the invention, the sulfur-crosslinkable rubber mixture b) contains 5 to 70 phr of at least one further rubber, in particular a further type of rubber.

[0029] It is clear to the person skilled in the art that the sum of the rubbers used, as already explained above, is 100 phr, so that the amount of further rubber or further rubbers in the case of 40 to 95 phr, particularly preferably 50 to 95 phr, of at least one butadiene rubber, correspondingly amounts to 5 to 60 phr, particularly preferably 5 to 50 phr.

[0030] The additional rubber b) can in principle be any type of rubber known to the person skilled in the art.

[0031] However, it is preferred that the at least one further rubber b) is at least a diene rubber.

[0032] Such a rubber compound is particularly suitable for vehicle tires, especially for their outer components.

[0033] Diene rubbers are rubbers that are produced 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.

[0034] The further diene rubber is preferably selected from the group consisting of natural polyisoprene (NR), synthetic polyisoprene (IR), epoxidized polyisoprene (ENR), 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 M w of greater than 20,000 g / mol, halobutyl rubber, polynorbornene, isoprene-isobutylene copolymer, ethylene-propylene-diene rubber, nitrile rubber, chloroprene rubber, acrylate rubber, fluororubber, silicone rubber, Polysulfide rubber, epichlorohydrin rubber, styrene-isoprene-butadiene terpolymer, hydrogenated acrylonitrile-butadiene rubber and hydrogenated styrene-butadiene rubber.

[0035] In particular, nitrile rubber, hydrogenated acrylonitrile-butadiene rubber, chloroprene rubber, butyl rubber, halobutyl rubber, or ethylene-propylene-diene rubber are used in the production of technical rubber articles, such as belts, straps, and hoses, and / or shoe soles. The preferred blend compositions for these rubbers—specific with regard to fillers, plasticizers, vulcanization systems, and additives—are known to those skilled in the art.

[0036] The natural and / or synthetic polyisoprene can be either cis-1,4-polyisoprene or 3,4-polyisoprene. However, the use of cis-1,4-polyisoprenes with a cis-1,4 content of > 90% is preferred. Such a polyisoprene can be obtained by stereospecific polymerization in solution with Ziegler-Natta catalysts or using finely divided lithium alkyls. Natural rubber (NR) is a cis-1,4-polyisoprene in which the cis-1,4 content in the natural rubber is greater than 99 wt.%.

[0037] Furthermore, a mixture of one or more natural polyisoprenes with one or more synthetic polyisoprene(s) is also conceivable.

[0038] For the purposes of the present invention, the term "natural rubber" refers to naturally occurring rubber that can be obtained from Hevea rubber trees and non-Hevea sources. Non-Hevea sources include, for example, guayule shrubs and dandelions such as TKS (Taraxacum kok-saghyz; Russian dandelion).

[0039] If at least one styrene-butadiene rubber (styrene-butadiene copolymer) is present in the rubber mixture, it can be either solution-polymerized styrene-butadiene rubber (SSBR) or emulsion-polymerized styrene-butadiene rubber (ESBR), although a mixture of at least one SSBR and at least one ESBR can also be used. The terms "styrene-butadiene rubber" and "styrene-butadiene copolymer" are used synonymously in the context of the present invention.

[0040] The styrene-butadiene copolymer used can be end-group modified with the modifications / functionalizations mentioned above for polybutadiene and / or modified along the polymer chains.

[0041] Particularly preferably, the diene rubber is selected from the group consisting of natural polyisoprene (NR) and synthetic polyisoprene (IR) and styrene-butadiene rubber (SBR), wherein the styrene-butadiene rubber is preferably selected from SSBR.

[0042] According to advantageous embodiments of the invention, the rubber mixture contains a) 30 to 95 phr of at least one butadiene rubber and b) 5 to 70 phr of at least one styrene-butadiene rubber (SBR), wherein the styrene-butadiene rubber is preferably selected from SSBR.

[0043] According to further advantageous embodiments of the invention, the rubber mixture contains a) 30 to 95 phr of at least one butadiene rubber and b) 5 to 70 phr of at least one styrene-butadiene rubber (SBR), wherein the styrene-butadiene rubber is preferably selected from SSBR, and at least one polyisoprene selected from natural polyisoprene (NR) and synthetic polyisoprene (IR), wherein at least one natural polyisoprene is preferred. According to these embodiments of the invention, the rubber mixture thus contains at least three different polymers, particularly preferably BR, NR, and SSBR.

[0044] According to particularly advantageous embodiments of the invention, the rubber mixture contains a) 30 to 95 phr of at least one butadiene rubber and b) 5 to 70 phr of at least one polyisoprene selected from natural polyisoprene (NR) and synthetic polyisoprene (IR), with at least one natural polyisoprene being preferred.

