Anti-moisture heat degradation and anti-ozone degradation inhibitors, rubber compositions, and their uses

Abstract

The present invention provides a compound of formula A used as a degradation inhibitor, a degradation inhibitor composition comprising the compound of formula A and the degradation inhibitor STMQ, a rubber composition comprising the degradation inhibitor composition or the compound of formula A, and applications thereof. The compound of formula A is as described in the specification. The degradation inhibitor and degradation inhibitor composition of the present invention significantly improve the moisture-heat degradation resistance properties of tire rubber compounding, while also possessing excellent ozone degradation resistance properties, thereby improving the service life of tires in special and harsh environments.

Description

[Technical Field]

[0001] This invention belongs to the field of rubber materials and relates to degradation inhibitors against humid heat degradation and ozone degradation, rubber compositions, and their applications. [Background technology]

[0002] During storage, processing, and use, rubber products are susceptible to internal and environmental factors (heat, oxygen, ozone, ultraviolet light, chemicals, etc.), which can lead to a decrease in their properties or damage. Oxygen is a significant factor in rubber degradation, and the absorption of thermal energy is a major cause of thermal decomposition of polymer materials in a vacuum or inert atmosphere. At the same time, thermal energy can accelerate the oxidation reaction of rubber products. Ozone is more reactive than oxygen, and its impact on rubber, especially unsaturated rubber, is far more severe than that of oxygen. The reaction between ozone and the double bonds in rubber accelerates the initiation and growth of cracks. Furthermore, as ozone concentration increases, the time to crack initiation shortens, and the rate of crack growth increases.

[0003] Currently, in tire compounding, physical and chemical degradation inhibitors are typically used in combination to improve the anti-ozone degradation properties of tires, including static and dynamic characteristics. Chemical degradation inhibitors, particularly p-phenylenediamine-based inhibitors such as 6PPD (N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine) and IPPD (N-isopropyl-N'-phenyl-p-phenylenediamine), are widely used in the tire industry due to their excellent and diverse overall protective properties (ozone, thermal oxidation, and dynamic fatigue properties).

[0004] Water (precipitation, humidity, condensation, etc.) plays a significant role in accelerating the deterioration of rubber products. Water extraction typically accelerates the leaching of antioxidants from the rubber product surface, thus promoting deterioration and reducing its mechanical properties.

[0005] When the external environment in which rubber products are used and stored becomes more severe, for example, in high-temperature and high-humidity environments, the water solubility (water-resistant extraction properties) of degradation inhibitors varies greatly depending on the type, and the concentration / ratio of degradation inhibitors in rubber compounding decreases significantly, ultimately leading to a significant reduction in the protective effect of rubber products. According to relevant literature, both the degradation inhibitors IPPD and 6PPD have poor water-resistant extraction properties. [Overview of the project]

[0006] In view of the challenges of existing technologies, the present invention provides a degradation inhibitor having anti-moisture-heat degradation and anti-ozone degradation effects, a degradation inhibitor composition containing the degradation inhibitor, a rubber composition containing the degradation inhibitor or degradation inhibitor composition, and applications thereof. The degradation inhibitor and degradation inhibitor composition of the present invention significantly improve the anti-moisture-heat degradation properties of a rubber composition, such as a tire rubber compound, without changing its initial physical properties or anti-thermal oxidative degradation properties, while also possessing excellent anti-ozone degradation properties, thereby improving the service life of rubber products, such as tires, in special and harsh environments.

[0007] Specifically, one aspect of the present invention provides a compound of formula A used as a degradation inhibitor.

[0008] [ka] In formula A, R1, R2, and R3 are each independently selected from C1-C8 alkyl groups.

[0009] In one or more embodiments, in formula A, R1 and R2 are each independently selected from C1-C2 alkyl groups, and R3 is selected from C3-C6 alkyl groups, preferably from C4-C6 alkyl groups.

[0010] In one or more embodiments, the compound of formula A is the compound of formula I, the compound of formula II, the compound of formula IV, or the compound of formula VI.

[0011] [ka] In one or more embodiments, the compound of formula A does not include a compound in which R1 and R2 are methyl groups and R3 is an isopropyl group.

[0012] Another aspect of the present invention provides a degradation inhibitor composition comprising a degradation inhibitor STMQ and a compound of formula A according to any one embodiment herein, wherein the degradation inhibitor STMQ is a 2,2,4-trimethyl-1,2-dihydroquinoline polymer having a total mass of ≥80% dimers, trimers, and tetramers of 2,2,4-trimethyl-1,2-dihydroquinoline.

[0013] In one or more embodiments, the mass ratio of the compound of formula A to the degradation inhibitor STMQ in the above-mentioned degradation inhibitor composition is 1:1 to 3:1, preferably 1.5:1 to 2.5:1.

[0014] Another aspect of the present invention provides a rubber composition in which the raw materials of the rubber composition comprise 100 parts by mass of a diene elastomer and 1 to 5 parts by mass of a compound of formula A according to any one embodiment of this specification, or the raw materials of the rubber composition comprise 100 parts by mass of a diene elastomer and 1 to 5 parts by mass of a degradation inhibitor composition according to any one embodiment of this specification.

[0015] In one or more embodiments, the diene elastomer comprises natural rubber and butadiene rubber, preferably with a mass ratio of 1:2 to 2:1 between the natural rubber and the butadiene rubber.

[0016] In one or more embodiments, the raw materials of the rubber composition further include 30 to 70 parts by mass of a reinforcing filler, preferably carbon black.

[0017] In one or more embodiments, the raw materials of the rubber composition further comprise 1 to 10 parts by mass of an activator, preferably zinc oxide.

[0018] In one or more embodiments, the raw materials of the rubber composition further include 2 to 15 parts by mass of a softening agent. Preferably, the softening agent includes aromatic oil and stearic acid with a mass ratio of 1:1 to 5:1.

[0019] In one or more embodiments, the raw materials of the rubber composition further include 0.5 to 3 parts by mass of sulfur.

[0020] In one or more embodiments, the raw materials of the rubber composition further include 0.2 to 2 parts by mass of an accelerator. Preferably, the accelerator is N-tert-butyl-2-benzothiazolesulfenamide.

