Nano-enhanced silane crosslinked chloroprene rubber composition as well as preparation method and application thereof

Abstract

The invention discloses a nano-reinforced silane crosslinked chloroprene rubber composition as well as a preparation method and application thereof, and belongs to the technical field of high-performance rubber materials. According to the technical scheme, the rubber composition comprises the following components in parts by weight: 100 parts of chloroprene rubber; 5 to 30 parts of a nanometer reinforcing phase; 2 to 10 parts of a silane cross-linking agent; 0.5 to 5 parts of an ionic liquid modifier; 3-15 parts of a bio-based plasticizer; 0.5-3 parts of a moisture absorbent; 0.1 to 1.5 parts of an organic tin catalyst; 1-4 parts of an anti-aging agent; and 1-5 parts of a processing aid. The vulcanized rubber prepared by the method has excellent heat aging resistance, ultralow compression set, enhanced mechanical property and excellent barrier property, completely avoids the heavy metal environmental protection problem of a traditional metal oxide vulcanization system, and can be widely applied to the high-end fields of aerospace sealing elements, deep sea cable sheaths, new energy automobile rubber tubes and the like.

Description

Technical Field

[0001] This invention relates to a nano-reinforced silane crosslinked chloroprene rubber composition, its preparation method, and its application, belonging to the field of high-performance rubber materials technology. Background Technology

[0002] Chloroprene rubber (CR), as one of the earliest industrialized synthetic rubbers, has been widely used in wire and cable, automotive, and aerospace industries due to its excellent oil resistance, weather resistance, flame retardancy, and mechanical properties. However, with the continuous improvement of material performance requirements in modern industry, especially in extreme environments such as deep-sea exploration, new energy vehicles, and nuclear energy utilization, the heat resistance, compression set resistance, and long service life of traditional chloroprene rubber are no longer sufficient to meet the demands.

[0003] Traditional chloroprene rubber vulcanization systems mainly use metal oxides (zinc oxide / magnesium oxide) in combination with sulfur or sulfur donors. This system has the following inherent defects: (1) Environmental problems: The release of zinc ions during vulcanization causes pollution to the environment, and the heavy metal content in the finished product is limited, making it difficult to meet the requirements of international environmental regulations such as RoHS and REACH; (2) Vulcanization reversion: Under high temperature or long-term over-sulfurization conditions, the cross-linked network dominated by polysulfide bonds is prone to breakage, resulting in a sharp decline in performance; (3) Large compression set: The cross-linked network formed by the traditional vulcanization system is uneven, and the stress relaxation is serious, affecting the long-term reliability of the seal.

[0004] Silane crosslinking technology has been successfully applied to polyethylene (silane crosslinked polyethylene cable material) and partially saturated rubber. The principle is that the alkoxy group of silane hydrolyzes in moisture to generate silanol, and the silanol condenses to form a stable -Si-O-Si-ether bond network. The crosslinking bond energy (~422 kJ / mol) is much higher than that of C-Sx-C bond (~250 kJ / mol), and it has excellent heat resistance and anti-aging properties. However, applying silane crosslinking technology directly to chloroprene rubber faces multiple challenges: (1) CR molecular chains are highly polar and contain chlorine atoms, resulting in poor compatibility with common silanes; (2) CR commonly uses acidic fillers (such as silica) to interfere with the silane hydrolysis-condensation reaction equilibrium; (3) Traditional silane crosslinking systems are difficult to form a uniform and high-density crosslinking network in CR.

[0005] In recent years, some studies have attempted to improve the dispersibility of carbon nanotubes in chloroprene rubber using ionic liquids, which has enhanced the mechanical and dielectric properties of the composite material to some extent. However, this technology is still limited to the traditional metal oxide / sulfur vulcanization system, where the crosslinking network remains essentially unchanged, and problems such as low crosslinking bond energy, poor heat aging resistance, large compression set, and environmental impact related to heavy metals persist. Therefore, how to fundamentally innovate the crosslinking network while improving filler dispersion is a key challenge that urgently needs to be addressed in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a nano-reinforced silane crosslinked chloroprene rubber composition, its preparation method, and its application. By constructing a dual network structure of "nano-reinforcement-chemical crosslinking", the overall performance of chloroprene rubber is comprehensively improved, meeting the stringent performance requirements of high-end application fields and solving the aforementioned problems in the background technology.

[0007] The technical solution of this invention is:

[0008] A nano-reinforced silane crosslinked chloroprene rubber composition, comprising the following components by weight: chloroprene rubber: 100 parts; nano-reinforcing phase: 5-30 parts; silane crosslinking agent: 2-10 parts; ionic liquid modifier: 0.5-5 parts; bio-based plasticizer: 3-15 parts; hygroscopic agent: 0.5-3 parts; organotin catalyst: 0.1-1.5 parts; antioxidant: 1-4 parts; processing aid: 1-5 parts.

[0009] Furthermore, the nano-reinforcing phase is surface-functionalized nano-silica and / or carboxylated carbon nanotubes, and the surface functionalization is performed in situ by silane coupling agents KH-550 or KH-590.

[0010] Furthermore, the nano-silica has a particle size of 10-50 nm and a specific surface area of ​​≥200 m² / g; the carboxylated carbon nanotubes have a diameter of 10-30 nm, a length of 1-10 μm, and a carboxyl content of 2-5 wt%.

[0011] Furthermore, the silane crosslinking agent is one or a mixture of two or more of γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, and bis-(γ-triethoxysilylpropyl)tetrasulfide.

