Rubber composition capable of preventing aging of metal ions and application thereof

Abstract

The invention discloses a compound as shown in a formula A and capable of being used as an anti-aging agent, a rubber composition containing the compound as shown in the formula A and application of the rubber composition. The rubber composition provided by the invention is used as all or part of a rubber matrix of a tire, in particular as tire belt rubber. The anti-aging agent provided by the invention can provide good rubber-steel wire bonding performance, improves the thermo-oxidative aging resistance of the rubber composition, especially can improve the mechanical property and bonding performance after aging in the presence of metal ions, and prolongs the service life of tires.

Description

Technical Field

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

[0002] As one of the main parts of a car, tires play an important role in carrying the weight of the car and transmitting traction and braking force. With the continuous development of the tire industry, radial tires have been widely used, and steel cords have become a very common reinforcement method, so the adhesion between rubber and steel cord has become very important. Studies have found that cobalt salts can play a good role in promoting the adhesion of rubber-steel cords. It is generally believed that cobalt salts increase the activity of sulfur and increase the generation rate of copper sulfide at the bonding interface, which is conducive to improving the adhesion performance.

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

[0004] Unsaturated rubber easily reacts with oxygen. Studies have found that the oxidation of unsaturated rubber proceeds according to the free radical chain reaction mechanism and has the characteristics of autocatalysis, and ions such as copper, manganese, and cobalt can catalyze the oxidation reaction of rubber. Metal ion catalysis can increase the oxidation rate sharply, accelerate the thermal oxidation of rubber, and cause great harm to rubber.

[0005] In the prior art, antioxidants are mostly used to inhibit the catalytic effect of metal ions, thereby improving the thermal oxidation aging resistance and other properties of rubber products. Among them, antioxidant 6PPD is a mainstream antioxidant widely used in the rubber industry, which can inhibit ozone aging and thermal oxidation aging of rubber products, and slow down rubber degradation under static conditions. However, antioxidant 6PPD has certain pollution, and the large-scale use of a single variety of antioxidant 6PPD in tire formulations will increase corporate costs. The performance retention rate of the tire under certain specific aging conditions during actual use cannot fully meet the requirements, and it is prone to problems such as frost spraying. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a rubber composition having excellent metal ion aging protection function and its use. The rubber composition of the present invention is used as all or part of the rubber matrix of a tire, especially as the tire belt rubber. The antioxidant of the present invention can provide good rubber-steel wire adhesion performance, improve the heat oxygen aging resistance and metal ion protection performance of the rubber composition, especially can improve the mechanical properties and adhesion performance after aging in the presence of metal ions, and extend the service life of the tire.

[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, R 1 is selected from C1-C8 alkyl, R 2 Selected from C1-C8 alkyl.

[0010] In one or more embodiments, in Formula A, R 1 is methyl, R 2 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]

[0013]

[0014] Another aspect of the present invention provides a rubber composition, the raw materials of the rubber composition comprising 100 parts by mass of a diene elastomer and 0.5-5 parts by mass of a compound of formula A as described in any embodiment herein.

[0015] 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.

[0016] In one or more embodiments, the diene elastomer is natural rubber.

[0017] In one or more embodiments, the raw materials of the rubber composition further include 2-10 parts by mass of sulfur.

[0018] In one or more embodiments, the compound of formula A is used in an amount of 1 to 3 parts by mass in the raw materials of the rubber composition.

[0019] 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.

[0020] 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.

[0021] In one or more embodiments, the raw material of the rubber composition further includes 0.5-5 parts by mass of a tackifying resin.

[0022] In one or more embodiments, the raw materials of the rubber composition further include 1 to 10 parts by mass of a rubber binder.

[0023] 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.

[0024] 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.

[0025] 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 belt layer.

[0026] Another aspect of the present invention provides the use of the compound of formula A described in any embodiment of the text in improving the mechanical properties of a rubber composition or rubber product after thermal oxidative aging in the presence of metal ions and the adhesion performance to steel wire.

[0027] In one or more embodiments, the use comprises adding 0.5-5 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 0.2-5 parts by mass of a cobalt salt. DETAILED DESCRIPTION

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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).

[0032] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0033] 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.

[0034] 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.

