Anti-aging agent resistant to damp-heat aging and ozone aging, rubber composition and application thereof

Abstract

The invention provides a compound as shown in a formula A which can be used as an anti-aging agent, an anti-aging agent composition containing the compound as shown in the formula A and an anti-aging agent STMQ, a rubber composition containing the anti-aging agent composition or the compound as shown in the formula A and application of the rubber composition. The compound of formula A is as described herein. The anti-aging agent and the anti-aging agent composition provided by the invention can significantly improve the damp-heat aging resistance of a tire rubber material, also have good ozone aging resistance, and prolong the service life of a tire in a special and severe environment.

Description

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 application thereof. Background Art

[0002] During the storage, processing and use of rubber products, the performance of rubber products will decline or be lost due to the effects of their own factors and environmental factors (heat, oxygen, ozone, ultraviolet rays, chemicals, etc.). Oxygen is an important factor in rubber aging, and the absorption of heat energy is the main factor in the pyrolysis of polymer materials in a vacuum or inert environment. At the same time, heat energy can also accelerate the oxidation reaction of rubber products. Ozone is more active than oxygen, so it is more aggressive than oxygen to rubber, especially unsaturated rubber. The reaction of ozone with rubber double bonds will accelerate the generation and growth of cracks; in addition, with the increase of ozone concentration, the time for cracks to appear is shortened, and the crack growth rate increases accordingly.

[0003] At present, physical antioxidants and chemical antioxidants are commonly added to tire formulas to improve the tire's ozone aging resistance, including static and dynamic performance. Among them, chemical antioxidants, especially 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 because of their good comprehensive protection properties (ozone, thermal oxygen and dynamic fatigue performance).

[0004] Water (precipitation, humidity, condensation, etc.) also plays an important role in accelerating the aging of rubber products. The extraction 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 the external environment of rubber products is used and stored in more harsh conditions, such as in a high temperature and high humidity environment, the water solubility (water extraction resistance) of different antioxidants varies greatly, causing the concentration / ratio of antioxidants in the rubber to decrease significantly, and ultimately leading to a significant decrease in the protective effect of rubber products. Related literature discloses that the hot water extraction resistance of antioxidants IPPD and 6PPD is poor. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides an antioxidant with the effects of resistance to wet heat aging and resistance to ozone aging, an antioxidant composition containing the antioxidant, a rubber composition containing the antioxidant or the antioxidant composition and uses thereof. The antioxidant and the antioxidant composition of the present invention can significantly improve the resistance to wet heat aging of the rubber composition, such as tire rubber material, while maintaining the original physical properties and heat and oxygen aging resistance of the rubber composition, and at the same time have good resistance to ozone aging, thereby increasing the service life of rubber products, such as tires, in special and harsh environments.

[0007] Specifically, one aspect of the present invention provides a compound of formula A which can be used as an antioxidant:

[0008]

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

[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]

[0013] In one or more embodiments, the compound of formula A does not include a compound in which R1 and R2 are methyl and R3 is isopropyl.

[0014] Another aspect of the present invention provides an antioxidant composition, which comprises an antioxidant STMQ and a compound of formula A as 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%.

[0015] 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.

[0016] Another aspect of the present invention provides a rubber composition, 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 as described in any embodiment of the present invention, or the raw materials of the rubber composition include 100 parts by mass of a diene elastomer and 1-5 parts by mass of an antioxidant composition as described in any embodiment of the present invention.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] In one or more embodiments, the raw materials of the rubber composition further include 0.5-3 parts by mass of sulfur.

[0022] 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.

[0023] Another aspect of the present invention provides a rubber product, wherein the rubber product comprises the rubber composition described in any embodiment of the present invention; preferably, the rubber product is a tire.

[0024] 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

[0025] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0026] 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.

[0027] 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 be disclosed herein.

[0028] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are only for brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0029] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0030] Herein, when describing embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all substitutes, improvements and equivalents of the methods and materials described in the present invention can be included in the scope limited by the claims.

[0031] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0032] In the present invention, the compound of formula A has the following structure:

[0033]

[0034] In formula A, R1, R2 and R3 are each independently selected from C1-C8 alkyl groups.

[0035] In the present invention, alkyl refers to a linear or branched monovalent saturated hydrocarbon group. The 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.

