A low compression set rare earth modified EPDM rubber, its preparation method and application

Abstract

The application provides a low-compression-permanent-deformation rare earth modified EPDM rubber and a preparation method and application thereof, and comprises EPDM, rare earth core-shell particles, IL, sulfur, phenolic resin crosslinking agent, BMI, accelerator, antioxidant, paraffin oil, carbon black, stearic acid and processing aid. The application adopts a "one-step in-situ modification-mother rubber dilution-low-temperature mixing-common two-stage vulcanization" process, realizes uniform dispersion of the rare earth particles in the EPDM matrix, avoids agglomeration and frosting, the product has a CS value of 5.8%-7.8% under the condition of 100 DEG C * 70h / 25% compression, which is far lower than the existing 25%-35% and meets the requirement of ≤10% in high-end scenes, the CS retention rate is ≥90% after aging at 150 DEG C * 168h, and there is no rebound phenomenon; and the application is outstanding in balanced and stable mechanical properties, high and low temperature resistance and anti-aging performance, processing and use stability and the like, has strong industrialization feasibility, the process has low energy consumption and can be produced on a large scale, expands the application of the composition in the high-end sealing field, and meets the strict use requirements in scenes such as fuel cells, LNG equipment and spacecraft.

Description

Technical Field

[0001] This application belongs to the field of polymer materials technology, and in particular relates to a rare earth modified EPDM rubber with low compression set, its preparation method and application. Background Technology

[0002] EPDM, with its saturated main chain structure, exhibits excellent resistance to heat and oxygen, ozone, and weathering, making it widely used in automotive sealing, building curtain walls, and rail transit vibration damping pads. However, EPDM is a non-self-reinforcing rubber. Under conventional testing conditions of 100℃×70h / 25% compression, its vulcanizate exhibits a compression set (CS) of 25%-35%, which is insufficient to meet the CS ≤ 10% requirement for high-end applications such as fuel cell bipolar plate sealing, thus limiting its application in high-end fields.

[0003] Existing technologies for reducing EPDM compression set all have drawbacks: high-filler carbon black / silica technology leads to increased rubber density and poor low-temperature resilience; peroxide-based complete crosslinking technology has the problems of high risk of rubber scorching, high energy consumption and high cost; metal oxide addition technology can only reduce CS to about 20%, and it is prone to blooming at high temperatures; crosslinking agent addition technology will increase rubber hardness, increase brittle temperature, and lose low-temperature adaptability.

[0004] In summary, existing technologies cannot achieve the multi-performance improvement requirements of "low dosage, low hardness, low compression set, no CS rebound after aging, no frost formation, and low temperature resistance". This technological gap restricts the breakthrough of EPDM in the high-end sealing field. Therefore, the development of EPDM compositions with such comprehensive performance has important industrial value. Summary of the Invention

[0005] This application is made in view of the above-mentioned issues, and its purpose is to provide an EPDM rubber composition containing a "rare earth-organic synergistic structure" and to provide a method for preparing the composition, which can be achieved using conventional industrial equipment. Through specific process design, the rare earth particles are uniformly dispersed in the EPDM matrix, avoiding agglomeration and frosting. The process has low energy consumption and can be mass-produced, expanding the application of the composition in the field of high-end sealing and meeting the stringent requirements of fuel cells, LNG equipment, spacecraft and other scenarios.

[0006] The first aspect of this application provides a rare earth modified EPDM rubber with low compression set, comprising the following raw materials in parts by weight: 100 parts EPDM, 1.5–4.0 parts rare earth oxide core-shell particles, 0.3–1.2 parts ionic liquid monomer (IL), 0.3–0.8 parts sulfur, 1.0–2.5 parts phenolic resin crosslinking agent, 0.5–1.5 parts bismaleimide (BMI), 0.8–1.5 parts accelerator MBT, 0.3–0.6 parts accelerator TBzTD, 1.0–2.0 parts antioxidant 445, 15–25 parts paraffin oil, 40–60 parts carbon black, 1.0 part stearic acid, and 2.0 parts processing aid WB222;

[0007] The ionic liquid monomer is selected from 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt or 1-carboxypropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt;

[0008] The rare earth oxide core-shell particles are obtained by in-situ surface modification of rare earth oxides with epoxy-containing trimethoxysilane and ionic liquid monomers, wherein the rare earth oxides are CeO2 and La2O3.

[0009] In any embodiment, the EPDM contains 4.5 wt% ENB and has a Mooney viscosity of ML(1+4) 125℃ 55±5.

[0010] In any embodiment, the ionic liquid monomer is selected from 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt (VMIm NTf2, vinyl type) or 1-carboxypropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt (CPMIm NTf2, carboxyl type), with a purity ≥98%.

[0011] In any embodiment, the amount of the ionic liquid monomer is 0.3 times the total molar amount of the rare earth oxides.

[0012] In any embodiment, the carbon black is at least one of N550 and N330.

[0013] A second aspect of this application also provides a method for preparing rare earth modified EPDM rubber with low compression set, comprising the following steps:

[0014] S1 Masterbatch Preparation: Add 30 phr EPDM, rare earth oxide core-shell particles, ionic liquid monomer, antioxidant 445, and stearic acid to an internal mixer, set the temperature to 75-85℃ and the speed to 55-65 rpm, mix for 3-5 minutes, and then discharge the masterbatch.

[0015] S2 Dilution and Mixing: Add the remaining 70 phr EPDM, carbon black, paraffin oil, phenolic resin crosslinking agent, BMI, sulfur, accelerator MBT, accelerator TBzTD, and processing aid WB222 to the masterbatch. Set the temperature to 65-75℃ and the speed to 45-55 rpm, and mix for 5-7 minutes. During this period, observe the state of the rubber compound every 2 minutes to ensure that there is no carbon black clumping. The discharge temperature should be strictly controlled to ≤100℃.

[0016] S3 Thin pass-granulation: The compound from step S2 is fed into an open mill, the roll gap is adjusted to 0.4-0.6mm, thin pass 4-6 times, then the roll gap is adjusted to 1.8-2.2mm, and the sheet is produced; the sheet is fed into an underwater pelletizer, the cutter speed is set to 280-320rpm, the cooling water temperature is 18-22℃, and cylindrical rubber pellets with a diameter of 2.8-3.2mm and a length of 3.8-4.2mm are obtained;

[0017] S4 two-stage vulcanization:

[0018] S41 First-stage vulcanization (flat plate vulcanization): The rubber granules are placed into the mold of the flat plate vulcanizing machine, the temperature is set to 165-175℃, the pressure is 9-11MPa, and the temperature is maintained for 8-12 minutes to achieve the shaping and initial cross-linking of the rubber compound.

[0019] S42 Secondary Vulcanization (Hot Air Oven Two-Stage Vulcanization): After primary vulcanization, the rubber compound is removed from the mold and transferred to an electric heating oven. It is first kept at 115-125℃ for 1.2-1.8 hours, and then heated to 155-165℃ for 2.5-3.5 hours. The hot air velocity in the oven is controlled at 0.6-1.0 m / s to ensure uniform temperature.

[0020] S43 Cooling: After vulcanization, the rubber compound is naturally cooled to room temperature at a rate of ≤5℃ / min to avoid internal stress and obtain the final product.

