A silica cascade dispersion method guided by a seed interface masterbatch, a tread rubber composition, and a tire

Abstract

The present application relates to the technical field of tire preparation, and particularly relates to a seed interface masterbatch guided white carbon black cascade dispersion method, a tread rubber composition and a tire. The method first constructs a seed interface masterbatch with a part of total white carbon black, a part of total rubber, an interface precursor and a first part of sulfur-containing silane coupling agent, and makes it reach a preset bound rubber, Payne effect and Floc index window; then the remaining white carbon black is added in 2-4 rounds, so that the newly added white carbon black preferentially completes wetting, embedding and expansion around the existing seed interface; finally, the post-coupling agent and the vulcanization system are supplemented to complete network stabilization. The method can reduce random agglomeration in a high white carbon black system, inhibit premature densification and post-stage structure rebound, improve interface construction uniformity, and be conducive to balancing wear resistance, wet grip and low rolling resistance.

Description

Technical Field

[0001] This invention relates to the field of tire manufacturing technology, and in particular to a method for the cascade dispersion of silica guided by a seed-based interfacial masterbatch, a tread rubber composition, and a tire. Background Technology

[0002] Silica / silane reinforcing systems have become an important technical route for high-performance passenger car tires, especially new energy vehicle tires, in recent years due to their ability to reduce tire rolling resistance while maintaining wet grip. Compared with traditional carbon black reinforcing systems, silica has a higher density of silanol groups on its surface, which gives it strong polarity and a high specific surface area. However, this also makes it easier to form filler-filler networks through hydrogen bonding during mixing, leading to problems such as increased Mooney viscosity, increased Payne effect, enhanced flocculation tendency, and narrowed processing window. To improve these issues, the industry typically uses sulfur-containing silane coupling agents to modify the surface of silica in situ, promoting a stronger interfacial interaction between silica and the rubber matrix, thereby improving the reinforcing effect and dynamic performance.

[0003] However, the practical engineering application of silica systems does not solely depend on the addition of silane coupling agents. More importantly, in highly filled systems, the contact sequence, reaction timing, and interface formation path between silica particles, coupling agents, and rubber molecules directly affect the final network structure. If a large amount of silica and silane coupling agents are simultaneously added to the internal mixer in the early stages of mixing, while this improves mixing efficiency per unit time, it can also easily lead to excessively rapid temperature rise in localized areas, excessively high filler contact density, and premature strong interfacial bonding in some areas. This results in another portion of silica that has not yet been effectively wetted and dispersed continuing to exist as agglomerates. This coexistence of strong local interfaces and disordered agglomerations leads to uneven interfacial quality within the system, ultimately manifesting as a high Payne effect, intensified flocculation, limited adjustment space for subsequent feeding, and difficulty in simultaneously optimizing abrasion resistance, wet grip, and rolling resistance.

[0004] To address the aforementioned problems, existing technologies have proposed several improvement approaches. One approach is a multi-stage mixing process centered on optimizing the mixing sequence. For example, Chinese patent CN105014810A discloses a method for mixing silica. This method sets up a raw rubber plasticizing stage, a primary mixing stage, a reaction stage, a secondary mixing stage, and a rubber discharge stage. It prioritizes adding silica and silane coupling agents at the beginning, while adding other auxiliary materials later, to reduce interference from auxiliary materials on the silica-silane reaction, thereby improving mixing uniformity and reaction efficiency. The technical focus of this document is on reducing the adverse effects of auxiliary materials on the silanization reaction through timed feeding, essentially still revolving around the idea of ​​enabling silica and silane to complete a more complete reaction at an earlier stage. In other words, although this type of technology can improve the problem of competitive adsorption or reaction interference of auxiliary materials in the traditional one-stage method, its process logic is still based on completing the dispersion and coupling of most of the silica within the system as quickly as possible.

[0005] From an engineering perspective, the multi-stage mixing route represented in this literature is indeed superior to the simple single-feed method because it achieves a purer reaction environment and a clearer process window by adjusting the timing of materials in the preceding and following stages. However, this type of route still has significant limitations: First, it does not distinguish between two different interface formation mechanisms: the initial formation of a small amount of high-quality interface and the subsequent gradual expansion of a large proportion of filler around that interface. Second, its staged mixing still primarily pursues overall uniformity rather than constructing a seed interface that can be continuously inherited and expanded by subsequently added silica. Third, this type of technology typically relies on switching between time, temperature, or conventional mixing steps, without establishing stage criteria based on structural parameters such as binding agent, Payne effect, and flocculation rate. Therefore, it still lacks more refined process control methods for the common problems in high-precision silica systems, such as premature densification in the early stage and significant structural rebound in the later stage.

[0006] Secondly, there is the technology of preparing silica masterbatch or wet masterbatch based on the pre-preparation of highly dispersed intermediates. For example, Chinese patent CN105199171A discloses a method for preparing silica masterbatch. The basic idea is to first modify silica by atomization with a coupling agent, and then slowly and continuously add the modified silica to a rubber-solvent homogeneous system. After mixing, solvent removal, and post-treatment, silica masterbatch is obtained. This type of technology uses solution methods or near-homogeneous systems to treat silica, which can improve the pre-dispersion level of silica in the rubber matrix to a certain extent and reduce the agglomeration problem caused by uneven local shearing in conventional dry mixing. Similarly, CN115572418A further discloses a silica-containing wet mixing masterbatch suitable for tire tread rubber and its preparation method. It also involves mixing white slurry with latex or rubber dispersion system, followed by coagulation, dehydration, and drying to improve the dispersibility of silica. However, while silica masterbatches, wet masterbatches, or pre-modified routes can improve the initial dispersion of silica when it enters the rubber system, their core technology still focuses on ensuring the silica is dispersed as uniformly as possible before entering the main rubber system. They don't truly address a deeper issue in high-filler dry compounding: interfaces don't just need to form uniformly; they need to form in a sequence conducive to network stability. When all or a large proportion of silica in the system is processed in a single upstream step, although the initial dispersion may improve, new structural rearrangements, re-agglomeration, or localized network closure can still occur when it re-combines with other rubbers, oils, and compounding agents, and continues to be heated and sheared. This means that simply improving the dispersion quality of the upstream masterbatch does not necessarily equate to obtaining a more controllable interface construction path throughout the entire process.

[0007] Furthermore, while existing multi-stage mixing and masterbatch processes have improved traditional silica tread rubber production by optimizing the feeding sequence and enhancing pretreatment dispersion, they share common shortcomings: First, they lack a systematic understanding of how a small number of high-quality interface units are formed first, inducing subsequent interface expansion; second, the quality of the seed interface has not been assessed using quantifiable indicators; and third, a rigid constraint relationship has not been established between the subsequent addition of silica and the state of the interfaces formed in the previous stage. Especially in the high silica-filled systems required for new energy vehicle tires, as the silica content increases, the system more easily forms a strong filler network rapidly in the initial mixing stage, making it difficult for subsequent additions of silica to be effectively accepted by the existing interfaces. Instead, they agglomerate and cause significant structural rebound. In this case, even if the final performance improves in some indicators, repeatability, processing stability, and overall balance are often sacrificed.

[0008] Furthermore, from a process control perspective, most existing technologies rely on temperature, time, rotation speed, or whether a certain mixing stage has been completed as the basis for switching, while the monitoring and utilization of intermediate structural states remain insufficient. In fact, parameters such as total bound rubber content, chemically bound rubber content, Payne effect of uncured rubber, and Floc index in the silica-reinforced system can reflect the quality of interface construction from different aspects, including the degree of silica-rubber interface bonding, chemical coupling level, filler network strength, and reflocculation rate under thermal history. If switching to the next step relies solely on a fixed time or discharge temperature, the actual interface state of the intermediate may deviate from the ideal window when raw material batches, equipment load, ambient temperature and humidity, or shear history change, leading to instability in subsequent expansion paths. While existing literature focuses on mixing processes, masterbatch preparation, and dispersion improvement, a complete process system is still lacking that incorporates these structural parameters into the stage switching logic and determines the subsequent silica addition method accordingly.

