Antioxidant resistant to damp-heat aging and ozone aging, and rubber composition and use thereof

Abstract

Provided in the present invention are a compound of formula A, which can be used as an antioxidant, an antioxidant composition comprising the compound of formula A and an antioxidant STMQ, a rubber composition comprising the antioxidant composition or the compound of formula A, and the use of the rubber composition. The compound of formula A is as described in the specification. The antioxidant and the antioxidant composition of the present invention can significantly improve the damp-heat aging resistance of a tire rubber material, and also have good ozone aging resistance, thereby prolonging the service life of a tire in special and harsh environments.

Description

Anti-aging agent resistant to moist heat and ozone aging, rubber composition and use thereof Technical Field

[0001] The invention belongs to the field of rubber materials and relates to an antioxidant resistant to moist heat aging and ozone aging, a rubber composition and applications thereof. Background Art

[0002] During storage, processing, and use, rubber products can experience degradation or loss of performance due to both their own factors and environmental factors (heat, oxygen, ozone, ultraviolet light, chemicals, etc.). Oxygen is a significant factor in rubber aging, while thermal absorption is the primary factor in the pyrolysis of polymer materials in a vacuum or inert environment. Thermal energy also accelerates the oxidation of rubber products. Ozone is more reactive than oxygen, making it more aggressive than oxygen to rubber, especially unsaturated rubber. The reaction between ozone and rubber double bonds accelerates the initiation and growth of cracks. Furthermore, increasing ozone concentration shortens the time it takes for cracks to appear, while increasing the rate of crack growth.

[0003] Currently, tire formulations commonly incorporate both physical and chemical antioxidants to improve the tire's resistance to ozone aging, including both static and dynamic performance. Chemical antioxidants, particularly p-phenylenediamine antioxidants such as 6PPD (N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine) and IPPD (N-isopropyl-N'-phenyl-p-phenylenediamine), are widely used in the tire industry due to their excellent comprehensive protection against ozone, thermal oxygen, and dynamic fatigue.

[0004] Water (precipitation, humidity, condensation, etc.) also plays an important role in accelerating the aging of rubber products. The extraction effect of water often accelerates the loss of antioxidants on the surface of rubber products, thereby accelerating aging and causing a decline in physical and mechanical properties.

[0005] When rubber products are used and stored in harsher environments, such as high temperature and high humidity, the water solubility (water extraction resistance) of different antioxidants varies significantly, causing the concentration / ratio of antioxidants in the rubber compound to drop significantly, ultimately leading to a significant decrease in the protective effect of rubber products. Related literature reveals that the antioxidants IPPD and 6PPD both have poor resistance to hot water extraction.

[0006] Summary of the Invention

[0007] In response to the problems existing in the prior art, the present invention provides an antioxidant having resistance to moist heat aging and ozone aging, an antioxidant composition containing the antioxidant, a rubber composition containing the antioxidant or the antioxidant composition, and uses thereof. The antioxidant and antioxidant composition of the present invention can significantly improve the moist heat aging resistance of the rubber composition, such as tire rubber, while maintaining the original physical properties and heat and oxygen aging resistance of the rubber composition, while also having good ozone aging resistance, thereby extending the service life of rubber products, such as tires, in special and harsh environments.

[0008] Specifically, one aspect of the present invention provides a compound of formula A which can be used as an antioxidant:

[0009] In formula A, R1, R2 and R3 are each independently selected from a C1-C8 alkyl group.

[0010] In one or more embodiments, in formula A, R1 and R2 are each independently selected from C1-C2 alkyl, and R3 is selected from C3-C6 alkyl, preferably C4-C6 alkyl.

[0011] In one or more embodiments, the compound of formula A is a compound of formula I, a compound of formula II, a compound of formula IV, or a compound of formula VI:

[0012] In one or more embodiments, the compound of formula A does not include a compound wherein R1 and R2 are methyl and R3 is isopropyl.

[0013] Another aspect of the present invention provides an antioxidant composition, which comprises an antioxidant STMQ and a compound of formula A described in any embodiment of the present invention, wherein the antioxidant STMQ is a 2,2,4-trimethyl-1,2-dihydroquinoline polymer having a total mass fraction of dimers, trimers, and tetramers of 2,2,4-trimethyl-1,2-dihydroquinoline of ≥80%.

