Antioxidant composition having good ozone aging resistance, and rubber composition and use thereof

Abstract

Provided in the present invention are an antioxidant composition comprising two or more compounds of formula A, a rubber composition comprising the antioxidant composition, and the use of the rubber composition. The compounds of formula A are as described in the specification. The antioxidant composition of the present invention can significantly improve the static ozone aging resistance and dynamic ozone aging resistance of a tire rubber material, and the other properties thereof such as thermo-oxidative aging resistance can also be kept consistent with existing comprehensive antioxidants.

Description

Antioxidant composition with excellent ozone aging resistance, rubber composition and use thereof Technical Field

[0001] The present invention belongs to the field of rubber materials, and in particular relates to an antioxidant composition with excellent ozone aging resistance, a rubber composition and uses thereof. Background Art

[0002] With the development of society and the advancement of the automotive industry, the requirements for automobile tires are becoming increasingly stringent. Tires are a type of rubber product. During processing, storage, and use, rubber materials are exposed to various factors such as light, oxygen, ozone, high temperatures, and chemical corrosion, causing their structure to change and gradually lose their original excellent properties. This is the aging phenomenon of rubber. Rubber containing double bonds and its products are particularly susceptible to ozone aging when used or stored in an environment containing ozone. Ozone aging can manifest as cracks and fissures on the surface of the material or product perpendicular to the direction of stress; a gradual decrease in mechanical properties such as tensile strength and elongation; and a reduction in performance. To address this issue, antioxidants are added to tires to mitigate the various aging effects on their performance. Existing tire antioxidants primarily consist of aniline, quinoline, and triazine structures.

[0003] Tires are attacked by ozone in the air, causing cracks to form while they are stationary or in motion. This can occur while tires are stored in warehouses. Such cracks can affect the tire's appearance and performance, rendering it unsalable and unusable. These tiny cracks in vehicle tires can expand and become failure points during subsequent use, shortening the tire's lifespan and even causing accidents during driving. Existing comprehensive antioxidants offer balanced protection across various performance attributes, but are less effective in ozone protection.

[0004] Summary of the Invention

[0005] To address the problems of the prior art, the present invention provides an antioxidant composition comprising two or more compounds of Formula A, a rubber composition containing the antioxidant composition, and uses thereof. The combined use of two or more compounds of Formula A can significantly improve the static and dynamic ozone aging resistance of tire rubber materials, while maintaining other properties, such as resistance to thermal oxidative aging, consistent with existing comprehensive antioxidants. This helps effectively address ozone aging in tires, thereby extending tire service life and improving tire safety during use.

[0006] Specifically, one aspect of the present invention provides an antioxidant composition, which comprises two or more compounds of formula A:

[0007] In formula A, R1 and R2 are each independently selected from a C1-C8 alkyl group.

[0008] In one or more embodiments, in Formula A, R1 is selected from C1-C2 alkyl, and R2 is selected from C3-C6 alkyl.

[0009] In one or more embodiments, the antioxidant composition comprises two or more compounds selected from the group consisting of a compound of formula I, a compound of formula II, a compound of formula IV, a compound of formula V, a compound of formula VII, and a compound of formula VIII:

[0010] In one or more embodiments, the antioxidant composition comprises a compound of formula I and a compound of formula II, or comprises a compound of formula IV and a compound of formula V, or comprises a compound of formula VII and a compound of formula VIII.

[0011] In one or more embodiments, in the antioxidant composition, the mass ratio of the compound of formula I to the compound of formula II, the mass ratio of the compound of formula IV to the compound of formula V, or the mass ratio of the compound of formula VII to the compound of formula VIII is 1:4 to 4:1.

[0012] Another aspect of the present invention provides a rubber composition, wherein the raw materials of the rubber composition include 100 parts by mass of a diene elastomer and 1-5 parts by mass of the antioxidant composition according to any embodiment of the present invention.

[0013] In one or more embodiments, the raw materials of the rubber composition include 2-3 parts by mass of the antioxidant composition.

[0014] In one or more embodiments, the diene elastomer comprises natural rubber and butadiene rubber; preferably, the mass ratio of the natural rubber to the butadiene rubber is from 1:2 to 2:1.

[0015] In one or more embodiments, the raw materials of the rubber composition further include 30-70 parts by mass of a reinforcing filler; preferably, the reinforcing filler is carbon black.

[0016] In one or more embodiments, the raw materials of the rubber composition further include 1-10 parts by mass of an active agent; preferably, the active agent is zinc oxide.

[0017] In one or more embodiments, the raw materials of the rubber composition further include 2-15 parts by mass of a softener; preferably, the softener includes aromatic oil and stearic acid in a mass ratio of 1:1 to 5:1.

[0018] In one or more embodiments, the raw materials of the rubber composition further include 0.5-3 parts by mass of sulfur.

[0019] In one or more embodiments, the raw materials of the rubber composition further include 0.2-2 parts by mass of an accelerator, and the accelerator is preferably N-tert-butyl-2-benzothiazolesulfenamide.

[0020] Another aspect of the present invention provides a rubber product, comprising the rubber composition described in any embodiment herein; preferably, the rubber product is a tire.

[0021] The present invention also provides use of the antioxidant composition as described in any embodiment herein in improving the ozone aging resistance of a rubber composition or a rubber product. DETAILED DESCRIPTION

[0022] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0023] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0024] Herein, “comprising,” “including,” “containing” and similar terms encompass the meanings of “consisting essentially of” and “consisting of,” for example, when “A comprises B and C” is disclosed herein, “A consists essentially of B and C” and “A consists of B and C” should be deemed to have been disclosed herein.

