Method for obtaining natural rubber, rubber composition containing natural rubber and use thereof

Abstract

The present invention relates to a process for obtaining an age resistant natural rubber, a rubber composition comprising the natural rubber obtained thereby and the use of the composition for the production of consumer goods.

Description

TECHNICAL FIELD

[0001] The present invention relates to a process for obtaining an age-resistant natural rubber, a rubber composition comprising the natural rubber obtained thereby and the use of the composition for the production of consumer goods. BACKGROUND

[0002] Many consumer goods in everyday modern life are made from rubber. Here, natural rubber is often superior to synthetically produced rubber with regard to possible stresses and quality. For a long time, natural rubber has been obtained mainly from rubber trees of the genus Hevea, in particular from the Brazilian rubber tree (Hevea brasiliensis), which is a plant species that is mainly cultivated in Asia.

[0003] In recent times, suitable alternatives for obtaining rubber have been sought, in particular with a view to plants that also thrive under Central European climatic conditions. A known suitable alternative for obtaining natural rubber is dandelion (Taraxacum sp.), in particular Russian dandelion (Taraxacum kok-saghyz or Taraxacum kok-saghyz); in addition, a natural rubber very similar to that from the Hevea genus species is also obtainable from guayule (Parthenium argenatatum).

[0004] Natural rubber from the genus Hevea is known to contain, in addition to the rubber polymer, a relatively high proportion of proteins and other cellular components or biomolecules. The components, which come from the original plant, impart good quality and an age-resistant natural stability to the natural rubber, but it is also known that some of these components trigger allergies in humans.

[0005] In the case of synthetic rubber, which generally does not contain proteins and other cellular components, age-stabilizers are usually added and many suitable age-stabilizers are known. Examples of suitable age-stabilizers are described in DE 19818564 A1, US 2010063189 A, US 2011303338 A, EP 3181628 A1, WO 19057703 and EP 3524639 A1.

[0006] Furthermore, US 4,568,711 discloses a synergistic combination of two antioxidants for natural rubber obtained from guayule. SUMMARY

[0007] It is an object of the present invention to provide a process by which age-resistant natural rubber can be produced.

[0008] This object is achieved by the method as claimed in claim 1, the dependent claims specifying preferred embodiments. An elastomeric product with high load bearing capacity, such as a vehicle tire, can be produced from natural rubber obtained in this way.

[0009] The method described herein is a method for obtaining an aging-resistant natural rubber, wherein, in the early stage of obtaining natural rubber from a plant, an aging stabilizer is brought into contact with the obtained plant juice or a component thereof (which has optionally been previously removed and which has optionally been purified) before the natural rubber has (completely) dried, in particular with the natural polyisoprene.

[0010] The method thus comprises a step (I) in which a plant material containing a polymer-containing juice is provided, wherein the juice contains at least natural polyisoprene, in particular cis-1,4-polyisoprene.

[0011] "Plant material" is to be understood as meaning the whole of a plant of the genus described herein, a plurality of plants of the genus described herein, a plurality of plants of different genera described herein, a part of a plant of the genus described herein or a plurality of parts of a plant of the genus described herein, a part of a plant of a plurality of genera described herein (for example roots or leaves from each plant) or a plurality of parts of a plant of a plurality of genera described herein.

[0012] "Juice" is to be understood in accordance with the present specification as meaning any liquid which is present in the plant material or which is exuded from the plant material by mechanical, thermal or chemical treatment, which can be squeezed out, which can be extracted or which can be removed from the solid plant material in some other way. In addition to water, the "juice" always also contains at least one, preferably a plurality of plant-typical components. The juice containing natural polyisoprene as a polymer is used for application in the method according to the application. Elastomeric plant material containing polyisoprene is thus involved.

[0013] According to step (II), the polymer-containing juice or at least its components, in particular natural polyisoprene, is obtained (here also referred to as extracted) from the plant material. The natural rubber contained in the juice can have coagulated in the plant material prior to extraction. The extraction of the juice and / or its components can be carried out in any suitable manner which enables the juice and / or its components, in particular at least the preferred fraction of the components, such as natural polyisoprene, contained in the plant material to exude from the plant material and to be obtained therefrom. The extraction method for obtaining the juice and / or its components, in particular natural polyisoprene, can comprise at least one of the following method steps: comminuting the plant or plant parts, crushing the plant material, destroying the plant material by mechanical, chemical or thermal treatment, pressing the plant material, heating the plant material and / or the juice and / or its components, admixing the plant material / juice and / or its components with an aqueous solution, admixing the plant material with spores of a fungus which decomposes the plant material, in particular Phytophthora infestans, admixing the plant material / juice and / or its components with at least one compound, preferably an organic acid, aerobically or anaerobically fermenting the plant material and / or separating the solid and liquid phases. However, it is preferred that the plant material / juice and / or its components are not admixed with enzymes prior to coagulation of the natural polyisoprene; preferably, no enzymes are added to the preparation during the entire process for obtaining the polyisoprene described here.

[0014] Methods for obtaining the juice and / or its components are known in principle; for example, suitable methods are described in US 2007276112 A, WO 11139382 A2, DE 102013107279 A1, US 2016237254 A, EP 3371229 A1, DE 2017118163 A1, WO 18036825 A1 and WO 18064484 A1.

