Sulfur-curable rubber compound

Description

[0001] The invention relates to a sulfur-crosslinkable rubber compound for metallic reinforcing elements, comprising at least one novolac resin having alkylurethane units and produced by reacting a phenolic compound, an aldehyde, and a carbamate resin, wherein the carbamate resin is produced by reacting alkylurethane with an aldehyde, and at least one etherified melamine resin. The invention further relates to a vehicle tire comprising at least one such sulfur-crosslinked rubber compound.

[0002] In sulfur-crosslinkable rubber compounds used as rubberizing compounds for textile reinforcement materials such as rayon, polyamide, and polyester, so-called methylene acceptor-methylene donor pairs are typically employed to achieve, in addition to bonding via the sulfur network, a bond for adhesive impregnation of the textile reinforcement material, usually an RFL dip. The RFL dip contains resorcinol and formaldehyde or their precondensates.

[0003] As an alternative to RFL dips, malein-functionalized polymers are now also offered for the treatment of textile fabrics or textile reinforcement elements to achieve improved adhesion to rubber compounds. Such so-called RF-free dips are disclosed, for example, in EP 1745079 B1 and DE 102014211365 A1.

[0004] Examples of methylene donors / formaldehyde donors include hexamethoxymethylmelamine (HMMM) and / or hexamethylenetetramine (HMT). Their use is widespread in the tire industry. Methylene acceptors include resorcinol and resorcinol equivalents or their precondensates, as well as other phenols. During the vulcanization process, a resin is formed from the methylene donor and the methylene acceptor. In addition to the sulfur network, a second network based on methylene donor and methylene acceptor forms, which interacts adhesively with the bonding agent in the reinforcing layer.

[0005] The use of methylene acceptor-methylene donor pairs is also known for rubber compounds for metallic reinforcing elements, particularly brass-plated steel cord. In the so-called direct adhesion process for brass-plated steel cord, the rubber compound contains, for example, cobalt salts and a resorcinol-formaldehyde-silica system, with the formaldehyde typically derived from formaldehyde donors such as etherified melamine resins. Examples of etherified melamine resins include hexamethoxymethylmelamine (HMMM) and hexamethylenetetramine (HMT). To improve adhesion, reinforcing resins are also used, and the compounds should contain a high proportion of sulfur and a lower proportion of accelerators to ensure sufficient mechanical interlocking with the steel cord surface.

[0006] Resorcinol-based methylene acceptors have disadvantages with regard to occupational safety and environmental protection. Resorcinol has a relatively high vapor pressure at the processing temperatures of a rubber compound, so that it partially evaporates during processing and condenses on cooler components. This leads to significant contamination and thus high cleaning costs in the processing environment. Furthermore, resorcinol is classified as harmful to health and the environment. It may affect the central nervous system. Therefore, efforts are being made to avoid using resorcinol as a methylene acceptor.

[0007] Mixtures that do not require methylene acceptors are known, for example, from EP 0 830 423 B1 and EP 2 065 219 A1. However, these publications use so-called self-condensing alkylated triazine resins with high imino and / or methylol functionality, whereby it is assumed that the high imino and / or methylol functionality allows these resins to self-condense and thereby form a network necessary for adhesion without the need for a methylene acceptor.

[0008] From EP 2 674 452 A1, it is known to use a reactive phenolic resin, in particular a phenolic resin modified with a vegetable and / or animal oil, an unsaturated oil and / or aromatic hydrocarbon, as a methylene acceptor in a sulfur-crosslinkable rubber compound for textile reinforcement in vehicle tires. This results in good adhesion, fewer impurities during compound production, and at the same time eliminates the need for resorcinol, which is harmful to health and the environment, during processing.

[0009] It has been shown that the aforementioned methylene acceptors do not lead to the desired adhesion and stiffness in all applications, particularly in all tire body compounds. Resorcinol residues are also frequently present in the resins, which pose the known health and environmental hazards during processing.

