Rubber composition of white carbon black network with open structure, preparation method and application

Abstract

The invention relates to the technical field of new rubber materials, in particular to a rubber composition of a white carbon black network with an open structure, a preparation method and application. According to the technology, monofunctional silane (XXSIL) is adopted to perform limited reaction covering on the surface of white carbon black, and under the action of a controlled-release water source and a condensation accelerator, liquid polybutadiene (LQBD) containing silane end groups is subjected to directional hydrolytic condensation between adjacent white carbon black aggregates to generate macromolecular bridges, so that an open network with communicated pores and channels is formed. Through segmented temperature and water content window control, the network shows a relatively low Payne effect and flocculation recovery after heat treatment in an RPA test, and can be verified by three-dimensional pore parameters. According to the scheme, the dynamic energy loss is remarkably reduced while reinforcement and wear resistance are maintained, so that the rolling resistance is reduced, the method is compatible with a conventional mixing-vulcanization process, and the process is stable.

Description

Technical Field

[0001] This invention relates to the field of new rubber materials technology, and in particular to a rubber composition with an open-structure silica network, its preparation method, and its application. Background Technology

[0002] Silica (precipitated silica) has become a key reinforcing filler in high-performance tire treads and various industrial rubber products due to its high specific surface area and ability to significantly improve the reinforcing and wet-skid properties of rubber materials. Unlike carbon black, silica is rich in silanol groups (Si–OH) on its surface, which readily form strong filler-filler interactions during mixing through hydrogen bonding and van der Waals forces. This leads to the formation of silica aggregates and agglomerates, resulting in high viscosity, high thixotropy, and difficult dispersion in the rubber compound. Simultaneously, the filler network exhibits a high storage modulus at small strains but rapidly decays at large strains, typically exhibiting a significant Payne effect. This further leads to a combination of problems, including increased dynamic heat generation, increased rolling resistance, and impaired low-temperature performance and fatigue resistance. To overcome the inherent defects of silica's "hydrophilicity and easy agglomeration", the industry has long used silane coupling agents to silanize it in situ or pre-treat it, so that the surface of silica changes from hydrophilic to relatively hydrophobic, and establishes chemical bonds between silica and rubber molecular chains, thereby reducing filler-filler interaction and improving reinforcement efficiency.

[0003] However, while traditional bifunctional or multifunctional silane coupling agents (such as sulfur-containing silane systems) improve interfacial bonding, they often introduce the risk of "local over-silanization / over-crosslinking." On the one hand, silane hydrolysis and condensation are highly dependent on temperature, shear, moisture content, and the conditions for the removal of volatile byproducts. On the other hand, multi-point condensation of silanes on the surface of silica may lead to the formation of denser filler networks or "hard clusters" in certain areas, resulting in improved macroscopic dispersion but a still relatively compact microstructure. This makes it difficult to reduce hysteresis loss to a more ideal level, and may even lead to a contradiction between reinforcement and low rolling resistance. Especially under the trend of high silica filling and low rolling resistance treads, re-agglomeration (flocculation) during the post-mixing resting or thermal history stages will be further aggravated, leading to drift in the dynamic properties of the rubber compound, poor processing stability, and increased batch-to-batch fluctuations in product performance. For the reasons mentioned above, the industry has begun to explore a synergistic approach of "silane coupling agent + functionalized liquid rubber / low molecular weight rubber". The aim is to use flexible segments and reactive end groups to more precisely control the interaction between the filler interface and the aggregate, thereby reducing the Payne effect while improving the thermal stability of the network.

[0004] For example, prior art CN109422938A discloses a rubber composition for pneumatic tire treads, the formulation of which includes a diene elastomer, silica, terminally capped mercaptosilane, and low molecular weight polybutadiene functionalized with alkoxysilane functional groups. The mercaptosilane and the functionalized low molecular weight polybutadiene synergistically affect the silica / rubber interface, improving silica dispersion and reducing dynamic hysteresis, thereby reducing rolling resistance while also considering other properties. The advantage of this approach is that by introducing low molecular weight polybutadiene segments that can condense with the silica surface, it is expected to reduce the localized structural hardening caused by the simple "rigid coupling" in traditional silane systems. However, in actual engineering implementation, the condensation reaction on the surface of silica is still affected by the combined effects of mixing temperature, rubber moisture content, volatile matter discharge and shear process. If the hydrolysis condensation reaction window is not properly controlled, functionalized low molecular weight polybutadiene may preferentially undergo aggregation grafting or self-condensation in local high-activity regions, which may induce new local densification structures. This makes it difficult to stably suppress re-agglomeration during the thermal history stage after mixing, resulting in limited repeatability of the so-called "low hysteresis" effect under batch, equipment or operating condition changes.

[0005] For example, CN113652010B discloses a "rubber composite material filled with silica that is synergistically modified by end-functionalized liquid rubber and mercaptosilane coupling agent and its preparation method". It emphasizes that by forming a chemical interface between silica and silica and constructing a pre-dispersed structure through end-functionalized liquid rubber and mercaptosilane, the interaction between silica and silica, rubber and silica and rubber and rubber is controlled by adjusting the graft chain density and structural rigidity, thereby improving mechanical strength and dynamic properties. This patent provides a relatively direct engineering path for "liquid rubber synergistic modification of silica", but its core still leans towards strengthening "interfacial chemistry / pre-dispersion structure": without more precise constraints on the water supply required for the condensation reaction, reaction segmentation and side reaction suppression, the liquid rubber and silane system may still form uncontrollable local high reaction density zones during the mixing process; especially when the goal is to build a more "open" inter-aggregate structure (to reduce filler network friction and energy loss), the description of "synergistic modification / formation of chemical interface" alone may still make it difficult to avoid problems such as structural shrinkage, secondary densification and flocculation rebound during the thermal history or storage stage, which in turn affects the consistency of rolling resistance and processing stability.

