Bio-based rubber solid softener and its preparation method and application method

Abstract

The present application relates to the technical field of polymer materials and rubber additives, in particular to a bio-based rubber solid softener and its preparation method and application method. The solid softener comprises precipitated white carbon black and a pre-reaction modified oil phase loaded in the pore channel of the precipitated white carbon black. The preparation method comprises the following steps: first, vacuum dewatering and pretreatment of the precipitated white carbon black; then, catalytic reaction of each oil phase component and TEOA in a reaction kettle to obtain a pre-reaction modified oil phase; finally, loading the oil phase in the pore channel of the carrier by high-speed adsorption to obtain a powder-like solid softener. When applied to rubber mixing, the solid softener replaces the traditional liquid softening oil according to the equivalent deduction rule. The pre-reaction oil phase carries residual TEOA to infiltrate the surface of the white carbon black, thereby improving the dispersibility of the filler and reducing the Mooney viscosity and rolling resistance. The present application has the advantages of high bio-based content, good processing performance, excellent product durability and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer materials and rubber additives, specifically to bio-based solid rubber softeners and their preparation and application methods. Background Technology

[0002] In the tire and rubber product industry, precipitated silica has become a core reinforcing filler for high-performance tire treads due to its ability to impart low rolling resistance and excellent wet skid resistance to rubber compounds. However, the presence of numerous silanol groups on the surface of silica allows for easy hydrogen bonding between particles, forming a filler network that leads to increased Mooney viscosity and dispersion difficulties in the compound. Industrially, liquid petroleum-based aromatic oils or naphthenic oils are typically added as softeners to improve processing performance. However, liquid softeners have inherent drawbacks such as inconvenient transportation, inaccurate weighing, difficulty in addition, and a tendency to leak or spill. Furthermore, the small-molecule oil phase is prone to migration during long-term use, leading to deterioration of product performance.

[0003] To address the process defects of liquid plasticizers, Chinese patent application CN106674711A, published on May 17, 2017, discloses a solid plasticizer for rubber. This method utilizes carbon nanotubes and highly adsorbent fillers to adsorb various types of plasticizers, and adds thermoplastic polymers to prevent clumping, thus achieving solid powder form of the plasticizer. However, the oil phase used in this solution is an unmodified ordinary plasticizer with a small molecular weight, resulting in limited fixation in the rubber crosslinking network. Furthermore, it relies on the physical fixation of the oil phase by thermoplastic polymers, without involving the chemical modification of the oil phase itself.

[0004] Chinese patent application CN113667312A, published on November 19, 2021, discloses a precipitated silica-supported plasticizer. The plasticizer is prepared by physically mixing and drying precipitated silica, which improves the plasticizer's feed efficiency and addresses low-temperature transportation issues. However, this solution only involves pure physical mixing; there is no chemical relationship between the plasticizer and the carrier, and it does not address the compounding of accelerators or methods for application deduction.

[0005] Regarding the modification of bio-based oils, Chinese patent application CN109467770A, published on March 15, 2019, discloses a rubber composite material modified with cashew phenol glycidyl ether. This modification utilizes the epoxy groups of cashew phenol glycidyl ether to react with the hydroxyl groups on the surface of the silica, achieving in-situ grafting modification. Chinese patent application CN114920989A, published on August 19, 2022, discloses a method for applying cashew phenol in rubber. This involves synthesizing a sulfur-containing borate ester intermediate through the reaction of boric acid and 1-thioglycerol, followed by reaction with cashew phenol to obtain a modified cashew phenol compound. This modified compound is used as an additive in rubber compounding, improving the dispersibility and crosslinking density of silica. Both of these methods involve the chemical modification of cashew phenol, but the modified product is added directly to the rubber as a single additive, rather than being pre-prepared as a supported solid softener. Chinese patent application CN121975202A, published on May 5, 2026, discloses a tread rubber composition that uses functional oil to improve the reinforcement of silica. This method introduces silane-terminated polyether-modified vegetable oil as an anchorable bio-based functional oil, utilizing the chemical bonding between the silane end groups and the silica surface to improve filler dispersion. While this approach achieves interfacial anchoring between the functional oil and silica, the functional oil remains liquid, failing to address the issue of solid-state processing.

[0006] In summary, existing technologies lack a softener product that combines oil-phase chemical modification with solid powdering. How to increase the molecular weight of the oil phase through chemical pre-reaction during the preparation stage, while simultaneously achieving solid feeding, maintaining low Mooney viscosity, and good dispersibility during application, is a pressing technical challenge in this field. Furthermore, how to prevent scorching during the mixing stage while introducing vulcanization accelerators is also a technical problem that needs to be solved. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a bio-based rubber solid softener. This invention employs a preparation stage that, through the compounding of specific components, effectively improves the fixation rate of the softener in the rubber network and the dispersibility of the filler without increasing the viscosity of the rubber compound.

[0008] The first objective of this invention is to provide a bio-based rubber solid softener.

[0009] It includes precipitated silica and a pre-reacted modified oil phase loaded in the pores of the precipitated silica (the loading includes capillary forces, van der Waals forces and hydrogen bonding between triethanolamine and the silanol groups on the surface of silica). The content of the precipitated silica is 30wt%-40wt% by mass percentage, and the content of the pre-reactive modified oil phase is 60wt%-70wt%. The pre-reaction modified oil phase includes a pre-reaction modified oil phase intermediate and a vulcanization accelerator; The pre-reaction modified oil phase intermediate is prepared by the following components in parts by weight via triethanolamine-catalyzed ring-opening polymerization and chain extension pre-reaction: Flaxseed oil: 20-40 parts; Epoxidized vegetable oil: 50-70 parts; Cashew phenols: 8-12 parts; The amount of triethanolamine (TEOA) added is 1.49%-3.73% of the total weight of the flaxseed oil, epoxidized vegetable oil, and cashew nut shell extract. After the pre-reaction modified oil phase intermediate has cooled, add 0.1-1.0 parts of vulcanization accelerator and mix evenly to obtain the pre-reaction modified oil phase; The vulcanization accelerator is zinc dibenzyl dithiocarbamate (ZBEC).

[0010] The reasons for limiting the ratio of carrier to oil phase are as follows: If the content of precipitated silica is less than 30wt%, the carrier has limited pore volume and cannot completely adsorb the oil phase, which may result in the product being sticky and the powder flowability being reduced; if it is more than 40wt%, when achieving the same plasticizing effect, more rigid carrier will be introduced into the rubber system, which may affect the flexibility of the rubber compound.

[0011] Carrier loading: Under high-speed shearing and atomized spraying conditions, the pre-reacted modified oil phase enters the mesopores and macropores of precipitated silica by capillary force, forming a load with van der Waals force and capillary force as the main forces.

[0012] The content of the precipitated silica is 35 wt%, and the content of the pre-reactive modified oil phase is 65 wt%. The raw materials for preparing the pre-reaction modified oil phase, by weight, are: 30 parts linseed oil, 60 parts epoxidized vegetable oil, 10 parts cashew phenol, 0.5 parts vulcanization accelerator, and the amount of triethanolamine added is 1.5% of the total weight of linseed oil, epoxidized vegetable oil and cashew phenol.

[0013] Preferably, the flaxseed oil has an iodine value ≥170gI2 / 100g; the epoxidized vegetable oil is epoxidized soybean oil with an epoxidation value ≥6.0%.

[0014] Preferably, the nitrogen adsorption specific surface area of ​​the precipitated silica is 155-190 m². 2 / g, CTAB specific surface area is 150-180m² 2 / g, DOP oil absorption value is 250-310mL / 100g.

[0015] A second objective of this invention is to provide a method for preparing the aforementioned solid plasticizer.

