DE102013106476A1 - rubber compound - Google Patents

Abstract

The invention relates to a rubber mixture, in particular for treads for vehicle tires, and a vehicle tire. The rubber mixture contains at least the following constituents: - 50 to 100 phr of at least one styrene-butadiene rubber and - 0 to 50 at least one further diene rubber and - 40 to 130 phr of at least one carbon black and - 0.25 to 0.95 phr sulfur and - 1 to 3 phr N-tert-butyl-2-benzothiazylsulfenamide (TBBS) and - 1 to 4 phr tetrabenzylthiuram disulfide (TBzTD).

Description

The invention relates to a rubber composition, in particular for treads of vehicle tires, and a vehicle tire.

The rubber composition of the tread highly determines the ride characteristics of a tire, especially a pneumatic vehicle tire. The term vehicle tires are understood in the present document pneumatic vehicle tires, solid rubber tires and two-wheeled tires.

Likewise, the rubber compounds found in belts, hoses and straps, especially in the mechanically heavily stressed areas, are essentially responsible for the stability and longevity of these rubber articles. Therefore, very high demands are placed on these rubber compounds for pneumatic vehicle tires, belts, belts and hoses.

In order to influence the mixing and vulcanizate properties, a wide variety of additives are added to the mixtures and / or special polymers are used. Fillers which may be mentioned by way of example at this point are fillers (for example carbon black), plasticizers, aging inhibitors and sulfur, accelerator and activator crosslinking systems. If a property is improved by varying the mixture, this often results in a deterioration of another property, so that certain conflicting goals exist. For mixtures for treads of vehicle tires such goal conflicts exist, for example, in terms of the abrasion behavior and the increased heat build-up, which causes a poorer resilience, thus a worse rolling resistance. Above all, variations in the composition of the mixture, and in particular the modification or adaptation of the additives, in order to achieve an improved level of the properties usually having a contrary behavior, are used to solve these conflicting goals.

An important group of additives that has an influence on the vulcanization rate and the physical properties of vulcanizates is the group of vulcanization accelerators. For the vulcanization of rubber compounds which are used for the production of vehicle tires, various vulcanization accelerator groups known to the person skilled in the art are available, which can also be used in combination with one another, whereby synergistic effects may result.

The vulcanization accelerators serve to activate the sulfur used as a vulcanizing agent. The dosage of sulfur and vulcanization accelerator is adjusted individually to the properties of the tire rubber mixture to be achieved. These properties to be achieved are achieved by the network resulting from the vulcanization, e.g. between polymer and fillers, so that the type and degree of crosslinking in view of the physical properties of the vulcanizates can be given great importance.

The state of the art with regard to vulcanization or crosslinker system will now be described in more detail with reference to the following publications:

The DE 2536674 A1 describes a crosslinkable rubber composition containing siliceous fillers and a method for crosslinking. This very generally claims a crosslinkable rubber mixture which contains at least 1 to 300 parts by weight of a siliceous filler, 0 to 300 parts by weight of carbon black and at least one known per se for vulcanization Vulkanisationsbeschleuniger in amounts of 0.02 to 10 parts by weight and at least one organosilane.

The DE 4036420 A1 discloses vulcanizates for technical rubber articles without nitrosamine toxicity which contain a medium or low active carbon black in combination with special thiuram and mercapto vulcanizing agents, whereby small amounts of elemental sulfur are required for vulcanization or crosslinking.

From the EP 0530590 B1 For example, a process for the preparation of diene rubber vulcanizates having very high aging stability and reversion resistance is known. The diene rubber vulcanizates here contain 1 to 2.5 parts of mercapto accelerator or 0.2 to 0.8 parts of sulfenamide accelerator or 0.3 to 2.5 parts of mercapto accelerator and 0.1 to 0.8 parts of sulfenamide accelerator. 0.1 to 0.2 parts of sulfur are used per 100 parts of rubber, preferably an oil-extended diene rubber.

In the WO 2009/147006 A 1 discloses a rubber composition containing a vulcanization system of sulfur donors and sulfur and vulcanization accelerators and predominantly silica as a filler. Such a rubber mixture shows improved abrasion properties, whereby the rolling resistance properties deteriorate in the conflict of objectives.

The present invention is based on the object of providing a rubber mixture which, in comparison to the prior art, has a further improvement of the abrasion behavior and at the same time improved wet braking properties, without the other tire properties, in particular the rolling resistance behavior, being significantly adversely affected.

