Use of a thiocarboxylate silane coupling agent

Abstract

This invention discloses a thiocarboxylic acid ester silane coupling agent for the modification of rubber substrates. This solution addresses the core contradiction in existing natural rubber-based green low-VOC tire formulations: the difficulty in simultaneously achieving deep VOC emission reduction and improving the interfacial, mechanical, and dynamic properties of the rubber compound. It also resolves issues such as high levels of silane hydrolysis byproducts and residues, poor interfacial bonding and dispersibility between silane and fillers, the tendency to exacerbate VOC emissions by improving filler agglomeration, insufficient compatibility between the formulation and silane reaction characteristics, and inadequate process control. Ultimately, in high-wear-resistant heavy-duty tire tread applications, the total VOC emission of the rubber compound is ≤0.28 mg / m³, tensile strength ≥29 MPa, tear strength ≥98 kN / m, and Akron abrasion ≤0.17 cm³ / 1.61 km; in green low rolling resistance tire tread applications for new energy vehicles, the total VOC emission of the rubber compound is ≤0.22 mg / m³, tensile strength ≥28 MPa, tanδ ≤0.10 at 60℃, tanδ ≥0.35 at 0℃, and wet skid resistance meets EU Tire Labelling Act Class A.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, specifically to the application of a thiocarboxylic acid ester silane coupling agent. Background Technology

[0002] The tire industry is currently moving towards green and low-emission development. The EU REACH regulation and my country's GB / T 22030-2021 standards limit the total VOC emission concentration of tires to ≤0.5mg / m³. New energy vehicles have put forward comprehensive performance requirements for tires, including low rolling resistance, high wear resistance, and wet skid resistance, which has increased the difficulty of formula research and development. Silane coupling agents are the core interfacial additives in this type of formulation. Among them, bis-[γ-(triethoxysilyl)propyl]tetrasulfide (Si69), 3-octanoylthio-1-propyltriethoxysilane (NXT silane), γ-mercaptopropyltriethoxysilane (KH590), and γ-aminopropyltriethoxysilane (KH550) are commonly used in tire rubber modification. The above-mentioned silane coupling agent molecules have both polar and non-polar groups, which can combine with polar inorganic fillers and non-polar rubber matrices respectively, improve the interfacial bonding strength of rubber-filler and improve filler dispersibility. The selection of their type and application method directly determines the VOC emission level and performance of tire rubber compounds.

[0003] However, in existing green low-VOC tire formulations, single silane coupling agents are the main source of VOC emissions from rubber compounds, making it difficult to balance environmental protection and modification effects. Traditional sulfur-containing silanes such as Si69 and KH590 produce a large amount of ethanol byproducts upon hydrolysis. The VOC emission concentration of Si69-modified rubber compounds reaches 0.8~1.2 mg / m³, far exceeding the national standard limit. Although NXT silanes produce fewer hydrolysis byproducts and are currently commonly used for low-VOC modification, they only bond with fillers through silicon-oxygen bonds, resulting in limited interfacial bonding strength. This fails to effectively weaken the Payne effect caused by filler agglomeration, exacerbates dynamic heat generation during rubber compound processing, and easily leads to degradation of rubber molecular chains and the generation of additional VOCs. Furthermore, their effect on the dispersion and modification of fillers in natural rubber-based compounds is poor. Aminosilanes such as KH550 have poor reactivity with the rubber matrix and are difficult to meet the reinforcement requirements of tire compounds when used alone. When physically mixed with other silanes, they also suffer from poor compatibility and uneven dispersion. Non-rubber components in the natural rubber molecular chain are prone to causing inorganic filler agglomeration. Existing technologies that increase the amount of silane to improve dispersibility will further increase hydrolysis byproducts, exacerbating the core contradiction between VOC emissions and modification effects.

[0004] In summary, existing green low-VOC tire formulations have significant shortcomings in the matching processes and formulation design of silane coupling agents, further amplifying the application deficiencies of existing silanes. Current modification schemes simply replace low-VOC raw materials without addressing specific formulation optimizations such as filler pretreatment and precise control of silane addition based on the reaction characteristics of existing silanes. This fails to leverage the interfacial modification effect of silanes at the formulation level and makes it difficult to achieve VOC source reduction at the process level. Ultimately, existing formulations are caught in a contradiction between VOC emission reduction and improving the overall performance of the rubber compound. They either sacrifice the mechanical and dynamic properties of the rubber compound to achieve VOC compliance or pursue tire performance at the expense of exceeding VOC emission limits. To date, there is still no dedicated green low-VOC formulation suitable for natural rubber-based tire tread compound systems, failing to meet stringent environmental regulations and the industrial production needs of green tires. Summary of the Invention

[0005] To address the challenge of simultaneously reducing VOC emissions and enhancing tire modification in green, low-VOC tire formulations, this invention provides an application of a thiocarboxylic acid ester silane coupling agent.

[0006] The technical solution adopted in this invention is: Application of a thiocarboxylic acid ester silane coupling agent, wherein the thiocarboxylic acid ester silane coupling agent is used for the modification of a rubber substrate.