[0016] The preparation method includes the following steps: S1. Pre-treatment of precipitated silica: Precipitated silica is heated and dehydrated under vacuum conditions, with the temperature controlled at 115℃-125℃ and the vacuum degree ≤-0.09MPa, until the moisture content of the carrier is ≤0.5%, thus obtaining the pretreated carrier. S2. Oil phase pre-reaction: Linseed oil, epoxidized vegetable oil and cashew phenol are added to the reaction vessel according to the formula. Triethanolamine is added at a total weight of 1.49%-3.73% of the three components. The mixture is stirred at a constant temperature of 130℃-140℃ for 1.5-2.0 hours to allow the phenolic hydroxyl groups of cashew phenol to undergo a ring-opening etherification reaction with the internal epoxy groups of the epoxidized vegetable oil, thus obtaining a pre-reaction modified oil phase intermediate. After the reaction is completed, the triethanolamine is not separated and the mixture is allowed to cool naturally to 80℃-85℃. S3. Vulcanization Accelerator Compounding and Physical Adsorption Powdering: A vulcanization accelerator is added to the pre-reactive modified oil phase intermediate obtained in step S2. The mixture is continuously stirred at 80℃-85℃ (200-400 rpm) for 20-30 minutes to ensure uniform dispersion, forming a stable microemulsion or submicron-level suspension dispersion oil phase system, thus obtaining the pre-reactive modified oil. The pretreated carrier obtained in step S1 is then fed into a high-shear mixer for fluidized stirring. The pre-reactive modified oil is sprayed into the mixer through an atomizing device with a heat-insulating jacket (atomizing pressure 0.5 MPa). The oil phase temperature is maintained at 80℃-85℃ to ensure a suitable atomization viscosity. After spraying, high-shear stirring continues for 15 minutes to allow the oil phase to fully enter the carrier mesopores. After cooling and sieving, the bio-based rubber solid softener is obtained.

[0017] Pre-reaction modified oil phase intermediate: refers to the product after step S2 reaction is completed but before ZBEC is added (i.e., the product after flaxseed oil, epoxidized soybean oil, and cashew phenol react under TEOA catalysis).

[0018] Pre-reaction modified oil phase: refers to the final oil phase after adding ZBEC in step S3 (i.e., the mixture of pre-reaction modified oil phase intermediate and ZBEC).

[0019] Pre-reactive modified oil: refers to the final oil phase system used to load precipitated silica.

[0020] A third objective of this invention is to provide a method for applying the above-mentioned solid softener in rubber products.

[0021] The solid softener is added as a compounding agent in the rubber mixing process; when adding the solid softener to the rubber base formulation, the equivalent deduction rule is applied: based on the mass of precipitated silica contained in the added solid softener, the corresponding amount of inorganic filler is deducted equally from the rubber base formulation.

[0022] Adding solid plasticizers directly to the formulation increases the total filler volume fraction of the rubber compound, leading to an abnormal increase in Mooney viscosity and causing processing difficulties. Applying the equivalent subtraction rule maintains a constant total amount of rigid filler in the formulation, ensuring stable rheological and processing properties of the rubber compound.

[0023] This application method employs the filler equivalent mass deduction rule: when the solid softener is introduced into the original rubber formulation to replace the liquid softening oil, the total weight of the required solid softener is calculated and added according to the effective content of the pre-reacted modified oil phase in the solid softener; simultaneously, the actual weight parts of the base silica to be deducted in the original formulation's feed table are calculated using the following formula: (1) Amount of solid plasticizer added: W1 = W0 / C; (2) Deduction for foundation packing: W3 = W2 - W1 × (1 - C); (3) Synchronous adjustment amount of silane coupling agent: W4 = W3 × R (where R is the mass ratio of silane coupling agent to silica in the original formula).

[0024] The parameters in the formula are defined as follows: W0—Amount of liquid softening oil in the original formula, unit: parts by weight; C—Mass fraction of the pre-reacted modified oil phase in the solid softener; W1—Amount of solid plasticizer added, unit: parts by weight; W2—Amount of silica in the original formula, unit: parts by weight; W3 — Adjusted amount of silica, unit: parts by weight; W4 — Adjusted dosage of silane coupling agent, unit: parts by weight; R – The mass ratio of silane coupling agent to silica in the original formula.

[0025] In this invention, after a triethanolamine-catalyzed reaction, the epoxy groups of epoxidized soybean oil undergo ring-opening addition with the phenolic hydroxyl groups of cashew phenol to form a modified oil phase containing a β-hydroxy ether structure. Compared to unreacted small-molecule liquid oil, this modified oil phase is presumably characterized by an increased molecular chain length, making it easier to form physical entanglements in the subsequent rubber crosslinking network, which is beneficial for improving the fixation efficiency of the oil phase in the vulcanized rubber network.

[0026] In the application system of this invention, the pre-reacted oil phase has macromolecular structural characteristics, and the carrier compound has a specific spatial distribution. It is speculated that it can exert its effects synergistically in three ways during the mixing and vulcanization stages: improving the surface affinity of the filler, increasing the physical entanglement size of the modified oil phase, and efficiently promoting the crosslinking density.

[0027] Processing safety performance verification: Experiments show that under mixing conditions of 140-150℃, the rubber compound using the solid softener of this invention still has sufficient scorch safety and can meet the processing requirements of continuous industrial mixing. The triethanolamine remaining in the oil phase preferentially adsorbs onto the surface of silica in the early stages of mixing, delaying its synergistic activation effect on vulcanization promotion; simultaneously, ZBEC is loaded within the pores of silica and is physically isolated in the early stages of mixing. The synergistic effect of these two factors ensures sufficient safety of the rubber compound at the mixing temperature.

[0028] Verification of Oil Phase Fixation Effect and Synergistic Mechanism: The acetone extract content of vulcanized rubber directly reflects the degree of fixation of small organic molecules in the crosslinking network. The decrease in extract content is not due to a single factor, but rather the result of the combined effect of three synergistic mechanisms: ① The increased molecular weight of the chain-extended oil phase generated in the pre-reaction increases the probability of physical entanglement with the rubber matrix; ② Residual TEOA optimizes the surface polarity of silica, reducing the loss of small molecules such as accelerators by fillers; ③ ZBEC significantly increases the crosslinking density of rubber during the vulcanization stage, and the high crosslinking density efficiently locks the oil phase molecules in the three-dimensional network. The combined effect of these three factors reduces the risk of small molecule migration and precipitation during long-term use of the product.

[0029] In Application Example 1, the scorch time was longer than in Application Comparative Example 1. The extended scorch time may be related to the competitive adsorption of TEOA on the filler surface and the pore isolation of ZBEC.

[0030] Compared with the prior art, the beneficial effects of the present invention are: (1) A macromolecular modified oil structure was constructed by pre-reaction of cashew phenol with epoxidized vegetable oil, which is beneficial to the fixation of the oil phase in the rubber crosslinking network during subsequent vulcanization. When applied to tire tread rubber, the hysteresis loss of the rubber compound is reduced, and the acetone extract content is reduced, which helps to reduce the risk of small molecule migration and precipitation during long-term use of the product.

[0031] (2) The preparation stage of this invention uses an adsorption process, and the resulting product is a powder with good flowability, which is convenient for automated weighing and feeding. In downstream applications, the Mooney viscosity of the rubber compound can be maintained relatively stably by using the equivalent subtraction method. This invention mainly uses bio-based raw materials (vegetable oils, cashew nut oil, etc.), which can replace petroleum-based aromatic oils, and cashew nut oil is an extract of agricultural and forestry by-products. Detailed Implementation

[0032] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the principles, raw materials, testing standards, and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0033] I. To achieve the technical objective of this invention, the following physicochemical mechanisms are followed in material selection, formulation design, and process route. Those skilled in the art can reproduce and implement this invention based on these mechanisms: 1. Group distribution ratio This invention limits the content of precipitated silica to 30wt%-40wt% and the content of pre-reacted modified oil phase to 60wt%-70wt%. This range is determined based on the pore volume of precipitated silica. When the oil phase content exceeds 70wt%, it may exceed the capillary adsorption capacity of the carrier, leading to powder surface wetting, agglomeration, and reduced flowability. When the carrier content exceeds 40wt%, to achieve the same plasticizing effect, a large amount of rigid carrier will be introduced into the rubber formulation, which may affect the processing performance of the rubber compound.

