Rubber composition for an inner liner for pneumatic vehicle tyres

Abstract

The invention relates to a rubber composition, comprising a rubber component that has at least one halobutyl rubber in an amount of 60 to 100 phr, and a filler component that comprises fillers F1 having a 14 C content in the range from 0.20 to 0.45 Bq / g carbon; a carbon content in the range from 60% by weight to 85% by weight; and at their surfaces acidic hydroxy groups; wherein the weighted arithmetic mean of the STSA surface areas of the fillers F1 lies in the range from 40 m2 / g to 80 m2 / g; the fillers F1 have a volume-based median grain-size distribution Dv(50) in the range from 0.5 µm to 5 µm and a volume-based Dv(97) value in the range from 3 µm to 23 µm; and (i) the filler component contains more than 45 phr of fillers F1; or (ii) the filler component contains more than 25 phr of fillers F1 and additionally one or more carbon blacks F2, wherein the weighted arithmetic mean of the STSA surface areas of the carbon blacks F2 lies in the range from 55 m2 / g to 95 m2 / g. The invention also relates to a vulcanizable and a vulcanized rubber composition based on the aforementioned rubber composition, to a kit-of-parts for producing the vulcanizable rubber composition and to a method for producing the rubber composition and the vulcanizable rubber composition. The invention further relates to a method for further processing the vulcanizable rubber composition. The invention additionally relates to the use of the aforementioned hydrothermally treated lignin for the production of rubber compositions for inner liners.

Description

[0001] RUBBER COMPOSITION FOR AN INNERLINER FOR PNEUMATIC VEHICLE TIRES

[0002] FIELD OF THE INVENTION

[0003] The invention relates to rubber compositions, in particular vulcanizable and vulcanized rubber compositions for inner liners of pneumatic vehicle tires. Furthermore, the invention relates to a kit of parts for their production and methods for their production and further processing, as well as a method for producing pneumatic tires. Furthermore, the invention relates to the use of special fillers from renewable raw materials for the production of the rubber compositions, in particular for inner liners.

[0004] BACKGROUND OF THE INVENTION

[0005] Pneumatic vehicle tires have a complex design. The requirements they meet are correspondingly diverse. On the one hand, they must ensure short braking distances on both dry and wet roads, while on the other, they must possess good abrasion properties and low rolling resistance. Furthermore, the vehicle tires must comply with legal requirements.

[0006] To ensure the diverse performance profile, the individual tire components are specialized and consist of a variety of different materials, such as metals, polymer textiles and various rubber-based components.

[0007] Depending on the design of the pneumatic tire, a distinction is made between radial tires, cross-ply tires, and bias-belted tires. A typical pneumatic tire, using the example of a radial belted tire, comprises at least a belt, a belt cover, a tread, reinforcement strips, sidewalls, apex, bead cords, an inner liner, and a carcass. The belt usually consists of twisted steel wire layers that are rubberized and arranged at an angle. It essentially serves to provide structural strength to the tire when inflated. The belt also ensures driving stability during acceleration, braking, and cornering. It influences rolling resistance and plays a significant role in the tire's mileage.

[0008] The belt cover located between the tread and the upper belt serves to improve high-speed stability and limits the tire diameter as speed increases.

[0009] The tread is crucial for a tire's driving characteristics. The rubber compound of the tread determines the abrasion behavior and dynamic handling in different weather conditions (on wet and dry roads, in cold and warm weather, on ice and snow). The tread pattern, in turn, is largely responsible for the tire's aquaplaning performance, wet performance, and on snow, and also determines its noise level.

[0010] Reinforcement strips are optionally used in the area of ​​the apex to further improve the strength of the tire and its driving characteristics.

[0011] The sidewall protects the carcass from lateral damage and weather influences. The rubber compound for the sidewall is flexible and abrasion-resistant and contains relatively high amounts of additives to protect against aging and ozone.

[0012] The apex sits above the bead cable / bead core. Its shape and design ensure driving stability and influence steering precision and suspension comfort. Rubber compounds for apex are typically very strong and relatively hard, which is ensured, among other things, by a high degree of crosslinking using high-dose vulcanization systems and by the choice of fillers.

[0013] The bead cord is the inner part of the tire bead and consists of twisted, rubber-coated steel wires wound in a ring shape to hold the tire securely on the rim. The tire bead (also called the tire base) presses against the rim flange and seals the tire, creating an airtight seal in the usual tubeless design. The steel wires and cables in the tire, in the bead core, the belt, or even the carcass of a solid steel tire, must bond firmly to the surrounding rubber compound so that they function as a single composite. For this purpose, the steel wires are often coated with brass or bronze. Only then are they formed into components with a wire bonding compound, which in turn are assembled to form a green tire. Wire bonding compounds are relatively strong, crack-resistant due to their high natural rubber content, and achieve a strong bond to the brass or bronze coating, for example, through special resin additives and a high sulfur content.The permanent bond is formed during vulcanization.

[0014] The carcass forms the basic structure of the tire and consists of one or more textile fabric layers (rayon, nylon, polyester, aramid) or steel cord layers (in trucks) embedded in rubber. The carcass is tensioned by the tire's air pressure and is therefore essentially responsible for transmitting power between the rim and the tread / road. In the tire base, it is connected to the tire bead and thus holds the tire together. The carcass acts as a bond between the cord layers, which ensure strength and power transmission, and a rubber compound that encloses the parallel cords. Due to the constant deformation of the tire, the cord compound must therefore be fatigue-resistant. This is usually achieved through a blend of natural and synthetic rubber, but at the same time it must also bond firmly to the cords. For this purpose, the cords are coated with a rubber compound after twisting.The thus-treated cords are coated with the unvulcanized rubber compound. Resin systems in the special compounds then react with the cord finish during vulcanization to form a permanent bond.

[0015] Modern tires, as described above, are generally tubeless. The so-called inner liner is a largely air-impermeable, radially inward-facing layer of a rubber compound. It is also called the inner core or inner plate and serves to ensure that the air pumped into the tire does not escape over an extended period of time, as air pressure significantly influences the tire's handling characteristics and durability. Furthermore, the internal pressure influences the tire's rolling resistance. A decrease in air pressure leads to greater dynamic deformation of the tire, which in turn causes some of the kinetic energy to be undesirably converted into heat energy. This has a negative impact on the vehicle's fuel consumption and thus also on the associated carbon dioxide emissions.

[0016] Furthermore, the inner liner protects the carcass from air and moisture penetration, thus preventing damage to the reinforcements of the carcass and / or the belt. To ensure the inner liner remains largely airtight, it should also exhibit good crack and fatigue resistance to prevent cracks from occurring during ferry service, which could compromise airtightness.

[0017] Due to this specific requirement profile, rubber compounds for inner liners have completely different compositions than the rubber compounds of other tire components, both in terms of the rubbers used, the fillers used, and the weight ratios of the components to each other. However, they must still be compatible with the adjacent tire components, and in particular, exhibit good adhesion to them. In addition to the type of rubber, minimum quantities for various rubbers in the rubber compound also play a role, as do various specific parameters and properties of the fillers used. Halobutyl rubbers such as chlorobutyl rubber and bromobutyl rubber, occasionally blended with other rubbers, are used as rubbers for the inner liner. Butyl and halobutyl rubbers exhibit low gas permeability.Halobutyl rubbers are blended with other rubbers, such as natural rubber, to increase the adhesive strength, reduce costs and adjust the mechanical properties.

[0018] By adding voluminous, low- or inactive fillers to the rubber compound of the inner liners, their airtightness can be further increased. The fillers used to date include, in particular, furnace black.

[0019] To prevent cracking under dynamic loads, inner liners must have a balanced elastic modulus and appropriate hardness, which, however, is usually at odds with a high proportion of inactive fillers. Therefore, mineral oil plasticizers are often added to the rubber composition. These reduce the elastic modulus and hardness of the composition while simultaneously increasing gas permeability, resulting in a relatively narrow, optimal range for the amounts of mineral oil plasticizer and filler used.

[0020] In addition, many fillers such as carbon black of type N 660 have relatively high densities of about 1.8 g / cm 3or higher. Accordingly, rubber compositions compounded with such fillers also have a higher density and thus a higher weight for the same volume. However, the higher density of the filler also results in a higher weight of the inner liner and ultimately of the pneumatic tire, which in turn results in higher fuel consumption. Carbon blacks of types N 660 and N 772 are used in particular for inner liner production. Carbon blacks are usually produced petrochemically through incomplete combustion or pyrolysis of hydrocarbons. From an environmental perspective, however, the use of fossil fuels for the production of fillers should be avoided or reduced to a minimum. Instead, the aim should be to provide biomass-based fillers for compounding that meet the diverse requirements of inner liners.

[0021] In the field of producing rubber compositions, inter alia for use in tires in general, WO 2017 / 085278 A1 discloses the use of so-called HTT lignin, a lignin converted by hydrothermal treatment, as a replacement filler for carbon black.

[0022] Lignins are solid biopolymers that are incorporated into plant cell walls, causing the lignification of plant cells. They are therefore present in biorenewable raw materials and, particularly in hydrothermally treated form, have potential as an environmentally friendly alternative to carbon black in rubber compositions.

[0023] WO 2017 / 194346 A1 describes the use of HTT lignins in rubber compounds for pneumatic tire components, particularly together with a methylene donor compound such as hexa(methoxymethyl)melamine, to increase the stiffness of a cured rubber component of a pneumatic tire, and, among other things, to replace phenolic resins and / or in combination with silane-based coupling agents. One of the objectives addressed in WO 2017 / 194346 is to reduce the rolling resistance of tires. Suitable rubber materials include natural rubber, polybutadiene rubber, styrene-butadiene rubber, and polyisoprene rubber. WO 2017 / 194346 A1 discloses the suitability of the rubber compounds described therein for the tread areas of a pneumatic tire, the sidewalls, and the tire bead. A rubber compound that meets the requirements of an inner liner is not described in this document.

[0024] EP 3 470 457 A1 also discloses vulcanizable sulfur-containing rubber compounds for vehicle tires. HTT carbons obtained from various starting materials, including those produced with the addition of metal halides, were used as fillers for the tested solvent-polymerized styrene-butadiene rubbers (SSBR). These carbons had BET surface areas of up to over 180 m². 2 / g. Among these, HTT coals with a BET surface area of ​​90 to 140 m 2 / g, which are said to have increased surface roughness and optimized surface functionality.

[0025] WO 2020 / 202125 A1 teaches for the first time in the field of inner liner production the use of a halobutyl rubber in combination with up to 45 phr (parts per hundred parts of rubber by weight) of an HTT lignin. However, in the examples of WO 2020 / 202125 A1, this is never used as the sole filler, but exclusively in combination with a carbon black of type N 660. In particular, the aforementioned publication teaches that the admixed carbon blacks have a specific surface area between 30 and 50 m 2 / g, which is a characteristic of carbon black type N 600, which has a BET surface area of ​​35 m 2 / g (ASTM D 6556) and an STSA surface area of ​​34 m 2 / g (ASTM D 6556). Both the limitation of the HTT lignin content to a maximum of 45 phr, as well as the limitation of the admixture of carbon blacks to those with a maximum specific surface area of ​​50 m 2 / g, however, has surprisingly proven to be disadvantageous with regard to the gas permeability to be reduced as well as the crack growth to be kept low, although the latter are those that are typically used in inner liners.

[0026] In summary of the state of the art, there is therefore a particular need for rubber compositions or rubber mixtures that are suitable for inner liners of pneumatic tires, contain environmentally friendly carbon black substitute materials based on renewable raw materials as fillers, and provide vulcanized rubber compositions that meet the requirements for inner liners of pneumatic tires, in particular with regard to airtightness and crack resistance, and have improved tear resistance.

