EP3625288A1

EP3625288A1 - Sulfur-crosslinked rubber mixture for vehicle tires, containing carbon nanotubes (cnts), vehicle tire having the sulfur-crosslinked rubber mixture, and method for producing the sulfur-crosslinked rubber mixture containing carbon nanotubes

Info

Publication number: EP3625288A1
Application number: EP18713170.1A
Authority: EP
Inventors: Nils Walter Hojdis; Carla Recker
Original assignee: Continental Reifen Deutschland GmbH
Current assignee: Continental Reifen Deutschland GmbH
Priority date: 2017-05-15
Filing date: 2018-03-19
Publication date: 2020-03-25
Also published as: DE102017208137A1; WO2018210471A1; CN110678508A; US20210163696A1; US11326028B2

Abstract

The invention relates to a sulfur-crosslinked rubber mixture for vehicle tires, containing carbon nanotubes (CNTs), to a vehicle tire having the sulfur-crosslinked rubber mixture, and to a method for producing the sulfur-crosslinked rubber mixture containing CNTs. The sulfur-crosslinked rubber mixture according to the invention is characterized in that the CNTs are pre-dispersed in at least one polyisoprene. The vehicle tire according to the invention has the sulfur-crosslinked rubber mixture preferably in the tread and/or a sidwall and/or a conductivity strip.

Description

Continental tires Germany GmbH

description

Sulfur-crosslinked rubber mixture for vehicle tires comprising carbon nanotubes (CNT), vehicle tires having the sulfur-crosslinked rubber mixture, and processes for producing the sulfur-crosslinked rubbers

Rubber mixture containing CNT

The invention relates to a sulfur-crosslinked rubber mixture for vehicle tires comprising carbon nanotubes (CNT), a vehicle tire having the sulfur-crosslinked rubber mixture, and a process for preparing the sulfur-crosslinked rubber mixture containing CNT.

The rubber compositions of the individual components of vehicle tires, in particular the composition of the tread, to a large extent determine their driving characteristics.

To influence the mixing and vulcanizing properties, a wide variety of additives are added to the mixtures and / or special polymers are used. Examples of fillers which may be mentioned here are fillers (eg carbon black), plasticizers, aging inhibitors and different crosslinking systems composed of sulfur, accelerator and activator. WO 2012/080160 A1 discloses a rubber compound for treads of vehicle tires, which comprises a masterbatch of carbon nanotubes (CNT;

Carbon nanotube) in ESBR (emulsion-polymerized styrene-butadiene rubber). Such a mixture shows improved traction control under winter conditions, dry handling behavior and rolling resistance compared to a mixture without CNT. The invention is based on the prior art based on the object to provide a sulfur-crosslinked rubber mixture containing carbon nanotubes (CNT), which is characterized by optimized electrical conductivity properties, the other properties, in particular the abrasion behavior remain at the same level or even improved become.

This object is achieved in that the CNT are predispersed in at least one polyisoprene in the sulfur-crosslinked rubber mixture.

Surprisingly, it has been found that the sulfur-crosslinked

Rubber composition thereby has an unexpectedly good electrical conductivity. This effect is particularly evident when compared with rubber blends containing polymer blends of styrene-butadiene rubbers and polyisoprene; in the case where the CNTs are predispersed in at least one polyisoprene (polyisoprene-CNT masterbatch), the surprisingly high electrical conductivity occurs.

At the same time, the remaining tire properties remain at approximately the same level or are even improved, with the abrasion properties of the rubber mixture in particular remaining or even improved at an approximately equal level. Another object underlying the present invention is to provide a vehicle tire having an improvement over the prior art in terms of conductivity.

The object is achieved in that the vehicle tire has at least one component in a component at least one sulfur-crosslinked rubber mixture with the above-mentioned or below detailed features.

Vehicle tires containing the rubber mixture according to the invention in at least one component, preferably at least in the tread and / or at least one side wall and / or at least one conductivity track, have an improved

Conductivity on. If the vehicle tire contains the sulfur-crosslinked rubber mixture according to the invention at least in the tread, the abrasion behavior remains at least at the same level or is also improved. In the case of two-part treads (upper part: cap and lower part: base), the rubber mixture according to the invention can be used both for the cap and for the base. Preferably, at least the cap has at least one

Sulfur-crosslinked rubber mixture according to the invention.

The term "sulfur-crosslinked rubber mixture" is to be understood as meaning a rubber mixture which consists of a rubber final mixture (or rubber raw mixture)

Sulfur vulcanization is made. A sulfur-crosslinked rubber compound is thus a vulcanizate.

In the context of the present invention, a conductivity track is any type of rubber compound known to the person skilled in the art which is suitable for conducting the conductivity between at least two tire components and / or at least one inner tire component and the road surface or other external surfaces with which the tire in FIG Touch comes, make sure. The conductive sheet may be a so-called "carbon center beam" or else a strip which is in the

Shoulder region of the vehicle tire is arranged. Furthermore, the conductive web can also be arranged between an electrically conductive tire component and a tire sensor and thus forward information about the electrical conductivity of the tire to the sensor. In the context 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-wheeled tires.

