Vulcanisable rubber blend and rubber product that can be produced from same

Abstract

The invention relates to a vulcanisable rubber blend comprising: i) one or more diene rubbers, ii) one or more fillers in a combined mass fraction of 55 phr or more, and iii) one or more rubber regenerates, wherein the one or more rubber regenerates are produced by devulcanisation of a rubber material blend in an extruder, wherein 50% or more of the rubber material blend consists of comminuted treads of radial tyres of lorries and / or buses, in relation to the mass of the rubber material blend.

Description

[0001] Vulcanizable rubber compound and product producible therefrom

[0002] rubber product

[0003] Description

[0004] The invention relates to a vulcanizable rubber mixture, a vulcanizate producible from this vulcanizable rubber mixture, and a rubber product comprising a corresponding vulcanizate, as well as processes for producing the corresponding vulcanizable rubber mixtures and vulcanizates. The invention also discloses the use of specific regenerated rubber materials in vulcanizable rubber mixtures.

[0005] In almost all areas of technology, there is a strong desire today to reduce dependence on fossil fuels and minimize greenhouse gas emissions. In the process of making production processes more sustainable, the recycling of old, no longer needed products is becoming increasingly important. These so-called secondary raw materials can already be used in many areas of technology to reduce the materials used in production, thereby improving the sustainability of production and the resulting products.

[0006] The tire industry is also striving to at least partially replace the components required for the production of modern vehicle tires with recycled materials. One class of materials that is particularly important for the production of vehicle tires and whose replacement with recycled secondary raw materials could potentially have a particularly beneficial impact on the sustainability of the products is the rubber required for rubber production. It is known from the state of the art that rubber materials from old conveyor belts or scrap tires can be processed to be used as an additive in vulcanizable rubber compounds, which can then be molded and vulcanized into the desired rubber products during tire production.

[0007] These so-called reclaimed rubber materials can in principle be produced in a variety of ways. In particular, processed materials are known from the state of the art which are still rubber materials in the narrower sense, i.e. cross-linked rubber, but whose plasticity is adjusted to the plasticity of unvulcanised rubber by means of suitable treatment processes, in particular using thermal and chemical stress and chemicals. In addition, there are also reclaimed rubber materials in which devulcanisation, i.e. the breaking of chemical bonds in the rubber material, occurs at least partially and in which the depolymerisation of the previously cross-linked rubber material contributes to an increase in plasticity. More detailed background information on the various technologies and the general technological background can be found, for example, in JK Kim et al., „Rubber Recycling: Challenges and Developments“, Green Chemistry Series No. 59, The Royal Society of Chemistry 2019, ISBN: 978-1-78801-084-9, in H. Yazdani et al., „Continuous devulcanization of waste tires by using a Co-rotating twin screw extruder: Effects of screw configuration, temperature profile, and devulcanization agent concentration”, Vinyl and additive Technology, 19, 1 , März 2013, Seiten 65-72, H. Si et al. “Effects of high shear stress on the devulcanization of ground tire rubber in a twin-screw extruder”, Journal of Applied Science, 128, 4, Seiten 2307-2318, sowie der US 20030125401 A1 , der EP 2601249 A1 , der DE 102020207121 A1 und der EP 3 173 162. Various technologies and processes are used to produce rubber reclaims from rubber materials, such as steam regeneration, mechanical regeneration, thermal regeneration, sound wave-based regeneration, radiation-based regeneration, chemical regeneration and combinations of these methods.

[0008] Since these processes for the production of reclaimed rubber are applied to structurally highly complex, disordered and inherently not structurally describable starting materials and induce very different physico-chemical changes in these depending on the processes and process parameters used, the various reclaimed rubbers have very different properties depending on the rubber materials originally used, the chemical composition of which varies particularly depending on the nature of the recycled rubber products, and the method used for devulcanization.

[0009] Similar to essentially all other components of typical vulcanizable rubber compounds, which are selected from a multitude of possible components, such as rubbers, fillers, and plasticizers, in order to optimize the vulcanizable rubber compound and thus the vulcanizate produced from it specifically to the requirements of the intended application of the subsequent rubber product, it is generally not possible to use a generic, uniform reclaimed rubber for all possible applications that would demonstrate good performance properties in all rubber compounds. Rather, it is necessary to specifically tailor the reclaimed rubber to the intended application of the rubber product, taking into account not only the mechanical and / orThe physical and chemical properties of the resulting vulcanizates, in particular the maximum substitutable amount of rubber, should be optimized in order to achieve the most sustainable product possible.

[0010] In practice, it is unfortunately often found that reclaimed rubber tends to degrade tire properties compared to the use of primary rubber raw materials. These performance characteristics often show a strong dependence on the degree of devulcanization achieved. Reclaimed rubber with a high degree of devulcanization often results in vulcanizable rubber compounds that can be converted into vulcanizates with improved properties. However, such comprehensive devulcanization is often associated with increased time and cost and can have a particularly negative impact on the energy required for the conversion and / or require the use of additional chemicals, which can diminish the fundamentally positive environmental impact of using reclaimed rubber.