[0027] SUMMARY OF THE INVENTION

[0028] The problems underlying the invention could be solved by providing a rubber composition comprising a rubber component which comprises at least one halobutyl rubber selected from the group consisting of bromobutyl rubber and chlorobutyl rubber, and a filler component which comprises one or more fillers F1 which have a 14 C content in the range of 0.20 to 0.45 Bq / g carbon; have a carbon content in the range of 60 wt% to 85 wt% based on the ash-free and water-free filler; have acidic hydroxy groups on their surfaces; the weighted arithmetic mean of the STSA surface areas of the fillers F1 in the range of 40 m 2 / g up to 80 m 2 / g; the fillers F1 have a volume-based median of the grain size distribution D v (50) in the range of 0.5 pm to 5 pm and a volume-based D v(97)- value in the range of 3 pm to 23 pm; and i. the filler component contains more than 45 phr of fillers F1; or ii. the filler component contains more than 25 phr of fillers F1 and additionally contains one or more carbon blacks F2, wherein the weighted arithmetic mean of the STSA surface areas of the carbon blacks F2 is in the range of 55 m 2 / g up to 95 m 2 / g; wherein the proportion of halobutyl rubber in the rubber composition is 60 to 100 phr.

[0029] The term phr (parts per hundred parts of rubber by weight) used herein is the standard quantity used in the rubber industry for compound formulations. The dosage of the parts by weight of the individual components is always based on 100 parts by weight of the total mass of all rubbers present in the compound.

[0030] This rubber composition is hereinafter also referred to as the rubber composition of the invention or the rubber composition according to the present invention.

[0031] Furthermore, the invention relates to a vulcanizable rubber composition which comprises or consists of a rubber composition according to the invention and a vulcanization system containing zinc oxide and / or sulfur.

[0032] This vulcanizable rubber composition is hereinafter also referred to as the vulcanizable rubber composition of the invention or the vulcanizable rubber composition according to the present invention.

[0033] The invention further relates to a kit of parts comprising, in spatially separated form, a rubber composition according to the invention and a vulcanization system containing zinc oxide and / or sulfur.

[0034] This kit of parts is also referred to below as the inventive kit of parts or kit of parts according to the present invention. The present invention also provides a process for producing a rubber composition according to the invention and a vulcanizable rubber composition according to the invention, the latter being obtained by, in a first step, preparing the rubber composition according to the invention as a masterbatch, compounding the components of the rubber composition, and, in a second step, admixing the components of the vulcanization system.

[0035] These processes are also referred to as processes according to the invention for producing the rubber composition according to the invention or the vulcanizable rubber composition according to the invention.

[0036] The invention further relates to a process for further processing the vulcanizable rubber compositions according to the invention in which they are formed into a web by calendering, extrusion or in the so-called roller-head process.

[0037] This method is also referred to as further processing method according to the invention or further processing method according to the present invention.

[0038] The invention also relates to a process for producing a pneumatic tire, comprising the further processing process according to the invention, followed by a step of cutting the web obtained to form an inner liner of pneumatic tires and comprising the subsequent step of vulcanizing the inner liner thus obtained, preferably together with the carcass of a pneumatic tire.

[0039] This process is also referred to as a process according to the invention for producing a pneumatic tire or as a process for producing a pneumatic tire according to the present invention. The present invention also provides for the use of the fillers F1 suitable within the scope of the invention as characterized above, as well as filler mixtures comprising F1 and F2, in rubber compositions for inner liners, wherein the fillers F1 and F2 are used in a total amount of at least 46 phr.

[0040] This use is also referred to as use according to the invention or use according to the present invention.

[0041] DETAILED DESCRIPTION OF THE INVENTION

[0042] In the following, the components of the rubber compositions used in the above-mentioned rubber compositions, processes and the above-mentioned use according to the invention as well as particularly suitable process procedures are described in detail.

[0043] Rubber composition

[0044] Rubbers

[0045] In the context of the present invention, one or more halobutyl rubbers selected from the group consisting of chlorobutyl rubbers (CI IR; chloro-isobutene-isoprene rubber) and bromobutyl rubbers (BIIR; bromo-isobutene-isoprene rubber) are used.

[0046] Halobutyl rubbers are halogenated isobutene-isoprene rubbers. They are obtainable by halogenation, particularly bromination and / or chlorination, of butyl rubbers. Butyl rubbers, in turn, are composed predominantly of isobutene units and the remainder of isoprene units. The proportion of isobutene units is particularly preferably 95 to 99.5 mol% and the proportion of isoprene units is 0.5 to 5 mol%; very particularly preferably, the proportion of isobutene units is 97 to 99.2 mol% and the proportion of isoprene units is 0.8 to 3 mol%, with the proportion of isobutene units and isoprene units preferably adding up to 100 mol% of the monomers present as polymerized units in the polymer. Butyl rubbers generally have low gas and moisture permeability.

[0047] Due to the polymerized isoprene units, butyl rubbers have carbon-carbon double bonds, which are used both for vulcanization and for modification with halogens such as chlorine and bromine.

[0048] The halobutyl rubbers obtainable by modification with halogens (halogenation) have a higher reactivity than butyl rubbers and therefore a broader spectrum in terms of vulcanization possibilities, in particular the co-vulcanization possibilities with other rubbers such as natural rubber (NR), butyl rubber (HR) and styrene-butadiene rubber (SBR).

[0049] Among the halobutyl rubbers, bromobutyl rubbers are more reactive than chlorobutyl rubbers, which have a carbon-chlorine bond, due to their weaker carbon-bromine bond. This opens up an even broader range of vulcanization systems for bromobutyl rubbers. Bromobutyl rubbers vulcanize more quickly and typically exhibit better adhesion to diene rubbers.

[0050] Bromobutyl rubbers are particularly preferred among halobutyl rubbers in the context of the present invention. However, it is also possible to use mixtures of one or more bromobutyl rubbers with one or more chlorobutyl rubbers as the halobutyl rubber component. In this case, the bromobutyl rubbers increase the vulcanization rate.

[0051] Chlorobutyl rubbers (CIIR) suitable for the present invention preferably contain between 1.1 and 1.3 wt.% chlorine, while bromobutyl rubbers (BIIR) preferably contain between 1.9 and 2.1 wt.% bromine. This corresponds to a reactive site content of approximately 2 mol.%.

[0052] The viscosities of halobutyl rubbers are preferably between 35 and 55 Mooney units (ML (1 + 8), 125°C). Like butyl rubber, the products contain virtually no secondary components (rubber content > 98.5%). Halobutyl rubbers preferably contain stabilizers, particularly sterically hindered phenols.

[0053] The rubber composition according to the invention may contain, in addition to the halobutyl rubbers, one or more other rubbers different from the halobutyl rubbers.

[0054] Other rubbers other than halobutyl rubbers are, where available, particularly preferred natural rubber, butyl rubber and styrene-butadiene rubber.

[0055] For example, by blending natural rubber with halobutyl rubbers, the adhesion to other rubber-based tire components can be increased, especially compared to general-purpose rubbers. Crosslinking the various rubbers can also create synergies in terms of tensile strength, so that these can even exceed the tensile strength of the individual rubbers. This is especially true when using vulcanization systems comprising zinc oxide, sulfur, and a thiazole such as mercaptobenzothiazyl disulfide (MBTS). On the other hand, the addition of natural rubber typically increases the gas and moisture permeability of the vulcanized final product.

[0056] Styrene-butadiene rubbers can be blended into halobutyl rubbers in the same way as natural rubbers, but they typically offer no particular advantages over natural rubbers. Therefore, the use of natural rubbers is generally preferable to styrene-butadiene rubbers, especially considering the use of renewable raw materials. Typical natural rubbers are available under the names SMR ("Standard Malaysian Rubber"), TSR ("Technically Specified Rubber"), and RSS ("Ribbed Smoked Sheets").

[0057] The addition of up to 30 phr, preferably up to a maximum of 20 phr, of butyl rubber to halobutyl rubber typically has little to no effect on the gas and moisture permeability of the vulcanized final product, but can, where desired, reduce the vulcanization rate and increase heat resistance.

[0058] The total amount of halobutyl rubber is 60 to 100 phr, preferably 65 to 100 phr, more preferably 70 to 100 phr, further preferably 75 or 80 to 100 phr, most preferably 85 or 90 to 100 phr, such as 95 to 100 phr and most preferably 100 phr.

[0059] In the event that the rubber mixture contains less than 100 phr of halobutyl rubber, at least one further rubber is contained in the rubber composition, preferably one of the aforementioned rubbers, very particularly preferably natural rubber, so that the total amount of rubber contained is 100 phr.

[0060] This means that the amount of other rubbers other than the halobutyl rubbers is 0 to 40 phr, preferably 0 to 35 phr, particularly preferably 0 to 30 phr, further preferably 0 to 20 or 25 phr, most preferably 0 to 10 or 15 phr, for example 0 to 5 phr or 0 phr.

[0061] Fillers F1

[0062] In the filler component, one or more fillers F1 are mandatory, which have a 14 C content in the range of 0.20 to 0.45 Bq / g carbon, preferably 0.23 to 0.42 Bq / g carbon; a carbon content in the range of 60 wt.% to 85 wt.%, preferably 63 wt.% to 80 wt.% and particularly preferably 65 wt.% to 75 wt.% and most preferably 68 wt.% to 73 wt.%, based on the ash-free and water-free filler; the weighted arithmetic mean of the STSA surface areas of the fillers F1 in the range of 40 m 2 / g up to 80 m 2 / g, preferably 42 m 2 / g up to 75 m 2 / g, particularly preferably 44 m 2 / g up to 70 m 2 / g; and the filler(s) F1 have a volume-based median particle size distribution D v(50) from 0.5 to 5 pm, particularly preferably 1 to 4 pm and most preferably from 1 to 3 pm and have a volume-based D v (97) value of in the range from 3 pm to 23 pm, preferably up to a maximum of 18 pm, particularly preferably up to a maximum of 15 pm, very particularly preferably up to a maximum of 12 pm, even more preferably up to a maximum of 10 pm, even more preferably up to a maximum of 9 pm, even more preferably up to a maximum of 8 pm, most preferably up to a maximum of 7 pm, very particularly preferably up to a maximum of 6 pm; and the filler(s) F1 have acidic hydroxyl groups on their surfaces.

[0063] The above-mentioned required 14The C content is met by fillers F1 obtained from biomass by further treatment or conversion, preferably decomposition thereof, wherein the decomposition can be thermally, chemically and / or biologically, preferably thermally and chemically. Fillers obtained from fossil materials, such as fossil fuels in particular, therefore do not fall under the definition of the filler to be used according to the present invention, since they do not have a corresponding 14 C content.

[0064] Biomass is defined herein as any biomass, whereby the term “biomass” includes so-called phytomass, i.e. biomass originating from plants, zoomass, i.e. biomass originating from animals, and microbial biomass, i.e. biomass originating from microorganisms including fungi, whether the biomass is dry biomass or fresh biomass and whether it originates from dead or living organisms.

[0065] The biomass particularly preferred for the production of fillers F1 herein is phytomass, preferably dead phytomass. Dead phytomass includes, among other things, dead, shed, or severed plants and components. These include, for example, broken and torn leaves, side shoots, twigs and branches, fallen foliage, felled or trimmed trees, as well as seeds and fruits and components derived therefrom, as well as sawdust, wood shavings, and other products derived from wood processing.

[0066] The carbon content indicated above is usually met by fillers based on the decomposition of biomass and can be determined by elemental analysis according to DIN 51732: 2014-7.

[0067] The fillers F1 preferably have an oxygen content in the range of 15 wt.% to 30 wt.%, preferably 17 wt.% to 28 wt.%, and particularly preferably 20 wt.% to 25 wt.%, based on the ash-free and water-free filler. The oxygen content is defined herein as the difference to the carbon, hydrogen, nitrogen, and sulfur content.