The rubber mixture according to the invention is also suitable for other components of

Vehicle tires suitable, such. B. in particular the, horn profile, and inner

Tire components. The rubber mixture according to the invention is also for others technical rubber articles, such as bellows, conveyor belts, air springs, straps, belts or hoses, as well as shoe soles.

The components of the sulfur-crosslinked rubber mixture according to the invention are described in more detail below. All embodiments also apply to the vehicle tire according to the invention, the at least one inventive

Having rubber mixture in at least one component. The description of the individual constituents refers to the rubber mixture before vulcanization, ie the sulfur-crosslinkable rubber mixture, unless stated otherwise.

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 in this document is based on 100 parts by weight of the total mass of all rubbers present in the mixture, ie the at least one polyisoprene plus optionally further sulfur-vulcanizable rubbers which are added to the rubber mixture according to the invention.

The subject of the invention is a sulfur-crosslinked one

Rubber mixture containing carbon nanotubes (CNT), which is also known as

Carbon nanotubes or tubes.

In principle, all types of CNT known to the person skilled in the art are included in the subject matter of the invention. Individual CNTs ("discrete carbon nanotubes") have an elongated shape and therefore have a high aspect ratio. The form factor is the quotient of the average length of the CNT divided by the

average diameter of the CNT.

According to a preferred embodiment of the invention, the CNT have a

Form factor of 10 to 200, more preferably 30 to 150, most preferably 50 to 120, on. The dimensions of the CNT are known to those skilled in the art

Scanning Electron Microscopy (SEM).

According to a preferred embodiment of the invention, the CNT have a length of 0.2 μιη to 1.4 μιη, preferably 0.5 μιη to 1 μιη, ie 200 nm to 1400 nm, preferably 500 nm to 1000 nm, on.

It is essential to the invention that the CNTs are predispersed in at least one polyisoprene. Surprisingly, only the predispersion of CNT in at least one polyisoprene results in a surprisingly high electrical conductivity.

By this is meant that the CNT preferably only in at least one

Polyisoprene are predispersed and not additionally masterbatches in the

Rubber mixture are included, in which CNTs are predispersed in a different rubber matrix than polyisoprene. In particular, the inventive

Rubber mixture does not prefer a masterbatch in which CNT are predispersed in ESBR. The presence of plasticizers or other substances in the

Masterbatchen is unaffected, d. H. a polyisoprene-CNT masterbatch may contain other substances, such as plasticizers, s. below. The at least one polyisoprene may be a natural polyisoprene (NR, natural rubber) and / or a synthetic polyisoprene (IR).

All embodiments may be both cis-1,4-polyisoprene and 3,4-polyisoprene. However, preference is given to the use of cis-1,4-polyisoprenes having an iron content of> 90% by weight. For one, such a

Polyisoprene by stereospecific polymerization in solution with Ziegler-Natta

Catalysts or be obtained using finely divided lithium alkyls. On the other hand, natural rubber (NR) is such an iron-1,4-polyisoprene, the cis-1,4-content in natural rubber is greater than 99% by weight.

Furthermore, a mixture of one or more natural polyisoprenes with one or more synthetic polyisoprene (s) is conceivable. According to a preferred embodiment of the invention, the at least one polyisoprene is at least one natural polyisoprene. This results in particularly good properties with regard to the requirements of the rubber mixture for use in at least one tire component with an excellent electrical

Conductivity.

Essential to the invention is that the CNT in the at least one polyisoprene

are predispersed, i. Preferably, the CNT are therefore present as a single, separate CNT in the at least one polyisoprene, but it can not be ruled out that even so

Agglomerates are present. Thus, in the rubber mixture according to the invention, the CNT can be present as a single CNT and possibly also as agglomerates. Both of the separate CNTs as well as the agglomerates can be measured by REM length and

Diameter are determined, which reference is made at this point for details to the statements in WO 2012/080160 AI. In the case of agglomerates, there are bundles of CNTs. Here then an effective form factor "English, effective aspect ratio") as a quotient of the average length (arithmetic mean) and the

Bundle diameter determined. The dispersion of the CNT in the at least one polyisoprene is carried out by methods known to the person skilled in the art, for example in accordance with the following

described method.

As described in US 7785701, the dispersion of CNT can be carried out by shear forces, namely z. By one of the following methods:

Kneading on a roll with a nip of 0.5 mm or less ("open-roll method");

Kneading in a closed-kneading method with a rotor pitch of 1 mm or less;

Kneading in a multi-screw extruding kneading method with a screw pitch of 0.3 mm or less. The incorporation of CNT into a rubber matrix in an internal mixer at 110 ° C for 30 minutes is described in S. Sagar et Incorporated Natural Rubber Composites: Thermal Insulation, Phase Transition and Mechanical Properties "in IACSIT International Journal of Engineering and Technology (June 2014), Vol. 6, No. 3, p.