[0009] Therefore, the existing technology still has at least the following shortcomings: First, in high silica-filled tread rubber, there is a lack of a process scheme that first uses a small amount of silica and some rubber to construct a high-quality, identifiable interface seed, and then uses this interface seed to guide the subsequent silica to expand into the system in stages; Second, there is a lack of a method that uses structural indicators such as total binder, chemical binder, Payne effect and Floc index to form an intermediate quality window, and uses this as the basis for switching process stages; Third, there is a lack of a method for constructing silica tread rubber that can be directly adapted to existing internal mixing-final mixing production lines without relying on special wet masterbatch equipment or complex solution processing equipment, while taking into account wear resistance, wet grip and low rolling resistance.

[0010] Therefore, there is an urgent need to propose a new method for the dispersion and interface construction of silica. This method departs from the traditional approach of quickly dispersing all fillers or centrally processing high-proportion silica in the initial stages. Instead, it establishes a small but stable seed interface masterbatch first, allowing subsequent silica to be gradually wetted, embedded, and expanded around this seed interface. This reduces random aggregation in highly filled systems, inhibits premature densification and later structural rebound, and improves the uniformity and repeatability of the overall interface construction. These issues are precisely the key technical problems that this invention aims to solve. Summary of the Invention

[0011] The technical objective of this invention is to provide a method for the cascade dispersion of silica guided by a seed-type interface masterbatch and the tread rubber composition obtained therefrom. By first constructing a seed-type interface masterbatch that meets the structural window requirements with a portion of silica and a portion of rubber, the remaining silica is guided to gradually complete wetting, embedding, and expansion around the seed interface in stages. This solves the problems of random agglomeration, premature densification, late-stage structural rebound, and uneven interface construction in existing high-filled silica tread rubber systems, and achieves a comprehensive balance between abrasion resistance, wet grip performance, and low rolling resistance.

[0012] Firstly, in order to achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0013] A method for seed-based interfacial masterbatch-guided cascade dispersion of silica, characterized by comprising the following steps:

[0014] S0, Seed-type interface masterbatch construction steps: [The following is a partial translation of the original text, likely due to a formatting error, and is not translated:] ...of the total rubber amount... The amount of matrix rubber and total silica in A portion of silica, an interfacial precursor, and a first portion of sulfur-containing silane coupling agent are added to a Banbury mixer and mixed to obtain a seeded interfacial masterbatch. 25 to 55 portions It accounts for 15% to 40% of the total silica content. The interface precursor is an interface regulating compound that does not contain polysulfide bonds and contains silanol groups and / or rubber molecular chains on the silica surface that can be adsorbed, reacted or entangled.

[0015] S1. Structural window determination step: Determine the total bound gum content of the seed interface masterbatch. Chemically bonded adhesive content Payne effect of uncured rubber and Floc index Only when , , , Only when at least three conditions are met simultaneously will the subsequent cascading expansion steps proceed;

[0016] S2, Cascaded Expansion Step: The remaining silica is added in 2-4 rounds, and at least a portion of the remaining rubber, processing oil, and / or at least a portion of the second part of sulfur-containing silane coupling agent are added simultaneously during each round of addition, so that the newly added silica in each round is wetted and dispersed on the basis of the seed interface or expansion interface already formed in the previous round; wherein, the rebound of the Payne effect measured after each round of addition of new silica is no more than 25% relative to the end of the previous round;

[0017] S3, Network Stabilization Step: Add the remaining rubber, the remaining sulfur-containing silane coupling agent, and the vulcanization system, and complete the final mixing to achieve a total binder content of 24%–38%, a chemical binder content of 18%–32%, and a Payne effect in the unvulcanized rubber composition. The pressure is 0.34–0.60 MPa, and the Floc index is [missing information]. The pressure is 0.004–0.011 MPa / min;

[0018] in, The percentage of rubber that remains bound to the surface of silica after extraction with common solvents, relative to the total mass of rubber before extraction. The percentage of rubber that remains bound to the surface of silica after extraction with the aid of an ammonia-based medium, relative to the total mass of rubber before extraction. To specify the difference between the low-strain storage modulus and the high-strain storage modulus under the specified test conditions, This is to define the slope of the energy storage modulus as a function of time under insulation conditions.

[0019] Preferably, the interface precursor is selected from one or two of alkoxy-terminated polyether silane, epoxy-alkoxy silane, amino-alkoxy silane, anhydride-grafted liquid diene rubber, hydroxyl-terminated liquid polybutadiene, and epoxidized liquid polybutadiene.

[0020] Preferably, in step S0, the amount of the interface precursor added is 0.5 to 6 parts, and the amount of the first part of the sulfur-containing silane coupling agent added is 2 to 10 parts; in step S3, the amount of the second part of the sulfur-containing silane coupling agent added is 0 to 8 parts; the sulfur-containing silane coupling agent is selected from one or two of TESPT, TESPD, NXT, and P97.

[0021] Preferably, the total amount of silica used is 100-160 parts, more preferably 115-150 parts; the CTAB specific surface area of ​​the silica is 140-260 m² / g.

[0022] Preferably, the base rubber, in 100 parts, includes 50 to 90 parts solution-polymerized styrene-butadiene rubber, 10 to 50 parts cis-butadiene rubber, and 0 to 25 parts natural rubber.

[0023] Preferably, in step S2, the amount of newly added silica in each round accounts for 20% to 45% of the total remaining silica; the mixing temperature during each round of addition is 95 to 140°C, the rotor speed is 35 to 80 rpm, and the discharge temperature is 120 to 155°C.

[0024] And / or, in step S2, when the Payne rebound exceeds 18% after a certain round of new silica addition, rubber and / or processing oil are added simultaneously to reduce the probability of direct agglomeration between the newly introduced silica, and the next round of feeding is carried out after the Payne rebound recovers to below 18%.

[0025] And / or, the tread rubber composition obtained at the end of step S3 satisfies the following conditions: total binder content of 24%–38%, chemical binder content of 18%–32%, and Payne effect of uncured rubber. The Floc exponent is 0.34–0.60 MPa. The pressure is 0.004–0.011 MPa / min, and the maximum Payne rebound in each round of the cascade expansion is no greater than 25%.

[0026] Secondly, the present invention also provides a tread rubber composition prepared by the method described above.

[0027] Preferably, the tread rubber composition further comprises 5-25 parts resin, 5-25 parts processing oil, 1-5 parts zinc oxide, 0.5-3 parts stearic acid, 1-5 parts antioxidant, 0.5-3 parts sulfur, and 0.5-4 parts accelerator.

[0028] Thirdly, the present invention also provides a tire tread prepared by vulcanization of the tread rubber composition described above.

[0029] Fourthly, the present invention also provides a pneumatic tire, the tread portion of which includes the aforementioned tread.

[0030] This invention constructs a small-scale nucleation and subsequent cascade expansion pathway for the silica interface, preventing the silica-rubber interface from being established in a disordered, simultaneous manner across the entire system. Instead, it first forms a stable, well-bonded, and controllable seed-type interface masterbatch, guiding subsequent additions of silica to preferentially wet, embed, and expand around the existing interface. This significantly reduces direct collisions and agglomeration between new fillers and the formation of localized hard clusters in high-silica systems, suppresses excessively rapid densification in the early stages and structural rebound in the later stages, reduces the Payne effect and Floc index of uncured rubber, and improves the uniformity, repeatability, and process window stability of interface construction within the system. Simultaneously, due to the improved levels of total and chemically bound rubber and a more coordinated filler network, the tread rubber composition prepared by this invention can maintain high reinforcement and low DIN abrasion while also achieving superior wet grip and low rolling resistance. This makes it more conducive to achieving a comprehensive balance between abrasion resistance, wet grip, and energy saving, and is particularly suitable for high-performance tread rubber systems such as those for new energy vehicle tires, which have high requirements for dynamic performance and energy consumption. Detailed Implementation

[0031] The present invention will now be described in further detail. It should be understood that the specific embodiments described below are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Any equivalent substitutions, conventional adjustments, or modifications made by those skilled in the art based on this specification without departing from the concept of the present invention should fall within the scope of protection of the present invention.

