Vulcanizate, its use and vehicle tires

Abstract

Vulcanizate obtained by sulfur vulcanization of a sulfur-crosslinkable rubber mixture containing - 10 to 30 phr of at least one natural and / or synthetic polyisoprene and - 70 to 90 phr of at least one styrene-butadiene rubber and / or polybutadiene and - at least one polyethylene with a density according to ASTM D 1505 of 0.915 to 0.935 g / cm 3 and a weight average molecular weight distribution Mw according to GPC of 20000 to 500000 g / mol.

Description

[0001] The invention relates to a vulcanizate obtained by sulfur vulcanization from a sulfur-crosslinkable rubber mixture, in particular for treads of vehicle tires, a use of the vulcanizate and a vehicle tire.

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

[0003] To influence the compound and vulcanizate properties, a wide variety of additives are added to the mixtures and / or special polymers are used. Examples of additives include fillers (e.g., carbon black), plasticizers, anti-aging agents, and crosslinking systems made of sulfur, accelerators, and activators. However, if one property is improved by varying the mixture, this is often accompanied by a deterioration of another property, resulting in certain conflicting objectives. In compounds for vehicle tire treads, such conflicting objectives exist, for example, with regard to abrasion behavior and increased heat buildup, which leads to poorer rebound resilience and, consequently, poorer rolling resistance.

[0004] US Patent No. 5,341,863 A proposes the use of LDPE ("low-density polyethylene") as an additive in certain polymer systems of rubber compounds for vehicle tire treads. This results in either improved crack resistance with good processability or abrasion resistance.

[0005] The present invention is based on the object of providing a sulfur-crosslinked vulcanizate, in particular for treads of vehicle tires, which has an improvement over the prior art with regard to the conflicting objectives of abrasion resistance, heat build-up and crack resistance, in particular under impact load, as well as tensile strength.

[0006] This task is solved by a vulcanizate obtained by sulfur vulcanization of a sulfur-crosslinkable rubber mixture containing: - 10 to 30 phr of at least one natural and / or synthetic polyisoprene and - 70 to 90 phr of at least one styrene-butadiene rubber and / or polybutadiene and - at least one polyethylene with a density according to ASTM D 1505 of 0.915 to 0.935 g / cm 3 and a weight average molecular weight distribution Mw according to GPC of 20000 to 500000 g / mol.

[0007] A further object underlying the present invention is to provide a vehicle tire which has an improvement over the prior art with regard to abrasion resistance, rolling resistance and crack resistance, in particular under impact load.

[0008] The object is achieved in that the vehicle tire has at least one vulcanizate according to the invention of at least one sulfur-crosslinkable rubber mixture having the above-mentioned features in at least one component, in particular at least in the tread.

[0009] Vehicle tires that contain the rubber compound at least in the tread have increased abrasion resistance and lower (and thus improved) rolling resistance as well as increased crack resistance, especially under sudden loads, which is particularly advantageous for use in treads of industrial and construction vehicles

[0010] 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, passenger car and two-wheeler tires, and in particular tires for "Off The Road" (OTR) applications.

[0011] According to a preferred embodiment of the invention, the tire is for OTR use in radial or diagonal construction, in particular diagonal construction.

[0012] The rubber compound is also suitable for other components of vehicle tires, such as sidewalls, horn profiles and inner tire components.

[0013] The rubber compound is also suitable for other technical rubber articles, such as bellows, conveyor belts, air springs, belts, straps or hoses, as well as shoe soles, whereby it is particularly suitable for conveyor belts due to the requirements profile.

[0014] The components of the sulfur-curable rubber mixture are described in more detail below. All statements also apply to the vulcanizate according to the invention, the vehicle tire according to the invention, and the use according to the invention.

[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 in this document is based on 100 parts by weight of the total mass of all high-molecular-weight (weight-average molecular weight according to GPC of 250,000 to 5,000,000 g / mol) and thus solid rubbers present in the mixture.

[0016] The rubber mixture contains 10 to 30 phr of at least one natural and / or synthetic polyisoprene and 70 to 90 phr of at least one styrene-butadiene rubber and / or polybutadiene.