Further, CNTs may be incorporated into a rubber matrix via a prior wetting with ethanol followed by evaporation of the ethanol, such as

for example in HH Le et of rubber polarity on selective wetting of carbon nanotubes in ternary blends "in eXPRESS Polymer Letters (2015), Vol. 9, No. 11, pp. 960-971.

The CNT and the at least one polyisoprene in which they are predispersed form a masterbatch which may contain other ingredients.

The viscosity of the masterbatch (Mooney ML 1 + 4 at 100 ° C.) is preferably 80 to 120 MU. The content by weight of the CNT in the masterbatch is preferably from 0.1 to 20% by weight, based on the total amount of the masterbatch.

According to a particularly advantageous embodiment of the invention, the proportion of CNT in the masterbatch is 13 to 20 wt .-%, particularly preferably 14 to 18 wt .-%, in particular and for example 15 to 17 wt .-%. With such a concentration of the CNT in the masterbatch of at least one polyisoprene, a good distribution of the CNTs in the polyisoprene and a particularly good electrical conductivities with other good tire properties in the sulfur-crosslinked rubber mixture are achieved.

The masterbatch may, as a further constituent, in particular at least one

Contain softener. The weight fraction of the plasticizer based on the total amount of the masterbatch is in this case preferably 0.1 to 20 wt .-%. According to an advantageous embodiment of the invention, it is 6 to 16 wt .-%, particularly preferably 8 to 14 wt .-%, in particular and for example 9 to 10 wt .-%.

The proportion by weight of the CNT in the masterbatch here is also preferably 0.1 to 20% by weight, based on the total amount of the masterbatch, and according to a particularly advantageous embodiment of the invention 13 to 20% by weight, particularly preferably 14 to 18% by weight. %, in particular and for example 15 to 17 wt .-%.

The amount of CNT in the sulfur-crosslinked rubber compound is preferably 0.1 to 25 phr (MB = rubber + CNT), preferably 0.1 to 15 phr. With such amounts, an improvement of the electrical conductivity at the same time good

Rolling resistance achieved.

According to a preferred embodiment, the inventive

Rubber mixture 0.1 to 2 phr CNT. With this amount, the conflict of objectives is achieved from high electrical conductivity at the same time as low rolling resistance as possible. According to an advantageous embodiment of the invention, the sulfur-crosslinked rubber mixture contains, in addition to the polyisoprene in which the CNTs are predispersed, at least one further sulfur vulcanizable prior to vulcanization and thus at least one further diene rubber.

Diene rubbers are rubbers which are formed by polymerization or copolymerization of dienes and / or cycloalkenes and thus have C = C double bonds either in the main chain or in the side groups.

The at least one further diene rubber is preferably selected from the group consisting of natural polyisoprene and / or synthetic polyisoprene and / or epoxidized polyisoprene and / or butadiene rubber and / or butadiene-isoprene rubber and / or solution-polymerized styrene-butadiene rubber and or emulsion-polymerized styrene-butadiene rubber and / or styrene-isoprene rubber and / or liquid rubbers having a molecular weight M _w greater than 20,000 g / mol 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 fluorinated rubber 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.

In particular nitrile rubber, hydrogenated acrylonitrile-butadiene rubber,

Chloroprene rubber, butyl rubber, halobutyl rubber or ethylene-propylene-diene rubber are used in the manufacture of technical rubber articles such as straps, belts and hoses, and / or shoe soles.

The rubber compound is particularly suitable for vehicle tires, and it can be used in principle in any component, such as in particular the tread, the

Sidewall, the horn profile, as well as in other so-called body components.

For this purpose, the diene rubber is preferably selected from the group consisting of synthetic polyisoprene (IR) and natural polyisoprene (NR) and styrene-butadiene rubber (SBR) and polybutadiene (BR) and butyl rubber (HR) and

Halobutyl rubber.

The diene rubber is particularly preferably selected from the group consisting of synthetic polyisoprene (IR) and natural polyisoprene (NR) and styrene-butadiene rubber (SBR) and polybutadiene (BR),

resulting in particularly good properties in terms of requirements in the

Vehicle tires result.

For the synthetic or natural polyisoprene which may be added as at least one further sulfur crosslinkable rubber, the above apply

Versions regarding the microstructure etc. If in the rubber mixture according to the invention butadiene rubber (= BR,

Polybutadiene) may be any of the types known to those skilled in the art. These include u.a. the so-called high-cis and low-cis types, wherein polybutadiene with an eis content greater than or equal to 90 wt .-% as high-cis type and polybutadiene with an eis content less than 90 wt .-% as low cis type is called. A low-cis polybutadiene is e.g. Li-BR (lithium-catalyzed butadiene rubber) with a cis content of 20 to 50 wt .-%. With a high-cis BR will be particularly good

Abriebeigenschaften and low hysteresis of the rubber mixture achieved.

The employed polybutadiene (s) can be modified with and

Functionalizations endgruppenmodifiziert and / or be functionalized along the polymer chains. The modification may be those having hydroxy groups and / or ethoxy groups and / or epoxy groups and / or siloxane groups and / or amino groups and / or aminosiloxane and / or carboxy groups and / or

Phthalocyanine groups and / or silane-sulfide groups. But there are also other known to the expert person, modifications, as well

Functionalizations referred to, in question. Part of such functionalizations may be metal atoms.