[0021] Process parameter correlation explanation: The primary vulcanization temperature is inversely proportional to time—if the primary vulcanization temperature is adjusted to 165℃, the holding time is extended to 12 minutes; if the primary vulcanization temperature is adjusted to 175℃, the holding time is shortened to 8 minutes. The secondary vulcanization temperature is also inversely proportional to time—if the highest oven temperature is adjusted to 150℃, the holding time at 150℃ is extended to 4 hours; if the highest oven temperature is adjusted to 165℃, the holding time at 165℃ is shortened to 2.5 hours, ensuring consistent final crosslinking degree.

[0022] In any embodiment, the rotor torque of the internal mixer in step S1 is stabilized at 80-100 N·m, and the temperature of the discharged masterbatch is ≤90℃.

[0023] In any embodiment, the rare earth oxide core-shell particles are prepared as follows:

[0024] S01 Primary Modification (Re-O-Si Core-Shell Formation): Mix rare earth oxides according to a set molar ratio, add 10%-14% KH560 of the total mass of rare earth oxides, adjust the pH to 4.0-5.0, and react for 1.5-2.5 h at 75-85℃ and 250-350 rpm stirring rate.

[0025] SO2 washing and drying: The reaction solution is centrifuged at 7000-9000 rpm for 10-20 min, the precipitate is collected, washed with ethanol, and then dried at 55-65℃ and vacuum degree -0.10~-0.08MPa for 3-5 h to obtain “Re-O-Si” core-shell particles.

[0026] S03 secondary modification (supramolecular bridge formation): “Re-O-Si” core-shell particles are dispersed in an ethanol-water mixture, ionic liquid monomers are added, and the reaction is carried out at 20-30℃ and 150-250rpm for 0.8-1.2h.

[0027] S04 Spray drying: The reaction solution is dried by a spray dryer to obtain powdered rare earth oxide core-shell particles.

[0028] In any embodiment, the rare earth oxides are CeO2 and La2O3; the CeO2 has a particle size of 50-80 nm and a purity of ≥99.9%; the La2O3 has a particle size of 50-80 nm and a purity of ≥99.9%; the molar ratio of CeO2 to La2O3 is 1:1-2:1; and the volume ratio of the ethanol-water mixture is 8:2~9.5:0.5.

[0029] In any embodiment, the KH560 is added at a mass of 12% of the total mass of the rare earth oxides.

[0030] The third aspect of this application provides an application of rare earth modified EPDM rubber with low compression set, including the use of the above-mentioned rare earth modified EPDM rubber or rare earth modified EPDM rubber obtained by the preparation method for fuel cell bipolar plate seals, LNG cryogenic flange gaskets, spacecraft hatch O-rings, high-end building curtain wall seals, and rail transit vibration damping pads.

[0031] The beneficial effects of this application are:

[0032] 1) The core of this invention lies in constructing a synergistic system of “rare earth core-shell particles-supramolecular bridge-ternary cross-linking network”, and achieving performance breakthroughs through precise matching of process and formulation. a) In-situ surface modification of rare earth oxides (CeO2 and La2O3 composite system) was performed using epoxy-containing trimethoxysilane (KH560) to form a "Re-O-Si" core-shell structure, improving the compatibility of rare earth particles with the EPDM matrix; b) An ionic liquid monomer (IL) containing functional groups (vinyl, carboxyl) was introduced as a coordination second shell to form stable coordination bonds with the empty orbitals of rare earth ions, constructing a "Re-O-Si-IL" supramolecular bridge, further improving the dispersion stability of rare earth particles and suppressing high-temperature volatilization; c) A ternary vulcanization system of "sulfur-phenolic resin-bismaleimide (BMI)" was adopted to simultaneously generate three types of functionally complementary crosslinking bonds in the rubber network: sulfur provides "C-Sx-C" flexible crosslinking bonds to ensure elastic recovery; phenolic resin provides "methylene bridge" rigid crosslinking bonds to improve structural stability; and bismaleimide provides "imide bridge" high-temperature resistant crosslinking bonds to enhance aging resistance; d) Rare earth core-shell particles are bonded to the EPDM crosslinking network through supramolecular bridges to form an "organic-inorganic interpenetrating crosslinking domain". This region acts as a reversible "elastic node" during compression / rebound, uniformly distributing compressive stress and quickly restoring its shape, thereby achieving an extremely low CS value and no rebound after aging.

[0033] 2) Significantly reduced compression set: Under compression conditions of 100℃×70h / 25%, the CS value of the product is 5.8%-7.8%, which is far lower than the existing technology level (25%-35%) and the requirements of high-end scenarios (≤10%). After high-temperature aging at 150℃×168h, the CS value is still controlled at 6.4%-8.7% (value-added rate ≤10%), the CS retention rate is ≥90%, and there is no rebound phenomenon, which demonstrates excellent anti-aging stability.

[0034] 3) Balanced and stable mechanical properties: Hardness is controlled at 68-73 Shore A (low hardness), tensile strength is 18.2-19.4MPa, and elongation at break is 355%-380%, which meets the mechanical load-bearing and assembly requirements of the seal.

[0035] 4) Excellent resistance to high and low temperatures and anti-aging properties: brittle temperature ≤ -55℃, suitable for LNG cryogenic conditions (-162℃), and can withstand long-term aging at 150℃, with high performance retention rate after high and low temperature cycles.

[0036] 5) Good processing and usage stability: The rare earth particles are uniformly dispersed through the "masterbatch dilution-low temperature mixing" process, with no agglomeration; there is no frosting at high temperatures (frost amount <0.1mg / cm³). 2It does not contaminate the sealing contact surface; it adopts a common vulcanization process, requires no special equipment, has high scorch safety of rubber compound (scorch time t5≥8min at 125℃), and has strong industrial feasibility. Attached Figure Description

[0037] Figure 1 This is a scanning electron microscope (SEM) image of the rare earth-modified EPDM rubber with low compression set according to this application. Detailed Implementation

[0038] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of a rare-earth modified EPDM rubber with low compression set, its preparation method, and its applications. However, unnecessary details may be omitted. For example, detailed descriptions of well-known facts and repetitive descriptions of essentially identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of providing a full understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0039] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0040] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0041] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0042] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0043] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0044] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0045] This invention addresses the problems of high compression set, performance rebound after aging, poor adaptability to high-end applications, and dependence on special vulcanization equipment in existing EPDM rubber. By constructing a "rare earth core-shell particle-supramolecular bridge-ternary crosslinking network" system through "formula synergy + process optimization", it achieves the unity of synergistic optimization of multiple properties and industrial feasibility.

[0046] Rare earth core-shell particles were prepared using a two-layer in-situ modification process of "silane-ionic liquid monomer". By precisely controlling the reaction parameters, the rare earth particles were uniformly dispersed in the EPDM matrix, while suppressing high-temperature frost formation. This method is different from traditional unmodified or single silane-modified rare earths.

[0047] By combining the "sulfur-phenolic resin-bismaleimide" ternary vulcanization system with rare earth elements, the three crosslinking bonds complement each other, ensuring low compression set and improving anti-aging stability, thus breaking through the performance limitations of traditional single vulcanization systems.

