A sidewall rubber composition for electric buses, a mixing method, and a tire

Abstract

The present invention belongs to the technical field of rubber composite materials, and particularly relates to a sidewall rubber composition for electric buses, a mixing method and a tire. A polar rubber premix is prepared by blending a polar rubber with an antioxidant, and the mass ratio of the polar rubber to the antioxidant is 3:1 to 1:3. Further, the present invention also discloses a sidewall rubber composition for electric buses. In the present invention, the polar rubber and the antioxidant also carrying polar groups are pre-blended to achieve preliminary dispersion of the antioxidant, and then the premix is mixed with raw rubber and other compounding agents. This process improves the compatibility of the antioxidant in the rubber composition, slows down the precipitation of the antioxidant, and the appearance of the sidewall of the finished tire is good.

Description

Technical Field

[0001] The present invention belongs to the technical field of rubber composites, and particularly relates to a sidewall rubber composition for electric buses, a mixing method, and a tire. Background Art

[0002] The rapid development of urban public transportation has put forward more and higher requirements for the tires of urban bus vehicles. The intended use of special bus tires is for bus vehicles that frequently stop in the city. Since there is space for passengers to stand on bus vehicles, special bus tires need to have a certain overloading performance. In addition, special bus tires have put forward higher requirements in terms of wear resistance, braking and driving performance, retreading rate, low noise, comfort, etc. For the sidewall of the bus tire, due to the large torque of the bus tire and the large tangential force acting on the sidewall, fatigue marks and sidewall cracks are likely to occur on the sidewall. Figure 1 There is a problem of circumferential fatigue marks in the sidewall part of the bus tire. Figure 2 There is a common phenomenon of blueing on the sidewall appearance caused by the precipitation of anti-aging agents. The tire industry has been researching the discoloration of the sidewall and trying to replace the traditional polluting anti-aging agent 4010NA with a non-polluting anti-aging agent (such as 4020 used by most tire factories now). Even though there is some improvement, with the extension of the storage period, the sidewall surface will still show brown. In addition, aromatic oil has been widely used in tire formulations because it is beneficial to improving tire performance and has a relatively low price. However, the unsaturation of its main component aromatic hydrocarbons is relatively high, and it is relatively easy to show oxidation discoloration, which is also one of the factors leading to tire discoloration. There is a superimposed effect between anti-aging agents and aromatic oil in the process of causing the discoloration of the rubber compound. Conventional anti-aging agents and aromatic oil both have the problem of blooming when added in excess to reach the supersaturated state, and are extremely prone to discoloration under the conditions of heat, oxygen, and light. Figure 3 There is the phenomenon of sidewall cracks.

[0003] In the prior art, for example, the Chinese invention patent application (publication number: CN113372623A, publication date: September 10, 2021) applied by the applicant discloses a rubber composition. Based on 100 parts by weight of the rubber component, this composition includes 2.0 - 12.0 parts by weight of non-oil plasticizer, 3.0 - 10.0 parts of nano-porous inorganic material, and 1.0 - 5.0 parts of microcrystalline wax; the present application develops a sidewall rubber composition with excellent appearance. Using this rubber composition to produce the sidewall and prepare the tire, while ensuring the flexing and aging resistance performance of the sidewall, there is no blooming phenomenon after parking, and the appearance is excellent.

[0004] The applicant applied for a Chinese invention patent (Publication No.: CN114989507A, Publication Date: September 2, 2022), which disclosed a sidewall rubber composition for high-quality appearance tires and its preparation method. Based on 100 parts by weight of rubber, the rubber composition is prepared by mixing raw materials including the following components: 30-50 parts of natural rubber, 50-70 parts of polybutadiene rubber, 5-35 parts of high-molecular-weight recycled rubber, 30-50 parts of carbon black, 2-8 parts of softening oil, and 1-3 parts of resin; the high-molecular-weight recycled rubber compound is prepared by pretreating waste rubber powder, softening agent, and activator in a blender and then performing desulfurization reaction in a screw extruder. The molecular weight Mn of the high-molecular-weight recycled rubber compound belongs to 12000-18000 g / mol, and the sol content belongs to 30%-50%. Applying the low-temperature desulfurized high-molecular-weight recycled rubber to the sidewall formula can ensure various physical properties, increase the blackness of the rubber compound, reduce the migration of small molecules, improve the spray resistance of the sidewall formula, and improve the appearance quality. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention discloses a sidewall composition for electric buses. First, the polar rubber and the antioxidant with the same polar group are pre-blended to achieve the preliminary dispersion of the antioxidant, and then the pre-mixture is mixed with raw rubber and other compounding agents. This process improves the compatibility of the antioxidant in the rubber composition, slows down the precipitation of the antioxidant, and the appearance of the sidewall of the finished tire is good.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A polar rubber pre-mixture, which is prepared by blending polar rubber and an antioxidant, and the mass ratio of the polar rubber to the antioxidant is 3:1 to 1:3.