[0017] The natural and / or synthetic polyisoprene in all embodiments can be either cis-1,4-polyisoprene or 3,4-polyisoprene. However, the use of cis-1,4-polyisoprenes with a cis-1,4 content of > 90 wt.% 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 also such a cis-1,4-polyisoprene; the cis-1,4 content in natural rubber is greater than 99 wt.%.

[0018] Furthermore, a mixture of one or more natural polyisoprenes with one or more synthetic polyisoprene(s) is also conceivable.

[0019] The butadiene rubber (= BR, polybutadiene) 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 wt.% being referred to as the high-cis type, and polybutadiene with a cis content less than 90 wt.% 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 wt. With a high-cis BR, particularly good abrasion properties and low hysteresis of the rubber mixture are achieved.

[0020] 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. However, other modifications known to the skilled person, also referred to as functionalizations, are also possible. Metal atoms can be a component of such functionalizations.

[0021] If 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 present invention.

[0022] The styrene-butadiene copolymer used can be end-group modified with the modifications and functionalizations mentioned above for polybutadiene and / or functionalized along the polymer chains.

[0023] The rubber mixture may contain 0.1 to 20 phr of at least one other diene rubber.

[0024] 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.

[0025] The further diene rubber can be epoxidized polyisoprene and / or styrene-isoprene rubber and / or halobutyl rubber and / or polynorbornene and / or isoprene-isobutylene copolymer and / or ethylene-propylene-diene rubber and / or nitrile rubber and / or chloroprene rubber and / or acrylate rubber and / or fluororubber and / or silicone rubber and / or polysulfide rubber and / or epichlorohydrin rubber and / or styrene-isoprene-butadiene terpolymer and / or hydrogenated acrylonitrile-butadiene rubber and / or hydrogenated styrene-butadiene rubber and / or butadiene-isoprene rubber.

[0026] 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.

[0027] According to a preferred embodiment, however, the rubber mixture contains no additional diene rubber, i.e., 0 phr of additional diene rubber. In this case, the sum of the polyisoprene, styrene-butadiene rubber, and butadiene rubber contained amounts to 100 phr.

[0028] According to a preferred embodiment, the rubber mixture contains 10 to 30 phr of at least one natural and / or synthetic polyisoprene, preferably natural polyisoprene (NR), and 35 to 45 phr of at least one styrene-butadiene rubber and 35 to 45 phr of at least one butadiene rubber. This achieves a particularly significant improvement in the aforementioned conflicting objectives of abrasion resistance, heat buildup, crack resistance, especially under impact loads, and tensile strength.

[0029] According to a preferred embodiment of the invention, the styrene-butadiene rubber is emulsion-polymerized styrene-butadiene rubber (ESBR).

[0030] The rubber mixture contains at least one polyethylene with a density according to ASTM D 1505 of 0.915 to 0.935 g / cm 3 and a weight average molecular weight distribution Mw according to GPC of 20000 to 500000 g / mol.

[0031] Such polyethylene is also called LDPE, or “low density polyethylene.”

[0032] The rubber mixture preferably contains 2 to 30 phr, particularly preferably 2 to 20 phr, very particularly preferably 7 to 20 phr, of at least one polyethylene.

[0033] Preferably, the polyethylene has a softening point according to ASTM D 1525 of 85 to 99 °C.

[0034] Preferably, the polyethylene has a melt index according to ASTM D 1238 of 0.4 g / 10 min to 5 g / 10 min.

[0035] A suitable polyethylene with a density according to ASTM D 1505 of 0.922 g / cm 3 and a softening point according to ASTM D 1525 of 93°C is available, for example, under the trade name TITANLENE LDF250YZ.

[0036] Surprisingly, the rubber compound containing the aforementioned combination of LDPE and polymer system shows an improvement in abrasion resistance, rolling resistance behavior, tensile strength and crack resistance, especially under impact loads, which is particularly advantageous for use in treads of industrial and construction vehicles.

[0037] The rubber mixture further preferably contains at least one filler such as, in particular, silica and / or carbon black.