• – 50 bis 100 phr zumindest eines Styrol-Butadien-Kautschuks und
• – 0 bis 50 zumindest eines weiteren Dienkautschuks und
• – 40 bis 130 phr zumindest eines Rußes und
• – 0,25 bis 0,95 phr Schwefel und
• – 1 bis 3 phr N-tert.Butyl-2-benzothiazylsulfenamid (TBBS) und
• – 1 bis 4 phr Tetrabenzylthiuramdisulfid (TBzTD).

This object is achieved by a rubber mixture containing at least the following constituents:

• - 50 to 100 phr of at least one styrene-butadiene rubber and
• - 0 to 50 at least one further diene rubber and
• - 40 to 130 phr of at least one soot and
• - 0.25 to 0.95 phr sulfur and
• - 1 to 3 phr of N-tert-butyl-2-benzothiazyl sulfenamide (TBBS) and
• - 1 to 4 phr of tetrabenzylthiuram disulfide (TBzTD).

Surprisingly, the combination of the abovementioned constituents shows improved wet grip properties and improved abrasion behavior in comparison with the prior art, the rubber mixture in particular having a higher abrasion resistance and thus a lower material loss when subjected to corresponding stress compared with the prior art.

According to the invention, the rubber mixture contains at least one styrene-butadiene rubber.

The styrene content of the styrene-butadiene rubber is 5 to 70 wt .-%, preferably 12 to 70 wt .-%, based on the total mass of the styrene-butadiene rubber. The solution-polymerized styrene-butadiene rubber preferably has a vinyl content of 5 to 70% by weight, particularly preferably 10 to 70% by weight.

The styrene content and the vinyl content of the polymers discussed in the context of the present invention are determined by means of ¹³ C-NMR (deuterochloroform CDCl ₃ solvent, nuclear magnetic resonance) and comparison with data from infrared spectrometry (IR, Nicolet FT-IR spectrometer, KBr window 25 mm diameter x 5 mm, 80 mg sample in 5 mL 1,2-dichlorobenzene). The determination of the glass transition temperature (T _g ) is carried out by means of dynamic difference calorimetry (DSC according to DIN 53765: 1994-03 respectively. ISO 11357-2: 1999-03 , Calibrated DSC with low temperature equipment, calibration by instrument type and manufacturer's instructions, sample in aluminum crucible with aluminum lid, cooling to temperatures lower than -120 ° C at 10 ° C / min).

The term phr (parts per hundred parts of rubber by weight) used in this document is the quantity used in the rubber industry for mixture formulations. The dosage of the parts by weight of the individual substances is referred to in this document to 100 parts by weight of the total mass of all high molecular weight and thus solid rubbers present in the mixture.

The styrene-butadiene rubber may be produced by emulsion polymerization or solvent polymerization. It is preferably an ESBR or an ESBR mixture.

The rubber mixture according to the invention contains at least one styrene-butadiene rubber in amounts of 50 to 100 phr, preferably 80 to 100 phr.

The rubber mixture according to the invention additionally contains 0 to 50 phr of at least one further rubber.

The at least one further rubber is selected from the group consisting of natural polyisoprene and / or synthetic polyisoprene and / or butadiene rubber and / or solution-polymerized styrene-butadiene rubber and / or emulsion-polymerized styrene-butadiene rubber and / or liquid rubbers and 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 isoprene-butadiene copolymer and / or or hydrogenated styrene-butadiene rubber.

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 straps, belts and hoses.

More preferably, the further diene rubber is selected from the group consisting of synthetic polyisoprene and natural polyisoprene and polybutadiene. The further diene rubber is preferably natural polyisoprene. Hereby, a particularly good processability (extrudability, miscibility, etc.) of the rubber mixture according to the invention is achieved.

According to an advantageous embodiment of the invention, the rubber mixture contains 1 to 10 phr, preferably 2 to 6 phr of at least one natural polyisoprene.

The rubber mixture according to the invention contains 40 to 130 phr, preferably 70 to 130 phr, more preferably 70 to 110 phr, most preferably 80 to 90 phr, of at least one carbon black as filler. In this case, all known in the art soot types are conceivable.

However, preference is given to using a carbon black which has an iodine adsorption number according to ASTM D 1510 from 80 to 180 g / kg, preferably 80 to 140 g / kg, more preferably 80 to 100 kg / g, and a DBP number according to ASTM D2414 from 115 to 200 ml / 100 g, preferably 118 to 200 ml / 100g, more preferably 118 to 150 ml / 100g. Preferably, therefore, a so-called high active carbon black is used whose DBP number is greater than 118 ml / 100 g. Hereby particularly good abrasion and wet grip properties are achieved for use in the vehicle tire, the other properties, in particular rolling resistance and dry braking, remain at approximately the same level and / or even improved.