[0032] This invention proposes an interface construction method for high-precision silica (SSil) tread rubber systems. Unlike existing technologies that simultaneously add a large amount of SSil in the initial stages and disperse and couple it as synchronously as possible, this invention does not aim for the earliest apparent dispersion of all SSil. Instead, it prioritizes utilizing a smaller portion of the total SSil and a portion of the total rubber to first establish a seeded interface masterbatch with high interface quality, low structural rebound tendency, and good subsequent acceptance capacity. Based on this, the remaining SSil is added gradually in 2-4 rounds, allowing each round of new SSil to preferentially wet, embed, and expand around the existing seed interface or the previous round's expanded interface. This restructures the formation sequence of the SSil interface from a random, simultaneous generation of the entire system into a controlled path of small-scale nucleation followed by cascading expansion. Finally, the overall network is stabilized through the addition of a sulfur-containing silane coupling agent and the vulcanization system in the later stages.

[0033] I. Terminology Explanation

[0034] To facilitate understanding of this invention, the main terms appearing in the specification will be explained first.

[0035] Seed-type interfacial masterbatch: refers to an intermediate formed by intensive mixing of 15%–40% of the total silica and 25–55% of the total rubber, with the participation of interfacial precursors and a first-part sulfur-containing silane coupling agent. This intermediate is not a typical pre-mixed masterbatch, but rather requires it to achieve specific bonding properties, Payne effect, and Floc index window to guide the subsequent expansion of new silica around the existing interface.

[0036] Interface precursors: These are compounds that do not contain polysulfide bonds and can form adsorption, chemical reactions, polar interactions, or chain entanglements with the silanol groups on the surface of silica and / or rubber molecular chains. They are used to preferentially establish a flexible, stable, and scalable silica-rubber transition interface in the S0 stage. They can be selected from one or two of the following: alkoxy-terminated polyether silanes, epoxy-alkoxy silanes, amino-alkoxy silanes, anhydride-grafted liquid diene rubbers, hydroxyl-terminated liquid polybutadiene, and epoxidized liquid polybutadiene.

[0037] Total bound rubber: refers to the percentage of rubber remaining and bound to the surface of silica after extraction with common solvents, relative to the total amount of rubber before extraction. It reflects the overall interfacial coating and adsorption / entanglement level of the silica surface.

[0038] Chemically bonded rubber: refers to the percentage of rubber remaining on the surface of silica after extraction with the aid of an ammonia-based medium, relative to the total amount of rubber before extraction. It mainly reflects strong interfacial interactions, especially the level of strong adsorption / entanglement that is difficult to break down through chemical coupling.

[0039] The Payne effect refers to the difference between the low-strain and high-strain storage modulus of uncured rubber under specified test conditions, used to characterize the strength of the filler network and its destructibility under dynamic strain. In this invention, a larger Payne effect generally indicates a stronger silica-silica network and a more pronounced tendency for random aggregation in the system.

[0040] Floc index: refers to the slope of the storage modulus of uncured rubber over time under specified insulation conditions, used to characterize the reflocculation rate of silica during thermal processes. A higher Floc index generally indicates that the system is more prone to structural rebound or network reconstruction during subsequent processing or storage.

[0041] Cascaded expansion: This refers to the fact that the remaining silica does not enter the system all at once, but is added in 2 to 4 rounds. In each round, the newly added silica prioritizes wetting and embedding around the seed interface or extended interface that existed in the previous stage, so that the interface is gradually transferred and spread from local high-quality units to the whole system.

[0042] Payne rebound magnitude: refers to the increase in the Payne effect measured after a certain round of new silica addition and completion of the mixing process, relative to the increase in the Payne effect at the end of the previous stage. It is used to evaluate whether the new silica entering the system mainly expands in a controlled manner around the existing interface, or whether there is obvious direct agglomeration between the new fillers.

[0043] Network stability window: refers to the predetermined range within which the final mixed tread rubber composition falls in terms of total binder, chemical binder, Payne effect, and Floc index, reflecting the final interface quality and the degree of coordination between the filler network.

[0044] II. System Structure

[0045] While the subject of this invention is a method and the tread rubber composition obtained therefrom, to enable those skilled in the art to clearly and completely implement this invention, a typical system structure for implementing the method is further described below. The system can be built on an existing internal mixing-final mixing production line without fundamentally modifying the core equipment; only intermediate sampling detection and stage switching control logic based on structural windows need to be introduced into the existing process.

[0046] The system includes at least a raw material supply unit, a main internal mixing unit, an intermediate sampling and structural detection unit, a process determination unit, a cascade feeding control unit, and a final mixing unit.

[0047] The raw material supply unit is used to supply rubber, silica, interfacial precursors, sulfur-containing silane coupling agents, processing oils, resins, and conventional compounding agents to the main mixing unit in stages. Preferably, the raw material supply unit is equipped with an independent weighing module to ensure that the addition ratio of seed silica, seed rubber, interfacial precursors, and the first part of sulfur-containing silane coupling agents in stage S0 is accurate and controllable; for the newly added silica in each round of stages S1 to S2, it is also preferred to measure and buffer it separately for each round.

[0048] The main mixing unit can be a commonly used internal mixer in the art, such as a tangential rotor type or a meshing rotor type internal mixer. Preferably, the main mixing unit can record or output parameters such as rotor speed, chamber temperature, discharge temperature, torque, and mixing time. It should be noted that the innovation of this invention does not lie in the special mechanical structure of the internal mixer itself, but rather in utilizing the same mixing platform to reconstruct the sequence of silica interface formation through staged material path design and structural window control.

[0049] The intermediate sampling and structural testing unit is used to sample and test the total bond strength, chemical bond strength, Payne effect, and Floc index of the rubber compound after S0, after each of S1-S2, and, if necessary, after S3. The testing can be performed either by online nearline analysis or by rapid laboratory analysis. For industrial applications, a combination of nearline sampling and rapid RPA testing is preferred; for R&D or pilot-scale applications, a more complete extraction and rheological testing process can be used to improve the accuracy of window settings.

[0050] The process determination unit is used to receive the results output by the intermediate sampling and structure detection unit and determine whether the current intermediate has reached the preset structure window. The process determination unit can be an industrial controller, process management software, or a manual determination rule table. As long as it can determine whether the conditions for switching from S0 to S1 are met based on the detection results, and whether the conditions for entering the next round or final mixing are met after a certain round of cascade expansion, the implementation requirements of this invention can be met.

[0051] The cascade feeding control unit is used to control the batching, timing, and proportion of the remaining silica, rubber, processing oil, and the second part of sulfur-containing silane coupling agent, according to the output of the process judgment unit. The function of this unit is to: when the seed interface masterbatch has reached the preset window, not add the remaining silica all at once, but distribute it in batches, and determine the next batch of silica and auxiliary materials to be added based on the current payne rebound amplitude, discharge temperature, torque changes, and processing window requirements.

[0052] The final mixing unit is used in step S3 to add the remaining rubber, the remaining sulfur-containing silane coupling agent, and the vulcanization system, so that the entire system reaches the final network stability window. The final mixing unit can be completed using a conventional open mill or low-temperature internal mixer to reduce the risk of early reactions in the vulcanization system.

[0053] Through the aforementioned system structure, this invention effectively introduces a closed-loop process for intermediate structure determination and stage expansion control into existing rubber compounding production lines. This closed loop does not simply use time or temperature as the basis for stage switching; instead, it moves the quality and network formation state of the silica-rubber interface forward to the process control center. This ensures that subsequent additions of silica are no longer a mechanical repetition of a fixed formula, but rather a controlled expansion around the existing interface. It is precisely this that enables this invention to achieve an effect closer to the step-by-step growth of the interface in a dry mixing system without relying on dedicated wet-process masterbatch equipment.

[0054] III. Specific Technical Route for Implementing the Method of the Invention

[0055] The specific technical route of this invention can be summarized into the following four stages: S0 seeding interface masterbatch construction stage, S1 structural window determination stage, S2 cascade expansion stage, and S3 network stabilization stage.

