Tread rubber composition containing thiol-modified liquid styrene-butadiene copolymer modified with lignin and mixing method thereof

Abstract

This invention relates to the field of tire rubber manufacturing technology, and discloses a tread rubber composition containing mercapto-modified liquid styrene-butadiene synergistic lignin and its mixing method. This invention adds L-SBR-SH to the tread rubber composition to replace L-SBR, which effectively reduces the heat generation of the rubber compound. Simultaneously, surface-modified lignin and lignin masterbatch are added. The γ-aminopropyltriethoxysilane in the surface-modified lignin can synergistically react with L-SBR-SH, and the L-SBR-SH in the lignin masterbatch can act as an internal lubricant to inhibit lignin aggregation, thereby enabling lignin to be uniformly dispersed in the rubber composition. L-SBR-SH, lignin masterbatch, and surface-modified lignin synergistically improve the abrasion resistance and wet grip performance of the rubber composition, achieving a balance between heat generation, abrasion, and wet grip in the tread rubber composition.

Description

Technical Field

[0001] This invention relates to the field of tire rubber manufacturing technology, and more specifically, to a tread rubber composition containing mercapto-modified liquid styrene-butadiene synergistic lignin and its mixing method. Background Technology

[0002] With increasingly stringent regulations on energy conservation and emission reduction in the automotive industry, and rising user demands for both safety and durability, the development of tire tread compounds has long revolved around the contradiction between "low rolling resistance (low hysteresis / low heat generation) – high wet grip – high abrasion resistance." For high-performance tread systems based on solution-polymerized styrene-butadiene rubber (SSBR), replacing some carbon black with fumed silica (SiO2) and combining it with silane coupling agents can reduce hysteresis loss and improve rolling resistance to some extent. However, fumed silica is rich in silanol groups on its surface, which easily lead to agglomeration between particles through hydrogen bonding, resulting in difficulty in dispersion within the rubber matrix. Simultaneously, fumed silica has poor interfacial compatibility with non-polar or weakly polar rubbers, easily forming stress concentration points during mixing, causing increased dynamic heat generation, decreased abrasion resistance, or fluctuations in wet performance. Therefore, how to maintain the reinforcing and low-heat-generating advantages of fumed silica while further improving filler dispersion and interfacial structure to achieve a balance of comprehensive performance remains a key technical challenge in this field.

[0003] Chinese invention patent CN102796295A discloses a rubber composition for tire treads and pneumatic tires, comprising modified styrene-butadiene rubber with functional groups such as amino or carboxyl groups, silica, silane coupling agents, and lignin derivatives, to improve the balance between rolling resistance and wet performance. However, it does not take into account the heat generation problem of the rubber compound and usually still faces the following shortcomings: 1) Lignin has strong polarity, complex structure, and is prone to agglomeration. Simple blending or general derivatization treatment often makes it difficult to obtain a stable and uniform dispersion in the SSBR matrix; 2) The introduction of lignin may cause abrasion degradation or insufficient wet grip under certain formulation windows, making it difficult to achieve simultaneous improvement in low heat generation, abrasion resistance, and wet grip.

[0004] Liquid styrene-butadiene rubber (SBR) is currently mostly added to rubber compositions as a plasticizer. While it can reduce the viscosity of the rubber compound and some heat generation, its physical compatibility with the rubber and filler interface, without chemical bonding, weakens the interfacial bonding and significantly reduces abrasion resistance. It cannot simultaneously achieve low heat generation and high abrasion resistance. Low heat generation requires reducing friction at the rubber-filler interface, while high wet slip and high abrasion resistance depend on a dense reinforcing network and strong interfacial bonding. Overcoming the "devil's triangle" of "low heat generation, high wet slip, and high abrasion resistance" is a pressing issue that needs to be addressed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a tread rubber composition containing mercapto-modified liquid styrene-butadiene synergistic lignin and its mixing method. By adding L-SBR-SH, lignin masterbatch and surface-modified lignin, a balance is achieved in the tread rubber composition in terms of heat generation, abrasion and wet grip.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A tread rubber composition containing mercapto-modified liquid styrene-butadiene co-modified lignin, wherein the rubber composition is prepared by mixing raw materials comprising the following components based on 100 parts by weight of raw rubber: 65-70 parts by weight of solution-polymerized styrene-butadiene rubber 28-32 parts by weight of natural rubber 8-12 parts by weight of butadiene rubber 5-10 parts by weight of mercapto-modified liquid styrene-butadiene rubber. 42-52 parts by weight of highly dispersed silica 3.0-5.0 parts by weight of silane coupling agent. 6-13 parts by weight of surface-modified lignin 6-13 parts by weight of lignin masterbatch; The raw rubber is the sum of solution-polymerized styrene-butadiene rubber, natural rubber, cis-butadiene rubber, and mercapto-modified liquid styrene-butadiene rubber; The surface-modified lignin is obtained by lignin being modified with γ-aminopropyltriethoxysilane and polycaprolactone. The lignin masterbatch is prepared by mixing surface-modified lignin, solution-polymerized styrene-butadiene rubber, and mercapto-modified liquid styrene-butadiene rubber.