[0014] In one or more embodiments, in the antioxidant composition, the mass ratio of the compound of formula A to the antioxidant STMQ is 1:1 to 3:1, preferably 1.5:1 to 2.5:1.

[0015] Another aspect of the present invention provides a rubber composition, the raw materials of which include 100 parts by mass of a diene elastomer and 1-5 parts by mass of the compound of formula A described in any embodiment herein, or 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 described in any embodiment herein.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] In one or more embodiments, the raw materials of the rubber composition further include 0.5-3 parts by mass of sulfur.

[0021] 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.

[0022] 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.

[0023] The present invention also provides use of the compound of formula A described in any embodiment herein or the antioxidant composition described in any embodiment herein in improving the wet heat aging resistance and / or ozone aging resistance of a rubber composition or rubber product. DETAILED DESCRIPTION

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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).

[0028] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0029] 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.

[0030] 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.

[0031] In the present invention, the compound of formula A has the following structure:

[0032] In formula A, R1, R2 and R3 are each independently selected from a C1-C8 alkyl group.

[0033] In the present invention, an alkyl group refers to a linear or branched monovalent saturated hydrocarbon group. An alkyl group may contain 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.

[0034] In Formula A, R1 can be located in the ortho, meta, or para position relative to the -NH- group on the benzene ring, and R2 can be located in the ortho, meta, or para position relative to R1. In some embodiments, R1 is located in the ortho position relative to the -NH- group on the benzene ring, and R2 is located in the ortho position relative to R1. In some embodiments, R1 is located in the meta position relative to the -NH- group on the benzene ring, and R2 is located in the para position relative to the -NH- group on the benzene ring.

[0035] Preferably, in formula A, R1 and R2 are each independently selected from C1-C4 alkyl, more preferably from C1-C3 alkyl, for example, from methyl and ethyl.

[0036] Preferably, in formula A, R3 is selected from C3-C8 alkyl, more preferably from C3-C6 alkyl or C4-C6 alkyl, for example, selected from isopropyl, 1-methylpropyl, 1-methylbutyl and 1,3-dimethylbutyl.

[0037] In some preferred embodiments, in formula A, R1 and R2 are each independently selected from C1-C2 alkyl, and R3 is selected from C3-C6 alkyl, preferably C4-C6 alkyl.

[0038] In some embodiments, the compound of formula A is a compound of formula I, a compound of formula II, a compound of formula IV, or a compound of formula VI:

[0039] The present invention has discovered that the use of a compound of formula A in a rubber composition, particularly a tire rubber composition, can significantly improve the wet-heat aging resistance and ozone aging resistance of the rubber composition, with the improvement effect being significantly superior to that of a conventional p-phenylenediamine antioxidant (e.g., IPPD), while maintaining good original physical properties and resistance to heat and oxygen aging. The present invention has also discovered that the combination of a compound of formula A and the antioxidant STMQ in a rubber composition, particularly a tire rubber composition, can significantly improve the wet-heat aging resistance and ozone aging resistance of the rubber composition, with the improvement effect being significantly superior to that of a conventional p-phenylenediamine antioxidant (e.g., IPPD) and the antioxidant STMQ, while maintaining good original physical properties and resistance to heat and oxygen aging.

[0040] In the present invention, the antioxidant STMQ refers to a 2,2,4-trimethyl-1,2-dihydroquinoline polymer having a total mass fraction of 2,2,4-trimethyl-1,2-dihydroquinoline dimers, trimers, and tetramers of 2,2,4-trimethyl-1,2-dihydroquinoline of ≥80%. The 2,2,4-trimethyl-1,2-dihydroquinoline polymer (also known as antioxidant TMQ) has the structure shown in Formula B:

[0041] In formula B, n represents the degree of polymerization.