[0045] According to particularly advantageous embodiments of the invention, the rubber mixture contains a) 40 to 60 phr, preferably 45 to 55 phr, in particular 50 phr, of at least one butadiene rubber and b) 40 to 60 phr, 45 to 55 phr, in particular 50 phr, of at least one natural polyisoprene (NR). This surprisingly results in better rolling resistance properties and improved tear properties, in particular improved fatigue resistance, especially against cracking and possibly fracture, after aging.

[0046] According to particularly advantageous embodiments of the invention, the rubber mixture contains 5 to 40 phr of natural polyisoprene (NR) as rubber b). This achieves the object underlying the invention particularly well, and the rubber mixture exhibits optimal processability and optimal other properties, in particular tear properties and abrasion behavior.

[0047] According to particularly advantageous embodiments of the invention, the sulfur-crosslinkable rubber mixture contains a) 60 to 80 phr of at least one butadiene rubber and b) 20 to 40 phr of at least one natural polyisoprene (NR). The sum of the amounts of rubbers a) and b) preferably amounts to 100 phr.

[0048] Otherwise, it is clear to the expert's understanding that in the case of a mixture containing, for example, 60 phr of butadiene rubber (BR) and 20 phr of natural rubber (NR), 20 phr of one or more other rubbers are also included, so that the total is 100 phr.

[0049] According to the invention, the sulfur-crosslinkable rubber mixture c) contains 0.1 to 3.0 phr of an oligomer mixture of 2,2,4-trimethyl-1,2-dihydroquinoline, wherein the mixture contains 70 to 100 wt.% of dimers and trimers of 2,2,4-trimethyl-1,2-dihydroquinoline.

[0050] As already mentioned above, 2,2,4-trimethyl-1,2-dihydroquinoline is also abbreviated as "TMQ".

[0051] 2,2,4-trimethyl-1,2-dihydroquinoline, which is commercially available as an anti-aging agent, is polymerized as described above, with the dimer and the trimer being identified as the active components in the anti-aging agent.

[0052] According to the general understanding of the field, an "oligomer" is a molecule that is made up of "few" (Greek "oligos" = few) parts (Greek "meros" = part).

[0053] The oligomer mixture c) contained in the rubber mixture according to the invention contains as oligomers at least dimers and trimers of TMQ.

[0054] The oligomer mixture c) preferably contains 73 to 100 wt.%, preferably 74 to 100 wt.%, particularly preferably 74 to 95 wt.%, very particularly preferably 74 to 85 wt.%, of dimers and trimers of 2,2,4-trimethyl-1,2-dihydroquinoline.

[0055] This solves the problem underlying the invention particularly well.

[0056] In case the oligomer mixture contains less than 100 wt.% of dimers and trimers of 2,2,4-trimethyl-1,2-dihydroquinoline, further substances are contained in the mixture.

[0057] The other substances include in particular by-products with reduced anti-aging activity, in particular tetramers and higher homologues, aniline, isopropylidene bisaniline, the monomer 2,2,4-trimethyl-1,2-dihydroquinoline.

[0058] The oligomer mixture preferably contains the substance isopropylidene bisaniline in an amount of less than 0.05 wt.%, more preferably less than 0.02 wt.%, particularly preferably less than 0.01 wt.%, again preferably 0 to 0.0099 wt.%.

[0059] This solves the problem underlying the invention particularly well.

[0060] The oligomer mixture preferably contains the monomer 2,2,4-trimethyl-1,2-dihydroquinoline in an amount of less than 0.7 wt.%, more preferably 0 to 0.5 wt.%.

[0061] This solves the problem underlying the invention particularly well.

[0062] The rubber mixture preferably contains the oligomer mixture c) in an amount of 0.2 to 3 phr, particularly preferably 0.2 to 2.5 phr, very particularly preferably 0.4 to 2.2 phr.

[0063] With such preferred, particularly preferred and very particularly preferred amounts, the object underlying the invention is achieved particularly well. This results in, in particular, improved

[0064] Rolling resistance properties with the same anti-aging effect.

[0065] The rubber mixture d) preferably contains at least one filler, preferably in amounts of 20 to 500 phr, particularly preferably 20 to 400 phr, again preferably 20 to 180 phr, very particularly preferably 45 to 180 phr.

[0066] Preferably, the filler is a reinforcing filler, which is preferably selected from the group consisting of carbon black and silicon dioxide.

[0067] According to advantageous embodiments, the rubber mixture according to the invention contains 20 to 500 phr, particularly preferably 20 to 400 phr, again preferably 20 to 180 phr, very particularly preferably 45 to 180 phr, of at least one carbon black.