[0010] From EP 2 432 810 B1, adhesion-enhancing rubberizing compounds for rubber articles are known, which contain at least one novolac resin having alkylurethane units and being produced by the reaction of a phenolic compound, an aldehyde, and a carbamate resin, wherein the carbamate resin is produced by the reaction of alkylurethane with an aldehyde, and at least one etherified melamine resin. The compounds are said to be characterized by good hardness, tensile strength, and adhesion, and do not contain resorcinol-based systems that are hazardous to health and the environment. The compounds described in EP 2 432 810 B1 contain 3 phr of a butylcarbamate-functionalized phenol-formaldehyde resin and 3 phr of hexamethoxymethylmelamine (HMMM).

[0011] The invention is based on the objective of providing a sulfur-crosslinkable rubberizing compound that exhibits improved adhesion to metallic reinforcement carriers and thus leads to an improvement in terms of the durability of the rubberized reinforcement carrier layers.

[0012] The problem is solved according to the invention by the fact that the rubberizing mixture contains at least one organic cobalt salt.

[0013] Surprisingly, it has been shown that the addition of cobalt salts can significantly improve the adhesion between metallic reinforcing elements and the rubber compound.

[0014] According to an advantageous embodiment of the invention, the rubberizing mixture contains less than 2.5 phr (parts by weight, based on 100 parts by weight of the total rubbers in the mixture), preferably 1.2 to 1.8 phr, of at least one novolac resin having alkylurethane units and produced by reaction of a phenol compound, an aldehyde and a carbamate resin, wherein the carbamate resin is produced by reaction of alkylurethane with an aldehyde, and less than 2.5 phr, preferably 1.2 to 1.8 phr, of at least one etherified melamine resin.

[0015] 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 individual substances by weight is always based on 100 parts by weight of the total mass of all rubbers present in the mixture. The mass of all rubbers present in the mixture adds up to 100.

[0016] With such small quantities of the special novolac resin and the etherified melamine resin, rubber compounds can be obtained that, after vulcanization, are characterized by improved tensile strength and elongation at break. This leads to improved durability of the rubberized reinforcing elements and thus of the rubber products containing these rubberized reinforcing elements. Furthermore, a shorter vulcanization time can be achieved with such rubber compounds.

[0017] To achieve particularly good results with regard to adhesion and stress-strain behavior, it has proven advantageous if the sum of the proportions of the novolac resin and the etherified melamine resin is less than 5 phr, preferably 2.5 to 3.5 phr.

[0018] Preferably, the ratio of the novolac resin to the etherified melamine resin is 1:1.5 to 1.5:1, particularly preferably 1:1.

[0019] If the rubber compound is free of resorcinol as an adhesive substance according to an advantageous further development, the compounds are also more environmentally friendly and less hazardous to health during processing.

[0020] Novolak resin is produced by reacting a phenolic compound with an aldehyde and a carbamate resin. The phenolic compound can be selected from the group consisting of phenol, o-, m-, and p-cresol, and o-, m-, and p-monoalkylphenols with alkyl groups having up to 18 carbon atoms. Preferably, the phenolic compound is phenol. The aldehyde can be selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, and isobutyraldehyde. Preferably, the aldehyde is formaldehyde.

[0021] The carbamate resin is produced by reacting alkylurethane with an aldehyde. The alkylurethane can be selected from the group consisting of ethylurethane, butylurethane, 2-ethylhexylurethane, and decylurethane. Preferably, the alkylurethane is butylurethane.

[0022] The aldehyde for the carbamate resin can be selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, and isobutyraldehyde. Preferably, the aldehyde is formaldehyde.

[0023] The aldehydes used for the novolac resin and the carbamate resin may be the same or different aldehydes.

[0024] For the rubber compound, a novolac resin is preferably used, which is made from phenol, formaldehyde and a carbamate resin made from butylurethane and formaldehyde (butylcarbamate-functionalized phenol-formaldehyde resin).

[0025] The rubber compound contains at least one etherified melamine resin, which forms a secondary network for good adhesion and hardness.

[0026] Preferably, the etherified melamine resin is hexamethoxymethylmelamine (HMMM). This is a common, commercially available melamine resin that forms a good resin network. HMMM is used, for example, as a technical product – often on an inert support – with a methylation degree < 6.

[0027] The rubberizing mixture according to the invention contains at least one organic cobalt salt. This can be, for example, cobalt stearate, borate, borate alkanoate, naphthenate, rhodinate, octoate, adipate, etc. Several cobalt salts can also be used in the mixture.