[0011] When using reclaimed rubber in vulcanizable rubber compounds, particularly in the area of ​​tire production with the multitude of very different requirement profiles prevailing in this field, there is often a conflict of objectives between adding the largest possible amount of reclaimed rubber and at the same time achieving the best possible performance properties, which should preferably not differ from those obtained for vulcanizable rubber compounds made from primary raw materials.

[0012] The inventors' experiments have shown that, in particular, reclaimed rubber produced through chemical devulcanization is of interest for many applications. With corresponding chemically devulcanized reclaimed rubber, particularly advantageous performance indicators for use in vehicle tires were obtained in many cases. However, the problem emerged that these chemically devulcanized reclaimed rubbers, when used in vulcanizable rubber compounds, can surprisingly lead to disadvantageously high viscosities, which impair the processability of the vulcanizable rubber compounds. This is particularly problematic for rubber compounds that have a comparatively high filler content, i.e.This is mostly the case with vulcanizable rubber compounds designed for high stiffness and / or high hardness, such as those frequently used in tire components with protective and / or reinforcing functions. The inherently favorable properties of chemically devulcanized reclaimed rubber are often overlooked in these devulcanized rubber compounds due to excessively limited processability, so that their use cannot usually be achieved in sufficiently large quantities to have the desired positive impact on the sustainability of the products.

[0013] It has been found that the use of alternative reclaimed rubber, such as those obtained from truck tires by thermal-mechanical degradation in an autoclave, can reduce viscosity and thus processability to an acceptable level, even with more heavily filled vulcanizable rubber compounds and higher reclaimed rubber contents. Unfortunately, however, a deterioration in many important performance indicators, especially those associated with rolling resistance, is observed, both compared to the use of primary raw materials and compared to chemically devulcanized reclaimed rubber.In summary, there is a pronounced conflict of objectives between the processability of vulcanizable rubber compounds containing reclaimed rubber, on the one hand, and the rolling resistance properties of the vulcanizates and rubber products produced from these vulcanizable rubber compounds, on the other. This conflict of objectives, which in many cases increases with increasing reclaimed rubber content, is particularly relevant for vulcanizable rubber compounds with higher filler content, which are intended to result in particularly stiff rubber materials.

[0014] The primary object of the present invention was to eliminate or at least reduce the above-described disadvantages of the prior art.

[0015] In particular, the object of the present invention was to provide a vulcanizable rubber mixture with a high filler content that, despite the highest possible proportion of reclaimed rubber, exhibits good processability and, after vulcanization, results in a vulcanizate that exhibits excellent rolling resistance properties when used in vehicle tires. Therefore, the object of the present invention was to optimally resolve the conflicting objectives between the good processability of the vulcanizable rubber mixture and the advantageous rolling resistance of the resulting vulcanizate, even with high proportions of reclaimed rubber.

[0016] In this context, the object of the present invention was to reduce the demand for primary raw materials as much as possible by using the highest possible content of reclaimed rubber, and thus to improve the sustainability of the production of corresponding rubber products as much as possible. In this connection, it was desirable that the sustainability of the production process would also be increased by producing the reclaimed rubber ideally without the use of substances that are potentially harmful to the environment or health, with a supplementary objective being that the production of the reclaimed rubber should be time- and cost-efficient, as well as with the lowest possible energy consumption. It was a further object of the present invention that the vulcanizable rubber mixtures to be specified could be produced in particularly stiff, iehigh-modulus and hard rubber materials should be feasible which, in view of their physical-chemical and mechanical properties, are optimally suited for use in tire components which also have a protective and / or stabilizing function in the vehicle tire, for example in the apex or the rim strips which can, for example, serve as cut protection in the contact area with the rim.

[0017] It was a supplementary object of the present invention to provide a corresponding vulcanizate and a corresponding rubber product which have excellent physico-chemical and mechanical properties, which make them particularly suitable for use in tire components which also have a protective and / or stabilizing function in the vehicle tire, but which are also particularly sustainable due to the high proportion of reclaimed rubber in the underlying vulcanizable rubber mixture.

[0018] Building on the above objects, it was also an object of the present invention to provide a process for producing corresponding vulcanizable rubber mixtures and the associated vulcanizates or rubber products.

[0019] It was a secondary object of the present invention to provide a use for a specifically produced rubber reclaim in the manufacture of rubber products.

[0020] The inventors of the present invention have now found that the objects described above can surprisingly be achieved if a specific rubber reclaim is used in a vulcanizable rubber mixture which, in addition to a diene rubber, comprises a comparatively high proportion of filler, which is predominantly obtained from the treads of radial tires of trucks and buses, and whose devulcanization takes place in an extruder, in particular in a twin-screw extruder, as defined in the claims.Surprisingly, this reclaimed rubber is particularly well suited for use in vulcanizable rubber compounds with a comparatively high filler content and allows sufficient processability even with comparatively large application quantities while simultaneously providing advantageous rolling resistance properties in the vulcanizate produced, so that the conflict of objectives in this regard is resolved particularly advantageously.