[0006] Furthermore, CN102219942A discloses a rubber composition containing treated silica, proposing the treatment of precipitated silica with a combination of allylsilane and dialkylsilane, and its application in sulfur-cured rubber compositions and tire products to improve the overall material properties. This technical approach of "treating silica with a combination of multiple silanes" indicates that by selecting silanes with different reactivity and structural characteristics, the surface state of silica and its dispersion / network characteristics in rubber can be controlled to a certain extent. However, existing solutions mostly focus on improving the "treatment agent formulation itself" or the "treatment process itself," often lacking operable segmented window control strategies for the contradictory relationship between hydrolysis and condensation kinetics, inter-aggregate bridging growth, and porosity maintenance during the mixing process. Simultaneously, regarding the re-agglomeration (flocculation) problem of filler networks after heat treatment / storage, existing technologies have not formed a unified, quantifiable structural criterion to distinguish between "open structure networks" and "dense flocculated networks," which makes the repeatability of related technologies under different equipment, different rubber moisture conditions, and different mixing energy inputs uncertain.

[0007] In summary, while existing technologies have proposed methods such as synergistically improving silica dispersion, reducing hysteresis, and enhancing mechanical properties through silane coupling agents, functionalized low-molecular-weight polybutadiene, or end-functionalized liquid rubber (e.g., CN109422938A, CN113652010B), and treating silica with compounded silanes to improve overall performance (e.g., CN102219942A), the following common challenges remain at the microstructural level required to achieve lower rolling resistance: Firstly, surface hydrolysis of silica... Condensation reactions are highly sensitive to moisture, temperature, and shear processes. Without controllable and reproducible reaction window management, localized densification and re-agglomeration are easily caused. Secondly, the rebound of flocculation during the post-mixing thermal history or storage stage is difficult to suppress stably, leading to dynamic property drift. Thirdly, existing publicly available solutions are more guided by formulation components or macroscopic properties, lacking a structural criterion that can stably distinguish and lock in the existence of pores / channels between aggregates that allow rubber molecules to penetrate. This limits the precise control and engineering reproduction of the morphology of silica network. Based on the above background, there is still an urgent need for a technical solution that can more stably construct and maintain an "open structure network" between silica aggregates to further reduce energy loss caused by filler-filler interactions, while also considering reinforcement, wear resistance, and processing stability. Summary of the Invention

[0008] The technical objective of this invention is to address the problems of high rolling resistance and poor performance stability caused by agglomeration, flocculation, and densification of filler networks in silica-reinforced rubber. This invention provides a material and method for controllably constructing an open-structure silica network. By using monofunctional silanes to perform limited reaction covering on the silica surface, and under controlled water release and condensation-promoting conditions, liquid polybutadiene containing silane end groups is oriented to form macromolecular bridges and interconnected pores between adjacent silica aggregates. This significantly reduces the Payne effect and post-heat treatment re-agglomeration (flocculation) while maintaining reinforcement and wear resistance, achieving a balance between low rolling resistance and high mechanical properties.

[0009] To achieve the objectives of this invention, the following technical solution is adopted:

[0010] A rubber composition of an open-structure silica network, the rubber composition comprising a rubber matrix and silica reinforcing filler, the silica being dispersed in the rubber matrix in the form of multiple aggregates; and a bridging system for directionally forming macromolecular bridges between the aggregates is introduced during the mixing process, the bridging system comprising at least:

[0011] a) Monofunctional silane XXSIL, which contains only one hydrolyzable silane group and whose organic end group is an inert group that does not participate in the sulfurization crosslinking reaction, is used to limit the reaction of silica surface to suppress dense silanization adhesion between aggregates.

[0012] b) Liquid polybutadiene (LQBD) with silane end groups, which is liquid polybutadiene with alkoxysilane groups at α and ω end groups and a weight-average molecular weight of 2000-50000, is used to form macromolecular bridges across aggregates by condensation reaction between adjacent silica aggregates.

[0013] c) Controlled-release water source and condensation accelerator, wherein the controlled-release water source is a microencapsulated water-releasing agent that releases water at 120–170°C, and the amount added is 0.05–0.50 phr; and the condensation accelerator is an organic acid or organotin / amine condensation catalyst, and the amount added is 0.005–0.20 phr.

[0014] The rubber composition is compounded using a segmented window control method: first, XXSIL is used to achieve limited reactive coverage of the silica surface at a compounding temperature of 110–140°C and a compound moisture content ≤0.20 wt%; then, at a compounding temperature of 130–170°C and a compound moisture content increased to 0.30–0.90 wt%, LQBD is used to undergo hydrolysis and condensation on the surfaces of different silica aggregates under the action of the water release source and condensation accelerator, thereby constructing an open network with pores and channels between the aggregates; and this network simultaneously satisfies the following criteria:

[0015] i) Payne effect ΔG' of uncured rubber compound after the first strain scan of RPA is ≤21dNm;

[0016] ii) The Flocculation index ΔG' of the uncured rubber compound after heat treatment in the third strain scan is ≤3.0dNm;

[0017] iii) When the vulcanized rubber is frozen and fractured, X-ray micro-CT or equivalent three-dimensional characterization is performed. The volume fraction of the connected pores in the silica-enriched phase is 2-15% and the median pore size is 0.2-3.0 μm.

[0018] Preferably, the rubber matrix comprises solution-polymerized styrene-butadiene rubber (SSBR) and / or butadiene rubber (BR), and the mass ratio of SSBR to BR is 20:80 to 80:20; and / or, per 100 parts of rubber matrix, the amount of silica is 30 to 120 phr, and the BET specific surface area of ​​the silica is 120 to 220 m². 2 / g.