[0068] The at least one carbon black is preferably selected from industrial carbon blacks and pyrolysis carbon blacks, with industrial carbon blacks being more preferred.

[0069] All types of soot known to the expert can be used as soot.

[0070] The carbon black preferably has an iodine number according to ASTM D 1510, which is also referred to as iodine adsorption number, between 30 and 250 g / kg, preferably 30 to 180 g / kg, more preferably 40 to 180 g / kg, and most preferably 40 to 130 g / kg, and a DBP number according to ASTM D 2414 of 30 to 200 ml / 100 g, preferably 70 to 200 ml / 100 g, more preferably 90 to 200 ml / 100 g.

[0071] The DBP number according to ASTM D 2414 determines the specific absorption volume of a carbon black or a light filler using dibutyl phthalate.

[0072] The use of such a type of carbon black in the rubber compound, especially for vehicle tires, ensures the best possible compromise between abrasion resistance and heat build-up, which in turn influences the ecologically relevant rolling resistance.

[0073] Particularly suitable and preferred is a carbon black with an iodine adsorption number between 80 and 110 g / kg and a DBP number of 100 to 130 ml / 100g, such as in particular carbon blacks of type N339.

[0074] According to advantageous embodiments, the rubber mixture according to the invention contains 20 to 500 phr, particularly preferably 20 to 400 phr, again preferably 20 to 180 phr, of at least one silicon dioxide.

[0075] The silicon dioxide is preferably amorphous silicon dioxide, for example, precipitated silica, also known as precipitated silicon dioxide. Alternatively, pyrogenic silicon dioxide, for example, can also be used. However, it is particularly preferred to use a finely divided, precipitated silica which has a nitrogen surface area (BET surface area) (according to DIN ISO 9277 and DIN 66132) of 35 to 400 m² / g, preferably of 35 to 350 m² / g, particularly preferably of 85 to 320 m² / g and very particularly preferably of 120 to 235 m² / g, and a CTAB surface area (according to ASTM D 3765) of 30 to 400 m² / g, preferably of 30 to 330 m² / g, particularly preferably of 80 to 300 m² / g and very particularly preferably of 115 to 200 m² / g. Such silicas lead, for example, to particularly good physical properties of the vulcanizates in rubber mixtures for tire treads.Furthermore, this can result in advantages in compound processing due to a reduction in mixing time while maintaining consistent product properties, leading to improved productivity. Silicas that can be used include, for example, Ultrasil®< VN3 (trade name) from Evonik as well as highly dispersible silicas, so-called HD silicas (e.g., Zeosil®< 1165 MP from Solvay).

[0076] Silica obtained from the residue of rice husk combustion can also be used.

[0077] The rubber mixture may also contain additional fillers that may or may not have a reinforcing effect.

[0078] Other (non-reinforcing) fillers within the scope of the present invention include aluminosilicates, kaolin, chalk, starch, magnesium oxide, titanium dioxide or rubber gels as well as fibers (such as aramid fibers, glass fibers, carbon fibers, cellulose fibers).

[0079] Other potentially reinforcing fillers include carbon nanotubes (CNTs) including discrete CNTs, so-called hollow carbon fibers (HCFs) and modified CNTs containing one or more functional groups, such as hydroxyl, carboxy, and carbonyl groups), graphite and graphene, and so-called "carbon-silica dual-phase fillers."

[0080] Zinc oxide is not considered a filler in the context of the present invention.

[0081] Furthermore, the rubber mixture may contain conventional additives in the usual parts by weight, which are preferably added in at least one basic mixing stage during its production. These additives include e) other age-protecting agents, such as diamines, such as N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditolyl-p-phenylenediamine (DTPD), N-(1,4-dimethylpentyl)-N'-phenyl-p-phenylenediamine (7PPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and / or substituted bisphenols, such as 2,2'-methylenebis(4-methyl-6-tert-butylphenol) (BPH), and / or substituted phenols, such as butylhydroxytoluene (BHT), f) activators, such as zinc oxide and fatty acids (e.g. stearic acid) and / or other activators, such as zinc complexes, such aszinc ethylhexanoate, g) activators and / or agents for the bonding of fillers, in particular carbon black or silicon dioxide, such as, for example, S-(3-aminopropyl)thiosulphuric acid and / or its metal salts (bonding to carbon black) and silane coupling agents (bonding to silicon dioxide, in particular silicic acid), h) ozone protection waxes, i) resins, in particular phenolic resins, in particular as adhesive resins, j) mastication aids, such as, for example, 2,2'-dibenzamidodiphenyl disulfide (DBD) and k) processing aids, such as, in particular, fatty acid esters and metal soaps, such as, for example, zinc soaps and / or calcium soaps l) plasticizers, in particular aromatic, naphthenic or paraffinic mineral oil plasticizers, such as, for example, B. MES (Mild Extraction Solvate) or RAE (Residual Aromatic Extract) or TDAE (Treated Distillate Aromatic Extract), or Rubber-to-Liquid oils (RTL) or Biomass-to-Liquid oils (BTL), preferably with a polycyclic aromatics content of less than 3% by weight.-% according to method IP 346 or triglycerides, such as rapeseed oil, or factices or hydrocarbon resins or liquid polymers whose average molecular weight (determined by GPC = gel permeation chromatography, based on BS ISO 11344:2004) is between 500 and 20,000 g / mol.

