Use of imidazolium compounds as anti-aging agents in rubber compositions

Abstract

The present application relates to the application of imidazolium compounds in rubber compositions as anti-aging agents. The present application uses imidazolium compounds with the structure shown in formula I as anti-aging agents of rubber compositions, which significantly improves the static and dynamic anti-ozone aging performance of the rubber compositions while maintaining good physical and mechanical properties of the rubber compositions. Compared with the traditional anti-aging agent 6PPD, the rubber composition can exhibit better crack resistance under the same ozone aging conditions, thereby effectively prolonging the service life of the rubber product.

Description

Technical Field

[0001] This invention relates to the field of rubber materials, and more specifically, to the application of imidazolium compounds as antioxidants in rubber compositions. Background Technology

[0002] Rubber products are inevitably subjected to various aging factors during processing, storage, and actual use, including heat, oxygen, ozone, ultraviolet radiation, and mechanical stress. Among these, ozone oxidative damage is particularly pronounced for diene rubbers containing unsaturated double bonds (such as natural rubber, styrene-butadiene rubber, cis-butadiene rubber, and nitrile rubber). Unlike the free radical chain-based autocatalytic oxidation mechanism of thermo-oxidative aging, ozone aging primarily occurs on the rubber surface: ozone attacks the unsaturated double bonds in the surface rubber molecular chains, causing cracks to form on the rubber surface, which continue to propagate under stress, significantly reducing the appearance quality and service life of rubber products. Because the aging mechanisms of different types of rubber vary, the protection strategies for different types of aging also differ. Furthermore, the thermo-oxidative aging resistance and ozone aging resistance of rubber materials are independent; excellent thermo-oxidative aging resistance does not necessarily mean that the rubber material also possesses ozone aging resistance.

[0003] To improve the ozone aging resistance of rubber, various antioxidants have been developed and applied industrially. Common rubber antioxidants include p-phenylenediamine (e.g., patent applications with publication numbers CN119330840A and CN114105895A), thiourea (e.g., patent application with publication number CN110229388A), and cycloene (e.g., patent application with publication number JP2020172577A). Among these, p-phenylenediamine antioxidants are the most widely used ozone antioxidants due to their excellent static and dynamic ozone protection effects. However, with increasingly harsh operating environments for rubber products (such as high ozone concentrations and long-term dynamic fatigue), existing antioxidants still suffer from insufficient protective effectiveness and limited protective durability, making it difficult to meet the long-term ozone aging resistance requirements of high-end rubber products. Summary of the Invention

[0004] The primary objective of this invention is to overcome the limited ozone aging resistance of existing rubbers and to provide the application of imidazolium compounds as antioxidants in rubber compositions.

[0005] The above-mentioned objective of this invention is achieved through the following technical solution: The application of imidazolium compounds as antioxidants in rubber compositions, wherein the antioxidants are additives for resisting ozone aging, and the imidazolium compounds include at least one compound having a structure as shown in Formula I:

[0006] Formula I in: R1 is hydrogen, C1~C 24 Alkyl, C2-C 24 alkenyl, C2-C 24 Alkyne group, C2-C 24 Alkoxyalkyl, C1-C 24 Hydroxyalkyl, C2-C 24 Cyanoalkyl, C3-C 24 Esteryl alkyl, C6-C 20 Aryl or C7~C 24 Aryl groups; R3, R4, and R5 are each independently hydrogen, C1-C6 alkyl, C2-C6 alkenyl, or C6-C6 alkyl. 12 Aryl; R2 and A - It is one of the following (a) to (b): (a) A - It pairs with the imidazolium cation via ionic bonds to form the imidazolium exosalt, where R2 is hydrogen and C1-C2. 24 Alkyl, C2-C 24 alkenyl, C2-C 24 Alkyne group, C2-C 24 Alkoxyalkyl, C1-C 24 Hydroxyalkyl, C2-C 24 Cyanoalkyl, C3-C 24 Esteryl alkyl, C6-C 20 Aryl or C7~C 24 Aryl alkyl group, and R1 and R2 are not both hydrogen; (b) A - It is covalently linked to R2, and then binds to the imidazole ring via R2 to form an imidazole inner salt, where R2 is C1 to C2. 24 Alkylene, C2-C 24 alkenyl, C2-C 24 Ethyne group, C6-C 20 aryl or C7~C 24 Aromatic alkyl groups.

[0007] Preferably, the A - When A pairs with an imidazolium cation via an ionic bond to form an imidazolium exosalt, - BF4 - PF6 - ClO4 - NO3 - HSO4 - H2PO4 - ROSO3 - , RSO3 - F- Cl - ,Br - I - ArSO3 - RCOO - RfCOO - ROPO3H - (RO)2PO2 - , RPO2H - SCN - N(CN)2 - C(CN)3 - N(SO2CF3)2 - N(SO2F)2 - N(SO2C2F5)2 - C n F 2n+1 SO3 - , RfSO3 - BF3R - BF3Rf - Or [M(Y)] p ] - Where R is C1 to C2. 12 Alkyl group, Ar is C6~C6 20 Aryl, Rf is C1~C 12 Fluoroalkyl, n is an integer from 1 to 12, M is a metal center, Y is a monovalent anion ligand, and p is an integer from 1 to 6; The A - When A is covalently linked to R2 and then to the imidazole ring via R2 to form an imidazole inner salt, - It can be a carboxylate group, sulfonate group, hydrogen phosphate group, phosphate ester group, or sulfate ester group.