The rubber mixture according to the invention may contain, in addition to carbon black, other known polar and / or nonpolar fillers.

Carbon black is preferably present in the rubber mixture according to the invention as sole filler or as main filler, that is to say that the amount of carbon black is significantly greater than the amount of optionally contained other fillers. In the event that, in addition to carbon black, another filler is included, this is preferably silica. Thus, it is also conceivable that the rubber composition according to the invention contains carbon black and silica, such as e.g. 40 to 130 phr of carbon black combined with 0.1 to 10 phr of silica.

The silicas may be the silicas known to those skilled in the art which are suitable as a filler for tire rubber mixtures. However, it is particularly preferred if a finely divided, precipitated silica is used, which has a nitrogen surface (BET surface area) (according to DIN ISO 9277 and DIN 66132 ) from 35 to 350 m ² / g, preferably from 35 to 260 m ² / g, more preferably from 100 to 260 m ² / g and most preferably from 130 to 235 m ² / g, and a CTAB surface (according to ASTM D 3765 ) from 30 to 400 m ² / g, preferably from 30 to 250 m ² / g, particularly preferably from 100 to 250 m ² / g and very particularly preferably from 125 to 230 m ² / g. Such silicas lead z. B. in rubber mixtures for tire tread to particularly good physical properties of the vulcanizates. In addition, there may be advantages in the mixing processing by reducing the mixing time with constant product properties, which lead to improved productivity. As silicas can thus z. B. both those of the type Ultrasil ^® VN3 (trade name) from Evonik and highly dispersible silicas, so-called HD silicas (eg Zeosil ^® 1165 MP from Rhodia) are used.

To improve the processability and to attach the silica and other optional polar fillers to the diene rubber silane coupling agents can be used in rubber mixtures. The silane coupling agents react with the superficial silanol groups of 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 (pre-modification). All silane coupling agents known to the person skilled in the art for use in rubber mixtures can be used as silane coupling agents. Such coupling agents known from the prior art are bifunctional organosilanes which have on the silicon atom at least one alkoxy, cycloalkoxy or phenoxy group as a leaving group and have as other functionality a group which may optionally undergo a chemical reaction with the double bonds of the polymer after cleavage. In the latter group may be z. These may be, for example, the following chemical groups: -SCN, -SH, -NH ₂ or -S _x - (where x = 2 to 8).

Thus, as silane coupling agents z. For example, 3-mercaptopropyltriethoxysilane, 3-thiocyanato-propyltrimethoxysilane or 3,3'-bis (triethoxysilylpropyl) polysulfides having 2 to 8 sulfur atoms, such as. For example, 3,3'-bis (triethoxysilylpropyl) tetrasulfide (TESPT), the corresponding disulfide (TESPD) or mixtures of the sulfides having 1 to 8 sulfur atoms with different contents of the various sulfides, are used. TESPT can, for example as a mixture with carbon black (trade name X50S ^® from Evonik) are added. Preference is given to using a silane mixture which comprises 40 to 100% by weight of disulfides, particularly preferably 55 to 85% by weight of disulfides and very particularly preferably 60 to 80% by weight of disulfides. Such a mixture is obtainable, for example, under the trade name Si ^261® from Evonik, which is available, for example, in the DE 102006004062 A1 is described. Also blocked mercaptosilanes, as z. B. from the WO 99/09036 are known, can be used as a silane coupling agent. Also silanes, as in the WO 2008/083241 A1 , of the WO 2008/083242 A1 , of the WO 2008/083243 A1 and the WO 2008/083244 A1 can be used, can be used. Suitable for. B. silanes, which are sold under the name NXT in various variants by the company Momentive, USA, or those sold under the name VP Si 363 ^® by Evonik Industries.

Most preferably, however, the rubber composition is free of further fillers and, i. In this preferred embodiment, the rubber mixture contains 0 phr of another filler. Thus, in this embodiment, no dosage of a second filler is necessary.

Zinc oxide is not considered a filler in the present invention.

0 to 70 phr, preferably 0.1 to 60 phr, preferably 10 to 50 phr, of at least one plasticizer may be present in the rubber mixture. This plasticizer is selected from the group consisting of mineral oils and / or synthetic plasticizers and / or fatty acids and / or fatty acid derivatives and / or resins and / or ingredients and / or glycerides and / or terpenes and / or biomass-to-liquid oils (BTL oils) and / or rubber-to-liquid oils (RTL oils) and / or liquid polymers, with mineral oils being particularly preferred.