[0007] Preferably, the rubber composition is prepared by mixing raw materials comprising the following components based on 100 parts by weight of raw rubber: 65-70 parts by weight of solution-polymerized styrene-butadiene rubber 28-32 parts by weight of natural rubber 8-12 parts by weight of butadiene rubber 5-10 parts by weight of mercapto-modified liquid styrene-butadiene rubber. 42-52 parts by weight of highly dispersed silica 3.0-5.0 parts by weight of silane coupling agent. 6-13 parts by weight of surface-modified lignin 6-13 parts by weight of lignin masterbatch Vulcanizing agent 1.2-2.0 parts by weight, Accelerator 1.0-2.5 parts by weight, Anti-aging agent 1.0-2.0 parts by weight, 2.0-5.0 parts by weight of plasticizer. Activator 3.0-5.0 parts by weight.

[0008] Preferably, the solution-polymerized styrene-butadiene rubber has a styrene content of 25-30% and a vinyl content of 55-60%.

[0009] Preferably, the mercapto-modified liquid styrene-butadiene rubber has a number average molecular weight of 2500-3500 and a mercapto content of 0.4-0.6 eq / 100g.

[0010] Preferably, the preparation of the surface-modified lignin includes the following steps: after vacuum drying, lignin powder is added to a high-speed mixer, and modifiers γ-aminopropyltriethoxysilane and polycaprolactone are added in sequence. The mixture is modified at 110-120℃ and 1800-2200r / min for 35-45min, and then pulverized after cooling for later use. Preferably, the total amount of the modifier is 5%-7% of the lignin content; more preferably, the amount of γ-aminopropyltriethoxysilane is 3%-4% of the lignin content, and the amount of polycaprolactone is 2%-3% of the lignin content. Preferably, the mass ratio of γ-aminopropyltriethoxysilane to polycaprolactone is (1.5-2.0):1; Preferably, the vacuum drying temperature is 75-85℃ and the drying time is 3.5-4.5h; Preferably, the lignin powder has a particle size of 2-5 μm.

[0011] Preferably, the preparation of the lignin masterbatch includes the following steps: adding surface-modified lignin, solution-polymerized styrene-butadiene rubber, and mercapto-modified liquid styrene-butadiene rubber into a mixer, mixing at 120-130℃ and 70-80 r / min for 6-8 min, pressing into sheets and cooling for later use. Preferably, the mass ratio of the surface-modified lignin, solution-polymerized styrene-butadiene rubber, and mercapto-modified liquid styrene-butadiene rubber is 1:(2-3):0.6; Preferably, the thickness of the compressed tablet is 2-3 mm.

[0012] Preferably, the butadiene rubber is nickel-based butadiene rubber; And / or, the specific surface area (CTAB) of the highly dispersed silica is 220-240 m². 2 / g, DBP oil absorption value 2.1-2.3cm 3 / g, dispersibility ≥92%; And / or, the activator comprises zinc oxide and stearic acid, wherein the zinc oxide comprises 2.5-3.5 parts by weight and the stearic acid comprises 0.8-1.2 parts by weight; preferably, the zinc oxide has a particle size of 50-80 nm.

[0013] Furthermore, the present invention also provides a method for mixing the rubber composition, comprising the following steps: 1) First stage mixing: Add solution-polymerized styrene-butadiene rubber, natural rubber, and butadiene rubber to a mixer and masticate at 85-95℃ and 55-65 r / min for 3-4 min; add highly dispersed silica, surface-modified lignin, and silane coupling agent, and mix at 95-105℃ for 5-6 min; then add mercapto-modified liquid styrene-butadiene rubber and other chemical auxiliaries (except for lignin masterbatch, vulcanizing agent, and accelerator), heat to 135-145℃ and mix for 7-9 min, discharge the rubber to obtain the first stage compound, discharge temperature ≤150℃, and let stand for 6-8 hours to cool to room temperature; 2) Two-stage mixing: Add the first-stage compound and lignin masterbatch to the open mill and pass through it 4-6 times at 55-65℃; add vulcanizing agent and accelerator, mix for 4-5 minutes, and control the temperature of the compound to ≤70℃ to obtain the final compound.