[0028] Preferably, the rubberizing mixture contains 0.2 to 2 phr of the organic cobalt salt.

[0029] The sulfur-curable rubber compound contains other components commonly used in the rubber industry, in particular at least one rubber. Diene rubbers can be used as the rubbers. Diene rubbers include all rubbers with an unsaturated carbon chain that are at least partially derived from conjugated dienes.

[0030] The rubber compound can contain polyisoprene (IR, NR) as diene rubber. This 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 > 90 wt.% is preferred. Such polyisoprene can be obtained by stereospecific polymerization in solution with Ziegler-Natta catalysts or using finely divided lithium alkyls. Alternatively, natural rubber (NR) is such a cis-1,4-polyisoprene, with a cis-1,4 content greater than 99 wt.%. Natural rubber refers to 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)).

[0031] If the rubber compound contains polybutadiene (BR) as the diene rubber, it can be cis-1,4-polybutadiene. The use of cis-1,4-polybutadiene with a cis-1,4 content greater than 90 wt% is preferred; this can be produced, for example, by solution polymerization in the presence of rare-earth catalysts.

[0032] Other diene rubbers that can be used include vinyl polybutadiene and styrene-butadiene copolymers. These vinyl polybutadienes and styrene-butadiene copolymers can be solution-polymerized (styrene)-butadiene copolymers (S-(S)BR) with a styrene content (based on the polymer) of approximately 0 to 45 wt.% and a vinyl content (content of 1,2-bonded butadiene, based on the total polymer) of 10 to 90 wt.%, which can be produced, for example, using lithium alkyls in an organic solvent. The S-(S)BRs can also be coupled and end-group modified. Emulsion-polymerized styrene-butadiene copolymers (E-SBR) as well as mixtures of E-SBR and S-(S)BR can also be used. The styrene content of E-SBR is approximately 15 to 50 wt% and the types known from the prior art, which were obtained by copolymerization of styrene and 1,3-butadiene in aqueous emulsion, can be used.

[0033] The diene rubbers used in the mixture, particularly the styrene-butadiene copolymers, can also be used in partially or fully functionalized form. Functionalization can be achieved with groups that can interact with the fillers used, especially with fillers containing OH groups. These functionalizations can include, for example, hydroxyl groups and / or epoxy groups and / or siloxane groups and / or amino groups and / or phthalocyanine groups and / or carboxyl groups and / or silane sulfide groups. The diene rubbers can also be coupled, either additionally or alternatively.

[0034] In addition to the diene rubbers mentioned, the mixture may also contain other types of rubber, such as styrene-isoprene-butadiene terpolymer, butyl rubber, halobutyl rubber or ethylene propylene diene rubber (EPDM).

[0035] Regenerate (reclaim) can also be added to the rubber compound as a processing aid and to reduce the cost of the mixture.

[0036] The rubber compound can contain various fillers, such as carbon black, silicas, aluminosilicates, chalk, starch, magnesium oxide, titanium dioxide or rubber gels in typical quantities, and the fillers can be used in combination.

[0037] When carbon black is used in the rubber compound, it is preferably types that have a CTAB surface area (according to ASTM D 3765) of more than 30 m² / g. These are easy to mix in and ensure low heat build-up.

[0038] If silicas are present in the mixture, they can be the silicas commonly used in tire rubber compounds. 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 / g, preferably 110 to 250 m² / g. Both conventional silicas, such as Evonik's VN3 (trade name), and highly dispersible silicas, so-called HD silicas (e.g., Evonik's Ultrasil 7000), can be used.

[0039] If the rubber compound contains silica or other polar fillers, silane coupling agents can be added to the compound to improve processability and to bind the polar filler to the rubber. The silane coupling agents react with the surface silanol groups of the silica or other polar groups during the mixing of the rubber or rubber compound (in situ) or even before the filler is added to the rubber as a pretreatment (pre-modification). Any silane coupling agents known to those skilled in the art for use in rubber compounds can be used as silane coupling agents.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 exhibit as a second functional group a group which, if necessary after cleavage, can undergo 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⁺- (with 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... B. 3,3'-Bis(triethoxysilylpropyl)tetrasulfide (TESPT), the corresponding disulfide or mixtures of the sulfides with 1 to 8 sulfur atoms with different contents of the various sulfides, can be used.Silane coupling agents can also be added as a mixture with carbon black, such as TESPT on carbon black (trade name X50S from Evonik). Blocked mercaptosilanes, such as those known 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. Suitable examples include silanes marketed under the name NXT in various formulations by Momentive, USA, or those marketed under the name VP Si 363 by Evonik Industries. So-called "silated core polysulfides" (SCP, polysulfides with silylated core) can also be used, which are described, for example, in US 20080161477 A1 and EP 2 114 961 B1.