[0021] The resulting vulcanizates are more sustainable than comparable vulcanizates made from primary raw materials and are ideal for use in tire components that require high stiffness and / or hardness of the rubber material, such as bead fillers and rim strips.

[0022] The above-mentioned objects are thus achieved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention emerge from the subclaims and the following statements.

[0023] Such embodiments, which are designated as preferred below, are combined in particularly preferred embodiments with features of other embodiments designated as preferred. Combinations of two or more of the embodiments designated as particularly preferred below are thus very particularly preferred. Likewise preferred are embodiments in which a feature of an embodiment designated as preferred to any extent is combined with one or more further features of other embodiments designated as preferred to any extent. Features of preferred vulcanizates, rubber products, processes, and uses emerge from the features of preferred vulcanizable rubber mixtures.

[0024] To the extent that both specific amounts or proportions of an element, for example, for the diene rubber or the reclaimed rubber, and preferred embodiments of the element are disclosed below, the specific amounts or proportions of the preferably configured elements are also disclosed. Furthermore, it is disclosed that, with the corresponding specific total amounts or total proportions of the elements, at least some of the elements can be configured in a preferred manner and, in particular, that preferably configured elements can in turn be present in the specific amounts or proportions within the specific total amounts or total proportions.

[0025] The phr (parts per hundred parts of rubber by weight) used below is the quantity commonly used in the rubber industry for mixture recipes, which indicates the mass fractions of the components in the rubber mixture based on the mass of the high molecular weight (weight average molecular weight distribution Mw according to GPC greater than 60,000 g / mol) rubbers present in the rubber mixture, whereby the combined mass fraction of the high molecular weight rubbers in the rubber mixture corresponds to 100 phr.

[0026] Within the scope of the present invention, reclaimed rubber, which has a complex chemical structure and / or composition, is also used in the vulcanizable rubber mixture. Those skilled in the art will understand that reclaimed rubber, in addition to other components, also comprises devulcanized rubber, the exact mass fraction of rubber in the reclaimed rubber being unknown. In order to prevent the resulting uncertainty from influencing the manufacturability of the vulcanizable rubber mixtures and their reliable production, the reclaimed rubber is not considered as rubber for the calculation of the phr within the scope of the present invention. Accordingly, within the scope of the present invention, the mass fraction of the high molecular weight rubbers used as primary raw material in the rubber mixture, i.e. the rubbers that do not originate from reclaimed rubber, corresponds to 100 phr.This definition advantageously makes it possible to reliably produce vulcanizable rubber compounds despite any residual uncertainties regarding the composition of the reclaimed rubber. For this purpose, the expert weighs the commercially available primary rubber raw materials not obtained by devulcanization and bases the quantities of the remaining components, including the reclaimed rubber, in the recipe on this initial weight.

[0027] The invention particularly relates to a vulcanizable rubber mixture comprising: i) one or more diene rubbers, ii) one or more fillers in a combined mass fraction of 55 phr or more, and iii) one or more rubber reclaims, wherein the one or more rubber reclaims are produced by devulcanization of a rubber material mixture in an extruder, wherein the rubber material mixture consists of 50% or more of shredded treads from truck radial tires and / or bus radial tires, based on the mass of the rubber material mixture.

[0028] The rubber mixture according to the invention is vulcanizable. According to the expert's understanding, this means that the vulcanizable rubber mixture can be converted by vulcanization into a vulcanized rubber mixture, a so-called vulcanizate, in which the rubber is at least partially crosslinked. The vulcanization process and the production of vulcanizates from vulcanizable rubber mixtures are well known to those skilled in the art.

[0029] These above-defined components of the vulcanizable rubber compound are used as "one or more" in accordance with the understanding of the person skilled in the art. The term "one or more" refers, in accordance with industry practice, to the chemical nature of the respective compounds and not to their quantity. For example, the vulcanizable rubber compound may comprise NR and BR as a diene rubber, which would mean that the vulcanizable rubber compound comprises a plurality of the respective molecules.

[0030] In the context of the present invention, the mass fractions are usually given as combined mass fractions of the one or more components, which expresses that the mass fraction of the correspondingly formed components taken together meets the corresponding criteria, wherein the mass fractions are each given in phr, as explained above.

[0031] According to the invention, the vulcanizable rubber mixture comprises at least one diene rubber. Diene rubbers are rubbers produced by polymerization or copolymerization of dienes and / or cycloalkenes and thus contain C=C double bonds either in the main chain or in the side groups.