[0015] The natural polyisoprene can be cis-1,4-polyisoprene or trans-1,4-polyisoprene. The natural rubber is preferably predominantly cis-1,4-polyisoprene, wherein the proportion of cis-1,4 in the natural rubber polymer is typically greater than 99% by weight.

[0016] According to step (III) of the present application, the obtained juice and / or its components, in particular natural polyisoprene, is brought into contact with at least one aging stabilizer. Here, the contact of the juice and / or its components with the aging stabilizer can be achieved by the plant material already being in contact with the aging stabilizer prior to the extraction, for example by placing the plant in an aqueous solution or water containing the aging stabilizer, by moistening the plant with the aging stabilizer in liquid form, or by adding the aging stabilizer as a solid to the plant material prior to the destruction of the plant material. Alternatively, the aging stabilizer can be added in solid, liquid or dissolved form during the destruction of the plant material, for example by mechanically, chemically or thermally treating the plant material. Alternatively, the aging stabilizer can also be brought into contact with the juice and / or its components after they have been exuded from the plant material. It is also possible to add the aging stabilizer to the juice and / or its components later, for example before, during or after method step (IV) described below, or before or during method step (V) described below, but according to the present application, prior to the drying of the natural rubber. Thus, according to the present application, the natural rubber obtained from the plant material has already been in contact with the aging stabilizer prior to the drying and / or at the latest during the drying, i.e. during the incorporation with the aging stabilizer during the drying. It is preferred that the aging stabilizer has already been in contact with the natural rubber prior to the drying. It is particularly preferred according to the method of the present application that the aging stabilizer is brought into contact with the juice and / or its components, in particular with the natural polyisoprene, as early as possible after the plant material has been destroyed, in order to protect the polymers contained in the juice as effectively as possible from atmospheric oxygen and other environmental conditions outside the plant material.

[0017] Step (IV) of the method comprises coagulating and / or condensing the polymers contained in the juice, in particular natural polyisoprene. Here, the coagulation or condensation can be achieved by any coagulation or condensation method known in the art, in particular by any known coagulation or condensation method for rubber. It is preferred that the coagulation / condensation of the polyisoprene takes place in an aqueous solution. It is also possible that the coagulation / condensation can already take place in the juice which is still present in the plant material, for example if the plant material is being stored or heat treated, for example by boiling. The coagulation or condensation of the polymers can also take place during the treatment of the plant material to extract the juice and / or its components, for example by heating to destroy the plant material or heating the exuded juice, so that step (IV) does not require a separate addition of substances and / or does not require a separate additional procedure. Without being limited thereto, suitable methods for coagulating / condensing the polymers are, for example, heating the plant material / juice, adding ions, adding organic solvents, etc.

[0018] Due to coagulation or condensation of the polymer, the initially previously dissolved and / or emulsified polymer chains in the juice become solid and can be removed from the (preferably aqueous) mixture. Preferably, according to the present application, the polyisoprene is coagulated by storing or heating the plant material / juice, preferably until boiling in water or an aqueous solution. Upon heating, the polyisoprene contained in the juice flocculates and the resulting natural rubber flakes can be removed from the plant material and other components of the juice. Without being limited to the mentioned methods, any suitable separation method can be used for removing the rubber flakes, such as skimming, sieving, filtering, milling, draining the liquid phase, centrifugation, etc.

[0019] The natural rubber flakes obtained in this way can be washed according to step (V) with one or more intermediate steps in order to additionally purify the obtained natural rubber to remove further components of the plant material. To this end, the obtained natural rubber flakes can be contacted with, e.g. transferred into, clean water or an aqueous solution. According to the present application, step (III), i.e. the addition of the aging stabilizer, can also take place before, during or after such washing steps, e.g. by adding the aging stabilizer to the water / aqueous solution with which the natural rubber flakes are contacted in one or more washing steps. Preferably, the rubber flakes are slurried, or suspended or dispersed in the water / aqueous solution, e.g. by stirring or shaking or by rotating in a rotating drum.

[0020] In step (VI) of the method, the coagulated or condensed natural rubber particles (flakes) are obtained from the aqueous mixture / suspension or dispersion. At this point, “obtained” means that no additional washing or purification steps follow the removal of the natural rubber flakes from the liquid phase. Also here, the present application is not limited to a specific method of removing the solid particles from the aqueous mixture / suspension or dispersion; rather, any suitable separation method can be used, such as skimming, sieving, filtering, draining the liquid phase, centrifugation, etc.

[0021] Since the natural rubber particles (flakes) are removed from the liquid phase of the aqueous mixture / suspension or dispersion according to steps (V) and (VI), they are at least partially, preferably largely, removed from other components of the plant material, so that the obtained natural rubber contains only up to a maximum of 30% by weight, preferably up to a maximum of 25% by weight, further preferably up to a maximum of 20% by weight, yet further preferably up to a maximum of 15% by weight of other components of the plant material, in particular of the juice. It is to be noted here that the components of the original juice can be depleted to different extents, for example the inulin, which is present in the original juice in large proportions, is preferably substantially removed (washed off) from the natural rubber flakes, whereas proteins, for example, can also flocculate to some extent during the heating process and can likewise be removed from the aqueous solution when obtaining the rubber flakes. It is absolutely preferred that the obtained natural rubber has at least a certain content of other natural components derived from the plant material, such as oligomeric isoprene, lipids and proteins, in addition to the natural polyisoprene.