[0021] Another aspect of the present invention provides a rubber product, which includes the rubber composition according to any one of the embodiments herein. Preferably, the rubber product is a tire.

[0022] The present invention further provides the use of the compound of formula A according to any one of the embodiments herein or the anti-degradant composition according to any one of the embodiments herein in improving the anti-moisture heat degradation characteristics and / or anti-ozone degradation characteristics of a rubber composition or a rubber product.

Embodiments for Carrying out the Invention

[0023] For those skilled in the art to understand the features and effects of the present invention, the terms mentioned in the specification and claims are generally explained and defined as follows. Unless otherwise specified, all technical terms and scientific terms used in this specification have the ordinary meanings understood by those skilled in the art regarding the present invention. In case of conflict, they shall conform to the definitions in this specification.

[0024] The theories or mechanisms described and disclosed in this specification, whether correct or not, do 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.

[0025] In this specification, “inclusion,” “contains,” “containing,” and similar terms encompass the meanings of “essentially consisting of” and “consisting of.” For example, when “A includes B and C” is disclosed herein, “A essentially consists of B and C” and “A consists of B and C” should be considered as being disclosed herein.

[0026] In this specification, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, content, and concentrations, are provided solely for the sake of brevity and convenience. Therefore, the description of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible secondary ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0027] In this specification, unless otherwise specified, "percent" means mass percentage and "ratio" means mass ratio.

[0028] The embodiments or examples described herein should be understood not to limit the invention. Conversely, all substitutes, improvements and equivalents of the methods and materials described herein are included within the scope limited by the claims.

[0029] For the sake of brevity, this specification does not describe all possible combinations of the various technical features in each embodiment or example. Therefore, as long as these combinations of technical features are inconsistent, each technical feature in each embodiment or example can be combined arbitrarily, and all combinations should be considered to be within the scope of this specification.

[0030] In the present invention, the compound of formula A has the following structure.

[0031] [ka] In formula A, R1, R2, and R3 are each independently selected from C1-C8 alkyl groups.

[0032] In the present invention, an alkyl group means a linear or branched monovalent saturated hydrocarbon group. The alkyl group may contain 1 to 8 carbon atoms (C1 to C8 alkyl groups). Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, 1-methylpropyl, isobutyl, 1-methylbutyl, and 1,3-dimethylbutyl groups.

[0033] In formula A, R1 may be located at the ortho, meta, or para position of the -NH- group in the benzene ring, and R2 may be located at the ortho, meta, or para position of R1. In some embodiments, R1 is located at the ortho position of the -NH- group in the benzene ring, and R2 is located at the ortho position of R1. In some embodiments, R1 is located at the meta position of the -NH- group in the benzene ring, and R2 is located at the para position of the -NH- group in the benzene ring.

[0034] Preferably, in formula A, R1 and R2 are each independently selected from C1-C4 alkyl groups, and more preferably selected from C1-C3 alkyl groups, such as a methyl group and an ethyl group.

[0035] Preferably, in formula A, R3 is selected from C3-C8 alkyl groups, and more preferably from C3-C6 alkyl groups or C4-C6 alkyl groups, such as isopropyl group, 1-methylpropyl group, 1-methylbutyl group, and 1,3-dimethylbutyl group.

[0036] In some preferred embodiments, in formula A, R1 and R2 are each independently selected from C1-C2 alkyl groups, and R3 is selected from C3-C6 alkyl groups, preferably from C4-C6 alkyl groups.

[0037] In some embodiments, the compound of formula A is the compound of formula I, the compound of formula II, the compound of formula IV, or the compound of formula VI.

[0038] [ka] The present invention has discovered that, in rubber compositions, particularly tire rubber compositions, the use of a compound of formula A can significantly improve the moisture-heat degradation resistance and ozone degradation resistance of the rubber composition, and that this improvement effect is clearly superior to that of conventional p-phenylenediamine-based degradation inhibitors (e.g., IPPD), while simultaneously maintaining excellent initial physical properties and heat- and oxidative degradation resistance. Furthermore, the present invention has discovered that, in rubber compositions, particularly tire rubber compositions, the use of a compound of formula A and the degradation inhibitor STMQ in combination can significantly improve the moisture-heat degradation resistance and ozone degradation resistance of the rubber composition, and that this improvement effect is clearly superior to that of conventional p-phenylenediamine-based degradation inhibitors (e.g., IPPD) and the degradation inhibitor STMQ in combination, while simultaneously maintaining excellent initial physical properties and heat- and oxidative degradation resistance.

[0039] In the present invention, the degradation inhibitor STMQ is a 2,2,4-trimethyl-1,2-dihydroquinoline polymer having a total mass of ≥80% of dimers, trimers, and tetramers of 2,2,4-trimethyl-1,2-dihydroquinoline. The 2,2,4-trimethyl-1,2-dihydroquinoline polymer (also called the degradation inhibitor TMQ) has the structure shown in formula B.

[0040] [ka] In equation B, n represents the degree of polymerization.

[0041] In the present invention, the compound of formula A can be produced by a method comprising the following steps.

[0042] (1) The compound of formula C and nitrobenzene are condensed in the presence of a first catalyst to obtain a condensate containing the compound of formula D and / or the compound of formula D'. Then, the condensate is reduced in the presence of H2 and a second catalyst to obtain the compound of formula E.

[0043] [ka] (2) Compound E and compound F are subjected to a reductive alkylation reaction in the presence of H2 and a third catalyst to obtain compound A.

[0044] [ka] In formulas A, C, D, and E, R1, R2, and R3 are as described in any one embodiment of this specification, and in formula F, R4 and R5 are each independently selected from H and C1-C7 alkyl groups, and those skilled in the art can determine appropriate R4 and R5 in formula F based on R3 contained in the compound of formula A.