[0014] Preferably, the final rubber compound is vulcanized at 155-165°C and 18-22 MPa for “T90+1min”; T90 is measured using the final rubber compound.

[0015] This invention, through the above scheme, adds L-SBR-SH to the tread rubber composition to replace L-SBR, which can effectively reduce the heat generation of the rubber compound. At the same time, surface-modified lignin and lignin masterbatch are added. The surface-modified lignin is obtained by composite modification of lignin with γ-aminopropyltriethoxysilane and polycaprolactone. The lignin masterbatch is prepared by compounding surface-modified lignin, solution-polymerized styrene-butadiene rubber, and mercapto-modified liquid styrene-butadiene rubber. Among them, γ-aminopropyltriethoxysilane can react synergistically with L-SBR-SH, and L-SBR-SH can also act as an internal lubricant of lignin masterbatch to inhibit lignin agglomeration, so that lignin can be uniformly dispersed in the rubber composition. L-SBR-SH, lignin masterbatch and surface-modified lignin can synergistically improve the wear resistance and wet grip performance of the rubber composition, and achieve a balance between heat generation, wear and wet grip in the tread rubber composition. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0017] The rubber composition of this embodiment is obtained by combining fillers, vulcanizing agents, and other auxiliary materials with a rubber component formed from solution-polymerized styrene-butadiene rubber (SSBR) and other conjugated diene rubbers.

[0018] (Rubber composition) Examples of conjugated diene rubbers used as rubber components include natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, or styrene-isoprene-butadiene copolymer rubber, and various diene rubbers commonly used in tire tread rubber compositions. These conjugated diene rubbers can be used alone or in blends of two or more.

[0019] In embodiments of the present invention, blends of solution-polymerized styrene-butadiene rubber (SSBR) and other conjugated diene rubbers are preferred, especially blends of natural rubber (NR), butadiene rubber (BR) and solution-polymerized styrene-butadiene rubber (SSBR) as part of the rubber base. In the present invention, mercapto-modified liquid styrene-butadiene rubber is also incorporated.

[0020] (Silicon dioxide) Silica refers to silica-silicic acid based filler materials, and not just silica in the narrow sense. It can be appropriately selected from existing materials used as reinforcing fillers. Examples include wet silica (hydrated silica) and dry silica (anhydrous silica). In the embodiments of this invention, highly dispersed silica is preferred.

[0021] CTAB of silica is preferably 220m. 2 CTAB concentrations above a certain level (g) and not below the lower limit tend to provide good reinforcing effects, resulting in excellent properties including tensile strength and abrasion resistance. CTAB concentrations of silica with a g content of 240 μg or higher are also preferred. 2 Below a certain value ( / g), CTAB levels not exceeding the upper limit tend to result in good dispersibility. Furthermore, the CTAB content of silica is determined according to ISO 5794-1:2006.

[0022] (Silane coupling agent) When the above-mentioned rubber composition contains silica, it preferably further contains a silane coupling agent. There are no particular limitations on the silane coupling agent; commonly used silane coupling agents can be used. Examples include silane coupling agents based on sulfides, polysulfides, thioesters, thiols, olefins, epoxy groups, amino groups, and alkyl groups. These 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.

[0023] Examples of silane coupling agents for the aforementioned sulfide systems 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-triethoxysilylpropyl)trisulfide, bis(3-trimethoxysilylpropyl)trisulfide, and bis(3-methyldimethoxysilylpropyl)tetrasulfide. Bis(2-triethoxysilylethyl) trisulfide, bis(3-monoethoxydimethylsilylpropyl) tetrasulfide, bis(3-monoethoxydimethylsilylpropyl) trisulfide, bis(3-monoethoxydimethylsilylpropyl) disulfide, bis(3-monoethoxydimethylsilylpropyl) tetrasulfide, bis(3-monoethoxydimethylsilylpropyl) trisulfide, bis(3-monoethoxydimethylsilylpropyl) disulfide, bis(2-monoethoxydimethylsilylethyl) tetrasulfide, bis(2-monoethoxydimethylsilylethyl) trisulfide, bis(2-monoethoxydimethylsilylethyl) disulfide, etc.

[0024] Examples of silane coupling agents in the aforementioned thioester system include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3-lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, and 2-lauroylthio... Ethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, 2-lauroylthioethyltrimethoxysilane, etc.

[0025] Examples of thiol-based silane coupling agents include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, γ-mercaptopropylethoxybis(propane-hexaethoxy-siloxane), and 3-octanoylthio-1-propyltriethoxysilane.