[0034] Precipitated silica is selected in this invention, with a BET specific surface area of ​​155-190 m². 2 / g, CTAB specific surface area is 150-180m² 2 / g, DOP oil absorption value is 250-310mL / 100g. DOP oil absorption value is an important indicator for characterizing the structure of silica. When the DOP oil absorption value (DBP absorption value) is too low, the carrier pore volume is insufficient, making it difficult to accommodate the pre-reacted modified oil phase, which may lead to oil phase overflow and powder agglomeration during adsorption. When the DOP oil absorption value is too high, the carrier structure is too loose, the particle mechanical strength decreases, and it may be excessively broken under high shear conditions of mixing, affecting the accuracy of equivalent subtraction.

[0035] After the reaction is complete, some TEOA is consumed, while the remaining free TEOA remains in the oil phase without separation. During application, the remaining free TEOA can form hydrogen bonds with the silanol groups on the surface of silica, which helps improve the affinity between the oil phase and the filler interface, thus aiding in the dispersion of the filler in the rubber matrix.

[0036] During the vulcanization stage, the unsaturated double bonds retained in the pre-reacted modified oil (derived from the side chains of linseed oil and cashew nut shell) can participate in the cross-linking reaction in the vulcanization system, fixing some of the macromolecular modified oil into the rubber cross-linking network. ZBEC (zinc dibenzyl dithiocarbamate), as an ultra-fast vulcanization accelerator that does not produce nitrosamines, forms active complexes with zinc oxide, stearic acid, and sulfur during the vulcanization stage, promoting the participation of unsaturated segments in the oil phase in the cross-linking reaction. Residual TEOA, as an alkaline substance, has an activating effect on ZBEC; however, it should be noted that the amount of TEOA added should not exceed 2.5% of the total weight of the oil phase, otherwise excessive TEOA free in the rubber matrix may accelerate the vulcanization reaction and affect processing safety.

[0037] For the formulation obtained after adjusting for the equivalent subtraction rule, the following conventional three-stage mixing process can be used for industrial preparation: First stage mixing (master mixing): Raw rubber (solution-polymerized styrene-butadiene rubber and cis-butadiene rubber) is added to an internal mixer and plasticized for 30-60 seconds. Then, the solid softener described in this invention, 2 / 3 of the adjusted silica, 2 / 3 of the silane coupling agent, zinc oxide, stearic acid, and antioxidant are added. The rotor speed is controlled at 50 rpm, the mixing time is 4 minutes, and the discharge temperature is controlled at 145-150℃ to ensure that TEOA fully activates the filler surface and promotes the silanization reaction of Si69.

[0038] Second stage mixing (supplementary mixing): After the first stage masterbatch has cooled and rested, it is put into an internal mixer, and the remaining 1 / 3 of the adjusted silica and silane coupling agent are added. The rotor speed is controlled at 45 rpm, the mixing time is 3 minutes, and the discharge temperature is controlled at 140-145℃.

[0039] The third stage of mixing (final mixing): After the second stage of mixing has cooled and been left to stand, it is put into an internal mixer, and sulfur and accelerators (CBS, DPG) are added. The rotor speed is controlled at 25 rpm, the mixing time is 3 minutes, and the discharge temperature is controlled at 90-105℃ to prevent the accelerator ZBEC from being prematurely activated and causing scorching.

[0040] II. Explanation of Raw Material Sources The main raw materials used in the specific embodiments and comparative examples of this invention can all be obtained through commercial means, and their specific specifications and sources are shown in Table 1.

[0041] Table 1: Specifications and sources of main raw materials used in the examples and comparative examples

[0042] Note: The active ingredient of cashew phenol in this invention is 3-pentadecanylphenol (content ≥90%), and the remainder is cashew diol and other impurities containing bisphenol hydroxyl groups. Since the reactivity of cashew diol differs from that of monophenols, the actual feed amount must be calculated based on the gas chromatography purity of each batch of raw materials, using the following formula, to ensure that the total molar number of phenolic hydroxyl groups participating in the pre-reaction is consistent with the baseline of the example (based on 90% purity): Equivalent feed amount (g) = Theoretical baseline feed amount (g) × (90% ÷ Measured mass fraction of 3-pentadecanylphenol).

[0043] The actual purity of all batches used in the embodiments of this invention is 91.2%-92.5%, and all batches have been corrected according to this formula before feeding.

[0044] III. Performance Testing Methods and Standards In the embodiments and comparative examples of this invention, the relevant performance indicators were tested according to the following national / international standards or industry-standard methods: Mooney viscosity: According to GB / T1232.1-2016, a Mooney viscometer was used for testing. A large rotor (L-type) was adopted, the test temperature was 100℃, the sample preheating time was 1 minute, and the Mooney viscosity value ML(1+4)@100℃ was read after the rotor rotated for 4 minutes.

[0045] Scorch time (T10): According to GB / T 9869.3-2025, the time (minutes) required for a 10% increase in torque was recorded using a rotorless vulcanizer at 160℃.

[0046] Payne effect testing: A rubber processing analyzer (RPA2000, model RPA2000P, Alpha Technologies, USA) was used with a sealed cavity mold. Before testing, the rubber compound was kept at 100℃ for 5 minutes to eliminate thermal history, and then strain scanning was performed. Scanning conditions: temperature 100℃, frequency 1Hz, strain range 0.28%-40% (logarithmic scan, 12 data points every ten times the frequency), and the storage modulus G′ was recorded. The Payne effect is expressed as the difference in storage modulus (ΔG′) between low strain (0.28%) and high strain (40%), in MPa. Each sample was tested three times and the average value was taken.

[0047] Tear strength: According to GB / T529-2008, the tear strength is tested using a right-angled specimen, and the unit is kN / m.

[0048] Dynamic mechanical properties (DMA, tanδ): Tested using a dynamic thermomechanical analyzer (DMA, model TAInstrumentsQ800 or equivalent), according to ISO 4664-1:2022 "Determination of dynamic properties of vulcanized or thermoplastic rubber". The specimen was a rectangular strip of vulcanized rubber, measuring 30mm × 6mm × 2mm (length × width × thickness). The test mode was tensile, using a film / fiber clamp with a preload force of 0.01N, automatically adjusting the static force to maintain a constant dynamic force. Test conditions: frequency 10Hz, dynamic strain 1%, heating rate 2℃ / min, temperature range -80℃ to 100℃. The loss factor (tanδ, characterizing wet grip) at 0℃ and the loss factor (tanδ, characterizing rolling resistance) at 60℃ were recorded. Three parallel specimens were tested for each sample, and the arithmetic mean was taken.

[0049] Acetone extract content: According to GB / T3516-2024, the vulcanized rubber sample was cut into pieces, and extracted with acetone in a Soxhlet extractor for 24 hours by reflux. After drying, the mass loss was measured and the mass percentage of the extract was calculated.

[0050] Crosslinking density test: Determined according to the Flory-Rehner equilibrium swelling method. The vulcanized rubber sample (approximately 0.5 g) was placed in toluene and swollen at 25°C in the dark for 72 hours until the equilibrium mass was constant. After removal, the surface solvent was quickly blotted dry with filter paper, and the swollen mass was weighed. Then, it was dried in a vacuum drying oven at 60°C until constant weight, and the dry rubber mass was weighed. The crosslinking density V was calculated according to the Flory-Rehner equation. e (Unit: mol / cm) 3 The rubber-toluene interaction parameter χ was set to 0.45. Three parallel samples were taken for each sample, and the test results were taken as the arithmetic mean.