[0008] More preferably, the C1 to C 12 The fluoroalkyl group is C1 to C2. 12 Perfluoroalkyl.

[0009] More preferably, p is 1, 2, 3, 4, 5 or 6.

[0010] More preferably, M is Fe 3+ Or Al 3+ .

[0011] More preferably, the Y is Cl - .

[0012] In this invention, C1 to C 12Alkyl refers to an alkyl group having 1 to 12 carbon atoms, wherein the number of carbon atoms is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12; the C1 to C1... 12 Fluoroalkyl refers to a fluoroalkyl group having 1 to 12 carbon atoms, wherein the number of carbon atoms is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12; the C1 to C12 carbon atoms are... 12 Perfluoroalkyl refers to perfluoroalkyl groups having 1 to 12 carbon atoms, wherein the number of carbon atoms is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12.

[0013] In this invention, C1 to C 24 Alkylene refers to an alkylene having 1 to 24 carbon atoms, wherein the number of carbon atoms is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24; the C2 to C3... 24 An alkenyl group refers to an alkenyl group having 2 to 24 carbon atoms, wherein the number of carbon atoms is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24; the C2 to C 24 The term "ethynyl group" refers to an ethynyl group having 2 to 24 carbon atoms, wherein the number of carbon atoms is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 or 24.

[0014] Preferably, R1 is hydrogen or C1~C1. 24 alkyl.

[0015] In this invention, C1 to C are mentioned throughout the text. 24 Alkyl refers to an alkyl group having 1 to 24 carbon atoms, wherein the number of carbon atoms is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 or 24.

[0016] Preferably, R3, R4, and R5 are each independently hydrogen or C1-C6 alkyl.

[0017] In this invention, the C1 to C6 alkyl refers to an alkyl group having 1 to 6 carbon atoms, wherein the number of carbon atoms is 1, 2, 3, 4, 5 or 6.

[0018] Preferably, the A - When R2 pairs with an imidazolium cation via an ionic bond to form an imidazolium exosalt, it is either hydrogen or C1-C2. 24 Alkyl, A - For Cl -CH3COO - CH3SO3 - ,Br - CF3SO3 - (C4H9O)2PO2 - H2PO4 - CF3COO - N(CN)2 - I - or OH - Furthermore, R1 and R2 are not both hydrogen.

[0019] Preferably, the A - When R2 is covalently linked to R2 and then binds to the imidazole ring via R2 to form an imidazole inner salt, R2 has a C1 to C2 configuration. 24 Alkylene, A - It is a sulfonate group.

[0020] In this invention, C1 to C 24 Alkylene refers to an alkylene having 1 to 24 carbon atoms, wherein the number of carbon atoms is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 or 24.

[0021] More preferably, R2 is a C1-C6 alkylene group; even more preferably, the C1-C6 alkylene group is a butylene group.

[0022] Preferably, the compound having the structure shown in Formula I is at least one of 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium methanesulfonate, 1-hexadecyl-3-methylimidazolium bromide, 1-sulfobutyl-3-methylimidazolium inner salt, 1-n-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium dibutyl phosphate, 1-vinyl-3-butylimidazolium chloride, 1-butyl-3-methylimidazolium dihydrogen phosphate, 1-butyl-2,3-dimethylimidazolium chloride, 1-butyl-3-methylimidazolium trifluoroacetate, 1-butyl-3-methylimidazolium bromide, 1-hexadecyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium dicyandiamide, 1-butyl-3-methylimidazolium iodide, or 1-butyl-3-methylimidazolium hydroxide.

[0023] When the compound having the structure shown in Formula I is a 1-butyl-3-methylimidazolium chloride, the rubber composition exhibits the best ozone resistance, especially dynamic ozone resistance.

[0024] The present invention does not impose any particular limitation on the source of compounds having the structure shown in Formula I, which can be prepared by conventional methods known in the art or by directly using commercially available products.