In the case where at least one styrene-butadiene rubber (styrene-butadiene copolymer) is contained in the rubber composition, it may be both

solution-polymerized styrene-butadiene rubber (SSBR) as well

emulsion-polymerized styrene-butadiene rubber (ESBR), wherein a mixture of at least one SSBR and at least one ESBR can be used. The terms "styrene-butadiene rubber" and "styrene-butadiene copolymer" are used synonymously in the context of the present invention.

The styrene-butadiene copolymer used can be end-group-modified with the modifications and functionalizations mentioned above for the polybutadiene and / or be functionalized along the polymer chains. According to an advantageous embodiment of the invention, the rubber mixture contains at least one further reinforcing filler, wherein the ratio of further reinforcing fillers to CNT 1000 is from 1 to 2 to 1.

More preferably, the ratio is 200 to 1 to 2 to 1, most preferably 80 to 1 to 2 to 1.

Under "further reinforcing fillers" are used in the present

Invention understood in principle all fillers that act in a rubber compound reinforcing, so change the viscoelastic properties in particular by interaction with the rubber matrix.

The amount of the at least one further reinforcing filler is preferably from 0.1 to 250 phr, more preferably from 20 to 250 phr, most preferably from 20 to 150 phr.

The further reinforcing filler is preferably at least one carbon black and / or at least one silica.

According to a preferred embodiment of the invention, the rubber mixture contains 0.1 to 250 phr, preferably 2 to 200 phr, more preferably 10 to 100 phr, again preferably 20 to 80 phr of at least one carbon black. In the context of the present invention, all carbon black types known to those skilled in the art are conceivable as carbon blacks. However, preference is given to using a carbon black which has an iodine adsorption number according to ASTM D 1510 of 20 to 180 g / kg, more preferably 30 to 140 g / kg, and a DBP number according to ASTM D 2414 of 30 to 200 ml / 100 g 90 to 180 ml / 100g, more preferably 110 to 180 ml / 100g. A particularly suitable carbon black in the context of the present invention is, for example, a carbon black of the

ASTM type N339 with an iodine adsorption number of 90 g / kg and a DBP number of 120 ml / 100g. This is for use in vehicle tires, especially in

Tread. Silicas are known in the art as reinforcing fillers. According to a preferred embodiment of the invention, the rubber mixture contains 0.1 to 30 phr at least one silicic acid, preferably 5 to 30 phr of at least one silica. It can therefore also be a so-called partial silica mixture.

According to another preferred embodiment of the invention, the

Rubber mixture 5 to 250 phr, more preferably 20 to 200 phr, again preferably 20 to 100 phr of at least one silica.

The terms "silica" and silica "are used synonymously in the context of the present invention.

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 area (BET surface area) (according to DIN ISO 9277 and DIN 66132) of 35 to 350 m ² / g, preferably from 35 to 260 m ² / g, more preferably from 70 to 235 m ² / g and most preferably from 70 to 205 m ² / g, and a CTAB surface (according to ASTM D 3765) from 30 to 400 m ² / g, preferably from 30 to 255 m ² / g, particularly preferably from 65 to 230 m ² / g and very particularly preferably from 65 to 200 m ² / g.

Such silicas lead z. B. in rubber blends for inner tire components 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 silicic acids with a comparatively low BET surface area (such as, for example, Zeosil® 1115 or Zeosil® 1085 from Solvay) and highly dispersible silicas, so-called HD silicas (eg Zeosil ® 1165 MP from Solvay).

Other possibly reinforcing fillers are, for example, graphite and graphene and so-called "carbon-silica dual-phase filing." The rubber mixture according to the invention may contain, preferably very small amounts, ie preferably 0 to 3 phr, further non-reinforcing fillers non-reinforcing fillers are within the scope of the present invention

Aluminosilicates, kaolin, chalk, starch, magnesia, titania or rubber gels, and fibers (such as aramid fibers, glass fibers, carbon fibers, cellulose fibers). Zinc oxide does not belong to the fillers in the context of the present invention.

The optional silica may be in the form of tethered or not

tethered silica be included.

In the case where the silica is present in the form of bound silica, the rubber mixture preferably contains at least one silane coupling agent.

Silane coupling agents are also referred to in the context of the present invention as "silane".

Here, one or more different silane coupling agents can be used in combination with each other. The rubber mixture may thus contain a mixture of different silanes.

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). As silane coupling agents, all those skilled in the art for use in

Rubber blends known silane coupling agents can be used. Such known from the prior art coupling agents are bifunctional organosilanes having 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. For example, they may be the following chemical groups:

-SCN, -SH, -NH ₂ or -S _x - (where x = 2 to 8).