[0007] Preferably, the thiocarboxylic acid ester silane coupling agent is prepared by chemical co-reaction of chloromethylphenethyltriethoxysilane and NXT silane, and the specific preparation method is as follows: S1: Mix deionized water with an organic solvent to prepare a water-organic mixed solvent; add sodium sulfide to the water-organic mixed solvent and stir until there are no solid particles, then add phase transfer catalyst and add octanoyl chloride dropwise. After the addition is complete, stir twice to obtain sodium thiooctanoate water-organic mixed catalyst solution. S2: Add chloromethylphenylethyltriethoxysilane and chloropropyltriethoxysilane to the sodium thiooctanoate aqueous-organic mixed catalyst solution obtained in S1; then adjust the pH of the system to weakly alkaline, increase the stirring rate, and stir the reaction at a constant temperature after heating. S3: After the reaction in step S2 is completed, the reaction solution is allowed to stand and the organic phase is separated. The organic phase is washed until neutral. The organic phase after water washing is subjected to gradient vacuum distillation to obtain chloromethylphenethyltriethoxysilane-NTX silane composite thiocarboxylic acid ester silane coupling agent.

[0008] This application also provides the application of the thiocarboxylic acid ester silane coupling agent in the tread of heavy-duty tires, wherein the composition of the heavy-duty tire tread includes: 100 parts of natural rubber base material, 50-60 parts of highly dispersed silica, 1.5-3.0 parts of thiocarboxylic acid ester silane coupling agent, 4-5 parts of active zinc oxide, 1-2 parts of high-purity stearic acid, 1.5-2.0 parts of insoluble sulfur, and 0.8-1.0 parts of accelerator TBBS.

[0009] The thiocarboxylic acid ester silane coupling agent used in this application is prepared by chemical co-reaction of chloromethylphenethyltriethoxysilane and NXT silane. While retaining the advantages of acyl group protection of thiol structure, low VOC, low odor, and mild hydrolysis, the bifunctional silane can form efficient and stable interfacial bonds with rubber macromolecules and fillers respectively, significantly improving the uniformity of filler dispersion and the interfacial bonding strength of rubber-filler, thus overcoming the shortcomings of insufficient interfacial effect of single coupling agents at the molecular level.

[0010] Preferably, the specific steps for preparing the heavy-duty tire tread are as follows: S1: Highly dispersed silica is spray-dried at 120°C for 2 hours until the moisture content is ≤0.5%, and then coupled with a thiocarboxylic acid ester silane coupling agent at 300~500 r / min. S1: Premix the filler by dry mixing for 5-8 minutes to obtain a premixed filler; S2: Add natural rubber base material to the premixed filler in step S1, and mix for 5-8 minutes at a first-stage mixing temperature of 80-100℃ and a rotor speed of 80-100 r / min; S3: Add active zinc oxide and stearic acid to the mixture after mixing in step S2, and mix for 5-8 minutes at a second-stage mixing temperature of 110-130℃ and a rotor speed of 60-80 r / min to ensure that the reaction completeness of silane with filler and rubber is ≥95%; S4: Add insoluble sulfur and accelerator TBBS to the mixture after mixing in step S3, and mix for 1-2 minutes at a final mixing temperature of 60-70℃ and a rotor speed of 30-50 r / min, and then discharge the rubber to obtain a compound; S5: Vulcanize the compound obtained in step S4 at a vulcanization temperature of 140-160℃ and a pressure of 10-18 MPa for 8-15 minutes to obtain the tread of a heavy-duty tire.

[0011] This application employs a gradient cooling mixing process to avoid stress concentration in rubber shrinkage, suppress VOC release caused by silane hydrolysis and rubber degradation, and stabilize the overall performance of the rubber compound to meet the needs of industrial production.

[0012] This application also provides the application of the thiocarboxylic acid ester silane coupling agent in the tread of a green low rolling resistance tire. The composition of the green low rolling resistance tire tread includes: 100 parts of rubber base material, 50-55 parts of carbon black, 1.5-2.75 parts of thiocarboxylic acid ester silane coupling agent, 4-4.5 parts of active zinc oxide, 1.5-2.0 parts of high-purity stearic acid, 1.6-1.8 parts of insoluble sulfur, and 1.0-1.2 parts of compounding accelerator.

[0013] Preferably, the rubber substrate is composed of natural rubber and butadiene rubber, wherein the natural rubber comprises 65-75 parts and the butadiene rubber comprises 25-35 parts; the carbon black is composed of highly dispersed silica and low oil absorption carbon black, wherein the highly dispersed silica comprises 30-35 parts and the low oil absorption carbon black comprises 20-25 parts; the compound accelerator is composed of accelerator CZ and accelerator TBBS, and the compounding ratio can be conventional. In the embodiments of this application, a compound accelerator with a mass ratio of CZ:TBBS=5:1 is used.

[0014] This application also provides the specific steps for preparing the green low rolling resistance tire tread as follows: S1: After spray drying carbon black at 120℃ for 2 hours until the moisture content is ≤0.5%, it is coupled with a thiocarboxylic acid ester silane coupling agent at 300~500r / min S1: Premix the filler by dry mixing for 5-8 minutes to obtain a premixed filler; S2: Add rubber base material to the premixed filler in step S1, and mix for 5-8 minutes at a first-stage mixing temperature of 80-100℃ and a rotor speed of 80-100 r / min; S3: Add active zinc oxide and stearic acid to the mixture after mixing in step S2, and mix for 5-8 minutes at a second-stage mixing temperature of 110-130℃ and a rotor speed of 60-80 r / min to ensure that the reaction completeness of silane with filler and rubber is ≥95%; S4: Add insoluble sulfur and compounding accelerator to the mixture after mixing in step S3, and mix for 1-2 minutes at a final mixing temperature of 60-70℃ and a rotor speed of 30-50 r / min, and then discharge the rubber to obtain a compounded rubber; S5: Vulcanize the compounded rubber obtained in step S4 at a vulcanization temperature of 140-160℃ and a pressure of 10-18 MPa for 8-15 minutes to obtain a green low rolling resistance tire tread.

