Preparation method of tread rubber

Abstract

The invention discloses a preparation method of tread rubber, and belongs to the field of rubber processing. The preparation method comprises the following steps: pretreating aramid pulp, a coupling agent and a lubricant, and then adding the pretreated aramid pulp, the coupling agent and the lubricant into natural rubber to prepare aramid pulp master batch particles; the obtained aramid pulp master batch particles are added into raw materials for preparing tread rubber, and the prepared rubber material has excellent mechanical properties, wear resistance and low rolling resistance. According to the method, the dispersity and interface combination of the aramid pulp in the rubber are remarkably optimized, the comprehensive improvement of the mechanical property, the wear resistance and the rolling resistance of the tread rubber is realized, and the tread rubber has outstanding industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of rubber processing, and specifically relates to a method for preparing tire tread rubber. Background Technology

[0002] As the part that directly contacts the road surface, the performance of the tread compound directly affects the tire's wear resistance, wet skid resistance, rolling resistance, and service life. With the rapid development of the automotive industry, the requirements for the comprehensive performance of tires are becoming increasingly stringent. Furthermore, in the tire manufacturing field, there is a concept known as the "devil's triangle," which refers to the fact that tire wear resistance, wet skid resistance, and rolling resistance cannot be improved simultaneously due to their inherent properties. Especially under the trend of energy conservation and environmental protection, balancing low rolling resistance, high wear resistance, and good wet skid resistance has become a key challenge in tread compound research and development.

[0003] Aramid pulp, as a fiber filler with high chemical stability, thermal stability, high mechanical properties and wear resistance, produces tread rubber with excellent mechanical properties and durability when added to a natural rubber matrix, thus improving the service life of the tread rubber.

[0004] However, due to the highly fibrillated structure of aramid pulp, it is difficult to disperse in the rubber matrix, and the low surface chemical activity of aramid pulp leads to poor interfacial interaction with the rubber matrix, which limits the effectiveness of aramid pulp in reinforcing the rubber matrix. To solve these problems, it is necessary to comprehensively improve the compatibility between the reinforcing filler aramid pulp and the matrix rubber material by improving both the dispersibility of aramid pulp in the matrix and the interfacial strength between the two phases of the aramid pulp / rubber composite.

[0005] Chinese patent document CN105273208A discloses a method for preparing aramid pulp masterbatch. This method involves stirring aramid pulp, a dispersing agent, and an adhesive resin in a high-speed mixer to obtain surface-modified aramid pulp. The modified aramid pulp composite is then premixed with a rubber matrix on an open mill to obtain premixed aramid pulp masterbatch. The premixed aramid pulp masterbatch is then subjected to twin-screw extrusion, granulation, and packaging to complete the preparation of the aramid pulp masterbatch. However, this method only physically mixes the aramid pulp composite with the rubber matrix using an open mill. The rubber matrix cannot fully penetrate the fine structure of the aramid pulp, resulting in uneven dispersion of the aramid pulp within the rubber matrix.

[0006] Chinese patent document CN106832611A discloses a method for preparing highly active finely dispersed aramid pulp masterbatch granules. The method involves premixing aramid pulp with a pretreatment composition to uniformly coat and isolate the surface of the submicron short fibers of aramid pulp with the in-situ modifying agent (coupling agent) and the penetrating isolation agent in the pretreatment composition, thereby obtaining an aramid pulp composite; (2) mixing and dispersing the aramid pulp composite with a rubber carrier in a mixer or an open mixing mill to obtain aramid pulp masterbatch; (3) heat-treating the aramid pulp masterbatch in a mixer or a hot roller to further isolate the submicron short fibers of aramid pulp; (4) granulating the heat-treated aramid pulp masterbatch through a single-screw extrusion granulation system to obtain highly active finely dispersed aramid pulp masterbatch granules with an aramid pulp content of 30-50%. However, this method uses polyisobutylene resin as a permeation separator, which will worsen its compatibility with the rubber matrix in subsequent rubber processing. Furthermore, the high content of additives in the aramid pulp masterbatch is detrimental to the preparation and processing of rubber products. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing tread rubber. Through a two-step modification process and a masterbatch preparation method, the dispersibility and interfacial bonding of aramid pulp in rubber can be significantly optimized, thereby achieving a comprehensive improvement in the mechanical properties, wear resistance, and rolling resistance of the tread rubber, and possessing outstanding industrial application value.