[0019] Preferably, the XXSIL is an alkyl / aryl substituted alkoxysilane, and the inert group is one or more of C1-C12 alkyl, cycloalkyl, or phenyl groups, in order to improve the uniformity of coverage on the surface of silica and reduce the tendency for secondary cross-linking.

[0020] Preferably, the amount of XXSIL added is 0.2 to 8.0 phr, and after the XXSIL is added in the first window segment, the mixture continues to be mixed for 0.5 to 6.0 min before entering the second window segment.

[0021] Preferably, the alkoxysilane end groups at both ends of the LQBD are one or more of triethoxysilane end groups, trimethoxysilane end groups, or methoxy-ethoxy mixed alkoxysilane end groups.

[0022] Preferably, the amount of LQBD added is 1 to 40 phr, and the mass ratio of LQBD to XXSIL is 1:(2 to 30).

[0023] Preferably, the microcapsules of the controlled-release water source have an average particle size of 1–50 μm, and the microcapsule shell material is polyurea, polyurethane, melamine resin or a combination thereof, to achieve slow-release water in the range of 120–170°C.

[0024] Preferably, the condensation accelerator comprises dibutyltin dilaurate, dibutyltin dioctanoate, tertiary amine catalyst, p-toluenesulfonic acid, or a combination thereof.

[0025] Preferably, the moisture content of the compound is obtained by Karl Fischer moisture determination, near-infrared online moisture detection or equivalent methods, and the amount of water added is corrected by closed-loop correction based on the online detection results, so that the moisture content in the second window segment is stabilized at 0.30 to 0.90 wt%.

[0026] Preferably, the first and third strain scans in the RPA test are performed at the same test temperature and frequency, and the heat treatment temperature is 150-180℃ and the heat treatment time is 5-30min.

[0027] Preferably, the rubber composition further comprises 0-20 phr of carbon black and / or 0-30 phr of processing oil, and is used for reinforcement and process conditioning without breaking the dual threshold and pore structure criteria.

[0028] Furthermore, the present invention also provides a rubber product obtained by vulcanizing the rubber composition, wherein the rubber product is a tire tread compound, a tire sidewall compound, a belt layer buffer compound, a conveyor belt cover, a vibration damping component, or a seal.

[0029] Furthermore, the present invention also provides a method for constructing the open-structure silica network, comprising:

[0030] S1) Initially mix the rubber matrix and silica in a mixer or open mill;

[0031] S2) Control the mixing temperature to 110~140℃ and the moisture content of the mixed rubber to ≤0.20wt%. Add XXSIL and continue mixing so that XXSIL forms a limited reaction coating on the surface of silica.

[0032] S3) Adjust the mixing temperature to 130-170℃, and add controlled-release water and condensation accelerator to increase the moisture content of the mixed rubber to 0.30-0.90wt%. Then add LQBD simultaneously or in stages and continue mixing to allow LQBD to undergo hydrolysis and condensation on the surface of different silica aggregates to form trans-aggregate macromolecular bridges.

[0033] S4) After cooling, add the vulcanization system and other additives to complete the final mixing, shape and vulcanize to obtain an open-structure silica network with interconnected pores.

[0034] As a preferred option, LQBD in S3 is added in small amounts multiple times, with a single addition interval of 10 to 120 seconds, in order to suppress the densification and aggregation caused by local instantaneous condensation.

[0035] Preferably, the amount of water source added is corrected by online moisture detection during processes S2 and / or S3, so that the water content fluctuation in the second window segment does not exceed ±0.15wt%.

[0036] As a preferred option, the uncured rubber compound is pre-tested using RPA before final mixing. If either ΔG' first scan or ΔG' third scan exceeds the threshold, the ratio of XXSIL to LQBD and / or the mixing times of S2 and S3 are adjusted, and the compound is mixed again until the threshold is met.

[0037] Furthermore, the present invention also provides a tire, wherein at least one rubber component of the tire comprises the rubber article.

[0038] This invention, by employing the aforementioned technical solution, prevents silica from forming a traditional dense flocculated network in the rubber matrix. Instead, it stably generates trans-aggregate macromolecular bridges between adjacent aggregates while retaining interconnected pores and channels, significantly reducing dynamic energy loss caused by filler-filler contact and frictional slippage. Consequently, in the RPA test of uncured rubber, both a lower Payne effect and a lower flocculation rebound after heat treatment (both ΔG' single-sweep and ΔG' triple-sweep are low) can be achieved. Furthermore, this "open structure" can be verified through three-dimensional pore parameters (connected pore volume fraction, median pore size, etc.), resulting in better process repeatability and performance consistency under different equipment and batch conditions. At the product level, the tanδ@60℃ of tread rubber or other rubber products is significantly reduced, and rolling resistance is significantly improved. At the same time, because the silica-rubber interface bonding and network load-bearing capacity are still retained, key mechanical indicators such as tensile strength, tensile stress at a given elongation, abrasion resistance, and fatigue resistance can be maintained or improved, comprehensively achieving a multi-objective balance of "low rolling resistance, high reinforcement, low flocculation drift, and processing stability." Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0040] I. Terminology and Key Indicators

[0041] 1. Silica aggregates and open-structure networks

[0042] The term "silica aggregate" in this invention refers to a cluster structure formed by multiple primary silica particles through hydrogen bonding and physical adsorption. The term "open structure silica network" refers to a structure in a rubber matrix where adjacent silica aggregates do not form a dense flocculated skeleton through surface-to-surface contact, but rather form trans-aggregate macromolecular bridges between the aggregates through a "bridging system" while retaining a certain proportion of pores and channels. This allows rubber macromolecules to partially penetrate the space between the aggregates, thereby reducing filler-filler friction and energy dissipation.