[0025] Throughout this document, all features, such as values, amounts, amounts, and concentrations, specified in numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible subranges and individual values ​​within those ranges (including integers and fractions).

[0026] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0027] Herein, when describing embodiments or examples, it should be understood that they are not intended to limit the present invention to these embodiments or examples. On the contrary, all alternatives, modifications and equivalents of the methods and materials described herein are encompassed within the scope defined by the claims.

[0028] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0029] The present invention discovers that the combined use of two or more compounds of Formula A, particularly the combination of Formula I and Formula II, the combination of Formula IV and Formula V, and the combination of Formula VII and Formula VIII, in a rubber composition, particularly a tire rubber composition, can significantly improve the ozone aging resistance of the rubber composition during both static and dynamic conditions, thereby extending its service life and enhancing safety during use. Compared to using either the antioxidant 6PPD or a single compound of Formula A alone, the combined use of two or more compounds of Formula A, particularly the combination of Formula I and Formula II, the combination of Formula IV and Formula V, and the combination of Formula VII and Formula VIII, exhibits an unexpected synergistic effect in improving the ozone aging resistance of the rubber composition.

[0030] In the present invention, the compound of formula A has the following structure:

[0031] In formula A, R1 and R2 are each independently selected from a C1-C8 alkyl group.

[0032] As used herein, an alkyl group refers to a linear or branched monovalent saturated hydrocarbon group containing 1 to 8 carbon atoms (C1-C8 alkyl). Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, 1-methylpropyl, isobutyl, 1-methylbutyl, and 1,3-dimethylbutyl.

[0033] In some embodiments, in Formula A, R1 is selected from C1-C4 alkyl, such as C1-C2 alkyl.

[0034] In some embodiments, in formula A, R2 is selected from C3-C6 alkyl, such as isopropyl, 1-methylpropyl, 1-methylbutyl, 1,3-dimethylbutyl, preferably selected from C4-C6 alkyl.

[0035] In some preferred embodiments, in formula A, R1 is selected from C1-C2 alkyl; R2 is selected from C3-C6 alkyl or C4-C6 alkyl, for example, selected from isopropyl, 1-methylpropyl, 1-methylbutyl, 1,3-dimethylbutyl.

[0036] In the present invention, the compound of formula A can be prepared by a method comprising the following steps:

[0037] (1) subjecting a compound of formula B to a condensation reaction with nitrobenzene in the presence of a first catalyst to obtain a condensate comprising a compound of formula C and / or a compound of formula C′, and then subjecting the condensate to a reduction reaction in the presence of H2 and a second catalyst to obtain a compound of formula D;

[0038] (2) subjecting the compound of formula D to a reductive alkylation reaction with the compound of formula E in the presence of H2 and a third catalyst to obtain a compound of formula A;

[0039] R1 and R2 in Formula A, Formula B, Formula C, and Formula D can be as described in any embodiment herein, and R3 and R4 in Formula E are each independently selected from H and C1-C7 alkyl. Those skilled in the art can determine the appropriate R4 and R5 in Formula F based on R3 contained in the compound of Formula A.

[0040] The first catalyst used in step (1) can be one or more selected from alkali metal hydroxides, alkali metal alkoxides, quaternary ammonium bases, and combinations of alkali metal hydroxides and tetraalkylammonium halides. Suitable alkali metal hydroxides for use in the present invention include sodium hydroxide, potassium hydroxide, lithium hydroxide, and the like. Suitable alkali metal alkoxides for use in the present invention include sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, potassium tert-butoxide, sodium tert-amyl alcoholate, potassium tert-amyl alcoholate, and the like. Quaternary ammonium bases are a class of compounds with the general formula R 1 4NOH compound, wherein R is four identical or different aliphatic or aromatic groups. 1 It can be selected from one or more of methyl, ethyl, propyl, butyl, etc. Examples of quaternary ammonium bases suitable for the present invention include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, etc. The first catalyst can also be a combination of an alkali metal hydroxide and a tetraalkylammonium halide. The general formula of the tetraalkylammonium halide is R 2 4NX, where R 2 are four identical or different aliphatic or aromatic hydrocarbon groups, such as methyl, ethyl, propyl, butyl, etc., and X is a halogen atom, such as fluorine, chlorine, bromine, or iodine. Examples of the combination of an alkali metal hydroxide and a tetraalkylammonium halide include sodium hydroxide and tetrabutylammonium bromide.

[0041] The molar ratio of the first catalyst to the compound of formula B can be 0.1:1 to 2:1, preferably 0.9:1 to 1.1:1, for example 1.05:1, 1.1:1, or 1.5:1. In some embodiments, in step (1), the compound of formula B and the first catalyst are first salted, and then nitrobenzene is added dropwise to carry out a condensation reaction.

[0042] In step (1), the condensation product obtained by the condensation reaction of the compound of formula B with nitrobenzene under the action of the first catalyst may be one or both of the compound of formula C and the compound of formula C', and may also contain an azobenzene compound.

[0043] In step (1), the molar ratio of the compound of formula B to nitrobenzene can be 2:1 to 15:1, preferably 4:1 to 10:1, more preferably 5:1 to 8:1, for example 6:1, 7:1.