[0008] Preferably, the polar rubber is one or more mixtures of chloroprene rubber, nitrile rubber, hydrogenated nitrile rubber, carboxy nitrile rubber, fluororubber, polyurethane rubber, polyether rubber, polysulfide rubber, acrylate rubber, chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber.

[0009] Preferably, the antioxidant is one or more mixtures of compounds of amines, phenols, imidazoles, metal carbamates, and waxes.

[0010] Furthermore, the present invention also discloses a preparation method of the above-mentioned polar rubber pre-mixture. The method uses a Banbury mixer. After putting the polar rubber into the mixing chamber, the top plug is pressed down. After plasticizing for 1 minute, the top plug is lifted up, and then the antioxidant is added and the top plug is pressed down. After mixing for 3-7 minutes, the top plug is lifted up, and the rubber compound is unloaded to obtain a polar rubber pre-mixture.

[0011] Furthermore, the present invention also discloses the application of the polar rubber premix in completely replacing the anti-aging agent in tire preparation.

[0012] Preferably, for the tire rubber composition, based on 100 parts by rubber component, 5.0 to 25 parts of the polar rubber premix are used to replace the anti-aging agent.

[0013] Preferably, the raw rubber used is a diene rubber. Examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), butyl rubber (IIR), ethylene propylene diene monomer rubber (EPDM), acrylonitrile-butadiene rubber (NBR), styrene-isoprene-butadiene rubber (SIBR), or chloroprene rubber (CR), etc. Preferably, it contains one or more rubber components among them.

[0014] Preferably, the reinforcing filler is selected from one or more of carbon black and silica.

[0015] Preferably, the BET specific surface area of the carbon black particles is preferably 20 to 160 m 2 / g, more preferably 40 to 130 m 2 / g, and further preferably 50 to 120 m 2 / g; the BET specific surface area of the carbon black particles can be measured in accordance with JIS Z8830. The so-called BET method is a method of adsorbing nitrogen with a known occupied area on the surface of the sample powder particles and obtaining the specific surface area of the sample powder particles based on the adsorption amount. The specific surface area obtained by this method is called the "BET specific surface area".

[0016] As the average secondary particle diameter of the carbon black particles, from the viewpoint of further improving the dispersibility, mechanical strength and hardness, it is preferably 0.05 to 3 μm, more preferably 0.1 to 1.0 μm, and further preferably 0.2 to 0.9 μm. The average secondary particle diameter of the carbon black particles can be measured by the laser diffraction / scattering method, which is the particle diameter (volume-based cumulative 50% particle diameter), i.e., D50 (median diameter) at the cumulative 50% in the particle size distribution measured by the laser diffraction / scattering method. The volume-based cumulative 50% particle diameter (D50) is to obtain the particle size distribution based on the volume. In the cumulative curve with the total volume set to 100%, the particle number is counted from the side with smaller particle size, and the particle diameter at the point where the cumulative value reaches 50% is measured.

[0017] Examples of the carbon black that constitutes the above carbon black particles include furnace black, thermal black, acetylene black, Ketjen black, etc. Among these, from the viewpoint of further improving the mechanical strength of the rubber composition, furnace black is preferred. They can be used alone or in combination of two or more. In addition, in order to further improve the affinity with the rubber component, the surface can be subjected to an organic treatment. Preferably, the carbon black in the present invention is one of N134, N220, N234, and N375.

[0018] Regarding the compounding amount when compounding carbon black particles in the rubber composition of the present invention, relative to 100 parts by mass of the rubber component, it is preferably 2 to 50 parts by mass, more preferably 3 to 30 parts by mass, and still more preferably 10 to 20 parts by mass.

[0019] The BET specific surface area of the silica in the rubber composition of the present invention is 50 to 250 m 2 / g, preferably 80 to 210 m 2 / g, more preferably 100 to 190 m 2 / g. By adjusting the BET specific surface area within such a range, more excellent dispersibility, wet skid resistance, and abrasion resistance can be obtained. The BET specific surface area of the silica can be measured in accordance with JIS Z8830. The BET method is a method of adsorbing nitrogen with a known occupied area on the surface of the sample powder particles and obtaining the specific surface area of the sample powder particles based on the adsorption amount. The specific surface area obtained by this method is called the "BET specific surface area".