[0015] The beneficial effects of this invention are: This application addresses the core contradiction in existing natural rubber-based green low-VOC tire formulations: the difficulty in simultaneously achieving deep VOC emission reduction and improving the interfacial, mechanical, and dynamic properties of the rubber compound. It also resolves issues such as high levels of silane hydrolysis byproducts and residues, poor interfacial bonding and dispersibility between silanes and fillers, the tendency to exacerbate VOC emissions by improving filler agglomeration, insufficient compatibility between the formulation and the reactivity characteristics of silanes, and inadequate process control. Ultimately, it achieves the following results in high-wear-resistant heavy-duty tire tread applications: total VOC emissions ≤0.28 mg / m³, tensile strength ≥29 MPa, tear strength ≥98 kN / m, Akron abrasion ≤0.17 cm³ / 1.61 km; and in green low rolling resistance tire tread applications for new energy vehicles: total VOC emissions ≤0.22 mg / m³, tensile strength ≥28 MPa, tanδ ≤0.10 at 60℃, tanδ ≥0.35 at 0℃, and wet skid resistance meeting EU Tire Labelling Act Class A. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with preferred embodiments.

[0017] The high-purity stearic acid used in the examples is Grade 1 stearic acid, which, according to the purity grade indicators in GB / T 9103-2013, has a total fatty acid content ≥98% and an iodine value ≤2 gI2 / 100g. The preparation method of the thiocarboxylic acid ester silane coupling agent used in the following examples is as follows: S1: In a 50L stainless steel reactor, add 8L of deionized water and 8L of toluene (water:organic solvent volume ratio 1:1), then add 2.2mol of sodium sulfide. The mass-volume ratio of sodium sulfide to the water-toluene mixed solvent is 0.0107 g / mL. Stir until the sodium sulfide is completely dissolved. Then, control the temperature at 25℃±0.5℃ and add 2.0mol of octanoyl chloride dropwise at a rate of 8kg / h. At the same time, add 0.5% of the mass of tetrabutylammonium bromide of octanoyl chloride. After the addition is complete, stir at a constant temperature (25℃±0.5℃) at a speed of 250r / min for 1.5h to obtain sodium thiooctanoate water-organic mixed catalyst solution. S2: Then add 1.0 kg of chloromethylphenylethyltriethoxysilane and 9.0 kg of chloropropyltriethoxysilane (mass ratio 1:9) to the reactor, with a molar ratio of sodium thiooctanoate to chloropropyltriethoxysilane of 1:1.1. Increase the stirring speed to 350 r / min, adjust the pH of the system to 7.5±0.2 with sodium carbonate, and heat to 50℃±0.5℃ at a heating rate of 6℃ / h and react at this temperature for 4h. S3: After the reaction, allow the mixture to stand for 35 minutes and discard the aqueous phase. Wash the organic phase three times with water at a stirring rate of 180 r / min, allowing it to stand for 20 minutes after each wash until the system is neutral. Perform gradient vacuum distillation on the washed organic phase: first, remove low-boiling substances and solvent under vacuum of -0.085 MPa and 75 °C, and then remove trace impurities a second time under vacuum of -0.098 MPa and 90 °C to obtain the thiocarboxylic acid ester silane coupling agent. Example 1

[0018] Heavy-duty tire tread composition: Based on 100 parts of natural rubber (specification SIR20), 55 parts of highly dispersed silica (specification Ultrasil 7000GR), 2.2 parts of complex thiocarboxylic acid ester silane coupling agent, 4.5 parts of active zinc oxide, 1.5 parts of high-purity stearic acid, 1.8 parts of insoluble sulfur, and 0.9 parts of accelerator TBBS are added. The preparation process uses an XM-370 type closed internal mixer; Heavy-duty tire tread preparation: S1: Highly dispersed silica is spray-dried at 120℃ for 2 hours until the moisture content is 0.4%, then premixed with a composite thiocarboxylic acid ester silane coupling agent at a dry rate of 400 r / min for 6 minutes to obtain a premixed filler; S2: Natural rubber base material is added to the premixed filler in step S1, and the mixture is kneaded for 6 minutes at a first-stage kneading temperature of 90℃ and a rotor speed of 90 r / min; S3: Active zinc oxide and stearic acid are added to the mixture after kneading in step S2, and the mixture is kneaded for 7 minutes at a second-stage kneading temperature of 120℃ and a rotor speed of 70 r / min to ensure a silane reaction completion rate of 96%; S4: Insoluble sulfur and accelerator TBBS are added to the mixture after kneading in step S3, and the mixture is kneaded for 1.5 minutes at a final kneading temperature of 65℃ and a rotor speed of 40 r / min. S4: The rubber compound obtained in step S4 is vulcanized at a vulcanization temperature of 150℃ and a pressure of 15MPa for 12 minutes to obtain the tread of heavy-duty tires.