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 oil.

• a) Alterungsschutzmittel, wie z. B. N-Phenyl-N'-(1,3-dimethylbutyl)-p-phenylendiamin (6PPD), N,N'-Diphenyl-p-phenylendiamin (DPPD), N,N'-Ditolyl-p-phenylendiamin (DTPD), N-Isopropyl-N’-phenyl-p-phenylendiamin (IPPD), 2,2,4-Trimethyl-1,2-dihydrochinolin (TMQ),
• b) Aktivatoren, wie z. B. Zinkoxid und Fettsäuren (z. B. Stearinsäure),
• c) Wachse,
• d) Harze, insbesondere Klebharze, und
• e) Mastikationshilfsmittel, wie z. B. 2,2'-Dibenzamidodiphenyldisulfid (DBD).

Furthermore, the rubber mixture according to the invention may contain customary additives in customary parts by weight. 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. Zinc oxide and fatty acids (eg stearic acid),
• c) waxes,
• d) resins, in particular adhesive resins, and
• e) Mastikationshilfsmittel such. B. 2,2'-Dibenzamidodiphenyldisulfid (DBD).

In particular, when using the rubber composition according to the invention for the inner components of a tire or a technical rubber article, which have direct contact with existing reinforcements, the rubber mixture is usually added to a suitable adhesive system, often in the form of adhesive resins.

The proportion of the total amount of further additives is 3 to 150 phr, preferably 3 to 100 phr and more preferably 5 to 80 phr. In the total amount of other additives are still 0.1 to 10 phr, preferably 0.2 to 8 phr, more preferably 0.2 to 4 phr, zinc oxide (ZnO). These may be any of the types of zinc oxide known to those skilled in the art, e.g. ZnO granules or powder. The conventionally used zinc oxide usually has a BET surface area of less than 10 m² / g. However, it is also possible to use so-called nano-zinc oxide having a BET surface area of 10 to 60 m 2 / g.

The vulcanization is carried out according to the invention in the presence of comparatively small amounts of elemental sulfur in combination with tetrabenzylthiuram disulfide (TBzTD) as sulfur donor with the aid of at least N-tert-butyl-2-benzothiazylsulfenamide (TBBS) as a vulcanization accelerator.

The amount of added elemental sulfur, also called free sulfur, is 0.25 to 0.95 phr, preferably 0.35 to 0.7 phr, more preferably 0.35 to 0.6 phr. The amount of added sulfur donor TBzTD is 1 to 4 phr, preferably 1.5 to 4 phr, more preferably 1.5 to 3 phr.

The amount of added N-tert-butyl-2-benzothiazyl sulfenamide (TBBS) as a vulcanization accelerator is 1 to 3 phr, preferably 1 to 2.5 phr, more preferably 1.3 to 2.4 phr.

According to an advantageous development, the rubber mixture according to the invention contains 0.01 to 0.15 phr of comparatively small amounts of the accelerator 2-mercaptobenzothiazole. This results in an economically sensible heating kinetics of the rubber mixture according to the invention in the vulcanization.

According to a preferred development of the invention, several accelerators are contained in the rubber mixture.

Particularly preferred is the use of the accelerator TBBS in combination with diphenylguanidine (DPG).

The preparation of the rubber mixture according to the invention is carried out according to the usual method in the rubber industry, in which first in one or more mixing stages, a base mixture with all components except the vulcanization system (sulfur and vulcanisationsbeeinflussende substances) is prepared. By adding the vulcanization system, consisting of sulfur and sulfur donors and the aforementioned accelerators, in a final mixing stage, the finished mixture is produced. The ready mix is e.g. further processed by an extrusion process and brought into the appropriate form.

Another object of the present invention is to provide a vehicle tire characterized by improved abrasion performance and wet grip properties. This object is achieved in that the vehicle tire in at least one component contains the rubber mixture according to the invention as described above. All the above explanations regarding the components and their characteristics apply.

The component is preferably a tread. As known to those skilled in the art, the abrasion resistance and wet grip properties of vehicle tires are critically dependent on the abrasion performance of the rubber compound of the tread. The vehicle tire is preferably a pneumatic vehicle tire, particularly preferably for passenger cars.

Another object of the present invention is to improve the abrasion performance and wet grip properties of vehicle tires. This object is achieved according to the invention by the use of the rubber mixture described above with all embodiments and features in vehicle tires.