[0020] The silica in the rubber composition of the present invention means a silica silicate-based filler, and not only represents silica in the narrow sense, and can be appropriately selected and used from existing materials used as reinforcing fillers. For example, wet silica (hydrous silicic acid), dry silica (anhydrous silica), etc. can be cited. Among these, from the viewpoint of further improving processability, wet skid resistance, and abrasion resistance, wet silica is preferred. They can be used alone or in combination of two or more. In addition, in order to further improve the affinity with the rubber component, it is preferred to form a treatment layer formed by a surface treatment agent on the surface.

[0021] The silica in the rubber composition constituting the present invention means a silica silicate-based filler, and not only represents silica in the narrow sense, and can be appropriately selected and used from existing materials used as reinforcing fillers. For example, wet silica (hydrous silicic acid), dry silica (anhydrous silica), etc. can be cited. Among these, from the viewpoint of further improving processability, wet skid resistance, and abrasion resistance, wet silica is preferred. They can be used alone or in combination of two or more. In addition, in order to further improve the affinity with the rubber component, it is preferred to form a treatment layer formed by a surface treatment agent on the surface.

[0022] From the viewpoint of further improving the processability, wet skid resistance, and abrasion resistance of the obtained rubber composition, the average secondary particle diameter of the silica is preferably 0.04 to 3 μm, more preferably 0.1 to 1 μm, and further preferably 0.2 to 0.7 μm. The average secondary particle diameter of the silica can be measured by the laser diffraction / scattering method, and is the particle diameter (volume-based cumulative 50% diameter), that is, D50 (median diameter) at the cumulative 50% in the particle size distribution measured by the laser diffraction / scattering method. The volume-based cumulative 50% diameter (D50) is to obtain the particle size distribution based on the volume, and in the cumulative curve with the total volume set to 100%, the number of particles is counted from the side with a small particle size, and the particle diameter at the point where the cumulative value reaches 50% is obtained.

[0023] The compounding amount of the silica in the rubber composition of the present invention is preferably 20 to 120 parts by mass, more preferably 25 to 100 parts by mass, and further preferably 30 to 90 parts by mass with respect to 100 parts by mass of the rubber component. By setting it within this range, more excellent wet skid resistance and abrasion resistance can be obtained.

[0024] In the rubber composition of the present invention, in addition to the above-mentioned components, compounding agents commonly used in the rubber field such as silane coupling agents, vulcanizing agents, vulcanization accelerator aids, softeners, plasticizers, anti-scorching agents, anti-ozone agents, foaming agents, and vulcanization retarders can be appropriately compounded.

[0025] Examples of the silane coupling agent can include sulfide-based, polysulfide-based, thioester-based, thiol-based, olefin-based, epoxy-based, amino-based, alkyl-based, etc. silane coupling agents, and they can be used alone or in combination of two or more. Among these, sulfide-based silane coupling agents and amino-based silane coupling agents are preferred.

[0026] Examples of silane coupling agents of the sulfide type include: bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(3-methyldimethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(3-methyldimethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-trimethoxysilylpropyl)trisulfide, bis(3-methyldimethoxysilylpropyl)trisulfide, bis(2-triethoxysilylethyl)trisulfide, bis(3-monoethoxydimethylsilylpropyl)tetrasulfide, bis(3-monoethoxydimethylsilylpropyl)trisulfide, bis(3-monoethoxydimethylsilylpropyl)disulfide, bis(3-monomethoxydimethylsilylpropyl)tetrasulfide, bis(3-monomethoxydimethylsilylpropyl)trisulfide, bis(3-monomethoxydimethylsilylpropyl)disulfide, bis(2-monoethoxydimethylsilylethyl)tetrasulfide, bis(2-monoethoxydimethylsilylethyl)trisulfide, bis(2-monoethoxydimethylsilylethyl)disulfide, etc. Among these, bis(3-triethoxysilylpropyl)tetrasulfide is preferred.

[0027] Examples of silane coupling agents of the thioester type include: 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3-lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, 2-lauroylthioethyltrimethoxysilane, etc.

[0028] Examples of silane coupling agents of the thiol type include: 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, etc.

[0029] As an olefin-based silane coupling agent, examples include dimethoxymethylvinylsilane, vinyltrimethoxysilane, dimethylethoxyvinylsilane, diethoxymethylvinylsilane, triethoxyvinylsilane, vinyltris(2-methoxyethoxy)silane, allyltrimethoxysilane, allyltriethoxysilane, p-styryltrimethoxysilane, 3-(methoxydimethoxydimethylsilyl)propyl acrylate, 3-(trimethoxysilyl)propyl acrylate, 3-[dimethoxy(methyl)silyl]propyl methacrylate, 3-(trimethoxysilyl)propyl methacrylate, 3-[dimethoxy(methyl)silyl]propyl methacrylate, 3-(triethoxysilyl)propyl methacrylate, 3-[tris(trimethylsiloxy)silyl]propyl methacrylate, etc.