[0056] In the S0 stage, not all silica is used; instead, only 15%–40% of the total silica is used as seed silica. Correspondingly, only 25–55 parts of the total rubber are used as seed rubber. Seed silica, seed rubber, interfacial precursors, and the first portion of sulfur-containing silane coupling agent are added to an internal mixer. Under limited temperature and shear conditions, silica-rubber units with a limited local quantity but high interfacial quality are first formed. At this stage, the interfacial precursors preferentially provide flexible transition, polarity matching, surface adsorption, or pre-grafting effects, while the first portion of sulfur-containing silane coupling agent further provides a foundation for subsequent interfacial strengthening, but without causing premature local densification as it would with full-volume early addition.

[0057] In stage S1, the intermediate obtained in S0 undergoes structural testing. The key here is not the testing itself, but rather its use as a rigid threshold for entering the next stage. Only when at least three of the following criteria are met—total binding, chemical binding, Payne effect, and Floc index—are the intermediate considered no longer a typical pre-gel, but a seed-type interface masterbatch with genuine subsequent guiding capabilities.

[0058] In stage S2, the remaining silica is added in 2-4 rounds. After each round, the goal is not simply to achieve complete dispersion as quickly as possible, but rather to control the newly added silica to preferentially wet and embed around the existing interface by simultaneously adding a portion of rubber, processing oil, and / or a second portion of sulfur-containing silane coupling agent. If the payne rebounds excessively after a round of addition, it indicates that strong direct contact has occurred between the newly added silica particles. In this case, the proportion of newly added silica in that round should be reduced, the matching rubber or processing oil should be increased, or the timing of silane addition should be changed to ensure that the next round returns to a controllable expansion path.

[0059] In stage S3, the remaining rubber, sulfur-containing silane coupling agent, and vulcanization system are added to further solidify and stabilize the aforementioned progressively spread interfaces, ultimately yielding a tread rubber composition with higher total bind, higher chemical bind, lower Payne effect, and lower Floc index. For tire applications, this final structure implies a more uniform reinforcing interface, lower random agglomeration, a more moderate tendency for thermal history restructuring, and a more favorable overall balance between abrasion resistance, wet grip, and rolling resistance.

[0060] IV. Key Parameters and Their Definitions

[0061] To make the technical solution of this invention clearer, several parameter expressions that can be used in process control are given below. It should be noted that these expressions are used to help those skilled in the art to understand and implement this invention, and should not be mechanically interpreted as limiting the scope of protection to a specific calculation method.

[0062] The percentage of precipitated silica in the seeds can be expressed as:

[0063] ;

[0064] in, The percentage of seed silica in the total silica; The quality of silica added in the S0 stage; This refers to the total mass of silica in the formula.

[0065] The percentage of seed rubber can be expressed as:

[0066] ;

[0067] in, This represents the percentage of seed rubber in the total rubber. The quality of rubber added in stage S0; This refers to the total mass of rubber in the formulation, usually expressed in 100 parts.

[0068] The bounce magnitude of Payne after a certain round of cascading expansion can be expressed as:

[0069] ;

[0070] in, For the first The rebound in Payne's performance after the addition of new silica in this round is relative to the end of the previous phase. For the first Payne effect measured after the end of the round; This refers to the Payne effect measured after the previous stage. Preferably, No more than 25%, preferably no more than 18%.

[0071] The overall structure determination after network stabilization can be based on the following window:

[0072] ;

[0073] in, For the final state structure window set; Total binder content; Content of chemically bonded adhesive; Payne effect in uncured rubber; For the Floc exponent. When , , and When all or most of the data falls within the predetermined range, it indicates that the system has good interface uniformity and network stability.

[0074] V. Specific Implementation Methods for Each Step

[0075] The specific manner of implementing the method of the present invention will be described in detail below according to the steps in the claims.

[0076] (a) S0: Construction steps of seed-based interface masterbatch

[0077] Step S0 is the primary core step that distinguishes this invention from conventional multi-stage compounding and conventional masterbatch methods. Its purpose is not to process as much silica as possible in the initial stage, but rather to establish an intermediate with stable interfacial quality, which can be inherited and extended by subsequently added silica, using only a small proportion of the total silica and a portion of the total rubber. This intermediate must not be a formally pre-mixed rubber, but rather a functional interfacial seed.

[0078] In practical implementation, it is preferable to pre-cut or pre-plasticize the base rubber to facilitate uniform contact with silica and interfacial precursors. The base rubber may include 50-90 parts solution-polymerized styrene-butadiene rubber, 10-50 parts butadiene rubber, and 0-25 parts natural rubber. For new energy vehicle tread compounds, a combination of approximately 70 parts functionalized or low rolling resistance solution-polymerized styrene-butadiene rubber and approximately 30 parts butadiene rubber is preferred to balance processability and dynamic performance.

[0079] Subsequently, 15% to 40% of the total silica content is selected as seed silica. If the proportion of seed silica is too low, for example, below 15%, the number of high-quality interface cores that can be formed will be insufficient. When newly added silica enters the system, they will still tend to contact each other preferentially, making it difficult to achieve the effect of expanding around the existing interface. If the proportion of seed silica is too high, for example, above 40%, the S0 stage itself is prone to reverting to the logic of ordinary masterbatch rubber processed with a large proportion of silica in the previous stage. The risk of premature densification in local areas increases significantly, and the subsequent processing window narrows. Based on the results of the embodiments, the present invention preferably controls the proportion of seed silica at 25% to 38%, which is more conducive to balancing the quantity, quality and subsequent expansion space of the seed interface.

[0080] The interface precursor plays a crucial role in this step. Unlike traditional methods that rely entirely on sulfur-containing silane coupling agents to rapidly establish a strong interface at high temperatures, this invention prioritizes the use of an interface precursor free of polysulfide bonds to establish a flexible transition layer. This transition layer possesses at least one or more of the following functions: firstly, it reduces the probability of direct strong hydrogen bond association between silanol groups on the surface of silica; secondly, it improves initial wetting efficiency, making it easier for seed silica to be coated by seed rubber; thirdly, it forms polar adsorption, flexible chain entanglement, or weak chemical linkages between silica and rubber molecular chains to improve the integrity of the seed interface; and fourthly, it provides a more uniform contact basis for further coupling with the subsequent sulfur-containing silane coupling agent. The preferred amount of interface precursor is 0.5–6 parts, more preferably 0.8–2.5 parts. If the amount is too low, the flexible transition layer will not form sufficiently; if the amount is too high, it may cause excessive plasticization of the rubber compound, high dynamic loss, or excessively strong local competitive adsorption.

[0081] The first part of the sulfur-containing silane coupling agent is not completely omitted in S0, but rather allocated with the idea of ​​establishing a foundation in small quantities first, and then further locking it in S3. Its preferred dosage is 2-10 parts, more preferably 2-5 parts. This arrangement serves two purposes: firstly, to ensure a certain degree of chemical interface foundation between silica and rubber is established in the S0 stage; secondly, to avoid premature local coupling and structural hardening caused by the early concentrated addition of the full amount of silane. In actual operation, the seed rubber and seed silica can be pre-dispersed within the range of 95-110℃. After the internal mixer torque reaches initial stability, the interface precursor and the first part of the sulfur-containing silane coupling agent are added for further mixing. Alternatively, depending on equipment conditions, a sequential approach can be adopted: silica first, interface precursor later, and the first part of the sulfur-containing silane coupling agent last, to reduce early powder dispersion and localized high-concentration reactions.

[0082] The mixing temperature and time in the S0 stage should aim to establish a high-quality seed interface, rather than simply pursuing high temperature and strong reaction. If the temperature is too low, the interaction between the interface precursor and the silica surface, as well as the initial reaction of the sulfur-containing silane coupling agent, will be insufficient; if the temperature is too high, hard agglomerates or an overly strong interface may easily form locally in the seed silica, weakening its flexibility in accepting newly added silica. Preferably, the chamber temperature in the S0 stage is controlled at 95–140°C, more preferably 100–125°C; the rotor speed can be 35–80 rpm, preferably 40–65 rpm. The discharge temperature can be adjusted according to the equipment size and target window, and is generally suitable at 120–150°C.