[0032] According to the inventors' assessment, a vulcanizable rubber mixture according to the invention is preferred, wherein the one or more diene rubbers are selected from the group consisting of natural polyisoprene (NR), synthetic polyisoprene (IR), butadiene rubber (BR), solution-polymerized styrene-butadiene rubber (SSBR), and emulsion-polymerized styrene-butadiene rubber (ESBR), preferably selected from the group consisting of natural polyisoprene and butadiene rubber. It is preferred if the vulcanizable rubber mixture according to the invention comprises at least two different diene rubbers.

[0033] According to the inventors, the advantages of the vulcanizable rubber mixture according to the invention are particularly evident when natural polyisoprene and / or butadiene rubber are used, with the combined use being particularly preferred. Corresponding vulcanizable rubber mixtures are particularly well suited for the production of stiff, high-modulus rubber materials, such as those often desirable for apex rims and rim strips, so the use of the specific rubber reclaims offers advantages, particularly with regard to the processability of these vulcanizable rubber mixtures, which are often difficult to process.

[0034] In this respect, preference is firstly given to a vulcanizable rubber mixture according to the invention, wherein the vulcanizable rubber mixture comprises natural polyisoprene, preferably in a mass fraction of 15 phr or more, preferably of 25 phr or more, particularly preferably of 30 phr or more.

[0035] Natural polyisoprene, also known as natural rubber (NR), is typically a cis-1,4-polyisoprene, with the cis-1,4 content of the natural rubber usually exceeding 99% by weight. For the purposes of the present invention, the term "natural polyisoprene" is understood, in accordance with the expert's understanding, to refer to naturally occurring rubber, which can be obtained, for example, from Hevea rubber trees but also from "non-Hevea" sources. Non-Hevea sources include, for example, Guayule shrubs and dandelions such as TKS (Taraxacum kok-saghyz; Russian dandelion).Additionally or alternatively, a vulcanizable rubber mixture according to the invention is preferred, wherein the vulcanizable rubber mixture comprises butadiene rubber, preferably in a mass fraction of 20 phr or more, preferably 40 phr or more, particularly preferably 60 phr or more, wherein a fraction in the range from 50 to 80 phr, preferably in the range from 55 to 75 phr, particularly preferably in the range from 60 to 70 phr, is very particularly preferred, in particular if the vulcanizable rubber mixture also comprises NR.

[0036] The butadiene rubber (BR, polybutadiene) can be any type of BR known to those skilled in the art. These include, among others, the so-called high-cis and low-cis types, with polybutadiene with a cis content of 90 wt.% or more being referred to as the high-cis type, and polybutadiene with a cis content of less than 90 wt.% being referred to as the low-cis type.

[0037] An example of a low-cis polybutadiene is Li-BR (lithium-catalyzed butadiene rubber) with a cis content of typically 20 to 50 wt.%.

[0038] For certain applications, particularly in vulcanizable rubber compounds intended for use in apex fillers, it may alternatively be advantageous to keep the BR content relatively low or even essentially eliminate the use of BR altogether. In these cases, a vulcanizable rubber compound according to the invention is preferred, wherein the vulcanizable rubber compound comprises 20 phr or less, preferably 10 phr or less, more preferably 5 phr or less, most preferably 1 phr or less, and most preferably essentially no butadiene rubber.

[0039] In the inventors' estimation, it may be advantageous for certain applications to adjust the physicochemical properties if the vulcanizable rubber mixture also comprises styrene-butadiene rubber (SBR) as the diene rubber. Based on their own experiments, low contents are preferred in the case of components such as rim tapes. Thus, additionally or alternatively, a vulcanizable rubber mixture according to the invention is preferred, wherein the vulcanizable rubber mixture comprises styrene-butadiene rubber, preferably in a mass fraction of 20 phr or less, preferably 10 phr or less, particularly preferably 5 phr or less, and most particularly preferably 1 phr or less.For use as Apex, however, alternatively vulcanizable rubber mixtures are preferred, wherein the vulcanizable rubber mixture comprises styrene-butadiene rubber in a mass fraction of 30 phr or more, preferably 40 phr or more, particularly preferably 50 phr or more, most particularly preferably 55 phr or more.

[0040] The styrene-butadiene rubber can, for example, be a solution-polymerized styrene-butadiene copolymer (SSBR) with a styrene content, based on the polymer, of approximately 5 to 45 wt.% and a vinyl content (content of 1,2-bonded butadiene, based on the total polymer) of 5 to 70 wt.%, which can be produced, for example, using lithium alkyls in an organic solvent. The SSBR can also be coupled and / or end-group modified and / or backbone modified. The modification may, for example, be hydroxyl groups and / or ethoxy groups and / or epoxy groups and / or siloxane groups and / or amino groups and / or aminosiloxane and / or carboxyl groups and / or phthalocyanine groups and / or alkoxysilyl groups and / or isocyanate groups.

