Stabilized rubber composition providing protection against ozone

Abstract

A rubber composition having a good antiozonation performance, particularly without the need for the use of 6PPD. Such a rubber composition is suitable for rubber articles, which include, besides sealings and gaskets, especially vehicle tires, such as rubber pneumatic tires, solid tires and non-pneumatic tires, and as well general rubber products that are exposed to continuous and intermittent dynamic operation conditions and require protection from ozonation like belts, hoses, cables, automotive mounts and bushings. In the rubber composition, the antiozonant compound is a partially hydrogenated quinoline derivative of formula (I) and is used to protect rubber composition from ozonation and consecutively from the damaging effect caused to the rubber composition by ozonation.

Description

[0001] Stabilized rubber composition providing protection against ozone

[0002] FIELD OF THE INVENTION

[0003] The present invention described herein in the following relates to rubber compositions and, more particularly, to tire rubber compositions having a good antiozonation performance, and particularly having good antiozonation performance without the need for the use of 6PPD. The rubber compositions according to the present invention are particularly suitable for rubber articles, which include, besides sealings and gaskets, especially vehicle tires, such as rubber pneumatic tires, solid tires and non-pneumatic tires, and as well general rubber products that are exposed to continuous and intermittent dynamic operation conditions and require protection from ozonation like belts, hoses, cables, automotive mounts and bushings. The invention relates as well to the use of antiozonant compounds defined hereinafter to protect rubber compositions from ozonation and consecutively from the damaging effect caused to the rubber composition caused by ozonation.

[0004] BACKGROUND OF THE INVENTION

[0005] Tires, such as vehicle tires, and other articles that are made of rubber are manufactured from rubber compositions that include rubber, e.g., natural rubber, synthetic rubber or combinations thereof, reinforcing fillers, vulcanizing agents, and other components that improve the physical mechanical characteristics of both the uncured and the cured rubber compositions.

[0006] Natural rubber and synthetic polymers (such as IR, BR, SSBR, ESBR, etc.), but also natural and synthetic oils, fats and lubricants, are subject to oxidation reactions which have a disadvantageous effect on the original desired properties during prolonged storage and during the use phase in the target application, which often involves exposure to elevated temperatures. Depending on the type of polymer, the polymer chains are either shortened, up to a liquefaction of the material, or the crosslink density of the material increases. Both processes are unwanted and need to be prevented to ensure long-term consistency of the material properties.

[0007] Anti-aging agents like antioxidants and antiozonants therefore contribute significantly to the longevity of vehicle tires and other technical rubber articles. They can react with ozone and deactivate radical species, such as e.g., alkyl radicals, hydroxyl radicals, hydroperoxyl radicals, and alkylperoxy radicals, and thus protect the rubbers from degradation reactions.

[0008] Anti-ageing agents which react in particular with ozone and are able to protect the rubber from the detrimental effects of ozone are also referred to as "antiozonant agents" or "antiozonants". If rubber articles based on highly unsaturated elastomers remain unprotected, ozone, which is present in the environment, will attack the surface of the rubber material. This ozone attack will result in cracks on the surface of the rubbers, particularly if the rubber is under strain during usage. Those initial cracks can further develop into deep and large cracks, especially when the rubber article is subject to dynamic load conditions. Such deep and large cracks may not only shorten the service life of the rubber articles such as tires but may as well - in extreme cases - eventually lead to mechanical failure and thereby pose safety issues of the rubber article in use. Different standards like DIN, ISO, VDE, SAE, and ASTM describe static (“static ozone cracking test”) and dynamic methods (“dynamic ozone cracking test”) for the investigation of the behavior of rubber samples towards ozone. Usually, rubber samples are stretched, and ozone is applied at defined temperature, humidity, and air velocity. When the surface ozone cracks of the “comparative rubber formulation part” are graded, a normalized cracking index can be calculated. For dynamic ozone cracking testing, the samples are additionally subjected to a cyclic strain in the ozone chamber. To combat the ozone attack on rubber, various antiozonants have been developed and commercialized in the past to slow down the formation of the ozone cracks under static and dynamic conditions. For example, waxes of various characteristics have been developed and used in rubbers against static ozone attack by forming a film barrier on the surface. However, such film will break and lose its protective properties against ozone under dynamic conditions.

[0009] For dynamic protection, various chemical antiozonants have been developed and are commercially available, with one of the well-known and widely used groups being the substituted phe- nyl-p-phenylenediamines (PPDs), wherein 6PPD (N-1 ,3-dimethylbutyl-N'-phenyl-p-phenylenedi- amine [CAS number: 793-24-8]) is one of its most popular representatives. The PPD “family” further includes e.g. IPPD (N-isopropyl-N'-phenyl-p-phenylenediamine), 7PPD (N-(1 ,4-dime- thylpentyl)-N'-phenyl-p-phenylenediamine), 77PD (N,N'-bis(1 ,4-dimethylpentyl)-p-phenylenedia- mine), 44PD (N,N'-di-sec-butyl-p-phenylenediamine) and 8PPD (N-(l-methylheptyl)-N'-phenyl- p-phenylenediamine).

[0010] The group of PPDs may also include derivatives such as N-cyclohexyl-N'-phenyl-p-phenylenedi- amine (CHPPD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditolyl-p-phenylenediamine (DTPD) or SPPD (N-(l-phenylethyl)-N'-phenyl-p-phenylenediamine).

[0011] Yet another group of chemicals selected from quinones (Q), quinoneimines (QI), and quinonedimines (QDI) based on PPD chemistry have been reported in rubber formulations. US6,533,859 discloses a method to pretreat carbon black surface with such chemicals to improve the dispersibility of the carbon black and the dynamic properties of the rubber formulations.

[0012] EP1025155 teaches a process to improve the processability of uncured rubber through high temperature mixing of quinonedimine, natural rubber, and carbon black.

[0013] US8,207,247 teaches a process to mix a rubber composition comprising natural rubber and an additive selected from aforementioned chemicals, preferably a quinonedimine.

[0014] Recently, WO 2022 / 069001 disclosed phenothiazine compounds, their use in rubber blends and vehicle tires as antiozonant. And WO 2022 / 146441 discusses rubber compositions having improved antiozonation performance comprising hydroxyl-substituted PPDs which are particularly suitable for rubber articles such as tires.

[0015] It is known that the PPDs can also act as primary and secondary antioxidants by scavenging free radicals and converting hydroperoxides into less harmful intermediates.

[0016] Some anti-aging agents, such as IPPD, are partially poorly soluble in rubbers and thus migrate to the surface and form a colored film there. This effect is known under the name "blooming", meaning that the anti-ageing agent “blooms” from the respective rubber.

[0017] During the service life of rubber compositions comprising antiozonants of the PPD type, when these antiozonants in general (with certain exceptions) migrate to the surface, they react with and provide protection against ozone in the environment, such as in the case of tire sidewalls and treads. The loading of the antiozonant and its migration rate to the surface therefore defines the service life of the rubber articles. Obviously, the better and faster the migration to the surface, the better the initial protection. On the other side, the fixed loading of the antiozonant and an “unregulated”, meaning too fast migration of the antiozonant to the surface will not only negatively impact the long-term protection, but leads to surface leaching and / or volatilization as well, causing “staining” of the article due to excessive surface concentration. In addition, PPDs are also prone to discoloration, which aggravates the visual effects of migration and staining. For example, if a staining antiozonant is used in a black rubber composition which is in proximity to a light-colored rubber part, the staining antiozonant will migrate into the light-colored rubber part and cause discoloration, which represents another problem of PPDs to be addressed. Different kind of compounds and solutions have been evaluated in this regard up to now.

[0018] For instance, US5,047,530 teaches the preparation and use of a larger molecule, substituted triazine for longer lasting and non-staining ozone protection. Still, the molecule itself is prone to discoloration and therefore not suitable for use in light-colored rubber compositions.

[0019] Another group of chemicals, hindered phenols, for example, 2,2'-methylenebis(4-methyl-6-tert- butylphenol), are often used as antioxidants in rubber compositions, even though they apparently offer no protection against ozone attack. Since these hindered phenols are generally nonstaining, they are often compounded in light colored articles where staining should be minimized, such as white sidewalls and colored treads in tires.

[0020] However, those hindered phenols are very efficient antioxidants but typically have limited effectiveness in protecting degradation of rubber compositions from ozone attack.

[0021] In general, it can be said, that compounds showing an excellent antioxidant performance do not necessarily also provide protection from ozone. Hence, it cannot be predicted that a high antioxidant efficiency correlates with a relevant antiozonant performance.