[0043] 2. The meaning of monofunctional silanes (XXSIL)

[0044] The "monofunctional silane" referred to in this invention means that its organic end group is an inert end group (basically not involved in sulfur crosslinking or secondary crosslinking). Its mechanism of action is to limit the reaction coverage and hydrophobic control of the silanol groups on the surface of silica, reduce the strong polar attraction and local excessive condensation tendency on the surface of silica, thereby reserving steric hindrance and reaction site distribution for subsequent "bridging growth".

[0045] 3. The meaning of silane-terminated liquid polybutadiene (LQBD)

[0046] LQBD is a low-viscosity liquid polybutadiene with hydrolyzable alkoxysilane end groups (such as triethoxysilane, trimethoxysilane, or mixed alkoxysilanes) at the ends of its molecular chains. Under suitable moisture and catalytic conditions, it can condense with the surface of silica and form long-chain bridges between adjacent aggregates.

[0047] 4. Controlled release water source and condensation accelerator

[0048] The controlled water release source is a microencapsulated water-releasing agent (e.g., water / glycerol as the core material and polyurea or polyurethane as the shell material) that releases water in the range of 120–170°C, used to provide the water required for hydrolysis and condensation in the "second window segment"; the condensation promoter can be an organic acid or an organotin / amine condensation catalyst, used to promote the condensation bonding between silane end groups and the surface of silica within the temperature window.

[0049] The Payne effect (ΔG' single-scan) and the Flocculation index (ΔG' triple-scan) were measured using RPA to perform strain scanning on uncured rubber, recording the difference in storage modulus between low and high strain conditions. The values ​​are defined as follows:

[0050] ;

[0051] The low strain can be selected as 0.56% (or 0.5%), and the high strain can be selected as 100% (or 50%). The test temperature and frequency are kept consistent across all samples.

[0052] ΔG' first scan: obtained from the first strain scan .

[0053] ΔG' third scan: obtained by performing a third strain scan on the sample after heat treatment. (Reflects thermal history / re-aggregation after resting and network reconstruction tendency).

[0054] The present invention preferably uses "ΔG' first scan ≤ 21dNm and ΔG' third scan ≤ 3.0dNm" as one of the criteria for open structure networks.

[0055] 5. Three-dimensional pore structure parameters

[0056] After freezing and fracture of the vulcanized rubber samples, the pore structure of the silica-enriched phase was obtained by X-ray micro-CT or equivalent three-dimensional characterization, yielding the volume fraction of connected pores (%) and the median pore size (μm). Preferably, the volume fraction of connected pores in this invention is 2–15%, and the median pore size is 0.2–3.0 μm.

[0057] II. Raw Materials, Equipment and Pretreatment

[0058] 1.Raw materials

[0059] Rubber matrix: solution styrene-butadiene rubber (SSBR, medium Mooney viscosity) and butadiene rubber (BR, high cis).

[0060] Silica: Precipitated silica, with a specific surface area of ​​120–220 m² / g. 2 / g (150-180m in this embodiment) 2 / g range).

[0061] XXSIL: Monofunctional silanes with inert end groups that are alkyl / aryl substituted; varieties include: propyltriethoxysilane, methyltriethoxysilane, phenyltriethoxysilane, etc. (one or more can be combined).

[0062] LQBD: Liquid polybutadiene with α and ω-terminal alkoxysilanes, with a weight-average molecular weight (Mw) of 2000–50000.

[0063] Controlled water release source: Microencapsulated water release agent (core material can be water / glycerol or water / low molecular weight polyol mixture; shell material is polyurea, polyurethane or melamine resin).

[0064] Condensation accelerators: dibutyltin dilaurate (DBTDL), dibutyltin dioctanoate, tertiary amine accelerators, or p-toluenesulfonic acid, etc.

[0065] Other additives: small amounts of carbon black (0-20 phr optional), processing oil, zinc oxide, stearic acid, antioxidants, sulfur and accelerators (such as CBS / NS, TBzTD, etc.), selected according to conventional tread formulation systems.

[0066] 2. Equipment

[0067] Internal mixer: 1.6L or 270L (suitable for laboratory / production), equipped with top plug and rotor, preferably with exhaust / vacuum interface.

[0068] Open mill: used for tableting, cooling, and final mixing of vulcanization systems.

[0069] Moisture detection: Karl Fischer moisture meter (offline) or near-infrared online moisture detection (optional).

[0070] Testing equipment: RPA, DMA, tensile testing machine, DIN abrasion tester, hardness tester, micro-CT (or equivalent three-dimensional characterization).

[0071] 3. Key pretreatment

[0072] To ensure that the moisture content of the first window section is ≤0.20wt%, at least one of the following is preferred:

[0073] Dry the silica at 100–120°C for 2–4 hours and store it in a sealed container.

[0074] Rubber, oils, and additives are sealed and equilibrated at room temperature to prevent moisture absorption;

[0075] Preheat the internal mixer before feeding materials and run it idle for a short time to remove moisture;

[0076] The first window section is opened to exhaust or slightly evacuate to remove volatiles.

[0077] III. Preparation Method (General Process Flow)

[0078] The following is the general process; the specific implementation examples only differ in the dosage, order of addition, and window control details:

[0079] (1) First window segment: limited reaction coverage (110~140℃, water content ≤0.20wt%)

[0080] a) Add SSBR and BR, and masticate at low speed for 30-60 seconds;

[0081] b) Add silica in batches (70% can be added first), and add some processing oil to wet it;

[0082] c) Control the glue temperature at 110-140℃, add XXSIL and mix for 0.5-6 minutes to allow XXSIL to perform a limited reaction coating on the surface of silica.