[0019] Total VOC emissions were tested in accordance with VDA 278:2022 and GB / T 39695-2020. Tensile strength testing was conducted according to GB / T 528-2009; Tear strength was tested according to GB / T 529-2008; Akron wear test was performed according to GB / T 1689-2014; Compression set test was conducted according to GB / T 1683-2018; the test results are as follows: The total VOC emissions are 0.26 mg / m³, ethanol byproducts are 0.07 mg / m³, tensile strength is 30.2 MPa, tear strength is 101 kN / m, Akron abrasion is 0.16 cm³ / 1.61 km, and compression set at 100℃ for 24 hours is 18.5%, meeting the requirements for low VOC and high wear resistance heavy-duty tire treads. Example 2

[0020] Heavy-duty tire tread composition: Based on 100 parts of natural rubber (specification SIR20), add 50 parts of highly dispersed silica (specification Ultrasil 7000GR), 1.5 parts of complex thiocarboxylic acid ester silane coupling agent, 4 parts of active zinc oxide, 1 part of high-purity stearic acid, 1.5 parts of insoluble sulfur and 0.8 parts of accelerator TBBS; The preparation process uses an XM-370 type closed internal mixer; Heavy-duty tire tread preparation: S1: Highly dispersed silica is spray-dried at 120℃ for 2 hours until the moisture content is 0.5%, then premixed with a composite thiocarboxylic acid ester silane coupling agent at a dry rate of 300 r / min for 5 minutes to obtain a premixed filler; S2: Natural rubber base material is added to the premixed filler in step S1, and the mixture is kneaded for 5 minutes at a first-stage kneading temperature of 80℃ and a rotor speed of 80 r / min; S3: Active zinc oxide and stearic acid are added to the mixture after kneading in step S2, and the mixture is kneaded for 5 minutes at a second-stage kneading temperature of 110℃ and a rotor speed of 60 r / min to ensure a silane reaction completeness of 95%; S4: Insoluble sulfur and accelerator TBBS are added to the mixture after kneading in step S3, and the mixture is kneaded for 1 minute at a final kneading temperature of 60℃ and a rotor speed of 30 r / min. S4: The rubber compound obtained in step S4 is vulcanized at a vulcanization temperature of 140℃ and a pressure of 10MPa for 8 minutes to obtain the tread of heavy-duty tires.

[0021] Total VOC emissions were tested in accordance with VDA 278:2022 and GB / T 39695-2020. Tensile strength testing was conducted according to GB / T 528-2009; Tear strength was tested according to GB / T 529-2008; Akron wear test was performed according to GB / T 1689-2014; Compression set test was conducted according to GB / T 1683-2018; the test results are as follows: The total VOC emissions are 0.24 mg / m³, ethanol byproducts are 0.06 mg / m³, tensile strength is 29.1 MPa, tear strength is 98 kN / m, Akron abrasion is 0.17 cm³ / 1.61 km, and compression set at 100℃ for 24 hours is 19.2%, meeting the design requirements for low VOC and high wear resistance heavy-duty tire treads. Example 3

[0022] Heavy-duty tire tread composition: Based on 100 parts of natural rubber (specification SIR20), add 60 parts of highly dispersed silica (specification Ultrasil 7000GR), 3.0 parts of complex thiocarboxylic acid ester silane coupling agent, 5 parts of active zinc oxide, 2 parts of high-purity stearic acid, 2.0 parts of insoluble sulfur and 1.0 part of accelerator TBBS; The preparation process uses an XM-370 type closed internal mixer; Heavy-duty tire tread preparation: S1: Highly dispersed silica is spray-dried at 120℃ for 2 hours until the moisture content is 0.4%, then premixed with a composite thiocarboxylic acid ester silane coupling agent at a dry rate of 400 r / min for 6 minutes to obtain a premixed filler; S2: Natural rubber base material is added to the premixed filler in step S1, and the mixture is kneaded for 6 minutes at a first-stage kneading temperature of 90℃ and a rotor speed of 90 r / min; S3: Active zinc oxide and stearic acid are added to the mixture after kneading in step S2, and the mixture is kneaded for 7 minutes at a second-stage kneading temperature of 120℃ and a rotor speed of 70 r / min to ensure a silane reaction completion rate of 97%; S4: Insoluble sulfur and accelerator TBBS are added to the mixture after kneading in step S3, and the mixture is kneaded for 1.5 minutes at a final kneading temperature of 65℃ and a rotor speed of 40 r / min, and then discharged to obtain a compound; S5: The compound obtained in step S4 is vulcanized at a temperature of 150℃ and a pressure of 15 MPa. The tread of a heavy-duty tire is obtained by vulcanizing for 12 minutes under the specified conditions.

[0023] Total VOC emissions were tested in accordance with VDA 278:2022 and GB / T 39695-2020. Tensile strength testing was conducted according to GB / T 528-2009; Tear strength was tested according to GB / T 529-2008; Akron wear test was performed according to GB / T 1689-2014; Compression set test was conducted according to GB / T 1683-2018; the test results are as follows: The total VOC emissions are 0.28 mg / m³, ethanol byproducts are 0.08 mg / m³, tensile strength is 30.5 MPa, tear strength is 102 kN / m, Akron abrasion is 0.15 cm³ / 1.61 km, and compression set at 100℃ for 24 hours is 18.1%, meeting the design requirements for low VOC and high wear resistance heavy-duty tire treads. Example 4