[0030] As an epoxy-based silane coupling agent, examples include 3-glycidoxypropyl(dimethoxy)methylsilane, 3-glycidoxypropyltrimethoxysilane, diethoxy(3-glycidoxypropyl)methylsilane, triethoxy(3-glycidoxypropyl)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, etc.

[0031] As an amino-based silane coupling agent, examples include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-ethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane, etc. Among these, 3-aminopropyltriethoxysilane is preferred.

[0032] As an alkyl-based silane coupling agent, examples include methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, cyclohexylmethyldimethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxysilane, etc.

[0033] As a vulcanizing agent, it can be combined with organic peroxides or sulfur-based vulcanizing agents. As the organic peroxides, for example, benzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, tert-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hex-3-yne, 1,3-bis(tert-butylperoxyisopropyl)benzene, di-tert-butyl peroxide diisopropylbenzene, tert-butyl peroxide benzene, 2,4-dichlorobenzoyl peroxide, 1,1-di-tert-butylperoxy-3,3,5-trimethylsiloxane, n-butyl 4,4-di-tert-butylperoxypentanoate, etc. can be combined. Among these organic peroxides, dicumyl peroxide, tert-butyl peroxide benzene, and di-tert-butyl peroxide diisopropylbenzene are preferred. In addition, as the sulfur-based vulcanizing agents, for example, sulfur, morpholine disulfide, etc. can be combined. Among these sulfur-based vulcanizing agents, sulfur is preferred.

[0034] As a vulcanization accelerator, it can be combined with sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamate-based, aldehyde-amine-based or aldehyde-ammonia-based, etc.

[0035] As the sulfenamide-based, for example, sulfenamide-based compounds such as CBS (N-cyclohexyl-2-benzothiazolylsulfenamide), TBBS (N-tert-butyl-2-benzothiazolylsulfenamide), N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N,N-diisopropyl-2-benzothiazolesulfenamide, etc. can be cited.

[0036] As the thiazole-based, for example, MBT (2-mercaptobenzothiazole), MBTS (dibenzothiazolyl disulfide), sodium salt, zinc salt, copper salt, cyclohexylamine salt of 2-mercaptobenzothiazole, 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, etc. can be cited.

[0037] As the thiuram-based, for example, TMTD (tetramethylthiuram disulfide), tetraethylthiuram disulfide, tetramethylthiuram monosulfide, dipentamethylenethiuram disulfide, dipentamethylenethiuram monosulfide, dipentamethylenethiuram tetrasulfide, dipentamethylenethiuram hexasulfide, tetrabutylthiuram disulfide, pentamethylenethiuram tetrasulfide, etc. can be cited.

[0038] As the thiourea-based, for example, thiourea compounds such as thiocarbamide, diethylthiourea, dibutylthiourea, trimethylthiourea, di-o-tolylthiourea, etc. can be cited.

[0039] As guanidine compounds, guanidine compounds such as diphenylguanidine, di-o-tolylguanidine, triphenylguanidine, o-tolylbiguanide, and diphenylguanidine phthalate can be cited, for example.

[0040] As dithiocarbamate compounds, for example, zinc ethylphenyl dithiocarbamate, zinc butylphenyl dithiocarbamate, sodium dimethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc dipentyldithiocarbamate, zinc dipropyldithiocarbamate, the coordination salt of zinc pentamethylenedithiocarbamate and piperidine, zinc hexadecylisopropyl dithiocarbamate, zinc octadecylisopropyl dithiocarbamate, zinc dibenzyldithiocarbamate, sodium diethyldithiocarbamate, piperidine pentamethylenedithiocarbamate, selenium dimethyldithiocarbamate, tellurium diethyldithiocarbamate, cadmium dipentyldithiocarbamate and other dithiocarbamate compounds can be cited.

[0041] As aldehyde-amine or aldehyde-ammonia compounds, for example, acetaldehyde-aniline reactants, butyraldehyde-aniline condensates, hexamethylenetetramine, acetaldehyde-ammonia reactants, etc. can be cited.

[0042] As softeners, petroleum-based softeners such as process oils, lubricating oils, paraffin wax, liquid paraffin, petroleum pitch, petrolatum, etc., fatty oil-based softeners such as castor oil, linseed oil, rapeseed oil, coconut oil, etc.; waxes such as tall oil, substitution ointment, beeswax, carnauba wax, lanolin, etc.; fatty acids such as linoleic acid, palmitic acid, stearic acid, lauric acid, etc. can be compounded. By compounding softeners, the kneading processability can be further improved.