[0083] d) During this period, maintain the moisture content of the compound rubber at ≤0.20wt%, and vent or vacuum if necessary.

[0084] (2) Second window segment: controlled water release + directional bridging condensation (130~170℃, water content 0.30~0.90wt%)

[0085] a) Raise the adhesive temperature to 130–170°C;

[0086] b) Add controlled-release water and condensation accelerator to increase and stabilize the moisture content of the rubber compound at 0.30–0.90 wt%;

[0087] c) Add LQBD simultaneously or at different times (preferably in small amounts and multiple times), and continue to mix so that the LQBD end groups undergo hydrolysis and condensation on the surface of different silica aggregates, forming trans-aggregate macromolecular bridges and interconnected pores.

[0088] d) When the torque stabilizes and the displacement decreases, the main mixing process ends.

[0089] (3) Final mixing and vulcanization

[0090] a) Cool the main mixed adhesive to <60℃ after sheeting;

[0091] b) Add sulfur, accelerators and other vulcanization systems to the open mill or low-temperature mixing section (control the rubber temperature <100℃) to complete the final mixing;

[0092] c) Calendering, extrusion, or molding as needed;

[0093] d) Curing at 150-170℃ for 10-25 minutes (adjusted according to the thickness of the product and the formulation system).

[0094] IV. Testing Methods

[0095] 1. RPA Testing (Payne and Three-Scan Metrics)

[0096] Sample: Uncured rubber;

[0097] Test temperature: 60℃ (or a specified uniform temperature); Frequency: 1.67Hz (or 1Hz);

[0098] Strain scan: 0.56% → 100% (logarithmic or linear stepping is acceptable, but consistency across all samples is required);

[0099] Record: and ,calculate ;

[0100] Heat treatment: Place the sample at 160℃ for 10 min (or at 150~180℃ for 5~30 min under the same conditions).

[0101] Repeat the scan up to the third time to obtain ΔG' three scans.

[0102] 2. Three-dimensional pore structure (micro-CT)

[0103] Take the vulcanized rubber, freeze it with liquid nitrogen until it becomes brittle, and cut a test piece of about 5×5×5mm.

[0104] Micro-CT resolution: voxel 1–5 μm;

[0105] Image segmentation: Threshold segmentation of the enriched / porosity phase of silica;

[0106] Output: Connected pore volume fraction (%), pore size distribution, and median pore size (μm).

[0107] 3. Dynamic Performance (DMA)

[0108] 10Hz, 0.1–0.5% small strain; temperature scan or constant temperature;

[0109] Take at 60℃ As an indicator related to rolling resistance (consistent across the board).

[0110] 4. Mechanics and Wear

[0111] Tensile strength and stress at a given elongation: in accordance with GB / T528 or equivalent;

[0112] DIN wear: according to DIN 53516;

[0113] Hardness: Shore A.

[0114] V. Examples and Comparative Examples

[0115] 1. Formulation Standards (Unified Matrix and Basic Additives)

[0116] Unless otherwise specified, the baseline formulations for each sample are as follows (unit: phr), based on 100 parts of rubber matrix (SSBR+BR):

[0117] SSBR: 60; BR: 40;

[0118] Silica: 80; (can contain 0-10% carbon black for fine-tuning)

[0119] Processing oil: 10;

[0120] Zinc oxide: 2; Stearic acid: 2; Antioxidant: 1.5;

[0121] Sulfur: 1.6; Accelerator (CBS / NS, etc.): 1.2; (Added in the final mixture)

[0122] Each embodiment is designed differently in terms of "XXSIL, LQBD, controlled release water source, condensation accelerator" and window control conditions.

[0123] 2. Example 1

[0124] XXSIL: Propyltriethoxysilane 2.0 phr;

[0125] LQBD: α,ω-triethoxysilane-terminated liquid polybutadiene, Mw≈10000, 10 phr;

[0126] Controlled water release source: 0.20 phr microcapsule water release agent (releases water at 120–170°C);

[0127] Condensation accelerator: DBTDL 0.05 phr.

[0128] Mixing steps:

[0129] First window segment: 110~135℃, moisture content ≤0.20wt%, mix for 3min after adding XXSIL;

[0130] Second window segment: Raise to 150-165℃, first add microcapsule water-releasing agent and DBTDL, wait 60s and then add LQBD in 3 parts (60s apart each time), mix for a total of 4 minutes; discharge temperature 155-160℃; final mixing vulcanization system <95℃.

[0131] Results: A stable open network was formed, and the RPA dual threshold and microCT porosity index both met the scope of this invention. The tanδ@60℃ was significantly reduced while maintaining mechanical properties.

[0132] 3. Example 2

[0133] XXSIL: Phenylacetyltriethoxysilane 1.5 phr;

[0134] LQBD: Mw≈8000, 8phr;

[0135] Controlled water release source: 0.15 phr;

[0136] Condensation accelerator: p-toluenesulfonic acid 0.02 phr (or equivalent organic acid).

[0137] Window: The first window segment maintains low water content; the second window segment is at 145-160℃. LQBD is added simultaneously with the water release source and acid catalyst immediately after addition, and the mixture is stirred for 3.5 minutes.

[0138] Results: ΔG' was low in both the first and third scans, and microCT showed that the interconnected pores were in the range of 2-12%, indicating improved rolling resistance.

[0139] 4. Example 3

[0140] XXSIL: Methyltriethoxysilane 2.5 phr;

[0141] LQBD: Mw≈30000, 6phr;

[0142] Controlled water release source: 0.25 phr;

[0143] Condensation accelerator: Dibutyltin dioctanoate 0.03 phr.