[0035] The present invention finds that the compound of formula A can be used as a rubber antioxidant:

[0036]

[0037] In formula A, R 1 is selected from C1-C8 alkyl, R 2 Selected from C1-C8 alkyl.

[0038] Herein, alkyl refers to a monovalent saturated group consisting of hydrogen atoms and carbon atoms. The alkyl group can be a straight chain alkyl group or a branched chain alkyl group. The alkyl group can contain 1-8 carbon atoms (C1-C8 alkyl group). Exemplary alkyl groups include, but are not limited to, methyl, ethyl, isopropyl, n-butyl, isobutyl, 1-methylpropyl, 1,3-dimethylbutyl, 1,4-dimethylpentyl, octyl, etc.

[0039] In some embodiments, in the compound of formula A, R 1 is selected from C1-C4 alkyl, such as C1-C2 alkyl. In some embodiments, in the compound of formula A, R 1 It is methyl.

[0040] In some embodiments, in the compound of formula A, R 2 In some embodiments, in the compound of formula A, R 2 Selected from isopropyl, 1-methylpropyl and 1,3-dimethylbutyl.

[0041] In some embodiments, in the compound of formula A, R 1 is selected from C1-C4 alkyl, such as C1-C2 alkyl, R 2 Selected from C1-C8 alkyl, such as C3-C6 alkyl.

[0042] In some embodiments, in the compound of formula A, R 1is methyl, R 2 Selected from C3-C6 alkyl.

[0043] 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:

[0044]

[0045]

[0046] 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 material, especially a tire belt layer rubber material) can impart excellent heat-oxidative aging resistance and good steel wire adhesion to the rubber composition, especially heat-oxidative aging resistance in the presence of metal ions (e.g., cobalt salts), and 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.

[0047] The present invention provides a method for preparing a compound of formula A, comprising the following steps:

[0048] (1) allowing aniline and the compound of formula B to undergo a condensation reaction under the action of a first catalyst to obtain a condensate containing the compound of formula C and / or the compound of formula C', and then subjecting the condensate to H 2 and a second catalyst to perform a reduction reaction to obtain a compound of formula D;

[0049]

[0050] (2) Compound D and compound E are reacted in H 2 and a third catalyst to perform a reductive alkylation reaction to obtain a compound of formula A;

[0051]

[0052] R in Formula A, Formula B, Formula C, Formula C' and Formula D 1 , R 2 As defined in any embodiment herein, R in Formula E 3 and R 4 Each independently selected from H and C1-C7 alkyl, those skilled in the art can 2 Determine the corresponding R in formula E 3 and R 4 .

[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 general formula (R a ) 4 NOH compound, where R a are four identical or different aliphatic groups (eg, alkyl groups) or aromatic groups. 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 ) 4 NX, where R b It is four identical or different aliphatic groups (such as alkyl) or aromatic groups, such as methyl, ethyl, propyl, butyl, etc., and X is a halogen atom, such as fluorine, chlorine, bromine, 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 ratio of the amount of the first catalyst to the amount of 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, 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.

[0054] 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 include an azobenzene compound:

[0055]

[0056] 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, 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, and the vacuum degree range is -0.09 to -0.99 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 in the supported metal catalysts 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 sieves, etc., and 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.

[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 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 in 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.

[0060] 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 solution 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.

[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 D may be 0.0001:1 to 0.2:1.

[0062] 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 a 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. 2The group selects a suitable compound of formula E to react. The amount ratio of the compound of formula E to the compound of formula D can be 1:1 to 15:1, such as 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, such as 50°C, 70°C, 80°C, 100°C, 120°C. The hydrogen pressure in step (2) can be 0.5 to 5MPa, preferably 0.5 to 2.5MPa, such as 1MPa, 1.2MPa, 1.5MPa, 1.8MPa, 2MPa, 2.5MPa.

[0063] 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 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 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).