[0048] By adopting the process of "one-step in-situ modification - masterbatch dilution - low-temperature mixing - ordinary two-stage vulcanization", an integrated process of "masterbatch dilution - low-temperature mixing - ordinary two-stage vulcanization" has been developed. No special equipment is required. Through parameter gradient design, the complete crosslinking and performance stability are unified, which solves industry problems such as rare earth particle agglomeration, rubber scorching, and high-temperature frost formation. Moreover, it has lower energy consumption and can be industrially scaled up.

[0049] Achieving a synergistic effect of "low CS (5.8%-7.8%), low hardness (68-73 Shore A), anti-aging rebound (retention rate ≥90%), no frost formation, and low temperature resistance (≤-55℃)" breaks through the inherent contradictions of existing technologies and fills a gap in the industry.

[0050] The technical solution of this invention has clear process parameters and repeatable performance verification. It can be implemented without relying on special equipment and characterization data. The product can be widely used in high-end sealing fields and has significant industrial value and market prospects.

[0051] In one embodiment of this application, a rare earth modified EPDM rubber with low compression set is provided, comprising the following raw materials in parts by weight: 100 parts EPDM, 1.5–4.0 parts rare earth oxide core-shell particles, 0.3–1.2 parts ionic liquid monomer (IL), 0.3–0.8 parts sulfur, 1.0–2.5 parts phenolic resin crosslinking agent, 0.5–1.5 parts bismaleimide (BMI), 0.8–1.5 parts accelerator MBT, 0.3–0.6 parts accelerator TBzTD, 1.0–2.0 parts antioxidant 445, 15–25 parts paraffin oil, 40–60 parts carbon black, 1.0 part stearic acid, and 2.0 parts processing aid WB222;

[0052] The ionic liquid monomer is selected from 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt or 1-carboxypropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt;

[0053] The rare earth oxide core-shell particles are obtained by in-situ surface modification of rare earth oxides with epoxy-containing trimethoxysilane and ionic liquid monomers, wherein the rare earth oxides are CeO2 and La2O3.

[0054] Rare earth oxide core-shell particles are the core functional components. A dosage below 1.5 phr results in insufficient CS improvement (CS>10%), while a dosage above 4.0 phr easily leads to particle agglomeration and increases production costs. Sulfur provides flexible crosslinking bonds; a dosage below 0.3 phr results in insufficient crosslinking density, while a dosage above 0.8 phr easily causes blooming. The phenolic resin crosslinking agent, HRJ-10565, has high reactivity, ensuring the formation of stable methylene bridges. A dosage below 1.0 phr results in insufficient structural stability, while a dosage above 2.5 phr leads to increased rubber hardness. Bismaleimide (BMI) provides high-temperature resistant crosslinking bonds; a dosage below 0.5 phr results in significant CS rebound after aging, while a dosage above 1.5 phr increases rubber brittleness. Thiazole accelerators adjust... The crosslinking rate is controlled; a dosage below 0.8 phr results in an excessively long vulcanization cycle, while a dosage above 1.5 phr increases the risk of scorching. Thiuram-based accelerators, working synergistically with MBT, improve crosslinking uniformity and vulcanization efficiency. Antioxidants possess both heat- and ozone-resistant aging properties; a dosage below 1.0 phr results in insufficient aging performance, while a dosage above 2.0 phr easily leads to migration and precipitation. Paraffin oil is an environmentally friendly plasticizer that improves processing fluidity and rubber flexibility; a dosage below 15 phr makes mixing difficult, while a dosage above 25 phr easily causes blooming. Carbon black acts as a semi-reinforcing agent, balancing mechanical properties and processing fluidity. Stearic acid acts as a vulcanization activator, lowering the vulcanization temperature; a fixed dosage ensures formulation stability. Processing aids improve mixing uniformity and release properties; a fixed dosage ensures stable processing.

[0055] In any embodiment, the EPDM contains 4.5 wt% ENB and has a Mooney viscosity of ML(1+4) 125℃ 55±5.

[0056] The ENB content in EPDM ensures cross-linking activity and guarantees a full reaction in the ternary vulcanization system. Mooney viscosity balances processing flowability and mechanical properties, preventing roller sticking or insufficient mechanical strength.

[0057] In any embodiment, the ionic liquid monomer is selected from 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt (VMIm NTf2, vinyl type, imidazolium cation with vinyl (–CH=CH2), and an anion of NTf2). - ) or 1-carboxypropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt (CPMIm NTf2, carboxyl type, imidazolium cationic side chain with carboxyl group (–COOH), anion is NTf2 - Purity ≥ 98%.

[0058] 1-Vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt (VMIm NTf2, vinyl type) or 1-carboxypropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt (CPMIm NTf2, carboxyl type), with a purity ≥98%; the amount used is 0.3 times the total molar amount of rare earth oxides to ensure sufficient coordination with rare earth ions. Insufficient amount will result in insufficient coordination, while excessive amount will easily lead to migration and precipitation.

[0059] In any embodiment, the amount of the ionic liquid monomer is 0.3 times the total molar amount of the rare earth oxides.

[0060] In any embodiment, the carbon black is at least one of N550 and N330.

[0061] In one embodiment of this application, a method for preparing rare earth modified EPDM rubber with low compression set is proposed, which adopts a "one-step in-situ modification-masterbatch dilution-low temperature mixing-ordinary two-stage vulcanization" process, and the specific steps are as follows:

[0062] S1 Masterbatch Preparation:

[0063] Equipment: 5L internal mixer (temperature control accuracy ±2℃, speed adjustable);

[0064] Operation: Add 30 phr EPDM, all rare earth oxide core-shell particles, all ionic liquid monomers, all antioxidant 445, and 1.0 phr stearic acid to the internal mixer. Set the temperature to 75-85℃ and the speed to 55-65 rpm, and mix for 3-5 minutes (ensure that the rotor torque is stable at 80-100 N·m to ensure that the materials are fully mixed). Discharge the masterbatch (temperature ≤90℃).

[0065] The initial uniform dispersion of rare earth particles is achieved by mixing high-concentration materials, avoiding agglomeration caused by direct mixing.

[0066] A temperature range of 75-85℃ can balance the dispersion efficiency of rare earth particles and the thermal stability of the rubber compound, avoiding premature cross-linking. When the temperature is below 75℃, the activity of the EPDM molecular chain is low, and it is difficult to uniformly disperse the rare earth core-shell particles and ionic liquid monomers, which makes the finished product prone to agglomeration. When the temperature is above 85℃, the temperature rise of the rubber compound is too fast, the antioxidant is consumed prematurely, and there is also a risk of scorching due to early cross-linking, which leads to a decrease in the processing performance of the masterbatch.

[0067] A rotation speed of 55-65 rpm provides moderate shear force, promoting the dispersion of rare earth particles without excessive heat generation. When the rotation speed is <55 rpm, the shear force is insufficient, and rare earth particles are prone to agglomeration; when the rotation speed is >65 rpm, shear heat generation intensifies within the internal mixer, causing the rubber compound temperature to rapidly exceed the threshold and trigger scorching.

[0068] A mixing time of 3-5 minutes can achieve uniform mixing of all components, balancing efficiency and energy consumption. When the time is less than 3 minutes, the materials are not mixed sufficiently, and rare earth particles are not dispersed evenly; when the time is greater than 5 minutes, the rubber compound generates excessive heat due to excessive shearing, increasing the risk of scorching and increasing production energy consumption.