[0025] As an example, the compound having the structure shown in Formula I can be prepared by a method including but not limited to the following steps: The imidazole compound shown in Formula II is reacted with the haloalkane shown in Formula III under solvent conditions to undergo a quaternization reaction to generate an imidazole onium salt; the molar ratio of the compound shown in Formula II to the compound shown in Formula III can be 1:(1~1.2). Alternatively, the imidazole compound shown in Formula II can be reacted with the haloalkane shown in Formula III under solvent conditions to undergo a quaternization reaction, resulting in an imidazole salt, which is then passed through an anion exchange resin (such as OH). - The strong basic resin is converted into the corresponding imidazolium hydroxide; Alternatively, the imidazole compound shown in Formula II can be reacted with the haloalkane shown in Formula III under solvent conditions to undergo a quaternization reaction, resulting in an imidazole salt, which is then passed through an anion exchange resin (such as OH). - A strong basic resin is converted into the corresponding imidazolium hydroxide, which is then neutralized with the target acid to obtain the target ionic liquid; the target acid is selected from at least one of hydrochloric acid, hydrobromic acid, phosphoric acid, acetic acid, trifluoroacetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, or dibutylphosphonic acid; the imidazolium salt is preferably 1-butyl-3-methylimidazolium bromide or 1-butyl-3-methylimidazolium chloride; the molar ratio of the compound shown in Formula II or Formula III to the target acid can be 1:(1~1.2):(1~1.2); Alternatively, the imidazole compound shown in Formula II can be reacted directly with the target acid or an ester derivative of the target acid or a dicyandiamide salt to generate the target ionic liquid in one step; the target acid is selected from at least one of hydrochloric acid, hydrobromic acid, phosphoric acid, acetic acid, trifluoroacetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, or dibutylphosphine; the ester derivative of the target acid is selected from at least one of alkyl methanesulfonate, alkyl trifluoromethanesulfonate, trialkyl phosphate, or alkyl p-toluenesulfonate, preferably n-butyl methanesulfonate, n-butyl trifluoromethanesulfonate, or tributyl phosphate; the dicyandiamide salt is preferably sodium dicyandiamide; the molar ratio of the compound shown in Formula II to the target acid or an ester derivative of the target acid or a dicyandiamide salt can be 1:(1~1.2); Alternatively, when the anion is in the form of an inner salt such as a sulfonate, the imidazole compound shown in II can be reacted with the sulfonyl lactone to directly generate the imidazole sulfonate inner salt; the sulfonyl lactone is preferably 1,4-butane sulfonyl lactone; the molar ratio of the compound shown in II to the sulfonyl lactone can be 1:(1~1.2).

[0026]

[0027] Formula II

[0028] Formula III In Formula II, the definitions and preferred embodiments of R1, R2, R3, and R5 are the same as those of the corresponding groups in Formula I. In Formula III, R4 is selected from hydrogen, C1 to C2, C3, C4 ... 24 Alkyl, C2-C 24 alkenyl, C2-C 24 Alkyne group, C2-C 24 Alkoxyalkyl, C1-C 24 Hydroxyalkyl, C2-C 24 Carboxyl groups, C1-C 24 sulfonyl, C1-C 24 Cyanoalkyl, C3-C 24 Esteryl alkyl, C6-C 20 Aryl or C7~C 24 Aryl group, where X is selected from fluorine, chlorine, bromine, or iodine; Optionally, the solvent is selected from organic solvents, water, or mixtures thereof, preferably at least one of acetonitrile, dichloromethane, deionized water, and ethyl acetate; Optionally, the compound represented by Formula II is at least one of 1-methylimidazolium or 1-vinylimidazolium, and the compound represented by Formula III is at least one of 1-chlorobutane, 1-bromohexadecane, 1-iodobutane, or 1-chlorohexadecane, 1-bromobutane, or 1-chloropropane.

[0029] The crude product obtained by the above preparation method is washed and dried to obtain the target ionic liquid.

[0030] Optionally, the solvent used for washing includes, but is not limited to, at least one of ethyl acetate, petroleum ether, or anhydrous diethyl ether.

[0031] Optionally, the drying temperature is 40~70℃ and the drying time is 5~15 hours.

[0032] Preferably, the amount of the imidazolium compound added is 0.1 to 10 parts per 100 parts by weight of rubber.

[0033] Specifically, the amount of imidazolium compounds added can be within any range of 0.1 parts, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 10 parts, or more. It should be noted that 0.1 to 10 parts is the preferred amount to balance good mechanical properties and ozone resistance; when only ozone resistance is desired, the amount added can be greater than 10 parts.

[0034] Preferably, the weight-average molecular weight of the rubber is 5 × 10⁻⁶.4 ~2×10 6 g / mol; specifically, it can be 5 × 10⁻⁶ g / mol. 4 6×10 4 7×10 4 8×10 4 9×10 4 1×10 5 2×10 5 3×10 5 4×10 5 5×10 5 6×10 5 7×10 5 8×10 5 9×10 5 1×10 6 2×10 6 The range consisting of g / mol or any two of the above.

[0035] Preferably, the rubber refers to an elastomer formed by polymerizing monomers containing dienes.

[0036] More preferably, the diene includes at least one of butadiene, isoprene, 2-chloro-1,3-butadiene, dicyclopentadiene, or hexadiene.