[0144] The second window segment uses a "small amount, multiple times" approach to add LQBD (4 times), and extends the mixing time to 5 minutes to ensure long-chain bridging growth.

[0145] Results: The median pore size increased slightly (more channel-like), tanδ@60℃ decreased further, and the tensile strength remained the same.

[0146] 5. Example 4

[0147] XXSIL: Propyltriethoxysilane 0.5 phr;

[0148] LQBD: Mw≈10000, 12phr;

[0149] Water release source: 0.20 phr;

[0150] DBTDL: 0.05phr.

[0151] Results: An open network can still be formed, but the Payne is slightly higher than in Example 1, indicating that insufficient XXSIL coverage leads to partial agglomeration enhancement due to the residual polarity on the surface of silica; the threshold is still met and rolling resistance is improved, indicating that the invention is feasible within the scope of this invention.

[0152] 6. Example 5

[0153] XXSIL: Phenylacetyltriethoxysilane 6.0 phr;

[0154] LQBD: Mw≈8000, 6phr;

[0155] Water release source: 0.15 phr;

[0156] Amine condensation accelerator: 0.08 phr.

[0157] The first window segment is controlled to be shorter (1.5-2 min) to prevent excessive coverage and insufficient interface reaction sites; the second window segment adopts synchronous addition.

[0158] Results: ΔG' is low in the third sweep and porosity still exists, but if XXSIL is too high and the first segment is too long, it will lead to insufficient bridging (see Comparative Example E for comparison). Therefore, this example achieves a stable effect by controlling the duration of the first segment.

[0159] 7. Example 6

[0160] Add carbon black N2348 phr to the baseline formulation, while reducing the silica to 72 phr;

[0161] XXSIL: 2.0 phr; LQBD: 10 phr; Release source: 0.20 phr; DBTDL: 0.05 phr.

[0162] Results: The open structure criterion is still met, the mechanical strength increases slightly, and the tanδ@60℃ is still significantly lower than that of the control sample, proving that the present invention is compatible with conventional carbon black synergistic reinforcement system.

[0163] 8. Example 7

[0164] Based on Example 1, near-infrared online moisture detection was introduced to perform closed-loop correction on the moisture content of the second window segment: when the detected value is <0.30wt%, 0.02phr of microcapsule water-releasing agent was added; when it is >0.90wt%, the venting time was extended and the reference amount of water-releasing agent for the next batch was reduced.

[0165] Results: The inter-batch ΔG' three-scan fluctuation was significantly reduced, and the pore volume fraction distribution was more concentrated, demonstrating the advantage of repeatability in industrial scale-up.

[0166] 9. Example 8 (Changing the shell material of the water release source to verify that the water release source is replaceable)

[0167] The water source was melamine resin shell microcapsules with a particle size of 5–30 μm and a pH of 0.18; the rest was the same as in Example 1.

[0168] Result: The threshold and pore parameters are still satisfied, indicating that the water source can be replaced equivalently within the scope of this invention.

[0169] VI. Comparative Example

[0170] 1. Comparative Example A

[0171] No LQBD or release water source added;

[0172] A conventional bifunctional sulfur-containing silane (e.g., the TESPT system) was used to replace 6 phr in equal amounts.

[0173] Phenomenon: Payne may decrease initially, but flocculation rebounds significantly after heat treatment, and ΔG' is high in three scans; microCT shows low connected pore volume fraction and small pore size (forming a dense network), and tanδ@60℃ shows limited decrease or large fluctuations.

[0174] 2. Comparative Example B

[0175] Add only LQBD 10 phr, water source 0.20 phr, and DBTDL 0.05 phr; do not add XXSIL.

[0176] Phenomenon: LQBD tends to shrink and induce local densification in highly active local areas, resulting in increased mixing viscosity and unstable dispersion; ΔG' in the first sweep is too high, and ΔG' in the third sweep is difficult to meet ≤3.0dNm.

[0177] 3. Comparative Example C

[0178] The process does not involve drying the silica; the moisture content in the first window section is approximately 0.45 wt%.

[0179] Both XXSIL and LQBD are added to the first window segment.

[0180] Phenomenon: Premature bridging reaction and high local crosslinking density make silica more prone to "clumping together", resulting in higher Payne and three-scan indexes, a more closed / dispersed pore structure, and unstable rolling resistance improvement.

[0181] Comparative Example D

[0182] 4. The first window is completed according to Example 1;

[0183] LQBD is added at temperatures above 180°C and close to the discharge point (or during the final mixing stage). Observations: Insufficient condensation window, insufficient bridging growth, more local surface grafting than cross-aggregate bridging; ΔG' three-scan is still too high, and the pore volume fraction is insufficient.

[0184] 5. Comparative Example E

[0185] XXSIL8phr, and the first window segment mixes for 6 minutes;

[0186] LQBD8phr, the rest is the same as in Example 1.

[0187] Phenomenon: Excessive coverage effectively reduces the condensable sites on the surface of silica, making it difficult for LQBD to form sufficient bridging between different aggregates, resulting in a decrease in pore volume fraction and limited improvement at tanδ@60℃. This demonstrates that "limited reaction coverage" needs to be matched with bridging growth.

[0188] 6. Comparative Example F

[0189] DBTDL 0.30 phr (significantly higher than the preferred upper limit), water source 0.25 phr;

[0190] Phenomenon: Rapid condensation leads to localized gel clusters, deterioration of dispersion, and increases in both the first and third sweeps of ΔG', resulting in greater mechanical fluctuations.

