Rubber composition capable of protecting against metal ion aging and use thereof

Abstract

Disclosed are a compound of formula A that can be used as an anti-aging agent, a rubber composition containing the compound of formula A and a use of the rubber composition. The rubber composition of the present invention is used as an entire or partial rubber matrix of a tire, especially as a tire belt rubber. The anti-aging agent of the present invention can provide good rubber-steel wire adhesion performance, improve the thermal oxidative aging resistance of the rubber composition, and especially improve the mechanical properties and adhesion properties after aging in the presence of metal ions, prolonging the service life of tires.

Description

A rubber composition capable of protecting metal ions from aging and its use Technical Field

[0001] The invention belongs to the field of rubber, and particularly relates to a rubber composition capable of protecting metal ions from aging and application thereof. Background Art

[0002] Tires, as a key automotive component, play a crucial role in carrying the vehicle's weight and transmitting traction and braking forces. With the continuous development of the tire industry, radial tires have become widely used, and steel cord has become a very common reinforcement method. Therefore, the adhesion between rubber and steel cord has become crucial. Research has found that cobalt salts can effectively promote rubber-steel cord adhesion. It is generally believed that cobalt salts increase the activity of sulfur, accelerating the formation of copper sulfide at the bonding interface, which is beneficial for improving adhesion.

[0003] Although the addition of cobalt salts can improve the adhesion of rubber to steel cord, it has an adverse effect on the aging properties of the rubber compound.

[0004] Unsaturated rubber readily reacts with oxygen. Studies have shown that the oxidation of unsaturated rubber occurs through a free radical chain reaction mechanism and exhibits autocatalytic properties. Ions such as copper, manganese, and cobalt can catalyze the oxidation of rubber. Metal ion catalysis can dramatically increase the oxidation rate, accelerating thermal oxidation of rubber and significantly harming it.

[0005] Prior art methods often use antioxidants to inhibit the catalytic effect of metal ions, thereby improving the thermal-oxidative aging resistance of rubber products. 6PPD, a widely used antioxidant in the rubber industry, can inhibit ozone and thermal-oxidative aging of rubber products, as well as slow rubber degradation under static conditions. However, 6PPD is somewhat polluting, and using a single type of antioxidant in tire formulations can increase costs. It also fails to fully maintain the performance required under certain aging conditions during actual tire use and is prone to blooming and other issues.

[0006] Summary of the Invention

[0007] To address the problems of the prior art, the present invention provides a rubber composition with excellent protection against metal ion aging and its use. The rubber composition of the present invention serves as all or part of the rubber matrix of a tire, particularly as the rubber for the tire belt layer. The antioxidant of the present invention can provide good rubber-steel wire adhesion, improve the rubber composition's resistance to heat and oxygen aging and metal ion protection, and in particular, enhance the mechanical properties and adhesion performance after aging in the presence of metal ions, thereby extending the tire's service life.

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

[0009] In formula A, R1 is selected from C1-C8 alkyl, and R2 is selected from C1-C8 alkyl.

[0010] In one or more embodiments, in Formula A, R1 is methyl, and R2 is selected from C3-C6 alkyl.

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

[0012] Another aspect of the present invention provides a rubber composition, wherein the raw materials of the rubber composition include 100 parts by mass of a diene elastomer and 0.5-5 parts by mass of the compound of formula A as described in any embodiment herein.

[0013] In one or more embodiments, the raw materials of the rubber composition include 100 parts by mass of a diene elastomer, 0.2-5 parts by mass of a cobalt salt, and 0.5-5 parts by mass of a compound of formula A as described in any embodiment herein.

[0014] In one or more embodiments, the diene elastomer is natural rubber.

[0015] In one or more embodiments, the raw materials of the rubber composition further include 2-10 parts by mass of sulfur.

[0016] In one or more embodiments, the amount of the compound of formula A in the raw materials of the rubber composition is 1-3 parts by mass.

[0017] In one or more embodiments, the raw materials of the rubber composition further include 30-70 parts by mass of a reinforcing filler; the reinforcing filler preferably comprises carbon black and white carbon black.

[0018] In one or more embodiments, the raw materials of the rubber composition further include 2-15 parts by mass of an active agent; the active agent is preferably zinc oxide.

[0019] In one or more embodiments, the raw materials of the rubber composition further include 0.5-5 parts by mass of a tackifying resin.

[0020] In one or more embodiments, the raw materials of the rubber composition further include 1 to 10 parts by mass of a rubber binder.

[0021] In one or more embodiments, the raw materials of the rubber composition further include 0.5-5 parts by mass of an accelerator; the accelerator is preferably N,N′-dicyclohexyl-2-benzothiazolesulfenamide.

[0022] In one or more embodiments, the raw materials of the rubber composition further include 0.02-0.5 parts by mass of a rubber scorch retarder.

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

[0024] Another aspect of the present invention provides use of the compound of formula A described in any embodiment of the present invention in improving the mechanical properties and adhesion to steel wire of a rubber composition or rubber product after thermo-oxidative aging in the presence of metal ions.

[0025] In one or more embodiments, the use comprises adding 0.5 to 5 parts by mass of the compound of formula A to a raw material of a rubber composition containing 100 parts by mass of a diene elastomer and 0.2 to 5 parts by mass of a cobalt salt. DETAILED DESCRIPTION

[0026] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0027] 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.

[0028] Herein, “comprising,” “including,” “containing” and similar terms encompass the meanings of “consisting essentially of” and “consisting of,” for example, when “A comprises B and C” is disclosed herein, “A consists essentially of B and C” and “A consists of B and C” should be deemed to have been disclosed herein.