[0040] Furthermore, the rubber compound according to the invention can contain conventional additives in conventional proportions by weight. These additives include plasticizers, such as glycerides, Faktisse, hydrocarbon resins, aromatic, naphthenic or paraffinic mineral oil plasticizers (e.g., MES (mild extraction solvate) or TDAE (treated distillate aromatic extract)), oils based on renewable raw materials (such as rapeseed oil, terpene oils (e.g., orange oils) or Faktisse), so-called BTL oils (as disclosed in DE 10 2008 037714 A1) or liquid polymers (such as liquid polybutadiene)); antioxidants, such as... B. N-Phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD), N-Isopropyl-N'-phenyl-p-phenylenediamine (IPPD), 2,2,4-Trimethyl-1,2-dihydroquinoline (TMQ) and other substances, such as those known from J. Schnetger, Lexikon der Kautschuktechnik, 2nd edition, Hüthig Buch Verlag, Heidelberg, 1991, pp. 42-48, activators, such as

[0041] Zinc oxide and fatty acids (e.g. stearic acid), waxes, adhesive resins such as hydrocarbon resins and rosin, and masticating aids such as 2,2'-dibenzamidodiphenyl disulfide (DBD).

[0042] Vulcanization is carried out in the presence of sulfur and / or sulfur donors, some of which can also act as vulcanization accelerators. Sulfur or sulfur donors are added to the rubber compound in the final mixing step in quantities customary by those skilled in the art (0.4 to 8 phr). To improve adhesion, particularly to textile reinforcements, the rubber compound preferably contains less than 5 phr of sulfur.

[0043] Furthermore, the rubber compound may contain vulcanization-modifying substances such as vulcanization accelerators, vulcanization retarders, and vulcanization activators in typical quantities to control the required time and / or temperature of vulcanization and to improve the vulcanizate properties. The vulcanization accelerators may be selected, for example, from the following accelerator groups: thiazole accelerators such as 2-mercaptobenzothiazole, sulfenamide accelerators such as benzothiazyl-2-cyclohexylsulfenamide (CBS), benzothiazyl-2-tert-butylsulfenamide (TBBS), and benzothiazyl-2-dicyclohexylsulfenamide (DCBS), guanidine accelerators such as N,N'-diphenylguanidine (DPG), dithiocarbamate accelerators such as zinc dibenzyldithiocarbamate, disulfides, and thiophosphates. The accelerators can also be used in combination with each other, which can result in synergistic effects.Other network-forming systems, such as Vulkuren ®< , Duralink ®< , Perkalink ®< or systems as described in WO 2010 / 049261 A2, can also be used in the rubber compound.

[0044] The vulcanization accelerators can be used in typical quantities. According to an advantageous embodiment of the invention, the rubber compound contains 0.8 to 1.5 phr of benzothiazolyl-2-dicyclohexylsulfenamide (DCBS) as a vulcanization accelerator and less than 0.5 phr of other vulcanization accelerators. Using DCBS as a vulcanization accelerator results in a further improvement in adhesion.

[0045] The rubber compound according to the invention is produced in a conventional manner, whereby a base mixture containing all components except the vulcanization system (sulfur and vulcanization-influencing substances) is first produced in one or more mixing stages, and the finished mixture is then produced by adding the vulcanization system. The mixture is then further processed.

[0046] The rubber compound can be used in a wide variety of rubber products that contain reinforcing elements. These rubber products can include, for example, drive belts, conveyor belts, hoses, rubberized fabrics, or air springs.

[0047] The rubber compound is preferably used in vehicle tires. There, it can be used, for example, as a rubber coating for textile or metallic reinforcing elements. These textile reinforcing elements can consist of materials such as aramid, polyester, polyamide, rayon, or hybrid cords made from these materials.