[0024] Heavy-duty tire tread composition: Based on 100 parts of natural rubber (specification SIR20), 55 parts of highly dispersed silica (specification Ultrasil 7000GR), 2.2 parts of complex thiocarboxylic acid ester silane coupling agent, 4.5 parts of active zinc oxide, 1.5 parts of high-purity stearic acid, 1.8 parts of insoluble sulfur, and 0.9 parts of accelerator TBBS are added. The preparation process uses an XM-370 type closed internal mixer; Heavy-duty tire tread preparation: S1: Highly dispersed silica is spray-dried at 120℃ for 2 hours until the moisture content is 0.4%, then premixed with a composite thiocarboxylic acid ester silane coupling agent at a dry rate of 500 r / min for 8 minutes to obtain a premixed filler; S2: Natural rubber base material is added to the premixed filler in step S1, and the mixture is kneaded for 8 minutes at a first-stage kneading temperature of 100℃ and a rotor speed of 100 r / min; S3: Active zinc oxide and stearic acid are added to the mixture after kneading in step S2, and the mixture is kneaded for 8 minutes at a second-stage kneading temperature of 130℃ and a rotor speed of 80 r / min to ensure a silane reaction completeness of 97%; S4: Insoluble sulfur and accelerator TBBS are added to the mixture after kneading in step S3, and the mixture is kneaded for 2 minutes at a final kneading temperature of 70℃ and a rotor speed of 50 r / min (after which the rubber is discharged) to obtain a compound; S5: The compound obtained in step S4 is vulcanized at a temperature of 160℃ and a pressure of 18 MPa. The tread of a heavy-duty tire is obtained by vulcanizing for 15 minutes under the specified conditions.

[0025] Total VOC emissions were tested in accordance with VDA 278:2022 and GB / T 39695-2020. Tensile strength testing was conducted according to GB / T 528-2009; Tear strength was tested according to GB / T 529-2008; Akron wear test was performed according to GB / T 1689-2014; Compression set test was conducted according to GB / T 1683-2018; the test results are as follows: total VOC emissions 0.27 mg / m³, ethanol byproducts 0.07 mg / m³, tensile strength 30.3 MPa, tear strength 101 kN / m, Akron abrasion 0.15 cm³ / 1.61 km, and compression set at 100℃ for 24 hours 18.3%, which meets the design requirements for low VOC and high wear resistance heavy-duty tire tread. Example 5

[0026] Green low rolling resistance tire tread composition: Based on 100 parts of rubber base material (70 parts of natural rubber of specification SIR20 + 30 parts of butadiene rubber of specification BR 9000), 32 parts of highly dispersed silica (specification VN3), 20 parts of low oil absorption carbon black (specification N220), 2.25 parts of composite thiocarboxylic acid ester silane coupling agent, 4.2 parts of active zinc oxide, 1.8 parts of high-purity stearic acid, 1.7 parts of insoluble sulfur, and 1.1 parts of compound accelerator with a CZ to TBBS mass ratio of 5:1; The preparation process uses an XM-270 type closed internal mixer. Preparation of green, low rolling resistance tire tread: S1: Highly dispersed silica and low oil absorption carbon black are spray-dried at 120℃ for 2 hours until the moisture content is 0.3%. They are then dry-mixed with a composite thiocarboxylic acid ester silane coupling agent at a rate of 450 r / min for 7 minutes to obtain a premixed filler. S2: Rubber base material is added to the premixed filler in step S1 and mixed for 7 minutes at a first-stage mixing temperature of 85℃ and a rotor speed of 95 r / min. S3: Active zinc oxide and stearic acid are added to the mixture after mixing in step S2 and mixed for 6 minutes at a second-stage mixing temperature of 115℃ and a rotor speed of 75 r / min. S4: Insoluble sulfur and compound accelerator are added to the mixture after mixing in step S3 and mixed for 1.5 minutes at a final mixing temperature of 68℃ and a rotor speed of 45 r / min before discharge to obtain a compound rubber. S5: The compound rubber obtained in step S4 is vulcanized at a vulcanization temperature of 148℃ and a vulcanization pressure of 16 MPa for 10 minutes to obtain a green low rolling resistance tire tread.

[0027] Total VOC emissions were tested in accordance with VDA 278:2022 and GB / T 39695-2020. Tensile strength testing was conducted according to GB / T 528-2009; Tear strength was tested according to GB / T 529-2008; Akron wear test was performed according to GB / T 1689-2014; Dynamic properties of vulcanized rubber or thermoplastic rubber were tested according to GB / T 9870-2021; the test results are as follows: Total VOC emissions are 0.21 mg / m³, ethanol byproducts are 0.06 mg / m³, tensile strength is 28.8 MPa, tear strength is 97 kN / m, Akron abrasion is 0.14 cm³ / 1.61 km, tanδ at 60℃ is 0.095, and tanδ at 0℃ is 0.36, making it suitable for conventional green tire requirements. Example 6