[0043] As plasticizers, 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), DLP (dilauryl phthalate), DCHP (dicyclohexyl phthalate), hydrogen phthalic anhydride ester, DOZ (di-2-ethylhexyl azelate), DBS (dibutyl sebacate), DOS (dioctyl sebacate), triethyl acetylcitrate, tributyl acetylcitrate, DBM (dibutyl maleate), DOM (2-ethylhexyl maleate), DBF (dibutyl fumarate), etc. can be compounded.

[0044] As anti-scorch agents, organic acids such as phthalic anhydride, salicylic acid, benzoic acid, etc.; nitroso compounds such as N-nitrosodiphenylamine, N-cyclohexylthiophthalimide, etc. can be compounded.

[0045] Furthermore, the present invention also discloses a sidewall rubber composition for electric buses. The tire composition is prepared by mixing the following raw materials based on 100 parts of rubber components:

[0046] Raw rubber: 80 - 97 parts

[0047] Polar rubber premix: 10 - 21 parts

[0048] Carbon black: 37 - 52 parts

[0049] Protective wax: 1.5 - 5 parts

[0050] Zinc oxide: 2.5 - 3.5 parts

[0051] Stearic acid: 1.0 - 3.0 parts

[0052] Zinc alkyl thiophosphate: 0.3 - 1.2 parts

[0053] Vulcanizing agent: 2.0 - 4.0 parts

[0054] Tear - resistant resin: 1.0 - 3.0 parts;

[0055] The polar rubber premix is the described polar rubber premix.

[0056] Preferably, the raw rubber is one or more of natural rubber, cis - 1,4 - polybutadiene rubber, and styrene - butadiene rubber; more preferably, it is 50 - 70 parts of natural rubber and 30 - 50 parts of cis - 1,4 - polybutadiene rubber.

[0057] Preferably, the tear - resistant resin is one or more of modified cyclopentadiene and dicyclopentadiene resin, α - styrenyl resin, rosin - modified C9 resin, rosin derivatives, and C9 resin - modified phenol - formaldehyde resin.

[0058] Preferably, the carbon black has a particle size of 20 - 30 nm, an iodine adsorption value of 82 - 121 g / kg, an oil absorption value of 72 - 119×10 - 5 m3 / kg, and a coloring strength of 103 - 124%.

[0059] Preferably, the vulcanizing agent includes sulfur, sulfur donors, functional resin cross - linkers, sulfenamide accelerators, thiazole accelerators, thiuram accelerators, thiourea accelerators, guanidine accelerators, dithiocarbamate accelerators, etc.

[0060] Preferably, the zinc alkyl thiophosphate is one of zinc dialkyldithiophosphate, bis(iso - butyl) - o - pentyl bis(dithiophosphate) zinc, bis[O - (2 - ethylhexyl) - O - (2 - methylpropyl) dithiophosphate zinc, and zinc O,O - dibutyldithiophosphate.

[0061] Furthermore, the present invention also discloses a mixing method for a sidewall rubber composition for electric buses, and the method comprises the following steps:

[0062] 1) First-stage mixing: Put raw rubber, carbon black, zinc oxide, stearic acid, protective wax, and anti-tear resin into a mixer and mix for 30 - 50 seconds, mix at a rotational speed of 37 - 55 rpm, perform lifting and pressing of the material every 20 - 35 seconds. When the temperature of the rubber compound reaches 145°C - 165°C, discharge the rubber and cut it into sheets. After placing it at room temperature for cooling for 8 - 12 hours, a first-stage masterbatch is obtained, and then it is subjected to second-stage mixing;

[0063] 2) Second-stage mixing: Put the first-stage masterbatch obtained in step 1) and a polar rubber premix into a mixer, and mix at a rotational speed of 25 - 40 rpm. Perform lifting and pressing of the material every 20 - 35 seconds. When the temperature of the rubber compound reaches 135 - 150°C, discharge the rubber and cut it into sheets. After placing it at room temperature for cooling for 8 - 12 hours, a second-stage masterbatch is obtained, and then it is subjected to final mixing;

[0064] 3) Final mixing: Put the second-stage masterbatch obtained in step 2), a vulcanizing agent, and zinc alkyl thiophosphate into a mixer, and mix at a rotational speed of 20 - 30 rpm. Perform lifting and pressing of the material at intervals of 20 - 35 seconds, 20 - 30 seconds, and 15 - 25 seconds in sequence. When the temperature of the rubber compound reaches 100 - 120°C, discharge the rubber and cut it into sheets. After placing it for cooling, the sidewall rubber composition is obtained.

[0065] Furthermore, the present invention also discloses a tire for electric buses, characterized in that the sidewall of the tire is prepared by vulcanizing the above-mentioned sidewall rubber composition.