[0068] In addition, the fillers F1 of the type defined above have acidic hydroxyl groups on their surface (so-called surface-available acidic hydroxyl groups). The surface-available acidic hydroxyl groups can be determined qualitatively and quantitatively colorimetrically according to Sipponen. The Sipponen method is based on the adsorption of the basic dye Azure B onto the acidic hydroxyl groups accessible on the filler surface. If such adsorption occurs under the conditions specified in section 2.9 (p. 82) of the article mentioned below, acidic, surface-available hydroxyl groups are present within the meaning of the present invention. Relevant details can be found in the article "Determination of surface-accessible acidic hydroxyls and surface area of ​​lignin by cation dye adsorption" (Bioresource Technology 169 (2014) 80-87).In a quantitative determination, the amount of surface-available acidic hydroxy groups is expressed in mmol / g of filler. Preferably, the amount of surface-available acidic hydroxy groups is in the range of 0.05 mmol / g to 40 mmol / g, more preferably 0.1 mmol / g to 30 mmol / g, and most preferably 0.15 to 30 mmol / g. Preferred surface-available acidic hydroxy groups are phenolic hydroxy groups.

[0069] Significant differences between the biomass-based fillers also exist in their BET surface areas (specific total surface area according to Brunauer, Emmett and Teller) and the external surfaces (STSA surface; Statistical Thickness Surface Area).

[0070] For example, WO 2017 / 085278 A1 describes STSA surfaces in the range of 5 to 200 m for hydrothermally treated lignins, i.e. fillers based on dead, lignin-containing phytomass obtained by hydrothermal treatment.2 / g. In the experimental part of the publication, even those with an STSA surface area of ​​only 2.6 m 2 / g called.

[0071] Within the scope of the invention, particular reference is also made to the weighted arithmetic mean of the STSA surface areas of the fillers. The term “weighted arithmetic mean” is used in the context of the present invention in its usual meaning. In connection with the STSA surface area in relation to the filler F1, when only one filler F1 is used, the weighted arithmetic mean of the STSA surface area of ​​this filler corresponds exactly to the STSA surface area of ​​this filler F1, since its relative frequency is 1 (weighted arithmetic mean of the STSA surface area = [STSA surface area of ​​F1] x 1). When using a mixture of, for example, two different fillers FT and F1", in which, for example, 70 wt. % filler FT (corresponds to a relative frequency of 0.7) and 30 wt.-% filler F1" (corresponds to a relative frequency of 0.3), the weighted arithmetic mean of the STSA surfaces of the fillers F1 = ([STSA surface of FT] x 0.7) + ([STSA surface of F1"] x 0.3) or in general: weighted arithmetic mean of the STSA surfaces of the fillers F1 = £ (STSA FÜ X hi), where STSA FÜ stands for the STSA surface of the filler FT and hi for the relative frequency of this filler.

[0072] Preferably, the STSA surfaces of each individual filler F1 are in the range of 40 to 80 m 2 / g, particularly preferably in the range of 40 to 75 m 2 / g, most preferably in the range of 42 to 70 m 2 / g. The selection of the individual fillers F1 is, of course, subject to the mandatory requirement that the weighted arithmetic mean of the STSA surfaces of the fillers F1 is in the range of 40 m 2 / g up to 80 m 2 / g, preferably 42 m 2 / g up to 75 m2 / g, particularly preferably 44 m 2 / g up to 70 m 2 / g.

[0073] The fillers F1 have a volume-based median grain size distribution D v (50) of minimum 0.5 pm and maximum 5 pm and a volume-based D v (97)- Value of the grain size distribution of minimum 3 pm and maximum 23 pm. The volume-based median of the grain size distribution D v (50) is in the range of 0.5 to 5 pm, particularly preferably in the range of 1 to 4 pm and most preferably in the range of 1 to 3 pm. The volume-based D v(97) value of the particle size distribution is in the range from 3 pm to 23 pm, preferably up to a maximum of 18 pm, particularly preferably up to a maximum of 15 pm, very particularly preferably up to a maximum of 12 pm, even more preferably up to a maximum of 10 pm, even more preferably up to a maximum of 9 pm, even more preferably up to a maximum of 8 pm, most preferably up to a maximum of 7 pm, very particularly preferably up to a maximum of 6 pm. The particle size distribution and the D v (50)- or D v (97) values ​​are determined by laser diffraction as described in detail in the experimental section. The D v (97) value of a filler F1 is naturally always greater than the D v (50) value of the same filler F1.

[0074] The particle size distribution is not an inherent property of the fillers F1 that results directly from their production. Rather, the biomass-based fillers are deagglomerated through comminution processes such as grinding to such an extent that the particle size distributions according to the invention result. Excessively large filler particle sizes exhibit lower reinforcement, which is reflected in a flat tensile-strain curve and thus lower tensile strength. Excessively small particle sizes impede dispersion in the polymer matrix, and the filler particles then exist as insufficiently dispersed clusters.

[0075] All the above-mentioned areas, which the fillers F1 with regard to their 14C content, carbon and oxygen content, STSA surface area and surface-available acidic groups as well as grain size distribution, apply equally to all fillers F1 to be used according to the invention, but preferably to lignin-based fillers, which represent a preferred class of fillers that can be produced from phytomass.

[0076] In their textbook "Rubber Technology - Materials Processing Products" (3rd revised and expanded edition, 2013, pages 1196-1197), Röthemeyer and Sommer classify various rubbers into three groups: those with low polarity and a high degree of swelling in oil, those with medium polarity and a medium degree of swelling in oil, and those with high polarity and a low degree of swelling in oil. Halobutyl rubbers have a low polarity despite their reactivity. Therefore, the good compatibility of the fillers F1 used according to the invention, in particular the lignin-based fillers with the halobutyl rubbers, which only have a low polarity, is particularly surprising, since the fillers used according to the invention have a high polarity compared to typical industrial carbon blacks, which is due, among other things, to the content of surface-available, acidic hydroxyl groups.But the higher oxygen content compared to industrial carbon black also contributes to this.

[0077] Among the lignin-based fillers F1, hydrothermally treated lignin-containing phytomass is particularly preferred. The preferred treatment is hydrothermal treatment at temperatures between 150°C and 250°C in the presence of liquid water. This generally increases the carbon content and decreases the oxygen content compared to the starting lignin. Suitable treatment processes are described, for example, in WO 2017 / 085278 A1. Lignin-based fillers obtained through hydrothermal treatment are also referred to below as HTT lignins ("hydrothermally treated lignins"). The term HTC lignin ("hydrothermally carbonized lignin") is also frequently used in the literature. Fillers referred to as HTC lignins also fall under the term HTT lignins. Hydrothermal treatment at temperatures between 150°C and 250°C in the presence of liquid water is also referred to below as hydrothermal treatment.The HTT lignins described below represent the preferred fillers F1 to be used in the present invention.

[0078] In one embodiment, the rubber composition according to the invention contains more than 45 phr, preferably at least 46 phr, particularly preferably 48 to 80 phr, very particularly preferably 50 to 75 phr, in particular 50 to 70 phr of the filler F1 as defined above to be used according to the invention.

[0079] In a further embodiment, the rubber composition according to the invention contains more than 35 phr, preferably at least 36 phr, particularly preferably 38 to 80 phr, very particularly preferably 40 to 70 phr, in particular 50 to 65 phr of the filler F1 as defined above to be used according to the invention in combination with one or more industrial carbon blacks F2, wherein the weighted arithmetic mean of the STSA surface areas of the industrial carbon blacks F2 is in the range of 55 m 2 / g up to 95 m 2 / g. In this embodiment, it is preferred that the sum of the fillers F1 and carbon blacks F2 in the filler component is at least 40 phr, particularly preferably at least 43 phr to 80 phr, very particularly preferably 46 to 70 phr, in particular 48 to 65 phr.

[0080] HTT lignins

[0081] HTT lignins are obtained by hydrothermal treatment of lignin-containing raw materials and represent particularly preferred fillers F1 that can be used according to the invention. The properties of HTT lignins can vary widely. For example, different HTT lignins differ in their BET and STSA surface area, ash content, pH value, and heat loss, as well as in density and particle size, the amount of surface-available acidic hydroxyl groups, and particle size distributions.

[0082] In the context of the present invention, the fillers F1 to be used according to the invention are preferably special HTT lignins as a substitute for the carbon blacks typically contained in rubber compositions for inner liners. The production of the HTT lignins that can be used according to the invention is described, for example, in WO 2017 / 085278 A1. The fillers F1 produced in this way are comminuted, in particular ground, until the required particle size distribution is achieved.

[0083] While the above-mentioned publications WO 2017 / 085278 A1 and WO 2017 / 194346 A1 generally mention the use of HTT lignins as possible substitutes for carbon blacks in tires, it should not be concluded that the behavior of HTT lignins in conventional rubber compositions is transferable to the specific rubber compositions of the present invention, which contain more reactive halobutyl rubbers. This applies particularly to their use in rubber compositions based on halobutyl rubbers, since these have completely different properties than conventional rubber compositions. Due to the high reactivity of the halogen atoms, in particular the chlorine and especially the bromine atoms, an interaction or even reaction with the fillers usable according to the invention, in particular the HTT lignins, which have a chemically different surface and nature compared to industrial carbon blacks, is to be expected.In particular, the aforementioned difference between carbon black and the fillers to be used in the present invention with regard to the presence of surface-available, acidic hydroxyl groups, preferably phenolic hydroxyl groups, leads to surprisingly good incorporation of the fillers and their compatibility with the rubber component, even without the use of compatibilizers, in particular without the use of silane compounds in the rubber compositions according to the invention. The resulting vulcanized products exhibit surprisingly good performance, improving even critical properties, such as the extremely low gas permeability required for inner liners.

[0084] It was also surprising that, contrary to the teaching of WO 2020 / 202125 A1, significantly higher amounts of fillers F1 with STSA surfaces can be used in the higher range and, in particular, combinations with carbon blacks with a high STSA surface of at least 55 m 2 / g excellent results can be achieved.

[0085] To achieve these advantages, the present invention required the targeted selection of specific fillers F1. HTT lignins have proven particularly suitable among these, as they exhibit both excellent compatibility with the other components of the rubber composition and compatibility with the special vulcanization systems described below. They particularly enable the desired gas barrier properties and reduce crack formation and crack growth.

[0086] The fillers F1 to be used according to the invention, and in particular the HTT lignins used in the present invention, enable the establishment of a good balance of various properties with regard to their use in inner liners. They possess good reinforcing properties, expressed by the tensile strength and tear strength of the vulcanized rubbers, a high elongation at break of the rubbers, and enable good dispersibility of the filler particles in the rubber. In particular, their use, especially in larger amounts, leads to significantly reduced gas permeability and reduced crack growth in the vulcanized rubbers.

[0087] To achieve this, it is advantageous that the fillers F1 used in the invention, preferably the HTT lignins, have - in addition to the STSA surface areas specified above - also BET surface areas in the range of 40 m 2 / g up to 100 m 2 / g, preferably 42 m2 / g up to 75 m 2 / g, particularly preferably 44 m 2 / g up to 70 m 2 / g.

[0088] Preferably, the fillers F1 used according to the invention, preferably the HTT lignins, have a pH in the range from 7 to 10, particularly preferably in the range from 8 to 9.5.

[0089] It was also found that the ash content and heat loss have only a minor influence as long as the values ​​are not too high and thus reduce the active ingredient content too much.

[0090] The fillers used herein, preferably the HTT lignins, have—as demonstrated in the experimental part of the present application—the potential to completely replace carbon blacks in the production of rubber compositions, particularly those used for inner liners, although the fillers F1 used here have a significantly higher STSA surface area than the industrial carbon blacks N660 and N772 commonly used in inner liners. This means that preferred rubber compositions according to the invention do not need to contain carbon blacks made from materials of fossil origin.