[0082] When using mineral oil, it is preferably selected from the group consisting of DAE (Distilled Aromatic Extracts), RAE (Residual Aromatic Extract), TDAE (Treated Distilled Aromatic Extracts), MES (Mild Extracted Solvents) and naphthenic oils.

[0083] According to advantageous embodiments of the invention, the sulfur-crosslinkable rubber mixture e) contains at least one further ageing inhibitor, particularly preferably selected from the group of diamines, such as N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD).

[0084] According to advantageous embodiments of the invention, the sulfur-crosslinkable rubber mixture contains further age-protecting agents e) in an amount of 0.5 to 4 phr, particularly preferably 0.5 to 2.5 phr.

[0085] According to advantageous embodiments of the invention, the sulfur-crosslinkable rubber mixture contains no further ageing inhibitor, in particular 0 phr of diamines, such as N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD).

[0086] The silane coupling agents can be any type known to the person skilled in the art.

[0087] Furthermore, one or more different silane coupling agents can be used in combination. The rubber compound can thus contain a mixture of different silanes.

[0088] The silane coupling agents react with the surface silanol groups of the silicon dioxide, in particular the silica, or other polar groups during the mixing of the rubber or the rubber mixture (in situ) or even before the addition of the filler to the rubber in the sense of a pretreatment (premodification).

[0089] 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, optionally 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 to 8).

[0090] For example, 3-mercaptopropyltriethoxysilane, 3-thiocyanatopropyltrimethoxysilane, or 3,3'-bis(triethoxysilylpropyl)polysulfides with 2 to 8 sulfur atoms, such as 3,3'-bis(triethoxysilylpropyl)tetrasulfide (TESPT), the corresponding disulfide (TESPD), or mixtures of sulfides with 1 to 8 sulfur atoms with varying 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 Evonik).

[0091] 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 of suitable silanes include those sold under the name NXT in various variants by Momentive, USA, such as 3-octanoylthio-1-propyltriethoxysilane, or those sold under the name VP Si 363 ® by Evonik Industries.

[0092] The proportion of the total amount of further additives is preferably 3 to 150 phr, particularly preferably 3 to 100 phr and most preferably 5 to 80 phr.

[0093] The total amount of other additives may contain zinc oxide (ZnO) in the amounts stated above.

[0094] These can be any type of zinc oxide known to those skilled in the art, such as ZnO granules or powder. The conventionally used zinc oxide generally has a BET surface area of ​​less than 10 m² / g. However, a zinc oxide with a BET surface area of ​​10 to 100 m² / g, such as so-called "nano-zinc oxides," can also be used.

[0095] The rubber mixture according to the invention is preferably used in vulcanized form, in particular in vehicle tires or other vulcanized technical rubber articles.

[0096] The terms "vulcanized" and "crosslinked" are used synonymously in the context of the present invention.

[0097] The vulcanization of the rubber mixture according to the invention is preferably 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, mercapto accelerators, sulfenamide accelerators, thiocarbamate accelerators, thiuram accelerators, thiophosphate accelerators, thiourea accelerators, xanthate accelerators, and guanidine accelerators. Preference is given to using at least one sulfenamide accelerator selected from the group consisting of N-cyclohexyl-2-benzothiazolesufenamide (CBS), N,N-dicyclohexylbenzothiazole-2-sulfenamide (DCBS), benzothiazyl-2-sulfenemorpholide (MBS), N-tert-butyl-2-benzothiazylsulfenamide (TBBS), N-tert-butyl-2-benzothiazolesulfenimide (TBSI), and / or at least one guanidine accelerator, such as diphenylguanidine (DPG).

[0098] In particular, two or more accelerators can be used.

[0099] All sulfur-donating substances known to the person skilled in the art can be used as sulfur-donating substances.

[0100] Furthermore, the rubber mixture may contain one or more

[0101] Reversion inhibitors such as 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane, hexamethylene-1,6-bis(thiosulfate) disodium salt dihydrate, and / or tetrabenzylthiuram disulfide (TBzTD) can be used.