[0045] The first catalyst used in step (1) may be one or more selected from alkali metal hydroxides, alkali metal alkoxides, quaternary ammonium bases, and combinations of alkali metal hydroxides and tetraalkylammonium halides. Alkali metal hydroxides applicable to the present invention include sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. Alkali metal alkoxides applicable to the present invention include sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, potassium tert-butoxide, sodium tert-amilate, potassium tert-amilate, etc. Quaternary ammonium bases are R 1 This is a general term for compounds having the general formula 4NOH, where R represents four homologous or distinct aliphatic hydrocarbon groups or aromatic hydrocarbon groups. In the quaternary ammonium bases applied to this invention, R represents... 1The group may be one or more selected from methyl, ethyl, propyl, and butyl groups. Examples of quaternary ammonium bases applicable to the present invention include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. The first catalyst may also be a combination of an alkali metal hydroxide and a tetraalkylammonium halide. The general formula for a tetraalkylammonium halide is R 2 4NX, and R in the formula 2 is one of four homologous or distinct aliphatic or aromatic hydrocarbon groups, such as a methyl group, an ethyl group, a propyl group, or a butyl group, and X is a halogen atom, such as fluorine, chlorine, bromine, or iodine. Examples of combinations of alkali metal hydroxides and tetraalkylammonium halides include sodium hydroxide and tetrabutylammonium bromide.

[0046] The molar ratio of the first catalyst to the compound of formula C can be 0.1:1 to 2:1, preferably 0.9:1 to 1.1:1, for example 1.05:1, 1.1:1, or 1.5:1. In some embodiments, step (1) involves first forming a salt with the compound of formula C and then adding nitrobenzene dropwise to carry out a condensation reaction.

[0047] In step (1), the condensate obtained by condensing the compound of formula C with nitrobenzene in the presence of the first catalyst may be one or both of the nitro compound represented by formula D and the nitroso compound represented by formula D', and may also include an azobenzene compound.

[0048] In step (1), the molar ratio of the compound of formula C to nitrobenzene can be 2:1 to 15:1, preferably 4:1 to 10:1, and more preferably 5:1 to 8.1, for example 6:1 or 7:1.

[0049] The condensation reaction in step (1) can be carried out at 40 to 90°C, preferably 65 to 85°C, for example the reaction temperature may be 60°C, 70°C, 75°C, or 80°C. The condensation reaction is carried out under vacuum conditions, with a pressure range of -0.09 to -0.1 MPa.

[0050] The second catalyst used in step (1) may be a porous metal catalyst or a supported metal catalyst. A porous metal catalyst is also called a sponge metal catalyst. Examples of porous metal catalysts applicable to the present invention include Raney nickel (also called skeleton nickel), Raney cobalt, and Raney copper. A supported metal catalyst includes a metal that serves as the catalytic active center and a support that holds the metal. Examples of metals used in the supported metal catalyst applicable to the present invention include nickel, cobalt, copper, platinum, palladium, ruthenium, and rhodium, and examples of supports include carbon, alumina, silica gel, and molecular sieves, with activated carbon being an example of the carbon used as a support. The molar ratio of the metal to the condensate in the second catalyst may be 0.0001:1 to 0.2:1.

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

[0052] In step (1), 2,3-dimethylaniline itself can be used as the solvent, or solvents such as toluene or xylene can be used. After the reaction in step (1) is complete, the reaction mixture is filtered, washed with water, and phase separated. The organic phase is then removed by vacuum distillation to obtain the compound of formula E.

[0053] The third catalyst used in step (2) may be the supported metal catalyst described above, for example, Pt / C. The molar ratio of the metal to the compound of formula E in the third catalyst may be 0.0001:1 to 0.2:1.

[0054] In step (2), the carbonyl carbon atom in the compound of formula F after the reaction is bonded to the amino nitrogen atom in the compound of formula E. Therefore, an appropriate compound of formula F can be selected and reacted depending on the R3 group contained in the compound of formula A to be prepared. The molar ratio of the compound of formula F to the compound of formula E can be 1:1 to 15:1, for example 2:1, 3:1, 5:1, 8:1, or 10:1. The reaction temperature in step (2) can be 40 to 150°C, for example 50°C, 80°C, 100°C, or 120°C. The hydrogen pressure in step (2) can be 0.5 to 5 MPa, for example 1 MPa, 1.5 MPa, 2 MPa, or 2.5 MPa.

[0055] In step (2), the compound of formula F, which is the reaction raw material, may be used as the solvent. After the reaction in step (2) is complete, the reaction mixture is filtered and distilled under reduced pressure to remove light components and obtain the compound of formula A.

[0056] In the present invention, liquid chromatography (LC) or gas chromatography (GC) can be used to determine whether the reaction in each step has reached its endpoint, and to determine an appropriate reaction time.

[0057] The degradation inhibitor composition of the present invention comprises (1) one or more compounds of formula A, and (2) a degradation inhibitor STMQ. In some embodiments, the degradation inhibitor composition of the present invention comprises a compound of formula A and a degradation inhibitor STMQ. In the degradation inhibitor composition of the present invention, the mass ratio of the compound of formula A to the degradation inhibitor STMQ may be 1:1 to 3:1, for example, 1.5:1, 2:1, or 2.5:1.

[0058] The raw materials for rubber compositions generally include diene elastomers, reinforcing fillers, degradation inhibitors, and crosslinking agents. In this specification, rubber compositions include unvulcanized rubber and vulcanized rubber. Unvulcanized rubber can be converted into vulcanized rubber by vulcanization (curing).

[0059] The raw materials for the rubber composition of the present invention include a diene elastomer and one or more compounds of formula A, where, if the amount of diene elastomer used is 100 parts by mass, the amount of compound of formula A used may be 1 to 5 parts by mass, preferably 1 to 3 parts by mass, for example, 1.5 parts by mass, 2 parts by mass, or 2.5 parts by mass. In this specification, unless otherwise specified, the mass of the diene elastomer in the raw materials of the rubber composition is set to 100 parts by mass as the basis for calculating the parts by mass of the other components in the raw materials of the rubber composition.

[0060] In some embodiments, the raw materials for the rubber composition of the present invention include a diene elastomer and the degradation inhibitor composition of the present invention, wherein the amount of the degradation inhibitor composition of the present invention used may be 1 to 5 parts by mass, for example, 1.5 parts by mass, 2 parts by mass, 2.5 parts by mass, 3 parts by mass, 3.5 parts by mass, or 4 parts by mass.