[0036] In formula A, R1 can be located at the ortho, meta or para position of the -NH- group on the benzene ring, and R2 can be located at the ortho, meta or para position of R1. In some embodiments, R1 is located at the ortho position of the -NH- group on the benzene ring, and R2 is located at the ortho position of R1. In some embodiments, R1 is located at the meta position of the -NH- group on the benzene ring, and R2 is located at the para position of the -NH- group on the benzene ring.

[0037] Preferably, in formula A, R1 and R2 are each independently selected from C1-C4 alkyl, more preferably selected from C1-C3 alkyl, for example, selected from methyl and ethyl.

[0038] Preferably, in formula A, R3 is selected from C3-C8 alkyl, more preferably selected from C3-C6 alkyl or C4-C6 alkyl, for example selected from isopropyl, 1-methylpropyl, 1-methylbutyl and 1,3-dimethylbutyl.

[0039] 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.

[0040] 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:

[0041]

[0042]

[0043] The present invention finds that the use of the compound of formula A in a rubber composition, especially a tire rubber composition, can significantly improve the wet heat aging resistance and ozone aging resistance of the rubber composition, and the improvement effect is significantly better than that of a traditional p-phenylenediamine antioxidant (such as IPPD), while maintaining good original physical properties and heat-oxidation aging resistance. The present invention also finds that the combination of the compound of formula A and the antioxidant STMQ in a rubber composition, especially a tire rubber composition, can significantly improve the wet heat aging resistance and ozone aging resistance of the rubber composition, and the improvement effect is significantly better than that of a combination of a traditional p-phenylenediamine antioxidant (such as IPPD) and the antioxidant STMQ, while maintaining good original physical properties and heat-oxidation aging resistance.

[0044] In the present invention, the antioxidant STMQ refers to a 2,2,4-trimethyl-1,2-dihydroquinoline polymer having a total mass fraction of di-, tri- 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 a structure shown in formula B:

[0045]

[0046] In formula B, n represents the degree of polymerization.

[0047] In the present invention, the compound of formula A can be prepared by a method comprising the following steps:

[0048] (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;

[0049]

[0050] (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;

[0051]

[0052] 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.

[0053] 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 the present invention include sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. Suitable alkali metal alkoxides for 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, etc. Quaternary ammonium bases are a class of compounds with the general formula R 1 4NOH, 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, iodine. Examples of the combination of an alkali metal hydroxide and a tetraalkylammonium halide include sodium hydroxide and tetrabutylammonium bromide, etc.

[0054] 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, such as 1.05:1, 1.1:1, 1.5:1. In some embodiments, in step (1), the compound of formula C and the first catalyst are first salified, and then nitrobenzene is added dropwise to carry out a condensation reaction.

[0055] In step (1), the condensate obtained by the condensation reaction of the compound of formula C and nitrobenzene under the action of the first catalyst may be one or both of the nitro compound of formula D and the nitroso compound of formula D', and may also include an azobenzene compound.

[0056] 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, such as 6:1 or 7:1.

[0057] In step (1), the condensation reaction can be carried out at 40 to 90° C., preferably 65 to 85° C., for example, the reaction temperature can be 60° C., 70° C., 75° C., 80° C. The condensation reaction needs to be carried out under vacuum conditions, with a pressure range of -0.09 to -0.1 MPa.

[0058] 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 metals as catalytic active centers and carriers for supporting metals. The metals suitable for the supported metal catalysts of the present invention can be nickel, cobalt, copper, platinum, palladium, ruthenium, rhodium, etc., and the carrier can be carbon, alumina, silica gel, molecular sieves, etc., and the carbon as a 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.

[0059] In step (1), the condensate generated by the condensation reaction is subjected to a hydrogenation reduction reaction under the action of a second catalyst to generate 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 in the reduction reaction can be 0.5 to 5 MPa, for example, 1 MPa, 1.5 MPa, 2 MPa, or 2.5 MPa.

[0060] 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 separated into phases, and the organic phase is subjected to reduced pressure distillation to remove light components to obtain the compound of formula E.

[0061] The third catalyst used in step (2) may 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 may be 0.0001:1 to 0.2:1.

[0062] 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, 120°C. The hydrogen pressure in step (2) can be 0.5 to 5MPa, for example, 1MPa, 1.5MPa, 2MPa, 2.5MPa.

[0063] 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 reduced pressure distillation to obtain the compound of formula A.