[0026] Examples of olefin-based silane coupling agents 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, and 3-[tris(trimethylsiloxy)silyl]propyl methacrylate.

[0027] Examples of epoxy-based silane coupling agents include 3-epoxypropoxypropyl(dimethoxy)methylsilane, 3-epoxypropoxypropyltrimethoxysilane, diethoxy(3-epoxypropoxypropyl)methylsilane, triethoxy(3-epoxypropoxypropyl)silane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0028] Examples of amino-based silane coupling agents include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-ethoxysilyl-N-(1,3-dimethylbutylene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane.

[0029] In the embodiments of the present invention, one or more of bis(3-triethoxysilylpropyl)tetrasulfide (Si-69), 3-mercaptopropyltrimethoxysilane (Si-75), and 3-octanoylthio-1-propyltriethoxysilane (NXT) are preferred, and the proportion is not particularly limited, with 3-mercaptopropyltrimethoxysilane (Si-75) being particularly preferred.

[0030] The content of the silane coupling agent relative to 100 parts by weight of silica is preferably 3 parts by weight or more, more preferably 5 parts by weight or more. Amounts of 3 parts by weight or more tend to provide an additive effect. This amount is also preferably 20 parts by weight or less, more preferably 15 parts by weight or less. Amounts not exceeding 20 parts by weight tend to produce an effect comparable to the amount added, and tend to achieve good processability during mixing.

[0031] (Activator) There are no particular limitations on the activator used; commonly used activators can be used. Zinc oxide and stearic acid are typically used together as activators. Commonly used zinc oxides include indirect zinc oxide, active zinc oxide, and nano zinc oxide. Indirect zinc oxide is commonly used, but its dispersibility is poor, requiring a higher dosage. Active zinc oxide is evenly distributed in the rubber compound, has a large contact area with hydrogen sulfide, and a greater chance of interfacial reaction. Furthermore, the active substances in active zinc oxide products provide a co-catalytic effect, resulting in a high conversion rate of zinc oxide to zinc sulfide. Therefore, active zinc oxide is an excellent vulcanizing activator, and its dosage can be appropriately reduced compared to indirect zinc oxide. Nano zinc oxide particles have a diameter in the range of 10-80 nm, a large specific surface area, and exhibit three effects: interfacial interaction, small size, and quantum tunneling. It has high activity and can effectively reduce the amount of zinc oxide used. Commercially available stearic acid can be used as the stearic acid.

[0032] (Vulcanizing agent) There are no particular restrictions on the type of vulcanizing agent; commonly used vulcanizing agents can be used. Examples of vulcanizing agents include sulfur and sulfur derivatives, organic peroxides, and resin-based vulcanizing agents.

[0033] Examples of sulfur and sulfur derivatives mentioned above include sulfur powder, insoluble sulfur, tetramethylthiuram disulfide, diethylthiuram disulfide, dibenzothiazole disulfide, N-cyclohexyl-2-benzothiazole sulfenamide, 2-mercaptobenzothiazole, tetraethylthiuram disulfide, tetramethylthiuram monosulfide, dibenzyl disulfide, dipentamethylenethiuram tetrasulfide, alkylphenol sulfides, etc.

[0034] Examples of the aforementioned organic peroxides include dicumyl peroxide, di-tert-butyl peroxide, benzoyl peroxide, tert-butyl peroxide benzoate, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 1,1-bis(tert-butylperoxy)cyclohexane, lauroyl peroxide, cyclohexanone peroxide, tert-butyl hydroperoxide, di-di-tert-butyl hydroperoxide, propylphenyl hydroperoxide, cyclohexanone peroxide, and 1,4-bis-tert-butylperoxyisopropylbenzene.

[0035] Examples of resin-based vulcanizing agents include p-tert-butylphenol formaldehyde resin, p-tert-octylphenol formaldehyde resin, alkylphenol formaldehyde resin, phenol formaldehyde resin, brominated p-tert-butylphenol formaldehyde resin, hexamethoxymethyl melamine resin, epoxy resin, phenolic epoxy resin, cashew nut phenolic resin, resorcinol formaldehyde resin, bismaleimide resin (BMI), urea-formaldehyde resin, furfural resin, and o-cresol formaldehyde epoxy resin.

[0036] These vulcanizing agents can be used alone or in combination of two or more. Sulfur powder and insoluble sulfur are preferred.

[0037] (Vulcanization accelerator) There are no particular restrictions on the type of accelerator; commonly used vulcanization accelerators can be used. Examples include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamate, aldehyde-amine, or aldehyde-amine accelerators. These can be used alone or in combination of two or more.