[0061] In this specification, a diene elastomer refers to an elastomer whose monomer is a diene (e.g., butadiene, isoprene). The diene elastomers applicable to the present invention may be various diene elastomers well known in the art, and include, but are 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 copolymer, isoprene / styrene copolymer, and isoprene / butadiene / styrene copolymer. In some preferred embodiments, the diene elastomer includes natural rubber and butadiene rubber, or consists of natural rubber and butadiene rubber. The mass ratio of natural rubber to butadiene rubber is preferably 1:2 to 2:1, for example 1:1.5 to 1.5:1, 4.5:5.5 to 5.5:4.5, or 1:1.

[0062] The rubber composition of the present invention contains a compound of formula A as the degradation inhibitor. In the raw materials of the rubber composition of the present invention, the amount of compound of formula A used may be 1 to 5 parts by mass, preferably 1 to 3 parts by mass, for example, 1.5 parts by mass, 2 parts by mass, or 2.5 parts by mass. Controlling the amount of compound of formula A used within the above range is advantageous in ensuring improved anti-moisture heat degradation properties and anti-ozone degradation properties with a low amount of use.

[0063] In some embodiments, the raw materials for the rubber composition of the present invention include the compound of formula A and the degradation inhibitor STMQ, i.e., the degradation inhibitor composition of the present invention. In the raw materials for the rubber composition of the present invention, the amount of the degradation inhibitor composition of the present invention used may be 1 to 5 parts by mass, for example 1.5 parts by mass, 2 parts by mass, 2.5 parts by mass, 3 parts by mass, 3.5 parts by mass, or 4 parts by mass, where the amount of the degradation inhibitor STMQ used is preferably 0.5 to 2 parts by mass, for example 0.8 parts by mass, 1 part by mass, 1.2 parts by mass, or 1.5 parts by mass, and the amount of the compound of formula A used is preferably 1 to 3 parts by mass, for example 1.5 parts by mass, 2 parts by mass, or 2.5 parts by mass. Controlling the amount of the degradation inhibitor composition of the present invention used within the above range is advantageous in ensuring improved anti-moisture heat degradation properties and anti-ozone degradation properties with a low amount of use.

[0064] In some embodiments, the degradation inhibitor contained in the raw materials of the rubber composition of the present invention contains only the compound of formula A, or contains only the compound of formula A and the degradation inhibitor STMQ.

[0065] The raw materials for the rubber composition of the present invention may include a reinforcing filler. In the raw materials for the rubber composition of the present invention, the amount of reinforcing filler used may be 30 to 70 parts by mass, for example, 40 parts by mass, 45 parts by mass, 50 parts by mass, 55 parts by mass, or 60 parts by mass. The reinforcing filler applied to the present invention may be a reinforcing filler commonly used in rubber compositions, and may include, but is not limited to, one or more selected from carbon black, white carbon black, titanium dioxide, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, clay, and talc. In some preferred embodiments, the reinforcing filler includes carbon black, or the reinforcing filler is carbon black.

[0066] The raw materials for the rubber composition of the present invention include a crosslinking agent, such as sulfur. In the raw materials for the rubber composition of the present invention, the amount of sulfur used may be 0.5 to 3 parts by mass, for example, 1 part by mass, 1.5 parts by mass, 2 parts by mass, or 2.5 parts by mass.

[0067] The raw materials of the rubber composition of the present invention may further include other components commonly used in rubber compositions, and may include, but are not limited to, one or more selected from softeners, protective waxes, surfactants, and accelerators.

[0068] A softening agent can be used to improve the processability of the rubber composition. The softening agent may include petroleum-based softening agents, such as naphthenic oils, aromatic oils, processing oils, lubricating oils, paraffin, liquid paraffin, petroleum asphalt, and petrolatum. It may also include fatty oil-based softening agents, such as stearic acid, castor oil, linseed oil, rapeseed oil, coconut oil, waxes (e.g., beeswax, carnauba wax, and lanolin), tall oil, linoleic acid, palmitic acid, and lauric acid. In the raw materials of the rubber composition of the present invention, the amount of softening agent used may be 2 to 15 parts by mass, for example, 3 parts by mass, 5 parts by mass, 7 parts by mass, 8 parts by mass, 9 parts by mass, 10 parts by mass, 11 parts by mass, or 13 parts by mass. In some preferred embodiments, the softening agent includes arene oil and stearic acid, or consists of arene oil and stearic acid. The mass ratio of aromatic oil to stearic acid may be 1:1 to 5:1, for example, 2:1, 3:1, 3.5:1, or 4:1. In some preferred embodiments, the amount of aromatic oil used in the raw materials of the rubber composition of the present invention is 1 to 10 parts by mass, for example, 5 parts by mass, 6 parts by mass, 7 parts by mass, 8 parts by mass, or 9 parts by mass, and the amount of stearic acid used is 1 to 5 parts by mass, for example, 1.5 parts by mass, 2 parts by mass, or 3 parts by mass.

[0069] The protective wax migrates from the inside of the rubber to the surface, forming a wax film that isolates the rubber surface from the external environment. The protective wax is added optionally. When the raw materials of the rubber composition of the present invention include protective wax, the amount of protective wax used may be 1 to 5 parts by mass, for example, 1.5 parts by mass, 2 parts by mass, 3 parts by mass, or 4 parts by mass.

[0070] The activator plays a role in accelerating the vulcanization rate and improving the thermal conductivity, abrasion resistance, and tear strength of the rubber. In the raw materials of the rubber composition of the present invention, the amount of activator used may be 1 to 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, 8 parts by mass, or 9 parts by mass. In some preferred embodiments, the activator contains ZnO, or the activator is ZnO. In some preferred embodiments, in the raw materials of the rubber composition of the present invention, the amount of ZnO used is 3 to 8 parts by mass, for example, 4 parts by mass, 5 parts by mass, 6 parts by mass, or 7 parts by mass.