[0029] Throughout this document, all features, such as values, amounts, amounts, and concentrations, specified in numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible subranges and individual values ​​within those ranges (including integers and fractions).

[0030] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0031] Herein, when describing embodiments or examples, it should be understood that they are not intended to limit the present invention to these embodiments or examples. On the contrary, all alternatives, modifications and equivalents of the methods and materials described herein are encompassed within the scope defined by the claims.

[0032] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0033] The present invention has found that the compound of formula A can be used as a rubber antioxidant:

[0034] In formula A, R1 is selected from C1-C8 alkyl, and R2 is selected from C1-C8 alkyl.

[0035] As used herein, an alkyl group refers to a monovalent saturated group consisting of hydrogen atoms and carbon atoms. An alkyl group can be a straight chain alkyl group or a branched chain alkyl group. An alkyl group can contain 1 to 8 carbon atoms (C1-C8 alkyl). Exemplary alkyl groups include, but are not limited to, methyl, ethyl, isopropyl, n-butyl, isobutyl, 1-methylpropyl, 1,3-dimethylbutyl, 1,4-dimethylpentyl, octyl, and the like.

[0036] In some embodiments, in the compound of formula A, R1 is selected from C1-C4 alkyl, such as C1-C2 alkyl. In some embodiments, in the compound of formula A, R1 is methyl.

[0037] In some embodiments, in the compound of formula A, R2 is selected from C3-C6 alkyl. In some embodiments, in the compound of formula A, R2 is selected from isopropyl, 1-methylpropyl and 1,3-dimethylbutyl.

[0038] In some embodiments, in the compound of formula A, R1 is selected from C1-C4 alkyl, such as C1-C2 alkyl, and R2 is selected from C1-C8 alkyl, such as C3-C6 alkyl.

[0039] In some embodiments, in the compound of formula A, R1 is methyl, and R2 is selected from C3-C6 alkyl.

[0040] In some embodiments, the compound of formula A is a compound of formula I, a compound of formula II, or a compound of formula III as shown below:

[0041] The present invention finds that adding a compound of formula A (e.g., a compound of formula I, a compound of formula II, or a compound of formula III) to a rubber composition (e.g., a tire rubber compound, especially a tire belt layer rubber compound) can impart excellent heat-oxidative aging resistance and good steel wire adhesion to the rubber composition, especially the heat-oxidative aging resistance in the presence of metal ions (e.g., cobalt salts). The addition can significantly improve the mechanical properties of the rubber composition after heat-oxidative aging in the presence of metal ions and the adhesion strength to the steel wire.

[0042] The present invention provides a method for preparing a compound of formula A, comprising the following steps:

[0043] (1) subjecting aniline and a compound of formula B to a condensation reaction under the action of a first catalyst to obtain a condensate comprising a compound of formula C and / or a compound of formula C′, and then subjecting the condensate to a reduction reaction under the action of H2 and a second catalyst to obtain a compound of formula D;

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

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

[0046] The first catalyst used in step (1) can be one or more selected from alkali metal hydroxides, alkali metal alkoxides, quaternary ammonium bases, and combinations of alkali metal hydroxides and tetraalkylammonium halides. Suitable alkali metal hydroxides for use in the present invention include sodium hydroxide, potassium hydroxide, lithium hydroxide, and the like. Suitable alkali metal alkoxides for use in the present invention include sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, potassium tert-butoxide, sodium tert-amyl alcoholate, potassium tert-amyl alcoholate, and the like. Quaternary ammonium bases are a class of compounds having the general formula (R a )4NOH compound, wherein R a In some embodiments, each R in the quaternary ammonium base is a is an alkyl group, for example, each R a Each of the quaternary ammonium groups may be independently selected from methyl, ethyl, propyl and butyl. Examples of quaternary ammonium bases suitable for use in the present invention include tetraalkylammonium hydroxides, such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, etc. The general formula of the tetraalkylammonium halide is (R b )4NX, where R bare four identical or different aliphatic groups (such as alkyl groups) or aromatic groups, such as methyl, ethyl, propyl, butyl, etc., and X is a halogen atom, such as fluorine, chlorine, bromine, or iodine. The first catalyst can also be a combination of an alkali metal hydroxide and a tetraalkylammonium halide. Examples of combinations of alkali metal hydroxides and tetraalkylammonium halides include sodium hydroxide and tetrabutylammonium bromide, etc. In some embodiments, the first catalyst is a quaternary ammonium base, such as tetraalkylammonium hydroxide. The molar ratio of the first catalyst to aniline can be 0.1:1 to 2:1, preferably 0.1:1 to 0.5:1, such as 0.2:1, 0.3:1, or 0.4:1. In step (1), aniline and the first catalyst can be first salified, and then the compound of formula B is added dropwise to carry out a condensation reaction.

[0047] In step (1), the condensation product obtained by the condensation reaction of aniline and the compound of formula B under the action of the first catalyst may be one or both of the compound of formula C and the compound of formula C′, and may also contain an azobenzene compound:

[0048] In step (1), the molar ratio of aniline to the compound of formula B can be 2:1 to 15:1, preferably 4:1 to 10:1, more preferably 5:1 to 8:1, for example 6:1, 7:1.

[0049] In step (1), the condensation reaction can be carried out at 40-90° C., preferably 65-85° C., for example, the reaction temperature can be 60° C., 70° C., 75° C., or 80° C. The condensation reaction needs to be carried out under vacuum conditions, with a vacuum degree range of -0.09 to -0.99 MPa.