[0066] Due to the adoption of the above technical solution, the present invention first preliminarily disperses the antioxidant by pre-blending the polar rubber with the antioxidant having the same polar group, and then kneads the pre-blend with the raw rubber and other compounding agents. This process improves the compatibility of the antioxidant in the rubber composition, slows down the precipitation of the antioxidant, and the appearance of the finished tire sidewall is good. Further, the present invention uses carbon black filler with small particle size and tear-resistant resin. The carbon black with small particle size has good reinforcing effect, high coloring strength, high blackness of the sidewall, and high tear strength. The use of the tear-resistant resin can improve the tear strength and viscosity of the rubber compound, improve the processing performance, and has good compatibility with the rubber. Its action mechanism is that the main chain of the resin provides a highly rigid structure, and at the same time, the side chain provides substituents with good compatibility with the rubber. This rigid structure can dissipate energy when the crack propagates. The tip crack expands due to the energy, and by adding this material that can dissipate energy and passivating the crack tip, the crack propagation can be hindered. In addition, the present invention controls the heat generation performance of the rubber compound by regulating the vulcanization system with zinc alkylthiophosphate salt for the crosslinked network structure and bond type, and greatly reduces the heat generation on the basis of ensuring the mechanical strength. The sidewall rubber prepared by the above three technical means has good dynamic performance, flex fatigue resistance and tear resistance, effectively avoids the appearance of sidewall turtle cracks, and meets the safety, comfort and other special requirements for urban bus tires. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a photo of the fatigue marks in a circumferential circle at the sidewall part of an existing bus tire.

[0068] Figure 2 It is a photo of the blueing phenomenon commonly seen in the appearance of the sidewall of an existing bus tire due to the precipitation of the antioxidant.

[0069] Figure 3 It is a photo of the sidewall crack phenomenon of an existing bus tire.

[0070] Figure 4 It is a comparison diagram of the sidewall product photos of Application Example 2 and Comparative Example 7. DETAILED DESCRIPTION OF THE INVENTION

[0071] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Given the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0072] The raw material sources of the present invention are as follows:

[0073] Carbon black, a product of Cabot

[0074] Zinc oxide, a product of Shijiazhuang Zhiyi Zinc Industry,

[0075] Stearic acid, a product of Hangzhou Oil Chemical Industry,

[0076] Antioxidant 4020, a product of ShengAo Chemical Technology,

[0077] Antioxidant RD, a product of Shandong Shangshun Chemical Industry,

[0078] Antioxidant DTPD, a product of Yixing Jujinxin Chemical Industry,

[0079] Protective wax, a product of Shandong Yanggu Huatai,

[0080] Tear-resistant resin, a product of Shanghai Qixiang Chemical Industry;

[0081] All other materials not specified are conventional materials for tire preparation.

[0082] Example 1

[0083] Antioxidant 4020: 3 parts, Antioxidant RD: 1 part, Antioxidant DTPD: 1 part, Nitrile rubber: 5 parts, the ratio of nitrile rubber to antioxidant is 1:1. Using a small internal mixer, after putting the nitrile rubber into the mixing chamber, press the upper ram, plastify for 1 minute, then raise the upper ram, put in all the antioxidants and press the upper ram again, mix for 4 minutes, then raise the upper ram, unload the rubber compound to obtain the polar rubber premix A.

[0084] Example 2

[0085] Antioxidant 4020: 3 parts, Antioxidant RD: 1 part, Antioxidant DTPD: 1 part, Chlorosulfonated polyethylene rubber: 10 parts, the ratio of chlorosulfonated polyethylene rubber to antioxidant is 2:1. Using a small internal mixer, after putting the chlorosulfonated polyethylene rubber into the mixing chamber, press the upper ram, plastify for 1 minute, then raise the upper ram, put in all the antioxidants and press the upper ram again, mix for 7 minutes, then raise the upper ram, unload the rubber compound to obtain the polar rubber premix B.

[0086] Example 3

[0087] Antioxidant 4020: 3 parts, Antioxidant RD: 1 part, Antioxidant DTPD: 1 part, Chloroprene rubber: 15 parts, the ratio of chloroprene rubber to antioxidant is 3:1. Using a small internal mixer, after putting the chloroprene rubber into the mixing chamber, press the upper ram, plastify for 1 minute, then raise the upper ram, put in all the antioxidants and press the upper ram again, mix for 7 minutes, then raise the upper ram, unload the rubber compound to obtain the polar rubber premix C.

[0088] Example 4

[0089] Antioxidant 4020: 3 parts, antioxidant RD: 1 part, antioxidant DTPD: 1 part, natural rubber: 15 parts. The ratio of natural rubber to antioxidants is 3:1. Using a small internal mixer, after putting the natural rubber into the mixing chamber, press the top plug. After plasticizing for 1 minute, raise the top plug, then add all the antioxidants and press the top plug. After mixing for 7 minutes, raise the top plug and unload the rubber compound to obtain rubber premix D.