[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 a compound of formula A as an antioxidant, wherein the amount of the compound of formula A may be 0.5-5 parts by mass based on 100 parts by mass of the diene elastomer. Herein, unless otherwise specified, the mass fractions 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] Herein, diene elastomer refers to an elastomer whose monomers contain dienes (such as butadiene, isoprene). Suitable diene elastomers for use in the present invention may be various diene elastomers known in the art, including but not limited to one or more selected from natural rubber (NR), butadiene rubber (BR), isoprene rubber, styrene-butadiene rubber (SBR), chloroprene rubber (CR), nitrile rubber (NBR), isoprene / butadiene copolymers, isoprene / styrene copolymers, and isoprene / butadiene / styrene copolymers. In some preferred embodiments, the diene elastomer contains natural rubber or consists of natural rubber.

[0069] The antioxidant contained in the rubber composition of the present invention includes a compound of formula A (e.g., a compound of formula I and / or a compound of formula II). In some embodiments, the rubber composition of the present invention does not contain other antioxidants except the compound of formula A. In the raw material of the rubber composition of the present invention, the amount of the compound of formula A 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 a compound of formula I and / or a compound of formula II, preferably including a compound of formula I. In some embodiments, the antioxidant in the rubber composition of the present invention is a compound of formula I, a compound of formula II, or a combination of the two, preferably a compound of formula I. 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 the compound of formula I, the compound of formula II and the compound of formula III when two or three of them are 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, 2.5 parts by mass.

[0070] 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, such as 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 for 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, such as 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, such as 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.

[0071] The raw materials of the rubber composition of the present invention include a crosslinking agent, such as sulfur. The sulfur is preferably insoluble sulfur. In the raw materials of the rubber composition of the present invention, the amount of sulfur can be 2-10 parts by mass, such as 3 parts by mass, 4 parts by mass, 5 parts by mass, 6 parts by mass, 7 parts by mass, 8 parts by mass, and 9 parts by mass.

[0072] The raw materials of the rubber composition of the present invention may also include other ingredients that can be used in the rubber composition, 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.

[0073] 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 also can 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 present invention, softener is optional to add. When the raw material of rubber composition of the present invention includes softener, the consumption of softener can be 1-10 mass parts, preferably 3-9 mass parts, such as 4 mass parts, 5 mass parts, 6 mass parts, 7 mass parts, 8 mass parts.

[0074] 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. 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, 4 parts by mass.

[0075] The activator can accelerate the vulcanization speed, improve the thermal conductivity, wear resistance, tear resistance of rubber and the like. The raw material of the rubber composition of the present invention preferably includes an activator. Examples of activators include ZnO. In the raw material of the rubber composition of the present invention, the amount of the activator can be 2-15 parts by mass, such as 5 parts by mass, 6 parts by mass, 7 parts by mass, 8 parts by mass, 9 parts by mass, 10 parts by mass, 12 parts by mass. In some preferred embodiments, the activator includes ZnO, or the activator is ZnO. In some preferred embodiments, in the raw material of the rubber composition of the present invention, the amount of ZnO is 2-15 parts by mass, such as 5 parts by mass, 6 parts by mass, 7 parts by mass, 8 parts by mass, 9 parts by mass, 10 parts by mass, 12 parts by mass.

[0076] Cobalt salts can play a good role in promoting the adhesion of rubber-steel cords. When used as a tire belt layer rubber material, the raw materials of the rubber composition of the present invention preferably contain cobalt salts. The cobalt salts that can be used in the present invention include but are not limited to cobalt boroacylate, cobalt neodecanoate, etc. In the raw materials of the rubber composition of the present invention, the amount of cobalt salt 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, 3 parts by mass.

[0077] Tackifying resin is used to enhance the adhesion between rubber and steel cord. When used as tire belt layer rubber, the raw material of the rubber composition of the present invention preferably includes 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, 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.

[0078] The rubber adhesive can be an adhesive containing a methylene donor (e.g., 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 layer rubber compound, the raw material of the rubber composition of the present invention preferably includes a rubber adhesive. Available rubber adhesives include rubber adhesives whose effective ingredient is hexamethoxymethyl melamine (HMMM for short), such as rubber adhesive RA. Rubber adhesive RA is composed of HMMM and an inorganic carrier. Examples of rubber adhesive RA include rubber adhesive RA-65. The mass fraction of HMMM in rubber adhesive RA-65 is 65%. In the raw material 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, 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.