[0022] The literature confirms that antioxidants which can be used to prolong the lifetime of a rubber article under flexing conditions do not necessarily work as antiozonants, i.e., do not necessarily provide any protection against the destructive influence of ozone on rubbers. It has been e.g. explicitly acknowledged decades ago, that the interrelation of ozone cracking and flex cracking is a continuous source of some confusion since conditions for high-speed dynamic weathering exposure are also conditions conducive to flex cracking. Antioxidants which are effective in prolonging flex life may or may not show antiozonant activity. For instance, both N-phenyl-2-naphthylamine and N-iso-propyl-N'-phenyl-p-phenylenediamine have antiflex-crack- ing activity, whereas only the latter is an antiozonant while the former is not (p. 1518 in J. C. AMBELANG et al., Rubber Chemistry and Technology 36 (4), 1963, 1497-1591).

[0023] It is well known that aromatic amines in general have undesirable toxicological properties, as many representatives of this class of chemicals are known to be harmful to human and animal health and aquatic life as well.

[0024] Especially, the continuous use of the well-established antiozonant class of PPDs is becoming more and more critical. The ECHA registration dossier states that “according to available information on degradation, all PPDs in question are not readily biodegradable and no significant biodegradation is observed but full abiotic degradation takes place”.

[0025] A possible explanation for the non-biodegradability is the hypothesis that 6PPD itself and possibly also 6PPD-quinone - one of its decomposition products - are highly toxic against bacteria. Even low concentrations may have a significant effect and kill bacteria or at least inhibit bacterial growth in the biodegradation tests on 6PPD. In the atmosphere rapid photodegradation takes place by reaction with photochemically produced OH radicals. According to the ECHA registration dossier, regarding environmental and monitoring data, 6PPD has been used as an indicator for other members of the PPD family as it is commonly used in tire production.

[0026] A recent study (Tian et al., Science 371 , 185-189 (2021) “A ubiquitous tire rubber-derived chemical induces acute mortality in coho salmon") found that in the U.S. Pacific Northwest, for coho salmon (Oncorhynchus kisutch), the stormwater exposure annually causes an unexplained acute mortality when adult salmon migrate to urban creeks to reproduce. A highly toxic quinone transformation product of N-(1 ,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) was found. The retrospective analysis of representative roadway runoff and stormwater-affected creeks of the U.S. West Coast indicated widespread occurrence of 6PPD-quinone at toxic concentrations. Not only revealed those results unanticipated risks of 6PPD to an aquatic species, but it uncovered as well the toxicological relevance for dissipated tire rubber residues.

[0027] These findings make clear that there is an existing need for identifying suitable alternative compounds to PPDs for their safe use as antiozonants in rubber products, including tires, which could help to reduce or even eliminate the quantity required of 6PPD and other PPDs. In addition it is also preferable, that those alternative solutions have a lower discoloration tendency than PPDs, which helps improving the acceptance by the customer and broadening the application range of such alternative solutions. Durable long-lasting rubber products that retain their original color, remain safe and reliable throughout their service life but at the same time may reduce the release of environmentally toxic substances are presently still an unresolved requirement. Such needs are addressed by the rubber compositions products of the present invention.

[0028] SUMMARY OF THE INVENTION

[0029] It is an object of the invention to provide anti-aging, especially antiozonant compounds which can be used in particular as anti-aging agents in vehicle tires or other technical rubber articles in order to achieve a protective effect for these articles and thereby substituting or reducing the presence of PPDs, especially of 6PPD.

[0030] The object is achieved by the use of partially hydrogenated quinoline derivatives as defined herein below, also called hereinafter “hydroquinoline derivatives” or “compound according to the (present) invention”.

[0031] The antiozonant “compound according to the (present) invention” has the following formula (I): wherein

[0032] X is each either selected from N or a group C-A, wherein at least one of X is N, but no more than two of X are N; and wherein

[0033] A is H, CN or an electron donating group, which is either an oxygen atom or nitrogen atom that is bonded directly to the aromatic ring; or is an aryl group or Ci-C2o-alkyl, Ci-C2o-alkenyl or Ci-C20-alkoxy group; and

[0034] R1, R1', R2, R2are each, independently from one another, selected from group consisting of hydrogen, a Ci-C20-alkyl group, Ci-C20-alkenyl or an aryl group, and wherein one of R1or R1and one of R2or R2' may optionally form together a double bond; and R3, R3’ are independently from one another selected from a Ci-C2o-alkyl group, Ci- C2o-alkenyl or aryl group.

[0035] The compound according to formula (I) of the present invention is a hydroquinoline derivative, more specifically a partially hydrogenated quinoline derivative.

[0036] Such partially hydrogenated quinoline derivatives have been described in WO2017 / 040961 , wherein they are comprised in lubricant compositions that further include a base oil in an amount of greater than 70 weight% of the lubricant composition.

[0037] Based on Quantitative Structure-Activity Relationship (QSAR) models, which - according to ECHA - are believed to provide plausible predictions on environmental fate properties of compounds based on knowledge of their chemical structure, the hydroquinoline derivatives used hereinafter as antioxidants and antiozonants according to the present invention are expected to be less harmful to the environmental and human and animal health, for instance suggesting a lower aquatic toxicity and lower skin sensitizing potential, as compared to the classic aromatic amines used for this purpose, such as e.g., 6PPD or IPPD.

[0038] Furthermore, the object of the present invention, the hydroquinoline derivates of formula (I), are obtained by the methods for producing the partially hydrogenated quinoline derivatives. Additionally their use as an anti-aging agent and / or antioxidant and / or antiozonant is claimed as well.

[0039] Another object of the invention is to provide a rubber composition comprising one or more partially hydrogenated quinoline derivative(s) as defined herein below.

[0040] Embodiments of the invention may be useful for finished rubber articles including nonpneumatic tires, solid tires, pneumatic tires, and tire components. Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0041] Particular embodiments of the present invention include rubber compositions, articles made from such rubber compositions, and the methods for making the same. Such embodiments include the tire product.

[0042] The tire product according to the invention comprises a rubber composition that is based upon a cross-linkable elastomer composition, such cross-linkable elastomer composition comprising for instance a highly unsaturated diene elastomer, a reinforcing filler, a vulcanization package and an antiozonant according to the present invention.

[0043] DETAILED DESCRIPTION OF THE INVENTION

[0044] The rubber composition according to the present invention comprises an antiozonant compound of formula (I) wherein

[0045] X is each either selected from N or a group C-A, wherein at least one of X is N, but no more than two of X are N; and wherein

[0046] A is H, CN or an electron donating group, which is either an oxygen atom or nitrogen atom that is bonded directly to the aromatic ring; or is an aryl group or Ci-C2o-alkyl, Ci-C2o-alkenyl or Ci-C20-alkoxy group; and

[0047] R1, R1', R2, R2are each, independently from one another, selected from group consisting of hydrogen, an Ci-C20-alkyl group, Ci-C20-alkenyl or an aryl group, and wherein one of R1or R1and one of R2or R2' may optionally form together a double bond; and

[0048] R3, R3are independently from one another selected from an Ci-C20-alkyl group, Ci-C20-alkenyl or aryl group.

[0049] The electron donating group in above definition can alternatively be an aryl group or alkyl group The terminology "aryl" group describes any functional group or substituent derived from an aromatic ring, e.g. phenyl, naphthyl, thienyl, indolyl, etc.

[0050] The Ci-C20-alkyl, the Ci-C20-alkenyl or the Ci-C20-alkoxy group may be linear, branched, or cyclic and typically includes 1 to 20 carbon atoms, which means that any integer of 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19, or 20 of the total number of carbon atoms falls under the definition of the alkyl, alkenyl or alkoxy group. The alkyl group may be alternatively described using the formula CnH2n+iwherein n is 1 to 20, as described above. In various embodiments, the alkyl group may be described as methyl, ethyl propyl, butyl, t-butyl, pentyl, hexyl, octyl, nonyl, or any isomer thereof.

[0051] Same applies for the aryl group or the Ci-C20-alkyl group and Ci-C20-alkenyl group defined for the substituents R1, R1, R2, R2, R3and R3. In one embodiment of the present invention R1and R1' in the antiozonant hydroquinoline deri- vate of formula (I) are independently from one another preferably selected from hydrogen or Ci- Cs-alkyl.

[0052] In one embodiment of the present invention R1and R1' in the antiozonant hydroquinoline deri- vate of formula (I) are independently from one another preferably selected from hydrogen or methyl.

[0053] In one embodiment of the present invention R1or R1is more preferably methyl. In one embodiment of the present invention one of R1or R1is more preferably methyl and the other is hydrogen.

[0054] In one embodiment of the present invention R2and R2in the antiozonant hydroquinoline deri- vate of formula (I) are independently from one another preferably selected from hydrogen or Ci- Cs-alkyl.

[0055] In one embodiment of the present invention R2and R2in the antiozonant hydroquinoline deri- vate of formula (I) are independently from one another preferably selected from hydrogen or methyl.

[0056] In one embodiment of the present invention both of R1or R1are more preferably hydrogen.

[0057] In one embodiment of the present invention R2is more preferably hydrogen.

[0058] In one embodiment of the present invention R3and R3in the antiozonant hydroquinoline deri- vate of formula (I) are both preferably selected independently from one another from a Ci-C8- alkyl group.