[0022] The natural rubber obtained from the mixture, suspension or dispersion is optionally dried by a suitable method for further processing. Suitable methods for drying the natural rubber are known in the art and are not limited thereto, and can include air and / or heat treatment. According to the method of the present application, the aging stabilizer has been contacted with the natural rubber at the latest during drying, preferably even before this step.

[0023] If the aging stabilizer is still not sufficiently distributed or incorporated into the obtained natural rubber during or after the above-mentioned method steps, this can be achieved by further incorporating the aging stabilizer into the natural rubber during the method, in particular before, during or after step (IV), during or after the (at least one) washing step according to step (V), or after step (VI) or after drying the rubber, for example by stirring, kneading, grinding, by diffusion in a suspension of the natural rubber and the aging stabilizer in water or another suitable method. Said “further incorporation” does not mean adding / contacting the aging stabilizer, but rather uniform distribution and incorporation of the agent in the natural rubber material. As already mentioned above, the contact of the aging stabilizer with the juice / its components always takes place before the (complete) drying of the natural rubber. The temperature during the contact of the aging stabilizer with the natural rubber is preferably chosen in the range from -25°C to 100°C, preferably in the range from 0°C to 90°C, particularly preferably from 10°C to 80°C. The time should be at least 10 min, preferably at least 30 min, further preferably at least 1 hour, and if necessary, can be prolonged to a suitable period of time as required; for example, the contact can be between 1 hour and 7 days, preferably 2 hours to 3 days, further preferably from 4 hours to 36 hours, yet further preferably from 4 to 10 hours, in order to ensure the effective activity of the aging stabilizer even before the (complete) drying of the natural rubber.

[0024] The above reference to method steps occurring or possibly occurring in the process according to the application describes the inventive process according to the application. However, it is noted here that some of the method steps can be carried out simultaneously or coincidentally, individual steps can be repeated, and these steps do not necessarily have to be carried out in the order specified. However, it is preferred according to the application that steps (I) to (VI) are each carried out before drying the natural rubber according to step (VII). In a preferred embodiment of the process, at least some, preferably all, of the steps described in the claims or above as optional are likewise carried out. It is particularly preferred that one or more washing steps (V) of the process are carried out. In a preferred embodiment in which washing is carried out, at least some of the age stabilizer to be incorporated into the natural rubber is added to the water used to wash the natural rubber flakes during at least one of these washing steps. The drying step (VII) is also preferably carried out as a separate method step.

[0025] The incorporation of the age stabilizer according to step (VIII) is likewise preferably carried out, such incorporation is possible before drying the natural rubber, during drying thereof or after, or before and during / after drying the natural rubber. Thus, the incorporation of the age stabilizer into the natural rubber can still be carried out in the aqueous mixture / suspension of the natural rubber flakes, after removal of the liquid phase from the natural rubber flakes, but before actual drying, or during or after drying, or both. The incorporation of the age stabilizer is preferably carried out by stirring, grinding, kneading, by diffusion in a suspension of the natural rubber and the age stabilizer in water or any other suitable method, for a period of time which allows effective incorporation into the final (dried) natural rubber.

[0026] In principle, the method according to the application can be applied to all plant species which are suitable for obtaining natural rubber.Examples of such plants include members of the Asteraceae family, such as Taraxacum sp. or Scorzonera sp., in particular Taraxacum krim-saghyz, Taraxacum bicorne, Taraxacum brevicorniculatum, or Scorzonera tau-saghyz, Scorzonera Uzbekistanica, Scorzonera teke-saghyz, Scorzonera hispanica, Scorzonera tau-saghyz, or Parthenium incanum, or other species such as Apocynum venetum, Asclepias incarnata, Asclepias cornuti, Asclepias sub-lata, Asclepias syrica, Cacalia atriplicifolia, Campanula america, Chicorium intybus, Chondrilla ambigua, Chondrilla pauciflora, Crysothamnus nauseousus, Cryptostegia grandiflora, Euphorbia lathyris, Lactuca serriola, Lactuca sativa, Parthenium incanum, Pycnanthemum incanum, Solidago altissima, Solidago gram inifolia, Solidago leavenworthii, Solidago rigida, Sonchus arvensis, Sonchus oleraceous, Teucreum canadense, or Silphium sp., or mixtures of these plants and also natural occurring or cultivated hybrids of the above mentioned species.

[0027] According to the application, the plant material from which the juice and / or its components are obtained can be, in particular, a plant species or a mixture of plant species which thrives under Central European climatic conditions and which contains natural polyisoprene in its juice.

[0028] The plant or plant part is preferably introduced into the process as fresh plant material, optionally after a certain storage period, for example a storage period of up to 1 year, but the plant or plant material used is not dried alone. Thus, it is preferred according to the application that the plant material still contains at least 10 %, preferably at least 25 %, further preferably at least 40 %, 50 %, 60 %, 70 %, 80 %, 90 % or even 95 % of the moisture it had at the time of harvesting when it is processed according to the process described here. However, it is also possible to use plant material which has a relatively low moisture content after storage, for example < 10 %, < 5 %, < 3 %, < 2 % or < 1 %.