[0091] This makes it possible, among other things, to produce inner liners for pneumatic tires that, while maintaining the same dimensions as comparable inner liners obtained using carbon black, offer significantly lower weight, improved air retention, and improved crack resistance with reduced crack growth. It is precisely this improved air retention that ensures the tire's rolling resistance remains at its optimum over time, thus allowing for more economical operation of the vehicle equipped with the tires.

[0092] However, it is also possible to replace only a portion of the carbon blacks made from fossil-based materials with one or more of the fillers F1 usable according to the invention, preferably HTT lignins. The carbon blacks F2 described below are particularly advantageous in this case, although these far exceed the specifications of the carbon blacks commonly used in inner liners, particularly with regard to their STSA surface areas. This also opens up a new field of application for the carbon blacks F2.

[0093] Other components of the rubber composition

[0094] Fillers F2 (= industrial carbon black F2)

[0095] In addition to the aforementioned fillers F1, which are mandatory according to the invention, preferably HTT lignins F1, the rubber compositions can contain other fillers F2 in the filler component that differ from F1, namely carbon blacks with the above-mentioned specifications. The same applies analogously to the calculation of the weighted arithmetic mean of the STSA surface areas of the carbon blacks F2.

[0096] The weighted arithmetic mean of the STSA surfaces of the carbon black F2 is in the range of 55 m 2 / g up to 95 m 2 / g, preferably in the range of 60 m 2 / g up to 92 m 2 / g, particularly preferably in the range of 65 m 2 / g up to 91 m 2 / g and especially in the range of 70 m 2 / g up to 85 m 2 / g, especially 72 m 2 / g up to 80 m 2 / G.

[0097] Preferably, the STSA surface area of ​​each individual carbon black F2 (ie filler F2) is also in the range of 55 to 95 m 2 / g, particularly preferably in the range of 65 to 90 m 2 / g, most preferably in the range of 70 to 85 m 2 / g. The selection of the individual fillers F2 is, of course, subject to the mandatory requirement that the weighted arithmetic mean of the STSA surface areas of the fillers F2 lies within the ranges specified in the previous paragraph.

[0098] Surprisingly, it has been found that the use of F2 carbon blacks, as characterized above, leads to advantages in terms of higher tensile strength and, above all, higher elongation at break. In particular, the small aggregate size appears to have a positive effect on crack growth, as presumably more particles and thus more defects in the same volume unit counteract crack growth.

[0099] In comparison to the partial replacement of the fillers F1 by the carbon blacks N660 and N772 used in the inner liner production, which have a STSA surface area of ​​34 m 2 / g and 28 m 2 / g, the carbon blacks F2 characterized as above with STSA surfaces in the range of 55 to 95 m 2 / g, particularly preferably in the range of 65 to 90 m 2 / g, most preferably in the range of 70 to 85 m 2 / g to provide.

[0100] For example, carbon black N326 contains smaller aggregates due to its higher specific surface area (STSA) compared to semi-active carbon blacks N660 and N772. The inventors of the present invention suspect that, at the same dosage, more particles are present per unit volume, improving the physical interaction and producing greater reinforcement. This appears to be particularly advantageous for dynamic crack resistance.

[0101] Preferred F2 carbon blacks are those listed in ASTM D1765 and designated N3XX. These include, in particular, carbon blacks designated N326, N330, N347, N339, N375, and N351.

[0102] The fillers F2 are never used alone, but always at least in combination with the fillers F1 in the filler component. However, when using the fillers F2, the proportion of the fillers F1 is more than 35 phr, preferably at least 36 phr, particularly preferably at least 38 phr, such as at least 40 phr.

[0103] In the event that further fillers F2 with the above characteristics are used, their proportion is preferably less than 25 phr, particularly preferably 1 to 25 phr, particularly preferably 5 to 20 phr, and very particularly preferably 8 to 18 phr.

[0104] Preferably, the sum of the amounts of fillers F1 and carbon blacks F2 is at least 45 phr, particularly preferably 45 to 80 phr, very particularly preferably 45 to 70 phr, and even more preferably 45 to 60 phr.

[0105] The proportion of fillers F1 in the sum of all fillers F1 plus F2 is preferably 50 to 100 wt.%, particularly preferably 65 to 100 wt.% and very particularly preferably 80 to 100 wt.%.

[0106] The weighted arithmetic mean of the STSA surfaces of the sum of the fillers F1 and carbon black F2 is at least 40 m 2 / g, particularly preferably 45 m 2 / g up to 65 m 2 / g, most preferably 47 m 2 / g up to 63 m 2 / g and even more preferably 50 m 2 / g up to 60 m 2 / g. Fillers F3

[0107] In addition to the fillers F1 and the optionally present fillers / carbon blacks F2, the rubber composition of the present invention may contain further fillers F3 that do not fall under the definitions of fillers F1 and F2. These include, in particular, inorganic fillers of different particle size, particle surface area, and chemical nature with different potential to influence the vulcanization behavior. If further fillers are present, these should preferably have properties as similar as possible to those of the fillers F1 and F2 used in the rubber composition of the invention.

[0108] If additional F3 fillers are used, these are preferably layered silicates such as clay minerals, for example, talc; carbonates such as calcium carbonate; and silicates such as calcium, magnesium, and aluminum silicate. However, they can also be F3 fillers that each have an STSA surface area of ​​less than 40 m 2 / g or greater than 80 m 2 / g and otherwise meet the requirements of the fillers F1 with regard to the 14 C content and carbon content, preferably also meeting the requirements regarding particle size distribution and acidic hydroxyl groups. However, the fillers F3 can also be industrial carbon blacks F3 with an STSA surface area of ​​less than 55 m 2 / g or greater 95 m 2 / g.

[0109] Inorganic fillers, preferably silica and other fillers bearing Si-OH groups on their surface, can also be surface-treated. In particular, silanization with organosilanes such as alkylalkoxysilanes, aminoalkylalkoxysilanes, or marcaptoalkylalkoxysilanes can be advantageous. The alkoxysilane groups can bond, for example, to the surfaces of silicates or silica or to other suitable groups by hydrolytic condensation, while the amino groups and thiol groups, for example, can react with the halogenated, especially brominated, isoprene units of the halobutyl rubbers. This can result in mechanical reinforcement of the vulcanized rubber compositions of the present invention.

[0110] The use of silanized fillers can accelerate the attainment of the final vulcanization state and increase the tear resistance.

[0111] The fillers can be used individually or in combination.

[0112] Preferably, in addition to the fillers F1 used according to the invention, in particular the HTT lignins F1 and the optionally present further fillers F2, no or only small amounts of fillers F3 are used. If further fillers F3 are used, these are preferably carbon blacks F3 that do not fall under the definition of carbon blacks F2, or phyllosilicates such as clay minerals and, for example, talc are preferred. The proportion of fillers F3 in the filler component is preferably less than 40 phr, more preferably 0 to 25 phr, most preferably 0 to 15 phr.

[0113] plasticizers

[0114] The use of plasticizers can influence properties of the unvulcanized rubber composition, such as processability, but also properties of the vulcanized rubber composition, such as its flexibility, especially at low temperatures.

[0115] Particularly suitable plasticizers within the scope of the present invention are mineral oils from the group of paraffinic oils (essentially saturated chain-like hydrocarbons) and naphthenic oils (essentially saturated cyclic hydrocarbons). The use of aromatic hydrocarbon oils is possible, but less advantageous, as they exhibit poorer solubility behavior compared to halobutyl rubbers. However, a mixture of paraffinic and / or naphthenic oils with aromatic oils as plasticizers can be advantageous with regard to the adhesion of the rubber composition to other rubber-containing components in tires, such as the carcass.

[0116] Other plasticizers include esters of aliphatic dicarboxylic acids such as adipic acid or sebacic acid, paraffin waxes and polyethylene waxes.

[0117] Among the plasticizers, paraffinic oils and naphthenic oils are particularly suitable for the purposes of the present invention.

[0118] Preferably, plasticizers and, most preferably, paraffinic and / or naphthenic oils are used in an amount of 0 to 20 phr, preferably 5 to 15 phr, particularly preferably 7 to 13 phr.

[0119] Tackifying resins

[0120] To improve the adhesion of the vulcanized rubber compound of the present invention to other adjacent tire components, so-called adhesion-enhancing resins can be used.

[0121] Particularly suitable resins are those based on phenol, preferably from the group consisting of phenolic resins, phenol-formaldehyde resins and phenol-acetylene resins.

[0122] In addition to phenol-based resins, aliphatic hydrocarbon resins such as Escorez™ 1102 RM from ExxonMobil, as well as aromatic hydrocarbon resins, can also be used. Aliphatic hydrocarbon resins particularly improve adhesion to other rubber components of the tire. They generally have lower adhesion than phenol-based resins and can be used alone or in blends with phenol-based resins.

[0123] If adhesion-enhancing resins are used, they are preferably selected from the group consisting of phenol-based resins, aromatic hydrocarbon resins, and aliphatic hydrocarbon resins. Their proportion is preferably 0 to 15 phr or 1 to 15 phr, particularly preferably 2 to 10 phr, and most preferably 3 to 8 phr.

[0124] Vulcanization-promoting additives

[0125] The rubber composition according to the invention may also contain additives that promote vulcanization but are not capable of initiating it independently. Such additives include, for example, vulcanization accelerators such as saturated fatty acids containing 12 to 24, preferably 14 to 20, and particularly preferably 16 to 18 carbon atoms, such as stearic acid and the zinc salts of the aforementioned fatty acids. Thiazoles may also be included among these additives. However, it is also possible to use vulcanization-promoting additives only in the vulcanization systems described below.

[0126] If vulcanization-promoting additives, and in particular the aforementioned fatty acids and / or their zinc salts, preferably stearic acid and / or zinc stearate, are used in the rubber compositions according to the invention, their proportion is preferably 0 to 5 phr, particularly preferably 0.5 to 3 phr, and particularly preferably 1 to 2 phr. Thus, in addition to the mandatory constituents, the rubber composition according to the invention preferably contains one or more constituents selected from the group consisting of i. rubbers other than halobutyl rubbers, ii. industrial carbon blacks F1 and / or fillers F3, iii. plasticizers, iv. adhesion-enhancing resins, and v. vulcanization-promoting additives.

[0127] If one or more of the constituents listed under points i. to v. above are present, then i. is preferably a rubber selected from the group consisting of natural rubber, butyl rubber and styrene-butadiene rubber, ii. is a filler F2 as defined above or a filler F3 selected from the group of carbon blacks other than F2 and layered silicates, iii. is preferably an ester of an aliphatic dicarboxylic acid, a paraffinic oil and / or a naphthenic oil, iv. is a resin selected from the group of aliphatic hydrocarbon resins, aromatic hydrocarbon resins, phenolic resins, phenol-formaldehyde resins and phenol-acetylene resins; and v. is an additive selected from the group of saturated fatty acids having 12 to 24 carbon atoms and thiazoles.

[0128] If components i. to v. are present, they are preferably present in the following amounts: i. 0 to 40 phr, particularly preferably 0 to 30 phr, very particularly preferably 0 to 20 phr or 0 phr; ii. 0 to 40 phr, further preferably 0 to 25 phr, particularly preferably 0.1 to 20 phr, very particularly preferably 0.5 to 18 phr; iii. 0 to 20 phr, particularly preferably 5 to 15 phr, very particularly preferably 7 to 13 phr; iv. 0 to 15 phr, particularly preferably 2 to 10 phr, very particularly preferably 3 to 8 phr; and v. 0 to 5 phr, particularly preferably 0.5 to 3 phr, very particularly preferably 1 to 2 phr.

[0129] Vulcanizable rubber composition

[0130] The vulcanizable rubber compositions of the present invention comprise a rubber composition according to the invention and a vulcanization system for vulcanizing the same.