[0038] According to a preferred embodiment, the rubber mixture contains 50 to 100 phr of at least one carbon black.

[0039] The rubber mixture preferably contains 50 to 80 phr, particularly preferably 55 to 65 phr, of at least one carbon black. This results, particularly in combination with the aforementioned components, in high hardness due to the reinforcing properties of carbon black / polymer interactions and thus high penetration resistance against crack-causing objects. Furthermore, improved resistance to volume loss under abrasive conditions is achieved, while simultaneously achieving a good level of heat build-up.

[0040] Within the scope of the present invention, all types of carbon black known to those skilled in the art are conceivable. However, preference is given to using a carbon black having an iodine adsorption number according to ASTM D 1510 of 20 to 180 g / kg, particularly preferably 30 to 140 kg / g, and a DBP number according to ASTM D 2414 of 30 to 200 ml / 100 g, preferably 90 to 180 ml / 100 g, particularly preferably 90 to 150 ml / 100 g. A particularly suitable carbon black within the scope of the present invention is, for example, a carbon black of ASTM type N234 with an iodine adsorption number of 120 g / kg and a DBP number of 125 ml / 100 g. This achieves particularly good properties with regard to the technical task for use in vehicle tires, particularly in the tread.

[0041] According to a preferred embodiment, the rubber mixture contains at least one silica, preferably in amounts of 5 to 100 phr, particularly preferably 5 to 50 phr, most preferably 5 to 20 phr, again particularly preferably 7 to 17 phr.

[0042] This results, particularly in combination with the components mentioned, in increased resistance to the formation and propagation of cracks in the described vulcanizate while at the same time maintaining a good level of heat build-up.

[0043] The silicas can be those known to those skilled in the art and suitable as fillers for tire rubber compounds. However, it is particularly preferred to use a finely divided, precipitated silica with a nitrogen surface area (BET surface area) (according to DIN ISO 9277 and DIN 66132) of 35 to 350 m². 2 / g, preferably from 60 to 260 m 2 / g, particularly preferably from 120 to 230 m 2 / g, and a CTAB surface area (according to ASTM D 3765) of 30 to 400 m 2 / g, preferably from 60 to 250 m 2 / g, particularly preferably from 120 to 230 m 2 / g.

[0044] According to a preferred embodiment, the rubber mixture contains 5 to 20 phr of at least one silica and 50 to 80 phr of at least one carbon black. This combination increases crack resistance and reduces volume loss under abrasive conditions, while simultaneously achieving a good level of heat buildup.

[0045] The rubber mixture preferably contains the smallest possible amounts or no additional fillers, i.e., preferably 0 to 2 phr of additional fillers, particularly preferably 0 phr, and in particular no non-reinforcing fillers. The rubber mixture is thus preferably free of non-reinforcing fillers.

[0046] Non-reinforcing fillers in the context 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). Other potentially reinforcing fillers are, for example, 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

[0047] Carbonyl groups), graphite and graphene and so-called “carbon-silica dual-phase filler”.

[0048] Zinc oxide is not considered a filler in the context of the present invention.

[0049] The terms “silicic acid” and “silica” are used synonymously in the context of the present invention, as is also common practice in the art.

[0050] To improve processability and to bond the silica and any other polar fillers present to the diene rubber, silane coupling agents can be used in rubber compounds. One or more different silane coupling agents can be used in combination. The rubber compound can thus contain a mixture of different silanes. The silane coupling agents react with the surface silanol groups of the silica or other polar groups during mixing of the rubber or rubber compound (in situ) or even before the filler is added to the rubber in the form of a pretreatment (premodification). Silane coupling agents that can be used include any silane coupling agents known to those skilled in the art for use in rubber compounds.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, 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, -NH2 or -S x - (with x = 2 to 8).

[0051] 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).