[0051] Hot air aging performance: According to GB / T3512-2014, the vulcanized rubber test pieces were placed in a 100℃ hot air aging chamber for 72 hours, the tear strength after aging was tested, and the retention rate with that before aging was calculated.

[0052] Oil leakage rate test for powder products: Accurately weigh 10.0g of solid softener powder (accurate to 0.01g), and evenly spread it on three layers of medium-speed quantitative filter paper (compliant with GB / T 1914-2017 standard, specifications: diameter 110mm, basis weight 80±4g / m). 2 The filter paper (with a pore size of 15-20 μm and a static adsorption capacity of ≥1.5 times its own weight for liquid paraffin) was placed in the central region of a constant-temperature drying oven at 60℃±1℃ for 72 hours. After removal, the mass of oil phase adsorbed by the filter paper (filter paper weight gain) was weighed, and the percentage of oil phase leakage was calculated. Pre-verification showed that the total adsorption capacity of the three-layer filter paper was approximately three times that of a single layer (i.e., ≥4.5 g of oil phase), far exceeding the maximum amount of oil phase that could actually leak from the sample (leakage in all comparative examples was <500 mg), ensuring that the adsorption process was not limited by filter paper saturation. The calculation formula was: Oil leakage rate (%) = (filter paper weight gain / initial sample mass) × 100%. Each sample underwent three parallel tests, and the arithmetic mean was taken.

[0053] In the following examples and comparative examples, for accurate weighing, the "parts" of each component in the active compound oil phase are calculated in "grams (g)". Pretreatment and physical compounding were carried out in a high-speed mixer equipped with heating and vacuum devices.

[0054] 1. Preparation Examples 1-8 This set of examples demonstrates the preparation of solid plasticizers with different formulations. Specific formulations are shown in Table 2.

[0055] Uniform preparation conditions and procedures: S1. Carrier dehydration pretreatment: Add the required mass of precipitated silica to a high-speed mixer and turn on the heating and vacuum system. Raise the material temperature to 120℃, maintain a vacuum of ≤-0.09MPa, and continuously stir at a constant temperature for 45 minutes until the carrier moisture content is ≤0.5%. Cool down for later use.

[0056] S2. Oil Phase Pre-reaction (Ring-opening Addition): In a reactor equipped with heating, stirring, and nitrogen protection devices, linseed oil, epoxidized soybean oil, and cashew nut shell powder are added sequentially according to the proportions in Table 2. Then, triethanolamine is added at 1.5% of the total weight of the three components. Stirring is started (300 rpm), and nitrogen is introduced three times to purge the air from the reactor. The temperature is raised to 135°C and stirred at a constant temperature. Samples are taken every 20 minutes during the reaction. Following the hydrochloric acid-acetone method in GB / T 1677-2023 "Determination of Epoxy Value of Plasticizers," the reaction time is controlled to 2.0 hours. Measurements show that within this time range, the epoxy group conversion rate typically reaches 60%-65%, indicating that the pre-reaction has been fully carried out. Before the reaction, the residual oxygen content in the reactor must be ensured to be ≤0.5% (monitored by an oxygen analyzer) to reduce the risk of thermal oxidation of the linseed oil. After the reaction is complete, take a sample to determine the iodine value (refer to GB / T 5532-2022). The decrease in iodine value should not exceed 5% of the initial value; otherwise, it indicates a significant oxidation side reaction, and the sealing of the nitrogen protection system needs to be checked. After confirming that it is qualified, allow the material to cool naturally to 83℃.

[0057] S3. Vulcanization Accelerator Compounding and Adsorption Powdering: ZBEC is added to the cooled pre-reactive modified oil phase intermediate. The system is then placed in a basket mill for 20 minutes of circulating grinding (controlling the grinding fineness D90 ≤ 10μm) to ensure uniform dispersion and form a stable suspended dispersion oil phase system, thus obtaining the pre-reactive modified oil. The dehydrated silica is placed in a mixer and fluidized (800 rpm). The pre-reactive modified oil is then uniformly sprayed into the mixer through a high-pressure atomizing nozzle. After spraying, high-shear stirring is continued for 15 minutes. After discharge, the material is naturally cooled to room temperature to obtain the target powder product.

[0058] Example 1 Weigh the following components according to the proportions in Example 1 in Table 2: 350.0g of precipitated silica; 650g of pre-reacted modified oil phase, including 194.4g of linseed oil, 388.8g of epoxidized soybean oil, 63.6g of cashew phenol (equivalent to 64.7g of theoretical effective amount based on the measured purity of 91.5% in this batch), 3.2g of ZBEC, and 9.7g of TEOA.

[0059] The preparation was carried out according to steps S1-S3, yielding approximately 1000g of the target product.

[0060] Example 2 Weigh the following components according to the proportions in Example 2 in Table 2: 300.0g of precipitated silica; 700g of pre-reacted modified oil phase, including 208.7g of linseed oil, 417.4g of epoxidized soybean oil, 68.3g of cashew phenol (equivalent to 69.4g of theoretical effective amount based on the measured purity of 91.5% in this batch), 5.6g of ZBEC, and 10.4g of TEOA.

[0061] Prepare according to steps S1-S3.

[0062] Example 3 Weigh the following components according to the proportions in Example 3 in Table 2: 400.0g of precipitated silica; 600g of pre-reacted modified oil phase, including 179.8g of linseed oil, 359.6g of epoxidized soybean oil, 58.8g of cashew phenol (equivalent to 59.8g of theoretical effective amount based on the measured purity of 91.5% in this batch), 1.8g of ZBEC, and 9.0g of TEOA.

[0063] Prepare according to steps S1-S3.

[0064] Example 4 Weigh the following components according to the proportions in Example 4 of Table 2: 350.0g of precipitated silica; 650g of pre-reacted modified oil phase, including 226.5g of linseed oil, 356.0g of epoxidized soybean oil, 63.6g of cashew phenol (equivalent to 64.6g of theoretical effective amount based on the measured purity of 91.5% in this batch), 3.9g of ZBEC, and 9.7g of TEOA.

[0065] Prepare according to steps S1-S3.

[0066] Example 5 Weigh the components according to the proportions in Example 5 in Table 2: 350.0g of precipitated silica; 650g of pre-reacted modified oil phase, including 162.2g of linseed oil, 421.6g of epoxidized soybean oil, 63.7g of cashew phenol (equivalent to 64.7g of theoretical effective amount based on the measured purity of 91.5% in this batch), 2.6g of ZBEC, and 9.7g of TEOA.

[0067] Prepare according to steps S1-S3.

[0068] Example 6 Weigh the following components according to the specified proportions: 350.0 g of precipitated silica; 650 g of pre-reacted modified oil phase, including 129.6 g of linseed oil, 453.6 g of epoxidized soybean oil, 63.6 g of cashew nut shell extract (equivalent to 64.7 g of theoretical effective amount based on the measured purity of 91.5% in this batch), 3.2 g of ZBEC, and 9.7 g of TEOA. The preparation steps are the same as in Example 1. The resulting product had an oil leakage rate of 0.32% at 60℃ for 72 h, and an oil phase viscosity of 182 mPa·s at 80℃.

[0069] Example 7 Weigh the following components according to the specified proportions: 350.0 g of precipitated silica; 650 g of pre-reacted modified oil phase, including 259.2 g of linseed oil, 324.0 g of epoxidized soybean oil, 63.6 g of cashew nut shell extract (equivalent to 64.7 g of theoretical effective amount based on the measured purity of 91.5% in this batch), 3.2 g of ZBEC, and 9.7 g of TEOA. The preparation steps are the same as in Example 1. The resulting product had an oil leakage rate of 0.26% at 60℃ for 72 h, and an oil phase viscosity of 308 mPa·s at 80℃.