[0042] In the present invention, the compound of formula A can be prepared by a method comprising the following steps:

[0043] (1) subjecting a compound of formula C to a condensation reaction with nitrobenzene in the presence of a first catalyst to obtain a condensate comprising a compound of formula D and / or a compound of formula D′, and then subjecting the condensate to a reduction reaction in the presence of H2 and a second catalyst to obtain a compound of formula E;

[0044] (2) subjecting the compound of formula E to a reductive alkylation reaction with the compound of formula F in the presence of H2 and a third catalyst to obtain a compound of formula A;

[0045] R1, R2, and R3 in Formula A, Formula C, Formula D, and Formula E are as described in any embodiment herein, and R4 and R5 in Formula F are each independently selected from H and C1-C7 alkyl. Those skilled in the art can determine suitable R4 and R5 in Formula F based on R3 contained in the compound of Formula A.

[0046] 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.

[0047] The molar ratio of the first catalyst to the compound of formula C 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 C and the first catalyst are first salted, and then nitrobenzene is added dropwise to carry out a condensation reaction.

[0048] In step (1), the condensation product obtained by the condensation reaction of the compound of formula C with nitrobenzene in the presence of a first catalyst may be one or both of the nitro compound represented by formula D and the nitroso compound represented by formula D′, and may also include an azobenzene compound.

[0049] In step (1), the molar ratio of the compound of formula C 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.

[0050] 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.

[0051] 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.

[0052] 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 E. 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.

[0053] In step (1), 2,3-dimethylaniline 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. The organic phase is then distilled under reduced pressure to remove light components to obtain the compound of formula E.

[0054] 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 E can be 0.0001:1 to 0.2:1.

[0055] In step (2), after the reaction, the carbonyl carbon atom in the compound of formula F is connected to the amino nitrogen atom in the compound of formula E. Therefore, a suitable compound of formula F 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 F to the compound of formula E 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.

[0056] In step (2), the compound of formula F, 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.

[0057] 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.

[0058] The antioxidant composition of the present invention comprises (1) one or more compounds of formula A, and (2) an antioxidant STMQ. In some embodiments, the antioxidant composition of the present invention consists of the compounds of formula A and the antioxidant STMQ. In the antioxidant composition of the present invention, the mass ratio of the compounds of formula A to the antioxidant STMQ can be 1:1 to 3:1, for example, 1.5:1, 2:1, or 2.5:1.

[0059] 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.

[0060] The raw materials of the rubber composition of the present invention include a diene elastomer and one or more compounds of formula A. The amount of the compound of formula A can be 1-5 parts by mass, preferably 1-3 parts by mass, such as 1.5 parts by mass, 2 parts by mass, or 2.5 parts by mass, based on 100 parts by mass of the diene elastomer. Unless otherwise specified herein, the mass of other components in the rubber composition raw materials is calculated based on 100 parts by mass of the diene elastomer.

[0061] In some embodiments, the raw materials of the rubber composition of the present invention include a diene elastomer and the antioxidant composition of the present invention, wherein the amount of the antioxidant composition of the present invention can be 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, 3.5 parts by mass, and 4 parts by mass.

[0062] 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.

[0063] The antioxidant contained in the rubber composition of the present invention includes a compound of formula A. In the raw materials of the rubber composition of the present invention, the amount of the compound of formula A can be 1-5 parts by mass, preferably 1-3 parts by mass, for example 1.5 parts by mass, 2 parts by mass, or 2.5 parts by mass. Controlling the amount of the compound of formula A within the aforementioned range is conducive to ensuring the effect of improving the wet heat aging resistance and the ozone aging resistance at a lower dosage.

[0064] In some embodiments, the raw material of rubber combination of the present invention comprises formula A compound and antioxidant STMQ, i.e. comprises antioxidant composition of the present invention.In the raw material of rubber combination of the present invention, the consumption of antioxidant composition of the present invention can be 1-5 mass parts, such as 1.5 mass parts, 2 mass parts, 2.5 mass parts, 3 mass parts, 3.5 mass parts, 4 mass parts, wherein the consumption of antioxidant STMQ is preferably 0.5-2 mass parts, such as 0.8 mass parts, 1 mass parts, 1.2 mass parts, 1.5 mass parts, the consumption of formula A compound is preferably 1-3 mass parts, such as 1.5 mass parts, 2 mass parts, 2.5 mass parts.The consumption control of antioxidant composition of the present invention in aforementioned range is conducive to ensuring improvement of wet heat aging resistance and the effect of ozone aging resistance under lower consumption.