[0064] 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.

[0065] The antioxidant composition of the present invention comprises (1) one or more compounds of formula A, and (2) antioxidant STMQ. In some embodiments, the antioxidant composition of the present invention consists of compounds of formula A and antioxidant STMQ. In the antioxidant composition of the present invention, the mass ratio of compound of formula A to antioxidant STMQ can be 1:1 to 3:1, for example 1.5:1, 2:1, 2.5:1.

[0066] The raw materials of the rubber composition generally include a diene elastomer, a reinforcing filler, an antioxidant and a crosslinking agent. Herein, the rubber composition includes unvulcanized rubber and vulcanized rubber. The unvulcanized rubber can be vulcanized (cured) to obtain vulcanized rubber.

[0067] The raw materials of the rubber composition of the present invention include a diene elastomer and one or more compounds of formula A, wherein the amount of the compound of formula A may 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. Herein, unless otherwise specified, the mass parts of other components in the raw materials of the rubber composition are calculated based on 100 parts by mass of the diene elastomer in the raw materials of the rubber composition.

[0068] 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 antioxidant composition of the present invention is used in an amount of 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.

[0069] Herein, diene elastomer refers to an elastomer whose monomers include dienes (such as butadiene, isoprene). Suitable diene elastomers for 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), cis-1,4-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, diene elastomer includes natural rubber and cis-1,4-butadiene rubber, or is composed of natural rubber and cis-1,4-butadiene rubber. The mass ratio of natural rubber and cis-1,4-butadiene rubber is preferably 1:2 to 2:1, such as 1:1.5 to 1.5:1, 4.5:5.5 to 5.5:4.5, 1:1.

[0070] 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, such as 1.5 parts by mass, 2 parts by mass, and 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.

[0071] In some embodiments, the raw material of the rubber composition 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 the rubber composition of the present invention, the consumption of the 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, and 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 of the antioxidant composition of the present invention is controlled within the aforementioned range to be conducive to ensuring the effect of improving the wet heat aging resistance and the ozone aging resistance under a relatively low consumption.

[0072] 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 includes the compound of formula A and the antioxidant STMQ.

[0073] The raw material of the rubber composition of the present invention may include reinforcing filler. In the raw material of the rubber composition of the present invention, the amount of reinforcing filler can be 30-70 mass parts, such as 40 mass parts, 45 mass parts, 50 mass parts, 55 mass parts, 60 mass parts. Reinforcing filler suitable for the present invention can be a conventional reinforcing filler for rubber composition, including but not limited to one or more selected from carbon black, white carbon black, titanium oxide, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, clay and talcum. In some preferred embodiments, reinforcing filler comprises carbon black, or reinforcing filler is carbon black.

[0074] The raw materials of the rubber composition of the present invention include a crosslinking agent, such as sulfur. In the raw materials of the rubber composition of the present invention, the amount of sulfur used can be 0.5-3 parts by mass, such as 1 part by mass, 1.5 parts by mass, 2 parts by mass, and 2.5 parts by mass.

[0075] 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, activators and accelerators.

[0076] Softener can be used to improve the processing properties of rubber composition. Softener can include petroleum softener, such as naphthenic oil, aromatic oil, process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, vaseline, etc., and can also include fatty oil softener, such as stearic acid, castor oil, linseed oil, rapeseed oil, coconut oil, wax (such as beeswax, carnauba wax and lanolin), tall oil, linoleic acid, palmitic acid, lauric acid, etc. In the raw material of rubber composition of the present invention, the amount of softener can be 2-15 mass parts, such as 3 mass parts, 5 mass parts, 7 mass parts, 8 mass parts, 9 mass parts, 10 mass parts, 11 mass parts, 13 mass parts. In some preferred embodiments, softener includes aromatic oil and stearic acid, or is composed of aromatic oil and stearic acid. The mass ratio of aromatic oil and stearic acid can be 1:1 to 5:1, such as 2:1, 3:1, 3.5:1, 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.

[0077] The protective wax can migrate from the inside of the rubber to the surface to form a wax film, which plays a role in 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 parts by mass, such as 1.5 parts by mass, 2 parts by mass, 3 parts by mass, and 4 parts by mass.