[0102] In addition, vulcanization retarders may be present in the rubber compound.

[0103] Otherwise, the rubber compound is manufactured according to the process commonly used in the rubber industry, in which a base compound containing all components except the vulcanization system (e.g., sulfur and vulcanization-influencing substances) is first produced in one or more mixing stages. The finished compound is created by adding the vulcanization system in a final mixing stage.

[0104] The finished mixture is further processed, for example, by an extrusion process or calendering, and brought into the appropriate shape.

[0105] The rubber mixture according to the invention is particularly suitable for use in vehicle tires, especially pneumatic vehicle tires. Application is conceivable in principle in all tire components, especially in an outer component, particularly and preferably in the flange profile, tread, and / or sidewall. In the case of a tread with a cap / base construction, the rubber mixture according to the invention is preferably used at least in the cap.

[0106] For use in vehicle tires, the mixture is formed as a ready-mix into the appropriate shape, preferably a horn profile, a sidewall and / or a tread, before vulcanization and is applied as known during the production of the vehicle tire blank.

[0107] The rubber mixture according to the invention for use as a body compound in vehicle tires is produced as already described. The difference lies in the shaping after the extrusion process or calendering of the mixture. The resulting shapes of the still unvulcanized rubber mixture for one or more different body compounds are then used to construct a green tire.

[0108] The term "body compound" refers to the rubber compounds for the other components of a tire, such as the separator plate, inner liner (inner layer), apex, belt, shoulder, belt profile, carcass, bead reinforcement, bead profile, and bandage. For use of the rubber compound according to the invention in belts and straps, especially conveyor belts, the extruded, still unvulcanized compound is formed into the appropriate shape and is often provided with reinforcements, e.g., synthetic fibers or steel cords, either during or after the process.

[0109] The material is then further processed by vulcanization.

[0110] As already stated at the outset, the present invention also relates to a vulcanizate which is obtained by sulfur vulcanization of at least one rubber mixture according to the invention, including all preferred features.

[0111] As already stated at the outset, a further subject matter of the present invention is also a vehicle tire which has at least one vulcanizate according to the invention including all preferred features in at least one component.

[0112] For the purposes of the present invention, vehicle tires are understood to mean pneumatic vehicle tires and solid rubber tires, including tires for industrial and construction vehicles, truck, car and two-wheel tires.

[0113] A vehicle tire according to the invention is preferred which has at least one vulcanizate according to the invention including all preferred features in at least one outer component, preferably in the horn profile, tread and / or the sidewall.

[0114] A further subject of the present invention, as already stated at the outset, is also a process for producing the sulfur-crosslinkable rubber mixture according to the invention, including all preferred features, comprising at least the following process steps: X1) Providing a) 30 to 95 phr of at least one butadiene rubber; and X2) Providing b) 5 to 70 phr of at least one further rubber; and X3) Providing c) 0.1 to 3.0 phr of an oligomer mixture of 2,2,4-trimethyl-1,2-dihydroquinoline, wherein the mixture contains 70 to 100 wt. % of dimers and trimers of 2,2,4-trimethyl-1,2-dihydroquinoline; and X4) Mixing the components from steps X1), X2) and X3), where the data in phr refer to 100 parts by weight of the total mass of all rubbers in the sulfur-curable rubber mixture produced.

[0115] Preferably, the mixing according to step X4) takes place in at least one basic mixing stage.

[0116] A further subject matter of the present invention, as already stated at the outset, is the use of the sulfur-crosslinkable rubber mixture according to the invention, including all preferred features, for the production of technical rubber articles, such as bellows, conveyor belts, air springs, belts, straps or hoses, as well as shoe soles.

[0117] The invention will now be explained in more detail using comparative and exemplary embodiments summarized in the following tables. All quantities in the tables are given in phr unless otherwise stated. Substances used

[0118] 1) High-cis butadiene rubber, Co-BR, cis-1,4 content 95% 2) Mixture TMQ: 43 wt.% of dimers and trimers of 2,2,4-trimethyl-1,2-dihydroquinoline, 0.1 wt.% isopropylidene bis aniline, 1.0 wt.% monomer 2,2,4-trimethyl-1,2-dihydroquinoline; Vulkanox ®< , Lanxess 3) Mixture TMQ: 75.5 wt.% of dimers and trimers of 2,2,4-trimethyl-1,2-dihydroquinoline, less than 0.01 wt.% isopropylidene bis aniline, 0.5 wt.% monomer 2,2,4-trimethyl-1,2-dihydroquinoline; Sirantech ™< S-TMQ, Jiangsu Sinorgchem Technology 4) Oil-extended sulfur: 33 wt.% oil, 67 wt.% sulfur 5) Silica: Zeosil ®< 1165MP, Solvay 6) Silane: Si 266 ®< , Evonik, contains TESPD (bis[3-triethoxysilyl)propyl]disulfide) 7) Steel cord adhesion system: sum of cobalt stearate, resorcinol precondensate and hexamethoxymethylmelamine resin (HMMM-65%) 8) Silica: Ultrasil ®< VN 3 GR, Evonik 9) Hydrocarbon resin OPPERA PR 373N,ExxonMobil Chemical 10) Low-cis butadiene rubber, cis-1,4 content 39%.