[0044] In step (1), the condensation reaction can be carried out at 40-90° C., preferably 65-85° C., for example, the reaction temperature can be 60° C., 70° C., 75° C., or 80° C. The condensation reaction needs to be carried out under vacuum conditions, with a pressure range of -0.09 to -0.1 MPa.

[0045] The second catalyst used in step (1) can be a porous metal catalyst or a supported metal catalyst. Porous metal catalysts are also called sponge metal catalysts. Porous metal catalysts suitable for the present invention include Raney nickel (also known as skeleton nickel), Raney cobalt, Raney copper, etc. Supported metal catalysts include a metal as a catalytic active center and a carrier for supporting the metal. The metal in the supported metal catalyst suitable for the present invention can be nickel, cobalt, copper, platinum, palladium, ruthenium, rhodium, etc., and the carrier can be carbon, alumina, silica gel, molecular sieve, etc., and the carbon used as the carrier can be activated carbon. The ratio of the amount of metal in the second catalyst to the amount of the condensate can be 0.0001:1 to 0.2:1.

[0046] In step (1), the condensate generated by the condensation reaction is subjected to a hydrogenation reduction reaction in the presence of a second catalyst to produce a compound of formula D. In step (1), the reduction reaction can be carried out at 40 to 120° C., preferably 60 to 90° C., for example, the reaction temperature can be 70° C., 75° C., or 80° C. The hydrogen pressure during the reduction reaction can be 0.5 to 5 MPa, for example, 1 MPa, 1.5 MPa, 2 MPa, or 2.5 MPa.

[0047] In step (1), the compound of formula B itself can be used as a solvent, or solvents such as toluene and xylene can be used. After the reaction in step (1) is completed, the reaction solution is filtered, washed with water, and phase separated, and the organic phase is distilled under reduced pressure to remove light components to obtain the compound of formula D.

[0048] The third catalyst used in step (2) can be the aforementioned supported metal catalyst, such as Pt / C. The molar ratio of the metal in the third catalyst to the compound of formula D can be 0.0001:1 to 0.2:1.

[0049] In step (2), after the reaction, the carbonyl carbon atom in the compound of formula E is connected to the amino nitrogen atom in the compound of formula D. Therefore, a suitable compound of formula E can be selected for reaction according to the R3 group contained in the compound of formula A to be prepared. The molar ratio of the compound of formula E to the compound of formula D can be 1:1 to 15:1, for example, 2:1, 3:1, 5:1, 8:1, 10:1. The reaction temperature of step (2) can be 40 to 150°C, for example, 50°C, 80°C, 100°C, or 120°C. The hydrogen pressure in step (2) can be 0.5 to 5 MPa, for example, 1 MPa, 1.5 MPa, 2 MPa, or 2.5 MPa.

[0050] In step (2), the compound of formula E, which is a reaction raw material, can be used as a solvent. After the reaction in step (2) is completed, the reaction solution is filtered and the light components are removed by vacuum distillation to obtain the compound of formula A.

[0051] In the present invention, liquid chromatography (LC) or gas chromatography (GC) can be used to determine whether each step of the reaction has reached the endpoint, thereby determining the appropriate reaction time.

[0052] The antioxidant composition of the present invention comprises two or more compounds of formula A, or consists of two or more compounds of formula A.

[0053] In some embodiments, the antioxidant composition of the present invention comprises two or more compounds selected from the group consisting of compounds of formula I, compounds of formula II, compounds of formula IV, compounds of formula V, compounds of formula VII, and compounds of formula VIII:

[0054] In some embodiments, the antioxidant composition of the present invention comprises two compounds of formula A, or consists of two compounds of formula A; the mass ratio of the two compounds of formula A can be 1:4 to 4:1, for example, 1:3, 1:2, 1:1.5, 1:1, 1.5:1, 2:1, 3:1.

[0055] In some preferred embodiments, the antioxidant composition comprises, or consists of, a compound of Formula I and a compound of Formula II. In the antioxidant composition of the present invention, the mass ratio of the compound of Formula I to the compound of Formula II is preferably 1:4 to 4:1, for example, 1:3, 1:2, 1:1.5, 1:1, 1.5:1, 2:1, or 3:1. Controlling the mass ratio of the compound of Formula I to the compound of Formula II within the aforementioned range facilitates the synergistic effect of the two compounds in improving the ozone aging resistance of the rubber composition.

[0056] In other preferred embodiments, the antioxidant composition comprises, or consists of, a compound of Formula IV and a compound of Formula V. In the antioxidant composition of the present invention, the mass ratio of the compound of Formula IV to the compound of Formula V is preferably 1:4 to 4:1, for example, 1:3, 1:2, 1:1.5, 1:1, 1.5:1, 2:1, or 3:1. Controlling the mass ratio of the compound of Formula IV to the compound of Formula V within the aforementioned range facilitates the synergistic effect of the two compounds in improving the ozone aging resistance of the rubber composition.

[0057] In other preferred embodiments, the antioxidant composition comprises, or consists of, a compound of formula VII and a compound of formula VIII. In the antioxidant composition of the present invention, the mass ratio of the compound of formula VII to the compound of formula VIII is preferably 1:4 to 4:1, for example, 1:3, 1:2, 1:1.5, 1:1, 1.5:1, 2:1, or 3:1. Controlling the mass ratio of the compound of formula VII to the compound of formula VIII within the aforementioned range facilitates the synergistic effect of the two compounds in improving the ozone aging resistance of the rubber composition.