[0191] VII. Data Summary

[0192] Table 1 RPA index and pore structure

[0193] serial number XXSIL / phr LQBD / phr(Mw) Water source / phr catalyst / phr ΔG′ scan (dNm) ΔG′ triple scan (dNm) Connected pore volume fraction (%) Median pore size (μm) Example 1 2.0 10 (10,000) 0.20 0.05 18.0～20.0 2.2～2.9 5～12 0.6～1.8 Example 2 1.5 8 (0.8 million) 0.15 0.02 18.5～20.5 2.1～2.8 4～10 0.5～1.6 Example 3 2.5 6 (30,000) 0.25 0.03 17.5～20.5 2.0～2.7 6～15 0.8～2.5 Example 4 0.5 12 (10,000) 0.20 0.05 19.5～21.0 2.4～3.0 3～9 0.4～1.5 Example 5 6.0 6 (8,000) 0.15 0.08 18.5～20.5 2.2～2.9 3～8 0.4～1.2 Example 6 2.0 10 (10,000) 0.20 0.05 18.0～20.5 2.2～2.9 4～11 0.5～1.7 Example 7 2.0 10 (10,000) 0.18～0.22 0.05 18.0～20.0 2.1～2.6 5～12 0.6～1.8 Example 8 2.0 10 (10,000) 0.18 0.05 18.0～20.5 2.2～2.8 4～11 0.5～1.7 Comparative Example A — — — — 21.5～25.0 3.8～6.0 0.5～2.0 0.1～0.4 Comparative Example B — 10 (10,000) 0.20 0.05 21.0～24.0 3.2～5.5 1.0～3.0 0.2～0.6 Comparative Example C 2.0 10 (10,000) 0.20 0.05 22.0～26.0 4.0～6.5 0.8～2.5 0.1～0.5 Comparative Example D 2.0 10 (10,000) 0.20 0.05 20.5～23.0 3.5～5.8 1.0～3.0 0.2～0.6 Comparative Example E 8.0 8 (0.8 million) 0.20 0.05 20.5～23.5 3.1～4.8 1.0～3.5 0.2～0.7 Comparative Example F 2.0 10 (10,000) 0.25 0.30 22.0～26.0 3.8～6.2 0.5～2.5 0.1～0.5

[0194] Table 2 Dynamic and Mechanical Properties (Vulcanized Rubber)

[0195] serial number tanδ@60℃ Tensile strength (MPa) 300% constant tensile stress (MPa) <![CDATA[DIN wear (mm 3 )]]> Example 1 0.085～0.105 9.0～11.5 5.5～7.0 85～105 Example 2 0.090～0.110 9.0～11.0 5.4～6.8 88～110 Example 3 0.080～0.100 9.2～11.6 5.6～7.2 82～102 Example 4 0.095～0.115 8.8～11.0 5.2～6.6 88～112 Example 5 0.095～0.120 8.8～11.2 5.1～6.7 90～115 Comparative Example A 0.120～0.150 8.0～10.5 5.3～7.0 95～125 Comparative Example B 0.115～0.145 7.8～10.2 5.0～6.8 98～130 Comparative Example C 0.120～0.160 7.5～10.0 5.4～7.5 100～140 Comparative Example D 0.115～0.150 8.0～10.3 5.2～6.9 96～130 Comparative Example F 0.120～0.165 7.0～9.8 5.8～8.2 105～150

[0196] VIII. Comprehensive Technical Description

[0197] 1. General Rules of Examples

[0198] As shown in Table 1, under different XXSIL types, different LQBD molecular weights and dosages, different catalytic systems, and different water release sources, Examples 1-8 all achieved a stable ΔG' value of ≤21 dNm in the first scan and maintained ΔG' ≤3.0 dNm in the third scan after heat treatment. Simultaneously, micro-CT showed that the volume fraction of connected pores reached 2-15%, and the median pore size was between 0.2 and 3.0 μm. These results indicate that the open structure of this invention is not a random dispersion phenomenon, but a structural achievement jointly determined by "limited reaction coverage—controlled water release—directional bridging condensation—verifiable three-dimensional pores," and therefore exhibits reproducibility within the scope defined by this invention.

[0199] 2. The necessity of proving key features through proportion

[0200] Comparative Example A demonstrates that while traditional silane systems can improve the interface to some extent, they tend to form a denser filler network, resulting in a significant increase in flocculation after thermal history, making it difficult to simultaneously achieve low ΔG' three-sweep ratios and sufficient interconnected pores. Comparative Example B demonstrates that without the reaction-limiting coverage of XXSIL, LQBD condensation tends to localize and densify, leading to higher Payne and three-sweep ratios. Comparative Examples C and D demonstrate that without controlling moisture and temperature windows (too early / too late condensation), bridging cannot grow across aggregates at the appropriate stage, making it difficult to establish or maintain open pores. Comparative Examples E and F further demonstrate that reaction-limiting coverage and bridging growth need to be matched; excessive catalysis can cause excessively rapid condensation and gel clusters, transforming the network from "open" to "dense and unstable."

[0201] 3. Combined contribution to rolling resistance and mechanical reinforcement

[0202] Table 2 shows that the tanδ@60℃ of the embodiment is significantly lower than that of the comparative example, indicating that the rolling resistance-related hysteresis loss is reduced. At the same time, tensile strength, constant elongation stress and wear are not sacrificed, indicating that the open structure is not "weakening and reinforcing", but achieves the goal of "low rolling resistance and reinforcement" by reducing the energy consumption of filler-filler friction and improving the wetting efficiency of rubber molecules between aggregates and stress transmission efficiency.

[0203] The foregoing description of embodiments of the present invention, through which those skilled in the art are able to implement or use the present invention, will be readily apparent to those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novelty disclosed herein.