[0008] To achieve this objective, the technical solution of the present invention is a method for preparing tread rubber, comprising the following steps: (1) Add aramid pulp and coupling agent to a mixer at 70~90℃ and mix for 3~7 min to obtain primary modified aramid pulp. The coupling agent is a silane coupling agent and the mass ratio of aramid pulp to coupling agent is 100:6~10. (2) Add lubricant to the primary modified aramid pulp obtained in step (1) and mix at 70~90℃ for 3~7 min to obtain secondary modified aramid pulp. The lubricant is a pentaerythritol ester compound, and the mass ratio of aramid pulp to lubricant is 100:8~12. (3) Place the secondary modified aramid pulp obtained in step (2) into a mixer, control the initial temperature of the mixer to be 90~110℃, add natural rubber in three equal amounts in three batches, and mix for 2~4 minutes each time to obtain aramid pulp masterbatch particles. The mass ratio of aramid pulp to natural rubber is 100:100~120. (4) Natural rubber, butadiene rubber, zinc oxide, stearic acid, antioxidant, carbon black, aramid pulp masterbatch, and anti-sulfurization reversion agent are mixed in an intensive kneading process, and then removed and left to stand to obtain a section of masterbatch. (5) Mix the first stage masterbatch, accelerator, sulfur and anti-scorching agent in an intensive kneading process, and then remove and let stand to obtain the second stage masterbatch; (6) The second stage masterbatch is subjected to open refining to obtain compound rubber, which is then placed at 20~30℃ for 12~48h; (7) The compound rubber is vulcanized to obtain tread rubber.

[0009] Preferably, the coupling agent in step (1) is one of vinyltrimethoxysilane (A171), vinyltriethoxysilane (A151), or γ-methacryloyloxypropyltrimethoxysilane (KH-570), and the mass ratio of aramid pulp to coupling agent is 100:6~10.

[0010] Preferably, in step (2), the lubricant is one of pentaerythritol ester or pentaerythritol tetrabenzoate, and the mass ratio of aramid pulp to lubricant is 100:8~12.

[0011] Preferably, in step (3), the mixing time after each addition of natural rubber is controlled to be 2-4 minutes, and the mass ratio of aramid pulp to natural rubber is 100:100-120.

[0012] Preferably, in step (4), the mass ratio of natural rubber, butadiene rubber, zinc oxide, stearic acid, antioxidant, carbon black, aramid pulp masterbatch, and anti-reversion agent is controlled to be 70~90:10~30:3~7:1~5:3~7:30~70:10~16, 0.5~1.5; the antioxidant is one or more of antioxidant 4020, antioxidant RD, antioxidant 4010, and antioxidant 4010NA; the filler is one of carbon black N330, carbon black N550, and carbon black N234; and the anti-reversion agent is one of 1,3-bis(citronamidomethyl)benzene (PK-900), N,N'-m-phenylenebismaleimide (HVA-2), and sodium hexyl sulfate (HTS).

[0013] Preferably, in step (5), the mass ratio of natural rubber, accelerator, sulfur, and scorch inhibitor is controlled to be 127.5~226.5:1~3:1.4~2.0:0.1~0.3; the accelerator is one of accelerator DM, accelerator M, accelerator CZ, accelerator DZ, and accelerator NOBS; the scorch inhibitor is one of cytosine triphosphate (CTP), dithiophosphate trimer (DTPP), and hexamethylenetetramine (HT).

[0014] The beneficial effects of the present invention are as follows: (1) Through the present invention, the dispersion and interfacial bonding of aramid pulp in rubber are significantly optimized by a two-step modification process and a masterbatch preparation method. The prepared tread rubber has good mechanical strength, wear resistance and low rolling resistance. Its mechanical properties (tensile strength) can be increased by 17.0% and 10.9% compared with the tread rubber materials prepared without adding aramid pulp and directly adding aramid pulp (without preparing aramid pulp masterbatch), respectively. The wear resistance can be increased by 14.7% and 11.0%, respectively. The rolling resistance is also significantly reduced, which can be reduced by 26.7% and 15.4% compared with the tread rubber materials prepared without adding aramid pulp and directly adding aramid pulp (without preparing aramid pulp masterbatch). By avoiding fiber entanglement through staged mixing, the aramid pulp in the masterbatch is evenly dispersed and can be used for a long time in the service environment. (2) Through this invention, the problem of dispersion difficulty caused by the fibrillated structure of aramid pulp is solved by synergistic modification of coupling agent and lubricant, and the interfacial bonding strength between fiber and rubber matrix is ​​increased by more than 30%. (3) Through this invention, by adding lubricant, the microstructure can be optimized and the surface of aramid pulp can be lubricated to reduce the friction between fibers. Then, in the subsequent addition of natural rubber, natural rubber can fully penetrate into the fine structure of aramid pulp, and isolate the ultrafine short fibers of aramid pulp to obtain aramid pulp composite. In this way, the problem of the microfibers of pulp being entangled and difficult to loosen and isolate is solved, and the microfibers of aramid pulp can be fully extended, thereby optimizing the microfiber structure. (4) Through this invention, due to the introduction of aramid pulp, the toughness of the fiber can delay the crack propagation of rubber under dynamic load and improve fatigue resistance; the thermal decomposition temperature of aramid pulp is as high as 500°C or above, which can significantly improve the dimensional stability and mechanical property retention rate of natural rubber in high temperature environment; reduce the hardening or embrittlement of rubber caused by thermo-oxidative aging; aramid is resistant to acids, alkalis and organic solvents, which can improve the rubber's tolerance in corrosive environments; aramid itself has flame retardancy and electrical insulation; it can enable the tread rubber to be used under extremely harsh conditions. Detailed Implementation