The invention will now be explained in more detail with reference to comparative and exemplary embodiments, which are summarized in Table 1.

The comparison mixtures are with V, the mixtures according to the invention are marked with E.

• • Shore-A-Härte bei Raumtemperatur (RT) gemäß DIN ISO 7619-1
• • Rückprallelastizität bei Raumtemperatur (RT) gemäß DIN 53 512

Mixture preparation was carried out under normal conditions in two stages in a tangential internal mixer. From all mixtures test specimens were prepared by optimal vulcanization under pressure at 160 ° C and determined with these specimens for the rubber industry typical material properties with the test methods given below.

• • Shore A hardness at room temperature (RT) according to DIN ISO 7619-1
• • Rebound resilience at room temperature (RT) according to DIN 53 512

Further, the comparative blends and rubber blends of the present invention were incorporated by art-known procedures by extrusion, laying on a respective green tire and then vulcanizing the green tires in the tread of vehicle tires.

Subsequently, the vehicle tires were tested for the following properties:

Furthermore, 205/55 R16 pneumatic vehicle tires were manufactured with a tread of the respective mixtures and the tires were used for wet braking on asphalt (low μ) and asphalt (high μ) and for braking on dry asphalt (dry braking) and for rolling resistance. Further, the abrasion was measured by the weight loss of the respective tires.

The determined values were converted into performance, whereby the comparison mixture V1 was normalized to 100% performance for each property tested. All other mixing powers relate to this comparison mixture V1. Here, values <100% mean a deterioration in properties, while values> 100% are an improvement.

Table 1

Substances used from Table 1:

• ^a) SBR: styrene-butadiene rubber: SBR 1500, ESBR INTOL 1500, Polimeri Europa, not oil-drawn.
• ^b) SBR: styrene-butadiene rubber: SBR 1723, ESBR INTOL 1723, Polimeri Europa, oil-drawn

As can be seen from Table 1, the rubber mixtures E1, E2 and E3 according to the invention have significantly improved wet-braking properties and a significantly higher abrasion resistance in the tire test with respect to their respective reference V1, V2 or V3. At the same time rolling resistance and dry braking are not significantly adversely affected.

Thus, it is possible with the rubber mixtures according to the invention to produce vehicle tires, in particular pneumatic vehicle tires, which have an improved abrasion behavior and improved wet braking properties without disadvantages as regards other requirements, such as rolling resistance and dry braking.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 2536674 A1 [0007]
• DE 4036420 A1 [0008]
• EP 0530590 B1 [0009]
• WO 2009147006 A [0010]
• DE 102006004062 A1 [0031]
• WO 99/09036 [0031]
• WO 2008/083241 A1 [0031]
• WO 2008/083242 A1 [0031]
• WO 2008/083243 A1 [0031]
• WO 2008/083244 A1 [0031]

Cited non-patent literature

• DIN 53765: 1994-03 [0016]
• ISO 11357-2: 1999-03 [0016]
• ASTM D 1510 [0026]
• ASTM D 2414 [0026]
• DIN ISO 9277 [0029]
• DIN 66132 [0029]
• ASTM D 3765 [0029]
• DIN ISO 7619-1 [0051]
• DIN 53 512 [0051]

Claims (8)

 Rubber mixture containing at least the following constituents: - 50 to 100 phr of at least one styrene-butadiene rubber and - 0 to 50 at least one further diene rubber and - 40 to 130 phr of at least one soot and - 0.25 to 0.95 phr sulfur and - 1 to 3 phr of N-tert-butyl-2-benzothiazyl sulfenamide (TBBS) and - 1 to 4 phr of tetrabenzylthiuram disulfide (TBzTD). Rubber mixture according to claim 1, characterized in that the carbon black has a DBP number according to ASTM D 2414 of 115 to 200 ml / 100 g. Rubber mixture according to one of claims 1 or 2, characterized in that the rubber mixture is free of silica. Rubber mixture according to one of claims 1 to 3, characterized in that it contains 80 to 100 phr of at least one styrene-butadiene rubber. Rubber mixture according to one of claims 1 to 4, characterized in that it contains 0.01 to 0.15 phr of the accelerator 2-mercaptobenzothiazole. Vehicle tire, characterized in that it contains in at least one component a sulfur-crosslinkable rubber mixture according to one of the preceding claims. Vehicle tire according to claim 7, characterized in that it is the component to a tread.  Use of a rubber composition according to any one of claims 1 to 6 in vehicle tires to improve the abrasion and wet grip properties of vehicle tires.