[0079] The rubber anti-scorch agent is used to prevent the rubber compound from producing early vulcanization during processing, and can be selected from one or more of nitroso compounds (such as N-nitrosodiphenylamine), organic acids (such as benzoic acid, phthalic anhydride) and thioimides (such as N-cyclohexylthiophthalimide) and the like. Examples of rubber anti-scorch agents include rubber anti-scorch agent CTP (N-cyclohexylthiophthalimide). The raw materials of the rubber composition of the present invention preferably include rubber anti-scorch agents. In the raw materials 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, the rubber anti-scorch agent includes rubber anti-scorch agent CTP, or the rubber anti-scorch agent is rubber anti-scorch agent CTP.

[0080] 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 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 mass parts, such as 1 mass part, 1.4 mass parts, 1.5 mass parts, 2 mass parts, 3 mass parts. In some preferred embodiments, the accelerator is accelerator DZ (N, N'-dicyclohexyl-2-benzothiazole sulfenamide).

[0081] 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.

[0082] When the rubber composition is used as a tire belt layer rubber material, the rubber composition of the present invention preferably comprises a bonding system consisting of a resorcinol donor (e.g., a resorcinol-formaldehyde resin), a methylene donor (e.g., HMMM) and white carbon black, which can effectively improve the adhesion between rubber and metal. The amounts of the resorcinol donor, the methylene donor and the white carbon black can be as described in any embodiment of the present invention.

[0083] 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, 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., a rubber adhesive RA), 0.02-0.5 parts by mass of a rubber scorch retarder (e.g., a rubber scorch retarder CTP) and 0.5-5 parts by mass of an accelerator (e.g., an accelerator DZ), or consist of the above ingredients.

[0084] The unvulcanized rubber of the present invention can be prepared by conventional rubber mixing methods, for example, by a two-stage mixing method: one stage of thermomechanical (e.g., internal mixer) mixing, mixing the rubber composition raw materials except the crosslinking agent, rubber adhesive and accelerator, kneading the entire mixture until the maximum temperature between 110°C and 190°C is reached to obtain a first-stage rubber; and a second stage of thermomechanical (e.g., open mixer) mixing, mixing the first-stage rubber with the crosslinking agent, rubber adhesive and accelerator to obtain a second-stage rubber, i.e., the unvulcanized rubber.

[0085] The unvulcanized rubber is vulcanized (cured) to obtain vulcanized rubber. The vulcanization temperature is usually 130-200°C, such as 140-160°C, 150±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.

[0086] Compared with the rubber composition using the antioxidant 6PPD, the rubber composition using the formula A compound (e.g., one or more of the formula I compound, the formula II compound, and the formula III compound) as the antioxidant is used in rubber products, such as tires, especially tire belt layers, which can make the rubber products have better mechanical properties after thermal oxidation aging in the presence of metal ions (e.g., cobalt ions) and adhesion between rubber and steel wire. Therefore, the present invention also provides a rubber product, which contains the rubber composition described herein. The rubber product can be a tire, a rubber shoe, a sealing strip, a soundproof board, a shockproof pad, etc. The rubber product is preferably a tire, such as a tire belt layer, etc.

[0087] 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 a rubber product after thermal oxidative aging in the presence of metal ions (e.g., cobalt ions) and the adhesion properties to a steel wire, and a method for improving the mechanical properties of a rubber composition or a rubber product after thermal oxidative aging in the presence of metal ions (e.g., cobalt ions) and the adhesion properties to a steel wire. Preferably, the use or method of the present invention comprises: 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.

[0088] 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.

[0089] The sources and specifications of the raw materials used in the examples are as follows:

[0090] Natural rubber (NR): Xishuangbanna Sinochem Rubber Co., Ltd., SCR5;

[0091] Carbon black: Shanghai Cabot Carbon Black Co., Ltd., N330;

[0092] Silica: Shanghai Kaiyin Chemical Co., Ltd., VN3;

[0093] Zinc oxide: Yonghua Chemical Technology (Jiangsu) Co., Ltd.