[0037] Preferably, the rubber includes at least one of natural rubber (NR), butadiene rubber (BR), isoprene rubber, styrene-butadiene rubber (SBR), chloroprene rubber (CR), nitrile rubber (NBR), ethylene propylene diene monomer (EPDM), isoprene / butadiene copolymer, isoprene / styrene copolymer, or isoprene / butadiene / styrene copolymer.

[0038] In some preferred embodiments, the rubber comprises both natural rubber and butadiene rubber, and the mass ratio of natural rubber to butadiene rubber is 1:(0.2~5), preferably 1:(1~2). The natural rubber / butadiene rubber compound system is a commonly used rubber system in tire sidewall rubber, which can balance mechanical strength, flexural fatigue resistance and processing performance.

[0039] In some preferred embodiments, the rubber comprises both natural rubber and styrene-butadiene rubber (SBR), and the mass ratio of natural rubber to SBR is 1:(0.2~5), preferably 1:(1~2). The natural rubber / SBR compound system is a commonly used rubber system in semi-steel tire tread compounds, which can balance mechanical strength, abrasion resistance, and formulation adaptability.

[0040] It should be understood that any rubber can be used in the application of this invention. The invention is specifically illustrated using an elastomer formed by polymerizing monomers containing dienes as an example because such rubbers have a higher requirement for ozone resistance.

[0041] It should be understood that the rubber compound systems listed in this invention are merely examples to meet the application performance requirements of specific products, and these specific examples are not intended to limit the scope of protection of this invention.

[0042] Preferably, the rubber composition further comprises 0.1 to 120 parts of filler per 100 parts by weight of rubber, more preferably 5 to 110 parts, even more preferably 50 to 110 parts, and even more preferably 50 to 70 parts.

[0043] The fillers suitable for use in this invention can be fillers conventionally used in rubber compositions, including but not limited to at least one selected from carbon black, silica, titanium dioxide, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, clay, or talc, preferably carbon black and / or silica. Typically, the average particle size of the filler is 5 nm to 100 μm.

[0044] Preferably, the rubber composition further comprises 0.1 to 3 parts of crosslinking agent per 100 parts by weight of rubber, more preferably 0.5 to 1.8 parts.

[0045] More preferably, the crosslinking agent includes, but is not limited to, sulfur.

[0046] Preferably, the rubber composition further comprises 0.5 to 15 parts of softener per 100 parts by weight of rubber, more preferably 1 to 3 parts.

[0047] Optionally, the softener includes, but is not limited to, at least one of naphthenic oil, aromatic oil, paraffin, petroleum asphalt, petrolatum, castor oil, linseed oil, rapeseed oil, coconut oil, tall oil, linoleic acid, palmitic acid, lauric acid, beeswax, carnauba wax, or lanolin, preferably aromatic oil and / or naphthenic oil.

[0048] Preferably, the rubber composition further comprises 1 to 10 parts of activator, more preferably 3 to 8 parts, per 100 parts by weight of rubber.

[0049] Optionally, the activator includes, but is not limited to, at least one of stearic acid or zinc oxide.

[0050] In some preferred embodiments, the activator comprises both stearic acid and zinc oxide in a mass ratio of 1:(1~6).

[0051] Preferably, the rubber composition further comprises 0.2 to 5 parts of accelerator per 100 parts by weight of rubber.

[0052] More preferably, the accelerator is a vulcanization accelerator, including but not limited to at least one of sulfonamide vulcanization accelerators, thiazole vulcanization accelerators, thiuram vulcanization accelerators, guanidine vulcanization accelerators, dithiocarbamate vulcanization accelerators, aldehyde-amine vulcanization accelerators, aldehyde-amine vulcanization accelerators, imidazoline vulcanization accelerators, or xanthic acid vulcanization accelerators.

[0053] More preferably, the accelerator is at least one of accelerator D (1,3-diphenylguanidine), accelerator NS (N-tert-butyl-2-benzothiazole sulfenamide), accelerator TMTD (tetramethylthiuram disulfide), accelerator CZ (N-cyclohexyl-2-benzothiazole sulfenamide), accelerator MBT (2-thiol-benzothiazole), or accelerator DM (2,2'-dithiodibenzothiazole).

[0054] In some preferred embodiments, the accelerator simultaneously comprises accelerator D (1,3-diphenylguanidine), accelerator TMTD (tetramethylthiuram disulfide), and accelerator CZ (N-cyclohexyl-2-benzothiazole sulfenamide), with a mass ratio of 1:(0.1~4):(0.1~2), preferably 1:(0.1~0.5):(0.2~0.5).

[0055] In some preferred embodiments, the accelerator comprises both accelerator DM (2,2'-dithiodibenzothiazole) and accelerator MBT (2-thiol-benzothiazole) in a mass ratio of 1:(0.1~3), preferably 1:(0.3~1).

[0056] Preferably, the rubber composition further comprises 0 to 5 parts of tackifying resin per 100 parts by weight of rubber.

[0057] Optionally, the tackifying resin includes, but is not limited to, at least one of petroleum resin, octylphenol tackifying resin, or rosin resin.