[0119] The mixture was prepared according to the

[0120] The process is customary in the rubber industry under normal conditions in at least three stages in a laboratory mixer with a volume of 300 milliliters to 3 liters, in which all components except the vulcanization system (sulfur and vulcanization-influencing substances) were mixed for 200 to 600 seconds at 145 to 165 °C, target temperatures of 152 to 157 °C, in the first mixing stages (basic mixing stages).

[0121] For V3 and V4, an additional mastication was carried out beforehand, in which the natural rubber, zinc oxide and small amounts of the filler were premixed.

[0122] In a further step, the mixtures from the previous step were mixed again.

[0123] The final mix was produced by adding the vulcanization system in the third or fourth (V3 and V4) stage (final mix stage), mixing for 180 to 300 seconds at 90 to 120 °C.

[0124] Test specimens were produced from all mixtures by vulcanization to t95 to t100 (measured on a moving die rheometer according to ASTM D 5289-12 / ISO 6502) under pressure at 160°C to 170°C and with these test specimens, material properties typical for the rubber industry were determined using the test methods specified below. Shore hardness at room temperature (RT) according to ISO 868, DIN 53 505 Rebound resilience at 70 °C according to ISO 4662 or ASTM D 1054 Stress value at 100% elongation at room temperature (M100 RT) according to DIN 53 504 Dynamic storage modulus E' at 55 °C from dynamic-mechanical measurement according to DIN 53 513, strain sweep at 8% elongation (E' (8%)) Maximum (max.) loss factor Tan d, synonymous with tangent delta, tan δ, at 55 °C from dynamic-mechanical measurement according to DIN 53 513, strain sweep