[0065] In some embodiments, the antioxidant contained in the raw materials of the rubber composition of the present invention includes only the compound of formula A, or only the compound of formula A and the antioxidant STMQ.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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 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, 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 used is 1-10 parts by mass, for example, 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 used is 1-5 parts by mass, for example, 1.5 parts by mass, 2 parts by mass, and 3 parts by mass.

[0070] 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.

[0071] Activating agent can play the effect 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 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, activating agent includes ZnO, or 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.

[0072] 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).

[0073] 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.

[0074] 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 a compound of formula A or an 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.

[0075] 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., an 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., an open mixer) to cool the first stage of rubber, 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., an unvulcanized rubber.

[0076] Vulcanized rubber can be obtained by vulcanizing (curing) the unvulcanized rubber. The vulcanization temperature is generally 130°C-200°C, for example, 140-160°C, 145±5°C. The vulcanization time depends on the vulcanization temperature, the vulcanization system, and the vulcanization kinetics, and is generally 15-60 minutes, for example, 20-40 minutes, 30±5 minutes.

[0077] The rubber composition of the present invention is used in rubber products, especially tires, and compared with using traditional p-phenylenediamine antioxidants such as IPPD, using formula A compound or antioxidant composition of the present invention can significantly improve the resistance to wet heat aging and ozone aging of rubber products. Therefore, the present invention also provides a kind of rubber product, and the rubber product contains rubber composition as herein described. The rubber product can be 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.

[0078] The present invention also provides the use of the compound of formula A or the antioxidant composition of the present invention in improving the resistance to moist heat aging and / or ozone aging of a rubber composition, and a method for improving the resistance to moist heat aging and / or ozone aging of a rubber composition. Preferably, the use or method of the present invention comprises: adding 1 to 5 parts by mass of the compound of formula A or 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.

[0079] 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.

[0080] The raw materials used in the examples are as follows: natural rubber (SCR5), Xishuangbanna Sinochem Rubber Co., Ltd.; butadiene rubber (BR9000), Shandong Yuhuang Chemical Co., Ltd.; antioxidant 6PPD, Shengao Chemical Technology Co., Ltd.; antioxidant STMQ, Kemai Chemical Co., Ltd.; carbon black N550, zinc oxide, stearic acid, aromatic oil, sublimed sulfur and accelerator NS are all common raw materials in the rubber industry.

[0081] Preparation Example 1: Synthesis of Compounds of Formula I

[0082] (1) Synthesis of compound of formula III

[0083] In a 500 mL four-necked flask, 181.5 g (1.5 mol) of 2,3-dimethylaniline and 100.1 g (0.275 mol) of a 25% aqueous solution of tetramethylammonium hydroxide (TMAOH) were added, stirred, heated to 40-50° C., and dehydrated by vacuum distillation to form a salt between TMAOH and 2,3-dimethylaniline. During this process, the reaction solution gradually changed from yellow to deep red. The temperature was gradually raised to 72° C. When the fraction was approximately 50% of the amount of 25% tetramethylammonium hydroxide charged as the catalyst, 31 g (0.25 mol) of nitrobenzene was added dropwise at 72° C. under reduced pressure (−0.098 MPa) for about 3 h. After the addition was complete, the mixture was kept warm for 1 h. LC monitoring was performed to obtain a condensation solution.

[0084] The condensation solution was transferred to a 500 mL stainless steel reactor, and 50 g of deionized water and 40 g of skeletal nickel catalyst were added. The atmosphere was replaced with hydrogen three times, and the temperature was raised to 75°C and the pressure was increased to 1.5 MPa. LC monitoring was performed until the nitro and nitroso groups were completely reduced. The reaction solution was filtered, washed with water, and phase separated. The organic phase was distilled under reduced pressure (-0.1 MPa, 180°C) to remove light components, yielding 45.7 g of compound III (yield approximately 85%). The GC assay showed a content of >96%.

[0085] LC-MS (m / z): 212.30 (MH + ).

[0086] (2) Synthesis of compound of formula I

[0087] 42.5 g (0.2 mol) of the compound of formula III, 60 g (0.6 mol) of 4-methyl-2-pentanone, and 0.5 g of Pt / C catalyst were placed in a reactor. The atmosphere was replaced with hydrogen three times, and the temperature was raised to 100°C and the pressure was increased to 1.5 MPa. The reaction was stopped when the content of the compound of formula III was <0.1%. The temperature was lowered, the catalyst was removed by filtration, and light components were removed by distillation at -0.1 MPa and 180°C to obtain 57.6 g of the compound of formula I (yield: approximately 97.2%). The content was >96.8% as determined by GC. Properties: Reddish-brown liquid.