[0028] Green low rolling resistance tire tread composition: Based on 100 parts of rubber base material (70 parts of natural rubber of specification SIR20 + 30 parts of butadiene rubber of specification BR 9000), 35 parts of highly dispersed silica (specification Ultrasil 7000GR), 20 parts of low oil absorption carbon black (specification N339), 2.75 parts of composite thiocarboxylic acid ester silane coupling agent, 4.5 parts of active zinc oxide, 2.0 parts of high-purity stearic acid, 1.8 parts of insoluble sulfur, and 1.2 parts of compound accelerator with a CZ to TBBS mass ratio of 5:1; The preparation was carried out using an XM-270 type closed internal mixer. Preparation of green, low rolling resistance tire tread: S1: Highly dispersed silica and low oil absorption carbon black are spray-dried at 120℃ for 2 hours until the moisture content is 0.3%. They are then dry-mixed with a composite thiocarboxylic acid ester silane coupling agent at a rate of 500 r / min for 8 minutes to obtain a premixed filler. S2: A rubber base material is added to the premixed filler from step S1, and the mixture is kneaded for 8 minutes at a first-stage mixing temperature of 100℃ and a rotor speed of 100 r / min. S3: Active zinc oxide and stearic acid are added to the mixture from step S2, and the mixture is kneaded for 8 minutes at a second-stage mixing temperature of 130℃ and a rotor speed of 80 r / min. S4: Insoluble sulfur and a compounding accelerator are added to the mixture from step S3, and the mixture is kneaded for 2 minutes at a final temperature of 70℃ and a rotor speed of 50 r / min. S4: The rubber compound obtained in step S4 is vulcanized at a vulcanization temperature of 160℃ and 18MPa for 11 minutes to obtain a green low rolling resistance tire tread.

[0029] Total VOC emissions were tested in accordance with VDA 278:2022 and GB / T 39695-2020. Tensile strength testing was conducted according to GB / T 528-2009; Tear strength was tested according to GB / T 529-2008; Akron wear test was performed according to GB / T 1689-2014; Dynamic performance testing of vulcanized rubber or thermoplastic rubber shall be conducted in accordance with GB / T 9870-2021. The temperature rise and fatigue resistance of vulcanized rubber in the flexural test were tested according to GB / T 1687.1-2016; the test results are as follows: VOC emissions are 0.20 mg / m³, ethanol byproducts are 0.05 mg / m³, tensile strength is 29.5 MPa, tear strength is 99 kN / m, Akron abrasion is 0.13 cm³ / 1.61 km, tanδ=0.090 at 60℃ and tanδ=0.37 at 0℃, dynamic fatigue life is 97.5%, which meets the requirements of low rolling resistance, high safety and long life of new energy vehicles. Example 7

[0030] Green low rolling resistance tire tread composition: Based on 100 parts of rubber base material (65 parts of natural rubber of specification SIR20 + 35 parts of butadiene rubber of specification BR 9000), 30 parts of highly dispersed silica (specification VN3), 20 parts of low oil absorption carbon black (specification N220), 1.5 parts of composite thiocarboxylic acid ester silane coupling agent, 4 parts of active zinc oxide, 1.5 parts of high-purity stearic acid, 1.6 parts of insoluble sulfur, and 1.0 part of compound accelerator with a CZ to TBBS mass ratio of 5:1; The preparation process uses an XM-270 type closed internal mixer. S1: Highly dispersed silica and low oil absorption carbon black are spray-dried at 120℃ for 2 hours until the moisture content is 0.5%, and then premixed with a composite thiocarboxylic acid ester silane coupling agent at a rate of 300 r / min for 5 minutes to obtain a premixed filler; S2: Rubber base material is added to the premixed filler in step S1, and the mixture is mixed for 5 minutes at a first-stage mixing temperature of 80℃ and a rotor speed of 80 r / min; S3: Active zinc oxide and stearic acid are added to the mixture after mixing in step S2, and the mixture is mixed for 5 minutes at a second-stage mixing temperature of 110℃ and a rotor speed of 60 r / min; S4: Insoluble sulfur and compound accelerator are added to the mixture after mixing in step S3, and the mixture is mixed for 1 minute at a final mixing temperature of 60℃ and a rotor speed of 30 r / min, and then discharged to obtain a compound rubber; S5: The compound rubber obtained in step S4 is vulcanized at a vulcanization temperature of 140℃ and a vulcanization pressure of 10 MPa for 8 minutes to obtain a green low rolling resistance tire tread.

[0031] Total VOC emissions were tested in accordance with VDA 278:2022 and GB / T 39695-2020. Tensile strength testing was conducted according to GB / T 528-2009; Tear strength was tested according to GB / T 529-2008; Akron wear test was performed according to GB / T 1689-2014; Dynamic properties of vulcanized rubber or thermoplastic rubber were tested according to GB / T 9870-2021; the test results are as follows: Total VOC emissions are 0.20 mg / m³, ethanol byproducts are 0.05 mg / m³, tensile strength is 28.0 MPa, tear strength is 95 kN / m, Akron abrasion is 0.15 cm³ / 1.61 km, tanδ at 60℃ is 0.098, tanδ at 0℃ is 0.35, and it meets the design requirements for green low rolling resistance tires. Example 8