[0125] The samples V2 and E2 were also aged for 14 days at 80 °C and then the fatigue resistance to crack formation and, if applicable, fracture of the sample under dynamic loading was determined: • Monsanto fatigue test FTF: "Fatigue to Failure" at 61% pre-strain and room temperature, specified in kc (kilocycles), based on the ASTM D4482 method • Fatigue test LTA: "Life time analysis" at 10% pre-strain and room temperature, specified in kc (kilocycles), crack growth test with crack initiation under dynamic loading; based on the Monsanto fatigue test FTF Table 1 ingredient Unit V1 E1 NR TSR phr 30 30 BR 1)< phr 70 70 Soot N339 phr 70 70 RAE phr 5 5 ZnO phr 3 3 Stearic acid phr 2 2 Phenolic resin phr 5 5 6PPD phr 2 2 Ozone protection wax phr 2 2 Mixture TMQ 2)< phr 4 - Mixture TMQ 3)< phr - 2 TBBS phr 2,5 2,5 Sulfur 4)< phr 3,73 3,73 Characteristics Shore hardness RT Shore A 74 75 Rebound 70 °C % 56,5 58,3 M 100 RT MPa 4,6 5,2 E' (8%) MPa 8,9 9,7 Tan d (max) 0,198 0,182 Table 2 ingredient Unit V2 E2 NR TSR phr 50 50 BR 1)< phr 50 50 Silica 5)< phr 46 46 Silane 6)< phr 3,3 3,3 TDAE phr 5 5 ZnO phr 3 3 Stearic acid phr 2 2 Phenolic resin phr 2 2 6PPD phr 2 2 Ozone protection wax phr 2 2 Mixture TMQ 2)< phr 4 - Mixture TMQ 3)< phr - 2 DPG phr 2 2 TBBS phr 1,5 1,5 sulfur phr 1,5 1,5 Characteristics Shore hardness RT Shore A 60 60 Rebound 70 °C % 65,7 66,4 M 100 RT MPa 1,9 1,9 E' (8%) MPa 4,8 4,9 Tan d (max) 0,093 0,082 Properties after aging (14 days, 80 °C) Monsanto FTF RT 61% pre-stretch kc 636 849 LTA RT 10% pre-stretch kc 333 2,000 (end of test) Table 3 ingredient Unit V3 V4 NR TSR phr 100 100 Soot N339 phr 62 62 TDAE phr 2 2 ZnO phr 7 7 Phenolic resin phr 1 1 6PPD phr 2 2 Mixture TMQ 2)< phr 4 - Mixture TMQ 3)< phr - 2 Adhesive system 7)< phr 9,8 9,8 DCBS phr 0,75 0,75 Sulfur 4)< phr 6,75 6,75 Characteristics Shore hardness RT Shore A 78 80 Rebound 70 °C % 49,2 49,1 M 100 RT MPa 5,0 5,3 Tan d (max) 0,176 0,175 Table 4 ingredient Unit V5 V6 NR TSR phr 50 50 SSBR phr 50 50 Soot N121 phr 5 5 Silica 8)< phr 60 60 Silane 6)< phr 5 5 Resin 9)< phr 15 15 ZnO phr 2,5 2,5 Stearic acid phr 2 2 6PPD phr 1,5 1,5 Ozone protection wax phr 2 2 Mixture TMQ 2)< phr 1,5 - Mixture TMQ 3)< phr - 0,75 CBS phr 2 2 sulfur phr 1,5 1,5 Characteristics Shore hardness RT Shore A 56 57 Rebound 70 °C % 56,3 55,7 M 100 RT MPa 1,3 1,4 Tan d (max) 0,140 0,140 Table 5 ingredient Unit V7 E3 V8 E4 V9 E5 NR TSR phr 30 30 70 70 70 70 BR 1)< phr - - 30 30 30 30 BR 10)< phr 70 70 - - - - Soot N339 phr 70 70 70 70 70 70 RAE phr 5 5 5 5 5 5 ZnO phr 3 3 3 3 3 3 Stearic acid phr 2 2 2 2 2 2 Phenolic resin phr 5 5 5 5 5 5 6PPD phr 2 2 2 2 2 2 Ozone protection wax phr 2 2 2 2 2 2 Mixture TMQ 2)< phr 4 - 4 - 1,5 - Mixture TMQ 3)< phr - 2 - 2 - 0,75 TBBS phr 2,5 2,5 2,5 2,5 2,5 2,5 Sulfur 4)< phr 3,73 3,73 3,73 3,73 3,73 3,73 Characteristics Shore hardness RT Shore A 75,5 76,5 74,7 74,8 75,5 75,8 Rebound 70 °C % 55,1 56 51,7 52,9 53,3 53,6 M 100 RT MPa 5,0 5,4 4,5 4,9 5,1 5,2 E' (8%) MPa 8,7 9,1 9,7 10,4 Tan d (max) 0,193 0,185 0,195 0,184 0,189 0,182 Table 6 ingredient Unit V10 E6 V11 E7 V12 E8 V13 E9 NR TSR phr - - - - 20 20 20 20 BR 1)< phr 50 50 50 50 30 30 30 30 SSBR phr 50 50 50 50 50 50 50 50 Soot N339 phr 70 70 70 70 70 70 70 70 RAE phr 5 5 5 5 5 5 5 5 ZnO phr 3 3 3 3 3 3 3 3 Stearic acid phr 2 2 2 2 2 2 2 2 Phenolic resin phr 5 5 5 5 5 5 5 5 6PPD phr 2 2 2 2 2 2 2 2 Ozone protection wax phr 2 2 2 2 2 2 2 2 Mixture TMQ 2)< phr 4 - 1,5 - 4 - 1,5 - Mixture TMQ 3)< phr - 2 - 0,75 - 2 - 0,75 TBBS phr 2,5 2,5 2,5 2,5 2,5 2,5 2,5 2,5 Sulfur 4)< phr 3,73 3,73 3,73 3,73 3,73 3,73 3,73 3,73 Characteristics Shore hardness RT Shore A 76,8 77,1 77,3 77,8 75,3 76 76,7 76,7 Rebound 70 °C % 54,3 55,7 55,8 56,1 54,1 55,3 54,2 55,7 M 100 RT MPa 5,2 5,8 5,8 5,9 5 5,4 5,4 5,6 E' (8%) MPa 11,7 12,2 12,4 12,8 10,6 10,8 11,3 11,5 Tan d (max) 0,193 0,186 0,185 0,183 0,195 0,188 0,194 0,187

[0126] As can be seen from Tables 1 to 6, surprisingly, only with the combination of a) butadiene rubber in the amounts according to the invention and c) the oligomer mixture of TMQ containing 70 to 100 wt.% of dimers and trimers, improved rebound resilience at 70 °C and improved heat build-up (lower values ​​for hysteresis loss, tangent delta) and thus further improved rolling resistance indicators as well as improved handling indicators are achieved.

[0127] The mixture E2 with a) 50 phr BR and c) the oligomer mixture of TMQ containing 70 to 100 wt.% of dimers and trimers additionally surprisingly shows significantly improved fatigue resistance, in particular against cracking and possibly fracture, after aging.