[0058] Preferably, the rubber composition further comprises 0 to 10 parts of plasticizer per 100 parts by weight of rubber, more preferably 3 to 6 parts.

[0059] Optionally, the plasticizer includes, but is not limited to, at least one of 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), or DCHP (dicyclohexyl phthalate).

[0060] Preferably, the rubber composition further comprises 0 to 10 parts of coupling agent per 100 parts by weight of rubber.

[0061] Optionally, the coupling agent is a silane coupling agent, including but not limited to at least one of bis-[γ-(triethoxysilane)propyl]tetrasulfide, 3-octanoylthiopropyltriethoxysilane, 3-thiocyanopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, or bis-[3-(triethoxysilane)propyl]-disulfide.

[0062] It should be noted that the other components in the rubber composition of the present invention, besides the compound having the structure shown in Formula I, including fillers, softeners, activators, accelerators, plasticizers, tackifying resins, etc., are all conventional additives in the art, and their types and amounts can be conventionally selected and adjusted according to actual functional requirements. Even if one or more of the above-mentioned additives are missing, it does not affect the compound having the structure shown in Formula I from performing its expected technical effect as an antioxidant in the present invention.

[0063] Preferably, the preparation process of the rubber composition includes the following steps: first, mixing the rubber with components other than the crosslinking agent and accelerator, then adding the crosslinking agent and accelerator, mixing again, and then vulcanizing to obtain the rubber composition.

[0064] More preferably, the preparation process of the rubber composition includes the following steps: S1. The rubber is mixed with the components other than the crosslinking agent and accelerator in an internal mixer, and the rubber is discharged to obtain a first-stage compound; S2. The first-stage compound is re-mixed in a two-roll mill, crosslinking agent and accelerator are added, mixed, and sheeted to obtain the second-stage compound; S3. The two-stage compound is vulcanized to obtain the rubber composition.

[0065] More preferably, in step S1, the timing of the glue discharge is when the temperature of the glue material rises to the set glue discharge temperature.

[0066] More preferably, the glue discharge temperature is 110~170℃.

[0067] More preferably, in step S2, the temperature of the sheet being extruded is 35~110℃.

[0068] More preferably, in step S3, the vulcanization temperature is 135~200℃ and the time is 6~60min.

[0069] In this invention, the rubber composition is suitable for preparing various rubber products, especially those requiring long-term ozone aging resistance, such as tires, rubber shoes, sealing strips, sound insulation panels, or vibration damping pads. It is particularly suitable for tire products, specifically as a sidewall rubber or tread rubber.

[0070] Compared with the prior art, the beneficial effects of the present invention are: This invention uses imidazolium compounds with the structure shown in Formula I as antioxidants for rubber compositions. While maintaining the good physical and mechanical properties of the rubber composition, it significantly improves the static and dynamic anti-ozone aging properties of the rubber composition. Compared with the traditional antioxidant 6PPD, imidazolium compounds with the structure shown in Formula I require only a lower dosage, and the rubber composition can exhibit superior crack resistance under the same ozone aging conditions, thereby effectively extending the service life of rubber products. The reason for this is presumably that the imidazolium heterocycle in the imidazolium compounds with the structure shown in Formula I can act as a preferential site for ozone or ozone oxidation intermediates, competitively consuming ozone and reducing the direct attack of ozone on the double bonds of the main molecular chain on the surface of the rubber composition. This delays the initiation and propagation of ozone cracks, improving the static and dynamic anti-ozone aging properties of the rubber composition. Detailed Implementation

[0071] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0072] The following describes some of the raw materials or reagents used in the embodiments and comparative examples of this invention: I. Compounds having the structure shown in Formula I