[0048] The rubber compound can be used for rubberizing a wide variety of tire components, such as the bead core, bead covers, bead reinforcements, belt, carcass, or belt bands. It can also be used for other compounds closely related to structural components, such as bead liners, squeegees, belt edge pads, shoulder pads, tread base plates, or other body compounds. Furthermore, several components within a single tire can be provided with the compound according to the invention. The production of the pneumatic tires according to the invention is carried out using a method known to those skilled in the art.

[0049] Preferably, the rubber compound is used as carcass rubber, where the good tensile strength and the good adhesion values ​​between the reinforcing material and the rubber compound lead to a long service life of the vehicle pneumatic tire.

[0050] Alternatively or additionally, the rubber compound can also be used as a belt rubber compound, which in turn positively influences the service life of the vehicle pneumatic tire.

[0051] The invention will now be explained in more detail with reference to the table below.

[0052] Table 1 shows mixtures for rubber coating of steel cord.

[0053] In the mixtures listed in Table 1, resorcinol was replaced as an adhesion promoter by a novolac resin, which is produced from phenol, formaldehyde, and a carbamate resin of butylurethane and formaldehyde (butylcarbamate-functionalized phenol-formaldehyde resin), and the amounts of both the novolac resin and the HMMM were varied. Furthermore, an organic cobalt salt was added to the mixtures according to the invention. The vulcanization accelerators were also varied.

[0054] The mixture was prepared under normal conditions by producing a base mixture and then the finished mixture in a laboratory tangential mixer.

[0055] The turnover times of 90% turnover (t 90 , vulcanization time) were determined using a rotorless vulcanometer (MDR = Moving Disc Rheometer) according to DIN 53 529 at vulcanization of 160 °C.

[0056] Test specimens were produced from the mixtures by optimal vulcanization under pressure at 160 °C, and material properties typical for the rubber industry were determined using these test specimens with the test procedures specified below. Shore A hardness at room temperature according to DIN ISO 7619-1; rebound elasticity at 70 °C according to DIN 53 512; tensile strength at room temperature according to DIN 53 504; elongation at break at room temperature according to DIN 53504

[0057] Furthermore, adhesion tests were performed with the mixtures from Table 1 on brass-plated steel cord (2 x 0.3 HT) according to ASTM 2229 / D1871 without aging (vulcanization: 20 min at 160 °C, embedding length in the rubber compound: 10 mm, pull-out speed: 125 mm / min). The pull-out force and coverage were determined. For the pull-out force, the value for mixture 1 was set to 100%; the values ​​for the other mixtures were referenced to mixture 1. Table 1 Components Unit 1 2 3 4 5 6 7 8 natural rubber phr 100 100 100 100 100 100 100 100 soot phr 55 55 55 55 55 55 55 55 Silica phr 15 15 15 15 15 15 15 15 Plasticizers, anti-aging agents phr 5 5 5 5 5 5 5 5 Vulcanization activators phr 10 10 10 10 10 10 10 10 Cobalt stearate phr - - 1,3 1,3 1,3 1,3 1,3 1,3 Resorcin phr 3 - 3 - 3 - 1,5 - butylcarbamate-functionalized phenol formalaldehyde resin a)< phr - 3 - 3 - 3 - 1,5 HMMM b)< phr 4,61 4,61 4,61 4,61 4,61 4,61 2,31 2,31 TBBS accelerator phr 0,6 0,6 0,6 0,6 - - - - DCBS accelerator phr 0,6 0,6 0,6 0,6 1,2 1,2 1,2 1,2 sulfur phr 6 6 6 6 6 6 6 6 Characteristics t 90 min 8,2 13,4 7,3 10,3 8,1 11,7 8,5 9,4 Hardness at RT Shore A 75 78 78 80 76 78 75 75 Rebound strength at 70 °C % 50 51 50 48 49 49 50 49 Tensile strength at RT MPa 15,8 17,7 15,9 18 16 17 17 19 Elongation at break % 326 358 313 361 320 366 350 424 Pull-out force (unaged) % 100 97 102 115 109 120 122 125 Coverage (unaged) % 95 91 94 93 95 94 96 95 a)< Alnovol ®< PN 760 / Past, from Allnex Netherlands BV b)< Hexamethoxymethylmelamine 65% on silica

[0058] Mixtures 1, 2, 3, 5 and 7 are comparison mixtures. Mixtures 4, 6 and 8 represent mixtures according to the invention.