[0015] In the description of this invention, it should be noted that unless specific conditions are specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. The mixer used in this invention is a LABSTAR® high-speed shear mixer manufactured by NETZSCH (Germany), with a capacity of 0.1~5L, a speed range of 100~10000 rpm, and a power of 2.2kW. The internal mixer is an XM-0.5L micro internal mixer manufactured by Shanghai Rubber Machinery Factory, with a capacity of 0.5L and a rotor speed of 30~80 rpm. Other reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0016] The technical solutions provided by the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0017] 100g of aramid pulp and 8g of coupling agent A171 were added to a mixer. The mixer speed was adjusted to 1500rpm and the temperature was raised to 80℃ for 5 minutes to obtain primary modified aramid pulp. Then, 10g of pentaerythritol ester was added, the mixer speed was adjusted to 2000rpm, and the mixture was continued for 5 minutes to fully lubricate the surface of the aramid pulp. The pulp was then removed to obtain secondary modified aramid pulp. The modified aramid pulp was added to a mixer. The initial temperature of the mixer was adjusted to 100℃ and the rotor speed was 60rpm. Then, 110g of natural rubber was added in three equal portions. After each addition of natural rubber, the mixture was stirred for 3 minutes to obtain aramid pulp masterbatch. Add 80g of natural rubber, 20g of butadiene rubber, 5g of zinc oxide, 2.5g of stearic acid, 2g of antioxidant RD, 3g of antioxidant 4020, 50g of carbon black N234, 12g of aramid pulp masterbatch granules, and 1g of anti-sulfurization reversion agent PK-900 to a mixer. Adjust the starting temperature of the mixer to 60℃ and the rotor speed to 60rpm. After mixing for 12 minutes, remove the mixture and let it stand for 4 hours to obtain 175.5g of masterbatch. Add 175.5g of first-stage masterbatch rubber, 2g of accelerator CZ, 1.8g of sulfur, and 0.2g of anti-scorching agent CTP to an internal mixer. Adjust the initial temperature of the internal mixer to 60℃ and the rotor speed to 60rpm. After mixing for 8 minutes, remove the mixture and let it stand for 4 hours to obtain 179.5g of second-stage masterbatch rubber. The two-stage masterbatch was subjected to open mixing to obtain the compounded rubber, which was then placed at 25°C in the dark for 24 hours. The compounded rubber, after being left to stand, was subjected to a vulcanization reaction at 150℃, 10MPa, and t90 time as measured by MDR, to obtain the tread rubber. Example 2

[0018] 100g of aramid pulp and 6g of coupling agent A151 were added to a mixer. The mixer speed was adjusted to 1500rpm, and the temperature was raised to 70℃ for 3 minutes to obtain primary modified aramid pulp. Then, 8g of pentaerythritol ester was added, the mixer speed was adjusted to 2000rpm, and the mixture was continued for 3 minutes to fully lubricate the surface of the aramid pulp. The pulp was then removed to obtain secondary modified aramid pulp. The modified aramid pulp was added to a mixer, the initial temperature of the mixer was adjusted to 90℃ and the rotor speed was 60rpm, and then 100g of natural rubber was added in three equal portions. After each addition of natural rubber, the mixture was stirred for 2 minutes to obtain aramid pulp masterbatch. Add 70g of natural rubber, 10g of nitrile rubber, 3g of zinc oxide, 1g of stearic acid, 1g of antioxidant RD, 2g of antioxidant 4010, 30g of carbon black N550, 10g of aramid pulp masterbatch granules, and 0.5g of anti-sulfurization reversion agent HVA-2 to a mixer. Adjust the starting temperature of the mixer to 60℃ and the rotor speed to 60rpm. After mixing for 12 minutes, remove the mixture and let it stand for 4 hours to obtain 127.5g of first-stage masterbatch. Add 127.5g of first-stage masterbatch rubber, 1g of accelerator DM, 1.4g of sulfur, and 0.1g of scorching inhibitor DTPP to an internal mixer. Adjust the initial temperature of the internal mixer to 60℃ and the rotor speed to 60rpm. Mix for 8 minutes and then remove the mixture. After standing for 4 hours, 130g of second-stage masterbatch rubber is obtained. The two-stage masterbatch was subjected to open mixing to obtain the compounded rubber, which was then placed at 20°C in the dark for 12 hours. The compounded rubber, after being left to stand, was subjected to a vulcanization reaction at 150℃, 10MPa, and t90 time as measured by MDR, to obtain the tread rubber. Example 3