[0038] Examples of sulfonamide compounds include N-cyclohexyl-2-benzothiazolyl sulfonamide, N-tert-butyl-2-benzothiazolyl sulfonamide, N,N-dicyclohexyl-2-benzothiazolyl sulfonamide, N-oxodiethylidene-2-benzothiazolyl sulfonamide, and N,N-diisopropyl-2-benzothiazolyl sulfonamide.

[0039] Examples of the aforementioned thiazole series include 2-mercaptobenzothiazole, dibenzothiazole disulfide, zinc salt of 2-mercaptobenzothiazole, N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, N-oxodiethylene-2-benzothiazole sulfenamide, derivatives of dibenzothiazole disulfide, sodium salt of 2-thiol-benzothiazole, and 2-benzothiazole disulfide.

[0040] Examples of the aforementioned thiuram series include tetramethylthiuram disulfide, tetramethylthiuram monosulfide, tetraethylthiuram disulfide, tetraisobutylthiuram disulfide, tetrabenzylthiuram disulfide, dipentylthiuram disulfide, bis(1,5-pentylene)thiuram tetrasulfide, bispentamethylenethiuram hexasulfide, tetra(2-ethylhexyl)thiuram disulfide, and bispentamethylenethiuram monosulfide.

[0041] Examples of guanidine compounds mentioned above include diphenylguanidine, di-o-toluidine, triphenylguanidine, o-toluidine, and diphenylguanidine phthalate.

[0042] Examples of dithiocarbamate compounds include zinc ethylphenyl dithiocarbamate, zinc butylphenyl dithiocarbamate, sodium dimethyl dithiocarbamate, zinc dimethyl dithiocarbamate, zinc diethyl dithiocarbamate, zinc dibutyl dithiocarbamate, zinc dipentyl dithiocarbamate, zinc dipropyl dithiocarbamate, a coordination salt of zinc pentamethylene dithiocarbamate and piperidine, zinc hexadecyl isopropyl dithiocarbamate, zinc octadecyl isopropyl dithiocarbamate, zinc dibenzyl dithiocarbamate, sodium diethyl dithiocarbamate, piperidine pentamethylene dithiocarbamate, selenium dimethyl dithiocarbamate, tellurium diethyl dithiocarbamate, cadmium dipentyl dithiocarbamate, etc.

[0043] Examples of aldehyde-amine or aldehyde-amine compounds mentioned above include acetaldehyde-aniline reactants, butyraldehyde-aniline condensates, hexamethylenetetramine, and acetaldehyde-amine reactants.

[0044] These accelerators can be used alone or in combination of two or more. N-tert-butyl-2-benzothiazole sulfenamide (NS) and dibenzothiazole disulfide (DM) are preferred.

[0045] (Anti-aging agents) There are no particular limitations on antioxidants; commonly used antioxidants can be used. Examples include amines, phenols, and heterocyclic antioxidants. They can be used alone or in combination of two or more.

[0046] Examples of amine antioxidants include N-phenyl-N'-isopropyl-p-phenylenediamine, N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and N-(1-methylheptyl)-N'-phenyl-p-phenylenediamine.

[0047] Examples of phenolic antioxidants include 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and tris[2,4-di-tert-butylphenyl] phosphite.

[0048] Examples of heterocyclic antioxidants include 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 2-(2-hydroxyphenyl)benzimidazole, and 2,2,4-trimethyl-1,2-dihydroquinoline polymer (RD).

[0049] These antioxidants can be used alone or in combination of two or more. N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine (antioxidant 4020) is preferred.

[0050] (Softener) Softeners are mainly classified into three categories: petroleum-based, vegetable oil-based, and ester-based, with petroleum-based being the most commonly used. Petroleum-based softeners include processing oils and petroleum resins. Processing oils typically include aromatic oils, naphthenic oils, and paraffin oils, while petroleum resins usually refer specifically to low-softening-point petroleum resins. Vegetable oil-based softeners are derived from natural raw materials, are environmentally friendly, and have a low odor; common varieties include pine tar, tall oil, castor oil, and soybean oil. Ester-based softeners are typically used in high-performance tire treads and generally include phthalates, adipates, and polyesters. Phthalate esters include dioctyl phthalate and dibutyl phthalate; adipates include dioctyl adipate; and polyesters include polypropylene adipate. In this embodiment, bio-based epoxy fatty acid methyl esters are preferred. Example

[0051] The formulations of the examples and comparative examples are shown in Table 1 (excluding the amount of oil added to the raw rubber).