[0083] It is important to emphasize that the end of the S0 step should not be solely based on the time elapsed or the discharge temperature being reached, but rather on whether the intermediate meets the seed structure window. This is one of the biggest differences between this invention and traditional front-end compounding. The quality window of the seed interface masterbatch preferably meets at least three of the following criteria: total bound rubber content 20%–32%, chemically bound rubber content 15%–28%, uncured rubber Payne effect no greater than 0.55 MPa, and Floc index 0.004–0.013 MPa / min. These at least three criteria are not arbitrarily set, but rather taken into account that certain indicators in different formulation systems may slightly deviate due to differences in rubber type, silica grade, interface precursor type, or RPA equipment. However, as long as most key indicators fall within a reasonable range, the seed interface can be considered to have good overall quality.

[0084] If the total binder is insufficient after the S0 test, it usually indicates that the wetting and coating of silica is inadequate, or that the contact between the interfacial precursor and the rubber with the silica is insufficient. If the chemical binder is low, it may indicate that the timing of the addition of the sulfur-containing silane coupling agent in the first part is poor or the initial temperature is insufficient. If the Payne effect is high, it indicates that the filler-filler network is still too strong, and there is too much direct contact between silica particles. If the Floc index is high, it indicates that the intermediate is still prone to rapid reflocculation under thermal conditions, and there is a greater risk of structural rebound during subsequent expansion. In this case, priority should be given to adjusting the proportion of seed silica in S0, the type of interfacial precursor and its addition timing, and the amount and order of addition of the sulfur-containing silane coupling agent in the first part. It is not recommended to simply extend the mixing time to refine the system, as the latter often leads to unnecessary heat accumulation and local overreaction.

[0085] Mechanistically, the S0 step essentially establishes a scalable interface template. This template is not a geometrically fixed core, but rather a local interface unit composed of a silica surface coated by seed rubber, a flexible transition layer formed by the interface precursor, and a moderate initial coupling layer. This unit is more stable than ordinary pre-mixed rubber, but not as rigid as a high-proportion pre-mixed masterbatch. Therefore, when new silica is added subsequently, it is more likely to become a preferred contact, preferred wetting, and preferred embedding site, thus pulling the interface formation sequence of the new silica back to the path of expansion around the existing interface.

[0086] (II) S1: Structural Window Determination Steps

[0087] The innovative contribution of step S1 lies in its shifting the focus from simply using experimental characterization methods such as total binder, chemical binder, Payne effect, and Floc index to becoming core control criteria for process stage switching. In traditional mixing processes, these indicators are typically used to evaluate results after the process is completed. However, in this invention, these indicators are used to determine whether subsequent cascade expansion is permitted. In other words, this invention is not a post-event evaluation, but rather process control.

[0088] In practice, samples can be taken from the adhesive compound after S0 debinding, and the total binder and chemically bound binder are determined using ordinary solvent extraction and ammonia-assisted extraction, respectively. The difference in storage modulus at 0.56% strain and 100% strain is measured using RPA at 60°C and 1Hz to obtain the Payne effect. The Floc index is obtained by holding the compound at 100°C, 1Hz, and 0.56% strain for 20 minutes using RPA, and the slope of the storage modulus change over time. Although the detection methods themselves are conventional in the field, in this invention, these methods serve as process gating mechanisms.

[0089] Preferably, the S2 cascade extension step is permitted only if at least three of the following four conditions are met: total binder content is 20%–32%, chemical binder content is 15%–28%, Payne effect is no greater than 0.55 MPa, and Floc index is 0.004–0.013 MPa / min. If all four conditions are met, it indicates a high seed interface quality; if only three conditions are met, process release can be carried out based on the target product focus; if two or fewer conditions are met, it is generally not advisable to proceed to subsequent cascade extension, otherwise the newly added silica will be difficult to be effectively guided by the seed interface.

[0090] The reason for employing at least three indicators, rather than simply using a single metric, is that this invention focuses on the comprehensive nature of interface quality. For example, a high total bound viscosity but also a high Payne effect indicates that although interface coating has improved, the filler network in the system remains relatively strong; a high chemically bound viscosity but a high Floc index indicates that a strong local interface has formed, but the overall network remains unstable under thermal conditions; a low Payne effect but a low total bound viscosity suggests that the dispersion may only be temporarily loose, and the interface coating and acceptance capabilities have not been truly established. Therefore, using multiple indicators for joint judgment can more accurately reflect whether the seed-forming interface masterbatch possesses the functional attributes to guide subsequent expansion.

[0091] Step S1 also has an important effect: improved process repeatability. Traditional processes often rely on fixed times, fixed temperatures, or empirical torque judgments. Even with identical external process parameters, the intermediate structure can vary significantly depending on different batches of raw materials, different moisture absorption states of silica, and different equipment loads. In this invention, the process does not proceed to the next stage unless the intermediate structure reaches a certain threshold. This shifts the basis for stage switching from external process conditions to internal structural state, significantly reducing batch-to-batch fluctuations.

[0092] (III) S2: Cascaded Expansion Steps

[0093] Step S2 is another core inventive step of this invention. Instead of adding the remaining silica all at once, this step involves adding it in 2 to 4 rounds, with each round expanding around the existing interface, thus allowing the interface to gradually spread from a local seed to the entire system. The key here is not the round-feeding itself, but rather why the process is done in rounds and how to ensure that the newly added silica primarily expands around the existing interface.

[0094] In this invention, the remaining silica is preferably added in 2 to 4 stages. If it is added in only 1 stage, it is essentially still close to a one-time addition, making it difficult to fully utilize the guiding effect of the seed interface; if it is added in more than 4 stages, although process control can be further refined, the industrial cycle time may be affected, and the heat exposure of the rubber compound increases with each stage, which is not conducive to industrial scale-up. Based on the results of the embodiments, 2 stages and 3 stages are the more preferred cascaded expansion paths.

[0095] The optimal amount of new silica added in each round is 20%–45% of the total remaining silica. This percentage is neither too low nor too high. If the amount added in each round is too small, although it is easier to control, the industrial cycle is poor and the interface increment per round is limited; if the amount added in each round is too large, the newly added silica is more likely to come into direct contact with each other and form a new filler network, weakening the seed-guiding effect. Especially in high specific surface area silica systems, an excessive amount added in a single round will rapidly increase the Payne effect and cavity torque, causing the system to return to a path dominated by random agglomeration.

[0096] To ensure that the newly added silica preferentially wets and embeds itself around the existing interface, this invention preferably involves simultaneously adding at least a portion of the remaining rubber, processing oil, and / or at least a portion of the second portion of sulfur-containing silane coupling agent during each addition process. This is because when the new silica enters the system, if only silica is added alone, the local silica concentration increases rapidly, raising the probability of direct contact between them. Simultaneously adding some rubber provides an immediate coating medium for the new silica; simultaneously adding a small amount of processing oil reduces local friction and instantaneous structural rigidity, improving wetting efficiency; and simultaneously adding an appropriate amount of downstream silane helps to further solidify the new interface based on the existing flexible transition interface. However, the timing and proportion of its addition should not be too abrupt to avoid reverting to the old path of excessively strong coupling in the initial stage.

[0097] In actual operation, each round of S2 can be performed as follows: First, the intermediate from the previous stage is fed into the internal mixer and heated to the predetermined temperature; then, the newly added silica for this round is added, and a portion of the remaining rubber or a small amount of processing oil is added simultaneously according to the design scheme; after pre-dispersion, if necessary, a portion of the second part of sulfur-containing silane coupling agent is added; continue mixing until the torque and temperature of this round reach a relatively stable state, then discharge the rubber and take samples to test the payne rebound amplitude and, if necessary, the Floc change. If the payne rebound of this round is not greater than 25%, preferably not greater than 18%, it can be considered that the newly added silica in this round mainly expands around the existing interface, allowing it to enter the next round; if it exceeds this threshold, it indicates that the proportion of new networks directly formed between the newly added silica in this round is too large, and the feeding ratio and order should be changed in the next round or during remixing.