[0019] 100g of aramid pulp and 10g of coupling agent KH-570 were added to a mixer. The mixer speed was adjusted to 1500rpm, and the mixture was heated to 90℃ and mixed for 7 minutes to obtain primary modified aramid pulp. Then, 12g of pentaerythritol tetrabenzoate was added, and the mixer speed was adjusted to 2000rpm and the mixture was mixed for 7 minutes to fully lubricate the surface of the aramid pulp. The pulp was then removed to obtain secondary modified aramid pulp. The modified aramid pulp was added to a mixer. The initial temperature of the mixer was adjusted to 90℃ and the rotor speed was 60rpm. Then, 120g of natural rubber was added in three equal portions. After each addition of natural rubber, the mixture was mixed for 4 minutes. The aramid pulp masterbatch was then obtained. Add 90g of natural rubber, 30g of butadiene rubber, 7g of zinc oxide, 5g of stearic acid, 3g of antioxidant RD, 4g of antioxidant 4010NA, 70g of carbon black N330, 16g of aramid pulp masterbatch granules, and 1.5g of anti-sulfurization reversion agent HTS to a mixer. Adjust the starting temperature of the mixer to 60℃ and the rotor speed to 60rpm. After mixing for 12 minutes, remove the mixture and let it stand for 4 hours to obtain 226.5g of first-stage masterbatch. Add 226.5g of first-stage masterbatch rubber, 3g of accelerator M, 2g of sulfur, and 0.3g of anti-scorching agent HT to an internal mixer. Adjust the initial temperature of the internal mixer to 60℃ and the rotor speed to 60rpm. Mix for 12 minutes and then remove the mixture. After standing for 4 hours, 231.8g of second-stage masterbatch rubber is obtained. The two-stage masterbatch was subjected to open mixing to obtain the compounded rubber, which was then placed at 30°C in the dark for 48 hours. The compounded rubber, after being left to stand, was subjected to a vulcanization reaction at 150℃, 10MPa, and t90 time as measured by MDR, to obtain the tread rubber. Example 4

[0020] 100g of aramid pulp and 8g of coupling agent A171 were added to a mixer. The mixer speed was adjusted to 1500rpm, and the temperature was raised to 80℃ for 5 minutes to obtain primary modified aramid pulp. Then, 10g of pentaerythritol ester was added and the mixer speed was adjusted to 2000rpm. The mixture was continued for 5 minutes to fully lubricate the surface of the aramid pulp. The pulp was then removed to obtain secondary modified aramid pulp. The modified aramid pulp was added to a mixer. The initial temperature of the mixer was adjusted to 100℃ and the rotor speed was 60rpm. Then, 110g of natural rubber was added in three equal portions. After each addition of natural rubber, the mixture was stirred for 3 minutes to obtain aramid pulp masterbatch. Add 80g of natural rubber, 20g of butadiene rubber, 5g of zinc oxide, 2.5g of stearic acid, 2g of antioxidant RD, 3g of antioxidant 4020, 50g of carbon black N234, 12g of aramid pulp masterbatch granules, and 1g of anti-sulfurization reversion agent PK-900 to a mixer. Adjust the starting temperature of the mixer to 60℃ and the rotor speed to 60rpm. After mixing for 12 minutes, remove the mixture and let it stand for 4 hours to obtain 175.5g of masterbatch. Add 175.5g of first-stage masterbatch rubber, 2g of accelerator DZ, 1.8g of sulfur, and 0.2g of anti-scorching agent CTP to an internal mixer. Adjust the initial temperature of the internal mixer to 60℃ and the rotor speed to 60rpm. After mixing for 8 minutes, remove the mixture and let it stand for 4 hours to obtain 179.5g of second-stage masterbatch rubber. The two-stage masterbatch was subjected to open mixing to obtain the compounded rubber, which was then placed at 25°C in the dark for 24 hours. The compounded rubber, after being left to stand, was subjected to a vulcanization reaction at 150℃, 10MPa, and t90 time as measured by MDR, to obtain the tread rubber. Example 5