[0029] According to the application, the plant is preferably selected from Taraxacum species or Scorzonera species, in particular from Russian dandelion such as Taraxacum koksaghyz, Taraxacum officinale, Taraxacum biforme, Taraxacum brevicorniculatum, or from Scorzonera taraxacifolia, Scorzonera uzbekistanica, Scorzonera kotschya, Scorzonera hispanica, Scorzonera taraxacifolia, or mixtures of these plants; preferably from Taraxacum koksaghyz, Scorzonera taraxacifolia, Scorzonera uzbekistanica, Scorzonera kotschya or mixtures or hybrids thereof; particularly preferably from Taraxacum koksaghyz or from Scorzonera taraxacifolia. However, it is particularly preferred according to the application to obtain natural rubber from Taraxacum species, in particular from Russian dandelion, preferably from Taraxacum koksaghyz or Taraxacum officinale, particularly preferably from Taraxacum koksaghyz. Hybrids involving Taraxacum koksaghyz or Taraxacum officinale are also particularly suitable. The plant material used can also be only a part of the whole plant for the process according to the application, in particular a part in which the concentration of natural polyisoprene is particularly high, for example the roots of the plant in the case of Taraxacum.

[0030] In principle, the age stabilizer used can be any known age stabilizer. The age stabilizer is preferably selected from the group consisting of antioxidants, metal ion complexing agents and / or radical scavengers, it being possible for various age stabilizers to be used as a mixture or combination.

[0031] Preferably, the age stabilizer is selected from the group consisting of butylated hydroxytoluene (BHT), vitamin E or derivatives thereof in at least one stereoisomeric form, N-C 1-12alkyl-N'-phenyl-p-phenylenediamine such as N-isopropyl-N'-phenyl-p- phenylenediamine, N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine (6PPD), N-1,4- dimethylpentyl-N'-phenyl-p-phenylenediamine (7PPD) or N,N'-bis-1,4-(1,4- dimethylpentyl)-p-phenylenediamine (77PD), diaryl-p-phenylenediamine (DTPD), 4,4'- bis(C 1-12 alkylamino)triphenylamine, 7,8-dimethylisoalloxazine or a compound containing 7,8- dimethylisoalloxazine as a structural building block such as riboflavin, p-phenylenediamine, a p- dinitrosylaromatic hydrocarbon such as poly-p-dinitrosylbenzene, an oligomeric 2,2,4- trimethyl-1,2-dihydroquinoline (TMQ), styrenated diphenylamine (DDA), cumylated diphenylamine, a zinc salt of 4- and 5-methylthiobenzimidazole, 2,6-di-tert-butylphenol, 2,6-di-tert- butyl-4-ethylphenol, 2,2'-methylenebis(6-tert-butyl-p-cresol), poly(dicyclopentadiene-co-p- cresol), n-octadecyl beta-(4-hydroxy-3,5-di-tert-butylphenyl)propionate, 2,2'-methylenebis(4- methyl-6-tert-butylphenol) (BPH), 2-methyl-4,6-bis(octylthiomethyl)phenol, thio-bisphenol, 4,4'- bis(1,1 -dimethylbenzyl)diphenylamine (CDPA), octylated diphenylamine (ODPA), phenyl-a- naphthylamine (PAN), phenyl-beta-naphthylamine (PBN), tris(nonylphenyl)phosphite, sodium hypophosphite, 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ), 2-mercaptobenzimidazole (MBI), methyl-2-mercaptobenzimidazole (MMBI), or any combination of the foregoing. Preferably, the aging stabilizer is selected from butylated hydroxytoluene (BHT), vitamin E in the form of tocopherol or tocotrienol, in particular demethyl-tocotrienol, gamma-tocotrienol, delta-tocotrienol or a mixture of gamma- and delta-tocotrienol (e.g. "DMT3" from Tricutis), a zinc salt of di-n- butyl dithiocarbamic acid, one of the aforementioned phenylenediamines, and a mixture of butylated reaction products of p-cresol and dicyclopentadiene according to formula (I) (wherein n = 1, 2, 3, 4, 5, 6, 7, 8 or 9) (e.g. the product sold under the name "Mark 1990" by Omnova Solutions).

[0032]

[0033] ​Further preferred, the aging stabilizer is selected from the group consisting of butylated hydroxytoluene (BHT), vitamin E in the form of tocopherol or tocotrienol, in particular demethyl-tocotrienol, gamma-tocotrienol, delta-tocotrienol or a mixture of gamma- and delta-tocotrienol (e.g. "DMT3" from Tricutis), and a compound according to formula (I) (wherein n = 1, 2, 3, 4, 5, 6, 7, 8 or 9) (e.g. "Irganox® L) from Everlight New Materials. L), and further preferred selected from the group consisting of BHT or a compound according to formula (I), in particular Irganox® L from Everlight New Materials. L. Particularly preferred, the aging stabilizer used is at least butylated hydroxytoluene (BHT), optionally in combination with another of the aforementioned. If a mixture is used, the preferred mixture is BHT with vitamin E in the form of tocopherol or tocotrienol and / or with a compound according to formula (I), in particular Irganox® L from Everlight New Materials. L.