[0098] In this invention, the essence of the expansion of newly added silica around the existing interface can be understood from the following aspects. First, the seed interface already established in S0 has a lower local surface energy and higher rubber accessibility than the bare silica surface. Therefore, when newly added silica comes into contact with this interface, it is easier to be attracted and covered by the existing rubber chains and interface precursor transition layer. Second, the existing interface has a certain degree of flexibility and scalability, and is not a completely dense rigid shell. Therefore, when newly added silica enters, it is easier to embed into the rubber phase around the interface, rather than directly forming a strong network with other newly added silica. Third, the phased addition ensures that each batch of newly added silica faces an environment dominated by the existing interface, rather than an environment where the same batch of newly added silica is dominated by each other, thus changing the priority contact object probabilistically.

[0099] (iv) S3: Network stabilization steps

[0100] The main function of step S3 is to stabilize the final network structure by adding excess rubber, excess sulfur-containing silane coupling agent, and a vulcanization system based on the previously formed progressively expanding interfaces. Compared to S0 and S2, this step is more inclined towards conventional final mixing logic. However, in this invention, its functional positioning still differs from traditional final mixing: traditional final mixing often involves making final modifications under the premise of highly uneven interface quality, while S3 of this invention locks the entire system based on the establishment of a high-quality seed interface in the front stage and the completion of controlled cascade expansion in the middle stage. Therefore, its result is more stable and more uniform.

[0101] In practice, the second part of the sulfur-containing silane coupling agent can be added in stages during the latter half of S2, or it can be added in concentrated S3, with a preferred total amount of 0-8 parts. If the first part of the sulfur-containing silane coupling agent already accounts for a large proportion in S0, the amount added in S3 can be appropriately reduced; if the S0 stage mainly relies on the interfacial precursor to establish a flexible transition layer, then more sulfur-containing silane coupling agent should be added in S3 to enhance the final interfacial strength. It should be noted that the addition of sulfur-containing silane coupling agent in the later stages should be based on the premise that the system already has good interfacial uniformity; otherwise, even if the later stage addition is more intense, it will only lock in the existing non-uniform structure, rather than improve it.

[0102] The vulcanization system can be added using conventional methods in the art, such as zinc oxide, stearic acid, antioxidants, sulfur, and accelerators. Preferably, it is added at a lower temperature in the final mixing equipment to prevent early scorching. The final rubber compound preferably meets the following requirements: total binder 24%–38%, chemical binder 18%–32%, Payne effect 0.34–0.60 MPa, and Floc index 0.004–0.011 MPa / min. Falling within this window generally indicates a relatively uniform silica interface, a more coordinated filler network, and a lower tendency for reflocculation.

[0103] VI. Examples and Comparative Examples

[0104] The following examples and comparative examples are used to further illustrate the present invention, but do not constitute a limitation on the scope of protection of the present invention. Unless otherwise specified, all raw materials are expressed in parts by weight (phr) and are based on 100 parts of total rubber. All examples use the same basic formulation framework, only changing the seed interface masterbatch setting, the type and amount of interface precursor, the cascade extension mode of silica, and the front-to-back distribution mode of sulfur-containing silane coupling agent.

[0105] (a) Raw materials and basic formula

[0106] 1. Base rubber

[0107] F-SSBR: 70 copies;

[0108] BR: 30 copies.

[0109] 2. Reinforcing fillers and compounding agents

[0110] Silica: 135 parts;

[0111] Tackifying / functional resin: 18 parts;

[0112] Processing oil: 14 parts;

[0113] Zinc oxide: 2.5 parts;

[0114] Stearic acid: 2.0 parts;

[0115] Antioxidant 6PPD: 2.0 parts;

[0116] Protective wax: 1.5 parts;

[0117] Sulfur: 1.4 parts;

[0118] Accelerator CZ: 1.6 parts;

[0119] Accelerator DPG: 1.8 parts.

[0120] 3. Interfacial precursors and coupling agents

[0121] PES: Alkoxy-terminated polyether silane;

[0122] ELBR: Epoxidized liquid polybutadiene;

[0123] TESPT: Bis-(triethoxysilylpropyl)tetrasulfide;

[0124] NXT: 3-Octaylthio-1-propyltriethoxysilane.

[0125] 4. Silica Indicators

[0126] CTAB silica has a specific surface area of ​​approximately 180 m² / g, a pH value of approximately 6.5–7.5, and a volatile content of less than 6%.

[0127] (II) Main Equipment and Testing Methods

[0128] 1. Mixing equipment

[0129] The primary mixing was performed using a 1.6L laboratory internal mixer with a tangential rotor; the final mixing was done using an 8-inch open mill. The internal mixer fill factor was controlled between 0.68 and 0.75.

[0130] 2. Structural index testing methods

[0131] (1) Total binding adhesive

[0132] Weigh out uncured rubber samples, extract with toluene for 72 hours, determine the residual amount of rubber, and calculate the total bound rubber content.

[0133] (2) Chemically bonded adhesive

[0134] Based on the above, after treatment with an ammonia-based medium, extraction was performed again to measure the amount of interfacial binder that could not be removed, and the chemical binder content was calculated.

[0135] (3) Payne effect

[0136] Using RPA, at 60℃ and 1Hz, the difference in storage modulus between 0.56% strain and 100% strain was measured and denoted as . .

[0137] (4) Floc exponent

[0138] Using RPA, the energy storage modulus was held at 100℃, 1Hz, and 0.56% strain for 20 min, and characterized by the slope of the change in energy storage modulus over time, with units of MPa / min.

[0139] (5) DMA test

[0140] Test loss factor at 0℃ and 60℃ .

[0141] (6) DIN wear

[0142] The wear volume loss is tested according to the DIN standard method, and the unit is mm³. The lower the value, the better the wear resistance.

[0143] (7) Mechanical properties

[0144] Test the stress and tensile strength at 300% constant elongation.

[0145] 3. Parameters for determining the cascading expansion process

[0146] The percentage of precipitated silica in the seeds is recorded as follows:

[0147] ;

[0148] in, The percentage of silica in the seeds. The quality of silica added in the S0 stage, This represents the total mass of silica.

[0149] No. The rebound of Payne after the addition of new silica is recorded as follows:

[0150] ;

[0151] in, For the first Payne's rebound magnitude For the first The Payne effect after the round ends This refers to the Payne effect following the conclusion of the previous stage.

[0152] (III) Examples

[0153] Example 1

[0154] First, 35 parts of rubber and 30% of the total amount of silica were added to an internal mixer and premixed for 30 seconds at 95–110°C. Then, 1.5 phr of PES and 3 phr of TESPT were added, and the rotor speed was controlled at 55 rpm. Mixing continued until the discharge temperature reached approximately 138°C, yielding the seeded interface masterbatch. Sampling tests showed that the total seed-bound rubber was 23.4%, the seed chemical-bound rubber was 18.1%, the seed Payne effect was 0.47 MPa, and the Floc index was 0.0081 MPa / min, meeting the structural window requirements.

[0155] The remaining silica was then added in two batches: in the first batch, 50% of the remaining silica was added, along with 7 phr of processing oil; in the second batch, the remaining silica was added, with 6 phr of TESPT added later. After the main mixing was completed, sulfur, accelerators, and other conventional additives were added in the final milling process to obtain the tread rubber composition.

[0156] In this embodiment, the maximum Payne rebound amplitude during the two-stage cascade expansion process was 7.8%. The final test results were: total bond strength 28.6%, chemical bond strength 24.2%, Payne effect 0.42 MPa, Floc index 0.0071 MPa / min, and DIN wear 86 mm³. It is 0.351. The value is 0.112, the 300% constant elongation stress is 12.4 MPa, and the tensile strength is 18.9 MPa.

[0157] Example 2

[0158] The process is essentially the same as in Example 1, except that the proportion of seed silica is increased to 35%, PES is increased to 2.0 phr, and more processing oil is added simultaneously during the first round of cascade expansion, so that the newly added silica has better wetting conditions in the early stage of expansion. The amount of TESPT added in the later stage is 5 phr.

[0159] Tests showed that the seed masterbatch had a total binder content of 25.8%, a chemical binder content of 20.7%, a seed payne effect of 0.44 MPa, and a Floc index of 0.0072 MPa / min. The maximum payne rebound was 6.2%. The final rubber compound had a total binder content of 29.8%, a chemical binder content of 25.0%, a payne effect of 0.40 MPa, a Floc index of 0.0066 MPa / min, and a DIN abrasion of 82 mm³. It is 0.346. The value is 0.109, the 300% constant elongation stress is 12.8 MPa, and the tensile strength is 19.3 MPa.