Thus, as silane coupling agents z. 3-mercaptopropyltriethoxysilane,

3-Thiocyanato-propyltrimethoxysilane or 3, 3 'bis (triethoxysilylpropyl) poly sulfides having 2 to 8 sulfur atoms, such as. B. 3,3'-bis (triethoxysilylpropyl) tetrasulfide (TESPT), the corresponding disulfide (TESPD) or mixtures of the sulfides with 1 to 8

Sulfur atoms with different contents of the different sulfides, are used. For example, TESPT can also be used as a mixture with carbon black

(Trade name X50S® 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 e.g. available under the trade name Si 266® Evonik, which is e.g. is described in DE 102006004062 AI. Also blocked mercaptosilanes, as z. B. from WO 99/09036 are known, can be used as a silane coupling agent. Silanes, as described in WO 2008/083241 Al, WO 2008/083242 Al, WO 2008/083243 Al and WO 2008/083244 Al, can also be used. Suitable for. For example, silanes sold under the name NXT (eg 3- (octanoylthio) -l-propyl-triethoxysilane) in various variants by Momentive, USA, or those sold under the name VP Si 363® by Evonik Industries become.

Furthermore, it is conceivable that one of the abovementioned mercaptosilanes, in particular

3-mercaptopropyltriethoxysilane, in combination with processing aids (which are listed below), in particular PEG carboxylic acid ester, can be used.

According to a preferred embodiment of the invention, the rubber mixture contains a combination of 3-mercaptopropyltriethoxysilane and PEG carboxylic acid ester, which gives particularly good properties, in particular with regard to the technical problem to be solved and overall a good level of properties in terms of other properties. Furthermore, the rubber mixture may contain further activators and / or agents for the binding of fillers, in particular carbon black. This can happen

For example, to the compound disclosed in EP 2589619 Al, for example, S- (3-aminopropyl) thiosulfuric acid and / or their metal salts, resulting in very good physical properties of the rubber mixture, especially when combined with at least one carbon black as a filler. According to a preferred embodiment, the rubber mixture according to the invention contains a maximum of 35 phr of at least one plasticizer, wherein the

Total amount of plasticizer (s), if at least one plasticizer is present, preferably 0.1 to 35 phr. This results in particular in combination with the above-mentioned components a particularly good processability of

Rubber mixture, in particular the extrudates before crosslinking, while good properties in view of the problem to be solved. With more than 35 phr of plasticizer (s), the heat buildup properties (hysteresis) are deteriorated. In addition, the conflict of objectives is made up of reinforcing properties

(Rigidity / hardness) and hysteresis deteriorated.

The plasticizer can also be completely or partly pass through the above-described masterbatch comprising CNT and polyisoprene into the rubber base mixture in the appropriate amounts.

The plasticizers used in the present invention include all known in the art plasticizers such as aromatic, naphthenic or

paraffinic mineral oil softening agents, such as e.g. 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) are preferred with a content of polycyclic Aromatics of less than 3 wt .-% according to method IP 346 or rapeseed oil or resin acids in particular or fact or liquid polymers whose average molecular weight (determined by GPC gel permeation chromatography, based on BS ISO 11344: 2004) between 500 and 20,000 g / mol is located. Be in the

According to the invention rubber mixture used additional liquid polymers as plasticizers, they do not go as a rubber in the calculation of the composition of the polymer matrix.

The plasticizer is preferably selected from the group consisting of the above-mentioned plasticizers. According to a particularly preferred embodiment of the invention contains the

Masterbatch already at least one plasticizer (see above), preferably in this case at least one resin acid, in particular disproportionated resin soap (eg.

SYLVAROS ™ DRS 215, Kraton or SYLVAROS ™ DRS 40, Kraton) or at least one mineral oil plasticizer.

According to another preferred embodiment of the invention, the

Rubber mixture additionally - added to any existing plasticizer in the masterbatch - at least one plasticizer. Mineral oils are particularly preferred as plasticizers.

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.

According to a preferred embodiment of the invention, 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 a good miscibility of the rubber mixture.

The plasticizer (s) which are not already contained in the masterbatch are preferably added in at least one basic mixing stage during the preparation of the rubber mixture according to the invention. Furthermore, the rubber mixture customary additives in conventional

Contain by weight, preferably in their preparation in at least one

Basic mixing stage to be added. 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 (eg., Stearic acid) and / or other activators, such as zinc complexes such as zinc ethylhexanoate,

c) waxes,

d) hydrocarbon resins which are not already included as plasticizers,

e) Mastikationshilfsmittel such. 2,2'-dibenzamidodiphenyl disulphide (DBD); and f) process aids such as, in particular, fatty acid esters and metal soaps, e.g.

Zinc soaps and / or calcium soaps.

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.

The total amount of other additives zinc oxide (ZnO) may be included in the above amounts.

These may be any type of zinc oxide known to those skilled in the art, such as ZnO granules or powder. The conventionally used zinc oxide usually has a BET surface area of less than 10 m ² / g. However, it is also possible to use a zinc oxide having a BET surface area of from 10 to 100 m ² / g, for example so-called "nano-zinc oxides".