[0071] The accelerator is usually a vulcanization accelerator and may be one or more selected from sulfonamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiram-based vulcanization accelerators, thiourea-based vulcanization accelerators, guanidine-based vulcanization accelerators, dithiocarbamate-based vulcanization accelerators, aldehydeamine-based vulcanization accelerators, imidazoline-based vulcanization accelerators, and xanthate-based vulcanization accelerators. In the raw materials of the rubber composition of the present invention, the amount of accelerator used may be 0.2 to 2 parts by mass, for example, 0.5 parts by mass, 0.6 parts by mass, 0.8 parts by mass, 1 part by mass, or 1.5 parts by mass. In some preferred embodiments, the accelerator is accelerator NS (N-tert-butyl-2-benzothiazole sulfenamide).

[0072] Furthermore, 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) may be used in the rubber composition as needed. The amount of plasticizer used may be the amount normally used in the art.

[0073] In some preferred embodiments, the raw materials for the rubber composition of the present invention include, or consist of, 100 parts by mass of diene elastomer, 0.5 to 3 parts by mass of sulfur, 1 to 5 parts by mass of the compound of formula A or the degradation inhibitor composition of the present invention, 30 to 70 parts by mass of carbon black, 1 to 10 parts by mass of ZnO, 1 to 5 parts by mass of stearic acid, 1 to 10 parts by mass of aromatic oil, and 0.2 to 2 parts by mass of an accelerator, where the diene elastomer preferably includes natural rubber and butadiene rubber in a mass ratio of 1:2 to 2:1, and the accelerator is preferably accelerator NS.

[0074] The unvulcanized rubber of the present invention can be manufactured using conventional rubber mixing methods. For example, it can be manufactured using a two-stage mixing method. In the first stage, the raw materials of the rubber composition, excluding the crosslinking agent and accelerator, are mixed in a thermomechanical machine (e.g., an internal mixer), and the entire mixture is kneaded to a maximum temperature of 110°C to 190°C to obtain first-stage rubber. In the second stage, the mixture is kneaded in a thermomechanical machine (e.g., an open mill), the first-stage rubber is cooled, and then the first-stage rubber, crosslinking agent, and accelerator are kneaded together to a maximum temperature of 110°C or lower to obtain second-stage rubber, i.e., unvulcanized rubber.

[0075] Vulcanized rubber can be obtained by vulcanizing (solidifying) unvulcanized rubber. The vulcanization temperature is typically 130°C to 200°C, for example, 140°C to 160°C or 145±5°C. The vulcanization time depends on the vulcanization temperature, vulcanization system, and vulcanization kinetics, but is typically 15 to 60 minutes, for example, 20 to 40 minutes or 30±5 minutes.

[0076] The rubber composition of the present invention is used in rubber products, particularly tires. Compared to using conventional p-phenylenediamine-based degradation inhibitors, such as IPPD, using the compound of formula A or the degradation inhibitor composition of the present invention can significantly improve the moisture-heat degradation resistance and ozone degradation resistance of rubber products. Accordingly, the present invention further provides rubber products, which include the rubber composition according to this specification. Examples of rubber products include tires, rubber shoes, sealing materials, soundproofing panels, and vibration-damping pads. Preferably, the rubber product is a tire, such as sidewall rubber or tread rubber.

[0077] The present invention further provides applications of the compound of formula A or the degradation inhibitor composition of the present invention in improving the anti-moisture-heat degradation properties and / or anti-ozone degradation properties of a rubber composition, and methods for improving the anti-moisture-heat degradation properties and / or anti-ozone degradation properties of a rubber composition. Preferably, the applications or methods of the present invention include adding 1 to 5 parts by mass of the compound of formula A or the degradation inhibitor composition of the present invention to the raw materials of a rubber composition, with the mass of the diene elastomer contained in the rubber composition being 100 parts by mass. In the applications or methods of the present invention, the raw material components of the rubber composition are preferably as described in any one embodiment of this specification.

[0078] The present invention will be explained below with specific examples. These examples are for illustrative purposes only and are not intended to intentionally limit the scope of the present invention. Unless otherwise noted, the methods, reagents, and materials used in the examples are those well known in the art. All raw material compounds used in the examples are commercially available.

[0079] The sources of the raw materials used in the examples are as follows:

[0080] [Table 1] Manufacturing Example 1: Synthesis of the compound of formula I (1) Synthesis of the compound of formula III In a 500 mL four-necked flask, 181.5 g (1.5 mol) of 2,3-methylaniline and 100.1 g (0.275 mol) of a 25% aqueous solution of tetramethylammonium hydroxide (TMAOH) were added. The mixture was heated to 40-50°C while stirring, and dehydration was carried out by vacuum distillation to form a salt between TMAOH and 2,3-dimethylaniline. During this process, the color of the reaction solution gradually changed from yellow to dark red. The temperature was gradually raised to 72°C, and when the fraction reached approximately 50% of the amount of 25% tetramethylammonium hydroxide used as a catalyst, 31 g (0.25 mol) of nitrobenzene was added dropwise for about 3 hours while distilling under reduced pressure (-0.098 MPa) at 72°C. After the addition was complete, the mixture was kept warm for 1 hour, and the completion of the nitrobenzene reaction was confirmed by LC to obtain the condensate.

[0081] The above condensation solution was transferred to a 500 mL stainless steel reaction vessel, 50 g of deionized water and 40 g of skeletonized nickel as a catalyst were added, and after three substitutions with hydrogen gas, the temperature was raised and pressurized to 75°C and 1.5 MPa to carry out the reaction. LC confirmed that the reduction of nitro and nitroso compounds was completely finished. The reaction solution was filtered, washed with water, and phase separated. The organic phase was then removed by vacuum distillation (-0.1 MPa, 180°C) to obtain 45.7 g of the compound of formula III (yield approximately 85%), and GC measurement showed a content of >96%.

[0082] [ka] LC-MS (m / z): 212.30 (MH) + ).