[0021] 100g of aramid pulp and 8g of coupling agent A171 were added to a mixer. The mixer speed was adjusted to 1500rpm and the temperature was raised to 80℃ for 5 minutes to obtain primary modified aramid pulp. Then, 10g of pentaerythritol ester was added, the mixer speed was adjusted to 2000rpm, and the mixture was continued for 5 minutes to fully lubricate the surface of the aramid pulp. The pulp was then removed to obtain secondary modified aramid pulp. The modified aramid pulp was added to a mixer. The initial temperature of the mixer was adjusted to 100℃ and the rotor speed was 60rpm. Then, 110g of natural rubber was added in three equal portions. After each addition of natural rubber, the mixture was stirred for 3 minutes to obtain aramid pulp masterbatch. Add 80g of natural rubber, 20g of butadiene rubber, 5g of zinc oxide, 2.5g of stearic acid, 2g of antioxidant RD, 3g of antioxidant 4020, 50g of carbon black N234, 12g of aramid pulp masterbatch granules, and 1g of anti-sulfurization reversion agent PK-900 to a mixer. Adjust the starting temperature of the mixer to 60℃ and the rotor speed to 60rpm. After mixing for 12 minutes, remove the mixture and let it stand for 4 hours to obtain 175.5g of masterbatch. Add 175.5g of first-stage masterbatch rubber, 2g of accelerator NOBS, 1.8g of sulfur, and 0.2g of anti-scorching agent CTP to an internal mixer. Adjust the initial temperature of the internal mixer to 60℃ and the rotor speed to 60rpm. Mix for 8 minutes and then remove the mixture. After standing for 4 hours, 179.5g of second-stage masterbatch rubber is obtained. The two-stage masterbatch was subjected to open mixing to obtain the compounded rubber, which was then placed at 25°C in the dark for 24 hours. The compounded rubber, after being left to stand, was subjected to a vulcanization reaction at 150℃, 10MPa, and t90 time as measured by MDR, to obtain the tread rubber. Comparative Example 1

[0022] Add 80g of natural rubber, 20g of butadiene rubber, 5g of zinc oxide, 2.5g of stearic acid, 2g of antioxidant RD, 3g of antioxidant 4020, 50g of carbon black N234, and 1g of anti-sulfurization reversion agent PK-900 to a mixer. Adjust the starting temperature of the mixer to 60℃ and the rotor speed to 60rpm. After mixing for 12 minutes, remove the mixture and let it stand for 4 hours to obtain 163.5g of masterbatch. Add 163.5g of first-stage masterbatch rubber, 2g of accelerator NOBS, 1.8g of sulfur, and 0.2g of anti-scorching agent CTP to an internal mixer. Adjust the initial temperature of the internal mixer to 60℃ and the rotor speed to 60rpm. After mixing for 8 minutes, remove the mixture and let it stand for 4 hours to obtain 167.5g of second-stage masterbatch rubber. The two-stage masterbatch was subjected to open mixing to obtain the compounded rubber, which was then placed at 25°C in the dark for 24 hours. The compounded rubber, after being left to stand, was subjected to a vulcanization reaction at 150℃, 10MPa, and t90 time as measured by MDR, to obtain the tread rubber. Contrast agent 2

[0023] Add 80g of natural rubber, 20g of butadiene rubber, 5g of zinc oxide, 2.5g of stearic acid, 2g of antioxidant RD, 3g of antioxidant 4020, 50g of carbon black N234, 5.263g of aramid pulp, and 1g of anti-sulfurization reversion agent PK-900 to a mixer. Adjust the starting temperature of the mixer to 60℃ and the rotor speed to 60rpm. After mixing for 12 minutes, remove the mixture and let it stand for 4 hours to obtain 168.763g of masterbatch. Add 168.763g of first-stage masterbatch rubber, 2g of accelerator NOBS, 1.8g of sulfur, and 0.2g of anti-scorching agent CTP to an internal mixer. Adjust the initial temperature of the internal mixer to 60℃ and the rotor speed to 60rpm. After mixing for 8 minutes, remove the mixture and let it stand for 4 hours to obtain 172.763g of second-stage masterbatch rubber. The two-stage masterbatch was subjected to open mixing to obtain the compounded rubber, which was then placed at 25°C in the dark for 24 hours. The compounded rubber, after being left to stand, was subjected to a vulcanization reaction at 150℃, 10MPa, and t90 time as measured by MDR, to obtain the tread rubber. Comparative Example 3