[0073] Formula I (1) In compounds having the structure shown in Formula I, R1 and R2 are selected as n-butyl and methyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - For Cl - That is, the compound having the structure shown in Formula I is 1-butyl-3-methylimidazolium chloride, which is commercially available and denoted as antioxidant A; (2) In compounds having the structure shown in Formula I, R1 and R2 are selected as n-butyl and methyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - CH3COO - The compound having the structure shown in Formula I is 1-butyl-3-methylimidazolium acetate, which is commercially available and designated as antioxidant B. (3) In compounds having the structure shown in Formula I, R1 and R2 are selected as n-butyl and methyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - CH3SO3 - The compound having the structure shown in Formula I is 1-butyl-3-methylimidazolium methanesulfonate, which is commercially available and denoted as antioxidant C. (4) In compounds having the structure shown in Formula I, R1 and R2 are selected as hexadecyl and methyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - For Br - The compound having the structure shown in Formula I is 1-hexadecyl-3-methylimidazolium bromide, commercially available, and designated as antioxidant D. (5) In compounds having the structure shown in Formula I, R1 is a methyl group; A - It is covalently bonded to R2; R2 is butylene; A - R3 is a sulfonate group; R4, R5 are each hydrogen atoms; that is, the compound having the structure shown in Formula I is a 1-sulfobutyl-3-methylimidazolium salt, commercially available, and denoted as antioxidant E; (6) In compounds having the structure shown in Formula I, R1 and R2 are selected as n-butyl and methyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - CF3SO3 - The compound having the structure shown in Formula I is 1-n-butyl-3-methylimidazolium trifluoromethane sulfonate, which is commercially available and denoted as antioxidant F. (7) In compounds having the structure shown in Formula I, R1 and R2 are selected as butyl and methyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - (C4H9O)2PO2 - The compound having the structure shown in Formula I is 1-butyl-3-methylimidazolium dibutyl phosphate salt, commercially available, and designated as antioxidant G. (8) In compounds having the structure shown in Formula I, R1 and R2 are selected as vinyl and n-butyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - For Cl - That is, the compound having the structure shown in Formula I is 1-vinyl-3-butylimidazolium chloride, which is commercially available and denoted as antioxidant H; (9) In compounds having the structure shown in Formula I, R1 and R2 are selected as butyl and methyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - H2PO4 - That is, a compound having the structure shown in Formula I: 1-Butyl-3-methylimidazolium dihydrogen phosphate, commercially available, denoted as Antioxidant I; (10) In compounds having the structure shown in Formula I, R1 and R2 are selected as n-butyl and methyl, respectively; R3 is methyl, and R4 and R5 are each independently hydrogen; anion A - For Cl - The compound having the structure shown in Formula I is 1-butyl-2,3-dimethylimidazolium chloride, which is commercially available and denoted as antioxidant J. (11) In compounds having the structure shown in Formula I, R1 and R2 are selected as n-butyl and methyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - For CF3COO - The compound having the structure shown in Formula I is 1-butyl-3-methylimidazolium trifluoroacetate, commercially available, with a purity ≥99.0%, and is designated as antioxidant K. (12) In compounds having the structure shown in Formula I, R1 and R2 are selected as n-butyl and methyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - For Br - The compound having the structure shown in Formula I is 1-butyl-3-methylimidazolium bromide, commercially available, and denoted as antioxidant L. (13) In compounds having the structure shown in Formula I, R1 and R2 are selected as n-butyl and methyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - Dicyandiamide N(CN)2 - The compound having the structure shown in Formula I is 1-butyl-3-methylimidazolium dicyandiamide salt, commercially available, and denoted as antioxidant M. (14) In compounds having the structure shown in Formula I, R1 and R2 are selected as n-butyl and methyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - For I - That is, the compound having the structure shown in Formula I is 1-butyl-3-methylimidazolium iodide, which is commercially available and denoted as antioxidant N; (15) In compounds having the structure shown in Formula I, R1 and R2 are selected as hexadecyl and methyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - For Cl - The compound having the structure shown in Formula I is 1-hexadecyl-3-methylimidazolium chloride, commercially available, and designated as antioxidant O. (16) In compounds having the structure shown in Formula I, R1 and R2 are selected as n-butyl and methyl, respectively; R3, R4, and R5 are each independently hydrogen; anion A - OH - The compound having the structure shown in Formula I is 1-butyl-3-methylimidazolium hydroxide, commercially available, and denoted as antioxidant P.

[0074] II. Other Anti-aging agent Q: Non-imidazolium quaternary phosphonium salt ionic liquid tributyl-n-tetradecyl phosphonium chloride, commercially available; Anti-aging agent 6PPD, commercially available; Natural rubber: Xishuangbanna Sinochem Rubber Co., Ltd., SCR5; Butadiene rubber: PetroChina Daqing, BR9000; SSBR: Jilin Chemical Co., Ltd., 2466; NBR: Zeon Corporation, Japan, DN003; EPDM: Jilin Chemical Co., Ltd., 3080; Carbon black N660, carbon black N330, carbon black N550 and carbon black N234 were all purchased from Cabot Corporation; Silica: TSRC Corporation, GR9000; Silane coupling agent: bis-[γ-(triethoxysilyl)propyl]tetrasulfide, Aladdin Reagents Ltd., AR; Zinc oxide, stearic acid, accelerator NS, accelerator D, accelerator TMTD, accelerator CZ, accelerator DM, accelerator MBT and sulfur were all purchased from Aladdin Reagent Co., Ltd. Aromatic oil: Shanghai Titan, AR.

[0075] Examples 1-19 and Comparative Examples 1-2 Examples 1-19 and Comparative Examples 1-2 provide a series of rubber compositions, prepared by the following process: (1) Add all components except accelerator and sulfur to the internal mixer and knead until the rubber temperature rises to 130°C and then discharge the rubber to obtain a first-stage compound. (2) After the first stage of compound is cooled, the first stage of compound is rolled on a rolling mill, accelerator NS and sulfur are added, and kneaded until the temperature of the rubber compound reaches 70°C and then sheeted out to obtain the second stage of compound. (3) The two-stage compound was vulcanized (at a temperature of 145°C for 35 minutes) to obtain a rubber composition; The amounts of each component in Examples 1-19 and Comparative Examples 1-2 are shown in Tables 1 and 2.