[0160] This embodiment demonstrates that when the seed interface quality is further improved and the first batch of newly added silica is more fully wetted, the network rebound is smaller, and a better balance between abrasion resistance and rolling resistance can be achieved.

[0161] Example 3

[0162] This embodiment employs a gentler seed interface scheme. First, 25% of the total silica and 30 parts of rubber are added to a mixer for pre-dispersion. ELBR 2.0 phr is then added. No significant amount of TESPT is added in the S0 stage; only 2 phr of TESPT is added to establish basic coupling. After the seed masterbatch reaches the window, the remaining silica is added in three batches, with samples taken at intervals between each batch. TESPT is added twice in the latter half of S2, for a total of 6 phr of TESPT added in the later stages.

[0163] Tests showed that the total seed binder was 22.6%, the chemical binder was 17.4%, the seed payne effect was 0.49 MPa, and the Floc index was 0.0084 MPa / min. The maximum payne rebound during the three-stage cascade expansion was 8.9%. The final compound had a total seed binder of 27.4%, a chemical binder of 23.3%, a payne effect of 0.43 MPa, a Floc index of 0.0076 MPa / min, and a DIN abrasion of 90 mm³. It is 0.356. The value is 0.115, the 300% constant elongation stress is 12.0 MPa, and the tensile strength is 18.5 MPa.

[0164] This embodiment illustrates that using a liquid rubber-type interface precursor to construct a relatively soft seed interface is beneficial for improving low-temperature dynamic performance and wet gripping level.

[0165] Example 4

[0166] First, 28% of the total silica and 32 parts of rubber were added to an internal mixer for pre-dispersion. Then, 1.5 phr of PES and 1.0 phr of NXT were added to form a composite interface precursor system. During the S0 stage, only a small amount of TESPT (2 phr) was added simultaneously. After the seed masterbatch reached the window, the remaining silica was added in three batches. During the first and second expansion stages, a small amount of processing oil (3 phr each) was added to mitigate local structural reconstruction. During the S3 stage, 4 phr of TESPT and 1 phr of NXT were added.

[0167] Tests showed that the total seed binder was 24.1%, the chemical binder was 19.2%, the seed Payne effect was 0.46 MPa, the Floc index was 0.0079 MPa / min, and the maximum Payne rebound was 8.1%. The final total seed binder was 29.1%, the chemical binder was 24.6%, the Payne effect was 0.41 MPa, the Floc index was 0.0068 MPa / min, and the DIN abrasion was 84 mm³. It is 0.349. The value is 0.110, the 300% constant elongation stress is 12.6 MPa, and the tensile strength is 19.0 MPa.

[0168] This embodiment demonstrates that when the composite interface precursor is combined with multiple small-scale refueling cycles, it is more conducive to obtaining a low Floc index and a more stable network.

[0169] Example 5

[0170] In this embodiment, 32% silica was used in the seeding stage, the interface precursor was a combination of 0.8 phr PES and 1.5 phr ELBR, and 40 parts of seed rubber were used. After reaching the S0 window, 10 phr of rubber was added in the first round of cascade expansion, so that the newly added silica would preferentially interact with the newly added rubber and the original seed interface, rather than agglomerate with each other. The amount of TESPT added in the later stage was 5 phr.

[0171] Tests showed that the total seed binder was 24.8%, the chemical binder was 18.9%, the seed payne effect was 0.48 MPa, and the Floc index was 0.0080 MPa / min. The maximum payne rebound was 9.4%. The final state showed a total seed binder of 28.8%, a chemical binder of 24.1%, a payne effect of 0.44 MPa, a Floc index of 0.0070 MPa / min, and a DIN abrasion of 87 mm³. It is 0.358. The value is 0.113, the 300% constant elongation stress is 12.2 MPa, and the tensile strength is 18.8 MPa.

[0172] This embodiment illustrates that adding additional rubber during the cascade expansion process helps improve the interface acceptance efficiency and wet grip performance of the newly added silica.

[0173] Example 6

[0174] In this embodiment, the proportion of seed silica is increased to 38%, and the interfacial precursor is 1.2 phr of PES. After obtaining a high-quality seed masterbatch in the S0 stage, the remaining silica is added in three batches, and 4 phr of processing oil is added in the latter half of the second batch to reduce structural rebound. The amount of TESPT added in the later stage is 4 phr.

[0175] Tests showed that the total seed binder was 26.3%, the chemical binder was 21.1%, the seed payne effect was 0.45 MPa, and the Floc index was 0.0074 MPa / min. The maximum payne rebound was 10.8%. The final state showed a total seed binder of 30.2%, a chemical binder of 25.4%, a payne effect of 0.45 MPa, a Floc index of 0.0069 MPa / min, and a DIN abrasion of 81 mm³. It is 0.344. The value is 0.108, the 300% constant elongation stress is 13.0 MPa, and the tensile strength is 19.5 MPa.

[0176] This embodiment demonstrates that, while still within the scope of the present invention, a higher number of seeds can further enhance reinforcement and wear resistance.

[0177] (iv) Comparative Example

[0178] Comparative Example 1: Conventional One-Step Method

[0179] All silica, all rubber, and TESPT were added to the internal mixer in a single, initial stage, without seed masterbatch or cascade expansion. Results: Final Payne effect 0.61 MPa, Floc index 0.0128 MPa / min, total bond strength 21.4%, chemically bonded rubber 17.9%, DIN abrasion 102 mm³. It is 0.337. It is 0.124.

[0180] Note: In the single-process method, silica undergoes extensive direct contact in the early stages, resulting in numerous localized hard agglomerates and strong filler networks. This leads to significant network rebound and the worst overall performance.

[0181] Comparative Example 2: Ordinary High-Proportion Masterbatch Method

[0182] The initial stage used approximately 65% ​​silica and most of the rubber to prepare a standard masterbatch. The remaining silica was added later, but the seed window was not constrained, and Payne rebound was not controlled. Results: Final Payne effect 0.54 MPa, Floc index 0.0106 MPa / min, maximum Payne rebound 22.1%, DIN abrasion 94 mm³. It is 0.118.

[0183] Note: Although it is an improvement over the one-step process, the proportion of silica in the front section is too high, and premature densification in some areas is still obvious. The subsequent addition of silica cannot stably expand around the existing interface.

[0184] Comparative Example 3: Seed quantity too low

[0185] The ELBR system was similar to that in Example 3, but only 10% of the total silica was used in the S0 stage, with other conditions remaining similar. Results: The total seed binder was 19.1%, and the chemical binder was 14.6%, failing to reach the ideal seed window; the final Payne effect was 0.57 MPa, the Floc index was 0.0114 MPa / min, the maximum Payne rebound was 27.3%, and the DIN abrasion was 98 mm³.

[0186] Note: When the seed quantity is too low, it is difficult to form a sufficient number of effective interface nuclei, and the silica will still mainly aggregate with each other in the subsequent process.

[0187] Comparative Example 4: Excessive seed quantity and excessively strong forward coupling

[0188] A seed masterbatch was constructed using 50% silica, with excessive TESPT added in the first half of the process. Results: Total seed bond was 27.2%, chemical bond was 21.0%, but the seed payne effect was high; the final payne effect was 0.58 MPa, the Floc index was 0.0111 MPa / min, the maximum payne rebound was 24.1%, and the DIN abrasion was 88 mm³. It is 0.332. It is 0.121.

[0189] Note: Although the reinforcement level is high, the premature coupling and densification in the early stage make it difficult to expand in the later stage, which is not conducive to the overall balance of rolling resistance and wet gripping.

[0190] Comparative Example 5: Interface-free precursor

[0191] The seed silica content was set to 30%, but no interfacial precursor was added in the S0 stage; coupling was achieved solely through TESPT in the later stage. The other feeding methods were similar to those in Example 1. Results: total seed binder 21.8%, chemical binder 16.2%, final Payne effect 0.53 MPa, Floc index 0.0098 MPa / min, maximum Payne rebound 18.6%, DIN wear 93 mm³.