[0083] (2) Synthesis of the compound of formula I 42.5 g (0.2 mol) of the compound of formula III, 60 g (0.6 mol) of 4-methyl-2-pentanone, and 0.5 g of Pt / C catalyst were placed in a reaction vessel. After three purgings with hydrogen gas, the temperature and pressure were increased to 100°C and 1.5 MPa to carry out the reaction. The reaction was stopped after confirming that the content of the compound of formula III was <0.1% by GC measurement. The reaction was cooled, the catalyst was removed by filtration, and light components were removed by vacuum distillation at -0.1 MPa and 180°C to obtain 57.6 g of the compound of formula I (yield approximately 97.2%), and the content was >96.8% by GC measurement. Properties: Reddish-brown liquid.

[0084] [ka] LC-MS (m / z): 296.46 (MH) + ).

[0085] Manufacturing Example 2: Synthesis of the compound of formula II (1) Synthesis of the compound of formula III The synthesis of the compound of formula III is the same as in Production Example 1.

[0086] (2) Synthesis of compound II 42.5 g (0.2 mol) of the compound of formula III, 100 g (1.38 mol) of 2-butanone, and 0.6 g of Pt / C catalyst were placed in a reaction vessel. After three purgings with hydrogen gas, the temperature was raised to 80°C and the reaction was carried out under pressure of 1.5 MPa. The reaction was stopped when the content of the compound of formula III was confirmed to be <0.1% by GC measurement. The temperature was lowered, the catalyst was removed by filtration, and light components were removed by vacuum distillation at -0.1 MPa and 150°C to obtain 52.2 g of the compound of formula II (yield approximately 97.4%), and the content was >95.8% by GC measurement. Properties: Reddish-brown solid.

[0087] [ka] LC-MS (m / z): 268.40 (MH) + ).

[0088] Manufacturing Example 3: Synthesis of the compound of formula IV (1) Synthesis of the compound of formula V In a 500 mL four-necked flask, 181.5 g (1.5 mol) of 3,4-methylaniline and 100.1 g (0.275 mol) of a 25% aqueous solution of tetramethylammonium hydroxide (TMAOH) were added. The mixture was heated to 40-50°C while stirring, and dehydration was carried out by vacuum distillation to form a salt between TMAOH and 2,3-dimethylaniline. During this process, the color of the reaction solution gradually changed from yellow to dark red. The temperature was gradually raised to 72°C, and when the fraction reached approximately 50% of the amount of 25% tetramethylammonium hydroxide used as a catalyst, 31 g (0.25 mol) of nitrobenzene was added dropwise for about 3 hours while distilling under reduced pressure (-0.098 MPa) at 72°C. After the addition was complete, the mixture was kept warm for 1 hour, and the completion of the nitrobenzene reaction was confirmed by LC to obtain the condensate.

[0089] The above condensation solution was transferred to a 500 mL stainless steel reaction vessel, 50 g of deionized water and 40 g of skeletonized nickel as a catalyst were added, and after three substitutions with hydrogen gas, the temperature was raised and pressurized to 75°C and 1.5 MPa to carry out the reaction. LC confirmed that the reduction of nitro and nitroso compounds was completely finished. The reaction solution was filtered, washed with water, and phase separated. The organic phase was then removed by vacuum distillation (-0.1 MPa, 180°C) to obtain 43.5 g of the compound of formula V (yield approximately 82%), and GC measurement showed a content of >95%.

[0090] [ka] LC-MS (m / z): 212.30 (MH) + ).

[0091] (2) Synthesis of the compound of formula IV 42.5 g (0.2 mol) of the compound of formula V, 162.4 g (2.8 mol) of acetone and 0.5 g of Pt / C catalyst were charged into a reaction kettle. After replacing with hydrogen gas three times, the temperature was raised to 70 °C and the pressure was increased to 1.5 MPa to carry out the reaction. After confirming by GC measurement that the content of the compound of formula V was <0.1%, the reaction was stopped. The temperature was lowered, and the catalyst was removed by filtration. Then, light components were removed by vacuum distillation at -0.1 MPa and 180 °C, and 49 g of the compound of formula IV (yield about 96.5%) was obtained. The content was >96.0% by GC measurement. Appearance: Reddish-brown solid.

[0092] [Chemical formula] LC-MS (m / z): 254.38 (M-H + )

[0093] Production Example 4: Synthesis of the compound of formula VI (1) Synthesis of the compound of formula VII 223.8 g (1.5 mol) of 2,3-diethylaniline and 100.1 g (0.275 mol) of an aqueous solution of 25% tetramethylammonium hydroxide (TMAOH) were charged into a 500 mL four-necked flask. While stirring, the temperature was raised to 40 - 50 °C, and dehydration was carried out by vacuum distillation to form a salt of TMAOH and 2,3-dimethylaniline. During this process, the color of the reaction solution gradually changed from yellow to dark red. The temperature was gradually raised to 72 °C. When the fraction reached about 50% of the amount of 25% tetramethylammonium hydroxide charged as the catalyst, 31 g (0.25 mol) of nitrobenzene was dropped dropwise over about 3 hours while vacuum distilling at 72 °C (-0.098 MPa). After the dropwise addition was completed, the mixture was kept warm for 1 hour. The completion of the reaction of nitrobenzene was confirmed by LC, and a condensation liquid was obtained.

[0094] The above condensation solution was transferred to a 500 mL stainless steel reaction vessel, 50 g of deionized water and 40 g of skeletonized nickel as a catalyst were added, and after three substitutions with hydrogen gas, the temperature was raised and pressurized to 75°C and 1.5 MPa to carry out the reaction. LC confirmed that the reduction of nitro and nitroso compounds was completely finished. The reaction solution was filtered, washed with water, and phase separated. The organic phase was then removed by vacuum distillation (-0.1 MPa, 180°C) to obtain 45.6 g of the compound of formula VII (yield approximately 75.9%), and GC measurement showed a content of >94.5%.

[0095] [ka] LC-MS (m / z): 240.35 (MH) + ).

[0096] (2) Synthesis of the compound of formula VI 43.2 g (0.18 mol) of the compound of formula VII, 155 g (1.8 mol) of 2-pentanone, and 0.5 g of Pt / C catalyst were placed in a reaction vessel. After three purgings with hydrogen gas, the temperature and pressure were increased to 100°C and 1.5 MPa to carry out the reaction. The reaction was stopped after confirming that the content of the compound of formula VII was <0.1% by GC measurement. The reaction was cooled, the catalyst was removed by filtration, and light components were removed by vacuum distillation at -0.1 MPa and 180°C to obtain 53.2 g of the compound of formula VI (yield approximately 95.3%), and the content was >96.8% by GC measurement. Properties: Reddish-brown liquid.