[0050] The second catalyst used in step (1) can be a porous metal catalyst or a supported metal catalyst. Porous metal catalysts are also called sponge metal catalysts. Porous metal catalysts suitable for the present invention include Raney nickel (also known as skeleton nickel), Raney cobalt, Raney copper, etc. Supported metal catalysts include a metal as a catalytic active center and a carrier for supporting the metal. The metal in the supported metal catalyst suitable for the present invention can be nickel, cobalt, copper, platinum, palladium, ruthenium, rhodium, etc., and the carrier can be carbon, alumina, silica gel, molecular sieve, etc. The carbon as a carrier can be activated carbon. In some embodiments, the second catalyst is a porous metal catalyst, such as Raney nickel. 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.

[0051] In step (1), the condensate generated by the condensation reaction is subjected to a hydrogenation reduction reaction in the presence of a second catalyst to produce a compound of formula D. In step (1), the reduction reaction can be carried out at 40 to 120° C., preferably 60 to 90° C., for example, the reaction temperature can be 70° C., 75° C., or 80° C. The hydrogen pressure during the reduction reaction can be 0.5 to 5 MPa, preferably 0.5 to 2.5 MPa, for example, 1 MPa, 1.5 MPa, 2 MPa, or 2.5 MPa.

[0052] In step (1), aniline 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 liquid is filtered to recover the second catalyst, the oil-water phase is separated to recover the first catalyst, and the organic phase is distilled to remove light components to obtain the compound of formula D.

[0053] The third catalyst used in step (2) can be the aforementioned supported metal catalyst, such as Pt / C. The molar ratio of the metal in the third catalyst to the compound of formula D can be 0.0001:1 to 0.2:1.

[0054] In step (2), the compound of formula D and the compound of formula E are subjected to a hydrogenation reduction alkylation reaction under the action of a third catalyst to produce the compound of formula A. After the reaction, the carbonyl carbon atom in the compound of formula E is connected to the amino nitrogen atom in the compound of formula D. Therefore, a suitable compound of formula E can be selected for reaction according to the R2 group contained in the compound of formula A to be prepared. The molar ratio of the compound of formula E to the compound of formula D can be 1:1 to 15:1, for example, 2:1, 3:1, 5:1, 8:1, 10:1, 11:1, 14:1. The reaction temperature of step (2) can be 40 to 150°C, preferably 50 to 120°C, for example, 50°C, 70°C, 80°C, 100°C, 120°C. The hydrogen pressure in step (2) can be 0.5 to 5 MPa, preferably 0.5 to 2.5 MPa, for example, 1 MPa, 1.2 MPa, 1.5 MPa, 1.8 MPa, 2 MPa, 2.5 MPa.

[0055] In step (2), the compound of formula E, which is a reaction raw material, can be used as a solvent. After the reaction in step (2) is completed, the reaction solution is filtered to recover the third catalyst, and the light components are removed by vacuum distillation to obtain the compound of formula A.

[0056] 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.

[0057] The present invention also provides a rubber composition comprising a compound of formula A (eg, a compound of formula I and / or a compound of formula II).

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

[0059] The raw materials of the rubber composition of the present invention include a diene elastomer and a compound of formula A as an antioxidant. The compound of formula A may be used in an amount of 0.5 to 5 parts by mass per 100 parts by mass of the diene elastomer. Unless otherwise specified herein, the weight percentages of other components in the rubber composition raw materials are calculated based on 100 parts by mass of the diene elastomer.

[0060] As used herein, a diene elastomer refers to an elastomer whose monomers include a diene (e.g., butadiene or isoprene). Suitable diene elastomers for use in the present invention may be any of various diene elastomers known in the art, including, but not limited to, one or more selected from natural rubber (NR), butadiene rubber (BR), isoprene rubber, styrene-butadiene rubber (SBR), chloroprene rubber (CR), nitrile rubber (NBR), isoprene / butadiene copolymers, isoprene / styrene copolymers, and isoprene / butadiene / styrene copolymers. In some preferred embodiments, the diene elastomer comprises or consists of natural rubber.

[0061] The antioxidant contained in the rubber composition of the present invention includes formula A compound (such as formula I compound and / or formula II compound).In some embodiments, the rubber composition of the present invention does not contain other antioxidants except formula A compound.In the raw material of the rubber composition of the present invention, the consumption of formula A compound can be 0.5-5 mass parts, preferably 1-3 mass parts, such as 1.2 mass parts, 1.5 mass parts, 1.8 mass parts, 2 mass parts, 2.2 mass parts, 2.5 mass parts.In some embodiments, the raw material of the rubber composition of the present invention includes formula I compound and / or formula II compound, preferably includes formula I compound.In some embodiments, the antioxidant in the rubber composition of the present invention is formula I compound, formula II compound or a combination of the two, preferably formula I compound. Among the raw materials of the rubber composition of the present invention, the amount of the compound of formula I when the compound of formula I is used alone, the amount of the compound of formula II when the compound of formula II is used alone, the amount of the compound of formula III when the compound of formula III is used alone, or the total amount of two or three of the compounds of formula I, formula II and formula III when used simultaneously can be 0.5-5 parts by mass, preferably 1-3 parts by mass, for example, 1.2 parts by mass, 1.5 parts by mass, 1.8 parts by mass, 2 parts by mass, 2.2 parts by mass, and 2.5 parts by mass.