[0069] Rotor torque 80-100N m, discharge temperature ≤90℃, and stable torque within this range proves that the materials are fully mixed and there is no abnormal load; discharge temperature control prevents premature cross-linking of the masterbatch. Torque <80N When m, the material is not mixed sufficiently; torque > 100N When the temperature is above 90℃, the equipment load is too high, which can easily cause component damage; when the discharge temperature is above 90℃, there is a risk of premature cross-linking of the masterbatch, which increases the difficulty of subsequent dilution and mixing.

[0070] S2 dilution and mixing:

[0071] Equipment: 5L internal mixer, same as in step S1;

[0072] Procedure: Add the remaining 70 phr EPDM, carbon black, paraffin oil, phenolic resin crosslinking agent, BMI, sulfur, accelerator MBT, accelerator TBzTD, and processing aid WB222 to the masterbatch. Set the temperature to 65-75℃ and the speed to 45-55 rpm, and mix for 5-7 minutes. Observe the state of the rubber compound every 2 minutes during this period to ensure that there is no carbon black clumping. Strictly control the discharge temperature to ≤100℃ (to prevent premature crosslinking of the rubber compound and ensure the safety of subsequent processing).

[0073] The remaining components are gradually introduced under low temperature conditions to ensure that the components of the formula are evenly dispersed and to avoid premature reaction of the vulcanization system caused by high temperature.

[0074] At temperatures of 65-75℃, low-temperature mixing can prevent premature reaction of the vulcanization system, including sulfur and accelerators, while ensuring uniform dispersion of carbon black. When the temperature is below 65℃, the rubber compound has high viscosity, making it difficult for carbon black to penetrate and disperse, and it is prone to agglomeration. When the temperature is above 75℃, the vulcanization system is activated prematurely, resulting in scorching of the rubber compound and large fluctuations in the performance of the subsequent vulcanized finished product.

[0075] A rotation speed of 45-55 rpm is recommended. Lower rotation speed reduces the rate of temperature rise in the rubber compound, ensuring the stability of the vulcanization system. When the rotation speed is <45 rpm, the mixing efficiency is low, and the carbon black and crosslinking agent are unevenly dispersed. When the rotation speed is >55 rpm, shear heat generation is rapid, and the rubber compound temperature is likely to exceed 100℃, causing premature reaction in the vulcanization system.

[0076] A mixing time of 5-7 minutes ensures complete dispersion of carbon black and uniform distribution of the crosslinking agent. When the time is less than 5 minutes, the carbon black is prone to agglomeration, resulting in a decrease in the mechanical properties of the finished product; when the time is greater than 7 minutes, the rubber compound heats up and ages, leading to poor processing performance.

[0077] The discharge temperature should be ≤100℃ to prevent premature cross-linking of the vulcanization system and ensure a suitable processing window for the rubber compound. When the discharge temperature is >100℃, the vulcanization system reacts prematurely, causing the rubber compound to scorch and preventing normal subsequent vulcanization molding.

[0078] S3 Thin-walled Granulation:

[0079] Equipment: Open mill (adjustable roll gap, temperature ≤60℃), underwater pelletizer;

[0080] Operation: Feed the mixed rubber into the open mill, adjust the roller gap to 0.4-0.6mm, and pass it through the mill 4-6 times (turning the rubber over after each pass to remove air bubbles). Then adjust the roller gap to 1.8-2.2mm and produce sheets (sheet thickness uniformity deviation ≤ ±0.1mm). Feed the sheets into an underwater pelletizer, set the cutter speed to 280-320rpm, and the cooling water temperature to 18-22℃ to obtain cylindrical rubber pellets with a diameter of 2.8-3.2mm and a length of 3.8-4.2mm (particle size uniformity deviation ≤ ±0.2mm).

[0081] This further improves the uniformity of the rubber compound, eliminates internal defects, and facilitates subsequent vulcanization molding.

[0082] A thin-pass roller gap of 0.4-0.6mm and 4-6 passes are recommended. This roller gap and number of passes effectively break up air bubbles inside the rubber compound, eliminate stress concentration, and improve the uniformity of the rubber compound. When the roller gap is <0.4mm, the rubber compound is subjected to excessive shear force, which can easily damage the open mill rollers and cause fatigue aging of the rubber compound. When the roller gap is >0.6mm or the number of passes is <4, air bubbles cannot be effectively broken up, and the finished product has internal defects. When the number of passes is >6, the rubber compound is excessively sheared, and its elasticity decreases.

[0083] The sheeting roller gap is 1.8-2.2mm to ensure uniform sheet thickness and facilitate subsequent pelleting. When the roller gap is <1.8mm, the sheet is too thin and prone to breakage during pelleting; when the roller gap is >2.2mm, the sheet is too thick, resulting in uneven pellet size after pelleting, which affects the uniformity of heating during subsequent vulcanization.

[0084] The cutting speed is 280-320 rpm, and the cooling water temperature is 18-22℃ to stabilize cutting efficiency and particle shape. The cooling water quickly cools the pellets and prevents them from sticking together. When the speed is <280 rpm, the particle shape is irregular; when the speed is >320 rpm, the shearing force is too large and the particles are easily broken; when the water temperature is <18℃, the cooling rate is too fast and stress is generated inside the particles; when the water temperature is >22℃, the cooling is insufficient and the particles are prone to sticking together and clumping.

[0085] The rubber granules have a diameter of 2.8-3.2 mm and a length of 3.8-4.2 mm, ensuring uniform particle size and guaranteeing that the rubber compound fills the mold and is heated evenly during the first stage of vulcanization. If the size is less than the lower limit, the rubber granules are prone to leakage; if the size is greater than the upper limit, the rubber granules will not fill the mold sufficiently, and the finished product is prone to defects such as insufficient rubber.

[0086] S4 two-stage vulcanization:

[0087] Equipment: Flat vulcanizing machine (temperature control accuracy ±2℃, pressure adjustable range 0-20MPa), electric heating blast oven (temperature control accuracy ±2℃, wind speed adjustable);

[0088] First-stage vulcanization (flat plate vulcanization): The rubber granules are placed into the mold of the flat plate vulcanizing machine, the temperature is set to 165-175℃ and the pressure to 9-11MPa, and the temperature is maintained for 8-12 minutes to achieve the shaping and initial cross-linking of the rubber compound (ensuring that the rubber compound completely fills the mold without any missing rubber).

[0089] A temperature of 165-175℃, a pressure of 9-11MPa, and a holding time of 8-12min can achieve rubber compound shaping and initial cross-linking. The inverse relationship between temperature and time ensures consistent cross-linking degree. When the temperature is <165℃ or the time is <8min, the cross-linking degree is insufficient, and the compression set (CS) value of the finished product increases; when the temperature is >175℃ or the time is >12min, the cross-linking is excessive, the rubber brittleness increases, and the elongation at break decreases; when the pressure is <9MPa, the rubber compound cannot completely fill the mold, and the finished product has missing rubber and air bubbles; when the pressure is >11MPa, the mold is easily damaged, and the rubber compound is too dense, resulting in decreased elasticity.