[0078] The activating agent can accelerate the vulcanization speed, improve the thermal conductivity, wear resistance, tear resistance and the like of rubber. In the raw material of the rubber composition of the present invention, the amount of the activating agent can be 1-10 mass parts, such as 2 mass parts, 3 mass parts, 4 mass parts, 5 mass parts, 6 mass parts, 7 mass parts, 8 mass parts, 9 mass parts. In some preferred embodiments, the activating agent includes ZnO, or the activating agent is ZnO. In some preferred embodiments, in the raw material of the rubber composition of the present invention, the amount of ZnO is 3-8 mass parts, such as 4 mass parts, 5 mass parts, 6 mass parts, 7 mass parts.

[0079] The accelerator is usually a vulcanization accelerator, which can be selected from sulfonamide vulcanization accelerators, thiazole vulcanization accelerators, thiuram vulcanization accelerators, thiourea vulcanization accelerators, guanidine vulcanization accelerators, dithiocarbamate vulcanization accelerators, aldehyde amine vulcanization accelerators, aldehyde ammonia vulcanization accelerators, imidazoline vulcanization accelerators and xanthogenic acid vulcanization accelerators. In the raw materials of the rubber composition of the present invention, the amount of the 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, the accelerator is accelerator NS (N- tert-butyl -2-benzothiazole sulfonamide).

[0080] In addition, when necessary, the rubber composition may also contain 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), etc. The amount of the plasticizer may be a conventional amount in the art.

[0081] 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.

[0082] 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 (e.g., internal mixer) mixing, mixing the rubber composition raw materials except the crosslinking agent and the accelerator, kneading the entire mixture until the maximum temperature between 110°C and 190°C is reached to obtain a first stage of rubber; a second stage of thermomechanical (e.g., open mixer) mixing, after the first stage of rubber is cooled, mixing the first stage of rubber with the crosslinking agent and the accelerator until the maximum temperature is below 110°C to obtain a second stage of rubber, i.e., the unvulcanized rubber.

[0083] Vulcanized rubber can be obtained by vulcanizing (curing) the unvulcanized rubber. The vulcanization temperature is usually 130-200°C, such as 140-160°C, 145±5°C; the vulcanization time depends on the vulcanization temperature, vulcanization system and vulcanization kinetics, and is usually 15-60 minutes, such as 20-40 minutes, 30±5 minutes.

[0084] The rubber composition of the present invention is used in rubber products, especially tires. Compared with the use of traditional p-phenylenediamine antioxidants such as IPPD, the use of formula A compound or the antioxidant composition of the present invention can significantly improve the wet heat aging resistance and ozone aging resistance of rubber products. Therefore, the present invention also provides a rubber product, the rubber product contains the rubber composition as described herein. The rubber product can be a tire, a rubber shoe, a sealing strip, a sound insulation board, a shockproof pad, etc. The rubber product is preferably a tire, such as a sidewall rubber, a tread rubber, etc.

[0085] 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: based on the mass of the diene elastomer contained in the rubber composition being 100 parts by mass, adding 1-5 parts by mass of the compound of formula A or the antioxidant composition of the present invention to the raw material of 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.

[0086] The present invention will be described below in the form 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 raw material compounds in the examples can all be purchased through commercial routes.

[0087] 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, sublimated sulfur and accelerator NS are all common raw materials for the rubber industry.

[0088] Preparation Example 1: Synthesis of Compounds of Formula I

[0089] (1) Synthesis of compound of formula III

[0090] In a 500mL four-necked flask, 181.5g (1.5mol) of 2,3-dimethylaniline and 100.1g (0.275mol) of a 25% aqueous solution of tetramethylammonium hydroxide (TMAOH) were added, stirred and heated to 40-50°C, and dehydrated by vacuum distillation to make TMAOH and 2,3-dimethylaniline form salts. During this process, the reaction liquid gradually changed from yellow to dark red; the temperature was gradually raised to 72°C. When the fraction was about 50% of the amount of 25% tetramethylammonium hydroxide added as catalyst, 31g (0.25mol) of nitrobenzene was added dropwise at 72°C under reduced pressure (-0.098MPa). The addition time was about 3h. After the addition was completed, the temperature was kept for 1h. LC monitoring was performed until the reaction of nitrobenzene was complete to obtain a condensation liquid.