[0034] The amount of aging stabilizer used is calculated in such a way that the aging stabilizer is available upon contact with the polymer-containing juice, in an amount resulting in a total amount of aging stabilizer in the final (dried) natural rubber of at least 0.01 phr, preferably in an amount from 0.05 to 5 phr, further preferred from 0.10 to 3.5 phr, particularly preferred from 0.25 to 2 phr, most preferred from 0.4 to 1 phr, based on the final dried rubber.

[0035] The unit "phr" (parts per hundred parts of rubber by weight) used here is the conventional indication for amounts of mixtures formulations in the rubber industry. The dosage in parts by weight of an individual substance is always based here on the total mass of all rubbers present in 100 parts by weight of the mixture.

[0036] The aging stabilizer can be added to the plant material / juice / ingredients thereof in any suitable form. Depending on the state of matter of the aging stabilizer itself, it can be added to the plant material / polymer-containing juice and / or ingredients thereof in the form of a powder, a suspension, a liquid or a solution. It is particularly preferred here if the aging stabilizer itself is a solid, that the aging stabilizer is very finely ground, suspended in a liquid or dissolved in a suitable organic or aqueous solvent before being brought into contact with the juice. If the aging stabilizer is finely ground, it is preferred that its maximum particle size is 1000 pm. If the aging stabilizer is dissolved, it is preferred to use an aqueous solvent or a suitable organic solvent. If an aqueous solvent is used, water or, for example, an aqueous buffer can be used, and as organic solvent it is preferred to use ethanol, isopropanol or a process oil (oil based on plants or minerals). A mixture of suitable aqueous and organic solvents can also be used. If an organic solvent is used because the aging stabilizer is not soluble in water, the aging stabilizer can crystallize out again when it is added to the aqueous system used to obtain or purify natural rubber. If the aging stabilizer itself is present as a pure substance in liquid form, it can also be used directly in this form or, if desired, diluted with another suitable liquid, for example with one of the solvents mentioned above.

[0037] The natural rubber obtained from the juice and admixed with the aging stabilizer can be used to produce a rubber composition from which rubber articles can be produced.

[0038] In addition to the ingredients of natural origin derived from natural rubber, further ingredients can also be added to the rubber composition in order to adapt the composition particularly to the intended processing purpose. Thus, at least one of the following ingredients can be added to the rubber composition according to the application:

[0039] (i) a further type of rubber selected from natural rubber or synthetic rubber

[0040] (ii) a filler, preferably carbon black and / or silica

[0041] (iii) a plasticizer

[0042] (iv) an activator

[0043] (v) a bonding agent

[0044] (vi) a pigment

[0045] (vii) a vulcanization accelerator

[0046] (viii) a vulcanization retarder

[0047] (ix) a further crosslinking agent

[0048] (x) further admixtures.

[0049] All these additives are well known in the art of rubber production technology. The rubber mixture can additionally contain further ingredients (further ageing stabilizers, processing aids, coupling agents, reinforcing resin systems,...).

[0050] The natural rubber produced by the process of the present application can be used for the production of rubber articles, either alone or in the form of a rubber mixture. Preferred rubber articles are those which are subjected to mechanical stress and at the same time have elasticity. Such articles are preferably selected from the group consisting of tires, in particular vehicle tires, or tire parts, bellows, conveyor belts, air springs, belts, transmission belts, such as V-belts, cogged belts, flat belts, V-ribbed belts, hoses, shoe soles, rubber rings, medical articles and tubes.

[0051] For the production of tires, the rubber composition can optionally contain, in addition to natural polyisoprene, at least one further type of rubber. It can be selected from the group consisting of natural polyisoprene and / or synthetic polyisoprene and / or epoxidized polyisoprene and / or butadiene rubber and / or butadiene-isoprene rubber and / or solution-polymerized styrene-butadiene rubber and / or emulsion-polymerized styrene-butadiene rubber and / or styrene-isoprene rubber and / or liquid rubber (having a molecular weight Mw of more than 20 000 g / mol) and / or halogenated butyl rubber and / or polynorbornene and / or isoprene-isobutylene copolymer and / or ethylene-propylene-diene rubber and / or nitrile rubber and / or chloroprene rubber and / or acrylate rubber and / or fluoro rubber and / or silicone rubber and / or polysulfide rubber and / or epichlorohydrin rubber and / or styrene-isoprene-butadiene terpolymer and / or hydrogenated acrylonitrile-butadiene rubber and / or hydrogenated styrene-butadiene rubber. Preferably, it is selected from other types of natural rubber, such as natural rubber from Hevea brasiliensis, synthetic polyisoprene and / or butadiene rubber and / or solution-polymerized styrene-butadiene rubber and / or emulsion-polymerized styrene-butadiene rubber. The synthetic rubber can optionally also be functionalized by suitable groups. Such rubber mixtures are particularly suitable for the production of pneumatic vehicle tires, in particular their treads, which are environmentally friendly and have a low rolling resistance.

[0052] In the production of industrial rubber articles, such as bellows, conveyor belts, belts, transmission belts and hoses, and shoe soles, possible additional rubber components are in particular nitrile rubber, hydrogenated acrylonitrile-butadiene rubber, chloroprene rubber, butyl rubber, halogenated butyl rubber or ethylene-propylene-diene rubber. The industrial rubber articles are used everywhere in daily life, for example in elevators, the automotive industry, the raw materials industry, the food industry and medical technology.