[0052] Table 1

[0053] The sources of raw materials are as follows: 1. Solution-polymerized styrene-butadiene rubber (SSBR), 5361H, Kumho Rubber, styrene content 28%, vinyl content 58%, Mooney viscosity ML (1+4) 100℃=60-70.

[0054] 2. Natural rubber (NR), SCR20, Sinochem International, Mooney viscosity ML (1+4) 100℃=65-75.

[0055] 3. Nickel-based cis-butadiene rubber (BR), BR 9000, Zhejiang Chuanhua, Mooney viscosity ML (1+4) 100℃ = 48-58.

[0056] 4. Highly dispersed silica, VN3, Evonik Chemicals, specific surface area 220-240 m² 2 / g, DBP oil absorption value 2.1-2.3cm 3 / g, dispersibility ≥92%.

[0057] 5. Silane coupling agent, Si75, Nanjing Shuguang.

[0058] 6. Surface-modified lignin, with a KH-550 and polycaprolactone mass ratio of 1.5:1. KH-550, from Shanghai Kanglang Biotechnology Co., Ltd., chemically named γ-aminopropyltriethoxysilane. Sulfate lignin, from Shandong Ailiwan Chemical Co., Ltd., with a particle size of 2-5 μm.

[0059] 7. Masterbatch lignin, surface dynamically modified lignin, SSBR and L-SBR-SH in a mass ratio of 1:2.5:0.6, Mooney viscosity ML(1+4)100℃=50-60.

[0060] 8. Vulcanizing agent, insoluble sulfur IS-60, Yanggu Huatai.

[0061] 9. Accelerator NS, chemical name N-tert-butyl-2-benzothiazole sulfenamide, Yanggu Huatai.

[0062] 10. Accelerator DM, chemical name dibenzothiazole disulfide, Yanggu Huatai.

[0063] 11. Antioxidant 4020, chemical name N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, Yanggu Huatai.

[0064] 12. Epoxy fatty acid methyl ester, Yanggu Huatai.

[0065] 13. Nano zinc oxide, Shijiazhuang Zhiyi Zinc Industry Co., Ltd.

[0066] 14. Plant-derived stearic acid, Yanggu Huatai.

[0067] <Preparation of Surface-Modified Lignin> After vacuum drying at 80℃ for 4 hours, sulfate lignin powder was added to a high-speed mixer. Then, KH-550 and polycaprolactone (KH-550: polycaprolactone = 1.5:1) were added sequentially. KH-550 accounted for 3% of the lignin mass, and polycaprolactone accounted for 2% of the lignin mass. The mixture was modified at 115℃ and 1800 r / min for 35 minutes. After cooling, it was pulverized for later use.

[0068] Lignin Masterbatch Surface-modified lignin, SSBR, and L-SBR-SH were added to an internal mixer at a mass ratio of 1:2.5:0.6 and mixed at 125℃ and 80r / min for 7 minutes. During this process, the lubricity of L-SBR-SH was used to inhibit lignin agglomeration, so that the lignin was evenly dispersed and formed a preliminary bond with SSBR to form a stable and dispersed masterbatch. The masterbatch was then pressed into tablets (2-3mm thick) and cooled for later use.

[0069] <l-sbr-sh> S1) Synthesis of the bislithium initiator: 2,6-dimethylpyridine, sec-butyllithium and tetrahydrofuran were fed into a polymerization reactor in a molar ratio of 1:1.3:1, and cyclopentane was used as the solvent. The mixture was stirred at room temperature for 1 hour.

[0070] S2) Polymerization reaction: Butadiene and dry styrene are fed in a mass ratio of 3:1, followed by the addition of the remaining solvent, and finally mercaptoethanol is added in an amount of 1.5-2.0% of the total mass of monomers. Hot water is passed through to raise the temperature to 50°C and the reaction is kept at a constant temperature for 5 hours.

[0071] S3) End capping and post-treatment: Take a sample from the polymerization reactor every 1 hour, put the polymerization liquid into a sampling bottle containing a small amount of ethanol, and after standing, a white transparent gel precipitate is obtained. Place the gel in a vacuum oven for vacuum drying to obtain mercapto-modified liquid styrene-butadiene rubber (L-SBR-SH).

[0072] The difference between Comparative Example 1 and Example 3 is that Comparative Example 1 did not contain L-SBR-SH (thiol-modified liquid styrene-butadiene rubber).

[0073] The main difference between Comparative Example 2 and Example 3 is that L-SBR is used instead of L-SBR-SH.

[0074] The main difference between Comparative Example 3 and Example 3 is that no lignin masterbatch was added.