[0059] In one embodiment of the present invention R3and R3are both more preferably selected independently from one another from a Ci-C4-alkyl group.

[0060] In one embodiment of the present invention R3and R3are both most preferably methyl.

[0061] In another embodiment of the present invention, the position of the two nitrogen atoms in the aromatic moiety of the antiozonant compound is represented by the following two structures of formula (II.1a) or formula (II.1 b):

[0062] Wherein the substituents are defined as above. In one embodiment of the present invention, the antiozonant hydroquinoline derivate is preferably of formula (II.1a) or of formula (II.1 b), wherein

[0063] R1represents hydrogen or methyl;

[0064] R2represents hydrogen or methyl; and

[0065] R3and R3are both selected independently from one another from a Ci-C8-alkyl group, preferably methyl.

[0066] In one embodiment of the present invention, the antiozonant hydroquinoline derivate is of formula (II.1a) or of formula (II.1 b), wherein R1represents preferably methyl.

[0067] In one embodiment of the present invention, the antiozonant hydroquinoline derivate is of formula (II.1a) or of formula (II.1 b), wherein R2represents preferably hydrogen.

[0068] In one embodiment of the present invention, the antiozonant hydroquinoline derivate is of formula (II.1a) or of formula (II.1 b), wherein R3and R3are both selected independently from one another preferably from a Ci-C4-alkyl group

[0069] In one embodiment of the present invention, the antiozonant hydroquinoline derivate is of formula (II.1a) or of formula (II.1 b), wherein R3and R3are both most preferably both methyl.

[0070] In another embodiment of the present invention, the position of the two nitrogen atoms in the aromatic moiety of the antiozonant compound is represented by the following two structures of formula (II.2a) or formula (II.2b): wherein the substituents are defined as above.

[0071] In one embodiment of the present invention, the antiozonant hydroquinoline derivate is preferably of formula (II.2a) or of formula (II.2b), wherein

[0072] R1, R1’ are both selected independently from one another from either hydrogen or a Ci-C8- alkyl group,

[0073] Preferably, wherein

[0074] R1, R1are both selected independently from one another from either hydrogen or a Ci-C4- group.

[0075] Most preferably wherein one R1or R1is hydrogen and the other is methyl; In one embodiment of the present invention, the antiozonant hydroquinoline derivate is preferably of formula (II.2a) or of formula (II.2b), wherein

[0076] R2, R2are both selected independently from one another from either hydrogen or a Ci-C8- alkyl group.

[0077] Preferably, wherein

[0078] R2, R2are both selected independently from one another from either hydrogen or a Ci-C4- group.

[0079] Most preferably wherein both of R2or R2are hydrogen.

[0080] In one embodiment of the present invention, the antiozonant hydroquinoline derivate is preferably of formula (II.2a) or of formula (II.2b), wherein R3and R3are both selected independently from one another from a Ci-C8-alkyl group.

[0081] Preferably, R3, R3are both selected independently from one another from a Ci-C4-group.

[0082] In one embodiment of the present invention, the antiozonant hydroquinoline derivate is of formula (II.2a) or of formula (II.2b), wherein most preferably both of R3or R3are methyl.

[0083] In one embodiment of the present invention, the antiozonant hydroquinoline derivate is of formula (II.2a) or of formula (II.2b), wherein

[0084] R1represents preferably methyl and R1is hydrogen;

[0085] R2and R2are both hydrogen,

[0086] R3and R3are both methyl.

[0087] In various embodiments, the antiozonant hydroquinoline derivate according to the present invention have for instance the following particular structures (111.1a) or (111.1 b): wherein substituent A is defined as above, preferably as below.

[0088] In preferred embodiments, the antiozonant hydroquinoline derivates according to the present invention have the following particular structures (III.2a) or (III.2b): wherein the substituent A is defined as above, preferably as below.

[0089] In further embodiments, the antiozonant hydroquinoline derivate according to the present invention have for instance the following particular structures (IV.1a) or (IV.1 b): wherein the substituents X are defined as above.

[0090] In one embodiment, one of X is nitrogen and one of X is CH.

[0091] In another embodiment, both of X are nitrogen.

[0092] In preferred embodiments, the antiozonant hydroquinoline derivates according to the present invention have the following particular structures (IV.2a) or (IV.2b):

[0093] Wherein the substituents X are defined as above.

[0094] In one embodiment, one of X is nitrogen and one of X is CH.

[0095] In another embodiment, both of X are nitrogen. Examples of additional embodiments for the antiozonant hydroquinoline derivate have the following structures:

[0096] Examples of preferred additional embodiments for the antiozonant hydroquinoline derivate have the following structures:

[0097] The electron donating group represented by A has an atom having at least one lone pair of electrons that is bonded directly to the aromatic ring of the antioxidant or may alternatively be an aryl group or alkyl group. The electron donating group can be alternatively described as an "EDG", as is appreciated in the art. In various embodiments, the electron donating group has an atom, such a nitrogen atom, a phosphorous atom, an oxygen atom or a sulfur atom, that has at least one lone pair of electrons. For example, oxygen and sulfur each typically have two lone pairs of electrons while nitrogen and phosphorous each typically have only one lone pair of electrons. The terminology "lone pair" describes a pair of valence electrons that are not shared with other atoms and / or are not used in chemical bonding. These electrons may also be described as a non-bonding pair of electrons. Preferred structures according to the present invention would be represented by above outlined formula V.a, VI. a, VII. a, VIII. a, IX.a and X.a, as well as formulae V.b, VI. b, VII. b, VIII. b, IX.b and X.b

[0098] In various non-limiting embodiments, analogs of each of the aforementioned structures wherein one, two, or three of the methyl groups are each independently from one another R1, R1, R2, R2, R3, and R3, as described above, are expressly contemplated.

[0099] In other embodiments, the electron donating group is selected from -NR42, -NH2, -OH, -OR4, - NHCOR4, or -OCOR4, wherein each R4is independently from one another a Ci-C8-alkyl group. In another embodiment, the electron donating group is -NH2.

[0100] In another embodiment, the electron donating group is -OH.

[0101] In another embodiment, the electron donating group is most preferably methoxy or ethoxy.

[0102] For example, the electron donating group may be -NR42, wherein each R4is independently an alkyl group having 1 to 8 carbon atoms, as described above

[0103] In one embodiment, each R4is selected independently from one another from a Ci-C4-alkyl.

[0104] In a further embodiment, the electron donating group is -OR4, wherein R4is an alkyl group having 1 to 8 carbon atoms, as described above.

[0105] In one embodiment, R4is preferably a Ci-C4-alkyl. In a further embodiment, the electron donating group is -NHCOR4, wherein R4is an alkyl group having 1 to 8 carbon atoms, as described above.

[0106] In one embodiment, R4is preferably a Ci-C4-alkyl.

[0107] In another embodiment, the electron donating group is -OCOR4, wherein R4is an alkyl group having 1 to 8 carbon atoms, as described above.

[0108] In one embodiment, R4is preferably a Ci-C4-alkyl.

[0109] The electron-donating strength of the alkoxy or amine group comes largely from the lone pairs of electrons on the O and N atoms, respectively, such that each of R4groups can be a hydrogen or a saturated or unsaturated branched or straight chain hydrocarbon moiety and / or may include one or more cycloaliphatic groups and / or one or more aromatic hydrocarbons, or a combination thereof, while not detracting from the electron donating characteristic of the alkoxy or amine group.

[0110] In such embodiments, the term "cycloaliphatic" describes a saturated or unsaturated carbocyclic moiety comprising mono- or bicyclic rings. Cycloaliphatic groups typically include a 3- to 7-mem- bered saturated carbocyclic moiety. Examples of cycloaliphatic moieties include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and the like, including partially unsaturated derivatives thereof such as cyclohexenyl, cyclopentenyl, and the like. Alternatively, the term "hydrocarbon group" may describe a hydrocarbon including from 1 to 20 carbon atoms, e.g. as described above, and includes saturated or unsaturated, branched or straight chain hydrocarbon moieties, including aliphatic moieties and / or one or more cycloaliphatic groups and / or one or more aromatic hydrocarbons, or a combination thereof.

[0111] The electron donating group may alternatively be a thiol, sulfide, thioether, or thioester (e.g. wherein the sulfur atom of the group is adjacent to the group being donated into).

[0112] Alternatively, the electron donating group may be a phosphine.

[0113] Non-limiting examples of structures corresponding to various embodiments of the present invention are set forth in WO2017 / 040961 , such as structures of formula (XI) to (L) disclosed therein, which are hereby incorporated by reference in their entirety. Structures of formula (XI) to (L) of WO2017 / 040961 , wherein one of R1or R1and one of R2or R2' do not form together a double bond, but wherein each is, independently from one another, selected from the group consisting of hydrogen, an C-i-C2o-alkyl group, C-i-C2o-alkenyl or an aryl group are embodiments of the present invention.