[0076] Example 20 and Comparative Example 3 Examples 20 and Comparative Example 3 provide a series of rubber compositions prepared by the following process: (1) Add all components except accelerator and sulfur to the internal mixer and knead until the rubber temperature rises to 150°C and then discharge the rubber to obtain a first-stage compound. (2) After the first stage of compound rubber cools down, the first stage of compound rubber is rolled on a rolling mill, and accelerator D, accelerator NS and sulfur are added. When the rubber temperature reaches 70°C, the mixture is sheeted out to obtain the second stage of compound rubber. (3) The two-stage compound was vulcanized (at a temperature of 150°C for 35 minutes) to obtain a rubber composition; The amounts of each component in Example 20 and Comparative Example 3 are shown in Table 3.

[0077] Example 21 and Comparative Example 4 Examples 21 and Comparative Example 4 provide a series of rubber compositions prepared by the following process: (1) Add all components except accelerator and sulfur to the internal mixer and knead until the rubber temperature rises to 110°C and then discharge the rubber to obtain a first-stage compound. (2) After the first stage of compound rubber cools down, the first stage of compound rubber is refining on a two-roll mill, and accelerator D, accelerator TMTD, accelerator CZ and sulfur are added to obtain the second stage of compound rubber. (3) The two-stage compound was vulcanized (at a temperature of 170°C for 30 minutes) to obtain a rubber composition; The amounts of each component in Example 21 and Comparative Example 4 are shown in Table 4.

[0078] Example 22 and Comparative Example 5 Examples 22 and Comparative Example 5 provide a series of rubber compositions prepared by the following process: (1) Add all components except accelerator and sulfur to the internal mixer and knead until the rubber temperature rises to 100°C and then discharge the rubber to obtain a first-stage compound. (2) After the first stage of compound is cooled, the first stage of compound is milled on a two-roll mill, and accelerator DM, accelerator MBT and sulfur are added to obtain the second stage of compound. (3) The two-stage compound was vulcanized (at a temperature of 170°C for 30 minutes) to obtain a rubber composition; The amounts of each component in Example 22 and Comparative Example 5 are shown in Table 5.

[0079] Example 23 and Comparative Example 6 Examples 23 and Comparative Example 6 provide a series of rubber compositions prepared by the following process: (1) Add all components except accelerator and sulfur to the internal mixer and knead until the rubber temperature rises to 130°C and then discharge the rubber to obtain a first-stage compound. (2) After the first stage of compound is cooled, the first stage of compound is milled on a two-roll mill, and accelerator NS and sulfur are added to obtain the second stage of compound. (3) The two-stage compound was vulcanized (at a temperature of 143°C for 40 min) to obtain a rubber composition; The amounts of each component in Example 23 and Comparative Example 6 are shown in Table 6.

[0080] Performance testing I. Physical and Mechanical Performance Testing The test was conducted in accordance with GB / T528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber".

[0081] II. Ozone Aging Test The rubber composition was subjected to ozone aging test in an ozone aging test chamber according to the following standards: Static ozone aging: GB / T 7762-2014 "Static tensile test for ozone cracking resistance of vulcanized rubber or thermoplastic rubber"; Dynamic ozone aging: GB / T 13642-2015 "Dynamic tensile test for ozone cracking resistance of vulcanized rubber or thermoplastic rubber"; Crack grade evaluation: GB / T 11206-2009 "Rubber Aging Test - Surface Cracking Method", the grades from best to worst are 0, 1a, 1b, 1c, 2a, 2b, 2c, 3a, 3b, 3c, 4a, 4b, 4c; The specific test parameters are as follows: ozone volume concentration 50 pphm, temperature (40±2)℃, humidity (60±5)%. During static testing, the sample was pre-stretched by 20%, and cracking was observed periodically. During dynamic testing, the sample was pre-stretched by 20%, dynamically stretched by 20%, at a frequency of 0.5Hz, and cracking was observed.

[0082] The performance test results of each embodiment and comparative example are shown in Tables 1-6.

[0083] Table 1

[0084] Table 2

[0085] Table 3

[0086] Table 4

[0087] Table 5

[0088] Table 6

[0089] As shown in Tables 1-6, when compounds with the structure shown in Formula I are added to rubber compositions, the resulting rubber compositions still maintain good physical and mechanical properties, with tensile strength of 8-20.5 MPa, elongation at break of 278-550%, and crack grade of 2c or above after 144 hours of static ozone aging, and crack grade of 3b or above after 144 hours of dynamic ozone aging. This indicates that compounds with the structure shown in Formula I have good compatibility with rubber, and while imparting ozone aging resistance to rubber compositions, they do not significantly reduce the basic mechanical properties of rubber compositions.

[0090] The results from Examples 1-4 show that as the amount of the compound having the structure shown in Formula I increases, the static and dynamic ozone aging resistance of the rubber composition gradually increases.