[0062] The raw materials of the rubber composition of the present invention may include reinforcing fillers. In the raw materials of the rubber composition of the present invention, the amount of reinforcing fillers can be 30-70 parts by mass, for example, 40 parts by mass, 45 parts by mass, 50 parts by mass, 55 parts by mass, and 60 parts by mass. The reinforcing fillers suitable for the present invention can be reinforcing fillers conventionally used in rubber compositions, 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 talc. In some embodiments, the reinforcing filler comprises carbon black. Examples of carbon black include carbon black N330. In the rubber composition of the present invention, the amount of carbon black can be 25-55 parts by mass, for example, 30 parts by mass, 35 parts by mass, 40 parts by mass, 43 parts by mass, 45 parts by mass, and 50 parts by mass. In some embodiments, the reinforcing filler comprises white carbon black. In the rubber composition of the present invention, the amount of white carbon black can be 5-20 parts by mass, for example, 8 parts by mass, 10 parts by mass, 12 parts by mass, and 15 parts by mass. In some preferred embodiments, the reinforcing filler comprises carbon black and white carbon black, or the reinforcing filler consists of carbon black and white carbon black.

[0063] The raw materials of the rubber composition of the present invention include a crosslinking agent, such as sulfur. The sulfur is preferably insoluble sulfur. The amount of sulfur in the raw materials of the rubber composition of the present invention can be 2-10 parts by mass, for example, 3 parts by mass, 4 parts by mass, 5 parts by mass, 6 parts by mass, 7 parts by mass, 8 parts by mass, or 9 parts by mass.

[0064] The raw materials of the rubber composition of the present invention may also include other ingredients that can be used in rubber compositions, including but not limited to one or more selected from softeners, protective waxes, activators, cobalt salts, tackifying resins, rubber adhesives, accelerators, rubber scorch retardants, etc.

[0065] Softening agent can be used for improving the processing properties of rubber combination.Softening agent can include petroleum softening agent, such as naphthenic oil, aromatic oil, process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, vaseline etc., and can also include fatty oil softening agent, 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 present invention, softening agent is optional to add. When the raw material of rubber combination of the present invention includes softening agent, the consumption of softening agent can be 1-10 mass parts, is preferably 3-9 mass parts, such as 4 mass parts, 5 mass parts, 6 mass parts, 7 mass parts, 8 mass parts.

[0066] The protective wax can migrate from the interior of the rubber to the surface to form a wax film, thereby isolating the rubber surface from the external environment. In the present invention, 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, for example, 1.5 parts by mass, 2 parts by mass, 3 parts by mass, or 4 parts by mass.

[0067] The activating agent can play the role of accelerating the vulcanization speed, improving the thermal conductivity, wear resistance, tear resistance of the rubber. The raw materials of the rubber composition of the present invention preferably include an activating agent. Examples of activating agents include ZnO. In the raw materials of the rubber composition of the present invention, the amount of the activating agent can be 2-15 mass parts, such as 5 mass parts, 6 mass parts, 7 mass parts, 8 mass parts, 9 mass parts, 10 mass parts, 12 mass parts. In some preferred embodiments, the activating agent includes ZnO, or the activating agent is ZnO. In some preferred embodiments, in the raw materials of the rubber composition of the present invention, the amount of ZnO is 2-15 mass parts, such as 5 mass parts, 6 mass parts, 7 mass parts, 8 mass parts, 9 mass parts, 10 mass parts, 12 mass parts.

[0068] Cobalt salts can effectively promote rubber-steel cord adhesion. When used as a tire belt compound, the raw materials of the rubber composition of the present invention preferably include cobalt salts. Cobalt salts that can be used in the present invention include, but are not limited to, cobalt boroacylate, cobalt neodecanoate, and the like. The amount of cobalt salt used in the raw materials of the rubber composition of the present invention can be 0.2-5 parts by mass, for example, 0.5 parts by mass, 0.8 parts by mass, 1 part by mass, 1.2 parts by mass, 1.5 parts by mass, 2 parts by mass, or 3 parts by mass.

[0069] Tackifying resin is used to enhance the adhesion between rubber and steel cord. When used as a tire belt compound, the raw materials of the rubber composition of the present invention preferably include tackifying resin. Available tackifying resins include resorcinol donors, such as resorcinol-formaldehyde resin. In the raw materials of the rubber composition of the present invention, the amount of tackifying resin can be 0.5-5 parts by mass, such as 1 part by mass, 1.5 parts by mass, 2 parts by mass, 2.5 parts by mass, 3 parts by mass, or 4 parts by mass. In some embodiments, the tackifying resin includes resorcinol-formaldehyde resin, or the tackifying resin is resorcinol-formaldehyde resin. Examples of available tackifying resins include resorcinol-formaldehyde resin SL3022.

[0070] The rubber adhesive can be an adhesive containing a methylene donor (such as hexamethoxymethyl melamine), which is used in conjunction with a tackifying resin to fully bond the rubber to skeleton materials such as steel wire. When used as a tire band rubber compound, the raw materials of the rubber composition of the present invention preferably include a rubber adhesive. Available rubber adhesives include rubber adhesives whose active ingredient is hexamethoxymethyl melamine (abbreviated as HMMM), such as rubber adhesive RA. Rubber adhesive RA is composed of HMMM and an inorganic carrier. The example of rubber adhesive RA includes rubber adhesive RA-65. The mass fraction of HMMM in rubber adhesive RA-65 is 65%. In the raw materials of the rubber composition of the present invention, the amount of rubber adhesive can be 1-10 parts by mass, such as 2 parts by mass, 3 parts by mass, 4 parts by mass, 5 parts by mass, 6 parts by mass, 7 parts by mass, and 8 parts by mass. In some embodiments, the rubber adhesive includes rubber adhesive RA, or the rubber adhesive is rubber adhesive RA. In the raw materials of the rubber composition of the present invention, the amount of the methylene donor (such as HMMM) can be 1-10 parts by mass, for example, 2 parts by mass, 3 parts by mass, 4 parts by mass, 5 parts by mass, 6 parts by mass, 7 parts by mass, or 8 parts by mass.