[0097] [ka] LC-MS (m / z): 310.49 (MH) + ).

[0098] Examples 1-6 and Comparative Examples 1-3 The rubber compositions of Examples 1-6 and Comparative Examples 1-3 were manufactured according to the formulations shown in Table 2, using the following process. (1) Natural rubber and butadiene rubber were added to an internal mixer, then carbon black, zinc oxide, stearic acid, aromatic oil and degradation inhibitors (degradation inhibitor IPPD, compound of formula I, compound of formula II, compound of formula IV, or compound of formula VI and / or degradation inhibitor STMQ), and the mixture was kneaded until the rubber mixture temperature reached 130°C, and the rubber was discharged to obtain a single-stage rubber. (2) After the first stage rubber was cooled, it was kneaded in an open mill, accelerator NS and sulfur were added, and the kneading continued until the rubber compound temperature reached 70°C, and then discharged to obtain the second stage rubber. (3) The two-stage rubber was vulcanized (145°C x 30 min) to obtain vulcanized rubber.

[0099] [Table 2] Test Example 1: High-Temperature Water Immersion Test The vulcanized rubbers of Examples 1-6 and Comparative Examples 1-3 were immersed in deionized water at 90°C for 8 hours. The immersion solution was then evaporated and dried, and the precipitated material was dissolved in acetone. Liquid chromatography analysis was performed to measure the content of the degradation inhibitor. The results are shown in Tables 3-5.

[0100] [Table 3]

[0101] [Table 4]

[0102] [Table 5] Test Example 2: Moisture Heat Degradation Test Based on GB / T 15905-1995, a test method for the moist heat degradation of vulcanized rubber, high-temperature and high-humidity degradation tests were performed on the vulcanized rubbers of Examples 1-6 and Comparative Examples 1-3. The test conditions were an aging chamber temperature of 70°C, relative humidity of 90%, and a degradation time of 14 days. The test standards for elongation at break and tensile strength were GB / T 528-2009, Measurement of tensile stress-strain characteristics of vulcanized rubber or thermoplastic rubber. The results are shown in Tables 6-8.

[0103] In this specification, the tensile product is given by tensile strength × elongation at break.

[0104] In this specification, the retention rate of physical properties = tensile strength after degradation / tensile strength before degradation

[0105] [Table 6]

[0106] [Table 7]

[0107] [Table 8] Test Example 3: Thermal Oxidation Degradation Test Based on GB / T 3512-2014, Hot Air Accelerated Degradation and Heat Resistance Test for Vulcanized Rubber or Thermoplastic Rubber, thermal oxidation degradation tests were performed on the vulcanized rubbers of Examples 1-6 and Comparative Examples 1-3, under test conditions of 100°C for 48 hours. The test standards for elongation at break and tensile strength were GB / T 528-2009, Measurement of Tensile Stress-Strain Characteristics of Vulcanized Rubber or Thermoplastic Rubber. The results are shown in Tables 9-11.

[0108] [Table 9]

[0109] [Table 10]

[0110] [Table 11] Test Example 4: Ozone Degradation Test Ozone degradation tests were conducted on the vulcanized rubbers of Examples 1-6 and Comparative Examples 1-3 in an ozone degradation test chamber according to the following standards. Dynamic ozone degradation: GB / T 13642-2015 Dynamic tensile test for anti-ozone cracking of vulcanized rubber or thermoplastic rubber. Static ozone degradation: GB / T 7762-2014 Static tensile test for anti-ozone cracking of vulcanized rubber or thermoplastic rubber. Crack level evaluation: GB / T 11206-2009 Rubber degradation test, surface crack method.

[0111] The specific test parameters were an ozone volume concentration of 50 pphm, a temperature of (40±2)°C, and a humidity of (50±5)%. In the static test, the crack condition of the sample was observed at regular intervals with a preliminary tensile strength of 20%. In the dynamic test, the crack condition of the sample was observed at regular intervals with a preliminary tensile strength of 10%, a dynamic tensile strength of 10%, and a frequency of 0.5 Hz. The results of the dynamic and static ozone degradation are shown in Tables 12 and 13, respectively. The meanings of 1c, 2c, 3c, and 4c in Tables 12 and 13 refer to the standard GB / T 11206-2019.

[0112] [Table 12]

[0113] [Table 13] The results in Table 3 show that after immersing the rubber formulations of Examples 1-4 in water at 90°C for 8 hours, the content of the degradation inhibitor in the precipitate was significantly lower than that of Comparative Example 1, and was less than 20% of that of Comparative Example 1. The results in Table 4 show that the content of the degradation inhibitor in the precipitate of the rubber formulation of Example 6 was significantly lower than that of Comparative Example 2. The results in Table 5 show that the content of the degradation inhibitor in the precipitate of the rubber formulation of Example 5 was significantly lower than that of Comparative Example 3. The above results indicate that the degradation inhibitors of Examples 1-6 are less likely to migrate from the rubber composition in high-temperature, high-humidity environments.

[0114] The results in Table 9 show that the rubber formulations of Examples 1-4 and Comparative Example 1 have the same level of property retention after hot air degradation at 100°C for 48 hours. This explains that the effect of compound I, compound II, compound IV, or compound VI on improving the anti-thermal oxidative degradation properties of rubber formulations is consistent with conventional p-phenylenediamine-based degradation inhibitors.

[0115] However, as shown in Table 6, after 14 days of degradation in a high-temperature, high-humidity environment (70°C, 90% relative humidity), the rubber compounds of Examples 1-4 retained approximately 80% of their physical properties, while the rubber compound of Comparative Example 1 retained only about 70%. As shown in Table 7, the rubber compound of Example 6 clearly retained more physical properties after degradation in high temperature and humidity than Comparative Example 2. As shown in Table 8, the rubber compound of Example 5 clearly retained more physical properties after degradation in high temperature and humidity than Comparative Example 3. The above results indicate that the degradation inhibitors in the rubber compounds of Examples 1-6 are not easily dissolved and extracted in water in a high-temperature, high-humidity environment, and can maintain a relatively high concentration in the rubber compounds, thus providing excellent protective effects and exhibiting excellent resistance to high temperature and high humidity degradation.