[0090] Secondary vulcanization (two-stage vulcanization in hot air oven): After primary vulcanization, the rubber compound is removed from the mold and transferred to an electric hot air oven. It is first kept at 115-125℃ for 1.2-1.8h (to remove residual low-molecular-weight volatiles in the rubber compound), and then heated to 155-165℃ for 2.5-3.5h (to ensure complete cross-linking reaction). The hot air velocity in the oven is controlled at 0.8m / s to ensure uniform temperature.

[0091] The low-temperature section (115-125℃, 1.2-1.8h) effectively removes residual low-molecular-weight volatiles from the rubber compound, preventing blooming in the finished product. When the temperature is <115℃ or the time is <1.2h, the low-molecular-weight substances are not completely removed, making the finished product prone to blooming at high temperatures. When the temperature is >125℃ or the time is >1.8h, energy consumption increases, and the rubber compound surface is prone to premature aging.

[0092] The high-temperature stage (155-165℃, 2.5-3.5h) ensures deep cross-linking, enhancing the finished product's anti-aging properties. The inverse relationship between temperature and time guarantees complete but not excessive cross-linking. At temperatures <155℃ or times <2.5h, cross-linking is incomplete, resulting in a significant rebound in the CS value after aging at 150℃. At temperatures >165℃ or times >3.5h, excessive cross-linking occurs, increasing rubber hardness and decreasing low-temperature brittleness.

[0093] A hot air velocity of 0.6-1.0 m / s ensures uniform temperature within the oven and prevents uneven cross-linking of the adhesive. When the velocity is <0.6 m / s, the temperature gradient within the oven is large, resulting in uneven cross-linking of the adhesive in different parts and performance fluctuations. When the velocity is >1.0 m / s, energy consumption increases, and the adhesive surface is prone to cracking, affecting appearance and sealing performance.

[0094] Cooling: After vulcanization, allow the rubber compound to cool naturally to room temperature (cooling rate ≤ 5℃ / min, to avoid generating internal stress) to obtain the final product;

[0095] Cooling rate ≤ 5℃ / min: Slow cooling avoids internal stress in the rubber compound, ensuring dimensional stability and mechanical properties of the finished product. Cooling rate > 5℃ / min: Large temperature difference between the inside and outside of the rubber compound generates internal stress, making the finished product prone to cracking and reducing compression set performance; excessively slow cooling rate reduces production efficiency and increases time costs.

[0096] Process parameter correlation explanation: The primary vulcanization temperature is inversely proportional to time—if the primary vulcanization temperature is adjusted to 165℃, the holding time is extended to 12 minutes; if the primary vulcanization temperature is adjusted to 175℃, the holding time is shortened to 8 minutes. The secondary vulcanization temperature is also inversely proportional to time—if the highest oven temperature is adjusted to 150℃, the holding time at 150℃ is extended to 4 hours; if the highest oven temperature is adjusted to 165℃, the holding time at 165℃ is shortened to 2.5 hours, ensuring consistent final crosslinking degree.

[0097] In some implementations, rare earth oxide core-shell particles (Re-O-Si-IL structure).

[0098] Raw material selection:

[0099] Rare earth oxides: CeO2 (particle size 50-80nm, purity ≥99.9%) and La2O3 (particle size 50-80nm, purity ≥99.9%), molar ratio 1:1 or 2:1; silane coupling agent: 3-(glycidyl ether oxypropyl)trimethoxysilane (KH560, purity ≥98%); solvent: ethanol-water mixture (volume ratio 9:1).

[0100] Preparation steps:

[0101] S01 primary modification (Re-O-Si core-shell formation): Mix CeO2 and La2O3 at a set molar ratio, add 10%-14% of KH560 by total mass of rare earth oxides, adjust the pH of the system to 4.0-5.0 with hydrochloric acid or acetic acid, and react for 1.5-2.5 h at 75-85℃ and 250-350 rpm.

[0102] The dosage of KH560 is 10%-14% of the total mass of rare earth oxides. This ensures that the silane coupling agent fully coats the rare earth oxide particles, forming a dense "Re-O-Si" core-shell structure, while avoiding particle agglomeration caused by excessive silane. When the dosage is <10%, the surface coating of rare earth oxides is insufficient, resulting in poor compatibility with the EPDM matrix. When the dosage is >14%, excessive KH560 will undergo self-aggregation, leading to larger core-shell particle sizes and decreased dispersibility.

[0103] A slightly acidic environment with a pH of 4.0-5.0 promotes the hydrolysis of KH560, and the generated silanol groups can undergo condensation reactions with the hydroxyl groups on the surface of rare earth oxides to form stable covalent bonds. When pH < 4.0, the hydrolysis rate is too fast, and silanes easily self-polymerize to form a gel, which cannot uniformly coat the rare earth particles; when pH > 5.0, the hydrolysis reaction is incomplete, the silanol content is insufficient, the core-shell structure has weak bonding force, and it is easy to detach later.

[0104] A reaction temperature of 75-85℃ can balance the hydrolysis-condensation reaction rate, ensuring a uniform and dense core-shell structure. At temperatures below 75℃, the reaction rate is slow, and the core-shell structure is not fully formed; at temperatures above 85℃, the reaction is too vigorous, particles are prone to agglomeration, and the silane coupling agent may undergo thermal decomposition, reducing the coating effect.

[0105] A stirring speed of 250-350 rpm is recommended. A moderate stirring speed ensures sufficient contact between rare earth oxides and KH560, preventing agglomeration caused by excessively high local concentrations. When the stirring speed is less than 250 rpm, the material is mixed unevenly, with some areas over-coated while others remain uncoated. When the stirring speed is greater than 350 rpm, the shear force is too high, which can easily damage the initially formed core-shell structure and increase energy consumption.

[0106] A reaction time of 1.5-2.5 hours ensures complete hydrolysis and condensation, resulting in a stable core-shell structure. A reaction time < 1.5 hours leads to incomplete reaction and a loose core-shell structure; a reaction time > 2.5 hours increases the risk of particle aggregation, prolongs the production cycle, and reduces efficiency.

[0107] SO2 washing and drying: The reaction solution is centrifuged at 7000-9000 rpm for 10-20 min, the precipitate is collected, and washed 3 times with ethanol to remove unreacted KH560. Then it is dried at 55-65℃ and vacuum degree -0.10~-0.08MPa for 3-5 h to obtain “Re-O-Si” core-shell particles.

[0108] A centrifugation speed of 7000-9000 rpm and a centrifugation time of 10-20 min are optimal for efficient separation of unreacted KH560 and byproducts, ensuring precipitate purity. When the speed is <7000 rpm or the time is <10 min, the precipitate separation is insufficient, leaving many impurities and affecting the subsequent core-shell particle performance. When the speed is >9000 rpm or the time is >20 min, the centrifugal force is too high, easily causing core-shell particles to aggregate and increasing equipment wear.

[0109] The drying temperature is 55-65℃. Low-temperature vacuum drying can remove the ethanol solvent on the particle surface and avoid particle agglomeration caused by high temperature. When the temperature is <55℃, the drying rate is slow and there is more solvent residue, which affects the subsequent secondary modification reaction. When the temperature is >65℃, the hydroxyl groups on the particle surface are prone to condensation reaction, which leads to agglomeration and destroys the dispersibility of the core-shell structure.