[0041] The advantageous influence of the reclaimed rubber used according to the invention on processability is particularly evident in vulcanizable rubber compounds that intrinsically exhibit poorer processability, particularly as expressed by a high Mooney viscosity, as is particularly the case with particularly filler-rich vulcanizable rubber compounds. Advantageously, the use of the specific reclaimed rubber in these vulcanizable rubber compounds can also improve the sustainability of the producible rubber products, while still maintaining good rolling resistance indicators in the vulcanizate. Accordingly, it is particularly advantageous to apply the teachings of the present inventions to such vulcanizable rubber compounds.Accordingly, a vulcanizable rubber mixture according to the invention is preferred, wherein the vulcanizable rubber mixture comprises the one or more fillers in a combined mass fraction of 60 phr or more, preferably 65 phr or more, particularly preferably 70 phr or more, and / or wherein the vulcanizable rubber mixture comprises the one or more fillers in a combined mass fraction in the range from 55 to 150 phr, preferably in the range from 60 to 120 phr, particularly preferably in the range from 65 to 100 phr. Additionally or alternatively, a vulcanizable rubber mixture according to the invention is preferred, wherein the vulcanizable rubber mixture has a Mooney viscosity ML (1 + 4 / 100°C) in the range from 40 to 100 MU, preferably in the range from 50 to 90 MU, particularly preferably in the range from 55 to 85 MU, determined according to ASTM D1646 from November 2019.

[0042] In the inventors' opinion, in principle, all fillers commonly used in rubber processing are suitable as fillers. An example of this is a vulcanizable rubber mixture according to the invention, wherein the one or more fillers are selected from the group consisting of polar and non-polar fillers, preferably selected from the group consisting of carbon black, aluminum hydroxide, titanium dioxide, magnesium oxide, amorphous silicon dioxide, and phyllosilicates, particularly preferably selected from the group consisting of carbon black and amorphous silicon dioxide, in particular pyrogenic and / or precipitated silicon dioxide. The use of carbon black and / or precipitated silicon dioxide, also referred to as silica, is particularly preferred.

[0043] The amorphous silicon dioxide can, in particular, be materials known to those skilled in the art as "silicas," which are suitable as fillers for tire rubber compounds. However, it is particularly preferred to use a finely divided, precipitated silica with a nitrogen surface area (BET surface area) (according to DIN ISO 9277:2010 and DIN 66132:1975) in the range of 35 to 400 m². 2 / g, preferably in the range of 35 to 350 m 2 / g, particularly preferably in the range of 85 to 320 m 2 / g and most preferably in the range of 120 to 235 m 2 / g.

[0044] However, in the inventors' opinion, the advantages of the invention are particularly pronounced when a large proportion of carbon black is provided in the vulcanizable rubber mixture, as is often the case in particular in vulcanizable rubber mixtures intended for the production of rigid and / or hard rubber materials used in bead fillers, rim strips and / or other components with a protective and / or reinforcing function. Therefore, a vulcanizable rubber mixture according to the invention is preferred, wherein the vulcanizable rubber mixture comprises carbon black as filler, preferably in a mass fraction of 45 phr or more, preferably 55 phr or more, particularly preferably 65 phr or more, wherein the mass fraction is preferably in a range from 50 to 150 phr, particularly preferably from 60 to 120 phr, particularly preferably from 70 to 100 phr.

[0045] In principle, all types of carbon black known to those skilled in the art are conceivable as carbon black. However, the use of carbon blacks with a high surface area (BET) is particularly preferred, as these generally exhibit a particularly pronounced reinforcing effect. According to ASTM Standard Classification D1765-13, such carbon blacks have a group number in the range from 0 to 5, preferably in the range from 1 to 5, particularly preferably in the range from 2 to 5, which is indicated directly after the letter, so that, for example, N219 has a group number of 2.

[0046] The vulcanizable rubber mixture according to the invention comprises one or more specific rubber reclaims, but can in principle also comprise other rubber reclaims. These specific rubber reclaims can be produced or are produced by devulcanizing a rubber material mixture in an extruder. In accordance with the expert's understanding, devulcanization refers to the process of splitting the sulfur bridges in a rubber material, by which the rubber material mixture is converted from the elastic to the plastic state in order to obtain the reclaimed rubber. The person skilled in the art understands that devulcanization does not have to be complete; in practice, from a time and / or cost perspective, partial devulcanization will probably be sufficient in most cases to achieve the desired plasticity.

[0047] The specific production of the reclaimed rubber and the precise matching with the rest of the rubber mixture advantageously makes it possible to use relatively high contents of reclaimed rubber, which is preferred from a sustainability perspective, since primary raw materials can be saved. Against this background, a vulcanizable rubber mixture according to the invention is preferred, wherein the vulcanizable rubber mixture comprises the one or more reclaimed rubbers in a combined mass fraction of 5 phr or more, preferably 10 phr or more, particularly preferably 20 phr or more, very particularly preferably 30 phr or more, and / or wherein the vulcanizable rubber mixture comprises the one or more reclaimed rubbers in a combined mass fraction in the range from 5 to 60 phr or more, preferably in the range from 10 to 50 phr, particularly preferably in the range from 15 to 40 phr.