[0070] Example 8 The overall formulation is the same as in Example 1. The difference is that in step S2, the amount of TEOA added is changed to 2.5% of the total weight of the base oil (i.e., the total weight of linseed oil, epoxidized soybean oil, and cashew phenol), i.e., TEOA: 16.2g. The weighing values ​​of the other components are the same as in Example 1. The remaining steps are the same as in Example 1. The resulting product has a dry appearance and good flowability.

[0071] Table 2: Composition ratios of preparation examples 1-8

[0072] Note: The components of the oil phase in Table 2 are expressed in "parts by weight" (relative proportions). In actual preparation, the proportions can be scaled up according to the target yield. The amount of TEOA added is calculated as a percentage of the total mass of linseed oil, epoxidized soybean oil, and cashew phenol. ZBEC is added in step S3 after the pre-reaction is completed and is not included in the TEOA stoichiometric standard.

[0073] Comparative Example 1 The formulation is the same as in Example 1. The difference is that in step S2, the reaction temperature is reduced from 135°C to 80°C, and the mixture is stirred at a constant temperature for 1.8 hours, while the other conditions remain unchanged.

[0074] Comparative Example 2 The formulation was changed to: 25 wt% precipitated silica and 75 wt% pre-reacted modified oil phase (the internal component ratio of the oil phase and the pre-reaction conditions are the same as in Example 1). The preparation steps are the same as in Example 1.

[0075] Comparative Example 3 The overall formulation is the same as in Example 1. In step S2, no TEOA catalyst is added; only flaxseed oil, epoxidized soybean oil, and cashew phenol are stirred at a constant temperature of 135°C for 1.8 hours. The remaining steps are the same as in Example 1.

[0076] Comparative Example 4 The overall formulation and pre-reaction conditions were the same as in Example 1. The difference was that after the reaction in step S2 was completed, the pre-reaction product was cooled to 60°C, an equal volume of deionized water was added, and after stirring for 30 minutes, it was allowed to stand and separate into layers. The aqueous phase was then separated. After washing twice with water, the pH of the oil phase was adjusted to 6.5-7.0 with dilute hydrochloric acid (1 mol / L), and then washed with deionized water until neutral. After separation, the oil phase was dehydrated at 80°C / vacuum degree ≤ -0.09 MPa until the carrier moisture content was ≤ 0.05%. The residual TEOA content in the treated oil phase was < 0.01% by gas chromatography. A pre-reaction modified oil phase with free triethanolamine removed was obtained, which was then subjected to the compounding and adsorption in step S3. The remaining steps were the same as in Example 1.

[0077] Comparative Example 5 The overall formulation is the same as in Example 1. In step S2, the amount of TEOA added is increased from 1.5% to 5.0% (as a percentage of the total weight of the oil phase). The remaining steps are the same as in Example 1.

[0078] Comparative Example 6 The formulation is the same as in Example 1. In step S1, the precipitated silica is not subjected to heating and vacuum dehydration treatment. Instead, commercially available silica in the same state as in Example 1, but without dehydration (its initial moisture content was determined to be approximately 6.2% by oven weight loss method at 105℃×2h), is used directly at room temperature for subsequent atomization adsorption. The remaining steps are the same as in Example 1.

[0079] Comparative Example 7 The overall formulation and pre-reaction conditions are the same as in Example 1. The difference is that ZBEC is not added in step S3; instead, the pre-reacted modified oil phase intermediate is directly atomized and sprayed for adsorption. The remaining steps are the same as in Example 1.

[0080] Comparative Example 8 The formulation and pre-reaction conditions were the same as in Example 1. Samples were taken before the reaction, during the reaction (every 20 minutes), and at the reaction endpoint. The epoxy value at each time point was determined according to the hydrochloric acid-acetone method of GB / T1677-2023 to investigate the transformation of epoxy groups during the pre-reaction process.

[0081] Comparative Examples 9a-9c: Pre-reaction temperature gradient experiments; The formulation was the same as in Example 1. The difference was that in step S2, the reaction temperature was set to 100℃ (Comparative Example 9a), 110℃ (Comparative Example 9b), and 120℃ (Comparative Example 9c), and the reaction time was 1.8 hours for each. The other conditions were the same as in Example 1. The epoxy group conversion rate at the reaction endpoint was measured at each temperature, and the results are shown in Table 6.

[0082] Comparative Example 10: The formulation is the same as in Example 1. The difference is that in step S2, no heated catalytic pre-reaction is performed. Instead, linseed oil, epoxidized soybean oil, cashew phenol, and TEOA are stirred and mixed at room temperature (25°C) for 30 minutes to form a physical mixture. Then, ZBEC is directly added and loaded onto silica in step S3. The remaining steps are the same as in Example 1. The resulting product has a uniform and dry appearance, and the oil leakage rate at 60°C / 72h is 1.3%.

[0083] The products obtained in Examples 1-5 and Comparative Examples 1-8 were observed for their appearance and tested for oil leakage rate at 60℃ / 72h. The results are shown in Table 3.

[0084] The pre-reaction conversion rates and corresponding application properties of the rubber compounds in Examples 1, 8 and Comparative Example 5 are shown in Table 7.

[0085] Table 3: Physical state test results of products from Examples 1-5 and Comparative Examples 1-8

[0086] Table 3 shows that all examples 1-5 yielded solid softener powders in good condition, with oil leakage rates ranging from 0.08% to 0.75%. Comparative Example 2 had an oil leakage rate of 4.85%, exceeding the adsorption capacity of the carrier; Comparative Example 6 had an oil leakage rate of 3.80%, indicating that when the carrier was not dehydrated, its pores were occupied by water, and strong hydrogen bonds formed between the surface silanol groups and water, reducing the capillary adsorption capacity and affinity for the oil phase, leading to an increased oil leakage rate. The remaining comparative examples showed powders with good appearance and extremely low oil leakage rates, indicating that the pre-reaction temperature, presence or absence of catalyst, catalyst residue, and addition of sulfidation accelerator have little effect on the physical state of the powder and its oil storage stability. Only the carrier ratio and the carrier pretreatment dehydration process are the core factors determining the powder's appearance and oil leakage performance.

[0087] To verify that the pre-reacted modified oil phase does indeed enter the mesoporous channels of the silica support rather than just adsorbed on the outer surface, nitrogen adsorption-desorption tests (BET method) were performed on the support raw material (pretreated silica) and the resulting powder product of Example 1. The results are shown in Table 4.

[0088] Table 4: Changes in pore structure parameters of silica carrier before and after loading

[0089] The above data show that after loading, the specific surface area and pore volume of the carrier decreased by approximately 70%, while the average pore size only slightly decreased from 38.5 nm to 36.2 nm. This indicates that the oil phase did not merely adhere to the outer surface or block the pore openings, but rather uniformly filled the interior of the mesoporous channels.

[0090] The results of epoxy value and TEOA consumption during the pre-reaction process of Comparative Example 8 are shown in Table 5.

[0091] Table 5: Results of epoxy value and TEOA consumption during the pre-reaction process of Comparative Example 8

[0092] Note: Apparent epoxy value (%) = epoxy molar concentration (mol / 100g) × 16 (oxygen atomic weight) × 100%. Epoxy group conversion rate = (initial epoxy molar concentration - current epoxy molar concentration) / initial epoxy molar concentration × 100%. The above data shows that the reaction reaches a conversion rate of approximately 63.4% after 120 minutes, and the reaction system still maintains a low viscosity, which is beneficial for the implementation of subsequent atomized spray coating loading processes.

[0093] To further quantitatively characterize the consumption of TEOA during the pre-reaction process, gas chromatography (GC) was used to determine the residual amount of free TEOA in the oil phase at different reaction times.