[0090] The specific formulations of the application examples and comparative examples of the present invention are shown in Table 1.

[0091] Table 1 Formulation

[0092] Application Example 1 Application Example 2 Application Example 3 Application Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Natural Rubber 55 50 50 50 60 55 55 55 45 Butadiene Rubber 40 40 40 35 40 40 40 40 40 Carbon Black N220 45 45 45 45 45 45 45 45 Carbon Black N330 45 Tear Resistance Resin 2 2 2 2 2 2 2 2 Phenolic Resin 2 Zinc Alkylthiophosphate 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Vulcanizing Agent 2.7 2.7 2.7 2.7 4 2.7 2.7 2.7 2.7 Polar Mixture A 10 10 10 Polar Mixture B 15 15 Polar Mixture C 20 Rubber Premix D 20 Antioxidant 5 5 Nitrile Rubber 5 Protective Wax 2 2 2 2 2 2 2 2 2

[0093] The mixing methods of the application examples and comparative examples are as follows. If there is no corresponding raw material in the formulation, do not add the corresponding raw material:

[0094] (1) First-stage mixing: Put the rubber, carbon black, zinc oxide, stearic acid and tear-resistant resin into the internal mixer and mix for 40 seconds. Mix at a rotational speed of 40 rpm, and perform lifting and pressing of the ram every 25 seconds. When the temperature of the rubber compound reaches 155 °C, discharge the rubber and cut it into sheets. After cooling at room temperature for 10 hours, obtain the first-stage masterbatch, and then perform second-stage mixing on it;

[0095] (2) Second-stage mixing: Put the first-stage masterbatch obtained in step (1) and the polar rubber premix into the internal mixer, and mix at a rotational speed of 30 rpm. Perform lifting and pressing of the ram every 20 seconds. When the temperature of the rubber compound reaches 145 °C, discharge the rubber and cut it into sheets. After cooling at room temperature for 8 hours, obtain the second-stage masterbatch, and then perform final mixing on it;

[0096] (3) Final mixing: Put the second-stage masterbatch obtained in step (2), vulcanizing agent, and zinc alkyl thiophosphate into the internal mixer, and mix at a rotational speed of 25 rpm. Perform lifting and pressing of the ram at intervals of 25 seconds, 30 seconds, and 20 seconds in sequence. When the temperature of the rubber compound reaches 110 °C, discharge the rubber and cut it into sheets. After cooling, the sidewall rubber composition is obtained.

[0097] Table 2 Performance Test

[0098]

[0099] Figure 4It is from the appearance of the test pieces after vulcanization of the sidewall compositions in Application Example 2 and Comparative Example 7. From the appearance of the test pieces, it can be seen that when using carbon black with a small particle size, the sidewall appearance is relatively black and shiny; in Application Example 1 and Comparative Example 2, a tear-resistant resin and a phenolic resin were respectively selected. The tear resistance of Application Example 1 was significantly improved. The main mechanism is that the main chain of the tear-resistant resin provides a highly rigid structure, and at the same time, substituents with good compatibility with rubber are provided on the side chain. This rigid structure can dissipate energy when the crack propagates. The tip crack propagates due to having energy, and by adding this material that can dissipate energy and passivating the crack tip, the crack propagation can be hindered. Therefore, compared with only improving the self-adhesion of the rubber compound, both have crack propagation resistance compared with the phenolic resin that improves the physical and mechanical properties and heat aging properties of the rubber compound; in Comparative Example 3 and Comparative Example 5, in Comparative Example 3, the problem of deteriorated cracks caused by adding polar rubber was eliminated by adding zinc alkylthiophosphate. In Application Example 1 and Comparative Example 2, Application Example 1 first blends the polar rubber and the antioxidant to form a premix, and then adds it in the second stage of mixing. Comparative Example 2 directly adds the polar rubber and the antioxidant into the second stage by the conventional process without pre-mixing. The mechanical properties and tear strength of Comparative Example 2 decreased significantly, and the blackness decreased. Through comparison, the flexing performance of Application Example 1 is the best. The appearance of the sidewall of the finished tire does not change color after being stored for half a year, while the sidewall of Comparative Example 5 began to show the phenomenon of antioxidant precipitation after 3 months, and the sidewall of Comparative Example 4 began to show the phenomenon of antioxidant precipitation and the sidewall turning blue after half a year.

[0100] In Application Examples 1, 2, and 3, different methods of blending polar rubber and antioxidant were adopted, and the result was that the effect of preventing antioxidant precipitation could be achieved. While in Comparative Example 5, natural rubber and antioxidant were blended, and there was no such effect, and the antioxidant began to precipitate after 3 months.