[0048] According to the inventors' assessment, particularly advantageous reclaimed rubber for use in vulcanizable rubber mixtures according to the invention are obtained when devulcanization takes place in an extruder in which two or more extruder screws exert shear forces on the rubber material mixture. The use of a twin-screw extruder is particularly preferred for essentially all embodiments, and the use of a sieve for filtering the resulting reclaimed rubber can also contribute to particularly advantageous properties. Therefore, a vulcanizable rubber mixture according to the invention is preferred, wherein the extruder is a multi-screw extruder, in particular a twin-screw extruder.Additionally or alternatively, a vulcanizable rubber mixture according to the invention is preferred, wherein the one or more rubber regenerates are produced by devulcanization of a rubber material mixture in an extruder and subsequent filtering of the extrudate, preferably by means of a sieve and / or a perforated plate.

[0049] The person skilled in the art understands that the above definition means that the one or more rubber regenerates are produced by, preferably thermal-mechanical, devulcanization of a rubber material mixture in an extruder.

[0050] As explained above, rubber materials used in different rubber products generally have very different physical-chemical and mechanical properties, which can be attributed in particular to the chemical composition of the vulcanizable rubber compounds used in their production. Accordingly, rubber materials behave differently during devulcanization and result in chemically different rubber reclaims. In practice, the choice of starting material is therefore of crucial importance.In the present case, the inventors have found that rubber materials from the treads of radial tires for trucks and buses, which are characterized by an application-typical property profile, have a particularly high compatibility with the process used for devulcanization and that the resulting rubber reclaims are particularly suitable for use in vulcanizable rubber compounds with high filler contents.

[0051] The term "radial tire" is clear to the expert and allows for precise identification of corresponding vehicle tires based on the carcass structure. Determining whether a tire is a truck radial tire and / or a bus radial tire (so-called commercial vehicle tires, also known as CVT tires) poses no challenges in practice for the tire expert. A truck radial tire and / or a bus radial tire can be easily identified by the expert based on its dimensions (larger and wider than passenger car tires) and the tire carcass structure, which is designed for significantly higher load capacities than passenger car tires, for example, load capacities of 2000 kg or more, preferably 3000 kg or more.In practice, however, this is usually not even necessary, since the corresponding commercial vehicle tires can usually be identified as such by appropriate markings on the vehicle tire or by the manufacturer's type designation. A vulcanizable rubber mixture according to the invention is particularly preferred, wherein the rubber material mixture comprises shredded treads from radial truck tires.

[0052] The person skilled in the art understands that, with a view to the most sustainable production possible, a vulcanizable rubber mixture according to the invention is particularly in focus, wherein the rubber material mixture consists of 50% or more of shredded treads from recycled, truck radial tires and / or recycled bus radial tires, ie from previously used and correspondingly at least partially worn-out truck radial tires or bus radial tires.

[0053] In the inventors' opinion, the rubber mixture should advantageously contain the highest possible proportion of such commercial vehicle tires so that the advantages of the invention are particularly evident. Therefore, a vulcanizable rubber mixture according to the invention is preferred, wherein the rubber mixture consists of 70% or more, preferably 80% or more, particularly preferably 90% or more, and most particularly preferably essentially 100%, of shredded treads from truck radial tires and / or bus radial tires, based on the mass of the rubber mixture.

[0054] Preference is given to a vulcanizable rubber mixture according to the invention, wherein the one or more rubber regenerates have an average particle size in the range from 75 pm to 5 mm, preferably in the range from 100 pm to 2 mm and particularly preferably in the range from 115 pm to 1000 pm.

[0055] The devulcanization of the specific rubber material mixture for producing the rubber regenerates can be carried out, for example, using extruder-based processes known from the prior art, as disclosed, for example, in DE 102020207121 A1, EP 3173162 A1 or US 20030125401 A1.

[0056] In principle, a vulcanizable rubber mixture according to the invention is preferred, wherein the one or more rubber regenerates are produced by devulcanization at a temperature in the range of 150 to 350 °C, preferably in the range of 200 to 300 °C, particularly preferably in the range of 220 to 280 °C. The vulcanization of the vulcanizable rubber mixture according to the invention results in a vulcanizate which can be used as a semi-finished product in the manufacture of rubber products, or which itself already represents a rubber product or part of a rubber product.

[0057] The vulcanization of the rubber mixture is preferably carried out in the presence of sulfur and / or sulfur donors with the aid of vulcanization accelerators, whereby some vulcanization accelerators can also act as sulfur donors. For this purpose, the vulcanizable rubber mixture preferably already comprises the so-called vulcanization system. Accordingly, a vulcanizable rubber mixture according to the invention is preferred, wherein the vulcanizable rubber mixture comprises 0.5 to 8.0 phr, preferably 0.5 to 5 phr, particularly preferably 1.0 to 3 phr, of sulfur, whereby the vulcanizable rubber mixture preferably comprises one or more vulcanization accelerators.The vulcanization accelerator is, for example, selected from the group consisting of thiazole accelerators, mercapto accelerators, sulfenamide accelerators, thiocarbamate accelerators, thiuram accelerators, thiophosphate accelerators, thiourea accelerators, xanthate accelerators and guanidine accelerators.