[0053] If the rubber mixture is used for the production of a rubber article, it is preferred that the rubber mixture comprises the natural rubber comprising natural polyisoprene and produced by the method according to the application in an amount of from 0.1 to 99 phr, preferably of from 0.5 to 90 phr, particularly preferably in an amount of from 5 to 85 phr. Further types of rubber that can be used are further natural rubbers (e.g. natural rubber from the rubber tree Hevea brasiliensis) or synthetic rubbers (such as preferably butadiene rubber and / or styrene-butadiene rubber, which can optionally be hydrogenated). However, it is also possible that the rubber used in the rubber composition according to the application contains only (up to 100 phr) the natural rubber produced by the method according to the application.

[0054] For the production of a rubber article, the polymers in the rubber composition can be at least partially covalently bonded to each other by means of a crosslinking agent (in any combination of natural rubber and synthetic rubber with each other). This means that the crosslinking agent forms covalent bonds with at least two polymer chains, so that the polymer chains are covalently bonded to each other by means of the crosslinking agent. Crosslinking agents suitable for this purpose are known in the art.

[0055] If a conventional vulcanization is carried out, the vulcanization of the rubber composition can be carried out in the presence of sulfur and / or a sulfur donor by means of a vulcanization accelerator, it being possible for some vulcanization accelerators to simultaneously act as sulfur donors. The accelerators can be selected from the group consisting of thiazole accelerators and / or mercapto group-containing accelerators and / or sulfenamide accelerators and / or thiocarbamate accelerators and / or thiuram accelerators and / or thiophosphate accelerators and / or thiourea accelerators and / or xanthate accelerators and / or guanidine accelerators and / or morpholine derivatives. Preference is given to using sulfenamide accelerators selected from the group consisting of N-cyclohexyl-2-benzothiazole sulfenamide (CBS) and / or N,N-dicyclohexylbenzothiazole-2-sulfenamide (DCBS) and / or N-tert-butyl-2-benzothiazylsulfenamide (TBBS).

[0056] The sulfur donor substances used can be any sulfur donor substances known to the person skilled in the art.

[0057] Further network-forming systems, as are available for example under the trade names Vulkuren (R) , Duralink (R) or Perkalink (R) , or network-forming systems as described in WO 2010 / 049216 A2 can also be used in the rubber composition.

[0058] The rubber composition also preferably contains at least one filler such as silica, carbon black and optionally further known polar and / or nonpolar fillers such as aluminosilicates and other silicates, chalk, kaolin, starch, magnesium oxide, zinc oxide, clay minerals such as bentonite, titanium dioxide and / or rubber gels, and also fibres (for example aramid fibres, glass fibres, carbon fibres, cellulose fibres), carbon nanotubes (CNT, including discrete CNT, so-called hollow carbon fibres (HCF) and modified CNT containing one or more functional groups such as hydroxyl, carboxyl and carbonyl groups) and / or graphite and / or graphene and / or so-called "carbon-silica dual-phase fillers".

[0059] If the filler is at least one silica, the rubber composition contains preferably 1 to 300 phr, particularly preferably 1 to 200 phr and most preferably 1 to 180 phr of the at least one silica.

[0060] If the filler is at least one carbon black, the rubber composition contains preferably 1 to 200 phr, particularly preferably 1 to 170 phr and most preferably 1 to 100 phr of the at least one carbon black.

[0061] The silica can be a silica known to the person skilled in the art as suitable as a filler for tire rubber mixtures. It is preferred to use a precipitated silica. It is particularly preferred to use a finely divided precipitated silica having a nitrogen surface area (BET surface area) of from 35 to 400 m 2 / g, preferably from 35 to 350 m 2 / g, particularly preferably from 85 to 320 m 2 / g, preferably from 60 to 330 m 2 / g, particularly preferably from 80 to 300 m 2 / g, particularly preferably from 80 to 300 m 2 / g, according to ASTM D 3765.

[0062] If the rubber composition contains carbon black, all types of carbon black known to the person skilled in the art are conceivable. However, it is preferred to use a carbon black having an iodine adsorption value according to ASTM D 1510 of from 30 to 250 g / kg, preferably from 30 to 180 kg / g, and a DBP value according to ASTM D 2414 of from 80 to 200 mL / 100 g, preferably from 100 to 200 mL / 100 g, particularly preferably from 115 to 200 mL / 100 g.

[0063] The rubber composition according to the application can also comprise a mixture of two or more of the mentioned fillers.

[0064] Silane coupling agents can be used as adhesion promoters between inorganic materials, such as glass beads, glass chips, glass surfaces, glass fibers or oxidic fillers, preferably silica, and organic polymers, such as thermosets, thermoplastics or elastomers, or as crosslinkers and surface modifiers for oxidic surfaces.

[0065] Silane coupling agents that can be used here include any silane coupling agents known to the person skilled in the art for rubber mixtures. Such coupling agents known from the prior art are bifunctional organosilanes which have at least one alkoxy, cycloalkoxy or phenoxy group as leaving group on the silicon atom and have as further functional group a group which can participate in a chemical reaction with a double bond of a polymer after cleavage, if necessary. The latter group can for example comprise the following chemical groups: -SCN, -SH, -NH2 or -Sx- (where x = 2 to 8).