[0059] In the steel cord rubbers according to the invention, as shown in Table 1, a significant improvement in adhesion is observed when using butylcarbamate-functionalized phenol-formaldehyde resin and HMMM in combination with cobalt stearate (see mixture 4). Furthermore, the heating time t90 can be reduced, resulting in cost and time savings in product manufacturing. If, according to mixture 6, between 0.8 and 1.5 phr of benzothiazolyl-2-dicyclohexylsulfenamide (DCBS) and less than 0.5 phr of other vulcanization accelerators are used, the adhesion can be further improved.

[0060] Reducing the amounts of butylcarbamate-functionalized phenol-formaldehyde resin and HMMM (see mixture 8) leads to a further improvement in adhesion, while surprisingly also significantly increasing the elongation at break and tensile strength. This results in improved durability of the rubberized reinforcement elements and the products manufactured from them.

Claims

1. Sulfur-crosslinkable rubberization mixture for metallic strength members containing - at least one novolac resin comprising alkyl urethane units and produced by reaction of a phenolic compound, an aldehyde and a carbamate resin, wherein the carbamate resin is produced by reaction of alkyl urethane with an aldehyde, and - at least one etherified melamine resin, characterized in that said mixture contains at least one organic cobalt salt.

2. Sulfur-crosslinkable rubberization mixture according to Claim 1, characterized in that it contains - less than 2.5 phr (parts by weight, based on 100 parts by weight of the total rubbers in the mixture) of at least one novolac resin comprising alkyl urethane units and produced by reaction of a phenolic compound, an aldehyde and a carbamate resin, wherein the carbamate resin is produced by reaction of alkyl urethane with an aldehyde, and - less than 2.5 phr of at least one etherified melamine resin.

3. Sulfur-crosslinkable rubberization mixture according to Claim 1 or 2, characterized in that it contains - 1.2 to 1.8 phr of at least one novolac resin comprising alkyl urethane units and produced by reaction of a phenol compound, an aldehyde and a carbamate resin, wherein the carbamate resin is produced by reaction of alkyl urethane with an aldehyde, and - 1.2 to 1.8 phr of at least one etherified melamine resin.

4. Sulfur-crosslinkable rubberization mixture according to at least one of the preceding claims, characterized in that the proportions of the novolac resin and of the etherified melamine resin sum to less than 5 phr, preferably 2.5 to 3.5 phr.

5. Sulfur-crosslinkable rubberization mixture according to at least one of the preceding claims, characterized in that it is free from resorcinol.

6. Sulfur-crosslinkable rubberization mixture according to at least one of the preceding claims, characterized in that the phenolic compound is phenol.

7. Sulfur-crosslinkable rubberization mixture according to at least one of the preceding claims, characterized in that the alkylurethane is butylurethane.

8. Sulfur-crosslinkable rubberization mixture according to at least one of the preceding claims, characterized in that the aldehyde is formaldehyde.

9. Sulfur-crosslinkable rubberization mixture according to at least one of the preceding claims, characterized in that the etherified melamine resin is hexamethoxymethylmelamine (HMMM).

10. Sulfur-crosslinkable rubberization mixture according to at least one of the preceding claims, characterized in that it contains 0.2 to 2 phr of the at least one organic cobalt salt.

11. Sulfur-crosslinkable rubberization mixture according to at least one of the preceding claims, characterized in that it contains as vulcanization accelerator 0.8 to 1.5 phr of benzothiazyl-2-dicyclohexylsulfenamide (DCBS) and less than 0.5 phr of other vulcanization accelerators.

12. Pneumatic vehicle tire comprising a sulfur-crosslinked rubberization mixture according to Claim 1.

13. Pneumatic vehicle tire according to Claim 12, characterized in that it comprises a carcass rubberization composed of the rubberization mixture.

14. Pneumatic vehicle tire according to Claim 12 or 13, characterized in that it comprises a belt rubberization composed of the rubberization mixture.