[0058] Furthermore, the vulcanizable rubber mixture may contain other conventional additives in conventional parts by weight. An example of a vulcanizable rubber mixture according to the invention is one in which the vulcanizable rubber mixture comprises one or more additives, for example stearic acid and / or N-(cyclohexylthio)phthalimide, which are preferably selected from the group consisting of anti-aging agents, reinforcing resins, coupling agents, adhesion promoters, and plasticizers, preferably in a combined mass fraction in the range of 5 to 50 phr, preferably in the range of 10 to 40 phr, particularly preferably in the range of 20 to 30 phr. These components and possible substances for the respective purposes are comprehensively known to the person skilled in the art and are comprehensively disclosed in the prior art.

[0059] In accordance with expert understanding and standard practice in the field of technology, it is expedient to define polymeric and oligomeric compounds such as the vulcanizates or rubber products that can be produced by means of the manufacturing process or the starting materials used for production, since it is impossible to meaningfully define the corresponding materials otherwise.

[0060] The invention accordingly also relates to a vulcanizate produced or producible by vulcanization of a vulcanizable rubber mixture according to the invention and to a rubber product, in particular a vehicle tire component, preferably a bead filler or a rim strip for vehicle tires, comprising a vulcanizate according to the invention.

[0061] The invention also relates to a process for producing a vulcanizable rubber mixture according to the invention, comprising the process steps: a) producing or providing a rubber material mixture, wherein the rubber material mixture consists of 50% or more of shredded treads from truck radial tires and / or bus radial tires, based on the mass of the rubber material mixture, b) devulcanizing the rubber material mixture in an extruder to obtain a reclaimed rubber, and c) mixing the reclaimed rubber with one or more diene rubbers and one or more fillers to obtain the vulcanizable rubber mixture.

[0062] The production of the vulcanizable rubber compound in process step c) is carried out, for example, according to the process commonly used in the rubber industry, in which a base compound containing all components except the vulcanization system (e.g., sulfur and vulcanization-influencing substances) is first produced in one or more mixing stages. The finished compound is created by adding the vulcanization system in a final mixing stage. The finished compound can be further processed, for example, by extrusion or calendering, and formed into the appropriate shape, preferably into a bead filler or rim strip.

[0063] In light of the above statements, a process according to the invention is preferred, wherein the devulcanization takes place at a temperature in the range from 150 to 350 °C, preferably in the range from 200 to 300 °C, particularly preferably in the range from 220 to 280 °C.

[0064] The invention further relates to a process based thereon for producing a vulcanizate according to the invention and / or a rubber product according to the invention, comprising the process steps of the process according to the invention for producing a vulcanizable rubber mixture according to the invention, and additionally the process step: d) vulcanizing the vulcanizable rubber mixture to obtain the vulcanizate and / or the rubber product.

[0065] Vulcanization can be carried out under the usual conditions which are well known to the person skilled in the art and which the person skilled in the art can easily adapt to the vulcanizable rubber mixtures he uses.

[0066] Also disclosed is the use of a reclaimed rubber in a vulcanizable rubber mixture having a total content of one or more fillers of 55 phr or more, for reducing the rubber requirement and improving the processability in the production of vehicle tires with improved rolling resistance, wherein the reclaimed rubber is produced by devulcanization of a rubber material mixture in an extruder, wherein the rubber material mixture consists of 50% or more of shredded treads from truck radial tires and / or bus radial tires, based on the mass of the rubber material mixture.

[0067] Preferred embodiments of the invention are further explained and described below with reference to experiments.

[0068] Four different rubber reclaims were provided, which were produced from different rubber materials using different methods.

[0069] The reclaimed rubber KR1 was obtained by chemical-mechanical devulcanization in a grinding device from a rubber material mixture consisting essentially of 100% shredded treads from truck radial tires and bus radial tires.

[0070] The rubber reclaim KR2 was obtained by thermal-mechanical devulcanization in a kneading device (t < 30 min; T = approx. 200 °C; and subsequent filtration) from a rubber material mixture that essentially consisted of 100% shredded treads from truck radial tires and bus radial tires.

[0071] The rubber reclaim KR3 was obtained by thermal-mechanical devulcanization in an autoclave (t = 2 - 4 h; T > 200 °C; and subsequent filtration) from a rubber material mixture consisting essentially of 100% shredded, whole truck diagonal tires.

[0072] The reclaimed rubber KR4 was obtained by thermal-mechanical devulcanization in a twin-screw extruder with high shear rates (and subsequent filtration) from a rubber material mixture consisting essentially of 100% shredded treads from truck radial tires and bus radial tires.