[0088] LC-MS (m / z): 296.46 (MH + ).

[0089] Preparation Example 2: Synthesis of Compound of Formula II

[0090] (1) Synthesis of compound of formula III

[0091] The synthesis of the compound of formula III is the same as that in Preparation Example 1.

[0092] (2) Synthesis of compound of formula II

[0093] 42.5 g (0.2 mol) of the compound of formula III, 100 g (1.38 mol) of 2-butanone, and 0.6 g of Pt / C catalyst were placed in a reactor. The atmosphere was replaced with hydrogen three times, and the temperature was raised to 80°C and the pressure was increased to 1.5 MPa for reaction. GC analysis was performed. The reaction was stopped when the content of the compound of formula III was less than 0.1%. The temperature was lowered, the catalyst was removed by filtration, and light components were removed by distillation at -0.1 MPa and 150°C to obtain 52.2 g of the compound of formula II (yield: approximately 97.4%). The content of the compound was greater than 95.8% as determined by GC analysis. Properties: Reddish-brown solid.

[0094] LC-MS (m / z): 268.40 (MH + ).

[0095] Preparation Example 3: Synthesis of Compound IV

[0096] (1) Synthesis of compound of formula V

[0097] In a 500 mL four-necked flask, 181.5 g (1.5 mol) of 3,4-dimethylaniline and 100.1 g (0.275 mol) of a 25% aqueous solution of tetramethylammonium hydroxide (TMAOH) were added, stirred, heated to 40-50° C., and dehydrated by vacuum distillation to form a salt between TMAOH and 2,3-dimethylaniline. During this process, the reaction solution gradually changed from yellow to deep red. The temperature was gradually raised to 72° C. When the fraction was approximately 50% of the amount of 25% tetramethylammonium hydroxide charged as the catalyst, 31 g (0.25 mol) of nitrobenzene was added dropwise at 72° C. under reduced pressure (−0.098 MPa) for about 3 h. After the addition was complete, the mixture was kept warm for 1 h. LC monitoring was performed to obtain a condensation solution.

[0098] The condensation solution was transferred to a 500 mL stainless steel reactor, and 50 g of deionized water and 40 g of skeletal nickel catalyst were added. The atmosphere was replaced with hydrogen three times, and the temperature was raised to 75°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 organic phase was distilled under reduced pressure (-0.1 MPa, 180°C) to remove light components, yielding 43.5 g of compound V (yield approximately 82%). The GC assay showed a content of >95%.

[0099] LC-MS (m / z): 212.30 (MH + ).

[0100] (2) Synthesis of compound of formula IV

[0101] 42.5 g (0.2 mol) of the compound of formula V, 162.4 g (2.8 mol) of acetone, and 0.5 g of Pt / C catalyst were placed in a reactor. The atmosphere was replaced with hydrogen three times, and the temperature was raised to 70°C and the pressure was increased to 1.5 MPa. The reaction was stopped when the content of the compound of formula V was less than 0.1% by GC. The temperature was lowered, the catalyst was removed by filtration, and light components were removed by distillation at -0.1 MPa and 180°C to obtain 49 g of the compound of formula IV (yield: approximately 96.5%). The content was >96.0% by GC. Properties: Reddish-brown solid.

[0102] LC-MS (m / z): 254.38 (MH + ).

[0103] Preparation Example 4: Synthesis of Compound VI

[0104] (1) Synthesis of compound of formula VII

[0105] In a 500 mL four-necked flask, 223.8 g (1.5 mol) of 2,3-diethylaniline and 100.1 g (0.275 mol) of a 25% aqueous solution of tetramethylammonium hydroxide (TMAOH) were added, stirred, heated to 40-50° C., and dehydrated by vacuum distillation to form a salt between TMAOH and 2,3-dimethylaniline. During this process, the reaction solution gradually changed from yellow to deep red. The temperature was gradually raised to 72° C. When the fraction was approximately 50% of the 25% tetramethylammonium hydroxide charge of the catalyst, 31 g (0.25 mol) of nitrobenzene was added dropwise at 72° C. under reduced pressure (−0.098 MPa) for about 3 h. After the addition was complete, the mixture was kept warm for 1 h. LC monitoring was performed to obtain a condensation solution.