[0066] Carbon black coupling agents can also be used.

[0067] In the context of the present application, zinc oxide is not counted as one of the fillers, but can be present in the rubber composition, preferably in combination with stearic acid.

[0068] Furthermore, the rubber composition preferably also comprises further additives.

[0069] In addition to zinc oxide (ZnO) and stearic acid, the further additives can essentially be plasticizers, vulcanization accelerators, anti-ozonants, further aging stabilizers, reinforcing resins including HMMM / HMT, tackifying resins, plasticizing aids, bonding systems, reinforcing resins and further activators or processing aids, such as fatty acid salts, for example zinc soaps, and fatty acid esters and derivatives thereof, for example zinc stearate, or zinc complexes, for example zinc ethylhexanoate.

[0070] Known plasticizers include aromatic, naphthenic or paraffinic mineral oil plasticizers, such as MES (mild extract solvate) or RAE (residual aromatic extract) or TDAE (treated distillate aromatic extract), or rubber-to-liquid oil (RTL) or biomass-to-liquid oil (BTL) or ointments or plasticizer resins or liquid polymers, such as liquid BR.

[0071] The proportion of the total amount of further additives is preferably 3 to 150 phr, preferably 3 to 100 phr and particularly preferably 5 to 100 phr.

[0072] The present invention further provides the use of the rubber composition described for producing an elastomeric material, for example for producing rubber products such as bellows, conveyor belts, air springs, belts, transmission belts, for example V-belts, toothed belts, flat belts, V-ribbed belts, hoses, shoe soles, rubber rings, tactile sensors for medical or robotic applications, medical products, tubes or in particular vehicle tires (including parts thereof). The present invention therefore further provides an elastomeric material, the production of which involves the use of at least one rubber composition according to the invention.

[0073] "Vehicle tire" is understood to mean pneumatic vehicle tires and solid rubber tires, including tires for industrial and construction site vehicles, truck tires, car tires and two-wheeled vehicle tires. The rubber composition of the present invention can also be used to produce certain components of such tires, for example, for producing the tread or carcass mix, including sidewalls, inner liner, apex, belt, shoulder, barrier, additional inserts (for example runflat tires), belt profiles, carcass, bead reinforcement and / or band. DETAILED DESCRIPTION

[0074] Example 1: Addition of various aging stabilizers

[0075] As shown in Table 1, various aging stabilizers were brought into contact with the natural rubber during an incubation period of 8 hours. The rubber produced was stored at 70° C. for up to 14 days. The number average (M) of the natural rubber polymer was determined by means of gel permeation chromatography. n ) and weight average (M w ) molecular weight (from which the polydispersity coefficient can be calculated) determines the stability against aging in the rubber obtained. Comparison of these values ​​over time gives a measure of the aging of the rubber.

[0076] Table 1:

[0077]

[0078]

[0079] (1) Polydispersity coefficient (M w / Mn)

[0080] (2) LNR = Natural rubber from dandelion (in this case rubber grass)

[0081] (3) IR: synthetic rubber

[0082] (4)NR: Natural rubber from the Hevea brasiliensis tree

[0083] The degree of stability against aging is determined by the number average molecular weight ratio Mn fresh / Mn at 70 ° C for 14 days:

[0084] Results:

[0085] Un-aged stabilized LNR: 2.55: molecular weight reduction, aging

[0086] LNR with BHT: 2.0: average aging

[0087] LNR with : 1.7: average aging

[0088] IR: 1.46: slight aging

[0089] NR: 1.03: little to no molecular weight reduction, little to no material aging

[0090] Example 2: Quality characteristics of the aging-resistant natural rubber composition

[0091] The further ingredients shown in Table 3 were incorporated into the natural rubber compositions 1 to 6 produced according to Example 1 and into the natural rubber according to batches 11 and 12 which were also compounded with a vitamin E derivative in order to produce rubber compositions suitable for tire production. To this end, 100 parts by weight of each of the rubber compositions 1 to 6 as well as 11 and 12 (see Table 2) were compounded with the further components indicated in Table 3 in parts by weight and processed to form a rubber material:

[0092] Table 2:

[0093] Batch number

[0094] 1. Un-aged stabilized LNR, fresh

[0095] 2. Un-aged stabilized LNR, aged 14 days / 70°C

[0096] 3. LNR with BHT, fresh

[0097] 4. LNR with BHT, aged 14 days / 70°C

[0098] 5. LNR with , fresh

[0099] 6. LNR with , aged 14 days / 70°C

[0100] 11. LNR with DMT3, fresh

[0101] 12. LNR with DMT3, aged 14 days / 70°C

[0102] LNR = natural rubber from dandelion (in this case, rubber grass)

[0103] Table 3: Additional ingredients of the rubber composition, each in (parts by weight)

[0104]

[0105] The results of the quality test and load test of the produced rubber compositions are shown in Table 4.

[0106]

[0107]

[0108] The quality test results show that the addition of the aging stabilizer to the natural rubber composition has not only a positive influence on the aging of the natural rubber, but also on the properties of the rubber produced from this material.