[0091] As can be seen from Examples 1 and Comparative Example 1, and Examples 20-23 and Comparative Examples 3-6, compared with the traditional antioxidant 6PPD, the compound having the structure shown in Formula I requires only a lower dosage, and the rubber composition can exhibit better crack resistance under the same ozone aging conditions, thereby effectively extending the service life of rubber products.

[0092] As can be seen from Example 1 and Comparative Example 2, ionic liquids using compounds that do not have the structure shown in Formula I cannot achieve better ozone aging resistance.

[0093] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. The application of imidazolium compounds as antioxidants in rubber compositions, characterized in that, The antioxidant is an adjuvant for combating ozone aging, and the imidazolium-type compound includes at least one compound having the structure shown in Formula I: Formula I in: R1 is hydrogen, C1~C 24 Alkyl, C2-C 24 alkenyl, C2-C 24 Alkyne group, C2-C 24 Alkoxyalkyl, C1-C 24 Hydroxyalkyl, C2-C 24 Cyanoalkyl, C3-C 24 Esteryl alkyl, C6-C 20 Aryl or C7~C 24 Aryl alkyl groups; R3, R4, and R5 are each independently hydrogen, C1-C6 alkyl, C2-C6 alkenyl, or C6-C6 alkyl. 12 Aryl; R2 and A - It is one of the following (a) to (b): (a) A - When R2 pairs with an imidazolium cation via an ionic bond to form an imidazolium exosalt, it is either hydrogen or C1-C2. 24 Alkyl, A - For Cl - CH3COO - CH3SO3 - ,Br - CF3SO3 - (C4H9O)2PO2 - H2PO4 - CF3COO - N(CN)2 - I - or OH - Furthermore, R1 and R2 are not both hydrogen; (b) A - When R2 is covalently linked to R2 and then binds to the imidazole ring via R2 to form an imidazole inner salt, R2 is a butylene group, A - It is a sulfonate group.

2. The application as described in claim 1, characterized in that, The compound having the structure shown in Formula I satisfies at least one of the following (1) to (2): (1) R1 is hydrogen or C1~C 24 alkyl; (2) R3, R4 and R5 are each independently hydrogen or C1 to C6 alkyl.

3. The application as described in claim 1, characterized in that, The compound having the structure shown in Formula I is at least one of 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium methanesulfonate, 1-hexadecyl-3-methylimidazolium bromide, 1-sulfobutyl-3-methylimidazolium inner salt, 1-n-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium dibutyl phosphate, 1-vinyl-3-butylimidazolium chloride, 1-butyl-3-methylimidazolium dihydrogen phosphate, 1-butyl-2,3-dimethylimidazolium chloride, 1-butyl-3-methylimidazolium trifluoroacetate, 1-butyl-3-methylimidazolium bromide, 1-hexadecyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium dicyandiamide, 1-butyl-3-methylimidazolium iodide, or 1-butyl-3-methylimidazolium hydroxide.

4. The application as described in claim 1, characterized in that, The amount of the imidazolium compound added is 0.1 to 10 parts per 100 parts by weight of rubber.

5. The application as described in claim 1, characterized in that, The rubber refers to an elastomer formed by the polymerization of monomers containing dienes.

6. The application as described in claim 5, characterized in that, The diene includes at least one of butadiene, isoprene, 2-chloro-1,3-butadiene, dicyclopentadiene, or hexadiene.

7. The application as described in claim 1, characterized in that, The rubber composition satisfies at least one of the following (1) to (9): (1) The rubber includes at least one of natural rubber, butadiene rubber, isoprene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, ethylene propylene diene monomer (EPDM) rubber, isoprene / butadiene copolymer, isoprene / styrene copolymer or isoprene / butadiene / styrene copolymer; (2) The rubber composition further comprises 0.1 to 120 parts of filler per 100 parts by weight of rubber; (3) The rubber composition further comprises 0.1 to 3 parts of crosslinking agent per 100 parts by weight of rubber; (4) The rubber composition further comprises 0.5 to 15 parts of softener per 100 parts by weight of rubber; (5) The rubber composition further comprises 1 to 10 parts of activator per 100 parts by weight of rubber; (6) The rubber composition further comprises 0.2 to 5 parts of accelerator per 100 parts by weight of rubber; (7) The rubber composition further comprises 0 to 5 parts of tackifying resin per 100 parts by weight of rubber; (8) The rubber composition further comprises 0 to 10 parts of plasticizer per 100 parts by weight of rubber; (9) The rubber composition further comprises 0 to 10 parts of coupling agent per 100 parts by weight of rubber.

8. The application as described in claim 1, characterized in that, The preparation process of the rubber composition includes the following steps: First, the rubber is mixed with components other than the crosslinking agent and accelerator. Then, the crosslinking agent and accelerator are added and mixed again before vulcanization to obtain the rubber composition.

9. The application as described in claim 1, characterized in that, The rubber composition is used to prepare tires, rubber shoes, sealing strips, sound insulation panels, or vibration damping pads.

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