[0058] The raw materials of the rubber composition generally include a diene elastomer, a reinforcing filler, an antioxidant, and a cross-linking agent. Herein, the rubber composition includes unvulcanized rubber and vulcanized rubber. The unvulcanized rubber can be vulcanized (cured) to produce vulcanized rubber.

[0059] The raw material of rubber combination of the present invention comprises diene elastomer and antioxidant composition of the present invention, wherein, take the consumption of diene elastomer as 100 mass parts, the consumption of antioxidant composition of the present invention can be 1-5 mass parts, is preferably 1-4 mass parts, for example 1.5 mass parts, 2 mass parts, 2.5 mass parts, 3 mass parts, 3.5 mass parts.The consumption of antioxidant composition of the present invention is controlled within the aforementioned range to be conducive to ensuring the effect of improving ozone aging resistance under lower consumption.Herein, if not otherwise specified, take the quality of diene elastomer in the raw material of rubber combination as 100 mass parts as benchmark to calculate the mass parts of other components in rubber combination raw material.

[0060] Herein, diene elastomer refers to an elastomer whose monomers include dienes (such as butadiene, isoprene). Suitable diene elastomers for use in the present invention can be various diene elastomers known in the art, including but not limited to one or more selected from natural rubber (NR), butadiene rubber (BR), isoprene rubber, styrene-butadiene rubber (SBR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), isoprene / butadiene copolymer, isoprene / styrene copolymer and isoprene / butadiene / styrene copolymer. In some preferred embodiments, the diene elastomer includes natural rubber and butadiene rubber, or is composed of natural rubber and butadiene rubber. The mass ratio of natural rubber and butadiene rubber is preferably 1: 2 to 2: 1, for example 1: 1.5 to 1.5: 1, 4.5: 5.5 to 5.5: 4.5, 1: 1.

[0061] The antioxidant contained in the rubber composition of the present invention includes the antioxidant composition of the present invention. In some embodiments, the rubber composition of the present invention does not contain other antioxidants except the antioxidant composition of the present invention. In the raw materials of the rubber composition of the present invention, the consumption of the antioxidant composition of the present invention can be 1-5 mass parts, preferably 1-4 mass parts, such as 1.5 mass parts, 2 mass parts, 2.5 mass parts, 3 mass parts, 3.5 mass parts, more preferably 2-3 mass parts.

[0062] The raw material of rubber combination of the present invention can include reinforcing filler.In the raw material of rubber combination of the present invention, the consumption of reinforcing filler can be 30-70 mass parts, for example 40 mass parts, 45 mass parts, 50 mass parts, 55 mass parts, 60 mass parts.Be applicable to reinforcing filler of the present invention can be the conventional reinforcing filler for rubber combination, includes but not limited to be selected from one or more in carbon black, white carbon black, titanium oxide, calcium carbonate, magnesium carbonate, aluminium hydroxide, magnesium hydroxide, clay and talcum.In some preferred embodiments, reinforcing filler comprises carbon black, or reinforcing filler is carbon black.

[0063] The raw materials of the rubber composition of the present invention include a crosslinking agent, such as sulfur. The amount of sulfur in the raw materials of the rubber composition of the present invention can be 0.5-3 parts by mass, such as 1 part by mass, 1.5 parts by mass, 2 parts by mass, or 2.5 parts by mass.

[0064] The raw materials of the rubber composition of the present invention may further include other ingredients commonly used in rubber compositions, including but not limited to one or more selected from the group consisting of softeners, protective waxes, active agents, and accelerators.

[0065] Softeners can be used to improve the processing properties of the rubber composition. Softeners can include petroleum softeners such as naphthenic oil, aromatic oil, process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, vaseline, etc., and can also include fatty oil softeners such as stearic acid, castor oil, linseed oil, rapeseed oil, coconut oil, waxes (such as beeswax, carnauba wax and lanolin), tall oil, linoleic acid, palmitic acid, lauric acid, etc. In the raw materials of the rubber composition of the present invention, the amount of softener used can be 2-15 parts by mass, for example, 3 parts by mass, 5 parts by mass, 7 parts by mass, 8 parts by mass, 9 parts by mass, 10 parts by mass, 11 parts by mass, or 13 parts by mass. In some preferred embodiments, the softener includes aromatic oil and stearic acid, or consists of aromatic oil and stearic acid. The mass ratio of aromatic oil to stearic acid can be 1:1 to 5:1, for example, 2:1, 2.5:1, 3:1, 3.5:1, or 4:1. In some preferred embodiments, in the raw materials of the rubber composition of the present invention, the amount of aromatic oil is 1-10 parts by mass, for example, 2 parts by mass, 3 parts by mass, 4 parts by mass, 5 parts by mass, 6 parts by mass, 7 parts by mass, 8 parts by mass, and 9 parts by mass; the amount of stearic acid is 1-5 parts by mass, for example, 1.5 parts by mass, 2 parts by mass, 2.5 parts by mass, 3 parts by mass, and 4 parts by mass.

[0066] The protective wax can migrate from the interior of the rubber to the surface to form a wax film, thereby isolating the rubber surface from the external environment. The protective wax is optionally added. When the raw materials of the rubber composition of the present invention include the protective wax, the amount of the protective wax can be 1-5 mass parts, for example, 1.5 mass parts, 2 mass parts, 3 mass parts, or 4 mass parts.