[0091] The condensation liquid was transferred to a 500 mL stainless steel reactor, 50 g of deionized water and 40 g of catalyst skeleton nickel were added, hydrogen was replaced three times, the temperature was raised to 75° C., the pressure was raised to 1.5 MPa for reaction, and LC was monitored until the nitro and nitroso compounds were completely reduced. The reaction liquid 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 to obtain 45.7 g of compound III (yield of about 85%), and the content detected by GC was >96%.

[0092]

[0093] LC-MS (m / z): 212.30 (MH + ).

[0094] (2) Synthesis of Compounds of Formula I

[0095] 42.5g (0.2mol) of compound III, 60g (0.6mol) of 4-methyl-2-pentanone and 0.5g of Pt / C catalyst were put into a reactor, replaced with hydrogen 3 times, heated to 100°C, and pressurized to 1.5MPa for reaction. Detected by GC, when the content of compound III was <0.1%, the reaction was stopped. Cooled, filtered to remove the catalyst, and distilled at -0.1MPa and 180°C to remove the light components to obtain 57.6g of compound I (yield of about 97.2%), and the content detected by GC was >96.8%. Properties: reddish brown liquid.

[0096]

[0097] LC-MS (m / z): 296.46 (MH + ).

[0098] Preparation Example 2: Synthesis of Compound of Formula II

[0099] (1) Synthesis of compound of formula III

[0100] The synthesis of the compound of formula III is the same as that of Preparation Example 1.

[0101] (2) Synthesis of Compound II

[0102] 42.5g (0.2mol) of compound III, 100g (1.38mol) of 2-butanone and 0.6g of Pt / C catalyst were put into a reactor, replaced with hydrogen 3 times, heated to 80°C, and pressurized to 1.5MPa for reaction. Detected by GC, when the content of compound III was less than 0.1%, the reaction was stopped. Cooled, filtered to remove the catalyst, and distilled at -0.1MPa and 150°C to remove the light components to obtain 52.2g of compound II (yield of about 97.4%), and the content detected by GC was >95.8%. Properties: reddish brown solid.

[0103]

[0104] LC-MS (m / z): 268.40 (MH + ).

[0105] Preparation Example 3: Synthesis of Compound IV

[0106] (1) Synthesis of Compound V

[0107] In a 500mL four-necked flask, 181.5g (1.5mol) of 3,4-dimethylaniline and 100.1g (0.275mol) of a 25% aqueous solution of tetramethylammonium hydroxide (TMAOH) were added, stirred and heated to 40-50°C, and dehydrated by vacuum distillation to form salts of TMAOH and 2,3-dimethylaniline. During this process, the reaction liquid gradually changed from yellow to dark red; the temperature was gradually raised to 72°C. When the fraction was about 50% of the amount of 25% tetramethylammonium hydroxide added as catalyst, 31g (0.25mol) of nitrobenzene was added dropwise at 72°C under reduced pressure (-0.098MPa). The addition time was about 3h. After the addition was completed, the temperature was kept for 1h. LC monitoring was performed until the reaction of nitrobenzene was complete to obtain a condensation liquid.

[0108] The condensation liquid was transferred to a 500 mL stainless steel reactor, 50 g of deionized water and 40 g of catalyst skeleton nickel were added, hydrogen was replaced three times, the temperature was raised to 75° C., the pressure was raised to 1.5 MPa for reaction, and LC was monitored until the nitro and nitroso compounds were completely reduced. The reaction liquid 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 to obtain 43.5 g of the compound of formula V (yield of about 82%), and the content detected by GC was >95%.

[0109]

[0110] LC-MS (m / z): 212.30 (MH + ).

[0111] (2) Synthesis of Compound IV

[0112] 42.5g (0.2mol) of the compound of formula V, 162.4g (2.8mol) of acetone and 0.5g of Pt / C catalyst were put into a reactor, replaced with hydrogen 3 times, heated to 70°C, and pressurized to 1.5MPa for reaction. The reaction was detected by GC. When the content of the compound of formula V was <0.1%, the reaction was stopped. The temperature was lowered, the catalyst was removed by filtration, and the light components were removed by distillation at -0.1MPa and 180°C to obtain 49g of the compound of formula IV (yield of about 96.5%), and the content detected by GC was >96.0%. Properties: reddish brown solid.

[0113]

[0114] LC-MS (m / z): 254.38 (MH + ).