[0110] A vacuum level of -0.10 to -0.08 MPa is required. This vacuum level lowers the solvent boiling point, accelerates the drying process, and prevents particle oxidation caused by air ingress. When the vacuum level is greater than -0.08 MPa (insufficient vacuum), the drying rate is slow and the drying time is prolonged; when the vacuum level is less than -0.10 MPa, particles are easily drawn away, resulting in material loss.

[0111] A drying time of 3-5 hours ensures complete solvent removal, resulting in dry and loose core-shell particles. If the drying time is less than 3 hours, solvent residue remains, hindering uniform adsorption of the ionic liquid monomer in subsequent secondary modification. If the drying time is greater than 5 hours, the risk of particle aggregation increases, and energy consumption also increases.

[0112] S03 secondary modification (supramolecular bridge formation): "Re-O-Si" core-shell particles are dispersed in an ethanol-water mixture (solid-liquid ratio 1:50, mass-volume ratio), and ionic liquid monomers (VMIm NTf2 or CPMIm NTf2) are added. The mixture is reacted at 20-30℃ and 150-250rpm for 0.8-1.2h.

[0113] An ethanol-water volume ratio of 8:2 to 9.5:0.5 is recommended. A high ethanol content in the mixture ensures uniform dispersion of the Re-O-Si core-shell particles and provides a suitable environment for the coordination reaction between the ionic liquid monomer and the particle surface. When the water content is >20% (volume ratio <8:2), the particles are prone to aggregation due to hydrophilic interactions. When the ethanol content is >95% (volume ratio >9.5:0.5), the solubility of the ionic liquid monomer decreases, preventing sufficient coordination reactions with the particle surface and resulting in inadequate supramolecular bridge formation.

[0114] The reaction temperature is 20-30℃. The room temperature range avoids thermal decomposition of the ionic liquid monomers and ensures a stable coordination reaction rate. At temperatures below 20℃, the reaction rate is slow, and supramolecular bridges are not fully formed; at temperatures above 30℃, the ionic liquid monomers may thermally decompose, lose their coordination function, and the particles are prone to aggregation.

[0115] A stirring rate of 150-250 rpm is recommended. A gentle stirring rate allows the ionic liquid monomers to be uniformly coated on the surface of the core-shell particles, while avoiding damage to the already formed "Re-O-Si" structure. When the stirring speed is <150 rpm, the ionic liquid monomers are unevenly dispersed, and the coordination reaction is insufficient; when the stirring speed is >250 rpm, the shear force is too high, which can easily damage the core-shell structure and lead to a decrease in the supramolecular bridge bonding force.

[0116] The reaction time is 0.8-1.2 h, which ensures sufficient coordination between the ionic liquid monomer and the core-shell particle surface to form stable supramolecular bridges. When the time is <0.8 h, the coordination reaction is incomplete and the supramolecular bridge density is low; when the time is >1.2 h, there is no significant performance improvement and the production cycle is prolonged.

[0117] S04 Spray drying: The reaction solution is dried by a spray dryer (inlet temperature 120℃, outlet temperature 60℃, atomization pressure 0.3MPa) to obtain powdered rare earth oxide core-shell particles.

[0118] Example

[0119] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0120] Example 1

[0121] Formulation parameters: EPDM 100 phr (ENB content 4.5wt%, Mooney viscosity ML(1+4) 125℃ 55±5), rare earth oxide core-shell particles 1.5 phr, 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt (VMIm NTf2) 0.3 phr, sulfur 0.5 phr, phenolic resin crosslinking agent (HRJ-10565) 1.8 phr, bismaleimide (BMI) 1.0 phr, accelerator MBT 1.2 phr, accelerator TBzTD 0.45 phr, antioxidant 445 1.5 phr, paraffin oil 20 phr, carbon black N550 50 phr, stearic acid 1.0 phr, processing aid WB222 2.0 phr.

[0122] Preparation process:

[0123] S1 Masterbatch Preparation: 30 phr EPDM, all rare earth oxide core-shell particles, all VMIm NTf2, all antioxidant 445 and 1.0 phr stearic acid are put into a 5L internal mixer. The temperature is set to 80℃ and the speed is 60 rpm. The mixture is mixed for 4 min (the rotor torque is stabilized at 80-100 N·m). The discharge temperature is ≤90℃ to obtain the masterbatch.

[0124] S2 dilution and mixing: Add the remaining 70 phr EPDM, carbon black N550, paraffin oil, phenolic resin crosslinking agent, BMI, sulfur, accelerator MBT, accelerator TBzTD and processing aid WB222 to the masterbatch. Set the temperature to 70℃ and the speed to 50 rpm, and mix for 6 min (observe every 2 min to ensure no carbon black agglomeration). The discharge temperature should be ≤100℃.

[0125] S3 Thin Pass - Granulation: The mixed rubber is fed into the open mill, the roller gap is adjusted to 0.5 mm, thin pass 5 times (each time the rubber is turned over to remove bubbles), the roller gap is adjusted to 2 mm to produce sheets (thickness deviation ≤ ±0.1 mm), and then it is processed by an underwater pelletizer (cutter speed 300 rpm, cooling water 20℃) to produce cylindrical rubber pellets with a diameter of 3 mm and a length of 4 mm (particle size deviation ≤ ±0.2 mm).

[0126] S4 Two-stage vulcanization: The granules are kept at 170℃ and 10 MPa for 10 min in a flat vulcanizing machine to complete the first stage of vulcanization; then they are transferred to an electric heating blast oven for the second stage of vulcanization, first kept at 120℃ for 1.5 h, and then heated to 160℃ for 3 h (hot air velocity 0.8 m / s); after vulcanization, they are naturally cooled to room temperature (cooling rate ≤5℃ / min).

[0127] Test performance data: Compression set (CS) was 7.8% under 25% compression conditions at 100℃ for 70h; CS was 7.0% after aging at 150℃ for 168h (retention rate ≥90%); hardness was 68 Shore A; tensile strength was 18.2 MPa; elongation at break was 380%; brittle temperature was ≤-55℃; and efflorescence was <0.1 mg / cm³. 2 The particles are evenly dispersed without agglomeration.

[0128] Example 2

[0129] Formulation parameters: rare earth oxide core-shell particles 2.0 phr, VMIm NTf 20.5 phr (the remaining components and amounts are the same as in Example 1).

[0130] Preparation process: Steps S1-S4 are the same as in Example 1, and the materials are added according to the formula parameters of this example.

[0131] Test performance data: CS 6.9%, CS after aging 6.2%, hardness 69 Shore A, tensile strength 18.7 MPa, elongation at break 375%, brittle temperature ≤ -55℃, efflorescence < 0.1 mg / cm² 2 The particles are evenly dispersed without agglomeration.

[0132] Example 3

[0133] Formulation parameters: rare earth oxide core-shell particles 2.5 phr, VMIm NTf 20.7 phr (the remaining components and amounts are the same as in Example 1).

[0134] Preparation process: Steps S1-S4 are the same as in Example 1, and the materials are added according to the formula parameters of this example.

[0135] Test performance data: CS 6.3%, CS after aging 5.7%, hardness 70 Shore A, tensile strength 19.1 MPa, elongation at break 370%, brittle temperature ≤ -55℃, efflorescence < 0.1 mg / cm² 2 The particles are evenly dispersed without agglomeration.