[0192] Note: When there are only front-end and back-end operations without an interface precursor, although a seed stage exists in form, the interface transition is not flexible enough, and the addition of silica can still easily form a new local network.

[0193] Comparative Example 6: No cascading extension is performed

[0194] The same seed masterbatch scheme as in Example 1 was used, but the remaining silica was added all at once after S1. Results: The seed window was basically met, but the final Payne effect was 0.56 MPa, the Floc index was 0.0102 MPa / min, the maximum Payne rebound was 23.5%, and the DIN abrasion was 95 mm³.

[0195] Note: Even with a good seed masterbatch, if multiple rounds of cascade expansion are not carried out subsequently, a significant structural rebound will still occur due to the concentrated entry of new silica.

[0196] Comparative Example 7: Not switching windows based on seed quality

[0197] The raw materials and feeding sequence were similar to those in Example 1, but the switching between S0, S1, and S2 was only based on fixed time and discharge temperature, and the total seed binder, chemical binder, and Floc index were not measured. Results: The final Payne effect was 0.52 MPa, the Floc index was 0.0096 MPa / min, the maximum Payne rebound was 17.4%, and the DIN abrasion was 92 mm³.

[0198] Note: Although superior to the completely one-time method, the batch stability and overall performance are not as good as the solution of this invention due to the large fluctuation in seed interface quality.

[0199] (v) Experimental Data

[0200] Table 1. Seed masterbatch and network structure indicators

[0201]

[0202] Table 2 Comprehensive Performance Test Results

[0203]

[0204] (vi) Results Analysis and Technical Effect Description

[0205] As shown in Table 1, the seed masterbatches of Examples 1-6 all reached the preset structural window before entering the cascade expansion stage. Therefore, their maximum Payne rebound was controlled within 10.8%, significantly lower than that of Comparative Examples 2, 3, 4, and 6. This indicates that the present invention does not simply improve the initial dispersion, but rather enables the newly added silica to complete wetting and embedding around the existing interface to a greater extent in the subsequent process, reducing the probability of the newly added silica reforming into a strong filler network.

[0206] Furthermore, the final Payne effect in Examples 1-6 was controlled between 0.40 and 0.45 MPa, and the Floc index was controlled between 0.0066 and 0.0076 MPa / min, which were significantly better than the comparative examples. This indicates that the present invention not only reduces the instantaneous packing network strength but also inhibits reflocculation behavior under thermal conditions.

[0207] As shown in Table 2, the embodiments of the present invention achieve a better balance between DIN wear, low-temperature dynamic performance, and high-temperature dynamic performance. Among them, Examples 2, 4, and 6 achieve the best balance between wear resistance and low rolling resistance; Examples 3 and 5 are superior in terms of dynamic performance at 0℃, indicating that different interface precursors and wheel extension designs can be adjusted to meet different performance requirements. In contrast, although Comparative Example 1 has the simplest process, its overall performance is the worst; although Comparative Example 4 has excessive reinforcement, its wet grip and rolling resistance are significantly damaged, proving that excessive seed quantity and excessively strong front coupling are not the technical path pursued by the present invention.

Claims

1. A method for the cascade dispersion of silica guided by a seed-based interfacial masterbatch, characterized in that, Includes the following steps: S0, Seed-type interface masterbatch construction steps: [The following is a partial translation of the original text, likely due to a formatting error, and is not translated:] ...of the total rubber amount... The amount of matrix rubber and total silica in A portion of silica, an interfacial precursor, and a first portion of sulfur-containing silane coupling agent are added to a Banbury mixer and mixed to obtain a seeded interfacial masterbatch. 25 to 55 portions It accounts for 15% to 40% of the total silica content. The interface precursor is an interface regulating compound that does not contain polysulfide bonds and contains silanol groups and / or rubber molecular chains on the silica surface that can be adsorbed, reacted or entangled. S1. Structural window determination step: Determine the total bound gum content of the seed interface masterbatch. Chemically bonded adhesive content Payne effect of uncured rubber and Floc index Only when , , , Only when at least three conditions are met simultaneously will the subsequent cascading expansion steps proceed; S2, Cascaded Expansion Step: The remaining silica is added in 2-4 rounds, and at least a portion of the remaining rubber, processing oil, and / or at least a portion of the second part of sulfur-containing silane coupling agent are added simultaneously during each round of addition, so that the newly added silica in each round is wetted and dispersed on the basis of the seed interface or expansion interface already formed in the previous round; wherein, the rebound of the Payne effect measured after each round of addition of new silica is no more than 25% relative to the end of the previous round; S3, Network Stabilization Step: Add the remaining rubber, the remaining sulfur-containing silane coupling agent, and the vulcanization system, and complete the final mixing to achieve a total binder content of 24%–38%, a chemical binder content of 18%–32%, and a Payne effect in the unvulcanized rubber composition. The pressure is 0.34–0.60 MPa, and the Floc index is [missing information]. The pressure is 0.004–0.011 MPa / min; in, The percentage of rubber that remains bound to the surface of silica after extraction with common solvents, relative to the total mass of rubber before extraction. The percentage of rubber remaining bound to the surface of silica after extraction with the aid of an ammonia-based medium, relative to the total mass of rubber before extraction. To specify the difference between the low-strain storage modulus and the high-strain storage modulus under the specified test conditions, This is to define the slope of the energy storage modulus as a function of time under insulation conditions.

2. The method according to claim 1, characterized in that, The interface precursor is selected from one or two of alkoxy-terminated polyether silane, epoxy-alkoxy silane, amino-alkoxy silane, anhydride-grafted liquid diene rubber, hydroxyl-terminated liquid polybutadiene, and epoxidized liquid polybutadiene.

3. The method according to claim 1 or 2, characterized in that, In step S0, the amount of the interface precursor added is 0.5 to 6 parts, and the amount of the first part of the sulfur-containing silane coupling agent added is 2 to 10 parts; in step S3, the amount of the second part of the sulfur-containing silane coupling agent added is 0 to 8 parts; the sulfur-containing silane coupling agent is selected from one or two of TESPT, TESPD, NXT, and P97.

4. The method according to claim 1, characterized in that, The total amount of silica used is 100-160 parts, preferably 115-150 parts; the CTAB specific surface area of ​​the silica is 140-260 m² / g.

5. The method according to claim 1, characterized in that, The base rubber, in 100 parts, includes 50 to 90 parts solution-polymerized styrene-butadiene rubber, 10 to 50 parts cis-butadiene rubber, and 0 to 25 parts natural rubber.

6. The method according to claim 1, characterized in that, In step S2, the amount of newly added silica in each round accounts for 20% to 45% of the total remaining silica; the mixing temperature during each round of addition is 95 to 140°C, the rotor speed is 35 to 80 rpm, and the discharge temperature is 120 to 155°C. And / or, in step S2, when the Payne rebound exceeds 18% after a certain round of new silica addition, rubber and / or processing oil are added simultaneously to reduce the probability of direct agglomeration between the newly introduced silica, and the next round of feeding is carried out after the Payne rebound recovers to below 18%. And / or, the tread rubber composition obtained at the end of step S3 satisfies the following conditions: total binder content of 24%–38%, chemical binder content of 18%–32%, and Payne effect of uncured rubber. The Floc exponent is 0.34–0.60 MPa. The pressure is 0.004–0.011 MPa / min, and the maximum Payne rebound in each round of the cascade expansion is no greater than 25%.

7. A tread rubber composition, characterized in that, It is prepared by the method described in any one of claims 1 to 6.

8. The tread rubber composition according to claim 7, characterized in that, It also includes 5 to 25 parts resin, 5 to 25 parts processing oil, 1 to 5 parts zinc oxide, 0.5 to 3 parts stearic acid, 1 to 5 parts antioxidant, 0.5 to 3 parts sulfur, and 0.5 to 4 parts accelerator.

9. A tire tread, characterized in that, It is prepared by vulcanization of the tread rubber composition comprising claim 7 or 8.

10. A pneumatic tire, characterized in that, Its tread portion includes the tread as described in claim 9.

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