[0024] 100g of aramid pulp and 8g of coupling agent A171 were added to a mixer. The mixer speed was adjusted to 1500rpm, and the temperature was raised to 80℃ for 5 minutes to obtain primary modified aramid pulp. Then, 4g of pentaerythritol ester was added, the mixer speed was adjusted to 2000rpm, and the mixture was continued for 5 minutes to fully lubricate the surface of the aramid pulp. The pulp was then removed to obtain secondary modified aramid pulp. The modified aramid pulp was added to a mixer. The initial temperature of the mixer was adjusted to 100℃ and the rotor speed was 60rpm. Then, 110g of natural rubber was added in three equal portions. After each addition of natural rubber, the mixture was stirred for 3 minutes to obtain aramid pulp masterbatch. Add 80g of natural rubber, 20g of butadiene rubber, 5g of zinc oxide, 2.5g of stearic acid, 2g of antioxidant RD, 3g of antioxidant 4020, 50g of carbon black N234, 12g of aramid pulp masterbatch granules, and 1g of anti-sulfurization reversion agent PK-900 to a mixer. Adjust the starting temperature of the mixer to 60℃ and the rotor speed to 60rpm. After mixing for 12 minutes, remove the mixture and let it stand for 4 hours to obtain 175.5g of masterbatch. Add 175.5g of first-stage masterbatch rubber, 2g of accelerator CZ, 1.8g of sulfur, and 0.2g of anti-scorching agent CTP to an internal mixer. Adjust the initial temperature of the internal mixer to 60℃ and the rotor speed to 60rpm. After mixing for 8 minutes, remove the mixture and let it stand for 4 hours to obtain 179.5g of second-stage masterbatch rubber. The two-stage masterbatch was subjected to open mixing to obtain the compounded rubber, which was then placed at 25°C in the dark for 24 hours. The compounded rubber, after being left to stand, was subjected to a vulcanization reaction at 150℃, 10MPa, and t90 time as measured by MDR, to obtain the tread rubber. Comparative Example 4

[0025] 100g of aramid pulp and 8g of coupling agent A171 were added to a mixer. The mixer speed was adjusted to 1500rpm and the temperature was raised to 80℃ for 5 minutes to obtain primary modified aramid pulp. Then, 16g of pentaerythritol ester was added, the mixer speed was adjusted to 2000rpm, and the mixture was continued for 5 minutes to fully lubricate the surface of the aramid pulp. The pulp was then removed to obtain secondary modified aramid pulp. The modified aramid pulp was added to a mixer. The initial temperature of the mixer was adjusted to 100℃ and the rotor speed was 60rpm. Then, 110g of natural rubber was added in three equal portions. After each addition of natural rubber, the mixture was stirred for 3 minutes to obtain aramid pulp masterbatch. Add 80g of natural rubber, 20g of butadiene rubber, 5g of zinc oxide, 2.5g of stearic acid, 2g of antioxidant RD, 3g of antioxidant 4020, 50g of carbon black N234, 12g of aramid pulp masterbatch granules, and 1g of anti-sulfurization reversion agent PK-900 to a mixer. Adjust the starting temperature of the mixer to 60℃ and the rotor speed to 60rpm. After mixing for 12 minutes, remove the mixture and let it stand for 4 hours to obtain 175.5g of masterbatch. Add 175.5g of first-stage masterbatch rubber, 2g of accelerator CZ, 1.8g of sulfur, and 0.2g of anti-scorching agent CTP to an internal mixer. Adjust the initial temperature of the internal mixer to 60℃ and the rotor speed to 60rpm. Mix for 8 minutes and then remove the mixture. After standing for 4 hours, 179.5g of second-stage masterbatch rubber is obtained. The two-stage masterbatch was subjected to open mixing to obtain the compounded rubber, which was then placed at 25°C in the dark for 24 hours. The compounded rubber, after being left to stand, was subjected to a vulcanization reaction at 150℃, 10MPa, and t90 time as measured by MDR, to obtain the tread rubber. Comparative Example 5