[0114] The object of the present invention is achieved by the use of partially hydrogenated quinoline derivatives as defined herein above, which are particularly suitable as an anti-ageing agent and / or antiozonant in vehicle tires.

[0115] They also can be used for producing other technical rubber articles, such as rubber bands, (conveyor) belts, hoses, cables, automotive mounts, bushings, air springs, bellows, profiles, seals, membranes, tactile sensors for medical applications or robots, as well as e.g. shoe soles or parts thereof.

[0116] In the case of vehicle tires or other technical rubber articles, the hydroquinoline derivative compounds of formula (I) are used in particular in a rubber composition.

[0117] A further subject matter of the invention is thus, as already mentioned, a rubber composition.

[0118] The rubber composition according to the invention contains the hydroquinoline derivative compound according to formula (I). The rubber composition according to the invention can in principle be any rubber composition in which the novel use of the hydroquinoline derivative compound of the formula (I) according to the invention achieves improved properties, in particular increased longevity by aging protection and / or ozone protection.

[0119] The rubber composition according to the invention contains at least one rubber.

[0120] The rubber composition according to the invention preferably contains 0.1 to 10 phr (parts per hundred), particularly preferably 0.2 to 5 phr, very particularly preferably 0.3 to 3 phr, of the compound according to formula I).

[0121] The term phr (parts per hundred parts of rubber by weight) used in this specification is the quantity specification customary in the rubber industry for rubber composition, like rubber mixture formulations. The dosage of the parts by weight of the individual substances is referred to in this document to 100 parts by weight of the total mass of all high molecular weight rubber elastomers (Mw greater than 20,000 g / mol) present in the mixture.

[0122] Further components of the rubber compositions according to the present invention are described hereinbelow.

[0123] Rubber elastomers suitable for use with particular embodiments of the present invention include highly unsaturated diene elastomers. According to advantageous embodiments of the invention, the rubber composition according to the present invention contains at least one diene rubber.

[0124] In a further embodiment the rubber composition contains a diene rubber or a mixture of two or more different diene rubbers.

[0125] Diene rubbers are rubbers which are produced by polymerization or copolymerization of dienes and / or cycloalkenes and thus either have C = C double bonds in the main chain or in the side groups.

[0126] Diene rubbers are preferably selected from the group consisting of natural polyisoprene (NR), synthetic polyisoprene (IR), epoxidized polyisoprene (ENR), (poly)butadiene rubber (BR), buta- diene-isoprene rubber, styrene- butadiene rubber (SBR), solution-polymerized styrene- butadiene rubber (SSBR), emulsion-polymerized styrene-butadiene rubber (ESBR), styrene-iso- prene rubber, isobutylene isoprene rubber (HR), butadiene copolymers, isoprene copolymers and mixtures of these elastomers, liquid rubbers having a molecular weight Mw of greater than 20,000 g / mol, polynorborneneisoprene-isobutylene copolymer, acrylate rubber, fluorine rubber, silicone rubber, polysulfide rubber, epichlorohydrin rubber, styrene-isoprene-butadiene terpolymer, and hydrogenated styrene-butadiene rubber.

[0127] Nitrile rubber, hydrogenated acrylonitrile butadiene rubber, chloroprene rubber, butyl rubber, ha- lobutyl rubber and / or ethylene-propylene-diene rubber (EPDM), which are often used in the production of technical rubber articles, such as belts and hoses, and / or shoe soles, may optionally be used as well with regard to the present invention.

[0128] The natural and / or synthetic polyisoprene of all embodiments can be both cis-1 ,4-polyisoprene and 3,4-polyisoprene and copolymers thereof.

[0129] The polyisoprenes include synthetic cis-1 ,4 polyisoprene, which may be characterized as possessing cis-1 ,4 bonds at more than 90 mol.% or alternatively, at more than 98 mol.%.

[0130] Natural rubber (NR) is such a cis-1 ,4 polyisoprene, in which the cis-1 , 4-component in the natural rubber is greater than 99% by weight. Furthermore, a mixture of one or more natural polyiso- prene(s) with one or more synthetic polyisoprene(s) is also conceivable.

[0131] Within the scope of the present invention, the term "natural rubber" is to be understood as naturally occurring rubber which can be obtained from Hevea rubber trees and "non-Hevea" sources. Non-Hevea sources are, for example, Guayule shrubs and soldering teeth such as, for example, TKS (Taraxacum kok-saghyz; Russian Dandelion).

[0132] If butadiene rubber (= BR, polybutadiene) is contained in the rubber composition according to the invention, it can be all types known to the person skilled in the art. These include, inter alia, the so-called high-cis and low-cis types, where polybutadiene having a cis content is greater than or equal to 90% by wt. % as a high-cis type and polybutadiene having a cis content of less than 90% by wt. % is referred to as the low-cis type. A low-cis polybutadiene is, for example, Li- BR (lithium-catalyzed butadiene rubber) with a cis content of 20 to 50 wt. %. With a high-cis BR, particularly good properties and a low hysteresis of the rubber composition are achieved.

[0133] The polybutadienes or polybutadienes used may be end-group-modified with modifications and functionalizations and / or functionalized along the polymer chains. The modification can be those having hydroxy groups and / or ethoxy groups and / or epoxy groups and / or siloxane groups and / or amino groups and / or aminosiloxane and / or carboxy groups and / or phthalocyanine groups and / or silane groups and / or sulfide groups. Other modifications known, also referred to as functionalizations, are also possible. Constituent of such functionalizations may be metal atoms. For the case where at least one styrene-butadiene rubber (styrene-butadiene copolymer) is contained in the rubber composition, it can be both solution-polymerized styrene-butadiene rubber (SSBR) and emulsion-polymerized styrene-butadiene rubber (ESBR), wherein also a mixture of at least one SSBR and at least one ESBR can be used. The terms "styrene-butadiene rubber" and "styrene-butadiene copolymer" are used synonymously in the context of the present invention.

[0134] The styrene-butadiene copolymer used can be end-group-modified and / or functionalized along the polymer chains with the modifications and functionalizations mentioned above for the polybutadiene.

[0135] In one embodiment, at least one diene rubber is selected from the group consisting of natural polyisoprene (NR, natural rubber), synthetic polyisoprene (IR), butadiene rubber (BR), solution polymerized styrene-butadiene rubber (SSBR), emulsion polymerized styrene-butadiene rubber (ESBR), butyl rubber (HR), and halobutyl rubber.

[0136] According to a particular embodiment of the invention, the at least one diene rubber is 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).

[0137] According to a particular embodiment of the invention, the rubber composition contains at least one natural polyisoprene (NR), for instance in amounts of 5 to 55 phr, and according to a particular embodiment of the invention 5 to 25 phr, very particularly 5 to 20 phr. Such a rubber composition exhibits good processability and reversion stability and optimized tearing properties and optimum rolling resistance behavior.

[0138] According to a particular embodiment of the invention, the rubber composition contains at least one polybutadiene (BR, butadiene rubber), for instance in amounts of 10 to 80 phr, particularly 10 to 50 phr, and according to a particular embodiment of the invention 15 to 40 phr. In this way, particularly good friction and abrasion properties of the rubber composition according to the invention and an optimum braking behavior are achieved.

[0139] According to a particular embodiment of the invention, the rubber composition contains at least one solution-polymerized or emulsion-polymerized styrene-butadiene rubber (SSBR or ESBR), for instance in amounts of 10 to 80 phr, particularly 30 to 80 phr, and according to a particular embodiment of the invention 50 to 70 phr. Particularly good rolling resistance properties of the rubber composition according to the invention are hereby achieved. According to particularly advantageous embodiments of the invention, SSBR and ESBR are used in combination with at least one further rubber in order to achieve an optimal and balanced property profile.

[0140] Also suitable for use in particular embodiments of the present invention are rubber elastomers that are copolymers and include, for example, butadiene-styrene copolymers (SBR), butadieneisoprene copolymers (BIR), isoprene-styrene copolymers (SIR) and isoprene-butadiene-styrene copolymers (SBIR) and mixtures thereof.

[0141] The elastomer system can be a blend of various elastomers with a total of 100 phr.

[0142] In view of the above, the rubber compositions according to the present invention may be mixtures of rubbers of different origins.

[0143] In a particular embodiment the rubber compositions according to the present invention include a mixture of one or more natural and one or more synthetic rubbers.

[0144] However, the rubber compositions according to the present invention may include as well only synthetic rubber(s).

[0145] Further, the rubber compositions according to the present invention may also include only natural rubber(s).

[0146] The rubber composition preferably contains at least one filler, for instance in amounts of 30 to 500 phr, particularly 50 to 400 phr, optionally 80 to 300 phr.

[0147] Reinforcing fillers used in the rubber composition according to the present invention include carbon black and / or silica (and associated silane chemistry).

[0148] Carbon black, which is an organic filler, is well known in the rubber compounding field.