[0131] Vulcanization systems

[0132] The vulcanization systems are not considered part of the rubber compositions according to the invention, but are treated as additional systems that cause crosslinking. The addition of the vulcanization systems to the rubber compositions according to the invention produces the vulcanizable rubber compositions according to the invention.

[0133] The halobutyl rubber-based rubber compositions of the present invention allow the use of a wide variety of different vulcanization systems. The weaker chlorine-carbon bond, and especially the bromine-carbon bond, compared to a carbon-carbon bond allows for faster vulcanization and better co-vulcanization with general-purpose rubbers.

[0134] The vulcanization of the rubber compositions of the present invention is preferably carried out using zinc oxide and / or sulfur.

[0135] In the preferred variants described below, zinc oxide is preferably used in combination with various organic compounds for vulcanization. The different additives can influence both the vulcanization behavior and the properties of the resulting vulcanized rubbers.

[0136] In a first variant of zinc oxide-based vulcanization, small amounts of a saturated fatty acid containing 12 to 24, preferably 14 to 20, and particularly preferably 16 to 18 carbon atoms, such as stearic acid and / or zinc stearate, are preferably added to the zinc oxide as a vulcanization accelerator. This allows the vulcanization rate to be increased. However, the final extent of vulcanization is usually reduced when using these fatty acids.

[0137] In a second variant of zinc oxide-based vulcanization, so-called thiurams such as thiuram monosulfide and thiuram disulfide and / or dithiocarbamates are added to the zinc oxide, in the absence of sulfur, in order to shorten the scorching time and improve the vulcanization efficiency by forming particularly stable networks.

[0138] In a third variant of zinc oxide-based vulcanization, an alkylphenol disulfide is added to the zinc oxide in order to adjust, and in particular to accelerate, the scorching times.

[0139] A further, fourth variant of zinc oxide-based vulcanization uses a combination of zinc oxide with polymethylolphenol resins and their halogenated derivatives, in which neither sulfur nor sulfur-containing compounds are used.

[0140] In a further, fifth variant of zinc oxide-based vulcanization, vulcanization is carried out using a combination of zinc oxide with thiazoles and / or sulfenamides, and preferably sulfur. The thiazoles and sulfenamides are preferably selected from the group consisting of 2-mercaptobenzothiazole (MBT), mercaptobenzothiazyl disulfide (MBTS), N-cyclohexyl-2-benzothiazyl-sulfenamide (CBS), 2-morpholinothiobenzothiazole (MBS), and N-tert-butyl-2-benzothiazyl-sulfenamide (TBBS). The addition of sulfur to such systems increases both the vulcanization rate and the extent of vulcanization and contributes to the processability of the rubber compositions during the vulcanization process. Co-vulcanization with rubbers other than halobutyl rubbers, especially those mentioned above, is also favored.The use of this vulcanization system preferably produces heat- and fatigue-resistant vulcanizates that, even in the vulcanized state, exhibit good adhesion to other components of vehicle tires, particularly carcass rubber compositions. A particularly advantageous vulcanization system comprises zinc oxide, a thiazole such as preferably mercaptobenzothiazyl disulfide (MBTS), and sulfur. Particularly preferred is the combination of the first variant with the fifth variant, i.e., the use of a vulcanization system comprising zinc oxide, a thiazole such as preferably mercaptobenzothiazyl disulfide (MBTS), sulfur, and stearic acid and / or optionally zinc stearate.

[0141] Less preferred vulcanization systems are based on pure sulfur vulcanization or peroxide vulcanization, the latter of which can lead to an undesirable reduction in molecular weights due to splitting of the molecules, particularly when butyl rubber or other rubbers are used.

[0142] In the context of the present invention, the vulcanization of the rubber composition according to the invention takes place in the presence of the specific fillers F1, preferably the specific HTT lignins and optionally the carbon black F2. The outstanding properties of the vulcanized rubber composition according to the invention, in particular its suitability as an inner liner, are essentially based on the combination of the suitable rubber component with the specific fillers F1, in particular the preferred HTT lignins F1 and optionally F2 in the prescribed amounts and a zinc oxide-based vulcanization system, preferably a vulcanization system of the variant referred to above as the fifth variant, even more preferably the combination of the first with the fifth variant.

[0143] Components of the vulcanization systems that cannot trigger vulcanization as such can also be included in the rubber composition of the present invention as "further components of the rubber composition." Thus, it is possible that, in particular, the stearic acid and / or optionally zinc stearate and / or the thiazole compound are already present in the rubber composition, and the complete vulcanization system is formed in situ by the addition of zinc oxide and sulfur.

[0144] Kit of parts

[0145] Due to the relationship between the rubber compositions of the invention and the crosslinking systems to be selected for their vulcanization, the present invention also relates to a kit of parts comprising the rubber composition of the invention and a vulcanization system, preferably a vulcanization system based on zinc oxide and / or sulfur. In the kit of parts, the rubber composition of the invention and the vulcanization system are spatially separated from one another and can thus be stored. The kit of parts serves to produce the vulcanizable rubber composition. For example, the rubber composition of the invention constituting one part of the kit of parts can be used as part (A) in stage 1 of the process described below for producing a vulcanizable rubber mixture, and the second part of the kit of parts, namely the vulcanization system, can be used as part (B) in stage 2 of said process.Preferably, the kit of parts includes.

[0146] Part (A) a rubber composition according to the present invention and as

[0147] Part (B) a vulcanization system comprising zinc oxide and / or sulfur.

[0148] Particularly preferably, the kit of parts includes

[0149] Part (A) a rubber composition according to the present invention and as

[0150] Part (B) a vulcanization system comprising zinc oxide, sulfur and a thiazole; or as

[0151] Part (A) a rubber composition according to the present invention containing a thiazole and as

[0152] Part (B) a vulcanization system comprising zinc oxide, sulfur.

[0153] Most preferably, the kit of parts includes

[0154] Part (A) a rubber composition according to the present invention, and as

[0155] Part (B) a vulcanization system comprising zinc oxide, sulfur, a thiazole and stearic acid and optionally zinc stearate; or as

[0156] Part (A) a rubber composition according to the present invention containing stearic acid and optionally zinc stearate, and as

[0157] Part (B) a vulcanization system comprising zinc oxide, sulfur and a thiazole.

[0158] Preferred thiazole in the above kit of parts is MBTS.

[0159] In contrast to the vulcanizable rubber composition, which already contains both the components of the inventive rubber composition and the associated vulcanization system homogeneously mixed, so that the vulcanizable rubber composition is vulcanized directly, in the kit of parts the inventive rubber composition and the vulcanization system are spatially separated. The vulcanizable rubber composition obtainable from the kit of parts is also referred to herein as a "green compound." It can be obtained using the two-step process described in the following section.

[0160] Process for producing the rubber composition according to the invention and a vulcanizable rubber composition from this

[0161] The vulcanizable rubber mixture is preferably produced in two stages.

[0162] In the first step, the rubber composition according to the invention is prepared as a masterbatch by compounding the components of the rubber composition. In the second step, the components of the vulcanization system are added.

[0163] Level 1

[0164] Preferably, the halobutyl rubbers and any additional rubbers used, as well as any adhesion-enhancing resins used, are initially introduced. However, the latter can also be added with the other additives. The rubbers are preferably at least at room temperature (23°C) or are preheated to temperatures of no more than 50°C, preferably no more than 45°C, and particularly preferably no more than 40°C. It is particularly preferred that the rubbers be pre-kneaded for a short period before the other components are added. If inhibitors, such as magnesium oxide, are used for later vulcanization control, these are preferably also added at this time.Subsequently, the fillers F1 to be used according to the invention, preferably as HTT lignins, and optionally further fillers F2 and / or F3 are added, preferably with the exception of zinc oxide, since this is used in the rubber compositions according to the invention as a component of the vulcanization system and is therefore not considered a filler herein. The addition of the fillers F1 to be used according to the invention, preferably the HTT lignins, and optionally further fillers F2 and / or F3, is preferably carried out incrementally.

[0165] Advantageously, but not necessarily, plasticizers and other components such as stearic acid and / or zinc stearate are only added after the addition of the fillers F1 to be used according to the invention, preferably HTT lignins or the further fillers F2 and / or F3, if used. This facilitates the incorporation of the fillers F1 to be used according to the invention, preferably HTT lignins and, if present, the further fillers F2 and / or F3. However, it can be advantageous to incorporate some of the fillers F1 to be used according to the invention, preferably HTT lignins or, if present, the further fillers F2 and / or F3, together with the plasticizers and any further components used.

[0166] The highest temperatures reached during the first-stage production of the rubber composition ("dump temperature") should not exceed 140 °C, as above these temperatures there is a risk of partial decomposition of the reactive halobutyl rubbers. The maximum temperature during the first-stage production of the rubber composition is preferably between 100 °C and 130 °C, particularly preferably between 105 °C and 120 °C.

[0167] The components of the rubber composition according to the invention are usually mixed using internal mixers equipped with tangential or meshing (i.e., intermeshing) rotors. The latter generally allow for better temperature control. However, mixing can also be carried out using a twin-roll mixer, for example.

[0168] After the rubber composition has been prepared, it is preferably cooled before the second step. This process is also referred to as aging. Typical aging periods are 6 to 24 hours, preferably 12 to 24 hours.

[0169] Level 2

[0170] In the second stage, the components of the vulcanization system are incorporated into the rubber composition of the first stage, whereby a vulcanizable rubber composition according to the present invention is obtained.

[0171] If a zinc oxide-based vulcanization system is used, the zinc oxide and the other components, such as sulfur and particularly preferably thiazole, are added in stage 2.

[0172] The highest temperatures (dump temperature) achieved during the preparation of the vulcanization system admixture to the rubber composition in the second stage should preferably not exceed 110 °C, particularly preferably 105 °C. A preferred temperature range is between 90 °C and 110 °C, particularly preferably between 95 °C and 105 °C. At temperatures above 105 to 110 °C, premature vulcanization may occur.

[0173] After the vulcanization system has been added in stage 2, the composition is preferably cooled.

[0174] In the above-mentioned two-stage process, a rubber composition according to the invention is thus initially obtained in the first stage, which is supplemented in the second stage to form the vulcanizable rubber composition, in particular the vulcanizable inner liner rubber composition.

[0175] Process for further processing of the vulcanizable rubber composition according to the invention

[0176] The vulcanizable rubber compositions obtained in the second-stage process described above are preferably further processed by calendering, extrusion or the roller-head process.

[0177] Calendering

[0178] The vulcanizable rubber composition of the present invention is preferably fed to the calender in a first step (a), for example, using a preheating roll mill and a downstream feed roll mill, or by extrusion using an extruder. In both cases, the vulcanizable rubber composition should have a temperature of preferably 65°C to 85°C, particularly preferably 70°C to 80°C, before being fed to the calender.

[0179] In the second step (b), calendering takes place, with various roll positions of the preferably three or four rolls of the calender being possible. Calendering is preferably carried out using a four-roll Z-calender (inclined Z-calender) or a four-roll L-calender (inverted L-calender). The cooler take-up rolls preferably have a temperature of 75°C to 85°C, while the warmer rolls preferably have a temperature of 85°C to 95°C.

[0180] After calendering, in a third step (c), the calendered vulcanizable rubber composition leaves the calender as a calendered sheet and is cooled before post-processing, preferably to temperatures below 35 °C. Once the calendered sheets leave the calender, several calendered sheets can be consolidated in multiple layers. Care must be taken to ensure that no unwanted air inclusions occur during the consolidation process.

[0181] Following these three steps, it is advantageous to store the calendered webs or the multi-layer consolidated calendered webs in a fourth step (d) for at least 3 hours, better still for at least 4 hours, and preferably at least 12 to 24 hours. This storage allows the calendered webs to cool completely and allows for stress relaxation.