[0094] Sample pretreatment steps: Accurately weigh 2.0 g of the pre-reaction oil phase (accurate to 0.001 g) and place it in a 50 mL stoppered centrifuge tube. Add 20 mL of anhydrous methanol (chromatographic grade), tighten the stopper, and place the tube in an ultrasonic cleaner. Extract using ultrasound at room temperature (25℃±2℃) for 30 min (ultrasonic power 200 W, frequency 40 kHz). After extraction, place the centrifuge tube in a benchtop high-speed centrifuge and centrifuge at 8000 rpm for 10 min to precipitate the high molecular weight components in the oil phase to the bottom of the tube. Take approximately 2 mL of the supernatant, filter it through a 0.22 μm PTFE syringe filter, and transfer it to a 2 mL GC vial. Seal and prepare for analysis.

[0095] Chromatographic conditions: Agilent DB-5 capillary column (30m × 0.32mm × 0.25μm), FID detector, high-purity nitrogen (purity ≥99.999%) as carrier gas, column flow rate 1.2mL / min, split ratio 20:1, injection volume 1μL. Injector temperature 250℃, detector temperature 280℃. Column oven temperature program: initial 80℃, hold for 2 min, increase to 280℃ at 10℃ / min, hold for 5 min. Quantification was performed using the internal standard method (with n-hexadecane as the internal standard). Standard curve concentration range: 0.5-10.0mg / mL, linear correlation coefficient R0. 2 >0.999.

[0096] Table 6: Epoxy group conversion rate at different pre-reaction temperatures

[0097] As shown in Table 6, within the temperature range of 80-135℃, the conversion rate increases with increasing temperature. When the temperature is below 130℃, the conversion rate cannot consistently reach the process threshold of 60%, and the amount of residual free small molecule oil phase in the product increases, resulting in higher acetone extract content and insufficient packing dispersion in subsequent application examples.

[0098] Table 7: Pre-reaction conversion rates and corresponding application properties of rubber compounds in Examples 1, 8 and Comparative Example 5

[0099] The data above show that when the TEOA addition is within the range of 1.0%-2.5%, the epoxy group conversion rate increases with the increase of TEOA dosage, the Mooney viscosity of the rubber compound remains at a low level, the Payne effect is below 1.60 MPa, and the scorch time is greater than 14 minutes, meeting the safety requirements for industrial processing. When the TEOA addition increases to 5.0%, the scorch time drops sharply to 10.2 minutes, and the processing safety deteriorates significantly. Therefore, the TEOA range of 1.0%-2.5% is a reasonable range that balances pre-reaction efficiency and processing safety.

[0100] To verify the performance of the solid softener of this invention in rubber formulations, the following basic formulation of green tire tread compound was established (unit: parts by weight / phr): Solution-polymerized styrene-butadiene rubber (SSBR) 80 parts; cis-butadiene rubber (BR) 20 parts; precipitated silica 80 parts (basic setting amount); silane coupling agent (Si69) 6.4 parts; zinc oxide (ZnO) 3.0 parts; stearic acid (SA) 1.5 parts; antioxidant (4020) 1.5 parts; softener 15 parts (basic setting effective oil content); sulfur 1.5 parts; accelerator (CBS) 1.5 parts; accelerator (DPG) 2.0 parts.

[0101] The mixing process adopts a conventional three-stage mixing process. The discharge temperature of the first stage mixing is controlled at 145℃, and the vulcanization conditions are 160℃×T90.

[0102] Application Example 1: The powder product of Example 1 was used. Approximately 23.08 parts of this powder (15 / 65%) were added (including 8.08 parts of carrier and 15 parts of pre-reacted modified oil). Following the equivalent deduction rule: the silica was reduced from 80 parts to 71.92 parts; Si69 was adjusted from 6.4 parts to 5.75 parts.

[0103] Application Example 2: The powder product from Example 2 (containing 70% oil) was used. 21.43 parts of powder were added (including 6.43 parts of carrier). The amount of silica was reduced to 73.57 parts, and Si69 was adjusted to 5.89 parts.

[0104] Application Example 3: The powder product of Example 3 (containing 60% oil) was used. 25 parts of powder (including 10 parts of carrier) were added. The amount of silica was reduced to 70 parts, and the amount of Si69 was adjusted to 5.60 parts.

[0105] Application Example 4: The powder product of Example 4 was used. 23.08 parts of powder were added, silica was reduced to 71.92 parts, and Si69 was adjusted to 5.75 parts.

[0106] Application Example 5: The powder product of Example 5 was used. 23.08 parts of powder were added, silica was reduced to 71.92 parts, and Si69 was adjusted to 5.75 parts.

[0107] Application Example 6: The powder product of Example 6 was used. Equivalent deduction was performed using the same method as in Application Example 1. The properties of the compound are shown in Table 11.

[0108] Application Example 7: The powder product of Example 7 was used. Equivalent deductions were performed using the same method as in Application Example 1. The properties of the compound are shown in Table 11.

[0109] Application Comparative Example 1: Without using the product of this invention. Directly add 15 parts of environmentally friendly aromatic oil (TDAE) and maintain 80 parts of silica.

[0110] Comparative Example 2: 23.08 parts of the powder from Comparative Example 1 (pre-reaction temperature 80℃) were used, and the equivalent subtraction rule was applied.

[0111] Application of Comparative Example 3: 23.08 parts of powder (TEOA-free) from Comparative Example 3 were used, and the equivalent deduction rule was applied.

[0112] Application of Comparative Example 4: 23.08 parts of powder (TEOA separation and removal) from Comparative Example 4 were used, and the equivalent deduction rule was applied.

[0113] Application of Comparative Example 5: 23.08 parts of the powder (TEOA 5.0%) of Comparative Example 5 were used, and the equivalent deduction rule was applied.

[0114] Application Comparative Example 6: No powder preparation. During the first mixing stage, 15 parts of liquid pre-reaction modified oil phase (oil phase composition and pre-reaction conditions are the same as in Example 1, containing 1.5% TEOA), 80 parts of silica, and 6.4 parts of Si69 were added in portions to the internal mixer (80°C), and other additives were added in the same manner as in Application Example 1.

[0115] Comparative Example 7: 23.08 parts of powder (excluding ZBEC) from Comparative Example 7 were used, and the equivalent deduction rule was applied.

[0116] Comparative Example 8: 23.08 parts of the powder from Example 1 were used, and the partial equivalent subtraction rule was applied (only 50% of the carrier was subtracted, i.e., 4.04 parts were subtracted, the silica was reduced to 75.96 parts, and the Si69 was reduced to 6.08 parts).

[0117] Comparative Examples 9a-9c: 23.08 parts of the powder from Example 1 were used. The equivalent subtraction rule was applied, and the first-stage mixing and debinding temperatures were set to 120℃ (Comparative Example 9a), 130℃ (Comparative Example 9b), and 140℃ (Comparative Example 9c), respectively. The remaining mixing processes were the same as in Application Example 1. The Payne effect was tested, and the results are shown in Table 9.

[0118] Comparative Examples 10a-10c: 23.08 parts of the powder from Example 1 were used. Carrier subtraction was performed according to the following gradients: Application Comparative Example 10a: 100% carrier (silica down to 71.92 parts, i.e. standard equivalent deduction) was removed. Comparative Example 10b: 80% carrier (silica reduced to 73.54 parts) was removed. Application Comparative Example 10c: Subtract 120% of the carrier (silica to 70.30 parts). The remaining formulation and mixing process are the same as in Application Example 1. Mooney viscosity and Payne effect were tested to determine the optimal subtraction ratio. Test data are shown in Table 13.