[0032] Green low rolling resistance tire tread composition: Based on 100 parts of rubber base material (65 parts of natural rubber of specification SIR20 + 35 parts of butadiene rubber of specification BR 9000), 32 parts of highly dispersed silica (specification VN3), 23 parts of low oil absorption carbon black (specification N220), 2.25 parts of composite thiocarboxylic acid ester silane coupling agent, 4.2 parts of active zinc oxide, 1.8 parts of high-purity stearic acid, 1.7 parts of insoluble sulfur, and 1.1 parts of compound accelerator with a CZ to TBBS mass ratio of 5:1; The preparation process uses an XM-270 type closed internal mixer. S1: Highly dispersed silica and low oil absorption carbon black are spray-dried at 120℃ for 2 hours until the moisture content is 0.3%. They are then dry-mixed with a composite thiocarboxylic acid ester silane coupling agent at a rate of 450 r / min for 7 minutes to obtain a premixed filler. S2: A rubber matrix is ​​added to the premixed filler from step S1, and the mixture is kneaded for 7 minutes at a first-stage mixing temperature of 85℃ and a rotor speed of 95 r / min. S3: Active zinc oxide and stearic acid are added to the mixture from step S2, and the mixture is kneaded for 6 minutes at a second-stage mixing temperature of 115℃ and a rotor speed of 75 r / min. S4: Insoluble sulfur and a compounding accelerator are added to the mixture from step S3, and the mixture is kneaded for 1.5 minutes at a final mixing temperature of 68℃ and a rotor speed of 45 r / min before being discharged to obtain a compounded rubber. S5: The compounded rubber obtained in step S4 is vulcanized at a vulcanization temperature of 148℃ and a pressure of 16 MPa for 10 minutes. This results in a green tire tread with low rolling resistance.

[0033] Total VOC emissions were tested in accordance with VDA 278:2022 and GB / T 39695-2020. Tensile strength testing was conducted according to GB / T 528-2009; Tear strength was tested according to GB / T 529-2008; Akron wear test was performed according to GB / T 1689-2014; Dynamic properties of vulcanized rubber or thermoplastic rubber were tested according to GB / T 9870-2021; the test results are as follows: Total VOC emissions are 0.21 mg / m³, ethanol byproducts are 0.06 mg / m³, tensile strength is 28.5 MPa, tear strength is 96 kN / m, Akron abrasion is 0.14 cm³ / 1.61 km, tanδ at 60℃ is 0.096, tanδ at 0℃ is 0.35, and it meets the design requirements for green low rolling resistance tires. Example 9

[0034] Green low rolling resistance tire tread composition: Based on 100 parts of rubber base material (75 parts of natural rubber of specification SIR20 + 25 parts of butadiene rubber of specification BR 9000), 32 parts of highly dispersed silica (specification VN3), 23 parts of low oil absorption carbon black (specification N220), 2.25 parts of composite thiocarboxylic acid ester silane coupling agent, 4.2 parts of active zinc oxide, 1.8 parts of high-purity stearic acid, 1.7 parts of insoluble sulfur, and 1.1 parts of compound accelerator with a CZ to TBBS mass ratio of 5:1; The preparation process uses an XM-270 type closed internal mixer. S1: Highly dispersed silica and low oil absorption carbon black are spray-dried at 120℃ for 2 hours until the moisture content is 0.3%. They are then dry-mixed with a composite thiocarboxylic acid ester silane coupling agent at a rate of 450 r / min for 7 minutes to obtain a premixed filler. S2: A rubber matrix is ​​added to the premixed filler from step S1, and the mixture is kneaded for 7 minutes at a first-stage mixing temperature of 85℃ and a rotor speed of 95 r / min. S3: Active zinc oxide and stearic acid are added to the mixture from step S2, and the mixture is kneaded for 6 minutes at a second-stage mixing temperature of 115℃ and a rotor speed of 75 r / min. S4: Insoluble sulfur and a compounding accelerator are added to the mixture from step S3, and the mixture is kneaded for 1.5 minutes at a final mixing temperature of 68℃ and a rotor speed of 45 r / min before being discharged to obtain a compounded rubber. S5: The compounded rubber obtained in step S4 is vulcanized at a temperature of 148℃ and a pressure of 16 MPa. Under certain conditions, vulcanization for 10 minutes yields a green tire tread with low rolling resistance.

[0035] Total VOC emissions were tested in accordance with VDA 278:2022 and GB / T 39695-2020. Tensile strength testing was conducted according to GB / T 528-2009; Tear strength was tested according to GB / T 529-2008; Akron wear test was performed according to GB / T 1689-2014; Dynamic properties of vulcanized rubber or thermoplastic rubber were tested according to GB / T 9870-2021; the test results are as follows: Total VOC emissions are 0.22 mg / m³, ethanol byproducts are 0.06 mg / m³, tensile strength is 29.0 MPa, tear strength is 98 kN / m, Akron abrasion is 0.13 cm³ / 1.61 km, tanδ at 60℃ is 0.094, tanδ at 0℃ is 0.36, and it meets the design requirements for green low rolling resistance tires.

[0036] Comparative Example 1 (Prior technology, single silane coupling agent system) Based on 100 parts of natural rubber (SIR20), the same amount of raw materials as in Example 1 was used; the only difference in preparation was that the composite thiocarboxylic acid ester silane coupling agent was replaced with 2.2 parts of single Si69 silane coupling agent, and the other conditions were the same as in Example 1.

[0037] The prepared heavy-duty tire tread was tested using the same standards as in Example 1. The total VOC emission of the rubber compound was 0.92 mg / m³, which is in line with the conventional emission of 0.8~1.2 mg / m³ for the Si69 system, but far exceeds the VOC emission of 0.26 mg / m³ in Example 1; the ethanol byproduct was 0.35 mg / m³, which is 5 times that of Example 1; the tensile strength was 24.8 MPa, which is 18% lower than that of Example 1; the tear strength was 82 kN / m, which is 19% lower than that of Example 1; the Akron abrasion was 0.23 cm³ / 1.61 km, which is 44% higher than that of Example 1; and the compression set at 100℃ for 24 h was 25.3%, which is 37% higher than that of Example 1. In summary, all the performance data of Comparative Example 1 are significantly worse than those of Example 1, and it cannot meet the requirements for low VOC and high wear-resistant tire treads. It is evident that this invention achieves the technical advantages of simultaneously improving the comprehensive performance of rubber compounds through the application of composite silane coupling agents, precise formulation design, and synergistic process control, thereby realizing deep VOC emission reduction.