[0052] Preference is given to using a silane mixture which contains 40 to 100% by weight of disulfides, more preferably 55 to 85% by weight of disulfides, and most preferably 60 to 80% by weight of disulfides. Such a mixture is available, for example, under the trade name Si 261® from Evonik, which is described, for example, in DE 102006004062 A1. Blocked mercaptosilanes, as known, for example, from WO 99 / 09036, can also be used as silane coupling agents. Silanes as described in WO 2008 / 083241 A1, WO 2008 / 083242 A1, WO 2008 / 083243 A1 and WO 2008 / 083244 A1 can also be used. The following can be used, for example: B. Silanes sold under the name NXT (e.g. 3-(octanoylthio)-1-propyl-triethoxysilane) in various variants by Momentive, USA, or those sold under the name VP Si 363® by Evonik Industries.

[0053] Furthermore, it is conceivable that one of the above-mentioned mercaptosilanes, in particular 3-mercaptopropyltriethoxysilane, is used in combination with processing aids (listed below), in particular PEG carboxylic acid esters.

[0054] According to a preferred embodiment, the rubber mixture contains a combination of 3-mercaptopropyltriethoxysilane and PEG carboxylic acid ester, which results in particularly good properties, in particular with regard to the technical problem to be solved and overall a good level of properties with regard to the other properties.

[0055] Furthermore, the rubber mixture may contain other activators and / or agents for binding fillers, especially carbon black. These may be, for example, the compound S-(3-aminopropyl)thiosulfuric acid, disclosed in EP 2589619 A1, and / or its metal salts, which, particularly when combined with at least one carbon black as a filler, result in very good physical properties of the rubber mixture.

[0056] The silanes and activators mentioned are preferably added in at least one basic mixing stage during the production of the rubber mixture.

[0057] According to a preferred embodiment, the rubber mixture contains at least one hydrocarbon resin as an adhesion promoter to achieve improved adhesion to adjacent tire components. Suitable hydrocarbon resins include, for example, and in particular, indene-coumarone resins, preferably with a softening point according to ASTM E 28 (ring and ball) of 0 to 105°C, particularly preferably 87 to 105°C, and C9 hydrocarbon resins, preferably with a softening point according to ASTM E 28 (ring and ball) of 0 to 105°C, particularly preferably 87 to 105°C.

[0058] The person skilled in the art knows that the term C9 hydrocarbon resins refers to homo- or co-polymers composed of hydrocarbon monomers with 9 carbon atoms.

[0059] According to a preferred embodiment, the rubber mixture contains at least one plasticizer, with the total amount of plasticizer preferably being 1 to 10 phr, particularly preferably 2 to 9 phr. This results, particularly in combination with the above-mentioned components, in particularly good processability of the rubber mixture, especially of the extrudates prior to crosslinking, while simultaneously providing good rolling resistance indicators and good (and thus low) heat buildup. An amount of plasticizer exceeding 10 phr would also undesirably reduce hardness and stiffness.

[0060] The plasticizers used in the context of the present invention include all 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), 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 rapeseed oil or factice, or plasticizer resins that are not among the adhesion promoters mentioned above, 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. If additional liquid polymers are used as plasticizers in the rubber mixture, these are not included as rubber in the calculation of the composition of the polymer matrix.

[0061] The plasticizer resins can in particular and preferably be unmodified phenolic resins.

[0062] The plasticizer is preferably selected from the group consisting of the above-mentioned plasticizers.

[0063] Mineral oils are particularly preferred as plasticizers.

[0064] When using mineral oil, this is preferably selected from the group consisting of DAE (Distilled Aromatic Extracts) and / or RAE (Residual Aromatic Extract) and / or TDAE (Treated Distilled Aromatic Extracts) and / or MES (Mild Extracted Solvents) and / or naphthenic oils.

[0065] According to a preferred embodiment, the rubber mixture contains at least one mineral oil plasticizer, preferably at least TDAE and / or RAE as plasticizer. This results in particularly good processability, in particular good miscibility of the rubber mixture.

[0066] The plasticizer(s) are preferably added in at least one basic mixing stage during the production of the rubber mixture.

[0067] 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 a) Anti-aging agents 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) mastication aids, such as 2,2'-dibenzamidodiphenyl disulfide (DBD) and e) processing aids such as fatty acid salts, such as zinc soaps, and fatty acid esters and their derivatives.

[0068] 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.