Claims

1. A rubber composition of an open-structure silica network, characterized in that: The rubber composition comprises a rubber matrix and a silica reinforcing filler, wherein the silica is dispersed in the rubber matrix in the form of multiple aggregates; Furthermore, a bridging system for the directional formation of macromolecular bridges between aggregates is introduced during the mixing process, the bridging system comprising at least: a) Monofunctional silane XXSIL, which contains only one hydrolyzable silane group and whose organic end group is an inert group that does not participate in the sulfurization crosslinking reaction, is used to limit the reaction of silica surface to suppress dense silanization adhesion between aggregates. b) Liquid polybutadiene (LQBD) with silane end groups, which is liquid polybutadiene with alkoxysilane groups at α and ω end groups and a weight-average molecular weight of 2,000 to 50,000, used to form macromolecular bridges across aggregates by condensation reaction between adjacent silica aggregates. c) A controlled-release water source and a condensation accelerator, wherein the controlled-release water source is a microencapsulated water-releasing agent that releases water at 120–170°C, and the amount added is 0.05–0.50 phr; and the condensation accelerator is an organic acid or an organotin / amine condensation catalyst, and the amount added is 0.005–0.20 phr. The rubber composition is mixed using a segmented window control method: first, XXSIL is used to complete the limited reaction coverage of the silica surface under the conditions of a mixing temperature of 110–140°C and a mixed rubber moisture content of ≤0.20 wt%; then, under the conditions of a mixing temperature of 130–170°C and a mixed rubber moisture content of 0.30–0.90 wt%, LQBD is used to undergo hydrolysis and condensation on the surface of different silica aggregates under the action of the water release source and condensation accelerator, thereby constructing an open network with pores and channels between the aggregates.

2. The rubber composition according to claim 1, characterized in that: The rubber matrix comprises solution-polymerized styrene-butadiene rubber (SSBR) and / or butadiene rubber (BR), and the mass ratio of SSBR to BR is 20:80 to 80:

20. Preferably, the amount of silica used is 30-120 phr per 100 parts of rubber matrix, and the BET specific surface area of ​​the silica is 120-220 m² / g. And / or, the XXSIL is an alkyl / aryl substituted alkoxysilane, and the inert group is one or more of C1-C12 alkyl, cycloalkyl, or phenyl groups; Preferably, the amount of XXSIL added is 0.2 to 8.0 phr, and after the XXSIL is added in the first window segment, the mixing continues for 0.5 to 6.0 min before entering the second window segment.

3. The rubber composition according to claim 1, characterized in that: The alkoxysilane end groups at both ends of the LQBD are one or more of triethoxysilane end groups, trimethoxysilane end groups, or methoxy-ethoxy mixed alkoxysilane end groups; preferably, the amount of LQBD added is 1 to 40 phr, and the mass ratio of LQBD to XXSIL is 1:(2 to 30).

4. The rubber composition according to claim 1, characterized in that: The controlled-release water source has microcapsules with an average particle size of 1–50 μm, and the microcapsule shell material is polyurea, polyurethane, melamine resin or a combination thereof, to achieve slow-release water in the range of 120–170°C; preferably, the condensation accelerator includes dibutyltin dilaurate, dibutyltin dioctanoate, tertiary amine catalyst, p-toluenesulfonic acid or a combination thereof.

5. The rubber composition according to claim 1, characterized in that: The moisture content of the compound was obtained by Karl Fischer moisture determination, near-infrared online moisture detection, or equivalent methods. The amount of water added was corrected using the online detection results in a closed loop to stabilize the moisture content in the second window segment at 0.30–0.90 wt%. Preferably, the first strain scan and the third strain scan in the RPA test are performed at the same test temperature and frequency, and the heat treatment temperature is 150-180℃ and the heat treatment time is 5-30 min.

6. The rubber composition according to claim 1, characterized in that: The rubber composition further comprises 0-20 phr of carbon black and / or 0-30 phr of processing oil, and is used for reinforcement and process conditioning without compromising the dual threshold and pore structure criteria.

7. A rubber product, characterized in that: The rubber product is obtained by vulcanizing the rubber composition according to any one of claims 1 to 6, and the rubber product is a tire tread rubber, tire sidewall rubber, belt layer buffer rubber, conveyor belt cover rubber, vibration damping component or seal.

8. A method for constructing the open-structure silica network according to any one of claims 1 to 6, characterized in that, include: S1) Initially mix the rubber matrix and silica in a mixer or open mill; S2) Control the mixing temperature to 110~140℃ and the moisture content of the mixed rubber to ≤0.20 wt%, add XXSIL and continue mixing so that XXSIL forms a limited reaction coating on the surface of silica. S3) Adjust the mixing temperature to 130-170℃, and add controlled-release water and condensation accelerator to increase the moisture content of the mixed rubber to 0.30-0.90 wt%. Then add LQBD simultaneously or in stages and continue mixing to allow LQBD to undergo hydrolysis and condensation on the surface of different silica aggregates to form trans-aggregate macromolecular bridges. S4) After cooling, add the vulcanization system and other additives to complete the final mixing, shape and vulcanize to obtain an open-structure silica network with interconnected pores.

9. The method according to claim 8, characterized in that: In S3, LQBD is added in small amounts multiple times, with a single addition interval of 10–120 s, in order to suppress the densification and aggregation caused by local instantaneous condensation; And / or, during processes S2 and / or S3, the amount of water source added is corrected by online moisture detection to ensure that the moisture content fluctuation in the second window does not exceed ±0.15 wt%; And / or perform RPA pre-test on the uncured rubber compound before final mixing. If either ΔG′ first scan or ΔG′ third scan exceeds the threshold, adjust the ratio of XXSIL to LQBD and / or the mixing time of S2 and S3, and then mix again until the threshold is met.

10. A tire, characterized in that: At least one rubber component of the tire comprises the rubber article of claim 7.