[0106] The condensation solution was transferred to a 500 mL stainless steel reactor, and 50 g of deionized water and 40 g of skeletal nickel catalyst were added. The atmosphere was replaced with hydrogen three times, and the temperature was raised to 75°C and the pressure was increased to 1.5 MPa. LC monitoring was performed until the nitro and nitroso groups were completely reduced. The reaction solution was filtered, washed with water, and phase separated. The organic phase was distilled under reduced pressure (-0.1 MPa, 180°C) to remove light components, yielding 45.6 g of compound of formula VII (yield approximately 75.9%). The GC assay showed a content of >94.5%.

[0107] LC-MS (m / z): 240.35 (MH + ).

[0108] (2) Synthesis of compound of formula VI

[0109] 43.2 g (0.18 mol) of the compound of formula VII, 155 g (1.8 mol) of 2-pentanone, and 0.5 g of Pt / C catalyst were placed in a reactor. The atmosphere was replaced with hydrogen three times, and the temperature was raised to 100°C and the pressure was increased to 1.5 MPa. The reaction was stopped when the content of the compound of formula VII was less than 0.1%. The temperature was lowered, the catalyst was removed by filtration, and light components were removed by distillation at -0.1 MPa and 180°C to obtain 53.2 g of the compound of formula VI (yield: approximately 95.3%). The content was >96.8% as determined by GC. Properties: Reddish-brown liquid.

[0110] LC-MS (m / z): 310.49 (MH + ).

[0111] Examples 1-6 and Comparative Examples 1-3

[0112] According to the formulation shown in Table 1, the rubber compositions of Examples 1-6 and Comparative Examples 1-3 were prepared using the following process:

[0113] (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 IPPD, compound of formula I, compound of formula II, compound of formula IV or compound of formula VI and / or antioxidant STMQ), kneading until the temperature of the rubber material rises to 130° C. and the rubber is discharged to obtain a rubber section;

[0114] (2) After the first stage rubber is cooled, it is milled 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;

[0115] (3) The second-stage rubber is vulcanized (145°C×30 min) to obtain a vulcanized rubber.

[0116] Table 1: Rubber composition formula (unit: mass parts)

[0117] Test Example 1: High Temperature Water Immersion Test

[0118] The vulcanized rubbers of Examples 1-6 and Comparative Examples 1-3 were soaked in deionized water at 90°C for 8 hours. The soaking liquid was then evaporated and dried. The precipitate was then dissolved in acetone and analyzed by liquid chromatography to determine the antioxidant content. The results are shown in Tables 2-4.

[0119] Table 2: Results of high temperature water immersion test on vulcanized rubber

[0120] Table 3: Results of high temperature water immersion test on vulcanized rubber

[0121] Table 4: Results of high temperature water immersion test on vulcanized rubber

[0122] Test Example 2: Humidity and heat aging test

[0123] The vulcanized rubbers of Examples 1-6 and Comparative Examples 1-3 were subjected to high-temperature, high-humidity aging tests according to GB / T 15905-1995, Test Method for Vulcanized Rubber. The test conditions were an aging chamber temperature of 70°C, a relative humidity of 90%, and an aging time of 14 days. The elongation at break and tensile strength were tested according to GB / T 528-2009, Test Method for Vulcanized Rubber — Determination of Tensile Stress-Strain Properties. The results are shown in Tables 5-7.

[0124] In this article, tensile product = tensile strength × elongation at break

[0125] In this article, physical property retention rate = tensile product after aging / tensile product before aging

[0126] Table 5: Physical properties of vulcanized rubber before and after high temperature and high humidity aging

[0127] Table 6: Physical properties of vulcanized rubber before and after high temperature and high humidity aging

[0128] Table 7: Physical properties of vulcanized rubber before and after high temperature and high humidity aging

[0129] Test Example 3: Thermal Oxidation Aging Test

[0130] The vulcanized rubbers of Examples 1-6 and Comparative Examples 1-3 were subjected to thermal oxidative aging tests according to GB / T 3512-2014, "Hot Air Accelerated Aging and Heat Resistance Tests for Vulcanized or Thermoplastic Rubber," at 100°C for 48 hours. Elongation at break and tensile strength were tested according to GB / T 528-2009, "Vulcanized or Thermoplastic Rubber — Determination of Tensile Stress-Strain Properties." The results are shown in Tables 8-10.