[0119] Application Comparative Example 11a 11e: Using 23.08 parts of the powder product from Example 1, the equivalent deduction rule was applied. The following mixing and debinding temperatures and ZBEC addition amounts (percentage of oil phase) were set: Comparative Example 11a: Debinding temperature 130℃, ZBEC addition 0.5 parts; Comparative Example 11b: Debinding temperature 140℃, ZBEC addition 0.5 parts; Comparative Example 11c: Debinding temperature 150℃, ZBEC addition 0.5 parts; Comparative Example 11d: Debinding temperature 145℃, ZBEC addition 0.05 parts; Comparative Example 11e: Debinding temperature 145℃, ZBEC addition amount 2.0 parts.

[0120] The remaining formulation and mixing process are the same as in Application Example 1. Mooney viscosity, scorch time (T10), and Payne effect were tested to verify the scorch safety of ZBEC at different temperatures and dosages. Comparative Example 11a was also applied. The test results for 11e are shown in Table 14.

[0121] Application Comparative Example 12: 23.03 parts of the pre-reactive modified oil phase intermediate (excluding ZBEC) from Example 1 were used, along with 0.12 parts of ZBEC powder (to ensure the total ZBEC amount was consistent with the oil phase amount in Example 1, i.e., 0.5 parts / 100 parts oil phase ratio). The two were added separately during the mixing process: the pre-reactive modified oil phase intermediate was added simultaneously with the raw rubber in liquid form, while the ZBEC powder was added directly in powder form during the second-stage mixing. The remaining formulation and mixing process were the same as in Example 1. Mooney viscosity, scorch time (T10), and crosslinking density after vulcanization were tested, and the results are shown in Table 15.

[0122] Application Comparison Example 13: The TDAE system formulation used in Comparative Example 1 was adopted, with an additional 0.2 parts of PVI (N-cyclohexylthiophthalimide, a typical scorching inhibitor). The remaining formulation and mixing process were the same as in Comparative Example 1. Test results are shown in Table 12.

[0123] Application Comparative Example 14: 23.08 parts of the powder product from Comparative Example 10 were used, and the equivalent subtraction rule was applied. The remaining formulation and mixing process were the same as in Application Example 1. The test results are as follows: Mooney viscosity ML(1+4) = 72.5, scorch time T10 = 11.8 min, Payne effect ΔG' = 3.45 MPa, tanδ at 60℃ = 0.158, and acetone extract content = 15.8%. These data indicate that, even under the same carrier load and equivalent subtraction conditions, the unreacted oil-phase physical mixture is less effective than Example 1 in improving filler dispersion and reducing extract content.

[0124] The rubber compounds obtained from Application Examples 1-5 and Application Comparative Examples 1-8 were tested, and the test results are shown in Table 8.

[0125] Table 8: Test results of rubber compounds obtained from Application Examples 1-5 and Comparative Examples 1-8

[0126] Note: The Mooney viscosity data in Table 8 are the average values ​​of three parallel experiments. The acetone extract content refers to the total amount of all small organic molecules in the vulcanized rubber that can be extracted by acetone, not specifically the free oil phase content.

[0127] As shown in Table 8, the Mooney viscosity of Application Example 1 was 62.5 MPa, and the Payne effect was 1.38 MPa; the Mooney viscosity of Application Comparative Example 1 was 68.5 MPa, and the Payne effect was 3.65 MPa. The lower Mooney viscosity and significantly reduced Payne effect of Application Example 1 indicate that the use of the solid softener of this invention helps improve the processing fluidity of the rubber compound and the uniformity of filler dispersion. The Payne effect of Application Comparative Example 2 was 2.85 MPa, higher than that of Application Example 1; Application Comparative Example 3 was 3.20 MPa; Application Comparative Example 4 was 2.95 MPa; Application Comparative Example 6 was 3.41 MPa, with a Mooney viscosity reaching 72.5; Application Comparative Example 8 had a Mooney viscosity of 76.8 MPa and a Payne effect of 1.76 MPa, all higher than that of Application Example 1. The above data comparison shows that the preferred pre-reaction temperature, TEOA catalysis, residual TEOA retention, carrier loading, and equivalent subtraction methods of this invention all play a positive role in improving processing fluidity and filler dispersion. The scorch time T10 of Application Example 1 was 16.0 min, longer than the 12.4 min of Application Comparative Example 1; the T10 of Application Examples 2-5 were all between 14.8 and 16.5 min, all superior to the traditional TDAE system. The T10 of Application Comparative Example 5 was significantly shortened to 10.2 min, indicating that when the TEOA dosage exceeded the limits of this invention, the scorch safety of the rubber compound decreased. The acetone extract content can reflect the overall fixation degree of the small organic molecule components in the vulcanizate. The extract content of Application Example 1 was 5.2%, a decrease of 11.6 percentage points compared to Application Comparative Example 1; the extract content of Application Examples 2-5 were between 5.0% and 5.6%, all superior to Application Comparative Example 1. The extract content of Application Comparative Example 7 was 7.8%, higher than that of Application Example 1; Application Comparative Example 4 was 14.8%. Analysis of the crosslinking density data in Table 15 shows that although Comparative Example 7 possesses a pre-reactive chain extender structure and TEOA, the lack of ZBEC's crosslinking-promoting effect results in a relatively low density of its vulcanizate crosslinking network, leading to a decrease in the efficiency of physical entanglement and fixation of the oil phase, manifested as a higher extract content. Regarding tear strength retention after hot air aging, Example 1 achieved 90.5%, 22 percentage points higher than Comparative Example 1; the retention rates of Examples 2-5 remained consistently above 89%, superior to all Comparative Examples. The tanδ at 60℃ for Example 1 was 0.109, lower than 0.165 for Comparative Example 1; the tanδ at 0℃ was 0.582, higher than 0.495 for Comparative Example 1. The tanδ at 60℃ for Examples 2-5 ranged from 0.106 to 0.116, and the tanδ at 0℃ ranged from 0.568 to 0.590, all superior to the traditional TDAE system, indicating that the solid softener of this invention achieves good anti-slip performance while reducing rolling resistance.

[0128] Table 9: Payne effect at different compounding and debinding temperatures

[0129] The above data shows that the Payne effect decreases continuously with increasing mixing temperature, without a clear critical temperature threshold. Higher mixing temperatures are beneficial for the formation of hydrogen bonds between TEOA and the silanol groups on the surface of silica, as well as for the uniform wetting of the modified oil phase on the filler surface. Therefore, it is recommended that the mixing discharge temperature not be lower than 140℃. At the same time, mixing at this temperature remains within the safe operating range for industrial rubber processing.

[0130] To verify the effect of the pre-adsorbed oil relative to the silanization reaction of Si69 using the equivalent subtraction rule, the bound rubber content of the compound used in Example 1 and Comparative Example 1 (TDAE blank control) was determined by low-field NMR (GB / T 46232-2025 "Determination of Bound Rubber Content in Uncured Rubber"). The results are shown in Table 10.

[0131] Table 10: Comparison of binder rubber content under different formulation systems

[0132] The above data indicate that the rubber content in Application Example 1 is higher than that in Comparative Example 1, and the filler-rubber interaction parameter α is also higher than that in the control group. This suggests that, under the conditions of the equivalent subtraction rule, the pre-adsorbed oil phase on the carrier did not negatively affect the silanization reaction between Si69 and the silica surface. This may be because, under the high temperature and high shear conditions of the internal mixer, the pre-adsorbed oil phase desorbs from the silica surface, providing usable active sites for the silanization reaction of Si69.

[0133] Table 11: Properties of the Rubber Compound in End-Value Examples

[0134] Table 12: Comparison of sulfidation kinetics between the system of this invention and the PVI anti-scorching agent system

[0135] As shown in Table 12, although the PVI anti-scorching agent prolongs T10, it also significantly prolongs T90, demonstrating comprehensive inhibition of sulfidation. In contrast, the system of this invention prolongs T10 to 16.0 min while significantly shortening T90 to 23.5 min, exhibiting typical delayed-start-accelerated sulfidation characteristics.