[0149] The rubber composition according to the present invention contains 30 to 300 phr, particularity 30 to 200 phr, more particularly 40 to 100 phr of at least one carbon black. In these amounts, carbon black is contained as sole filler or as a main filler. If carbon black is merely present as a further filler in addition to a main filler, such as, in particular, silica (see herein below), the rubber composition according to the present invention contains 0.1 to 60 phr, particularly 3 to 40 phr, especially 5 to 30 phr of at least one carbon black.

[0150] Suitable carbon blacks are any carbon blacks known in the art and suitable for the given purpose for example, any carbon black having a BET surface area or a specific CTAB surface area both of which are less than 400 m2 / g or alternatively, between 20 and 200 m2 / g may be suitable for particular embodiments based on the desired properties of the cured rubber composition. The CTAB specific surface area is the external surface area determined in accordance with Standard AFNOR-NFT-45007 of November 1987. Suitable carbon blacks of the type HAF, ISAF and SAF, for example, are conventionally used in tire treads. Non-limitative examples of carbon blacks include, for example, the N 115, N134, N234, N299, N326, N330, N339, N343, N347, N375 and the 600 series of carbon blacks, including, but not limited to N630, N650 and N660 carbon blacks.

[0151] Silica may also be useful as reinforcement filler. The silica may be any known reinforcing silica for example, any precipitated or pyrogenic silica having a BET surface area and a specific CTAB surface area both of which are less than 450 m2 / g or alternatively, between 20 and 400 m2 / g may be suitable for particular embodiments based on the desired properties of the cured rubber composition.

[0152] Particular embodiments of rubber compositions disclosed herein may include a silica having a CTAB of between 80 and 200 m2 / g, between 100 and 190 m2 / g, between 120 and 190 m2 / g or between 140 and 180 m2 / g.

[0153] Such silicas lead, for example, to rubber compositions for tire treads having particularly good physical properties. In addition, advantages in mixing processing can result from a reduction in the mixing time with constant product properties, which result in improved productivity. Commercially available examples of such silicas are Ultrasil ® VN3 type (trade name) from Evonik and Zeosil ® 1165 MP from Solvay.

[0154] According to particular embodiments of the invention, the rubber composition contains silicic acid as filler, for instance in amounts of 30 to 500 phr, particularly 50 to 400 phr, more particularly 80 to 300 phr. In these amounts, silicic acid is used in particular as sole filler or as a main filler (more than 50% by weight based on the total amount of filler).

[0155] According to a further embodiment of the invention, the rubber composition contains at least one silicic acid as a further filler, in addition to another main filler, such as in particular a carbon black. Under these circumstances it is used in amounts of 5 to 100 phr, particularly 5 to 80 phr, more particularly 10 to 60 phr.

[0156] According to a particular embodiment of the invention, the rubber composition contains 5 to 60 phr, particularly preferably 5 to 40 phr, of at least one carbon black and 50 to 300 phr, preferably 80 to 200 phr of at least one silica.

[0157] When silica is added to the rubber composition, a proportional amount of a silane coupling agent is also added to the rubber composition. The silane coupling agent is a sulfur- containing organosilicon compound that reacts with the silanol groups of the silica during mixing and with the elastomers during vulcanization to provide improved properties of the cured rubber composition. A suitable coupling agent is one that is capable of establishing a sufficient chemical and / or physical bond between the inorganic filler and the diene elastomer; which is therefore at least bifunctional, meaning which is capable of bonding physically and / or chemically with the inorganic filler. One bond may be established, for example, between a silicon atom of the coupling agent and the surface hydroxyl (OH) groups of the inorganic filler (for example, surface silanols in the case of silica), and the other bond may then be established (physically and / or chemically) with the diene elastomer, for example by means of a sulfur atom. Hence, the silane coupling agents react with the surface silanol groups of the silicic acid or other polar groups during the mixing of the rubber or rubber composition (in situ) or even before the addition of the filler to the rubber in the sense of a pretreatment (pre-modification).

[0158] Silane coupling agents used according to the present invention can be all types known, and one or more different silane coupling agents can be used in combination with one another. The rubber composition can thus contain a mixture of different silanes.

[0159] Coupling agents known from the prior art are bifunctional organosilanes which have at least one alkoxy, cycloalkoxy or phenoxy group as a leaving group on the silicon atom and which, as other functionality, have a group which, if appropriate after cleavage, can undergo a chemical reaction with the double bonds of the polymer. The last-mentioned group can be, for example, the following chemical groups: — SCN, — SH, — NH2 or — Sx— (where x = 2 to 8).

[0160] Thus, for example, 3-mercaptopropyltriethoxy silane can be used as silane coupling agents, 3- thiocyanato-propyltrimethoxysilane or 3,3 '-bis (triethoxysilylpropyl) polysulfides having 2 to 8 sulfur atoms, such as, for example, 3,3 '-bis (triethoxysilylpropyl) tetrasulfide (TESPT), the corresponding disulfide (TESPD) or other mixtures of the sulfides having 1 to 8 sulfur atoms with different contents of the various sulfides. TESPT can also be added, for example, as a mixture with industrial carbon black (e.g. X50S® from Evonik). Suitable silanes are described in WO 2008 / 083241 A1 , WO 2008 / 083242 A1 , WO 2008 / 083243 A1 and WO 2008 / 083244 A1 . Blocked mercaptosilanes, e.g. as known from WO 99 / 09036, can also be used as silane coupling agents. Commercially available silanes are sold under the name NXT™ Silane by Mo- mentive, or under the name of VP Si 363® by Evonik Industries.

[0161] Further optionally reinforcing fillers are, for example, carbon nanotubes (CNT) including discrete CNTs, so-called hollow carbon fibers (HCF) and modified CNT containing one or more functional groups, such as hydroxy, carboxyl and carbonyl groups), zeolite, graphite and graphenes, and so-called "carbon-silica dual-phase".

[0162] Conventional non-reinforcing fillers such as clays, bentonite, talc, chalk, kaolin, aluminosilicate, starch, magnesium oxide, titanium dioxide may be present as well. In the context of the present invention, further non-reinforcing fillers include also rubber gels and fibers (such as, for example, aramid fibers, glass fibers, carbon fibers, cellulose fibers).

[0163] Plasticizers, which may as well be present, include oils and resins (from petroleum or other natural renewable resources, e.g., sunflower seeds, citrus orange peels). Processing oils are generally extracted from petroleum and are classified as being paraffinic, aromatic or naphthenic type processing oil, including MES and TDAE oils. Processing oils may also include, inter alia, plant-based oils, such as sunflower oil, rapeseed oil and vegetable oil. Some of the rubber compositions disclosed herein may include an elastomer, such as a styrene-butadiene rubber, that has been extended with one or more such processing oils but such oil is limited in the rubber composition of particular embodiments as being no more than 40 phr of the total elastomer content of the rubber composition.

[0164] The rubber composition according to the invention is preferably used in a vulcanized state, in particular in vehicle tires or other vulcanized technical rubber articles.

[0165] The terms "vulcanized" and "crosslinked" are used synonymously in the context of the present invention.

[0166] The vulcanization of the rubber composition according to the present invention is preferably carried out in the presence of sulfur and / or sulfur with the aid of vulcanization accelerators, wherein some vulcanization accelerators can simultaneously act as sulfur donors.

[0167] The accelerator may be selected from the group of thiazole accelerators and / or mercapto accelerators and / or sulfenamide accelerators and / or thiocarbamato accelerators and / or thiuram accelerators and / or thiophosphate accelerators and / or thiourea accelerators and / or xanthate accelerators and / or guanidine accelerators. Other known vulcanization agents may be used as well, as for example, peroxide and ionic crosslinking agents. Vulcanization agents as used herein are those materials that cause the cross-linkage of the rubber and therefore may be added only to the productive mix so that premature curing does not occur, such agents are for example elemental sulfur or sulfur donating agents, as well as peroxides.

[0168] The vulcanization system used may especially be based on sulfur and on an accelerator. Use may be made of any compound capable of acting as an accelerator of the vulcanization of elastomers in the presence of sulfur, in particular those chosen from the group of sulfenamide accelerators comprising for instance benzothiazyl-2-sulphenyl morpholide (MBS), 2-mercaptobenzo- thiazyl disulfide (abbreviated to "MBTS"), N-cyclohexyl-2- benzothiazolesulphenamide (abbreviated to "CBS"), N,N-dicyclohexyl-2- benzothiazolesulphenamide (abbreviated to "DCBS”), N- tert-butyl-2- benzothiazolesulphenamide (abbreviated to "TBBS"), N-tert-butyl-2-benzothiazole- sulphenimide (abbreviated to "TBSI ") and the mixtures of these compounds.

[0169] A primary accelerator of the sulfenamide type may be used as one embodiment of the present invention.

[0170] The rubber composition may also include vulcanization retarders, a vulcanization system based, for example, on sulfur or on a peroxide, vulcanization accelerators, vulcanization activators, and so forth.