[0101] From Application Examples 2, 3, and 4, it can be known that changing different raw rubber ratios and selecting different carbon blacks can solve the problem of antioxidant precipitation; in Application Example 2, N220 was selected, and in Application Example 3, N330 was selected. It can be seen that since the particle size of N220 is smaller, the blackness of Application Example 2 is higher.

[0102] The above is the description of the embodiments of the present invention. Through the above description of the disclosed embodiments, those skilled in the art can implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel points disclosed herein.

Claims

1. A sidewall rubber composition for electric buses, characterized in that the tire composition is prepared by mixing the following raw materials based on 100 parts by weight of rubber components: Raw rubber 80 - 97 parts Polar rubber premix 10 - 21 parts Carbon black 37 - 52 parts Protective wax 1.5 - 5 parts Zinc oxide 2.5 - 3.5 parts Stearic acid 1.0 - 3.0 parts Zinc alkyl thiophosphate 0.3 - 1.2 parts Vulcanizing agent 2.0 - 4.0 parts Anti - tear resin 1.0 - 3.0 parts; The polar rubber premix is prepared by blending polar rubber and antioxidant, and the mass ratio of the polar rubber to the antioxidant is 3:1 - 1:3; the polar rubber is one or a mixture of chloroprene rubber, nitrile rubber, hydrogenated nitrile rubber, carboxyl nitrile rubber, fluororubber, polyurethane rubber, polyether rubber, polysulfide rubber, acrylate rubber, chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber; the raw rubber is 50 - 70 parts of natural rubber and 30 - 50 parts of cis - butadiene rubber.

2. A sidewall rubber composition for electric buses according to claim 1, characterized in that the antioxidant is one or a mixture of compounds of amines, phenols, imidazoles, metal carbamates and waxes.

3. A sidewall rubber composition for electric buses according to claim 1, characterized in that the anti - tear resin is one or a mixture of modified cyclopentadiene and dicyclopentadiene resin, ɑ - styrenyl resin, rosin - modified C9 resin, rosin derivatives, C9 resin - modified phenol - formaldehyde resin.

4. A sidewall rubber composition for electric buses according to claim 1, characterized in that The carbon black has a particle size of 20 to 30 nm, an iodine adsorption value of 82 to 121 g / kg, an oil absorption value of 72 to 119×10 -5 m 3 / kg, and a coloring strength of 103 to 124%.

5. A sidewall rubber composition for electric buses according to claim 1, characterized in that the vulcanizing agent includes sulfur, sulfur donors, functional resin cross - linkers, sulfenamide accelerators, thiazole accelerators, thiuram accelerators, thiourea accelerators, guanidine accelerators or dithiocarbamate accelerators.

6. A sidewall rubber composition for electric buses according to claim 1, characterized in that the zinc alkyl thiophosphate is one of zinc dialkyldithiophosphate, bis(iso - butyl) - o - pentyl bis(dithiophosphate) zinc, bis[O - (2 - ethylhexyl) - O - (2 - methylpropyl) dithiophosphate zinc, O,O - dibutyl dithiophosphate zinc.

7. The mixing method of a sidewall rubber composition for electric buses according to claim 1, characterized in that the method comprises the following steps: 1) First - stage mixing: Put raw rubber, carbon black, zinc oxide, stearic acid, protective wax, and anti - tear resin into a mixer and mix for 30 - 50 seconds, mix at a speed of 37 - 55 rpm, lift and press the material every 20 - 35 seconds. When the temperature of the rubber compound reaches 145℃ - 165℃, discharge the rubber and cut it into pieces. After cooling at room temperature for 8 - 12 hours, obtain the first - stage masterbatch, and then carry out the second - stage mixing on it; 2) Two-stage mixing: Put the first-stage masterbatch from step 1) and the polar rubber premix into a Banbury mixer, mix at a speed of 25 - 40 rpm, perform lifting and pressing of the rubber mass every 20 - 35 seconds, discharge the rubber and cut it into sheets when the temperature of the rubber compound reaches 135 - 150 °C, and obtain the second-stage masterbatch after cooling at room temperature for 8 - 12 hours, and then conduct final mixing on it; 3) Final mixing: Put the second-stage masterbatch from step 2), vulcanizing agent, and zinc alkylthiophosphate into a Banbury mixer, mix at a speed of 20 - 30 rpm, perform lifting and pressing of the rubber mass successively at intervals of 20 - 35 seconds, 20 - 30 seconds, and 15 - 25 seconds, discharge the rubber and cut it into sheets when the temperature of the rubber compound reaches 100 - 120 °C, and obtain the sidewall rubber composition of this tire after placing it for cooling.

8. A tire for an electric bus, characterized in that, the sidewall of this tire is prepared by vulcanization using a sidewall rubber composition described in any one of claims 1 - 6.

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