The rubber mixture according to the invention is sulfur-crosslinked, which means that the vulcanization of the underlying crude mixture in the presence of sulfur and / or sulfur donors is carried out with the aid of vulcanization accelerators. Some vulcanization accelerators can also act as sulfur donors. In this case, the accelerator is preferably 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.

Preferably, the use of a sulfenamide Beschleumgers, which is selected from the group consisting of N-cyclohexyl-2-benzothiazolesufenamid (CBS) and / or N, N Dicyclohexylbenzothiazole-2-sulfenamide (DCBS) and / or benzothiazyl-2-sulfenmorpholide (MBS) and / or N-tert-butyl-2-benzothiazyl sulfenamide (TBBS).

As a sulfur-donating substance, all known in the art

Sulfur donating substances are used. If the rubber mixture contains a sulfur-donating substance, it is preferably selected from the group comprising e.g. Thiuram disulfides, e.g. Tetrabenzylthiuram disulfide (TBzTD) and / or

Tetramethylthiuram disulfide (TMTD) and / or tetraethylthiuram disulfide (TETD), and / or thiuramate tetrasulfides, e.g. Dipentamethylene thiuram tetrasulfide (DPTT), and / or dithiophosphates, e.g.

DipDis (bis (diisopropyl) thiophosphoryl disulfide) and / or bis (0,0-2-ethylhexyl thiophosphoryl) polysulfide (eg Rhenocure SDT 50®, Rheinchemie GmbH) and / or zinc dichloro dithiophosphate (eg Rhenocure ZDT / S®, Rheinchemie GmbH) and / or zinc alkyl dithiophosphate, and / or 1, 6-bis (N, N-dibenzylthiocarbamoyldithio) hexane and / or diaryl polysulfides and / or dialkyl polysulfides.

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 mixture. This system contains a vulcanizing agent, which with a

Functionality greater than four crosslinked and at least one vulcanization accelerator. The vulcanizing agent which has a functionality of greater than four crosslinked, for example, the general formula D):

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 independently selected from a rubber active group contains sulfur-containing functionalities; and wherein a, b and c are integers for which independently: a is 0 to 6; b is 0 to 8; and c is 3 to 5. 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 Natriumthiosulfonatgruppe (Bunte salt group).

This will be very good abrasion and tear properties of the invention

Rubber mixture achieved.

Particularly preferred is the use of the accelerators TBBS and / or CBS and / or diphenylguanidine (DPG).

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

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

Another object of the present invention is a vehicle tire, the at least one sulfur-crosslinked in at least one component according to the invention

Rubber mixture has. The vehicle tire according to the invention can in

different components have different embodiments of the rubber mixture according to the invention.

The at least one component is particularly preferably at least one tread and / or one side wall and / or one conductivity track.

A further subject of the present invention is a process for preparing a sulfur-crosslinked rubber mixture containing CNT comprising at least the following process steps: a) preparation of a masterbatch of at least one polyisoprene and CNT, the CNTs being intensively mixed into the polyisoprene; and

b) optionally providing further ingredients comprising at least one reinforcing filler and / or at least one sulfur crosslinkable rubber and / or antiaging agent and / or at least one silane coupling agent; and c) optionally mixing the further constituents from step b) with the polyisoprene CNT masterbatch; and

d) providing at least one sulfur vulcanization system;

e) mixing the mixture from step a) or c) with the

Sulfur vulcanization system from step d); and

f) vulcanization of the mixture from step e) to a sulfur-crosslinked

Rubber mixture.

For the constituents, all statements which have been made above for the rubber mixture according to the invention apply.

It is therefore essential to the invention that, according to step a), a masterbatch comprising at least one polyisoprene and CNT is prepared, which is subsequently optionally mixed with further constituents to form a rubber base mixture. Without steps b) and c), the masterbatch itself constitutes a rubber masterbatch to which, according to step e), a sulfur vulcanization system may also be added, thereby providing a final rubber compound.

The preparation of the polyisoprene NR masterbatch according to step a) is carried out by methods known to the person skilled in the art, as described above.

The ready mix is e.g. further processed by an extrusion process or calendering and brought into the appropriate form. Subsequently, the further processing by vulcanization according to step f), wherein due to the vulcanization system added in the context of the present invention, a sulfur crosslinking takes place.

For use in vehicle tires, the mixture is preferably pre-vulcanized in the form of a tread and / or sidewall and / or a conductivity track and deposited as known in the manufacture of the vehicle tire blank.

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

Mixtures here are mixtures according to the invention, while the mixtures marked with "V" are comparative mixtures The preparation of the mixture was carried out under customary conditions in three stages in a laboratory tangential mixer.

From all mixtures test specimens were prepared by vulcanization and determined with these specimens typical for the rubber industry material properties. For the above-described tests on specimens, the following test procedures were used:

Table 1 :

Mooney viscosity according to ASTM D1646; e.g. ML1 + 4 at 100 ° C (Mooney units M.E.