[0069] The total amount of other additives also contains 0.1 to 10 phr, preferably 1 to 8 phr, particularly preferably 1.5 to 4 phr, of zinc oxide (ZnO).

[0070] This can be any type of zinc oxide known to the person skilled in the art, such as ZnO granules or powder. The zinc oxide commonly used usually has a BET surface area of ​​less than 10 m 2 / g. However, it can also be a zinc oxide with a BET surface area of ​​10 to 100 m 2 / g, such as so-called “nano-zinc oxides”, can be used.

[0071] It is common practice to add zinc oxide as an activator to a rubber compound for sulfur crosslinking with vulcanization accelerators, usually in combination with fatty acids (e.g., stearic acid). The sulfur is then activated for vulcanization by complex formation.

[0072] The vulcanization of the sulfur-curable 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.

[0073] 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).

[0074] All sulfur-donating substances 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, this is preferably selected from the group comprising, for example, thiuram disulfides, such as tetrabenzylthiuram disulfide (TBzTD) and / or tetramethylthiuram disulfide (TMTD) and / or tetraethylthiuram disulfide (TETD), and / or thiuram tetrasulfides, such as dipentamethylenethiuram tetrasulfide (DPTT), and / or dithiophosphates, such as

[0075] DipDis (bis-(diisopropyl)thiophosphoryl disulfide) and / or bis(O,O-2-ethylhexylthiophosphoryl)polysulfide (e.g. Rhenocure SDT 50®, Rheinchemie GmbH) and / or zinc dichloryldithiophosphate (e.g. Rhenocure ZDT / S®, Rheinchemie GmbH) and / or zinc alkyldithiophosphate, and / or 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane and / or diarylpolysulfides and / or dialkylpolysulfides.

[0076] Other network-forming systems, such as those available under the trade names Vulkuren®, Duralink®, or Perkalink®, or network-forming systems as described in WO 2010 / 049216 A2, can also be used in the rubber compound. This system contains a vulcanizing agent that crosslinks with a functionality greater than four and at least one vulcanization accelerator. The vulcanizing agent that crosslinks with a functionality greater than four has, for example, the general formula A): G[CaH2a−CH2−SbY]c wherein G is a polyvalent cyclic hydrocarbon group and / or a polyvalent heterohydrocarbon group and / or a polyvalent siloxane group containing 1 to 100 atoms; wherein each Y is independently selected from a rubber-active group containing sulfur-containing functionalities; and wherein a, b, and c are integers each of which independently includes: a is 0 to 6; b is 0 to 8; and c is 3 to 5.

[0077] The rubber-active group is preferably selected from a thiosulfonate group, a dithiocarbamate group, a thiocarbonyl group, a mercapto group, a hydrocarbon group, and a sodium thiosulfonate group (Bunte salt group). This achieves very good abrasion and tear properties of the rubber mixture. For the purposes of the present invention, sulfur and sulfur donors, including sulfur-donating silanes such as TESPT, and vulcanization accelerators as described above and vulcanizing agents that crosslink with a functionality greater than four, as described in WO 2010 / 049216 A2, such as a vulcanizing agent of formula A), as well as the above-mentioned systems Vulkuren®, Duralink®, and Perkalink®, are conceptually summarized as vulcanizing agents.

[0078] During the final mixing stage, at least one vulcanizing agent selected from the group containing, particularly preferably consisting of, sulfur and / or sulfur donors and / or vulcanization accelerators and / or vulcanizing agents that crosslink with a functionality greater than four is preferably added to the rubber mixture during its production. This allows a sulfur-crosslinked rubber mixture, particularly for use in vehicle tires, to be produced from the mixed final mixture by vulcanization.

[0079] The use of the accelerators TBBS and / or CBS and / or diphenylguanidine (DPG) is particularly preferred.

[0080] In addition, vulcanization retarders may be present in the rubber compound.

[0081] The terms “vulcanized” and “crosslinked” are used synonymously in the context of the present invention.

[0082] According to a preferred development of the invention, several accelerators are added in the final mixing stage during the production of the sulfur-crosslinkable rubber mixture.