[0182] Calendering is preferably carried out at calendering speeds in the range of 20 to 35 m / min, particularly preferably 25 to 30 m / min.

[0183] Extrude

[0184] In addition to calendering, it is also possible to obtain inner liners by extrusion.

[0185] The vulcanizable rubber composition of the present invention is preferably fed to the extruder in a first step (a), for example, via a twin-roll mixer or other suitable feed device. The vulcanizable rubber composition should preferably have a temperature of 65°C to 85°C, particularly preferably 70°C to 80°C, before being fed to the calender.

[0186] In the second step (b), extrusion, temperatures of 100 °C can be reached. Therefore, special care must be taken to prevent scorching.

[0187] After extrusion, in a third step (c), the extruded vulcanizable rubber composition leaves the extruder as a sheet and is cooled before post-processing, preferably to temperatures below 35 °C. Once the sheets leave the extruder, several sheets can be consolidated into multiple layers. Care must be taken to ensure that no unwanted air inclusions occur during the consolidation process.

[0188] Following these three steps, it is advantageous to store the sheets or multi-layer consolidated sheets in a fourth step (d) for at least 3 hours, better still for at least 4 hours, and preferably at least 12 to 24 hours. This storage allows the sheets to cool completely and allows for stress relaxation.

[0189] Roller-head process

[0190] In contrast to calendering with multiple rolls, as described above, in the roller-head process, the calender gap of a two- or three-roll calender is fed with a rubber compound from an extruder with a wide-diameter die head. The extruder itself can be fed hot or cold. A cold-feed pin extruder, for example, can be used. The roll gap (calender gap) can be optimally fed if the supplied compound is adapted to the thickness and width of the web to be calendered. This is achieved by selecting the wide-diameter die head and the replaceable injection bars mounted at its end.

[0191] In terms of operating behavior, roller-head systems lie between extruders and calenders, whereby the uniform flow in the extruder nozzle determines quality and dimensions when producing thicker webs, while the calender behavior predominates for thinner webs.

[0192] The operating temperatures are in the range of calendering and extrusion as described above for these processes.

[0193] As already described in connection with calendering, the finished webs must be cooled after leaving the calender according to step (c) above, which is preferably followed by step (d) above. The calendered, extruded, or vulcanizable webs obtained via the roller-head process preferably have a layer thickness of 0.3 to 5 mm, more preferably 0.4 to 4 mm, and most preferably 0.5 to 3 mm. These layer thickness ranges are typical for inner liners.

[0194] Vulcanized rubber compositions

[0195] The present invention further relates to vulcanized rubber compositions which are obtainable from the vulcanizable rubber compositions described above, for example also using a kit of parts.

[0196] The vulcanization conditions depend on the vulcanization system used. Suitable vulcanization temperatures are preferably between 140 °C and 200 °C, particularly preferably between 150 °C and 180 °C.

[0197] Preferably, the vulcanized rubber composition is the inner liner of a pneumatic tire.

[0198] Properties of the vulcanized rubber composition

[0199] The vulcanized rubber compositions obtained from the vulcanizable rubber compositions according to the invention preferably have

[0200] (a) a Shore A hardness in the range from 35 to 65, more preferably from 38 to 60 and most preferably from 40 to 55; and / or

[0201] (b) a modulus 300 of 2.8 MPa to 8 MPa, more preferably of 3.0 MPa to 6.0 MPa and most preferably of 3.0 MPa to 4.0 MPa; and / or (c) a density of 1,000 g / cm 3 up to 1,120 g / cm 3 , particularly preferably 1,010 g / cm 3 up to 1,100 g / cm 3 and most preferably 1,020 g / cm 3 up to 1,080 g / cm 3 ; and / or

[0202] (d) a gas permeability of less than 3.8 x 10' 17 m 2 / Pas, particularly preferably a gas permeability of 2.5 x 10' 17 m 2 / Pas up to 3.8 x 10' 17 m 2 / Pas and especially preferably 2.7 x 10' 17 m 2 / Pas up to 3.7 x 10' 17 m 2 / Pas such as 2.8 x 10' 17 m 2 / Pas up to 3.5 x 10'17 m 2 / Pas.

[0203] In general, a higher content of fillers F1 usable according to the invention, especially HTT lignins and any other fillers present, generally further reduces gas permeability, but this is at the expense of the tensile strength and elongation at break of the mixture. By partially replacing the fillers F1 with the carbon blacks F2, both the tensile strength and the elongation at break can be significantly increased without significantly impairing the other properties.

[0204] Process for producing a pneumatic tire comprising an inner liner made of the vulcanizable rubber composition according to the invention

[0205] The vulcanizable sheets obtained by the above processes are preferably stored in roll form until use and serve as inner liner material in the manufacture of pneumatic tires. For this purpose, the sheets must be cut to the drum circumference, which is possible using ultrasonic knives or heated rotating circular knives, with the latter preferably using the so-called roll-on-and-cut process.

[0206] The inner liners are typically vulcanized together with the tire carcass and / or other tire components under pressure and / or heat. Suitable vulcanization temperatures are preferably between 140°C and 200°C, particularly preferably between 150°C and 180°C.

[0207] The process can, for example, be carried out by closing the press and then molding the green tire into the closing mold. To do this, an inner bladder (heating bladder) can be subjected to a slight pressure (< 0.2 bar) so that the bladder also inserts itself into the green tire. The press and thus also the mold are then completely closed. The pressure in the bladder is increased (crowning pressure, usually approx. 1.8 bar). This embosses the profile and sidewall lettering into the tread. In the next step, the press is locked and the closing force is applied. The closing force varies depending on the press type and tire size and can be up to 2500 kN using hydraulic cylinders. Once the closing forces have been applied, the actual vulcanization process begins. The mold is continuously heated from the outside with steam. Temperatures here are usually set between 150 and 180 °C.The inner medium varies greatly depending on the tire type. For example, steam or hot water is used inside the bladder. The internal pressures can vary and differ depending on the tire type, such as car or truck tires.

[0208] All measured variables mentioned in the present description in connection with the present invention are determined according to the methods mentioned in the experimental part.

[0209] Use of the fillers F1 to be used according to the invention, in particular the HTT lignins F1 and mixtures of F1 with F2.

[0210] The present application further relates to the use of the fillers F1 as defined above in connection with the rubber composition according to the invention, preferably the HTT lignins, or mixtures of the fillers F1 with the carbon blacks F2, which are also as defined above, in rubber compositions for inner liners, wherein the fillers F1 and carbon blacks F2 are used in a total amount of at least 46 phr.

[0211] The use serves in particular to reduce gas permeability and crack growth, especially in comparison with rubber compositions containing carbon black N660 and / or carbon black N772 instead of F1 and / or F2.

[0212] EXAMPLES

[0213] The components of the rubber composition, the unvulcanized rubber composition and the vulcanized rubber composition were subjected to various test procedures, which are described in more detail below.

[0214] Characterization of fillers F1 and F2

[0215] Mass-related surface area (BET surface area and STSA surface area)

[0216] The specific surface area of ​​HTT lignin was determined by nitrogen adsorption according to the ASTM D 6556 (2019-01-01) standard for carbon black. According to this standard, the BET surface area (Brunauer, Emmett, and Teller specific surface area) and the external surface area (STSA surface area; Statistical Thickness Surface Area) were determined as follows.

[0217] The sample to be analyzed was dried to a dry matter content of > 97.5 wt.% at 105 °C prior to measurement. Furthermore, the measuring cell was dried in a drying oven at 105 °C for several hours before weighing the sample. The sample was then filled into the measuring cell using a funnel. If the upper measuring cell shaft became contaminated during filling, it was cleaned using a suitable brush or pipe cleaner. For highly airborne (electrostatic) material, glass wool was weighed in addition to the sample. The glass wool served to retain any material that might be released during the annealing process and contaminate the device.

[0218] The sample to be analyzed was heated at 150 °C for 2 hours, and the Al2O3 standard was heated at 350 °C for 1 hour. The following N2 dosage was used for the determination, depending on the pressure range: p / pO = 0 - 0.01 : N2 dosage: 5 ml / g p / pO = 0.01 - 0.5 : N2 dosage: 4 ml / g

[0219] To determine the BET, extrapolation was performed in the range of p / pO = 0.05 - 0.3 with at least 6 measurement points. To determine the STSA, extrapolation was performed in the range of the layer thickness of the adsorbed N2 of t = 0.4 - 0.63 nm (corresponding to p / pO = 0.2 - 0.5) with at least 7 measurement points.

[0220] Determination of pH value

[0221] The pH value was determined in accordance with ASTM D 1512 as follows. The dry sample, unless already in powder form, was ground or crushed into a powder. 5 g of sample and 50 g of deionized water were weighed into a beaker. The suspension was heated to 60°C with continuous stirring using a magnetic stirrer with a heating function and stirring bar, and the temperature was held at 60°C for 30 minutes. The stirrer's heating function was then deactivated so that the mixture could cool while stirring. After cooling, the evaporated water was replenished by adding more deionized water and stirred again for 5 minutes. The pH value of the suspension was determined using a measuring device. The temperature of the suspension should be 23°C (± 0.5°C). A duplicate determination was carried out for each sample, and the average value is reported.

[0222] Determination of bulk density

[0223] The bulk density of the sample was determined according to ISO 697 as follows. A standard beaker according to DIN ISO 60 (volume 100 ml) for bulk density determination was placed in a bowl to collect the overflow. Using a funnel and scoop, the beaker was filled to overflowing. The supernatant was removed from the beaker rim using a straight edge of the scoop. The outside of the beaker was wiped with a dry cloth and weighed to an accuracy of 0.1 g.

[0224] Determination of surface-available acidic hydroxy groups (OH group density)

[0225] The surface-accessible acidic hydroxyl groups were determined qualitatively and quantitatively using colorimetric methods according to Sipponen. The Sipponen method is based on the adsorption of the basic dye Azure B onto the acidic hydroxyl groups accessible on the filler surface and is described in detail in the article "Determination of surface-accessible acidic hydroxyls and surface area of ​​lignin by cation dye adsorption" (Bioresource Technology 169 (2014) 80-87). The amount of surface-accessible acidic hydroxyl groups is expressed in mmol / g filler. Regardless of the filler source, the method was applied not only to lignin-based fillers but also, for example, to the reference carbon black N660.

[0226] Determination of the 14 C content

[0227] The determination of the 14 C content (content of bio-based carbon) can be determined using the radiocarbon method according to DIN EN 16640:2017-08.

[0228] Determination of grain size distribution

[0229] The particle size distribution can be determined by laser diffraction of the material dispersed in water (1 wt.% in water) according to ISO 13320:2009, with an ultrasonic treatment of 12000 Ws prior to the measurement. The volume fraction is expressed, for example, as D v (97) in pm (diameter of the grains of 97% of the sample volume is below this value). For the D v (50) value the analogous consideration applies.

[0230] Characterization of vulcanizable rubber compounds (“Green Compounds”)

[0231] Determination of reaction kinetics / vulcanization kinetics

[0232] The reaction kinetics of unvulcanized rubber compounds (“green compounds”) were determined using a MDR 3000 Professional rheometer (MonTech Werkstoffprüfmaschinen GmbH, Buchen, Germany) by determining the time course of the torque [dNm] according to DIN 53529 TI 3 (torsional shear vulcanometer without rotor). The upper and lower rotor plates of the rheometer were heated to 160 °C. 5.5 g ± 0.5 g of the unvulcanized

[0233] Rubber compounds were cut out of the center of the sheet with scissors. Care was taken to ensure that the cutout represented a square area and that the diagonal of this area corresponded to the diameter of the rheometer rotor. Before placing the unvulcanized rubber compound on the rheometer rotor, the top and bottom of the cutout were covered with foil. The measurement was started immediately after placing the unvulcanized sample.