[0075] The main difference between Comparative Example 4 and Example 3 is that unmodified lignin was used instead of surface-modified lignin.

[0076] <Mixing Method> The mixing methods for the examples and comparative examples are as follows: 1) First-stage mixing (dynamic interface pre-construction): Add solution-polymerized styrene-butadiene rubber, natural rubber, and butadiene rubber to a mixer and masticate at 85-95℃ and 55-65 r / min for 3-4 min; add highly dispersed silica, surface-modified lignin, and silane coupling agent, and mix at 95-105℃ for 5-6 min; then add mercapto-modified liquid styrene-butadiene rubber and other chemical auxiliaries (except for lignin masterbatch, vulcanizing agent, and accelerator), heat to 135-145℃ and mix for 7-9 min, discharge the rubber to obtain the first-stage compound, discharge temperature ≤150℃, and let stand for 6-8 hours to cool to room temperature; 2) Two-stage mixing (interface strengthening and cross-linking control): Add the first-stage compound and lignin masterbatch to the open mill and pass through it 4-6 times at 55-65℃; add vulcanizing agent and accelerator, mix for 4-5 minutes, and control the temperature of the compound to ≤70℃ to obtain the final compound.

[0077] <Testing Methods> 1. Dynamic heat generation: Tested according to GB / T 1687.3-2016 (60℃, load 1.82MPa, time 30min).

[0078] 2. Dynamic mechanical properties: DMA test (-60~80℃, frequency 10Hz, 60℃ tanδ reflects heat generation, 0℃ tanδ reflects wet grip) 3. Wet friction coefficient: Tested according to GB / T 3903.6-2005 (tile surface wetted with water, load 100N, sliding speed 100mm / min).

[0079] 4. Abrasion resistance: GB / T 1689-2014 (Akron abrasion resistance).

[0080] 5. Mechanical properties: Tensile strength is tested according to GB / T 528-2009, and tear strength is tested according to GB / T 529-2008.

[0081] The test results are shown in Table 2.

[0082] Table 2

[0083] A comparison of Comparative Example 2 (L-SBR) and Example 1 (L-SBR-SH) shows that Comparative Example 2, lacking dynamic bonding, exhibits inferior wear resistance compared to Example 3 (0.100 cm). 3 This is because the dynamic SO bonds of L-SBR-SH can be reversibly broken and recombined under stress, reducing the friction at the rubber-filler interface, thereby reducing heat generation without causing a deterioration in wear resistance.

[0084] Comparative Example 1 (without L-SBR-SH), Comparative Example 3 (without lignin masterbatch), Comparative Example 4 (without surface-modified lignin), and Example 3 show that L-SBR-SH, lignin masterbatch, and surface-modified lignin can synergistically improve the abrasion resistance and wet grip properties of the rubber composition.

[0085] The foregoing description of embodiments of the present invention, through which those skilled in the art are able to implement or use the present invention, will be readily apparent to those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novelty disclosed herein.

Claims

1. A tread rubber composition containing mercapto-modified liquid styrene-butadiene co-modified lignin, characterized in that, The rubber composition is prepared by mixing raw materials comprising the following components based on 100 parts by weight of raw rubber: 65-70 parts by weight of solution-polymerized styrene-butadiene rubber 28-32 parts by weight of natural rubber 8-12 parts by weight of butadiene rubber 5-10 parts by weight of mercapto-modified liquid styrene-butadiene rubber. 42-52 parts by weight of highly dispersed silica 3.0-5.0 parts by weight of silane coupling agent. 6-13 parts by weight of surface-modified lignin 6-13 parts by weight of lignin masterbatch; The raw rubber is the sum of solution-polymerized styrene-butadiene rubber, natural rubber, cis-butadiene rubber, and mercapto-modified liquid styrene-butadiene rubber; The surface-modified lignin is obtained by lignin being modified with γ-aminopropyltriethoxysilane and polycaprolactone. The lignin masterbatch is prepared by mixing surface-modified lignin, solution-polymerized styrene-butadiene rubber, and mercapto-modified liquid styrene-butadiene rubber.

2. The tread rubber composition containing mercapto-modified liquid styrene-butadiene synergistic lignin as described in claim 1, characterized in that, The rubber composition is prepared by mixing raw materials comprising the following components based on 100 parts by weight of raw rubber: 65-70 parts by weight of solution-polymerized styrene-butadiene rubber 28-32 parts by weight of natural rubber 8-12 parts by weight of butadiene rubber 5-10 parts by weight of mercapto-modified liquid styrene-butadiene rubber. 42-52 parts by weight of highly dispersed silica 3.0-5.0 parts by weight of silane coupling agent. 6-13 parts by weight of surface-modified lignin 6-13 parts by weight of lignin masterbatch Vulcanizing agent 1.2-2.0 parts by weight, Accelerator 1.0-2.5 parts by weight, Anti-aging agent 1.0-2.0 parts by weight, 2.0-5.0 parts by weight of plasticizer. Activator 3.0-5.0 parts by weight.