[0094] Cobalt boroacylate: Zhejiang Jinmao Rubber Additives Co., Ltd., in compliance with industry standard HG / T 4072-2008;

[0095] Antioxidant 6PPD: Shengao Chemical Technology Co., Ltd.;

[0096] Resorcinol-formaldehyde resin: SI Group Chemical Co., Ltd., SL3022;

[0097] Rubber adhesive RA-65: Shandong Ruiqi Chemical Co., Ltd.;

[0098] Rubber anti-scorch agent CTP: Shandong Yanggu Huatai Chemical Co., Ltd.;

[0099] Insoluble sulfur: Sanao Chemical Technology Co., Ltd., HD OT20;

[0100] Accelerator DZ: Weilin New Materials Technology Co., Ltd.

[0101] Preparation Example 1

[0102] (1) Synthesis of Compound IV

[0103] In a 500mL four-necked flask, 139.7g (1.5mol) of aniline and 91g (0.25mol) of a 25% aqueous solution of tetramethylammonium hydroxide (TMAOH) were added, stirred and heated to 40-55°C, and dehydrated by vacuum distillation to form salts of TMAOH and aniline. During this process, the reaction solution gradually changed from yellow to dark red; the temperature was gradually raised to 72°C. When the fraction was about 46mL, 34.3g (0.25mol) of 3-methylnitrobenzene was added dropwise at 72°C under reduced pressure (-0.098MPa) for about 3h. After the addition was completed, the temperature was kept for 1h. LC was monitored until the reaction of 3-methylnitrobenzene was complete to obtain a condensation solution.

[0104] 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, hydrogen was introduced to 1.5 MPa for hydrogenation reduction reaction, and LC was monitored until the nitro and nitroso compounds were completely reduced. Then, the reaction was filtered and phase-separated, and the organic phase was washed with water and distilled under reduced pressure (-0.1 MPa, 160°C) to evaporate aniline and light component by-products, and finally 42.6 g of the reduction product (Compound IV) was distilled out, cooled and solidified into a yellow solid, with a yield of about 86%, and the content detected by GC was >99%.

[0105]

[0106] LC-MS (m / z): 198.22 (M-H+).

[0107] 1 H NMR (400 MHz, CDCl 3 )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).

[0108] (2) Synthesis of Compounds of Formula I

[0109] 46g (0.23mol) of compound IV, 70g (0.70mol) of 4-methyl-2-pentanone and 0.8g of Pt / C catalyst were put into a reactor, replaced with hydrogen 3 times, heated to 80°C, and hydrogen was passed to 1.8MPa for reaction. GC was used for detection. When the content of compound IV was less than 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 60.4g of compound I (yield of about 93%), and the content detected by GC was >95.8%. After cooling and solidification, it was a red liquid.

[0110]

[0111] Molecular formula: C 19 H 26 N 2

[0112] LC-MS (m / z): 282.40 (M-H+).

[0113] Preparation Example 2

[0114] (1) Synthesis of Compound IV

[0115] The synthesis of the compound of formula IV is the same as that of Preparation Example 1.

[0116] (2) Synthesis of Compound II

[0117] 40g (0.2mol) of compound IV, 151.4g (2.1mol) of 2-butanone and 0.5g of Pt / C catalyst were put into a reactor, replaced with hydrogen 3 times, heated to 80°C, and hydrogen was passed to 1.5MPa for reaction. GC was used for detection. When the content of compound IV was less than 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 50.9g of compound II (yield of about 99%), and the content was >99% by GC detection. After cooling and solidification, it was a light red solid.

[0118]

[0119] Molecular formula: C 17 H 22 N 2

[0120] LC-MS (m / z): 254.35 (M-H+).

[0121] 1 H NMR (400 MHz, CDCl 3 )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).

[0122] Preparation Example 3

[0123] (1) Synthesis of Compound IV

[0124] The synthesis of the compound of formula IV is the same as that of Preparation Example 1.

[0125] (2) Synthesis of compound of formula III

[0126] 40g (0.2mol) of compound IV, 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 hydrogen was passed to 1.5MPa for reaction. The reaction was stopped when the content of compound IV was <0.1%. 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 48.3g of compound III (yield of about 99.4%), and the content detected by GC was >98%. After cooling and solidification, it was a light pink solid.

[0127]

[0128] Molecular formula: C 16 H 20 N 2

[0129] LC-MS (m / z): 240.35 (M-H+).