[0171] If the rubber composition contains a sulfur-donating substance, it is preferably selected from the group containing, for example, thiuram disulfides, such as, for example, tetrabenzylthiuram disulfide (TBzTD) and / or tetramethylthiuram disulfide (TMTD) and / or tetraethylthiuram disulfide (TETA), and / or thiuram tetrasulfides, such as, for example, dipentamethylenthiuramtetrasulfide (DPTT), and / or dithiophosphates, such as, for example, Didis (bis-(diisopropyl)thiophosphoryl disulfide) and / or bis (O,O-2-ethylhexyl thiophosphoryl) polysulfide (e.g. Rhenocure SDT 50®, Rheinchemie GMBH) and / or zinc dichloroyldithiophosphate (e.g. Rhenocure ZDT / S ®, Rhein- chemie GMBH) and / or zinc alkyldithiophosphate, and / or I, 6-bis (N, N-dibenzylthiocar- bamoyldithio) hexane and / or diaryl polysulfides and / or dialkyl polysulfides.

[0172] Other network-forming systems, such as those obtainable, for example, under the trade names Vulkuren®, Duralink® or Perkalink®, or network-forming systems, as described in WO 2010 / 049216 A2, can also be used in the rubber composition according to the present invention.

[0173] The vulcanization system may further include various known secondary accelerators or vulcanization activators, such as zinc oxide or zinc complexes such as zinc ethylhexanoate, fatty acids (e.g. stearic acid) and guanidine derivatives (in particular diphenylguanidine, or “DPG”). Particular preference is given to the use of the accelerators TBBS and / or CBS and / or diphenylguanidine (DPG).

[0174] The proportion of the total amount of these additives is for instance 3 to 150 phr, particularly 3 to 100 phr and very particularly 5 to 80 phr.

[0175] As a further additive, zinc oxide (ZnO) can be present within the abovementioned amounts.

[0176] These may be all types of zinc oxide known to the person skilled in the art, such as, for example, ZnO granules or powders. The conventionally used zinc oxide generally has a BET surface area of less than 10 m2 / g. However, it is also possible to use a zinc oxide having a BET surface area of 10 to 100 m2 / g, such as, for example, so-called "nano-zinc oxides".

[0177] Furthermore, in addition to the above, the rubber composition according to the present invention may contain customary additives in customary parts by weight, which are preferably added during their preparation in at least one basic mixing stage.

[0178] Such optional general additives include:

[0179] • agents for the binding of fillers, in particular carbon black or silicic acid, such as, for example, S-(3-aminopropyl)thiosulfuric acid and / or metal salts thereof binding to carbon black (silane coupling agents, binding to silica, have been described herein above);

[0180] • ozone protection waxes;

[0181] • resins, in particular adhesive resins for inner tire components;

[0182] • mastication aids, such as, for example, 2,2'-dibenzamidodiphenyl disulfide (DBD);

[0183] • process auxiliaries, such as, in particular, fatty acid esters and metal soaps, such as, for example, zinc soaps and / or calcium soaps; According to particularly advantageous embodiments, the rubber composition according to the invention contains, in addition to the formula I according to the invention, no further anti-ageing agents from the group of p-phenylenediamines.

[0184] In particular, according to one embodiment, the rubber composition according to the invention may contain 0 to 1 phr of further ageing inhibitors based on diamines which are selected from the group containing consisting of N-phenyl-N'-(l, 3-dimethylbutyl)-p-phenylenediamine (6PPD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditolyl-p-phenylenediamine (DTPD), N-isopro- pyl-N'-phenyl-p-phenylenediamine (IPPD), N-(l, 4-dimethylpentyl)-N'-phenyl-p-phenylenedia- mine (7PPD).

[0185] With the preferably very small amounts of the mentioned diamines and the compound according to the invention according to formula (I), it is still possible to achieve a good protective effect. In such case, the compound of the formula (I) according to the invention replaces the mentioned diamines known in the prior art.

[0186] According to a further embodiment of the invention, at least one further one of said diamine ageing inhibitors may also be present, so that the compound according to the invention partially replaces the diamines known in the prior art, which allow for conventional results without losses.

[0187] According to another embodiment, ageing inhibitors based on dihydroquinoline, such as TMQ, may be present in the rubber composition in addition to the compound of formula (I) according to the present invention. The amount of dihydroquinolines present, such as in particular TMQ, is for instance 0.1 to 3 phr, in particular 0.5 to 1 .5 phr.

[0188] A further subject matter of the present invention is a vehicle tire which comprising the rubber composition according to the present invention containing at least one compound of formula (I) as defined herein above.

[0189] The vulcanized vehicle tire has, at least in one component, a vulcanizate of at least one rubber composition according to the invention. It is known to a person skilled in the art that most substances, such as, for example, the rubbers contained, are present in chemically modified form either after mixing or only after vulcanization.

[0190] In the context of the present invention, vehicle tires are understood to be pneumatic vehicle tires and solid rubber tires, including tires for industrial and construction site vehicles, trucks, passenger cars and two-wheel tires. The vehicle tire according to the invention preferably has the rubber composition according to the invention in at least one outer component, wherein the outer component is preferably a tread, a side wall and / or a horn profile.

[0191] The vehicle tire according to the invention can thus comprise the rubber composition according to the present invention containing one or more compound(s) of formula (I) and a plurality of further components as described hereinabove in an optionally adapted composition.

[0192] Methods of production and use of the present invention are described in the following:

[0193] The rubber compositions that are embodiments of the present invention may be produced in suitable mixers in a manner known to those having ordinary skill in the art. Typically, the mixing may occur using two successive preparation phases, a first phase of thermo-mechanical working at high temperature followed by a second phase of mechanical working at a lower temperature.

[0194] The first phase, sometimes referred to as a "non-productive" phase, includes thoroughly mixing, typically by kneading, the various ingredients of the composition but excluding some components of the vulcanization system such as the vulcanization agents, the accelerators, and the retarders. This first phase is carried out in a suitable kneading device, such as an internal mixer of the Banbury type, until under the action of the mechanical working and the high shearing imposed on the mixture, a maximum temperature of generally between 120°C and 190°C is reached, indicating that the components are well dispersed.

[0195] After cooling the mixture, a second phase of mechanical working is implemented at a lower temperature. Sometimes referred to a "productive" phase, this finishing phase consists of incorporating some components of the aforementioned vulcanization system that were not added in the “non-productive” phase, including the vulcanization agents, the accelerators, and the retarders into the rubber composition using a suitable device, such as an open mill. It is performed for an appropriate time (typically, for example, between 1 and 30 minutes or between 2 and 10 minutes), and at a sufficiently low temperature, i.e., lower than the vulcanization temperature of the mixture, so as to protect against premature vulcanization.

[0196] Thus the rubber composition according to the present invention can be formed into useful articles, including tire components. Tire treads, for example, may be formed as tread bands and then later made a part of a tire or they may be formed directly onto a tire carcass by, for example, extrusion and then cured in a mold. Other components such as those located in the bead area of the tire or in the sidewall may be formed and assembled into a green tire and then cured with the curing of the tire. According to a preferred development of the invention, a plurality of accelerators is added in the final mixing stage in the production of the sulfur-crosslinkable rubber composition.

[0197] The sulfur-crosslinkable rubber composition according to the invention is prepared by the process customary in the rubber industry, in which a basic mixture with all constituents other than the vulcanization system (sulfur and vulcanization-influencing substances) is initially produced in one or more mixing stages. The finished mixture is produced by adding the vulcanization system in a last mixing stage. The finished mixture is, for example, used are further processed by an extrusion process or calendering and brought into the corresponding form.

[0198] The further processing is then carried out by vulcanization, wherein a sulfur crosslinking takes place on the basis of the vulcanization system added in the context of the present invention.

[0199] The rubber composition according to the invention described above is particularly suitable for use in vehicle tires, in particular pneumatic vehicle tires.

[0200] For use in vehicle tires, the mixture is preferably introduced as a finished mixture before vulcanization into the form of a tread and applied as is known during the production of the vehicle tire blank.

[0201] The rubber composition according to the invention for use as a side wall or other body mixture in vehicle tires is produced as already described. The difference lies in the shaping after the extrusion process or calendering of the mixture. The resulting forms of the still unvulcanized rubber composition for one or more different body mixtures then serve for the construction of a green tire.

[0202] In this context, the rubber compositions for the inner components of a tire are referred to as the body mixture, such as substantially inner core (inner layer), core profile, belt, shoulder, belt profile, carcass, bead amplifier, bead profile, horn profile and bandage. The still unvulcanized tire blank is then vulcanized.

[0203] For the use of the rubber composition according to the invention in other rubber articles such as belts, in particular in conveyor belts, the extruded or unvulcanized mixture is brought into the corresponding form and is often provided with strength carriers, for example synthetic fibers or steel cords. In most cases, this results in a multi-layer structure consisting of one and / or more layers of rubber composition, one and / or more layers of the same and / or different strength members and one and / or more further layers or the like and / or another rubber composition.