[0071] Rubber anti-scorch agent is used to prevent the rubber compound from producing early vulcanization phenomenon during processing, and can be one or more selected from nitroso compounds (such as N-nitrosodiphenylamine), organic acids (such as benzoic acid, phthalic anhydride) and thioimides (such as N-cyclohexylthiophthalimide) etc. The example of rubber anti-scorch agent includes rubber anti-scorch agent CTP (N-cyclohexylthiophthalimide). The raw material of the rubber composition of the present invention preferably includes rubber anti-scorch agent. In the raw material of the rubber composition of the present invention, the amount of rubber anti-scorch agent can be 0.02-0.5 mass parts, such as 0.05 mass parts, 0.1 mass parts, 0.2 mass parts, 0.3 mass parts, 0.4 mass parts. In some embodiments, rubber anti-scorch agent includes rubber anti-scorch agent CTP, or rubber anti-scorch agent is rubber anti-scorch agent CTP.

[0072] The accelerator is usually a vulcanization accelerator, which can be selected from one or more of sulfonamide vulcanization accelerators, thiazole vulcanization accelerators, thiuram vulcanization accelerators, thiourea vulcanization accelerators, guanidine vulcanization accelerators, dithiocarbamate vulcanization accelerators, aldehydeamine vulcanization accelerators, aldehyde-amine vulcanization accelerators, imidazoline vulcanization accelerators and xanthate vulcanization accelerators. In the raw materials of the rubber composition of the present invention, the amount of the accelerator can be 0.5-5 parts by mass, for example, 1 part by mass, 1.4 parts by mass, 1.5 parts by mass, 2 parts by mass, or 3 parts by mass. In some preferred embodiments, the accelerator is accelerator DZ (N, N'-dicyclohexyl-2-benzothiazolesulfenamide).

[0073] In addition, when necessary, the rubber composition may further include plasticizers such as DMP (dimethyl phthalate), DEP (diethyl phthalate), DBP (dibutyl phthalate), DHP (diheptyl phthalate), DOP (dioctyl phthalate), DINP (diisononyl phthalate), DIDP (diisodecyl phthalate), BBP (butyl benzyl phthalate), DWP (dilauryl phthalate), and DCHP (dicyclohexyl phthalate). The amount of the plasticizer used may be a conventional amount in the art.

[0074] When the rubber composition is used as a tire band compound, the rubber composition of the present invention preferably includes a bonding system consisting of a resorcinol donor (e.g., resorcinol-formaldehyde resin), a methylene donor (e.g., HMMM), and silica, which can effectively improve rubber-to-metal adhesion. The amounts of the resorcinol donor, methylene donor, and silica can be as described in any embodiment herein.

[0075] In some preferred embodiments, the raw materials of the rubber composition of the present invention include: 100 parts by mass of a diene elastomer, 2-10 parts by mass of sulfur, 0.5-5 parts by mass of a compound of formula A, 25-55 parts by mass of carbon black, 5-20 parts by mass of white carbon black, 2-15 parts by mass of ZnO, 0.2-5 parts by mass of a cobalt salt, 0.5-5 parts by mass of a tackifying resin (e.g., resorcinol-formaldehyde resin), 1-10 parts by mass of a rubber adhesive (e.g., rubber adhesive RA), 0.02-0.5 parts by mass of a rubber retarder (e.g., rubber retarder CTP), and 0.5-5 parts by mass of an accelerator (e.g., accelerator DZ), or consist of the above ingredients.

[0076] The unvulcanized rubber of the present invention can be prepared by conventional rubber mixing methods, for example, by a two-stage mixing method: a first stage of thermomechanical mixing (e.g., an internal mixer) to mix the rubber composition raw materials except the crosslinking agent, rubber adhesive and accelerator, and knead the entire mixture until it reaches a maximum temperature between 110°C and 190°C to obtain a first stage rubber; a second stage of thermomechanical mixing (e.g., an open mixer) to mix the first stage rubber with the crosslinking agent, rubber adhesive and accelerator to obtain a second stage rubber, i.e., the unvulcanized rubber.

[0077] Vulcanized rubber can be obtained by vulcanizing (curing) the unvulcanized rubber. The vulcanization temperature is generally 130°C-200°C, for example, 140-160°C, 150±5°C. The vulcanization time depends on the vulcanization temperature, the vulcanization system, and the vulcanization kinetics, and is generally 15-60 minutes, for example, 20-40 minutes, 30±5 minutes.

[0078] Compared with the rubber composition using antioxidant 6PPD, the rubber composition using formula A compound (such as one or more of formula I compound, formula II compound and formula III compound) as antioxidant is used for rubber products, such as tires, especially tire belts, and can make rubber products have better mechanical properties after thermal oxidative aging in the presence of metal ions (such as cobalt ions) and adhesion between rubber and steel wire. Therefore, the present invention also provides a kind of rubber product, and the rubber product contains rubber composition as herein described. The rubber product can be tire, rubber shoes, sealing strips, sound insulation boards, anti-vibration pads, etc. The rubber product is preferably a tire, such as tire belts, etc.