[0130] 1 H NMR (400 MHz, CDCl 3 )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).

[0131] Examples 1-6 and Comparative Examples 1-4

[0132] 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:

[0133] (1) The first stage of mixing was carried out in an internal mixer with an initial temperature of 70°C and a rotor speed of 60 r / min. -1 , add natural rubber into an internal mixer, then add 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, knead until the temperature of the rubber reaches 150° C. to obtain a rubber section;

[0134] (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;

[0135] (3) The second-stage rubber is vulcanized at 151°C for 30 minutes to obtain a vulcanized rubber.

[0136] Table 1: Formulations of the rubber compositions of Examples 1-6 and Comparative Examples 1-4 (unit: parts by mass)

[0137]

[0138]

[0139] Test Example 1: Mechanical properties before and after thermal oxidation aging

[0140] 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:

[0141] Tensile strength and elongation at break: GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber;

[0142] 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.

[0143] Tensile strength retention after aging = tensile strength after aging / tensile strength before aging × 100%

[0144] Retention rate of elongation at break after aging = elongation at break after aging / elongation at break before aging × 100%

[0145] 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.

[0146] Table 2: Mechanical properties of the rubber compositions of Examples 1-6 and Comparative Examples 1-4 before and after aging

[0147]

[0148] As can be seen from Table 2, the mechanical properties of 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 before aging are close to those of the rubber compositions of Comparative Examples 3-4 to which the antioxidant 6PPD is added. The retention rates of tensile strength and elongation at break of the rubber composition of Comparative Example 1 after aging are lower than those of Comparative Example 2, indicating that the addition of cobalt salt has an adverse effect on the thermal oxidative aging performance. Compared with the rubber composition of Comparative Example 1, the retention rates of tensile strength and elongation at break of 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 after aging are greatly improved, indicating that the compounds of Formula I, Formula II, and Formula III can give the rubber compositions good thermal oxidative aging resistance and metal ion protection performance. In particular, under the same amount of antioxidant, the rubber compositions of Examples 1-2 added with the compound of Formula I, the rubber compositions of Examples 3-4 added with the compound of Formula II, and the rubber compositions of Examples 5-6 added with the compound of Formula III have higher retention rates of tensile strength and elongation at break after heat-oxidative aging in the presence of metal ions than the rubber compositions of Comparative Examples 3-4 added with the antioxidant 6PPD, indicating that the compounds of Formula I, Formula II and Formula III have better effects on improving the heat-oxidative aging resistance and metal ion protection performance of the rubber compositions than the antioxidant 6PPD.

[0149] Test Example 2: Steel Wire Adhesion Performance

[0150] The bonding strength between the vulcanized rubber of Examples 1-6 and Comparative Examples 1-4 and the steel cord before and after thermal oxidation aging was tested according to the following standards. The results are shown in Table 3:

[0151] Adhesion strength: GB / T 16586-1996 Determination of adhesion strength between vulcanized rubber and steel cord;

[0152] 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.

[0153] Adhesion strength retention rate after aging = Adhesion strength after aging / Adhesion strength before aging × 100%

[0154] 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

[0155]

[0156] As shown in Table 3, compared with the vulcanized rubber of Comparative Example 2 without adding cobalt salt, the vulcanized rubber of Comparative Example 1 with added cobalt salt has higher bonding strength, indicating that the addition of cobalt salt improves the rubber-steel wire bonding performance. The bonding strength of the vulcanized rubber of Examples 1-2 with added Formula I compound and the vulcanized rubber of Examples 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, indicating that the Formula I compound and the Formula II compound can improve the bonding performance of the rubber composition and the steel wire. The bonding strength of the vulcanized rubber of Examples 1-2 with added Formula I compound, the bonding strength of the vulcanized rubber of Examples 3-4 with added Formula II compound and the bonding strength retention rate of the vulcanized rubber of Examples 5-6 with added Formula III compound after thermal oxidative aging is higher than the vulcanized rubber of Comparative Example 3-4 with added antioxidant 6PPD, indicating that the Formula I compound, the Formula II compound and the Formula III compound can improve the bonding performance of the rubber composition and the steel wire after thermal 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 further 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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