[0136] Table 13: Test data of Mooney viscosity and Payne effect for comparative examples 10a-10c

[0137] The test results of Comparative Examples 10a-10c show that when the carrier subtraction ratio is 100%, the Mooney viscosity is 62.5, the Payne effect is 1.38 MPa, and the tear strength is 53.8 kN / m. When the subtraction ratio is 80%, the Mooney viscosity increases to 65.0, and the Payne effect increases to 1.85 MPa, indicating that incomplete carrier subtraction leads to a higher total filler volume and increased filler network. When the subtraction ratio is 120%, the Mooney viscosity decreases to 60.8, and the Payne effect decreases to 1.25 MPa, achieving optimal processing fluidity. However, the tear strength decreases to 51.5 kN / m, slightly lower than in Example 1, indicating that excessive carrier subtraction may affect the reinforcing effect. Considering the three indicators of Mooney viscosity, Payne effect, and tear strength, 100% equivalent subtraction achieves the best balance between maintaining processing fluidity, filler dispersibility, and mechanical properties.

[0138] Table 14: Results of scorch time tests for comparative examples 11a-11e

[0139] As shown in Table 14, within the temperature range of 130-150℃, when the ZBEC addition amount is 0.5 parts, the scorch time T10 remains above 14 minutes, which is much higher than the 12.4 minutes of the traditional TDAE system (using Comparative Example 1). This indicates that ZBEC does not cause early scorch within the mixing temperature range of this invention. However, when the ZBEC addition amount increases to 2.0 parts (Comparative Example 11e), T10 shortens to 11.2 minutes, and the risk of scorch increases, proving that the ZBEC addition amount needs to be controlled within the range of 0.1-1.0 parts specified in this invention.

[0140] Table 15: Comparative test results between Application Example 12 and Application Example 1

[0141] Table 15 shows that when ZBEC is added directly in powder form, the scorch time is shortened from 16.0 min to 12.8 min, while the crosslinking density remains basically the same. This result proves that the addition of ZBEC plays a substantial role in the final crosslinking density; pre-compiling ZBEC into the modified oil phase can delay its release and activation in the early stage of mixing.

Claims

1. A bio-based rubber solid softener, characterized in that, Includes precipitated silica and a pre-reacted modified oil phase loaded within the pores of the precipitated silica; The content of the precipitated silica is 30wt%-40wt% by mass percentage, and the content of the pre-reactive modified oil phase is 60wt%-70wt%. The pre-reaction modified oil phase includes a pre-reaction modified oil phase intermediate and a vulcanization accelerator; The pre-reaction modified oil phase intermediate is prepared by the following components in parts by weight via triethanolamine-catalyzed ring-opening polymerization and chain extension pre-reaction: Flaxseed oil: 20-40 parts; Epoxidized vegetable oil: 50-70 parts; Cashew phenols: 8-12 parts; The amount of triethanolamine added is 1.49%-3.73% of the total weight of the flaxseed oil, epoxidized vegetable oil, and cashew nutmeg. After the pre-reaction modified oil phase intermediate has cooled, add 0.1-1.0 parts of vulcanization accelerator and mix evenly to obtain the pre-reaction modified oil phase; The vulcanization accelerator is zinc dibenzyl dithiocarbamate; The precipitated silica is precipitated silica that has undergone dehydration pretreatment; The pretreatment method for dehydration of precipitated silica is as follows: the precipitated silica is heated and dehydrated under vacuum conditions to obtain a pretreated carrier, and the endpoint is controlled so that the moisture content of the carrier is ≤0.5%.

2. The bio-based rubber solid softener according to claim 1, characterized in that, The content of the precipitated silica is 35 wt%, and the content of the pre-reactive modified oil phase is 65 wt%. The raw materials for preparing the pre-reaction modified oil phase, by weight, are: 30 parts linseed oil, 60 parts epoxidized vegetable oil, 10 parts cashew phenol, 0.5 parts vulcanization accelerator, and the amount of triethanolamine added is 1.5% of the total weight of linseed oil, epoxidized vegetable oil and cashew phenol.

3. The bio-based rubber solid softener according to claim 1 or 2, characterized in that, The flaxseed oil has an iodine value ≥170gI2 / 100g; the epoxidized vegetable oil is epoxidized soybean oil with an epoxy value ≥6.0%.

4. The bio-based rubber solid softener according to claim 1, characterized in that, The nitrogen adsorption specific surface area of ​​the precipitated silica is 155-190 m². 2 / g, CTAB specific surface area is 150-180m² 2 / g, DOP oil absorption value is 250-310mL / 100g.

5. A method for preparing a bio-based rubber solid softener according to any one of claims 1-4, characterized in that, The preparation method includes the following steps: S1. Pre-treatment of precipitated silica: Precipitated silica is heated and dehydrated under vacuum to obtain a pretreated carrier; S2. Oil phase pre-reaction: Linseed oil, epoxidized vegetable oil and cashew phenol are added to the reaction vessel according to the formula, and triethanolamine is added. The mixture is stirred at a constant temperature of 130℃-140℃ for 1.5-2.0 hours to allow the phenolic hydroxyl groups of cashew phenol to undergo a ring-opening etherification reaction with the internal epoxy groups of the epoxidized vegetable oil, thus obtaining a pre-reaction modified oil phase intermediate. After the reaction is completed, triethanolamine is not separated and the mixture is naturally cooled to 80℃-85℃. S3. Vulcanization accelerator compounding and physical adsorption to form powder: Vulcanization accelerator is added to the pre-reaction modified oil phase intermediate obtained in step S2, and stirred to disperse it evenly to form a stable microemulsion or submicron-level suspended dispersion oil phase system, thus obtaining pre-reaction modified oil; the pre-treated carrier obtained in step S1 is put into a high-shear mixer for fluidization, and the pre-reaction modified oil is sprayed into the mixer by atomization spraying. Then, the oil phase is adsorbed into the carrier mesopores by high-speed mechanical shearing, and cooled and sieved to obtain the bio-based rubber solid softener.

6. The method for preparing the bio-based rubber solid softener according to claim 5, characterized in that, In step S1, the temperature for vacuum dehydration is 115℃-125℃, the vacuum degree is ≤-0.09MPa, and the endpoint is controlled to have a carrier moisture content of ≤0.5%.

7. The method for preparing the bio-based rubber solid softener according to claim 5, characterized in that, In step S2, the reaction is carried out under nitrogen protection, with a stirring speed of 200-400 rpm, and the water content of the oil phase is ≤0.05% after the reaction is completed.

8. A method for applying the bio-based rubber solid softener according to any one of claims 1-4 in rubber products, characterized in that, The solid softener is used as a compounding agent and is added to the mixing equipment simultaneously with the raw rubber and basic fillers in the initial stage of the rubber mixing process for intensive mixing. The rubber product is then obtained by vulcanization molding.

9. The method for applying the bio-based rubber solid softener according to claim 8 in rubber products, characterized in that, When the solid softener is introduced into the original rubber formulation to replace the liquid softening oil, the dosage of each component shall be determined as follows: The total amount of solid softener added, W1, is determined by the amount of liquid softening oil in the original formula, W0, and the mass fraction C of the pre-reacted modified oil phase in the solid softener. The calculation formula is: W1 = W0 / C. Meanwhile, in the original formula, the amount of silica used as filler W2 is reduced by the mass of precipitated silica in the added solid softener to determine the adjusted amount of silica W3. The calculation formula is: W3=W2-W1×(1-C). The dosage of silane coupling agent is adjusted synchronously with the adjusted dosage of silica to determine the adjusted dosage of silane coupling agent W4. The calculation formula is: W4 = W3 × R, where R is the mass ratio of silane coupling agent to silica in the original formula.

Images