[0026] Add 100g of aramid pulp and 10g of pentaerythritol ester to a mixer, adjust the mixer speed to 2000rpm, heat to 80℃ and mix for 5min, and take out to obtain a modified aramid pulp. The modified aramid pulp was added to a mixer. The initial temperature of the mixer was adjusted to 100℃ and the rotor speed was 60rpm. Then, 110g of natural rubber was added in three equal portions. After each addition of natural rubber, the mixture was stirred for 3 minutes to obtain aramid pulp masterbatch. Add 80g of natural rubber, 20g of butadiene rubber, 5g of zinc oxide, 2.5g of stearic acid, 2g of antioxidant RD, 3g of antioxidant 4020, 50g of carbon black N234, 12g of aramid pulp masterbatch granules, and 1g of anti-sulfurization reversion agent PK-900 to a mixer. Adjust the starting temperature of the mixer to 60℃ and the rotor speed to 60rpm. After mixing for 12 minutes, remove the mixture and let it stand for 4 hours to obtain 175.5g of masterbatch. Add 175.5g of first-stage masterbatch rubber, 2g of accelerator CZ, 1.8g of sulfur, and 0.2g of anti-scorching agent CTP to an internal mixer. Adjust the initial temperature of the internal mixer to 60℃ and the rotor speed to 60rpm. After mixing for 8 minutes, remove the mixture and let it stand for 4 hours to obtain 179.5g of second-stage masterbatch rubber. The two-stage masterbatch was subjected to open mixing to obtain the compounded rubber, which was then placed at 25°C in the dark for 24 hours. The compounded rubber, after being left to stand, was subjected to a vulcanization reaction at 150℃, 10MPa, and t90 time as measured by MDR, to obtain the tread rubber. Comparative Example 6

[0027] Add 100g of aramid pulp and 8g of coupling agent A171 to a mixer, adjust the mixer speed to 1500rpm, heat to 80℃ and mix for 5min to obtain a modified aramid pulp. The modified aramid pulp was added to a mixer. The initial temperature of the mixer was adjusted to 100℃ and the rotor speed was 60rpm. Then, 110g of natural rubber was added in three equal portions. After each addition of natural rubber, the mixture was stirred for 3 minutes to obtain aramid pulp masterbatch. Add 80g of natural rubber, 20g of butadiene rubber, 5g of zinc oxide, 2.5g of stearic acid, 2g of antioxidant RD, 3g of antioxidant 4020, 50g of carbon black N234, 12g of aramid pulp masterbatch granules, and 1g of anti-sulfurization reversion agent PK-900 to a mixer. Adjust the starting temperature of the mixer to 60℃ and the rotor speed to 60rpm. After mixing for 12 minutes, remove the mixture and let it stand for 4 hours to obtain 175.5g of masterbatch. Add 175.5g of first-stage masterbatch rubber, 2g of accelerator CZ, 1.8g of sulfur, and 0.2g of anti-scorching agent CTP to an internal mixer. Adjust the initial temperature of the internal mixer to 60℃ and the rotor speed to 60rpm. Mix for 8 minutes and then remove the mixture. After standing for 4 hours, 179.5g of second-stage masterbatch rubber is obtained. The two-stage masterbatch was subjected to open mixing to obtain the compounded rubber, which was then placed at 25°C in the dark for 24 hours. The compounded rubber, after being left to stand, was subjected to a vulcanization reaction at 150℃, 10MPa, and t90 time as measured by MDR, to obtain the tread rubber. Experimental Example 1

[0028] The corresponding performance tests were conducted according to the equipment and testing methods described below, as shown in Table 1:

[0029] DMA testing: Measured using a DMA2422 dynamic mechanical analyzer manufactured by NETZSCH GmbH, Germany. The test adopted a double cantilever beam mode, with a maximum dynamic load of 2N, a maximum amplitude of 120μm, a frequency of 1HZ, a temperature range of -100~100℃, and a heating rate of 3℃ / min. The wet skid resistance was characterized by the loss factor at 0℃, and the rolling resistance was characterized by the loss factor at 60℃. Table 2 is a performance comparison table of Examples 1-5 and each comparative example.