[0204] Consequently, in view of the above, the present invention relates as well to the use of the compound according to formula (I) as an anti-ageing agent and / or antiozonant in vehicle tires and / or technical rubber articles, for instance rubber articles like an air spring, a bellow, a conveyor belt, a hose, a rubber band, a profile, a seal, a membrane, tactile sensors for medical applications or robot applications or a shoe sole or parts thereof.

[0205] EXAMPLES The invention is further illustrated by the following examples, which are to be regarded only as illustrations and not delimitative of the invention in any way. The characterization of the innovative antiozonant molecules and the properties of the rubber compositions disclosed in the examples were evaluated as described below.

[0206] S. Synthesis Example

[0207] The antiozonant compounds according to the present invention were synthetized as described in WO2017 / 040961.

[0208] S.1. Synthesis of 6-methoxy-2,2,4-trimethyl-3,4-dihydro-1 H-1 ,5-naphthyridine (Compound 1.A)

[0209] In a 1 -liter 3 neck round bottom flask equipped with a reflux condenser connected to a nitrogen gas source, a thermocouple, and a magnetic stir bar was dissolved 52.48 g of 5-amino-2-meth- oxypyridine in 500 mL of acetone. To the resultant solution was added 6.8 g of iodine. The resultant mixture was stirred under a nitrogen atmosphere and heated at reflux, internal measured reaction temperature was 60°C. After 14 hr of heating the resultant mixture was cooled to ambient temperature and concentrated under vacuum to give a dark viscous crude oil.

[0210] The crude reaction mixture was dissolved into dichloromethane and passed through a short column of silica gel eluting with dichloromethane to afford 69 g (80% yield) of l,2-dihydro-6-meth- oxy-2,2,4-trimethyl-l ,5-naphthyridine as a yellow oil.

[0211] % NMR (500 MHz, CDCh): 5 1.26 (s, 6H), 2.05 (s, 3H), 3.4 (s, 1 H), 3.86 (s, 3H), 5.49 (s, 1 H), 6.4 (d, 1 H), 6.7 (d, 1 H).

[0212] This reaction is also set forth visually below:

[0213] S.2 Synthesis of 6-methoxy-1 ,2,3, 4-tetrahydro-2, 2, 4-trimethyl-1 ,5-naphthyridine (Compound 1.B)

[0214] In a 600 mL pressure bottle equipped with a magnetic stir bar was dissolved 10 g of 1 ,2-dihy- dro-6-methoxy-2,2,4- trimethyl-l,5-naphthyridine in 30 mL of ethanol. To the resultant solution was added 0.75 g of 10% Pd on carbon as a catalyst using an additional 25 mL of ethanol to ensure complete transfer of the catalyst to the flask. The resultant mixture was purged with nitrogen and was reacted under a hydrogen pressure of 20 to 40 psi until no further hydrogen was absorbed. The reaction mixture was purged with nitrogen and the catalyst removed by filtration. The filtrate was concentrated under vacuum to afford 9.93 g (98% yield) of 6-methoxy-l ,2,3,4- tetrahydro-2,2,4- trimethyl-l,5-naphthyridine as a light amber oil.

[0215] % NMR (500 MHz, CDCh): 5 1.17 (s, 3H), 1.24 (s, 3H), 1.39 (d, 3H), 1.5 (t, 1 H), 1.84 (dd, 1 H), 2.93 (m, 1 H), 3.05 (s, 1 H), 3.87 (s, 6.41 (d, 1 H), 6.76 (d, 1 H). MS: m / z=207 (M)+.

[0216] This reaction is also set forth visually below: formula (I.B)

[0217] After formation, the antiozonant of formula (LB) obtained in synthesis example S.2 is tested for its antiozonant efficacy in examples below.

[0218] The results are set forth as well below.

[0219] T. Testing Examples

[0220] Several test systems are available in order to evaluate the efficacy and the effectivity of antiozonants.

[0221] For instance, antiozonant migration and antiozonation longevity tests may be assessed by grading the surface ozone cracks on a prepared rubber sample (partially comprising and partially not comprising an antiozonant) after exposure to ozone environment, e.g.in an ozone chamber for a specified duration. The migration rate in this process is dependent on various factors such as the molecular size of the antiozonant, the solubility and affinity of the antiozonant in the rubber formulation matrix, as well as the environmental conditions.

[0222] T.1. Testing of antioxidant activity in synthetic raw rubber via viscosity measurement (Minimum Mooney viscosity ML measured before and after heat aging according to ISO 289- 1 :2014.)

[0223] The Mooney Viscosity test is the most popular test method for characterizing polymers and uncured rubber materials and the Mooney viscosity value is one of the important indexes to evaluate the processing performance of rubbers, as it is closely related to plasticity. Lower Mooney viscosity indicates the better fluidity of a rubber compound, low molecular weight and good plasticity, whereas a higher viscosity value indicates that the rubber has a high molecular weight and poor plasticity. As defined by international standards, the sample material is preheated for a defined period in a closed die cavity, then sheared by the embedded rotor at a constant rate. The Mooney Viscosity is recorded, and data are calculated at predefined time and viscosity points. In elastomer and tire research, a Mooney Viscometer testing method is used for measuring torque. Whereas Ml (Initial Torque) is the torque recorded at time zero at the start of the test As the compound heats under shear, the viscosity decreases and the torque decreases. The lowest registered Torque value is called ML. Basically, it is a measure of the rigidity and viscosity of the non-vulcanized rubber compound. ML is represented as ML(1+4) at 100 deg C, which indicates the final torque at 100 degree C° after 4 minutes of testing with 1 min preheating time using large rotor.

[0224] Materials used:

[0225] ESBR Rubber: SBR 1502 emulsion from Petrochina Jiling (cold polymerized, 23.5% styrene SBR polymer made with a mixed-acid emulsifier and a non-staining stabilizer)

[0226] Compound 1 .B: Inventive antiozonant AOz (6-methoxy-1 ,2,3,4-tetrahydro-2,2,4-trimethyl-1 ,5- naphthyridine)

[0227] Irganox® 5057: Comparative antioxidant AOx-1 (Benzenamine, N-phenyl-, reaction products with 2,4,4-trimethylpentene)

[0228] Irganox® 1076: Comparative antioxidant AOx-2 (Octadecyl-3-(3,5-di-te / Y-butyl-4-hydroxy- phenyl)-propionate)

[0229] Irganox® 1520: Comparative antioxidant AOx-3 (4,6-bis(octylthiomethyl)-o-cresol)

[0230] 6PPD: Comparative antiozonant AOz-1 (N-(1 ,3-dimethylbutyl)-N'-phenyl-p-phe- nylenediamine)

[0231] Sirantox EPPD: Comparative antiozonant mixture AOz- 2 (mixture of 6PPD and 7PPD (N-(1 ,4- dimethylpentyl)-N'-phenyl-p-phenylenediamine, commercially available from Sinochem)

[0232] Sample preparation:

[0233] The respective rubber stabilizers as outlined in Table 1 were added to an emulsion of SBR 1502 and mixed thoroughly. After coagulation, the raw rubber was dried and kneaded on a two-roll mill to yield a flat piece of raw rubber which was then subjected to oven aging with determination of the Mooney Viscosity before and after aging.

[0234] Test conditions:

[0235] 1. Oven aging condition: 100°C, 72 hours

[0236] 2. Measurement conditions:

[0237] • Sample size: Diameter 50mmxThickness 6mm • Rotor size: Diameter 38.1 mm ; Thickness 5.54mm

[0238] • Test temperature: 100°C

[0239] • Preheating time: 1 min

[0240] • Runtime: 4min

[0241] • Equipment: Gotech MV-3000VS

[0242] Results

[0243] The individual test results are listed in the tables below.

[0244] Table T.1.a: Minimum Mooney viscosity of ESBR before and after heat aging at 100°C for 72 hours without rubber stabilization and with rubber stabilization with inventive compound 1 .B b)blank example; inventive example;

[0245] Table T.1.b: Minimum Mooney viscosity of ESBR before and after heat aging at 100°C for 72 hours with rubber stabilization with various antioxidants c)comparative example;

[0246] Table T.1.c: Minimum Mooney viscosity of ESBR before and after heat aging at 100°C for 72 hours with rubber stabilization with alternative antiozonants c)comparative example; The results from Table T.1a in comparison to tables T.1 b and T.1.c show that inventive Compound 1.B (example 1.1g) can effectively stabilize the uncured rubber against degradation under heat exposure, as expressed by the significantly reduced alteration of the Mooney viscosity before and after heat exposure, compared to the rubber without additional rubber stabilizer (example B.1a), and also better than I or on similar level as traditional antioxidants in table T.1 b.

[0247] Preferably, the viscosity of the raw rubber is maintained at its original level during the heat aging experiment, i.e. no increase or decrease of the viscosity is observed. Stabilizers yielding the lowest alteration of the minimum Mooney viscosity measured before and after heat exposure are the most effective stabilizers, protecting the raw rubber from both, degradation and premature crosslinking.