[0234] From the measurement curves, the minimum and maximum torque (ML, MH) were determined within a 30-minute test phase at 160 °C (0.5° arc, 1.67 Hz) and the difference A (MH-ML) was calculated from this.

[0235] Furthermore, for each of the measurement curves, the minimum torque ML was defined as 0% of the maximum torque MH, and the maximum torque MH was standardized as 100%. Subsequently, the time periods in which the torque, starting from the time of the minimum torque ML, reaches 10%, 50%, and 90% of the maximum torque MH were determined. These time periods were designated as T ,

[0236] Tso and T90.

[0237] Characterization of vulcanized rubber compositions

[0238] Determination of Shore A hardness

[0239] The Shore A hardness of vulcanized rubber compositions was determined using a digital Shore hardness tester from Sauter GmbH in accordance with ISO 7619-1. Before each measurement, the device was calibrated using the enclosed calibration plate. To measure the hardness, three S2 bars, punched out for tensile testing according to DIN 53504, were stacked on top of each other. The hardness measurements were taken at five different locations on the stack. The Shore A hardness of vulcanized rubber compositions represents the average of the five measurements. Between vulcanization and testing, the sample was stored in the laboratory at room temperature for at least 16 hours.

[0240] Determination of the density of the vulcanized rubber composition

[0241] The density of the vulcanized rubber compositions was determined according to DIN EN ISO 1183-1:2018-04 (Method for determining the density of non-foamed plastics) Method A (immersion method). Ethanol was used as the immersion medium. The density of the vulcanized rubber composition represents the mean value of a triplicate determination. Between vulcanization and testing, the sample was stored in the laboratory at room temperature for at least 16 hours.

[0242] Determination of gas permeability

[0243] The determination of the gas permeability of the vulcanized rubber composition to air was carried out according to ISO 15105. The measurements were performed at 70 °C. Gas permeability represents the average of three measurements. Between vulcanization and testing, the sample was stored in the laboratory at room temperature for at least 16 hours.

[0244] Determination of compression set

[0245] Compression deformation was determined on vulcanized rubber compositions according to DIN ISO 815-1:2016-09. Three test specimens were tested per sample. The exposure time was 22 hours, measured from the moment the compression set unit was placed in the oven. The test temperature was 70 °C. The applied compressive stress was 25% of the initial thickness of the test specimen. Between vulcanization and testing, the specimens were stored at room temperature for at least 16 hours.

[0246] Determination of tensile strength, elongation at break and stress values ​​(moduli)

[0247] Tensile testing is used to determine the ultimate tensile strength, ultimate elongation, and stress values ​​of non-preloaded specimens. In tensile testing, the specimens are stretched at a constant strain rate until they break, and the force and length change required for this are recorded.

[0248] Tear strength: The tear strength oR is the quotient of the force FR measured at the moment of tearing and the initial cross-section AO of the test specimen.

[0249] Tensile strength: The tensile strength omax is the quotient of the measured maximum force Fmax and the initial cross-section AO of the specimen. For elastomers, the force occurring at break is generally also the maximum force Fmax.

[0250] Elongation at break: The elongation at break (sR) is the quotient of the change in length LR - L0 measured at the moment of break and the original gauge length L0 of the specimen. It is expressed as a percentage. For the bar specimens used, L0 is the specified distance between two measuring marks.

[0251] Stress value: The stress value oi is the tensile force Fi present at a certain strain, relative to the initial cross-section AO. For bar specimens, the strain is related to the original gauge length LO, i.e., the specified distance between the gauge marks.

[0252] The tensile strength, elongation at break, and stress values ​​of the vulcanized rubber composition were determined using a Tensor Check test instrument from Gibitre Instruments in accordance with ISO 37. Between vulcanization and testing, the sample was stored in the laboratory at room temperature for at least 16 hours. To determine the modulus, at least five dumbbell test specimens were punched from the vulcanized rubber composition with the sample dimensions listed in ISO 37 (bar type S2). The thickness of the specimen was determined using a calibrated thickness gauge from Käfer Dial Gauges and represents the average of three measurements taken at different positions on the web. The crosshead speed during the tensile test was 200 mm / min. The stated measured values ​​for tensile strength, elongation at break, and stress values ​​(moduli 100, 200, 300) are averages of five measurements.

[0253] De Mattia crack growth test according to DIN 53522

[0254] The fatigue buckling test, used to assess an elastomer's resistance to crack growth, is carried out using dynamic testing with a De Mattia test device. The specimen (140 x 25 x 6.3 mm) has a transverse groove and is deformed by compression using an eccentric drive. 300 buckling cycles occur per minute, with the specimens being bent to 40% of their clamped length. The specimens are pierced in the center of the groove with a cutting tool specified in the standard, creating a 2 mm crack before the start of the test. The test is continued until the crack length has changed significantly. The number of cycles is recorded until a certain crack length is reached.

[0255] Volume swelling with toluene and calculation of the M c

[0256] Crosslinked polymers swell in solvents up to a certain equilibrium value, which is a function of the degree of crosslinking. This can be determined by the swelling strain.

[0257] From the swelling behavior of elastomers, the mean molecular network length M c which is one of the most important structural parameters of a polymer network. This parameter is crucial for the mechanical properties of elastomers.

[0258] M c is obtained from the relationship: M c = A / B* q 5 / 3

[0259] M c = average molecular mass between two cross-linking sites

[0260] A = Density of rubber * Molar volume of solvent

[0261] B = 0.5 - Flory-Huggins constant (here 0.35) q = degree of swelling

[0262] The degree of swelling q corresponds to the reciprocal of the volume fraction q = 1 / V2. The value V2 is calculated using the following equation: V2 = 1 / (I + V1A / 0), where V1 is the volume of the solvent and Vo is the volume of the unswollen rubber. The ratio V1 / 0 is determined using the following equation:

[0263] V1 / 0 = (m q - m0) / p / mo / pm q = mass of the swollen rubber mo = mass of the rubber before swelling p L = density of the solvent p = density of the rubber.

[0264] Manufacturing examples

[0265] Production of the HTT lignins used in the invention

[0266] The three fillers F1A, F1B, and F1C, derived from renewable raw materials, were characterized as shown in Table 1. The characterization results were compared with commercially available and ASTM-standardized industrial carbon blacks of the types N660, N772, and N326.

[0267] The fillers F1A, F1B and F1C were prepared by hydrothermal treatment of lignin, as described in detail in WO 2017 / 085278 A1.

[0268] For this purpose, a lignin-containing liquid was prepared. First, water and lignin were mixed to produce a lignin-containing liquid with a dry organic matter content of 15 wt.%. The lignin was then largely dissolved in the lignin-containing liquid. For this purpose, the pH was adjusted by adding NaOH. The solution was prepared by intensive mixing at 80 °C for 3 h. The lignin-containing liquid was then subjected to hydrothermal treatment to obtain a solid. The prepared solution was heated at 2 K / min to a reaction temperature of 220 °C, which was maintained for a reaction time of 8 h. Cooling then followed. The result was an aqueous solid suspension. The solid was largely dewatered and washed by filtration and washing.Subsequent drying and thermal treatment took place under nitrogen in a fluidized bed. The drying process involved heating to a temperature of 50°C at 1.5 K / min and holding for 2.5 hours. The thermal treatment then involved heating to a temperature of 190°C at 1.5 K / min, holding for 15 minutes, and cooling again. The dried solid was milled to a D in a counter-jet mill with nitrogen. v (97) value (determined according to the determination method described above), de-agglomerated to the grain size given in Table 1.

[0269] Table 1

[0270] 1 = surface-available acidic hydroxy groups

[0271] Production of various rubber compositions (stage 1)

[0272] In a Haake Rheomix 3000 S mixer equipped with Banbury rotors from ThermoFischer, rubber compositions (base mixtures; masterbatches) with the components and quantities specified in Table 2 were prepared as follows.

[0273] Before mixing began, the mixing chamber was heated to 40 °C. The quantities of the components were calculated to ensure a 70% filling level of the mixing chamber. All components were pre-weighed on a Kern scale. After the rotors started (50 rpm), the mixing chamber was filled with rubber, the filling device to the mixing chamber was pneumatically locked, and mixing was continued for a total mixing time of 1 minute. The filling device of the mixing chamber was then opened, 1 / 3 of the filler quantity and additives (0.15 phr MgO; 4 phr Escorez 1102) were added, the mixing chamber was closed again, and mixing was continued for a total mixing time of 2 minutes. The filling device of the mixing chamber was then opened, 1 / 6 of the filler quantity was added, followed by the oil quantity, followed by 1 / 6 of the filler quantity, the mixing chamber was closed again, and mixing was continued for a total mixing time of 4 minutes.The mixing chamber's filling device was then opened, 1 / 6 of the filler quantity was added, followed by the oil quantity, followed by 1 / 6 of the filler quantity. The mixing chamber was closed again, and mixing continued for a total mixing time of 6 minutes. After 8 minutes of total mixing time, the chamber was vented. The discharge temperature was controlled by adjusting the speed. After 10 minutes of total mixing time, the mixture was discharged, and the temperature of the mixture was measured.

[0274] After the mixing process, the mixture was removed from the mixer and cooled and homogenized on a laboratory roller mill at a medium roller gap. To do this, the mixture was first passed through the roller gap once, the resulting mixture sheet was rolled into a "doll" and tumbled upside down through the roller gap six times. The sheet was then placed on a cooling table to cool until it reached room temperature.

[0275] Table 2

[0276] 1 Bromobutyl rubber X Butyl BB 2230 from Arlanxeo

[0277] 2 Carbon black N660 from Lehmann and Voss

[0278] 3 Paraffin oil from Hansen and Rosenthal Tudalen 1927

[0279] # highest temperature reached during mixing (“dumping temperature”)

[0280] Comparative Example C1 differs from inventive Example B1 in that carbon black N660 was used in this example. Comparative Example C2 used the maximum amount of F1A in phr that would be permissible for HTT lignin according to the teaching of WO 2020 / 202125 A1.

[0281] Production of vulcanizable rubber compositions (stage 2)

[0282] The vulcanizable "green compounds" of examples V1, V2, and B1 were produced for each of the rubber compositions by admixing a vulcanization system consisting of 1 phr zinc oxide, 0.5 phr sulfur, and 1.9 phr mercaptobenzothiazyl disulfide (80% strength; contains 20 wt.% binder and dispersant). In comparative example V1, the zinc oxide was added in stage 1. First, the cooled compound sheet was cut into strips, and the vulcanization chemicals were weighed. After the rotors were started (50 rpm) at a mixing chamber temperature of 40 °C, the sheet was fed into the mixing chamber, the filling device to the mixing chamber was pneumatically locked, and mixing was carried out for a total mixing time of 2 minutes. The filling device to the mixing chamber was then opened, vulcanization chemicals were added, the filling device to the mixing chamber was pneumatically locked, and mixing was continued for a total mixing time of 5 minutes.The discharge temperature was controlled by adjusting the speed. After 5 minutes of total mixing time, the mixture was discharged and the temperature of the mixture was measured.

[0283] After the mixing process, the mixture was removed from the mixer and cooled and homogenized on a laboratory roller mill at a medium roller gap. To do this, the mixture was first passed through the roller gap once, the resulting mixture sheet was rolled into a "doll" and tumbled upside down through the roller gap six times. The sheet was then placed on a cooling table to cool until it reached room temperature.

[0284] This resulted in the vulcanizable rubber compositions V1 g and V2 g and B1 g , where “g” stands for “Green Compound” and the remaining designation corresponds to the examples V1, V2 and B1.