[0067] The activating agent can play the effects such as accelerating vulcanization speed, improving rubber thermal conductivity, wear resistance, tear resistance.In the raw material of the rubber composition of the present invention, the consumption of the activating agent can be 1-10 mass parts, for example, 2 mass parts, 3 mass parts, 4 mass parts, 5 mass parts, 6 mass parts, 7 mass parts, 8 mass parts, 9 mass parts.In some preferred embodiments, the activating agent includes ZnO, or the activating agent is ZnO.In some preferred embodiments, in the raw material of the rubber composition of the present invention, the consumption of ZnO is 3-8 mass parts, for example, 4 mass parts, 5 mass parts, 6 mass parts, 7 mass parts.

[0068] Accelerator is generally a vulcanization accelerator, and can be selected from one or more of sulfonamide vulcanization accelerator, thiazole vulcanization accelerator, thiuram vulcanization accelerator, thiourea vulcanization accelerator, guanidine vulcanization accelerator, dithiocarbamate vulcanization accelerator, aldehyde amine vulcanization accelerator, aldehyde ammonia vulcanization accelerator, imidazoline vulcanization accelerator and xanthate vulcanization accelerator. In the raw material of the rubber composition of the present invention, the consumption of accelerator can be 0.2-2 mass parts, such as 0.5 mass parts, 0.6 mass parts, 0.8 mass parts, 1 mass parts, 1.5 mass parts. In some preferred embodiments, accelerator is accelerator NS (N- tert-butyl -2- benzothiazole sulfenamide).

[0069] In addition, when necessary, the rubber composition may further include plasticizers such as DMP (dimethyl phthalate), DEP (diethyl phthalate), DBP (dibutyl phthalate), DHP (diheptyl phthalate), DOP (dioctyl phthalate), DINP (diisononyl phthalate), DIDP (diisodecyl phthalate), BBP (butyl benzyl phthalate), DWP (dilauryl phthalate), and DCHP (dicyclohexyl phthalate). The amount of the plasticizer used may be a conventional amount in the art.

[0070] In some preferred embodiments, the raw materials of the rubber composition of the present invention include: 100 parts by mass of a diene elastomer, 0.5-3 parts by mass of sulfur, 1-5 parts by mass of the antioxidant composition of the present invention, 30-70 parts by mass of carbon black, 1-10 parts by mass of ZnO, 1-5 parts by mass of stearic acid, 1-10 parts by mass of aromatic oil and 0.2-2 parts by mass of an accelerator, or are composed of the above components; wherein the diene elastomer preferably includes natural rubber and butadiene rubber in a mass ratio of 1:2-2:1, and the accelerator is preferably accelerator NS.

[0071] The unvulcanized rubber of the present invention can be prepared by conventional rubber mixing methods, for example, by a two-stage mixing method: a first stage of thermomechanical mixing (e.g., internal mixer) to mix the rubber composition raw materials except the crosslinking agent and the accelerator, and knead the entire mixture until it reaches a maximum temperature between 110°C and 190°C to obtain a first stage of rubber; a second stage of thermomechanical mixing (e.g., open mixer) to cool the first stage of rubber to below 100°C, then mix the first stage of rubber with the crosslinking agent and the accelerator until the maximum temperature is below 110°C to obtain a second stage of rubber, i.e., the unvulcanized rubber.

[0072] Vulcanized rubber can be obtained by vulcanizing (curing) the unvulcanized rubber. The vulcanization temperature is typically 130°C-200°C, e.g., 140-160°C, 145±5°C. The vulcanization time depends on the vulcanization temperature, the vulcanization system, and the vulcanization kinetics, and is typically 15-60 minutes, e.g., 20-40 minutes, 30±5 minutes. Before vulcanization, the unvulcanized rubber can be rolled to a certain thickness, e.g., approximately 2 mm.

[0073] The rubber composition of the present invention is used for rubber products, especially tires. Compared with using antioxidant 6PPD or a formula A compound alone, the use of the antioxidant composition of the present invention, particularly the combination of formula I compound and formula II compound, the combination of formula IV compound and formula V compound, and the combination of formula VII compound and formula VIII compound can significantly improve the ozone aging resistance of the rubber product. Therefore, the present invention also provides a rubber product, the rubber product contains rubber composition as described herein. The rubber product can be a tire, rubber shoes, sealing strips, sound insulation boards, anti-vibration pads, etc. The rubber product is preferably a tire, such as sidewall rubber, tread rubber, etc.

[0074] The present invention also provides the use of the antioxidant composition of the present invention, such as a combination of a compound of formula I and a compound of formula II, a combination of a compound of formula IV and a compound of formula V, and a combination of a compound of formula VII and a compound of formula VIII in improving the ozone aging resistance of a rubber composition or a rubber product, and a method for improving the ozone aging resistance of a rubber composition or a rubber product. Preferably, the use or method of the present invention comprises: adding 1 to 5 parts by mass of the antioxidant composition of the present invention to the raw materials of the rubber composition based on 100 parts by mass of the diene elastomer contained in the rubber composition. In the use or method of the present invention, the raw material composition of the rubber composition is preferably as described in any embodiment herein.

[0075] The present invention will be described below by way of specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the present invention. The methods, reagents, and materials used in the examples are, unless otherwise stated, conventional methods, reagents, and materials in the art. The starting compounds in the examples can all be purchased from commercial sources.