[0083] The sulfur-curable 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 (sulfur and vulcanization-influencing substances) is first prepared in one or more mixing stages. The final compound is created by adding the vulcanization system in a final mixing stage. The final compound is further processed, for example, by extrusion or calendering, and formed into the appropriate shape.

[0084] Subsequently, further processing takes place by vulcanization, whereby sulfur crosslinking takes place due to the vulcanization system added within the scope of the present invention.

[0085] The rubber compound described above is particularly suitable for use in vehicle tires, especially pneumatic tires. In principle, it can be used in all tire components, particularly in a tread, especially in the cap of a tread with a cap / base construction.

[0086] For use in vehicle tires, the mixture is preferably formed into a tread shape as a ready-mix before vulcanization and applied as usual during the production of the green vehicle tire.

[0087] The rubber compound for use as a body compound in vehicle tires is produced as described above. The difference lies in the shaping after the extrusion process or calendering of the compound. The resulting shapes of the still unvulcanized rubber compound for one or more different body compounds are then used to construct a green tire. The body compound refers to the rubber compounds for the other outer and inner components of a tire, such as the squeegee, sidewall, inner liner (inner layer), apex, belt, shoulder, belt profile, carcass, bead reinforcement, bead profile, flange profile, and bandage.

[0088] For use in belts and straps, especially conveyor belts, the extruded, still unvulcanized compound is molded into the appropriate shape and often provided with reinforcements, such as synthetic fibers or steel cords, either during or after the process. This usually results in a multi-layer structure consisting of one or more layers of rubber compound, one or more layers of the same and / or different reinforcements, and one or more additional layers of the same and / or a different rubber compound.

[0089] The invention will now be explained in more detail using comparative and exemplary embodiments, which are summarized in Table 1.

[0090] The comparison mixtures are marked with V, the mixtures for the vulcanizate according to the invention are marked with E.

[0091] The compound was manufactured according to the process commonly used in the rubber industry 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.

[0092] Test specimens were produced from all mixtures by vulcanization after 20 minutes under pressure at 160°C and with these test specimens, material properties typical for the rubber industry were determined using the test methods given below. • Shore A hardness at room temperature (RT) and 70 °C according to DIN ISO 7619-1 • Tensile strength and elongation at room temperature according to DIN 53 504 • High-speed elongation as tear energy per deformed volume at room temperature according to the High Speed ​​Tear Energy Test according to DIN EN 10 045 (HSTE) • Rebound resilience at room temperature and 70°C according to ISO 4662 or ASTM D 1054 • Abrasion at room temperature according to DIN / ISO 4649 • Gabometer: Characterization of the heat development and the service life of elastomers under sinusoidal compressive stress (compression) according to DIN 53535, indication of the temperature T of the test specimen at the head. Substances used a) NR: Natural rubber TSR b) BR: Buna CB 24, Lanxess, Dormagen, Germany c) ESBR: emulsion-polymerized styrene-butadiene rubber, SBR1500, Polimeri d) LDPE: TITANLENE LDF250YZ, Titan Chemical Corp; density according to ASTM D 1505 = 0.922 g / cm 3Vicat softening point according to ASTM D 1525 = 93 °C; melt index according to ASTM D 1238 = 0.75 g / 10 min e) Silica: VN3, Evonik f) Adhesion promoter: 4 phr indene-coumarone resin NOVARES C 90 RUETGERS GERMANY GMBH DUISBURG, D with EP = 85 to 95 °C and 4 phr C9 hydrocarbon resin UNILENE A90 Braskem Qpar SAO PAULO, BR with EP = 85 to 95 °C 8) Plasticizers: TDAE and / or RAE h) Additives: Stearic acid, ZnO, N-(1,3-DIMETHYLBUTYL)-N'-PHENYL-P-PHENYLENEDIAMINE, 2,2,4-Trimethyl-1,2-Dihydroquinoline, refined paraffin wax and microcrystalline wax, zinc soap i) Accelerators: Diphenyl guanidine, N-tert-butyl-2-benzothiazole sulfenamide, N-(cyclohexylthio)phthalimide Table 1 Components Unit V1 E1 V2 V3 V4 V5 No. a) phr 20 20 100 100 50 50 BR b) phr 40 40 - - - - ESBR c) phr 40 40 - - 50 50 LDPE d) phr - 15 - 15 - 15 Silica e) phr 12 12 12,7 12,7 12,7 12,7 Soot N234 phr 60 60 - - - - Soot N339 phr - - 46 46 46 46 Adhesion promoter f) phr 8 8 8 8 8 8 plasticizers g) phr 8 8 8 8 8 8 additives h) phr 16,5 16,5 17 17 17 17 accelerator i) phr 1,5 1,5 1,1 1,1 1,1 1,1 sulfur phr 1,6 1,6 1,8 1,8 1,8 1,8 Hardness RT Shore A 64 70 58 64 61 67 Hardness 70 °C Shore A 55 60 50 54 51 55 Review RT % 31 30 36 34 33 32 Check back 70 °C % 41 40 51 50 44 43 Tensile strength MPa 18 18 17 15 15 14 Elongation at break % 604 636 547 510 564 578 HSTE MJ / cm 3 11,5 13 14,7 16,5 15,8 16,5 T Gabometer °C 106 85 88 74 88 82 Abrasion mm 3 83 76 223 153 157 134