[0079] The present invention also provides the use of a compound of formula A (e.g., one or more of a compound of formula I, a compound of formula II, and a compound of formula III) in improving the mechanical properties of a rubber composition or rubber product after heat-oxidative aging in the presence of metal ions (e.g., cobalt ions) and the adhesion properties to steel wire, and a method for improving the mechanical properties of a rubber composition or rubber product after heat-oxidative aging in the presence of metal ions (e.g., cobalt ions) and the adhesion properties to steel wire. Preferably, the use or method of the present invention includes: adding a compound of formula A (e.g., one or more of a compound of formula I, a compound of formula II, and a compound of formula III) to the raw materials of the rubber composition. In the use or method of the present invention, the amount of the compound of formula A (e.g., one or more of a compound of formula I, a compound of formula II, and a compound of formula III) and the raw material composition of the rubber composition are preferably as described in any embodiment herein.

[0080] The present invention will be described below by way of specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the present invention. The methods, reagents, and materials used in the examples are, unless otherwise stated, conventional methods, reagents, and materials in the art. The starting compounds in the examples can all be purchased from commercial sources.

[0081] The sources and specifications of the raw materials used in the examples are as follows:

[0082] Natural rubber (NR): Xishuangbanna Sinochem Rubber Co., Ltd., SCR5;

[0083] Carbon black: Shanghai Cabot Carbon Black Co., Ltd., N330;

[0084] Silica: Shanghai Kaiyin Chemical Co., Ltd., VN3;

[0085] Zinc oxide: Yonghua Chemical Technology (Jiangsu) Co., Ltd.

[0086] Cobalt boroacylate: Zhejiang Jinmao Rubber Additives Co., Ltd., in compliance with industry standard HG / T 4072-2008;

[0087] Antioxidant 6PPD: Senao Chemical Technology Co., Ltd.

[0088] Resorcinol-formaldehyde resin: SI Group Chemical Co., Ltd., SL3022;

[0089] Rubber adhesive RA-65: Shandong Ruiqi Chemical Co., Ltd.

[0090] Rubber anti-scorch agent CTP: Shandong Yanggu Huatai Chemical Co., Ltd.

[0091] Insoluble sulfur: Sanao Chemical Technology Co., Ltd., HD OT20;

[0092] Accelerator DZ: Weilin New Materials Technology Co., Ltd.

[0093] Preparation Example 1

[0094] (1) Synthesis of compound of formula IV

[0095] In a 500 mL four-necked flask, 139.7 g (1.5 mol) of aniline and 91 g (0.25 mol) of a 25% aqueous solution of tetramethylammonium hydroxide (TMAOH) were added. The mixture was stirred and heated to 40-55° C., and dehydrated by vacuum distillation to form a salt between TMAOH and aniline. During this process, the reaction solution gradually changed from yellow to deep red. The temperature was gradually raised to 72° C. When the fraction reached approximately 46 mL, 34.3 g (0.25 mol) of 3-methylnitrobenzene was added dropwise by vacuum distillation at 72° C. (−0.098 MPa) for approximately 3 h. After the addition was complete, the mixture was incubated for 1 h. LC monitoring was performed to determine the complete reaction of 3-methylnitrobenzene to obtain a condensation solution.

[0096] The condensation solution was transferred to a 500 mL stainless steel reactor, and 50 g of deionized water and 40 g of skeletal nickel catalyst were added. The reaction was then hydrogenated three times, heated to 75°C, and hydrogen was introduced to 1.5 MPa for a hydrogenation reduction reaction. LC monitoring was performed until the nitro and nitroso compounds were completely reduced. The reaction was then filtered and phase separated. The organic phase was washed with water and distilled under reduced pressure (-0.1 MPa, 160°C) to remove aniline and light by-products. Finally, 42.6 g of the reduction product (Compound IV) was distilled off and solidified on cooling to form a yellow solid. The yield was approximately 86%, and the content was >99% as determined by GC.

[0097] LC-MS (m / z): 198.22 (M-H+).

[0098] 1H NMR (400MHz, CDCl3) δ7.22-7.15 (m, 2H), 7.03 (d, J=8.3Hz, 1H), 6.79-6.74 (m, 1H), 6.68 (dt, J=8.8, 1 .7Hz, 2H), 6.61 (d, J=2.6Hz, 1H), 6.54 (dd, J=8.3, 2.7Hz, 1H), 5.15 (s, 1H), 3.56 (s, 2H), 2.17 (s, 3H).

[0099] (2) Synthesis of compound of formula I

[0100] 46 g (0.23 mol) of the compound of formula IV, 70 g (0.70 mol) of 4-methyl-2-pentanone, and 0.8 g of Pt / C catalyst were placed in a reactor. The atmosphere was replaced with hydrogen three times, and the temperature was raised to 80°C. Hydrogen was introduced to 1.8 MPa and the reaction was stopped when the content of the compound of formula IV was less than 0.1% as determined by GC. The reaction was then cooled, the catalyst was removed by filtration, and light components were removed by distillation at -0.1 MPa and 180°C to obtain 60.4 g of the compound of formula I (yield: approximately 93%). The content was >95.8% as determined by GC. The mixture solidified after cooling to a red liquid.

[0101] Molecular formula: C 19 H 26 N2

[0102] LC-MS (m / z): 282.40 (M-H+).

[0103] Preparation Example 2

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

[0105] The synthesis of the compound of formula IV is the same as that in Preparation Example 1.