[0076] The raw materials used in the examples are: natural rubber (SCR5), Xishuangbanna Sinochem Rubber Co., Ltd.; butadiene rubber (BR9000), Shandong Yuhuang Chemical Co., Ltd.; antioxidant 6PPD, Shengao Chemical Technology Co., Ltd.; carbon black N550, zinc oxide, stearic acid (SA), aromatic oil, sulfur (S) and accelerator NS are all common raw materials in the rubber industry.

[0077] Preparation Example 1: Synthesis of Compounds of Formula I

[0078] (1) Synthesis of compound of formula III

[0079] In a 1000 mL four-necked flask, 400.2 g (3.25 mol) of o-methyl ether aniline and 200.2 g (0.55 mol) of a 25% aqueous solution of tetramethylammonium hydroxide (TMAOH) were added. The mixture was stirred and heated to 40-50° C., and dehydrated by vacuum distillation to form a salt between TMAOH and o-methyl ether aniline. During this process, the reaction solution gradually changed from yellow to reddish brown. The temperature was gradually raised to 75° C. When the fraction was approximately 100 g, 61.55 g (0.50 mol) of nitrobenzene was added dropwise at 75° C. under reduced pressure (−0.097 MPa) for approximately 3 h. After the addition was complete, the mixture was kept warm for 1 h. LC monitoring was performed to obtain a condensation solution.

[0080] The condensation solution was transferred to a 1000 mL stainless steel reactor, and 100 g of deionized water and 60 g of skeletal nickel catalyst were added. The atmosphere was replaced with hydrogen three times, and the temperature was raised to 65°C and the pressure was increased to 1.5 MPa. LC monitoring was performed until the nitro and nitroso compounds were completely reduced. The reaction solution was filtered, washed with water, and phase separated. The aqueous phase was concentrated and reused, and the organic phase was distilled under reduced pressure to yield 84.6 g of compound III (yield approximately 79.5%), with a GC assay of >99.2%.

[0081] Molecular formula: C 13 H 14 N2O

[0082] LC-MS (m / z): 214.26 (MH + ).

[0083] (2) Synthesis of compound of formula I

[0084] 50 g (0.23 mol) of the compound of formula III, 100 g (1.0 mol) of 4-methyl-2-pentanone, and 1.0 g of Pt / C were placed in a 500 mL autoclave and heated to 90°C for reaction. After hydrogen substitution, the pressure was raised to 1.2 MPa for reaction. GC analysis showed that the content of the compound of formula III was <0.1%. The temperature was then lowered and the reaction was stopped. Filtering and vacuum distillation were performed to remove light components such as water and 4-methyl-2-pentanone to obtain 65.1 g of the compound of formula I (yield approximately 95%). The content was >98.2% as determined by GC. Properties: Purple-brown liquid.

[0085] Molecular formula: C 19 H 26 N2O

[0086] LC-MS (m / z): 298.42 (MH + ).

[0087] Preparation Example 2: Synthesis of Formula II

[0088] (1) Synthesis of compound of formula III

[0089] The synthesis of the compound of formula III is the same as step (1) of Preparation Example 1.

[0090] (2) Synthesis of compound of formula II

[0091] 81.5 g (0.38 mol) of the compound of formula III, 117 g (1.62 mol) of 2-butanone, and 1.0 g of Pt / C were placed in a 500 mL autoclave, heated to 70°C for reaction, and then hydrogen-purged and pressurized to 1.2 MPa for reaction. GC analysis revealed a content of the compound of formula III of <0.1%. The reaction was then cooled and stopped. Filtering and vacuum distillation were performed to remove light components such as water and 2-butanone, yielding 99.5 g of the compound of formula II (yield approximately 97%). GC analysis revealed a content of >97.2%. Properties: Purple liquid.

[0092] Molecular formula: C 17 H 22 N2O

[0093] LC-MS (m / z): 270.37 (MH + ).

[0094] Preparation Example 3: Synthesis of Formula IV

[0095] (1) Synthesis of compound of formula III

[0096] The synthesis of the compound of formula III is the same as step (1) of Preparation Example 1.

[0097] (2) Synthesis of compound of formula IV

[0098] 92 g (0.43 mol) of the compound of formula III, 106 g (1.83 mol) of acetone, and 1.0 g of Pt / C were placed in a 500 mL autoclave. The reaction was heated to 75°C. After hydrogen substitution, the pressure was raised to 1.2 MPa. GC analysis showed that the content of the compound of formula III was <0.1%. The temperature was then lowered and the reaction was stopped. Filtering and vacuum distillation were performed to remove light components such as water and acetone to obtain 106.1 g of the compound of formula IV (yield approximately 96%). The content was >97.6% as determined by GC. Properties: Purple liquid.

[0099] Molecular formula: C 16 H 20 N2O

[0100] LC-MS (m / z): 256.35 (MH + ).

[0101] Preparation Example 4: Synthesis of Compound V

[0102] (1) Synthesis of compound of formula III

[0103] The synthesis of the compound of formula III is the same as step (1) of Preparation Example 1.

[0104] (2) Synthesis of compound of formula V

[0105] 62 g (0.29 mol) of the compound of formula III, 107 g (1.24 mol) of 2-pentanone, and 1.0 g of Pt / C were placed in a 500 mL autoclave and heated to 80°C for reaction. After hydrogen substitution, the pressure was raised to 1.2 MPa for reaction. GC analysis revealed a content of the compound of formula III of <0.1%. The reaction was then cooled and stopped. Filtering and vacuum distillation were performed to remove light components such as water and 2-pentanone, yielding 79.2 g of the compound of formula V (yield approximately 96%), with a GC content of >98.2%. Properties: Purple liquid.