[0038] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also within the protection scope of the present invention.

Claims

1. The application of a thiocarboxylic acid ester silane coupling agent, characterized in that, The thiocarboxylic acid ester silane coupling agent is used for the modification of rubber substrates.

2. The application according to claim 1, characterized in that, The preparation method of the thiocarboxylic acid ester silane coupling agent is as follows: S1: Mix deionized water with an organic solvent to prepare a water-organic mixed solvent; add sodium sulfide to the water-organic mixed solvent and stir until there are no solid particles, then add phase transfer catalyst and add octanoyl chloride dropwise. After the addition is complete, stir twice to obtain sodium thiooctanoate water-organic mixed catalyst solution. S2: Add chloromethylphenylethyltriethoxysilane and chloropropyltriethoxysilane to the sodium thiooctanoate aqueous-organic mixed catalyst solution obtained in S1; then adjust the pH of the system to weakly alkaline, increase the stirring rate, and stir the reaction at a constant temperature after heating. S3: After the reaction in step S2 is completed, the reaction solution is allowed to stand and the organic phase is separated. The organic phase is washed until neutral. The organic phase after water washing is subjected to gradient vacuum distillation to obtain chloromethylphenethyltriethoxysilane-NTX silane composite thiocarboxylic acid ester silane coupling agent.

3. The application according to claim 1, characterized in that, The application of the thiocarboxylic acid ester silane coupling agent in the tread of heavy-duty tires, wherein the composition of the heavy-duty tire tread includes: 100 parts of natural rubber base material, 50-60 parts of highly dispersed silica, 1.5-3.0 parts of thiocarboxylic acid ester silane coupling agent, 4-5 parts of active zinc oxide, 1-2 parts of stearic acid, 1.5-2.0 parts of insoluble sulfur, and 0.8-1.0 parts of accelerator TBBS.

4. The application according to claim 3, characterized in that, The specific steps for preparing the heavy-duty tire tread are as follows: S1: After spray drying the highly dispersed silica at 120°C for 2 hours, it is dry-mixed with the thiocarboxylic acid ester silane coupling agent at a rate of 300~500 r / min for 5~8 minutes to obtain the premixed filler; S2: Add natural rubber base material to the premixed filler in step S1, and mix for 5-8 minutes at a first-stage mixing temperature of 80-100℃ and a rotor speed of 80-100 r / min; S3: Add active zinc oxide and stearic acid to the mixture after mixing in step S2, and mix for 5-8 minutes at a second-stage mixing temperature of 110-130℃ and a rotor speed of 60-80 r / min; S4: Add insoluble sulfur and accelerator TBBS to the mixture after mixing in step S3, and mix for 1-2 minutes at a final mixing temperature of 60-70℃ and a rotor speed of 30-50 r / min, then discharge the rubber to obtain the compounded rubber; S5: The rubber compound obtained in step S4 is vulcanized at a vulcanization temperature of 140~160℃ and a pressure of 10~18MPa for 8~15 minutes to obtain the tread of heavy-duty tires.

5. The application according to claim 1, characterized in that, The application of the thiocarboxylic acid ester silane coupling agent in the green low rolling resistance tire tread comprises: 100 parts of rubber base material, 50-55 parts of carbon black, 1.5-2.75 parts of thiocarboxylic acid ester silane coupling agent, 4-4.5 parts of active zinc oxide, 1.5-2.0 parts of stearic acid, 1.6-1.8 parts of insoluble sulfur, and 1.0-1.2 parts of compounding accelerator.

6. The application according to claim 5, characterized in that, The rubber base material is composed of natural rubber and butadiene rubber, with 65-75 parts of natural rubber and 25-35 parts of butadiene rubber; the carbon black is composed of highly dispersed silica and low oil absorption carbon black, with 30-35 parts of highly dispersed silica and 20-25 parts of low oil absorption carbon black; the compound accelerator is composed of accelerator CZ and accelerator TBBS.

7. The application according to claim 5, characterized in that, The specific steps for preparing the green low rolling resistance tire tread are as follows: S1: After the carbon black is spray-dried at 120°C for 2 hours, it is dry-mixed with the thiocarboxylic acid ester silane coupling agent at a rate of 300~500 r / min for 5~8 minutes to obtain the premixed filler. S2: Add rubber base material to the premixed filler in step S1, and mix for 5-8 minutes at a first-stage mixing temperature of 80-100℃ and a rotor speed of 80-100 r / min; S3: Add active zinc oxide and stearic acid to the mixture after mixing in step S2, and mix for 5-8 minutes at a second-stage mixing temperature of 110-130℃ and a rotor speed of 60-80 r / min; S4: Add insoluble sulfur and compounding accelerator to the mixture after mixing in step S3, and mix for 1-2 minutes at a final mixing temperature of 60-70℃ and a rotor speed of 30-50 r / min, then discharge the rubber to obtain the compounded rubber; S5: The rubber compound obtained in step S4 is vulcanized at a vulcanization temperature of 140~160℃ and a pressure of 10~18MP for 8~15 minutes to obtain a green low rolling resistance tire tread.