[0131] Table 8: Physical properties of vulcanized rubber before and after hot air aging

[0132] Table 9: Physical properties of vulcanized rubber before and after hot air aging

[0133] Table 10: Physical properties of vulcanized rubber before and after hot air aging

[0134] Test Example 4: Ozone Aging Test

[0135] The ozone aging test of the vulcanized rubbers of Examples 1-6 and Comparative Examples 1-3 was carried out in an ozone aging test chamber according to the following standards:

[0136] Dynamic ozone aging: GB / T 13642-2015 Dynamic tensile test for ozone cracking resistance of vulcanized rubber or thermoplastic rubber;

[0137] Static ozone aging: GB / T 7762-2014 Static tensile test for ozone cracking resistance of vulcanized rubber or thermoplastic rubber;

[0138] Crack grade evaluation: GB / T 11206-2009 Rubber aging test surface cracking method;

[0139] Specific test parameters are as follows: ozone volume concentration of 50 pphm, temperature (40±2)°C, humidity (50±5)%. Static testing was performed with a 20% pre-stretch and periodic observation for cracking. Dynamic testing was performed with a 10% pre-stretch, a 10% dynamic stretch, and a frequency of 0.5 Hz, with periodic observation for cracking. The results of dynamic and static ozone aging are shown in Tables 11 and 12, respectively. The meanings of 1c, 2c, 3c, and 4c in Tables 11 and 12 are as given in GB / T 11206-2019.

[0140] Table 11: Dynamic ozone aging cracking grade results

[0141] Table 12: Static ozone aging cracking grade results

[0142] The results in Table 2 show that after the rubber compounds of Examples 1-4 were soaked in water at 90°C for 8 hours, the antioxidant content in the precipitates was significantly lower than that in Comparative Example 1, and the antioxidant content in the precipitates was less than 20% of that in Comparative Example 1. The results in Table 3 show that the antioxidant content in the precipitates of the rubber compounds of Example 6 was significantly lower than that in Comparative Example 2. The results in Table 4 show that the antioxidant content in the precipitates of the rubber compounds of Example 5 was significantly lower than that in Comparative Example 3. The above results indicate that the antioxidants in Examples 1-6 are not easily migrated from the rubber composition under high temperature and high humidity conditions.

[0143] The results in Table 8 show that the performance retention rates of the rubber compounds of Examples 1-4 and the rubber compound of Comparative Example 1 after hot air aging at 100°C*48 hours are at the same level, indicating that the effect of the compound of Formula I, the compound of Formula II, the compound of Formula IV or the compound of Formula VI on improving the heat-oxidative aging resistance of the rubber compound is consistent with that of traditional paraphenylenediamine antioxidants.

[0144] However, as shown in Table 5, after aging for 14 days in a high-temperature, high-humidity environment at a temperature of 70°C and a relative humidity of 90%, the physical property retention rate of the rubber materials of Examples 1-4 remained at approximately 80%, while the physical property retention rate of the rubber material of Comparative Example 1 was only approximately 70%. As shown in Table 6, the physical property retention rate of the rubber material of Example 6 after high-temperature, high-humidity aging was significantly higher than that of Comparative Example 2. As shown in Table 7, the physical property retention rate of the rubber material of Example 5 after high-temperature, high-humidity aging was significantly higher than that of Comparative Example 3. The above results indicate that the antioxidants in the rubber materials of Examples 1-6 are not easily dissolved and extracted by water in a high-temperature, high-humidity environment, and can still maintain a relatively high concentration in the rubber material, thereby playing a good protective role and demonstrating excellent high-temperature, high-humidity aging resistance.