[0109] Regarding the evaluation in Table 4:

[0110] (A) A smaller drop in the difference in rebound resilience provides an advantage in the trade-off between rolling resistance and wet grip of a vehicle tire

[0111] (B) The smaller the drop in tensile strength after aging, the better the durability

[0112] (C) The smaller the drop in breaking energy density after aging, the better the durability

[0113] (D) The lower the DIN abrasion after aging, the longer the life of the tire.

Claims

1. A method for obtaining aging-resistant natural rubber, the method comprising the following steps: (I) providing a plant material comprising a polymer-containing juice, wherein the polymer-containing juice contains at least natural polyisoprene, (II) treating the plant / the plant material in such a way that the juice and / or its components are separated from the rest of the plant tissue, (III) contacting the plant material / the polymer-containing juice and / or components thereof with at least one aging stabilizer, (IV) coagulating and / or agglomerating the natural polyisoprene to provide a natural rubber sheet, (V) optionally washing the natural rubber sheet, (VI) obtaining the natural rubber flakes from the extract / wash solution, (VII) Optionally drying the natural rubber (VIII) optionally incorporating the aging stabilizer into the natural rubber, wherein the contacting with the aging stabilizer according to step (III) is carried out before drying the natural rubber or at the latest during drying the natural rubber, wherein the plant material comprises at least Russian dandelion, and the at least one aging stabilizer is selected from butylated hydroxytoluene (BHT), vitamin E or a derivative thereof, and a compound according to formula (I), wherein n=1, 2, 3, 4, 5, 6, 7, 8 or 9, Formula (I).

2. The method according to claim 1, wherein The method is carried out with fresh, optionally stored, but not separately dried plant material.

3. The method according to claim 1, wherein Step (III) is carried out before, during or after step (II), before, during or after step (IV) and / or before or during step (V), but in any case before or at the latest during step (VII).

4. The method according to any one of claims 1 to 3, wherein The plant material comprises at least rubber grass.

5. The method according to any one of claims 1 to 3, wherein At least butylated hydroxytoluene (BHT) is used as an aging stabilizer.

6. The method according to any one of claims 1 to 3, wherein The aging stabilizer is added to the plant material / the polymer-containing juice and / or components thereof in such an amount that it is present in the natural rubber obtained in a total amount of at least 0.01 phr.

7. The method according to claim 6, wherein: The aging stabilizer is added to the plant material / the polymer-containing juice and / or components thereof in such an amount that it is present in the natural rubber obtained in an amount of from 0.05 to 5 phr.

8. The method of claim 6, wherein: The aging stabilizer is added to the plant material / the polymer-containing juice and / or components thereof in such an amount that it is present in the natural rubber obtained in an amount of from 0.10 to 3.5 phr.

9. The method of claim 6, wherein: The aging stabilizer is added to the plant material / the polymer-containing juice and / or components thereof in such an amount that it is present in the natural rubber obtained in an amount of from 0.25 to 2 phr.

10. The method of claim 6, wherein: The aging stabilizer is added to the plant material / the polymer-containing juice and / or components thereof in such an amount that it is present in the natural rubber obtained in an amount of from 0.4 to 1 phr.

11. The method according to any one of claims 1 to 3, wherein The aging stabilizer is added to the plant material / the polymer-containing juice and / or its optionally purified fractions in the form of a powder, a suspension, a liquid or a solution.

12. The method according to any one of claims 1 to 3, wherein The contact of the aging stabilizer with the natural rubber occurs under at least one of the following conditions: (i) At temperatures ranging from -25°C to 100°C (ii) by mechanical agitation, or by diffusion in a suspension of rubber and aging stabilizer in water (iii) a period of at least 10 minutes.

13. The method of claim 12, wherein: The contacting of the aging stabilizer with the natural rubber is at a temperature ranging from 0°C to 90°C.

14. The method of claim 12, wherein: The contacting of the aging stabilizer with the natural rubber is at a temperature ranging from 10°C to 80°C.

15. The method of claim 12, wherein: The aging stabilizer is contacted with the natural rubber by stirring, rolling, grinding or kneading or a combination thereof.

16. The method of claim 12, wherein: The contact of the aging stabilizer with the natural rubber lasts for at least 30 minutes.

17. The method of claim 12, wherein: The contact of the aging stabilizer with the natural rubber lasts for at least 1 hour.

18. A rubber composition comprising a natural rubber produced by the method of any one of the preceding claims.

19. The rubber composition according to claim 18, wherein The rubber composition further comprises at least one of the following additives: (i) Another type of rubber selected from natural rubber or synthetic rubber (ii) Filler (iii) Plasticizers (iv) Activator (v) Adhesives (vi) Pigments (vii) Vulcanization accelerator (viii) Vulcanization retardants (ix) Additional cross-linking agents (x) Other admixtures.

20. The rubber composition according to claim 19, wherein The filler is carbon black and / or silica.

21. Use of the rubber composition according to any one of claims 18 to 20 for producing a rubber product.

22. A rubber product produced from the rubber composition according to any one of claims 18 to 20.

23. The rubber product according to claim 22, wherein: The rubber product is selected from tires, bellows, air springs, belts, hoses, shoe soles, rubber rings, and medical products.

24. The rubber product according to claim 23, wherein The rubber product is selected from a V-belt, a toothed belt, and a flat belt.

25. The rubber product according to claim 24, wherein The rubber product is a V-ribbed belt.

26. The rubber product according to claim 23, wherein The rubber product is a tire component.

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