[0115] Preparation Example 4: Synthesis of Compound VI

[0116] (1) Synthesis of compound of formula VII

[0117] In a 500mL four-necked flask, add 223.8g (1.5mol) of 2,3-diethylaniline and 100.1g (0.275mol) of a 25% aqueous solution of tetramethylammonium hydroxide (TMAOH), stir and heat to 40-50°C, dehydrate by vacuum distillation to make TMAOH and 2,3-dimethylaniline form salts, during which the reaction liquid gradually changes from yellow to dark red; gradually heat to 72°C, when the fraction is about 50% of the amount of 25% tetramethylammonium hydroxide added as catalyst, distill at 72°C under reduced pressure (-0.098MPa) and drop 31g (0.25mol) of nitrobenzene, the dropping time is about 3h, and after the dropping is completed, keep warm for 1h, and monitor by LC until the reaction of nitrobenzene is complete to obtain a condensation liquid.

[0118] The condensation liquid was transferred to a 500 mL stainless steel reactor, 50 g of deionized water and 40 g of catalyst skeleton nickel were added, hydrogen was replaced three times, the temperature was raised to 75° C., the pressure was raised to 1.5 MPa for reaction, and LC was monitored until the nitro and nitroso compounds were completely reduced. The reaction liquid 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 to obtain 45.6 g of the compound of formula VII (yield of about 75.9%), and the content detected by GC was >94.5%.

[0119]

[0120] LC-MS (m / z): 240.35 (MH + ).

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

[0122] 43.2g (0.18mol) of compound VII, 155g (1.8mol) of 2-pentanone and 0.5g of Pt / C catalyst were put into a reactor, replaced with hydrogen for 3 times, heated to 100°C, and pressurized to 1.5MPa for reaction. Detected by GC, when the content of compound VII was less than 0.1%, the reaction was stopped. Cooled, filtered to remove the catalyst, and distilled at -0.1MPa and 180°C to remove the light components to obtain 53.2g of compound VI (yield of about 95.3%), the content of which was >96.8% by GC detection. Properties: reddish brown liquid.

[0123]

[0124] LC-MS (m / z): 310.49 (MH + ).

[0125] Examples 1-6 and Comparative Examples 1-3

[0126] 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:

[0127] (1) adding natural rubber and butadiene rubber into an internal mixer, and then adding carbon black, zinc oxide, stearic acid, aromatic oil and antioxidant (antiaging agent 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;

[0128] (2) After the first stage of the rubber is cooled, the first stage of the rubber is mixed on an open mixing mill, and 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 of the rubber;

[0129] (3) The second-stage rubber is vulcanized (145°C x 30 min) to obtain a vulcanized rubber.

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

[0131]

[0132] Test Example 1: High Temperature Water Immersion Test

[0133] The vulcanized rubbers of Examples 1-6 and Comparative Examples 1-3 were soaked in deionized water at 90°C for 8 hours, and the soaking liquid was evaporated and dried, and then the soaking precipitate was dissolved with acetone and analyzed by liquid chromatography to determine the content of the antioxidant therein. The results are shown in Table 2-4.

[0134] Table 2: Results of high temperature water immersion test on vulcanized rubber

[0135]

[0136] Table 3: Results of high temperature water immersion test on vulcanized rubber

[0137] Comparative Example 2 Example 6 Antioxidant mass in soaked material (mg / 100g glue) 0.705 0.100 Changes relative to Comparative Example 2 / -86％

[0138] Table 4: Results of high temperature water immersion test on vulcanized rubber

[0139] Comparative Example 3 Example 5 Antioxidant mass in soaked material (mg / 100g glue) 0.557 0.079 Changes relative to Comparative Example 2 / -86％

[0140] Test Example 2: Damp Heat Aging Test

[0141] According to GB / T 15905-1995 vulcanized rubber wet heat aging test method, the vulcanized rubber of Examples 1-6 and Comparative Examples 1-3 were subjected to high temperature and high humidity aging test, and the test conditions were aging box temperature 70°C, relative humidity 90%, and aging time 14 days. The test standard for elongation at break and tensile strength is: GB / T528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber. The results are shown in Tables 5-7.