[0285] Production of vulcanized rubber compositions

[0286] From the vulcanizable rubber compositions V1 g , V2 g and B1 g Test specimens V1 were vulcanized by vulcanization at 160 °C in vulcanizing presses v , V2 v and B1 v , corresponding to the vulcanizable Green Compounds V1 g , V2 g and B1 gThe compound sheet was rolled out wrinkle-free to a thickness of 3 mm by successively reducing the gap width of the laboratory roller. A square measuring 250 x 250 mm was then cut from this sheet using scissors and transferred to the press (Gibitre Instruments SRL vulcanization press with a built-in mold for 2 mm thick test sheets). The vulcanization time to be set is determined from the t90 time determined in the rheometer test, plus one minute per millimeter of sheet thickness (i.e., plus two when using the 2 mm frame). The vulcanized rubber sheet was removed immediately after the pressing time. The sheet was placed on the cooling table to cool. After cooling, the excess edge was carefully trimmed off with scissors.

[0287] Other rubber compositions containing filler F1B

[0288] The vulcanizable rubber compositions listed in Table 3 were prepared in the same manner as described above. In contrast to Table 2, Table 3 lists the rubber compositions including the components added in stage 2 and their amounts (i.e., as "green compounds").

[0289] Table 3

[0290] The examples V3 g , V4 g and B2 g correspond to examples V1 g , V2 g and B1 g (i.e., the "Green Compounds" of examples V1, V2, and B1) with the difference that filler F1B was used instead of filler F1A. F1B has a slightly lower multipoint BET surface area and a slightly lower STSA surface area (see Table 1).

[0291] In the examples V5 g , V6 g and B3 gPart of the filler F1 B was replaced by carbon blacks with different BET or STSA surface areas. The ratio of FB1 to carbon black is 40:10. In Examples V7 g and B4 g Part of the filler F1 B was replaced with carbon blacks with different BET and STSA surface areas. The ratio of FB1 to carbon black is 40:15. The process oil content was also slightly increased.

[0292] Other rubber compositions containing filler F1C

[0293] The vulcanizable rubber compositions listed in Table 4 were prepared in the same manner as described above. The presentation in Table 4 is analogous to that in Table 3.

[0294] Table 4 The above examples in Table 4 demonstrate that blends of bromobutyl rubber (X Butyl BB 2030) or chlorobutyl rubber (X Butyl CB 1240) with natural rubber (SMR CV) can also be produced using the filler F1 C. Due to the advantages of using F1 fillers in bromobutyl rubber with regard to reducing gas permeability, as outlined in the results section, it is possible to replace part of the bromobutyl rubber with natural rubber while maintaining sufficiently good gas permeability. Although natural rubber is somewhat more gas-permeable, it has the advantage of being a product of biological origin. By increasing the proportion of F1c, the advantages associated with the filler F1 can also be improved. The crosslinking chemicals were adapted to be suitable for blending with natural rubber.

[0295] Test results

[0296] Table 5 shows the test results for the reaction kinetics / vulcanization kinetics of the vulcanizable rubber compositions V1 g , V2 g and B1 g (Use of filler F1A) or V3 g , V4 g and B2 g (Use of filler F1 B).

[0297] Table 5

[0298] As can be seen from Table 5, the data for the reference blends with carbon black N660 V1g and V3g are within a tolerable range. However, significant deviations are evident in the reaction kinetics for V4g and B2g. The literature on BIIR crosslinking using ZnO notes that water acts as a strong retarder. The HTT lignin used reaches equilibrium at a water absorption of approximately 2.5%. This is significantly higher than the water absorbed by carbon black N660. The influences of reaction kinetics were taken into account during vulcanization by vulcanizing the test specimens of the respective blends using the time determined for T90.

[0299] Table 6 shows the measured values ​​obtained on the vulcanized test specimens for the comparative examples V1 v , V2 v and the inventive example B1 v .

[0300] Table 6

[0301] As can be seen from Table 6, the use of HTT lignin improves gas permeability even at the same volume dosage (taking into account the low density of the filler). A slight increase in the volumetric filler ratio, as in B1v, leads to an improvement in gas permeability of approximately 25%. The reinforcement index M300 / M100 is also improved in B1v. The tensile strength and elongation at break values ​​are within an acceptable range for the compound's application in inner liners.

[0302] Table 7 shows the measured values ​​obtained on the vulcanized test specimens for the comparative examples V3 v , V4 v and the inventive example B2 V .

[0303] Table 7

[0304] As can be seen from Table 7, the density is lower when using HTT lignin in compounds V4v and B2v. The reinforcement properties up to 300% elongation are superior to those of the carbon black reference, which is also clearly reflected in the reinforcement index M300 / M100. It is also important to note that the mean molecular network length Mc, determined by toluene swelling and using the Flory-Huggins constant (0.35), is somewhat lower. Despite the higher network density and the higher moduli up to 300% deformation, B2v in particular shows improved crack growth inhibition. This is all the more remarkable given that higher forces act at the crack site in this compound with HTT lignin. Table 8

[0305] As can be seen from Table 8, replacing N772 with N326 at both dosages results in a higher torque delta (MH-ML) in the crosslinking kinetics measurement, indicating a higher strengthening effect. ML, however, is little affected at these dosages, indicating good processability for N326.

[0306] Table 9 As can be seen from Table 9, replacing carbon black N772 with carbon black N326 shows an increase in stress values ​​(modulus 100-300), tensile strength, elongation at break, and hardness. What is particularly surprising, however, is that despite these higher stress values, an improvement in crack growth was achieved.

Claims

PATENT CLAIMS Rubber composition comprising a rubber component comprising at least one halobutyl rubber selected from the group consisting of bromobutyl rubber and chlorobutyl rubber, and a filler component comprising one or more fillers F1 comprising a 14 possess a carbon content in the range of 0.20 to 0.45 Bq / g carbon; possess a carbon content in the range of 60 wt.% to 85 wt.% based on the ash-free and anhydrous filler; exhibit acidic hydroxyl groups on their surfaces; wherein the weighted arithmetic mean of the STSA surface areas of the fillers F1 is in the range of 40 m 2 / g up to 80 m 2 / g lies; the fillers F1 a volume-based median of the particle size distribution D v (50) in the range of 0.5 pm to 5 pm and a volume-based D v(97)-value in the range of 3 pm to 23 pm; and i. the filler component contains more than 45 phr of fillers F1; or ii. the filler component contains more than 25 phr of fillers F1 and additionally contains one or more industrial carbon blacks F2, wherein the weighted arithmetic mean of the STSA surface areas of the industrial carbon blacks F2 is in the range of 55 m 2 / g up to 95 m 2 / g; wherein the proportion of halobutyl rubber in the rubber composition is 60 to 100 phr. Rubber composition according to claim 1, characterized in that the STSA surface area of ​​each filler F1 is in the range of 40 m 2 / g up to 80 m 2 / g lies and the STSA surface area of ​​each industrial carbon black F2 is in the range of 55 m 2 / g up to 95 m 2 / g lies. A rubber composition according to claim 1 or 2, characterized in that the rubber composition contains one or more further components selected from the group consisting of i. rubbers other than halobutyl rubbers, ii. fillers F3 other than filler F1 and filler F2, iii. plasticizers, iv. resins that increase adhesion, and v. vulcanization-promoting additives. A rubber composition according to claim 3, characterized in that i. the rubbers other than halobutyl rubbers are selected from the group consisting of natural rubber, butyl rubber, and styrene-butadiene rubber, and / or ii. the fillers F3 other than filler F1 and filler F2 are selected from the group consisting of carbon blacks and layered silicates, and / or iii. The plasticizers are selected from the group consisting of esters of aliphatic dicarboxylic acids, paraffinic oils and naphthenic oils, and / or iv.the resins that increase adhesion are selected from the group of aliphatic hydrocarbon resins, aromatic hydrocarbon resins, phenolic resins, phenol-formaldehyde resins and phenol-acetylene resins; and / or the vulcanization-promoting additives are selected from the group of saturated fatty acids with 12 to 24 carbon atoms and thiazoles. A rubber composition according to one of claims 3 or 4, characterized in that i. the rubbers other than halobutyl rubbers are contained in the rubber composition in an amount of 0 to 40 phr, and / or ii. the fillers F3 other than fillers F1 and carbon blacks F2 are contained in the rubber composition in an amount of 0 to 40 phr, and / or iii. the plasticizers are contained in the rubber composition in an amount of 0 to 20 phr, and / or iv. the adhesion-enhancing resins are contained in the rubber composition in an amount of 0 to 15 phr; and / or v. the vulcanization-promoting additives are contained in the rubber composition in an amount of 0 to 5 phr. Rubber composition according to one or more of the preceding claims, wherein the filler F1 is a lignin-based filler, preferably a hydrothermally treated lignin.A rubber composition according to one or more of the preceding claims, wherein the filler(s) F1 is present in a proportion of 50 to 100 wt.% relative to the total of fillers F1 and F2, and / or the proportion of the total of fillers F1 and F2 is at least 46 phr. A rubber composition according to one of the preceding claims, wherein the amount of surface-available acidic hydroxyl groups of filler F1, according to Sipponen, is in the range of 0.05 mmol / g to 5 mmol / g. A vulcanizable rubber composition comprising a rubber composition according to one or more of claims 1 to 8 and a vulcanization system comprising zinc oxide and / or sulfur. A vulcanizable rubber composition according to claim 9, characterized in that the vulcanization system is selected from the group consisting of the following vulcanization systems comprising: a. zinc oxide and at least one saturated fatty acid with 12 to 24 carbon atoms; b. at least one thiuram and / or dithiocarbamate, and preferably no sulfur; c. at least one alkylphenol disulfide; d. at least one polymethylolphenol resin or a halogenated polymethylolphenol resin, and preferably no sulfur and no sulfur-containing compounds; e. sulfur and at least one thiazole and / or sulfenamide; f. sulfur, at least one thiazole and / or sulfenamide, and at least one saturated fatty acid with 12 to 24 carbon atoms.A kit-of-parts comprising, in spatially separate form, a rubber composition (A) according to one or more of claims 1 to 8 and a vulcanization system (B) as defined in claims 9 or 10. A method for producing a rubber composition as defined in one or more of claims 1 to 8, characterized in that the rubber component is provided and the filler component, as well as optionally plasticizers, adhesion-enhancing resins, and vulcanization-promoting additives, are incorporated therein. A method for producing a vulcanizable rubber composition according to claim 9 or 10, characterized in that, in a first stage, a rubber composition is produced according to the method of claim 12, and subsequently, in a second stage, the components of the vulcanization system are added. A method for further processing the vulcanizable rubber compositions according to the invention as defined in claims 9 and 10, characterized in that they are formed into a sheet by calendering, extrusion, or roller-head forming. A method according to claim 14, characterized in that the sheet has a thickness in the range of 0.3 to 5 mm.A method for manufacturing a pneumatic tire comprising the method of claim 14 or 15, followed by a step of cutting the resulting web to form an inner liner of a pneumatic tire, and comprising the subsequent step of vulcanizing the inner liner thus obtained together with the carcass of a pneumatic tire. The use of one or more fillers F1, optionally in a mixture with one or more carbon blacks F2, wherein these are defined as in any one of claims 1, 6, 7, or 8, in rubber compositions for inner liners, wherein the fillers F1 and carbon blacks F2 are used in a total amount of at least 46 phr. A vulcanized rubber composition obtainable by vulcanizing a vulcanizable rubber composition according to any one of claims 9 or 10. A vulcanized rubber composition according to claim 18, characterized in that it... (a) a Shore A hardness in the range of 35 to 65; and / or (b) a module 300 from 2.8 MPa to 8 MPa; and / or (c) a density of 1,000 g / cm³ 3 up to 1,120 g / cm³ 3 ; and / or (d) a gas permeability of less than 3.8 x 10' 17 m 2 / Pas possesses. Vulcanized rubber composition according to claim 18 or 19, wherein it is the inner liner of a pneumatic tire.

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