[0106] (2) Synthesis of compound of formula II

[0107] 40 g (0.2 mol) of the compound of formula IV, 151.4 g (2.1 mol) of 2-butanone, and 0.5 g of Pt / C catalyst were placed in a reactor. The atmosphere was replaced with hydrogen three times, and the temperature was raised to 80°C. Hydrogen was introduced to 1.5 MPa for reaction. GC analysis was performed. The reaction was stopped when the content of the compound of formula IV was less than 0.1%. The temperature was lowered, the catalyst was removed by filtration, and light components were removed by distillation at -0.1 MPa and 180°C to obtain 50.9 g of the compound of formula II (yield: approximately 99%). The content was >99% as determined by GC analysis. The product solidified after cooling to a light red solid.

[0108] Molecular formula: C 17 H 22 N2

[0109] LC-MS (m / z): 254.35 (M-H+).

[0110] 1 H NMR (400MHz, CDCl3) δ7.26-7.18 (m, 2H), 7.01 (d, J=8.4Hz, 1H), 6.73-6.68 (m, 1H), 6.65 (m, 2H), 6.47 (d, J=2.7Hz, 1H), 6.43 (dd, J=8.4, 2 .7Hz, 1H), 4.98 (s, 1H), 3.68-3.42 (m, 1H), 3.30 (br.s, 1H), 2.20 (s, 3H), 1.52-1.45 (m, 2H), 1.21 (d, J=6.3Hz, 3H), 0.97 (t, J=7.4Hz, 3H).

[0111] Preparation Example 3

[0112] (1) Synthesis of compound of formula IV

[0113] The synthesis of the compound of formula IV is the same as that in Preparation Example 1.

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

[0115] 40 g (0.2 mol) of compound IV, 162.4 g (2.8 mol) of acetone, and 0.5 g of Pt / C catalyst were placed in a reactor. The atmosphere was replaced with hydrogen three times, and the temperature was raised to 70°C. Hydrogen was introduced to 1.5 MPa and the reaction was stopped when the content of compound IV was less than 0.1%. The temperature was lowered, the catalyst was removed by filtration, and light components were removed by distillation at -0.1 MPa and 180°C to obtain 48.3 g of compound III (yield approximately 99.4%). The content was >98% as determined by GC. The product solidified after cooling to a light pink solid.

[0116] Molecular formula: C 16 H 20 N2

[0117] LC-MS (m / z): 240.35 (M-H+).

[0118] 1H NMR (400MHz, CDCl3) δ7.20-7.11 (m, 2H), 7.03 (d, J=8.4Hz, 1H), 6.77-6.70 (m, 1H), 6.65 (dt, J=8.8, 1. 7Hz, 2H), 6.50 (d, J=2.7Hz, 1H), 6.44 (dd, J=8.4, 2.7Hz, 1H), 5.13 (s, 1H), 3.71-3.43 (m, 1H), 3.34 (br s, 1H), 2.17 (s, 3H), 1.23 (d, J=6.3Hz, 6H).

[0119] Examples 1-6 and Comparative Examples 1-4

[0120] According to the formulation shown in Table 1, the rubber compositions of Examples 1-6 and Comparative Examples 1-4 were prepared using the following process:

[0121] (1) The mixing was carried out in an internal mixer with an initial temperature of 70°C and a rotor speed of 60 r / min. -1 , adding natural rubber into an internal mixer, and then adding carbon black N330, white carbon black, zinc oxide, cobalt boroacylate, antioxidant (compound of formula I, compound of formula II or antioxidant 6PPD), resorcinol-formaldehyde resin SL3022 and rubber scorch retarder CTP, kneading until the rubber temperature reaches 150°C and the rubber is discharged to obtain a first stage rubber;

[0122] (2) The second stage mixing is carried out on an open mill. The first stage rubber, rubber adhesive RA-65, insoluble sulfur and accelerator DZ are added to the open mill, and the mixture is thinned 5 times and then unrolled to obtain the second stage rubber;

[0123] (3) The second-stage rubber is vulcanized at 151°C for 30 minutes to obtain a vulcanized rubber.

[0124] Table 1: Formulations of the rubber compositions of Examples 1-6 and Comparative Examples 1-4 (Unit: parts by mass)

[0125] Test Example 1: Mechanical properties before and after thermal oxidative aging

[0126] The tensile strength and elongation at break of the vulcanized rubber before thermal oxidative aging, as well as the retention of tensile strength and elongation at break after thermal oxidative aging, were tested according to the following standards:

[0127] Tensile strength and elongation at break: GB / T 528-2009 Vulcanized rubber or thermoplastic rubber - Determination of tensile stress-strain properties;

[0128] Thermal oxidative aging test: GB / T 3512-2014 vulcanized rubber or thermoplastic rubber hot air accelerated aging and heat resistance test, aging conditions are 100℃×48h.

[0129] Tensile strength retention after aging = tensile strength after aging / tensile strength before aging × 100%

[0130] Retention rate of elongation at break after aging = elongation at break after aging / elongation at break before aging × 100%

[0131] The mechanical properties of the rubber compositions of Examples 1-6 and Comparative Examples 1-4 before and after aging are shown in Table 2.