[0145] The results in Table 11 show that under dynamic ozone aging conditions, the initial crack density (Grade B) of the films of Examples 1-4 was significantly lower than that of the film of Comparative Example 1 (Grade C). In terms of crack width growth rate, the cracks of the films of Examples 1-4 grew significantly slower than those of Comparative Example 1. After 144 hours of ozone aging, the crack grade of the film of Comparative Example 1 was Grade 4, while the crack grades of the films of Examples 1-4 were all Grade 3, demonstrating a significant performance improvement. The crack grade of Examples 1-4 reached Grade 3 after aging for at least 120 hours, while that of Comparative Example 1 was only 96 hours, representing a performance improvement of over 25%.

[0146] The results in Table 12 show that after 120 hours of static ozone aging, the crack grade of the film of Comparative Example 1 is Level 4, while the crack grade of the films of Examples 1-4 is only Level 3, indicating a significant performance improvement. After the aging time is further extended to 144 hours, the crack grade of the films of Examples 1-4 is still maintained at Level 3, showing good durability.

[0147] Based on the above results, the compound of formula A and the antioxidant composition of the present invention can make the rubber composition have excellent high temperature and high humidity aging resistance and ozone aging resistance while maintaining the original physical properties and heat and oxygen aging resistance basically unchanged.

Claims

1. Compound of formula A: In formula A, R1, R2 and R3 are each independently selected from C1-C8 alkyl; The compound of formula A does not include the compound in which R1 and R2 are methyl and R3 is isopropyl.

2. The compound of formula A according to claim 1, characterized in that In formula A, R1 and R2 are each independently selected from C1-C2 alkyl groups, and R3 is selected from C3-C6 alkyl groups, preferably C4-C6 alkyl groups.

3. The compound of formula A according to claim 1, characterized in that The compound of formula A is a compound of formula I, a compound of formula II or a compound of formula VI:

4. An antioxidant composition, characterized in that The antioxidant composition comprises an antioxidant STMQ and a compound of formula A, wherein the antioxidant STMQ is a 2,2,4-trimethyl-1,2-dihydroquinoline polymer with a total mass fraction of dimers, trimers and tetramers of 2,2,4-trimethyl-1,2-dihydroquinoline of ≥80%, and the structural formula of the compound of formula A is: In formula A, R1, R2 and R3 are each independently selected from C1-C8 alkyl groups. Preferably, in formula A, R1 and R2 are each independently selected from C1-C2 alkyl, and R3 is selected from C3-C6 alkyl, preferably C4-C6 alkyl.

5. The antioxidant composition according to claim 4, characterized in that, The compound of formula A is selected from the group consisting of a compound of formula I, a compound of formula II, a compound of formula IV and a compound of formula VI:

6. The antioxidant composition according to claim 4, characterized in that, In the antioxidant composition, the mass ratio of the compound of formula A to the antioxidant STMQ is 1:1 to 3:1, preferably 1.5:1 to 2.5:

1.

7. A rubber composition, characterized in that: The raw materials of the rubber composition include 100 parts by mass of a diene elastomer and 1-5 parts by mass of a compound of formula A or an antioxidant composition as described in any one of claims 4-6, wherein the structural formula of the compound of formula A is: In formula A, R1, R2 and R3 are each independently selected from C1-C8 alkyl; Preferably, in formula A, R1 and R2 are each independently selected from C1-C2 alkyl, and R3 is selected from C3-C6 alkyl, preferably selected from C4-C6 alkyl; Preferably, the compound of formula A is selected from the group consisting of a compound of formula I, a compound of formula II, a compound of formula IV and a compound of formula VI:

8. The rubber composition according to claim 4, characterized in that The rubber composition has one or more of the following characteristics: 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; 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 claim 7 or 8; preferably, the rubber product is a tire.

10. Use of the compound of formula A or the antioxidant composition according to any one of claims 4 to 6 in improving the resistance to wet heat aging and / or ozone aging of a rubber composition or a rubber product, wherein the structural formula of the compound of formula A is: In formula A, R1, R2 and R3 are each independently selected from C1-C8 alkyl; Preferably, in formula A, R1 and R2 are each independently selected from C1-C2 alkyl, and R3 is selected from C3-C6 alkyl, preferably selected from C4-C6 alkyl; Preferably, the compound of formula A is selected from the group consisting of a compound of formula I, a compound of formula II, a compound of formula IV and a compound of formula VI:

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