[0073] Using these reclaimed rubbers, vulcanizable rubber compounds were produced, the composition of which is listed in Table 1. The vulcanizable rubber compounds were produced according to the process commonly used in the rubber industry under standard conditions in three stages in a tangential mixer or a laboratory mixer. In the first two mixing stages (basic mixing stages), all components except the vulcanization system (sulfur and vulcanization-influencing substances) were mixed. The final mixture was produced by adding the vulcanization system in the third stage (final mixing stage), with mixing taking place at 90 to 120 °C. The general process for producing rubber compounds and their vulcanizates is described, for example, in "Rubber Technology Handbook," W. Hofmann, Hanser Verlag 1994.

[0074] Table 1 - Vulcanizable rubber compounds

[0075] Test specimens were produced from all compounds by vulcanization to t95 (measured on a moving disc rheometer according to ASTM D 5289-12 / ISO 6502) under pressure at 160 °C. For the vulcanizable rubber compounds and these test specimens, typical material properties for the rubber industry were determined using the test methods specified below:

[0076] Mooney viscosity (ML1 +4), according to ASTM D1646 (Mooney units abbreviated “MU”)

[0077] Shore A hardness at room temperature (RT) according to DIN ISO 7619-1:2012-02;

[0078] Rebound resilience at 70 °C according to DIN 53512:2000-04;

[0079] Stress value at 200% strain (modulus 200) at room temperature according to DIN 53504:2017;

[0080] Loss factor tangent delta (tan d max) at 55 °C according to ISO 4664-1:2011; and

[0081] Abrasion at room temperature according to DIN ISO 4649:2021 .

[0082] The material properties of the vulcanizates are summarized in Table 2. Table 2 - Material properties

[0083] The experimental data show that the processability of the inventive rubber compound E1 is improved compared to the comparative sample V1. At the same time, the vulcanizate from the inventive rubber compound E1 yields improved rolling resistance indicators than the comparative samples V2 and V3. In particular, the rebound resilience at 70 °C, the loss factor tangent delta, and the abrasion are improved compared to V2 and V3, whereas the Shore hardness and the 200 modulus are at a comparable level.

[0084] The rolling resistance indicators (rebound resilience at 70 °C and loss factor tangent delta) and abrasion of sample E1 are particularly close to the values ​​of sample V1, which exhibits a favorable performance profile with regard to these properties. In this respect, the experimental data demonstrate that the inventive rubber compound E1 and the vulcanizate obtained therefrom successfully resolve the trade-off between good processability of the vulcanizable rubber compound and favorable rolling resistance of the resulting vulcanizate, even with relatively high proportions of reclaimed rubber.

Claims

Claims 1. Vulcanizable rubber compound comprising: i) one or more diene rubbers, ii) one or more fillers in a combined mass fraction of 55 phr or more, and iii) one or more rubber regenerates, wherein the one or more rubber regenerates are produced by devulcanization of a rubber compound in an extruder, wherein the rubber compound consists of 50% or more of shredded tread strips of truck radial tires and / or bus radial tires, based on the mass of the rubber compound.

2. Vulcanizable rubber compound according to claim 1, wherein the vulcanizable rubber compound comprises butadiene rubber, preferably in a mass fraction of 20 phr or more.

3. Vulcanizable rubber compound according to one of claims 1 or 2, wherein the vulcanizable rubber compound comprises carbon black as a filler, preferably in a mass fraction of 45 phr or more.

4. Vulcanizable rubber compound according to any one of claims 1 to 3, wherein the vulcanizable rubber compound has a Mooney viscosity ML (1 +4 / 100°C) in the range of 40 to 100 MU.

5. Vulcanizable rubber compound according to any one of claims 1 to 4, wherein the extruder is a multi-screw extruder, in particular a twin-screw extruder.

6. Vulcanizable rubber compound according to any one of claims 1 to 5, wherein the rubber compound consists of 70% or more of shredded tread strips from truck radial tires and / or bus radial tires, based on the mass of the Rubber material mixture.

7. Vulcanizate, produced or producible by vulcanization of a vulcanizable rubber compound according to any one of claims 1 to 6.

8. Rubber product, in particular vehicle tire component, preferably a bead liner or a rim strip for vehicle tires, comprising a vulcanizate according to claim 7.

9. A method for producing a vulcanizable rubber compound according to any one of claims 1 to 6, comprising the process steps of: a) producing or providing a rubber compound, wherein the rubber compound consists of 50% or more of shredded tread strips from truck radial tires and / or bus radial tires, based on the mass of the rubber compound; b) devulcanizing the rubber compound in an extruder to obtain a rubber regenerate; and c) Mixing the regenerated rubber with one or more diene rubbers and one or more fillers to obtain the vulcanizable rubber compound.

10. A process for producing a vulcanizate according to claim 7 and / or a rubber product according to claim 8, comprising the process steps of the process according to claim 9, and additionally the process step: d) Vulcanizing the vulcanizable rubber compound to obtain the vulcanizate and / or the rubber product.

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