[0093] As can be seen from Table 1, the rubber compound E1 for a vulcanizate according to the invention (compared to V1 without LDPE) has greater abrasion resistance, significantly lower heat build-up (lower Gabometer temperature) and increased crack resistance under sudden loading (HSTE) with constant tensile strength.

[0094] In the comparison systems V2 / V3 and V4 / V5, which use a different polymer system, a deterioration in tensile strength is achieved with LDPE. Furthermore, the comparison compounds V3 and V5, even with LDPE, exhibit significantly higher (poorer) levels of abrasion.

[0095] The rubber compound with the combination of LDPE and polymer system, on the other hand, has a heat build-up comparable to V2 to V5, with abrasion resistance, tensile strength and elongation at break being at a better level.

[0096] A vehicle tire having the rubber mixture in at least one component, preferably in the tread, thus exhibits improved abrasion behavior and improved and / or comparable rolling resistance as well as improved resistance to cracks, in particular to damage to the tread pattern, under high load while maintaining the same strength.

Claims

[1] Vulcanizate obtained by sulfur vulcanization of a sulfur-crosslinkable rubber mixture containing - 10 to 30 phr of at least one natural and / or synthetic polyisoprene and - 70 to 90 phr of at least one styrene-butadiene rubber and / or polybutadiene and - at least one polyethylene with a density according to ASTM D 1505 of 0.915 to 0.935 g / cm 3 and a weight average molecular weight distribution Mw according to GPC of 20000 to 500000 g / mol. [2] Vulcanizate according to claim 1, characterized by that the sulfur-crosslinkable rubber mixture contains 10 to 30 phr of at least one natural and / or synthetic polyisoprene and 35 to 45 phr of at least one styrene-butadiene rubber and 35 to 45 phr of at least one butadiene rubber. [3] Vulcanizate according to claim 1 or 2, characterized by that the polyethylene has a softening point according to ASTM D 1525 of 85 to 99 °C. [4] Vulcanizate according to one of the preceding claims, characterized by that the polyethylene has a melt index according to ASTM D 1238 of 0.4 g / 10 min to 5 g / 10 min. [5] Vulcanizate according to one of the preceding claims, characterized by that the sulfur-curable rubber compound contains 2 to 30 phr of polyethylene. [6] Vulcanizate according to one of the preceding claims, characterized by that the sulfur-curable rubber mixture contains 50 to 100 phr of at least one carbon black. [7] Vulcanizate according to one of the preceding claims, characterized by that the sulfur-curable rubber compound contains 5 to 20 phr of silica. [8] Vehicle tyre comprising in at least one component at least one vulcanizate according to at least one of claims 1 to 7. [9] Vehicle tyre according to claim 8, characterized by that the component is at least a tread. [10] Use of at least one vulcanizate according to one of claims 1 to 7 for producing a conveyor belt.