[0136] Example 4 (Baseline Formulation)

[0137] Formulation parameters: rare earth oxide core-shell particles 3.0 phr, VMIm NTf 20.9 phr (the remaining components and amounts are the same as in Example 1).

[0138] Preparation process: Steps S1-S4 are the same as in Example 1, and the materials are added according to the formula parameters of this example.

[0139] Test performance data: CS 5.8%, CS after aging 5.2%, hardness 71 Shore A, tensile strength 19.4 MPa, elongation at break 365%, brittle temperature ≤ -55℃, efflorescence < 0.1 mg / cm² 2 The particles are evenly dispersed without agglomeration.

[0140] Example 5

[0141] Formulation parameters: rare earth oxide core-shell particles 3.5 phr, VMIm NTf 21.0 phr (the remaining components and amounts are the same as in Example 1).

[0142] Preparation process: Steps S1-S4 are the same as in Example 1, and the materials are added according to the formula parameters of this example.

[0143] Test performance data: CS 5.9%, CS after aging 5.3%, hardness 72 Shore A, tensile strength 19.2 MPa, elongation at break 360%, brittle temperature ≤ -55℃, efflorescence < 0.1 mg / cm² 2 The particles are evenly dispersed without agglomeration.

[0144] Example 6

[0145] Formulation parameters: rare earth oxide core-shell particles 4.0 phr, VMIm NTf 21.2 phr (the remaining components and amounts are the same as in Example 1).

[0146] Preparation process: Steps S1-S4 are the same as in Example 1, and the materials are added according to the formula parameters of this example.

[0147] Test performance data: CS 6.1%, CS after aging 5.5%, hardness 73 Shore A, tensile strength 18.9 MPa, elongation at break 355%, brittle temperature ≤ -55℃, efflorescence < 0.1 mg / cm² 2 The particles are evenly dispersed without agglomeration.

[0148] Example 7

[0149] Formulation parameters: The molar ratio of CeO2 to La2O3 was adjusted to 2:1 (1:1 in Example 4), the total amount of rare earth oxides was kept at 3.0 phr, and VMIm NTf 20.9 phr (the other components and amounts were the same as in Example 1).

[0150] Preparation process: In the preparation of rare earth oxide core-shell particles, primary modification (S01-S02) is carried out by mixing CeO2:La2O3 in a molar ratio of 2:1. Subsequent steps S1-S4 are the same as in Example 1.

[0151] Test performance data: CS 5.9%, CS after aging 5.3%, hardness 71 Shore A, tensile strength 19.3 MPa, elongation at break 363%, brittle temperature ≤ -55℃, efflorescence < 0.1 mg / cm² 2 The particles are evenly dispersed without agglomeration.

[0152] Example 8

[0153] Formulation parameters: The ionic liquid monomer is replaced with 1-carboxypropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt (CPMIm NTf2), and the dosage is 0.9 phr (the other components and dosages are the same as in Example 4).

[0154] Preparation process: In the preparation of rare earth oxide core-shell particles, the secondary modification (S03) is carried out by reacting CPMIm NTf2 with "Re-O-Si" core-shell particles, and the subsequent steps S1-S4 are the same as in Example 1.

[0155] Test performance data: CS 6.0%, CS after aging 5.4%, hardness 71 Shore A, tensile strength 19.2 MPa, elongation at break 364%, brittle temperature ≤ -55℃, efflorescence < 0.1 mg / cm² 2 The particles are evenly dispersed without agglomeration.

[0156] Example 9

[0157] Formula parameters: Same as in Example 4.

[0158] Preparation process: The primary vulcanization parameters were adjusted to 165℃×12 min (the secondary vulcanization parameters and steps S1-S3 are the same as in Example 1), and the remaining process conditions remained unchanged.

[0159] Test performance data: CS 6.1%, CS after aging 5.5%, hardness 71 Shore A, tensile strength 19.1 MPa, elongation at break 362%, brittle temperature ≤ -55℃, efflorescence < 0.1 mg / cm³ 2 The particles are evenly dispersed without agglomeration.

[0160] Example 10

[0161] Formulation parameters: Carbon black is replaced with N330 at a dosage of 50 phr (in Example 4, it is N550 at a dosage of 50 phr), and the other components and dosages are the same as in Example 4.

[0162] Preparation process: Steps S1-S4 are the same as in Example 1, and the materials are added according to the formula parameters of this example.

[0163] Test performance data: CS 6.2%, CS after aging 5.6%, hardness 72 Shore A, tensile strength 19.0 MPa, elongation at break 361%, brittle temperature ≤ -55℃, efflorescence < 0.1 mg / cm² 2 The particles are evenly dispersed without agglomeration.

[0164] Comparative Examples 1-5

[0165] Comparative Examples 1-5 all used the same vulcanization process (primary vulcanization at 170℃ for 10 min, followed by secondary vulcanization at 120℃ for 1.5 h + 160℃ for 3 h), with only the core components adjusted:

[0166] Comparative Example 1: Monomer without rare earth core-shell particles and ionic liquid. Properties: CS 13.5%, CS rebounded significantly to 20.1% after aging, hardness 73 Shore A, tensile strength 16.8 MPa, elongation at break 320%, brittle temperature -45℃, efflorescence <0.1 mg / cm³. 2 .

[0167] Comparative Example 2: Added unmodified CeO2 3.0 phr (non-ionic liquid monomer). Properties: CS 12.8%, 19.5% after aging, hardness 74 Shore A, tensile strength 17.2 MPa, elongation at break 315%, brittle temperature -46℃, efflorescence 0.8 mg / cm³. 2 Severe particle aggregation occurred.

[0168] Comparative Example 3: No BMI component, otherwise the same as Example 4. Performance: CS 10.2%, 15.3% after aging, hardness 76 Shore A, tensile strength 18.5 MPa, elongation at break 330%, brittle temperature -48℃, frosting amount <0.1 mg / cm², uniform particle dispersion but insufficient high-temperature performance.

[0169] Comparative Example 4: A common sulfur system (S 2.0 phr + CZ 1.5 phr + TMTD 0.5 phr) was used, without phenolic resin and BMI. Properties: CS 15.6%, 22.4% after aging, hardness 75 Shore A, tensile strength 16.5 MPa, elongation at break 305%, brittle temperature -47℃, and efflorescence amount 0.3 mg / cm². 2 .

[0170] Comparative Example 5: Replacing rare earth core-shell particles and ionic liquid monomers with HDMA 2.0 phr. Properties: CS 11.0%, 18.0% after aging, hardness 77 Shore A, tensile strength 18.3 MPa, elongation at break 325℃, brittle temperature -40℃, efflorescence <0.1 mg / cm². 2.

[0171] Performance tables corresponding to Examples 1-10:

[0172]

[0173] Performance tables corresponding to Comparative Examples 1-5:

[0174]

[0175] The core role of rare earth synergistic particles and IL: The CS values ​​of Comparative Example 1 (no rare earth + no IL) and Comparative Example 2 (unmodified rare earth + no IL) were significantly higher than those of Example 1 (≥12.8% vs 5.8%-7.8%), and the CS rebound after aging was large (≥19.5%), proving that the synergistic combination of "rare earth core-shell particles + IL" is the core to achieving low CS and anti-aging rebound.