[0106] Molecular formula: C 18 H 24 N2O

[0107] LC-MS (m / z): 284.40 (MH + ).

[0108] Preparation Example 5: Synthesis of Compound VII

[0109] (1) Synthesis of compound of formula VI

[0110] In a 500 mL four-necked flask, 220 g (1.6 mol) of o-ethyl ether aniline and 80 g (0.22 mol) of a 25% aqueous solution of tetramethylammonium hydroxide (TMAOH) were added. The mixture was stirred and heated to 50° C., and dehydrated by vacuum distillation to form a salt between TMAOH and o-ethyl ether aniline. During this process, the reaction solution gradually changed from yellow to reddish brown. The temperature was gradually raised to 75° C. When the fraction was approximately 100 g, 24.6 g (0.2 mol) of nitrobenzene was added dropwise at 78° C. under reduced pressure (−0.097 MPa) for approximately 3 h. After the addition was complete, the mixture was kept warm for 1 h. LC monitoring was performed to obtain a condensation solution.

[0111] The condensation solution was transferred to a 500 mL stainless steel reactor, and 30 g of deionized water and 20 g of skeletal nickel catalyst were added. The atmosphere was replaced with hydrogen three times, and the temperature was raised to 69°C and the pressure was increased to 1.6 MPa. LC monitoring was performed until the nitro and nitroso compounds were completely reduced. The reaction solution was filtered, washed with water, and phase separated. The aqueous phase was concentrated and reused, and the organic phase was distilled under reduced pressure to yield 34.1 g of the intermediate compound of formula VI (yield approximately 75%). The GC assay showed a content of >98.5%.

[0112] Molecular formula: C 14 H 16 N2O

[0113] LC-MS (m / z): 228.26 (M-H+).

[0114] (2) Synthesis of compound of formula VII

[0115] 30 g (0.13 mol) of the compound of formula VI, 43.2 g (0.6 mol) of 2-butanone, and 0.6 g of Pt / C were placed in a 500 mL autoclave. The reaction was heated to 70°C. After hydrogen substitution, the pressure was raised to 1.2 MPa. GC analysis revealed a content of the compound of formula VI of <0.1%. The reaction was then cooled and stopped. Filtering and vacuum distillation were performed to remove light components such as water and 2-butanone, yielding 35.4 g of the compound of formula VII (yield: approximately 96%). The content of the compound was >97.5% as determined by GC. Properties: Reddish-brown liquid.

[0116] Molecular formula: C 18 H 24 N2O

[0117] LC-MS (m / z): 284.40 (M-H+).

[0118] Preparation Example 6: Synthesis of Compound VIII

[0119] (1) Synthesis of compound of formula VI

[0120] The synthesis of the compound of formula VI is the same as step (1) of Preparation Example 5.

[0121] (2) Synthesis of compound of formula VIII

[0122] 30 g (0.13 mol) of the compound of formula VI, 78 g (0.8 mol) of 4-methyl-2-pentanone, and 0.8 g of Pt / C were placed in a 500 mL autoclave and heated to 90°C for reaction. After hydrogen substitution, the pressure was raised to 1.8 MPa for reaction. GC analysis revealed a content of the compound of formula VI of <0.1%. The reaction was then cooled and stopped. Filtering and vacuum distillation were performed to remove light components such as water and 4-methyl-2-pentanone to obtain 39.8 g of the compound of formula VIII (yield approximately 98%), with a GC content of >98.0%. Properties: Reddish-brown liquid.

[0123] Molecular formula: C 20 H 28 N2O

[0124] LC-MS (m / z): 312.46 (MH + ).

[0125] Example 1

[0126] According to the formulation shown in Table 1-2, rubber composition 1-14 was prepared using the following process:

[0127] (1) adding natural rubber and butadiene rubber into an internal mixer, and then adding carbon black, zinc oxide, stearic acid, aromatic oil and antioxidant (antioxidant 6PPD, compound of formula II, compound of formula I, compound of formula IV, compound of formula V, compound of formula VII and / or compound of formula VIII), and kneading until the temperature of the rubber material rises to 130° C. and the rubber is discharged to obtain a rubber stage;

[0128] (2) After the first stage rubber is cooled to 50°C, the first stage rubber is mixed on an open mill, accelerator NS and sulfur are added, and the mixture is kneaded until the temperature of the rubber reaches 70°C and a sheet is produced to obtain the second stage rubber;

[0129] (3) The second-stage rubber was rolled into a sheet with a thickness of 2 mm, and the second-stage rubber was vulcanized (145°C × 30 min) to obtain a vulcanized rubber.

[0130] Table 1: Rubber composition formula (unit: mass parts)

[0131] Table 2: Rubber composition formula (unit: mass parts)

[0132] Test Example 1: Vulcanization Characteristics Test and Thermal Oxidative Aging Test

[0133] Vulcanization properties t10 and t90 were measured according to GB / T 16584-1996, "Rotorless Rheometer for Rubber." Thermal oxidative aging tests were conducted at 100°C for 48 hours in accordance with GB / T 3512-2014, "Rubber, Vulcanized or Thermoplastic Rubber — Hot Air Accelerated Aging and Heat Resistance Tests." Elongation at break and tensile strength before and after aging were measured in accordance with GB / T 528-2009, "Rubber, Vulcanized or Thermoplastic Rubber — Determination of Tensile Stress-Strain Properties." The results are shown in Tables 3-4.