[0030] As shown in Table 2, the tread rubber materials prepared in Examples 1-5, while maintaining essentially the same wet skid resistance, exhibit significantly improved mechanical properties (tensile strength) and abrasion resistance compared to Comparative Example 1 (without aramid pulp) and Comparative Example 2 (with direct addition of aramid pulp (without preparing aramid pulp masterbatch)). Example 1 shows a 17.0% and 10.9% increase in tensile strength, and a 14.7% and 11.0% increase in abrasion resistance, respectively, which are superior to the tread rubber materials prepared in Comparative Examples 1 and 2. Furthermore, rolling resistance is significantly reduced, with Example 1 showing a 26.7% and 15.4% reduction compared to Comparative Examples 1 and 2. This is because the present invention pre-treats the aramid pulp and prepares masterbatch particles of aramid pulp and rubber matrix material before adding them, which can optimize the microstructure. By adding a lubricant, the surface of the aramid pulp is lubricated to reduce the friction between fibers. Then, when natural rubber is added later, the natural rubber can fully penetrate into the fine structure of the aramid pulp, separating the ultrafine short fibers of the aramid pulp to obtain an aramid pulp composite. In this way, the problems of the pulp's own microfibers being entangled, difficult to loosen, and difficult to isolate microfibers are solved. If no lubricant is added (Comparative Example 6) or the amount added is too small (Comparative Example 3), the friction between aramid fibers is still too large, and the rubber matrix cannot fully penetrate into the fine structure of the aramid pulp. If too much lubricant is added (Comparative Example 4), or the content of additives is too high, it will have an adverse effect on the subsequent preparation and processing of rubber products. Compared with Example 1, the tensile strength of Comparative Examples 6, 3, and 4 decreased by 7.8%, 6.6%, and 7.1%, respectively, their abrasion resistance decreased by 7.4%, 4.9%, and 4.9%, respectively, and their rolling resistance increased by 18.9%, 17.6%, and 16.3%, respectively. Modifying the isolated pulp with a coupling agent can further improve the dispersibility and compatibility of the pulp. If no coupling agent is added, the aramid pulp and the rubber matrix rely only on physical adsorption (van der Waals forces) and lack chemical bonding, resulting in a significant reduction in interfacial bonding strength. Compared with Example 1, the tensile strength of Comparative Example 5 decreased by 8.7%, its abrasion resistance decreased by 4.9%, and its rolling resistance increased by 19.5%. In this way, when aramid pulp is mixed with natural rubber / butadiene rubber and other additives, it can be better dispersed and more uniformly, improving the mixing effect and the bonding strength between the aramid pulp and the matrix. This allows the microfibers of the aramid pulp to fully extend, thereby optimizing the microfiber structure. Through modification and optimization of the aramid pulp's microstructure, the resulting tread rubber exhibits good mechanical strength, wear resistance, and low rolling resistance, enabling it to be used for extended periods in its operating environment.

Claims

1. A method for preparing a tire tread compound, characterized in that, Includes the following steps: (1) Mix aramid pulp and coupling agent at 70~90℃ for 3~7min to obtain primary modified aramid pulp. The coupling agent is a silane coupling agent. The mass ratio of aramid pulp to coupling agent is 100:6~10. (2) Add lubricant to the primary modified aramid pulp and mix at 70~90℃ for 3~7min to obtain secondary modified aramid pulp. The lubricant is a pentaerythritol ester compound and the mass ratio of aramid pulp to lubricant is 100:8~12. (3) Place the secondary modified aramid pulp in a mixer, control the initial temperature of the mixer to be 90~110℃, add natural rubber in three equal portions, and mix for 2~4 minutes each time to obtain aramid pulp masterbatch particles. The mass ratio of aramid pulp to natural rubber is 100:100~120. (4) Natural rubber, butadiene rubber, zinc oxide, stearic acid, antioxidant, carbon black, aramid pulp masterbatch, and anti-sulfurization reversion agent are mixed in an intensive manner at a ratio of 70~90:10~30:3~7:1~5:3~7:30~70:10~16 and 0.5~1.5 to obtain a first-stage masterbatch. (5) The first stage of masterbatch is mixed with accelerator, sulfur and anti-scorching agent in a mass ratio of 127.5~226.5:1~3:1.4~2.0:0.1~0.3 to obtain the second stage of masterbatch; (6) The second stage masterbatch is subjected to open milling and placed in the dark at 20~30℃ for 12~48h to obtain the compound; (7) The compound rubber is vulcanized to obtain tread rubber.

2. The method for preparing the tread compound according to claim 1, characterized in that, In step (1), the silane coupling agent is one of vinyltrimethoxysilane, vinyltriethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

3. The method for preparing the tread compound according to claim 1, characterized in that, In step (2), the pentaerythritol ester compound is one of pentaerythritol ester and pentaerythritol tetrabenzoate.

4. The method for preparing the tread compound according to claim 1, characterized in that, In step (4), the antioxidant is one or more of antioxidant 4020, antioxidant RD, antioxidant 4010, and antioxidant 4010NA; the carbon black is one of carbon black N330, carbon black N550, and carbon black N234.

5. The method for preparing the tread compound according to claim 1, characterized in that, The anti-sulfurization reversion agent in step (4) is one of 1,3-bis(citronamidomethyl)benzene, N,N'-m-phenylenebismaleimide, or sodium hexyl sulfate.

6. The method for preparing the tread compound according to claim 1, characterized in that, The accelerator in step (5) is one of accelerator DM, accelerator M, accelerator CZ, accelerator DZ, and accelerator NOBS; the scorching inhibitor is one of cytosine triphosphate, dithiophosphate trimer, and hexamethylenetetramine.

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