• Shore A hardness at room temperature by means of a durometer in accordance with DIN ISO 7619-1

• Rebound resilience at 70 ° C according to DIN 53 512 or ISO 4662 or ASTM D 1054

Tensile strength, elongation at break and stress values at 50% and 300% elongation at room temperature in accordance with DIN 53 504 (M50 and M300)

• Abrasion at room temperature according to DIN / ISO 4649

Dispersion by means of a dispergrader (microscope disperGRADER;

Enlargement)

FIG. 1:

• Specific electrical volume resistance according to DIN IEC 60093; Ohms mm (y-axis) are plotted against% by volume of> CNT based on the respective

Rubber compound (x-axis) Table 1

Component Unit VI El E2

NR (TSR) phr 60 47 35

BR phr 10 10 10

SSBR phr 30 30 30

Carbon black 43 31 20

NR-CNT-MB ^a) phr - 17.69 34.01

Silica phr 16 16 16

Silane ^b) phr 2.25 2.25 2.25

Other phr 17,1 17,1 17,1 17,1 Additives ^

Accelerator ^d) phr 1.7 1.7 1.7

Sulfur phr 1.5 1.5 1.5

Viscosity M.E. 74 60 60

Hardness RT Shore A 63 60 60

Rückpr. 70 ° C% 60 61 61

Tensile strength MPa 22 22 21

M50 MPa 1.4 1.3 1.3

M300 MPa 12 11 10

Breaking strain% 522 560 570

Dispersion% 88 93 87

Abrasion mm ³ 114 105 105

Substances used Table 1:

a) NR-CNT masterbatch: CNT predispersed in NR: 67.3 wt% NR, 18.7 wt% CNT, 14 wt% resin acids; Density 1.03 g / cm ³ b) Silane: TESPD + 3-mercaptopropyltriethoxysilane c) Other additives: Process auxiliaries: PEG carboxylic acid ester;

Hydrocarbon resin; Anti-aging agents; Antiozonant wax, zinc oxide;

Stearic acid d) accelerator: DPG + CBS

As Table 1 shows, the rubber mixtures of the invention El and E2 have an improved abrasion behavior. The other properties are on one

comparable level or even improved.

Furthermore, the electrical conductivity or the electrical resistance of various comparative mixtures and mixtures according to the invention was investigated. The result is summarized in FIG.

The mixture series are composed as follows (explanation for FIG. 1): Comparative Example C2

ESBR1500_CNT_1: ESBR as the sole rubber matrix, partly from an ESBR-CNT masterbatch and partially added separately:

One data point with 5% by volume CNT in the rubber mixture; For this purpose, 67.8 phr of a masterbatch containing 16.1% by weight of CNT and 82.9% by weight of ESBR and the remainder of plasticizer were mixed with 43.8 phr of ESBR. Other ingredients: 3 phr zinc oxide, 2 phr stearic acid, 1.5 phr sulfur, 1.3 phr accelerator TBBS. Inventive Examples E3, E4, E5

NR_CNT_1: NR as sole rubber matrix, partly from an NR-CNT masterbatch and partially added separately:

3 data points with 4.5 and 6.5 and 7.6 vol.% CNT in the rubber mixture:

E3: 4.5% by volume CNT: 60 phr of an NR-CNT masterbatch containing 82.8% by weight of NR and 17% by weight of CNT and the remainder of plasticizer and 50.32 phr of NR.

E4: 6.5 vol% CNT: 90 phr of the NR-CNT masterbatch (as described under 4.5 vol% CNT) and 25.48 phr NR.

E5: 7.6 vol% CNT: 120.77 phr of the same NR-CNT masterbatch and no additional NR, i. 0 phr separate NR.

The mixtures also contained the same further constituents as under

ESBR1500 CNT 1 listed.

Inventive Examples E6, E7, E8, E9, E10

50 NR / 50 ESBR (NR CNT MB): The rubber matrix consists of 50% by weight of ESBR and 50% by weight of NR; the CNTs are predispersed exclusively in the NR (NR-CNT masterbatch):

5 data points with 1.5 and 2 and 3 and 4 and 4.7% by volume CNT in the rubber mixture: E6: 1.5% by volume CNT: 18.59 phr of the NR-CNT masterbatch (as under 4, 5% by volume CNT) and 34.61 phr of NR and 50 phr of ESBR;

E7: 2% by volume CNT: 24.91 phr of the same NR-CNT masterbatch and 29.37 phr of NR and 50 phr of ESBR;

E8: 3% by volume CNT: 37.75 phr of the same NR-CNT masterbatch and 18.74 phr of NR and 50 phr of ESBR;

E9: 4% by volume CNT: 50.86 phr of the same NR-CNT masterbatch and 7.89 phr of NR and 50 phr of ESBR;

E10: 4.7% by volume CNT: 60.39 phr of the same NR-CNT masterbatch and no additional NR, i. 0 phr NR and 50 phr ESBR;

The mixtures also contained the same further constituents as under

ESBR1500 CNT 1 listed. Comparative Examples V3, V4, V5 and V6

50 NR / 50 ESBR (ESBR CNT MB): The rubber matrix consists of 50% by weight ESBR and 50% by weight NR; the CNT are predispersed exclusively in the ESBR (ESBR-CNT masterbatch):