Claims

1. Sulfur-crosslinkable rubber mixture containing at least the following constituents: a) 30 to 95 phr, preferably 40 to 95 phr, particularly preferably 50 to 95 phr, of at least one butadiene rubber; and b) 5 to 70 phr, preferably 5 to 60 phr, particularly preferably 5 to 50 phr, of at least one further rubber; and c) 0.1 to 3.0 phr, preferably 0.2 to 3 phr, particularly preferably 0.2 to 2.5 phr, of an oligomer mixture of 2,2,4-trimethyl-1,2-dihydroquinoline, wherein the mixture contains 70% to 100% by weight of dimers and trimers of 2,2,4-trimethyl-1,2-dihydroquinoline.

2. Sulfur-crosslinkable rubber mixture according to Claim 1, characterized in that the at least one further rubber b) is at least one diene rubber preferably selected from the group consisting of natural polyisoprene (NR) and synthetic polyisoprene (IR) and styrene-butadiene rubber (SBR), wherein the styrene-butadiene rubber is preferably selected from solution-polymerized styrene-butadiene rubber (SSBR).

3. Sulfur-crosslinkable rubber mixture according to Claim 1 or 2, characterized in that it contains as rubber b) 5 to 40 phr of natural polyisoprene (NR), wherein the sulfur-crosslinkable rubber mixture preferably contains a) 60 to 80 phr of at least one butadiene rubber and b) 20 to 40 phr of at least one natural polyisoprene (NR).

4. Sulfur-crosslinkable rubber mixture according to Claim 1 or 2, characterized in that it contains a) 40 to 60 phr, preferably 45 to 55 phr, in particular 50 phr, of at least one butadiene rubber and b) 40 to 60 phr, 45 to 55 phr, in particular 50 phr, of at least one natural polyisoprene (NR).

5. Sulfur-crosslinkable rubber mixture according to any of the preceding claims, characterized in that the at least one butadiene rubber a) has a cis-1,4 content of 90% to 98%, preferably 94% to 98%.

6. Sulfur-crosslinkable rubber mixture according to any of the preceding claims, characterized in that the oligomer mixture c) contains 73% to 100% by weight, preferably 74% to 100% by weight, particularly preferably 74% to 95% by weight, very particularly preferably 74% to 85% by weight, of dimers and trimers of 2,2,4-trimethyl-1,2-dihydroquinoline.

7. Sulfur-crosslinkable rubber mixture according to any of the preceding claims, characterized in that the oligomer mixture contains the substance isopropylidene bis aniline in an amount of less than 0.05% by weight, preferably less than 0.02% by weight, particularly preferably less than 0.01% by weight, in turn preferably 0% to 0.0099% by weight.

8. Sulfur-crosslinkable rubber mixture according to any of the preceding claims, characterized in that the oligomer mixture contains the monomer 2,2,4-trimethyl-1,2-dihydroquinoline in an amount of less than 0.7% by weight, preferably 0% to 0.5% by weight.

9. Sulfur-crosslinkable rubber mixture according to any of the preceding claims, characterized in that it contains d) at least one filler, preferably 20 to 500 phr, particularly preferably 20 to 400 phr, in turn preferably 20 to 180 phr, very particularly preferably 45 to 180 phr, of at least one carbon black.

10. Vulcanizate obtained by sulfur vulcanization of at least one rubber mixture according to any of Claims 1 to 9.

11. Vehicle tyre, characterized in that it comprises at least one vulcanizate according to Claim 10 in at least one component.

12. Vehicle tyre according to Claim 11, characterized in that it comprises at least one vulcanizate according to Claim 10 at least in an outer component, preferably in the flange profile, tread and / or sidewall.

13. Process for producing the sulfur-crosslinkable rubber mixture according to Claim 1 comprising at least the process steps of: X1) providing a) 30 to 95 phr of at least one butadiene rubber; and X2) providing b) 5 to 70 phr of at least one further rubber; and X3) providing c) 0.1 to 3.0 phr of an oligomer mixture of 2,2,4-trimethyl-1,2-dihydroquinoline, wherein the mixture contains 70% to 100% by weight of dimers and trimers of 2,2,4-trimethyl-1,2-dihydroquinoline; and X4) mixing the components from steps X1), X2) and X3), wherein the reported amounts in phr relate to 100 parts by weight of the total mass of all rubbers in the produced sulfur-crosslinkable rubber mixture.

14. Use of the sulfur-crosslinkable rubber mixture according to any of Claims 1 to 9 for the production of technical rubber articles, such as bellows, conveyor belts, air springs, belts, drive belts or hoses, and also shoe soles.