[0116] The results in Table 12 show that the rubber sheets of Examples 1-4 had a significantly lower crack density (grade B) initially under dynamic ozone degradation conditions than the rubber sheet of Comparative Example 1 (grade C). Regarding the crack width growth rate, the crack growth in the rubber sheets of Examples 1-4 was significantly slower than that of Comparative Example 1. After 144 hours of ozone degradation, the crack level of the rubber sheet of Comparative Example 1 was grade 4, while the crack levels of the rubber sheets of Examples 1-4 were all grade 3, demonstrating a clear improvement in properties. The crack level of Examples 1-4 reached grade 3 at the earliest after 120 hours of degradation, while Comparative Example 1 reached it in just 96 hours, representing an improvement of over 25%.

[0117] The results in Table 13 show that after 120 hours of static ozone degradation, the crack level of the rubber sheet in Comparative Example 1 was grade 4, while the crack level of the rubber sheets in Examples 1-4 was only grade 3, clearly demonstrating improved properties. Even after extending the degradation time to 144 hours, the crack level of the rubber sheets in Examples 1-4 remained at grade 3, indicating excellent durability.

[0118] According to the above results, the compound of formula A and the degradation inhibitor composition of the present invention can enable the rubber composition to have excellent high-temperature and high-humidity degradation resistance and ozone degradation resistance without fundamentally changing the initial physical properties or anti-thermal oxidative degradation characteristics.

Claims

1. A compound of formula A, 【Chemistry 1】 In equation A, R 1 , R 2 and R 3 Each is independently selected from C1 to C8 alkyl groups. The compound of formula A is R 1 and R 2 is a methyl group, R 3 A compound of formula A that does not contain a compound in which isopropyl group.

2. A compound of formula A according to claim 1, wherein in formula A, R 1 and R 2 are each independently selected from C1-C2 alkyl groups, and R 3 is selected from C3-C6 alkyl groups, preferably selected from C4-C6 alkyl groups, a compound of formula A.

3. A compound of formula A as described in claim 1, characterized in that the compound of formula A is a compound of formula I, a compound of formula II, or a compound of formula VI. 【Chemistry 2】

4. A degradation inhibitor composition comprising a degradation inhibitor STMQ and a compound of formula A, wherein the degradation inhibitor STMQ is a 2,2,4-trimethyl-1,2-dihydroquinoline polymer having a total mass of ≥80% of dimers, trimers, and tetramers of 2,2,4-trimethyl-1,2-dihydroquinoline, and the structural formula of the compound of formula A is, 【Transformation 3】 And in equation A, R 1 , R 2 and R 3 Each is independently selected from C1 to C8 alkyl groups. Preferably, in formula A, R 1 and R 2 Each is independently selected from C1-C2 alkyl groups, R 3 A degradation inhibitor composition characterized in that the alkyl group is selected from C3 to C6 alkyl groups, preferably from C4 to C6 alkyl groups.

5. A degradation inhibitor composition according to claim 4, characterized in that the compound of formula A is selected from the compound of formula I, the compound of formula II, the compound of formula IV, and the compound of formula VI. 【Chemistry 4】

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

1.

7. A rubber composition comprising 100 parts by mass of a diene elastomer and 1 to 5 parts by mass of a compound of formula A or a degradation inhibitor composition according to any one of claims 4 to 6, wherein the structural formula of the compound of formula A is 【Transformation 5】 And in equation A, R 1 , R 2 and R 3 Each is independently selected from C1 to C8 alkyl groups. Preferably, in formula A, R 1 and R 2 Each is independently selected from C1-C2 alkyl groups, R 3 The alkyl group is selected from C3 to C6 alkyl groups, preferably selected from C4 to C6 alkyl groups. Preferably, the compound of formula A is selected from the compounds of formula I, formula II, formula IV, and formula VI, characterized in that it is a rubber composition. 【Transformation 6】

8. The rubber composition according to claim 4, wherein the rubber composition has the following characteristics, namely, The diene elastomer comprises natural rubber and butadiene rubber, preferably with a mass ratio of 1:2 to 2:1 between the natural rubber and the butadiene rubber. The raw materials of the rubber composition further include 30 to 70 parts by mass of a reinforcing filler, preferably the reinforcing filler being carbon black. The raw materials of the rubber composition further contain 1 to 10 parts by mass of an activator, preferably the activator being zinc oxide. The raw materials of the rubber composition further include 2 to 15 parts by mass of a softening agent, preferably the softening agent includes an aromatic oil and stearic acid in a mass ratio of 1:1 to 5:

1. The raw materials for the rubber composition further contain 0.5 to 3 parts by mass of sulfur. The rubber composition is characterized in that the raw materials of the rubber composition further contain 0.2 to 2 parts by mass of an accelerator, wherein the accelerator is preferably selected from N-tert-butyl-2-benzothiazole sulfenamide, and the rubber composition is further characterized in that the accelerator is one or more selected from N-tert-butyl-2-benzothiazole sulfenamide.

9. A rubber product comprising the rubber composition described in claim 7 or 8, and preferably the rubber product being a tire.

10. An application of the compound of formula A or the degradation inhibitor composition described in any one of claims 4 to 6 in improving the anti-moisture-heat degradation properties and / or anti-ozone degradation properties of a rubber composition or rubber product, wherein the structural formula of the compound of formula A is: 【Transformation 7】 And in equation A, R 1 , R 2 and R 3 Each is independently selected from C1 to C8 alkyl groups. Preferably, in formula A, R 1 and R 2 Each is independently selected from C1-C2 alkyl groups, R 3 The alkyl group is selected from C3 to C6 alkyl groups, preferably selected from C4 to C6 alkyl groups. Preferably, the compound of formula A is selected from the compounds of formula I, formula II, formula IV, and formula VI, for the application. 【Transformation 8】

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