[0176] Synergistic advantages of the ternary vulcanization system: The CS value and post-aging stability of Comparative Example 3 (without BMI) and Comparative Example 4 (ordinary sulfur system) are inferior to those of the example, proving that the crosslinking effect of the "sulfur-phenolic resin-BMI" ternary vulcanization system is significantly better than that of the single-component vulcanization system, which is the key to achieving performance breakthrough.

[0177] Adaptability of conventional vulcanization process: Examples 1-10 adopted the conventional flat plate + hot air oven vulcanization process, which still achieved the core performance of CS≤7.8% and retention rate ≥90% after aging, and there was no frost formation and the particles were evenly dispersed, proving that the conventional vulcanization process can be fully adapted to the formulation system of the present invention without relying on special equipment.

[0178] This application achieves comprehensive performance advantages with multiple performance enhancements: the embodiment is superior to the comparative example in terms of CS value, aging stability, hardness control, and low temperature resistance, breaking through the inherent contradiction of the prior art that "reducing CS will inevitably increase hardness and anti-aging will inevitably sacrifice low temperature performance", and filling a gap in the industry.

[0179] Figure 1 The results show that the "rare earth-organic" synergistic structure is uniformly dispersed in EPDM, ensuring the excellent performance of the modified EPDM rubber.

[0180] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A rare-earth modified EPDM rubber with low compression set, characterized in that, The raw materials include the following parts by weight: 100 parts EPDM, 1.5–4.0 parts rare earth oxide core-shell particles, 0.3–1.2 parts ionic liquid monomer, 0.3–0.8 parts sulfur, 1.0–2.5 parts phenolic resin crosslinking agent, 0.5–1.5 parts bismaleimide, 0.8–1.5 parts accelerator MBT, 0.3–0.6 parts accelerator TBzTD, 1.0–2.0 parts antioxidant 445, 15–25 parts paraffin oil, 40–60 parts carbon black, 1.0 part stearic acid, and 2.0 parts processing aid WB222; The rare earth oxide core-shell particles are obtained by in-situ surface modification of rare earth oxides with epoxy-containing trimethoxysilane and ionic liquid monomers, wherein the rare earth oxides are CeO2 and La2O3. The ionic liquid monomer is selected from 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt or 1-carboxypropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt.

2. The rare-earth modified EPDM rubber with low compression set according to claim 1, characterized in that, The EPDM contains 4.5 wt% ENB and has a Mooney viscosity of ML(1+4) at 125°C of 55 ± 5.

3. The rare-earth modified EPDM rubber with low compression set according to claim 1, characterized in that, The carbon black is at least one of N550 and N330.

4. A method for preparing a rare-earth modified EPDM rubber with low compression set according to any one of claims 1-3, characterized in that, Includes the following steps: S1 Masterbatch Preparation: Add 30 phr EPDM, rare earth oxide core-shell particles, ionic liquid monomer, antioxidant 445, and stearic acid to an internal mixer, set the temperature to 75-85℃ and the speed to 55-65 rpm, mix for 3-5 minutes, and then discharge the masterbatch. S2 Dilution and Mixing: Add the remaining 70 phr EPDM, carbon black, paraffin oil, phenolic resin crosslinking agent, BMI, sulfur, accelerator MBT, accelerator TBzTD, and processing aid WB222 to the masterbatch. Set the temperature to 65-75℃ and the speed to 45-55 rpm, and mix for 5-7 minutes. During this period, observe the state of the rubber compound every 2 minutes to ensure that there is no carbon black clumping. The discharge temperature should be strictly controlled to ≤100℃. S3 Thin pass-granulation: The compound from step S2 is fed into an open mill, the roll gap is adjusted to 0.4-0.6mm, thin pass 4-6 times, then the roll gap is adjusted to 1.8-2.2mm, and the sheet is produced; the sheet is fed into an underwater pelletizer, the cutter speed is set to 280-320rpm, the cooling water temperature is 18-22℃, and cylindrical rubber pellets with a diameter of 2.8-3.2mm and a length of 3.8-4.2mm are obtained; S4 two-stage vulcanization: S41 Primary Vulcanization: Place the rubber granules into the mold of the flat vulcanizing machine, set the temperature to 165-175℃ and the pressure to 9-11MPa, and hold for 8-12 minutes to achieve the shaping and initial cross-linking of the rubber compound. S42 Secondary Vulcanization: After primary vulcanization, the rubber compound is removed from the mold and transferred to an electric heating oven. It is first kept at 115-125℃ for 1.2-1.8 hours, and then heated to 155-165℃ for 2.5-3.5 hours. The hot air velocity in the oven is controlled at 0.6-1.0 m / s to ensure uniform temperature. S43 Cooling: After vulcanization, the rubber compound is naturally cooled to room temperature at a rate of ≤5℃ / min to avoid internal stress and obtain the final product.

5. The method for preparing a rare earth-modified EPDM rubber with low compression set according to claim 4, characterized in that, In step S1, the rotor torque of the internal mixer is stabilized at 80-100 N·m, and the temperature of the discharged masterbatch is ≤90℃.

6. The method for preparing a rare-earth modified EPDM rubber with low compression set according to claim 4, characterized in that, Preparation of the rare earth oxide core-shell particles: S01 Primary Modification: Mix rare earth oxides according to a set molar ratio, add trimethoxysilane containing epoxy groups (KH560), adjust the pH to 4.0-5.0, and react at 75-85℃ and 250-350rpm for 1.5-2.5h. SO2 washing and drying: The reaction solution is centrifuged at 7000-9000 rpm for 10-20 min, the precipitate is collected, washed with ethanol, and then dried at 55-65℃ and vacuum degree -0.10~-0.08MPa for 3-5 h to obtain "Re-O-Si" core-shell particles; S03 secondary modification: "Re-O-Si" core-shell particles are dispersed in an ethanol-water mixture, ionic liquid monomers are added, and the reaction is carried out at 20-30℃ and 150-250rpm for 0.8-1.2h. S04 Spray drying: The reaction solution is dried by a spray dryer to obtain powdered rare earth oxide core-shell particles.

7. The method for preparing a rare-earth modified EPDM rubber with low compression set according to claim 6, characterized in that, The rare earth oxides are CeO2 and La2O3; the CeO2 has a particle size of 50-80 nm and a purity of ≥99.9%; the La2O3 has a particle size of 50-80 nm and a purity of ≥99.9%; the molar ratio of CeO2 to La2O3 is 1:1-2:1; and the volume ratio of the ethanol-water mixture is 9:

1.

8. A method for preparing a rare-earth modified EPDM rubber with low compression set according to claim 4 or 6, characterized in that, The ionic liquid monomer is selected from 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt or 1-carboxypropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, with a purity ≥ 98%.

9. The method for preparing a rare-earth modified EPDM rubber with low compression set according to claim 6, characterized in that, The KH560 is added at a mass of 10%-14% of the total mass of rare earth oxides.

10. An application of a rare-earth modified EPDM rubber with low compression set, characterized in that, Rare earth modified EPDM rubber obtained by the preparation method described in any one of claims 1-3 or any one of claims 4-9 is used for fuel cell bipolar plate sealing, LNG cryogenic flange gaskets, spacecraft hatch O-rings, high-end building curtain wall seals, and rail transit vibration damping pads.

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