4 data points with 2 and 3 and 4 and 4.5% by volume CNT:

V3: 2% by volume CNT: 26.55 phr of the ESBR-CNT masterbatch (as described under

ESBR1500 CNT 1 described) and 27.99 phr ESBR and 50 phr NR;

V4: 3% by volume CNT: 40.26 phr of ESBR-CNT masterbatch (as under

ESBR1500 CNT 1) and 16.63 phr ESBR and 50 phr NR;

V5: 4% by volume CNT: 54.22 phr of the ESBR-CNT masterbatch (as under

ESBR1500 CNT 1 described) and 5.05 phr of ESBR and 50 phr of NR;

V6: 4.5% by volume CNT: 60.31 phr of ESBR-CNT masterbatch (as under

ESBR1500 CNT 1) and no additional ESBR, i. 0 phr ESBR and 50 phr NR;

The mixtures also contained the same further constituents as under

ESBR1500 CNT 1 listed.

Comparative Examples V7, V8, V9 and V10

50 NR / 50 ESBR (1/2 NR CNT MB, 1/2 ESBR CNT_MB): The rubber matrix consists of 50% by weight of ESBR and 50% by weight of NR; the CNT are both in

ESBR predispersed (ESBR-CNT-MB) as well as in the NR (NR-CNT masterbatch):

V7: 1.5% by volume CNT: 9.29 phr of the NR-CNT masterbatch (as described under 4.5% by volume of CNT) and 42.3 phr of NR and 9.91 phr of the ESBR-CNT masterbatch ( as under

ESBR1500 CNT 1 described) and 41.79 phr ESBR;

V8: 2% by volume CNT: 12.46 phr of the NR-CNT masterbatch (as described under 4.5% by volume of CNT) and 39.69 phr of NR and 13.27 phr of the ESBR-CNT masterbatch (as described in US Pat

ESBR1500 CNT 1 described) and 39 phr ESBR;

V9: 5% by volume CNT: 32.12 phr of the NR-CNT masterbatch (as described under 4.5% by volume of CNT) and 23.4 phr of NR and 34.24 phr of the ESBR-CNT masterbatch (as described in US Pat ESBR1500 CNT 1 described) and 21.61 phr ESBR; V10: 8.7% by volume CNT: 60.39 phr of the NR-CNT masterbatch (as described under 4.5% by volume of CNT) and no additional ie 0 phr NR and 60.31 phr of the ESBR-CNT Masterbatches (as described under ESBR1500 CNT 1) and no additional ie 0 phr ESBR;

The mixtures also contained the same further constituents as under

ESBR1500 CNT 1 listed.

As can be seen in FIG. 1 (in conjunction with the above explanations), surprisingly, the rubber mixtures according to the invention (E3, E4, E5 and E6, E7, E8, E9, E10) in which the CNT is present exclusively in at least one

Polyisoprene, here NR, are predispersed, achieved a significantly lower electrical resistance and thus a significantly improved electrical conductivity.

Claims

claims

1. Sulfur crosslinked rubber compound for vehicle tires

containing carbon nanotubes (CNT), characterized in that the CNTs are predispersed in at least one polyisoprene.

2. rubber mixture according to claim 1, characterized in that the

at least one polyisoprene is at least one natural polyisoprene.

3. Rubber mixture according to one of the preceding claims, characterized

characterized in that it contains the CNT in an amount of 0.1 to 25 phr.

4. Rubber mixture according to one of the preceding claims, characterized

in that, in addition to the polyisoprene in which the CNTs are predispersed, it contains at least one further sulfur-crosslinkable rubber.

5. Rubber mixture according to one of the preceding claims, characterized

in that it contains at least one further reinforcing filler and the ratio of further reinforcing fillers to CNT 100 is 1 to 2 to 1.

6. Rubber mixture according to one of the preceding claims, characterized

characterized in that it contains a maximum of 35 phr of plasticizers.

7. A vehicle tire, characterized in that it comprises in at least one component at least one sulfur-crosslinked rubber mixture according to one of claims 1 to 6. Vehicle tire according to claim 7, characterized in that it is

Component around a tread and / or a side wall and / or a

Conductivity railway acts.

Process for the preparation of a sulfur-crosslinked rubber mixture

Vehicle tire containing CNT comprising at least the following

Process steps: a) Preparation of a masterbatch of at least one polyisoprene and CNT, the CNTs being intensively mixed into the polyisoprene; and b) optionally providing further ingredients comprising at least one reinforcing filler and / or at least one sulfur crosslinkable rubber and / or antiaging agent and / or at least one silane coupling agent; and

c) optionally mixing the further constituents from step b) with the polyisoprene-CNT masterbatch; and

d) providing at least one sulfur vulcanization system; e) mixing the mixture from step a) or c) with the

Sulfur vulcanization system from step d); and

f) vulcanization of the mixture from step e) to a sulfur-crosslinked rubber mixture.

10. The method according to claim 9, characterized in that the CNT in the in

Step a) masterbatch contained in an amount of 0.1 to 20 wt .-% based on the total amount of the masterbatch.