3. The tread rubber composition containing mercapto-modified liquid styrene-butadiene co-modified lignin according to claim 1 or 2, characterized in that, The solution-polymerized styrene-butadiene rubber has a styrene content of 25-30% and a vinyl content of 55-60%.

4. The tread rubber composition containing mercapto-modified liquid styrene-butadiene synergistic lignin according to claim 1 or 2, characterized in that, The mercapto-modified liquid styrene-butadiene rubber has a number average molecular weight of 2500-3500 and a mercapto content of 0.4-0.6 eq / 100g.

5. The tread rubber composition containing mercapto-modified liquid styrene-butadiene co-modified lignin according to claim 1 or 2, characterized in that, The preparation of the surface-modified lignin includes the following steps: After vacuum drying, lignin powder is added to a high-speed mixer, followed by the addition of modifiers γ-aminopropyltriethoxysilane and polycaprolactone. The mixture is modified at 110-120℃ and 1800-2200r / min for 35-45min, then cooled and pulverized for later use. Preferably, the total amount of the modifier is 5%-7% of the lignin content; more preferably, the amount of γ-aminopropyltriethoxysilane is 3%-4% of the lignin content, and the amount of polycaprolactone is 2%-3% of the lignin content. Preferably, the mass ratio of γ-aminopropyltriethoxysilane to polycaprolactone is (1.5-2.0):1; Preferably, the vacuum drying temperature is 75-85℃ and the drying time is 3.5-4.5h; Preferably, the lignin powder has a particle size of 2-5 μm.

6. The tread rubber composition containing mercapto-modified liquid styrene-butadiene co-modified lignin according to claim 1 or 2, characterized in that, The preparation of the lignin masterbatch includes the following steps: adding surface-modified lignin, solution-polymerized styrene-butadiene rubber, and mercapto-modified liquid styrene-butadiene rubber into a mixer, mixing at 120-130℃ and 70-80 r / min for 6-8 min, pressing into sheets and cooling for later use. Preferably, the mass ratio of the surface-modified lignin, solution-polymerized styrene-butadiene rubber, and mercapto-modified liquid styrene-butadiene rubber is 1:(2-3):0.6; Preferably, the thickness of the compressed tablet is 2-3 mm.

7. The tread rubber composition containing mercapto-modified liquid styrene-butadiene synergistic lignin according to claim 1 or 2, characterized in that, The cis-butadiene rubber mentioned is nickel-based cis-butadiene rubber; And / or, the specific surface area (CTAB) of the highly dispersed silica is 220-240 m². 2 / g, DBP oil absorption value 2.1-2.3cm 3 / g, dispersibility ≥92%; And / or, the activator comprises zinc oxide and stearic acid, wherein the zinc oxide comprises 2.5-3.5 parts by weight and the stearic acid comprises 0.8-1.2 parts by weight; preferably, the zinc oxide has a particle size of 50-80 nm.

8. The method for mixing the rubber composition according to any one of claims 1-7, characterized in that, Includes the following steps: 1) First stage mixing: Add solution-polymerized styrene-butadiene rubber, natural rubber, and butadiene rubber to a mixer and masticate at 85-95℃ and 55-65 r / min for 3-4 min; add highly dispersed silica, surface-modified lignin, and silane coupling agent, and mix at 95-105℃ for 5-6 min; then add mercapto-modified liquid styrene-butadiene rubber and other chemical auxiliaries (except for lignin masterbatch, vulcanizing agent, and accelerator), heat to 135-145℃ and mix for 7-9 min, discharge the rubber to obtain the first stage compound, discharge temperature ≤150℃, and let stand for 6-8 hours to cool to room temperature; 2) Two-stage mixing: Add the first-stage compound and lignin masterbatch to the open mill and pass through it 4-6 times at 55-65℃; add vulcanizing agent and accelerator, mix for 4-5 minutes, and control the temperature of the compound to ≤70℃ to obtain the final compound.

9. The method for mixing the rubber composition according to claim 8, characterized in that, The final rubber compound is vulcanized at 155-165℃ and 18-22MPa at a rate of "T90+1min"; T90 is measured using the final rubber compound.

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