[0132] Table 2: Mechanical properties of the rubber compositions of Examples 1-6 and Comparative Examples 1-4 before and after aging

[0133] As can be seen from Table 2, the mechanical properties of the rubber compositions of Examples 1-2, which added the compound of Formula I, the rubber compositions of Examples 3-4, which added the compound of Formula II, and the rubber compositions of Examples 5-6, which added the compound of Formula III, before aging were similar to those of the rubber composition of Comparative Examples 3-4, which added the antioxidant 6PPD. The post-aging retention rates of the rubber composition of Comparative Example 1 were lower than those of Comparative Example 2, indicating that the addition of cobalt salts had an adverse effect on thermal oxidative aging performance. Compared to the rubber composition of Comparative Example 1, the post-aging retention rates of the rubber compositions of Examples 1-2, which added the compound of Formula I, the rubber compositions of Examples 3-4, which added the compound of Formula II, and the rubber compositions of Examples 5-6, which added the compound of Formula III, were significantly improved, demonstrating that the compounds of Formula I, Formula II, and Formula III can impart excellent thermal oxidative aging resistance and metal ion protection to the rubber compositions. In particular, under the same amount of antioxidant, the rubber compositions of Examples 1-2 to which the compound of Formula I is added, the rubber compositions of Examples 3-4 to which the compound of Formula II is added, and the rubber compositions of Examples 5-6 to which the compound of Formula III is added have higher retention rates of tensile strength and elongation at break after thermal oxidative aging in the presence of metal ions than the rubber compositions of Comparative Examples 3-4 to which the antioxidant 6PPD is added, indicating that the compounds of Formula I, Formula II and Formula III have better effects on improving the thermal oxidative aging resistance and metal ion protection properties of the rubber compositions than the antioxidant 6PPD.

[0134] Test Example 2: Steel Wire Adhesion Performance

[0135] The bonding strength between the vulcanized rubbers of Examples 1-6 and Comparative Examples 1-4 and the steel cords before and after thermal oxidative aging was tested according to the following standards. The results are shown in Table 3:

[0136] Adhesion strength: GB / T 16586-1996 Determination of adhesion strength between vulcanized rubber and steel cord;

[0137] Thermal oxidative aging test: GB / T 3512-2014 vulcanized rubber or thermoplastic rubber hot air accelerated aging and heat resistance test, aging conditions are 100℃×96h.

[0138] Adhesion strength retention rate after aging = Adhesion strength after aging / Adhesion strength before aging × 100%

[0139] Table 3: Adhesion strength of the rubber compositions of Examples 1-6 and Comparative Examples 1-4 to the steel cord before and after aging

[0140] As shown in Table 3, compared with the vulcanized rubber of Comparative Example 2 without adding cobalt salt, the vulcanized rubber bonding strength of Comparative Example 1 with added cobalt salt is higher, showing that the addition of cobalt salt improves rubber-steel wire bonding performance. The bonding strength of the vulcanized rubber of Example 1-2 with added Formula I compound and the vulcanized rubber of Example 3-4 with added Formula II compound is higher than the vulcanized rubber of Comparative Example 1 without adding antioxidant and the vulcanized rubber of Comparative Example 3-4 with added antioxidant 6PPD, showing that Formula I compound and Formula II compound can improve the bonding performance of rubber composition and steel wire. The bonding strength retention rate of the vulcanized rubber of Example 1-2 with added Formula I compound, the vulcanized rubber of Example 3-4 with added Formula II compound and the vulcanized rubber of Example 5-6 with added Formula III compound after hot-oxidative aging is higher than the vulcanized rubber of Comparative Example 3-4 with added antioxidant 6PPD, showing that Formula I compound, Formula II compound and Formula III compound can improve the bonding performance of rubber composition and steel wire after hot-oxidative aging in the presence of metal ions.

Claims

1. A rubber composition, characterized in that: The raw materials of the rubber composition include 100 parts by mass of a diene elastomer, 0.2-5 parts by mass of a cobalt salt and 0.5-5 parts by mass of a compound of formula A: In formula A, R1 is selected from C1-C8 alkyl, and R2 is selected from C1-C8 alkyl.

2. The rubber composition according to claim 1, characterized in that In formula A, R1 is a methyl group, and R2 is selected from a C3-C6 alkyl group.

3. The rubber composition 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 III:

4. The rubber composition according to claim 1, characterized in that The diene elastomer is natural rubber.

5. The rubber composition according to claim 1, characterized in that The raw materials of the rubber composition further include 2-10 parts by mass of sulfur.

6. The rubber composition according to claim 1, characterized in that In the raw materials of the rubber composition, the compound of formula A is used in an amount of 1-3 parts by mass.

7. The rubber composition according to claim 1, characterized in that The rubber composition has one or more of the following characteristics: The raw materials of the rubber composition further include 30-70 parts by mass of reinforcing filler; the reinforcing filler preferably comprises carbon black and white carbon black; The raw materials of the rubber composition further include 2-15 parts by mass of an active agent; the active agent is preferably zinc oxide; The raw materials of the rubber composition also include 0.5-5 parts by mass of a tackifying resin; The raw materials of the rubber composition also include 1-10 parts by mass of a rubber adhesive; The raw materials of the rubber composition also include 0.5-5 parts by mass of an accelerator; the accelerator is preferably N,N′-dicyclohexyl-2-benzothiazolesulfenamide; The raw materials of the rubber composition also include 0.02-0.5 parts by mass of a rubber scorch retarder.

8. A rubber product, characterized in that: The rubber product comprises the rubber composition according to any one of claims 1 to 7; preferably, the rubber product is a tire belt layer.

9. Use of the compound of formula A in improving the mechanical properties of a rubber composition after thermal oxidative aging in the presence of metal ions and the bonding properties with steel wire: In formula A, R1 is selected from C1-C8 alkyl, and R2 is selected from C1-C8 alkyl; Preferably, in formula A, R1 is methyl, and R2 is selected from C3-C6 alkyl; Preferably, the compound of formula A is a compound of formula I, a compound of formula II or a compound of formula III:

10. The use according to claim 9, characterized in that The use comprises adding 0.5 to 5 parts by mass of the compound of formula A to the raw materials of a rubber composition containing 100 parts by mass of a diene elastomer and 0.2 to 5 parts by mass of a cobalt salt.

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