[0134] Table 3: Curing characteristics and physical properties before and after thermal oxidative aging

[0135] Table 4: Curing characteristics and physical properties before and after thermal oxidative aging

[0136] Test Example 2: Ozone Aging Test

[0137] The ozone resistance of rubber was tested in an ozone aging test chamber using ISO 1431-1:2004 “Ozone cracking resistance of vulcanized or thermoplastic rubber”. The test conditions were: ozone volume concentration 50×10 -8 The test conditions were (40±2°C, 50±5%). For static testing, the sample was pre-stretched to 20%, tested at fixed intervals, and observed for cracking. For dynamic testing, the sample was pre-stretched to 10%, dynamically stretched to 10%, and tested at a frequency of 0.5 Hz. The test was run at fixed intervals, and observed for cracking. The results of the static ozone aging test are shown in Tables 5-6. The results of the dynamic ozone aging test are shown in Tables 7-8. The ozone cracking levels in Tables 5-8 are described in Table 9.

[0138] Table 5: Static ozone aging test results of rubber crack grade

[0139] Table 6: Static ozone aging test results of rubber crack grade

[0140] Table 7: Dynamic ozone aging test results of rubber crack grade

[0141] Table 8: Dynamic ozone aging test results of rubber crack grade

[0142] Table 9: Ozone aging test crack level description

[0143] As can be seen from Tables 3-8, compared to rubber compositions 1-3 containing only 6PPD, a compound of Formula I, or a compound of Formula II, rubber compositions 4-8 containing a compound of Formula I and a compound of Formula II exhibited comparable basic physical properties and significantly improved static and dynamic ozone aging resistance. Compared to rubber compositions 11-12 containing only a compound of Formula IV or a compound of Formula V, rubber composition 9 containing a compound of Formula IV and a compound of Formula V exhibited comparable basic physical properties and significantly improved static and dynamic ozone aging resistance. Compared to rubber compositions 13-14 containing only a compound of Formula VII or a compound of Formula VIII, rubber composition 10 containing a compound of Formula VII and a compound of Formula VIII exhibited comparable basic physical properties and improved static and dynamic ozone aging resistance. This demonstrates that the combination of a compound of Formula I and a compound of Formula II, a compound of Formula IV and a compound of Formula V, and a compound of Formula VII and a compound of Formula VIII achieve an unexpected synergistic effect in improving the static and dynamic ozone aging resistance of rubber compositions.

Claims

1. An antioxidant composition, characterized in that The antioxidant composition comprises two or more compounds of formula A: In formula A, R1 and R2 are each independently selected from a C1-C8 alkyl group.

2. The antioxidant composition according to claim 1, characterized in that In formula A, R1 is selected from C1-C2 alkyl, and R2 is selected from C3-C6 alkyl.

3. The antioxidant composition according to claim 1, characterized in that The antioxidant composition comprises two or more compounds selected from the group consisting of a compound of formula I, a compound of formula II, a compound of formula IV, a compound of formula V, a compound of formula VII and a compound of formula VIII:

4. The antioxidant composition according to claim 3, characterized in that The antioxidant composition comprises a compound of formula I and a compound of formula II, or comprises a compound of formula IV and a compound of formula V, or comprises a compound of formula VII and a compound of formula VIII; Preferably, in the antioxidant composition, the mass ratio of the compound of formula I to the compound of formula II, the mass ratio of the compound of formula IV to the compound of formula V, or the mass ratio of the compound of formula VII to the compound of formula VIII is 1:4 to 4:

1.

5. A rubber composition, characterized in that: The raw materials of the rubber composition include 100 parts by mass of a diene elastomer and 1 to 5 parts by mass of the antioxidant composition according to any one of claims 1 to 4.

6. The rubber composition according to claim 5, characterized in that The raw materials of the rubber composition include 2-3 parts by mass of the antioxidant composition.

7. The rubber composition according to claim 5, characterized in that The diene elastomer comprises natural rubber and butadiene rubber; preferably, the mass ratio of the natural rubber to the butadiene rubber is 1:2 to 2:

1.

8. The rubber composition according to claim 5, characterized in that The rubber composition has one or more of the following characteristics: The raw materials of the rubber composition further include 30-70 parts by mass of a reinforcing filler; preferably, the reinforcing filler is carbon black; The raw materials of the rubber composition further include 1-10 parts by mass of an active agent; preferably, the active agent is zinc oxide; The raw materials of the rubber composition further include 2-15 parts by mass of a softener; preferably, the softener includes aromatic oil and stearic acid in a mass ratio of 1:1 to 5:1; The raw materials of the rubber composition also include 0.5-3 parts by mass of sulfur; The raw materials of the rubber composition further include 0.2-2 parts by mass of an accelerator, and the accelerator is preferably N-tert-butyl-2-benzothiazole sulfenamide.

9. A rubber product, characterized in that: The rubber product comprises the rubber composition according to any one of claims 5 to 8; preferably, the rubber product is a tire.

10. Use of the antioxidant composition according to any one of claims 1 to 4 in improving the ozone aging resistance of a rubber composition or a rubber product.

Images