[0248] T.2. Testing of antioxidant activity in synthetic raw rubber via color measurement (Yellowness Index (Yl) according to ISO 17223:2014 before and after heat aging)

[0249] Sample preparation:

[0250] Flat raw rubber pieces containing the rubber stabilizers indicated in Table T.2 were obtained following the procedure outlined in Example 1 above.

[0251] Test conditions:

[0252] 1. Oven aging condition: 100°C, 7 days

[0253] 2. Measurement conditions:

[0254] • Sample size : 6cmx5cmx0.2cm

[0255] • Equipment: Colorimeter CI60

[0256] • Test light source : CIE standard light source D65

[0257] • Color System : L*a*b

[0258] Results

[0259] The individual test results are listed in tables below.

[0260] Table T.2.a: Yellowness Index of ESBR before and after heat aging at 100°C for 7 days with no rubber stabilizer and with inventive antiozonant compound 1 .B b> blank example;

[0261] ') inventive example; Table T.2.b: Yellowness Index of ESBR before and after heat aging at 100°C for 7 days with comparative antioxidants c> comparative example;

[0262] Table T.2.c: Yellowness Index of ESBR before and after heat aging at 100°C for 7 days with comparative antioxidants c> comparative example;

[0263] The values in Table T.2.a to T.2.c represent the average Yl of 2 samples per formulation. The initial color of samples stabilized with EPPD and 6PPD was very dark (table T.2.c). It was therefore not feasible to assess their color change by Yl index. The results show that Compound 1 .B (example 1.2g) yields a rubber composition of comparably low initial color compared to 6PPD and Sirantox EPPD (examples C.2e and C.2f). Furthermore, Compound 1.B (example 1.2g) is able to stabilize the rubber composition against discoloration under heat exposure, resulting in lower discoloration (Delta Yl) than most of the other tested additives, even in comparison to known antioxidants (table T.2.b).

[0264] T.3 Testing of antiozonant activity in cured synthetic rubber (Testing of resistance to static ozone cracking according to ISO 1431-1 :2012)

[0265] ISO 1431-1 :2012 specifies procedures intended for use in estimating the resistance of vulcanized or thermoplastic rubbers to cracking when exposed, under static (or dynamic) tensile strain, to air containing a definite concentration of ozone and at a definite temperature in circumstances that exclude the effects of direct light.

[0266] Visual observation and / or image analysis are used to evaluate the formation and growth of cracks. The changes in physical or chemical properties resulting from exposure can also be determined. Sample preparation:

[0267] Test specimens of cured ESBR were prepared according to the procedures specified in ASTM D 3186.

[0268] The formula for the preparation of the ESBR compounds is as below :

[0269] Testing of resistance to static ozone cracking was performed according to ISO 1431-1 :2004 in an ozone chamber with an ozone concentration of (50±5)x108parts per volume at (40±2) °C, a relative humidity of max. 65% and a strain of 20%. Specimen were evaluated after 72 h testing time. 3 specimens were tested per formulation.

[0270] Results

[0271] The individual test results are listed in tables below.

[0272] Table T.3.a: Results of static ozone cracking test with no rubber stabilizer and with inventive antiozonant compound 1.B b)blank example;

[0273] ') inventive example;

[0274] Table T.3.b: Results of static ozone cracking test with comparative antioxidants c)comparative example; Table T.3.c: Results of static ozone cracking test with comparative antiozonants c)comparative example Tables T.3.a to T.3.c show the results of ozone degradation protection from different compounds tested for their antiozonant activity on cured SBR. The protective effects against ozone are clearly improved by the use of inventive compound 1.B (example 1.3d) compared to a combination of Irganox® 1520 and Irganox® 5057 (example C.3.a), which showed an excellent antioxidant performance in previous tests T.1 and T.2, and hereby demonstrating that a high antiox- idant efficiency does not correlate with a relevant antiozonant performance. Therefore, the antiozonant effect obtained with Compound 1.B is surprising and could not have been expected.

Claims

CLAIMS1 . A rubber composition comprising an antiozonant compound formula (I)whereinX is each either selected from N or a group C-A, wherein at least one of X is N, but no more than two of X are N; and whereinA is H, CN or an electron donating group, which is either an oxygen atom or nitrogen atom that is bonded directly to the aromatic ring; or is an aryl group or C-i-C2o-alkyl, C-i-C2o-alkenyl or Ci-C20-alkoxy group; andR1, R1’, R2, R2are each, independently from one another, selected from group consisting of hydrogen, an Ci-C20-alkyl group, Ci-C20-alkenyl or an aryl group, and wherein one of R1or R1and one of R2or R2' may optionally form together a double bond; andR3, R3are independently from one another selected from an Ci-C20-alkyl group,Ci-C20-alkenyl or aryl group.

2. The rubber composition according to claim 1 , wherein said antiozonant is of the following two structures of formula (II.1a) or formula (II.1 b):The rubber composition according to claim 2, wherein in formula (II.1a) or (II.1b):R1is hydrogen or methyl, preferably methyl;R2is hydrogen or methyl, preferably hydrogen; andR3, R3are both selected independently from one another from a Ci-C8-alkyl group, preferably a Ci-C4-alkyl group, most preferably both are methyl.The rubber composition according to claim 1 , wherein said antiozonant is of the following two structures of formula (II.2a) or formula (Il2.b):The rubber composition according to claim 4, wherein in formula (ll.2a) or (ll.2.b):R1, R1are both selected independently from one another from either hydrogen or a C-i-Cs-alkyl group, preferably a Ci-C4-group, most preferably one is hydrogen and the other is methyl;R2, R2are both selected independently from one another from either hydrogen or a C-i-Cs-alkyl group, preferably a Ci-C4-group, most preferably both are hydrogen; andR3, R3are both selected independently from one another from a Ci-C8-alkyl group, preferably a Ci-C4-alkyl, most preferably both are methyl.

6. The rubber composition according to any one of claims 1 to 5, wherein in formula (II.1a), (II.1 b) ,(ll.2a) or (II.2b) one of X is nitrogen and the other is C-A.

7. The rubber composition according to claim 6, wherein in formula (II.1a), (II.1 b) ,(H2.a) or (II.2b) one of X is nitrogen and the other is CH.

8. The rubber composition according to any one of claims 1 to 6, wherein at least one of the electron donating groupsA has an oxygen atom or nitrogen atom that is bonded directly to the aromatic ring.

9. The rubber composition according to claim 8, whereinA is selected from -NH2, -NHR4-NR42or -NHCOR4, whereineach R4is independently from one another selected from a Ci-C8-alkyl group, preferably Ci-C4-alkyl, most preferably A is -NH2.

10. The rubber composition according to claim 8, whereinA is selected from -OH, -OR4or-OCOR4, whereinR4is C-i-Cs-alkyl, preferably Ci-C4-alkyl, most preferably wherein A is hydroxy, methoxy or ethoxy.11 . The rubber composition according to any one of claims 1 to 5, wherein both X in formula (II.1a), (II.1 b), (II.2a) or (II.2b) represent nitrogen.

12. The rubber composition according to any one of the preceding claims, which contains a diene rubber, a reinforcing filler, a plasticizer and / or a vulcanization system.

13. The rubber composition according to any one of the preceding claims, which contains at least a highly unsaturated diene rubber selected from the group consisting of natural rubber, isoprene rubber, styrene-butadiene, polybutadiene, natural polyisoprene (NR), synthetic polyisoprene (IR), butadiene rubber (BR), solution polymerized styrene-butadiene rubber (SSBR), emulsion polymerized styrene-butadiene rubber (ESBR), butyl rubber (HR), and halobutyl rubber and any combinations thereof.

14. The rubber composition according to any one of the preceding claims, which contains a reinforcing filler selected from the group consisting of carbon blacks, silicas, graphene, graphite, and combinations thereof.

15. The rubber composition according to any one of the preceding claims, which contains a plasticizer selected from the group consisting of oils, resins, and combinations thereof.

16. The rubber composition according to any one of the preceding claims, which contains a vulcanization system comprising sulfur and an accelerator.

17. The rubber composition according to any one of the preceding claims, wherein the amount of the antiozonant is between 0.2 to 10 phr, preferably between 0.5 to 3 phr.

18. A vehicle tire comprising the rubber composition according to any one of claims 1 to 17 in at least one component.

19. A vehicle tire according to claim 18, wherein the rubber composition is comprised in one outer component, and wherein the outer component is preferably a tread, a side wall and / or a rhombus.

20. Use of the compound according to formula (I) as defined in claim 1 as an anti-ageing agent and / or antiozonant in vehicle tires and / or technical rubber articles.21 . The use according to claim 20, wherein the rubber article is an air spring, bellow, conveyor belt, hose, rubber band, profile, a seal, a membrane, tactile sensors for medical applications or robot applications or a shoe sole or parts thereof.

22. The use according to claim 20 or 21 as antiozonant.

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