[0142] In this article, tensile product = tensile strength × elongation at break

[0143] In this article, physical property retention rate = tensile product after aging / tensile product before aging

[0144] Table 5: Physical properties of vulcanized rubber before and after high temperature and high humidity aging

[0145]

[0146] Table 6: Physical properties of vulcanized rubber before and after high temperature and high humidity aging

[0147]

[0148] Table 7: Physical properties of vulcanized rubber before and after high temperature and high humidity aging

[0149]

[0150] Test Example 3: Thermal Oxygen Aging Test

[0151] According to GB / T 3512-2014 vulcanized rubber or thermoplastic rubber hot air accelerated aging and heat resistance test, the vulcanized rubber of Examples 1-6 and Comparative Examples 1-3 was subjected to thermal oxygen aging test, and the test conditions were: 100°C*48 hours. The test standard for elongation at break and tensile strength was: GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber. The results are shown in Tables 8-10.

[0152] Table 8: Physical properties of vulcanized rubber before and after hot air aging

[0153]

[0154] Table 9: Physical properties of vulcanized rubber before and after hot air aging

[0155]

[0156] Table 10: Physical properties of vulcanized rubber before and after hot air aging

[0157]

[0158] Test Example 4: Ozone Aging Test

[0159] 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:

[0160] Dynamic ozone aging: GB / T 13642-2015 Dynamic tensile test of vulcanized rubber or thermoplastic rubber for ozone cracking resistance;

[0161] Static ozone aging: GB / T 7762-2014 static tensile test of vulcanized rubber or thermoplastic rubber for ozone cracking resistance;

[0162] Crack grade evaluation: GB / T 11206-2009 Rubber aging test surface cracking method;

[0163] The specific test parameters are as follows: ozone volume concentration 50pphm, temperature (40±2)℃, humidity (50±5)%. Pre-stretch 20% during static testing, and observe the cracking of the sample regularly. Pre-stretch 10%, dynamic stretch 10%, frequency 0.5Hz during dynamic testing, and observe the cracking of the sample regularly. The results of dynamic ozone aging and static ozone aging are shown in Table 11 and Table 12, respectively. The meanings of 1c, 2c, 3c, and 4c in Table 11 and Table 12 can be found in standard GB / T 11206-2019.

[0164] Table 11: Dynamic ozone aging cracking grade results

[0165]

[0166]

[0167] Table 12: Static ozone aging cracking grade results

[0168]

[0169] The results in Table 2 show that after the rubber materials of Examples 1-4 were soaked in water at 90°C for 8 hours, the antioxidant content in the soaked precipitate was significantly lower than that in Comparative Example 1, and the antioxidant content in the soaked precipitate was less than 20% of that in Comparative Example 1. The results in Table 3 show that the antioxidant content in the soaked precipitate of the rubber materials of Example 6 was significantly lower than that in Comparative Example 2. The results in Table 4 show that the antioxidant content in the soaked precipitate of the rubber materials of Example 5 was significantly lower than that in Comparative Example 3. The above results show that the antioxidants in Examples 1-6 are not easy to migrate out of the rubber composition under high temperature and high humidity conditions.

[0170] 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.

[0171] However, as shown in Table 5, after aging for 14 days in a high temperature and 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 about 80%, while the physical property retention rate of the rubber material of Comparative Example 1 was only about 70%. As shown in Table 6, the physical property retention rate of the rubber material of Example 6 after high temperature and 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 and high humidity aging was significantly higher than that of Comparative Example 3. The above results show that the antioxidant in the rubber materials of Examples 1-6 is not easily dissolved and extracted by water under a high temperature and high humidity environment, and can still maintain a relatively high concentration in the rubber material, thereby playing a good protective role and showing excellent high temperature and high humidity aging resistance.

[0172] The results in Table 11 show that the crack density (b level) of the films of Examples 1-4 under dynamic ozone aging conditions is significantly lower than that of the film of Comparative Example 1 (c level); in terms of the growth rate of the crack width, the crack growth of the films of Examples 1-4 is significantly slower than that of Comparative Example 1. After 144 hours of ozone aging, the crack level of the film of Comparative Example 1 is Level 4, while the crack levels of the films of Examples 1-4 are all Level 3, with significant performance improvement. The crack level of Examples 1-4 reaches Level 3 after aging for at least 120 hours, while Comparative Example 1 only needs 96 hours, and the performance improvement reaches more than 25%.

[0173] 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, and the performance is significantly improved; after further extending the aging time to 144 hours, the crack grade of the films of Examples 1-4 is still maintained at Level 3, showing good durability.

[0174] 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 di-, tri- 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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