[0012] Furthermore, the ionic liquid modifier is one or more of 1-butyl-3-methylimidazolium hexafluorophosphate, 1-allyl-3-methylimidazolium chloride, or 1-ethyl-3-methylimidazolium dicyandiamide. In the silane crosslinking system of the present invention, the ionic liquid simultaneously acts as a promoter for the silane hydrolysis-condensation reaction and an interfacial coupling agent between the nanofiller and the rubber matrix, participating in the construction of an integrated dual-network structure.

[0013] Furthermore, the bio-based plasticizer is one or more of epoxidized soybean oil, castor oil-based polyol ester, or cashew phenol-based plasticizer.

[0014] Further, the hygroscopic agent is calcium oxide, magnesium oxide, or molecular sieve powder; the organotin catalyst is dibutyltin dilaurate or dibutyltin diacetate; and the antioxidant is one or more of antioxidant RD, antioxidant 4010NA, or antioxidant MMBI.

[0015] A method for preparing a nano-reinforced silane crosslinked chloroprene rubber composition includes the following steps: (1) Nano-reinforcement phase pretreatment: Disperse nano-silica and / or carboxylated carbon nanotubes in an ethanol solution, add silane coupling agent KH-550 or KH-590, stir and react at 60-80°C for 2-4 hours, filter and dry to obtain a surface-functionalized nano-reinforcement phase; (2) Masterbatch preparation: Add chloroprene rubber raw rubber to a mixer, plasticize until the rubber is wrapped around the roller, then add the surface-functionalized nano-reinforcement phase, ionic liquid modifier, bio-based plasticizer, hygroscopic agent, antioxidant and processing aid in sequence, mix at 80-100°C for 10-15 minutes, and discharge the rubber to obtain the masterbatch. (3) Final mixing: Place the masterbatch back on the open mill, add silane crosslinking agent and organotin catalyst at 40-50°C, pass through 5-8 times, mix evenly and then sheet; (4) Vulcanization molding: Place the final mixed rubber in the mold and perform the first stage vulcanization on the flat vulcanizing machine at a temperature of 160-180°C, a pressure of 10-15MPa, and a time of positive vulcanization time t90; (5) Post-crosslinking treatment: Place the product after the first stage vulcanization in a constant temperature and humidity chamber at a temperature of 70-95°C, a relative humidity of 70-95%, and a time of 12-36 hours to complete the full hydrolysis and condensation of silane and the in-situ bonding of the nano-reinforcing phase.

[0016] Furthermore, the post-crosslinking treatment in step (5) adopts a gradient heating process: first, it is treated at 70°C for 6 hours, then heated to 85°C for 12 hours, and finally treated at 95°C for 6 hours.

[0017] The above-mentioned nano-reinforced silane crosslinked chloroprene rubber composition is used in the preparation of aerospace seals, deep-sea cable sheaths, high-pressure hoses for new energy vehicles, or radiation-resistant sealing products for nuclear power plants.

[0018] The positive effects of this invention:

[0019] (1) Excellent heat aging resistance

[0020] The constructed -Si-O-Si crosslinked network exhibits high bond energy and good thermal stability. After hot air aging at 150°C for 168 hours, the tensile strength retention rate is ≥85%, and the elongation at break retention rate is ≥70%, significantly better than traditional metal oxide sulfidation systems (which typically retain ≤60%). The addition of the nano-reinforcing phase further delays the propagation of microcracks during thermo-oxidative aging.

[0021] (2) Ultra-low compression set

[0022] The synergistic effect of the dual network structure results in high and uniform crosslinking density, effectively suppressing molecular chain slippage and stress relaxation. Under conditions of 100°C for 24 hours and 25% compression, the compression set can be as low as 15-20%, far lower than the 40-50% of traditional systems, making it particularly suitable for applications with extremely high requirements for sealing reliability.

[0023] (3) Enhanced mechanical properties

[0024] The uniform dispersion and chemical bonding of functionalized nanomaterials significantly improve their reinforcing efficiency. Compared to silane crosslinking systems without added nanomaterials, tensile strength is increased by 30-50%, tear strength by 40-60%, and abrasion resistance by over 50%.

[0025] (4) Excellent barrier properties

[0026] The barrier effect of the nanosheet structure and the dense chemical cross-linking network significantly improve the material's barrier performance against oxygen, water vapor, and oil media. The gas permeability coefficient is reduced by 40-60%, and the oil volume expansion rate (ASTM #3 oil, 100°C×70h) is ≤15%.

[0027] (5) Environmental protection and safety

[0028] Completely free of metal oxides such as zinc oxide and magnesium oxide, it contains no toxic heavy metals and complies with international environmental regulations such as RoHS and REACH. The use of bio-based plasticizers reduces petroleum resource consumption and lowers the carbon footprint.

[0029] (6) Multifunctional designability

[0030] By adjusting the types and ratios of nanomaterials, the structure of ionic liquids, and the type of silane, precise control can be achieved over the electrical properties (conductivity / insulation), thermal properties (thermal conductivity / insulation), and flame retardant properties of materials, meeting the customized needs of different application fields. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments:

[0032] A nano-reinforced silane crosslinked chloroprene rubber composition, comprising the following components by weight: chloroprene rubber: 100 parts; nano-reinforcing phase: 5-30 parts; silane crosslinking agent: 2-10 parts; ionic liquid modifier: 0.5-5 parts; bio-based plasticizer: 3-15 parts; hygroscopic agent: 0.5-3 parts; organotin catalyst: 0.1-1.5 parts; antioxidant: 1-4 parts; processing aid: 1-5 parts.

[0033] The nano-reinforcing phase is surface-functionalized nano-silica and / or carboxylated carbon nanotubes, and the surface functionalization is carried out in situ by silane coupling agents KH-550 or KH-590.

[0034] The nano-silica has a particle size of 10-50 nm and a specific surface area ≥200 m² / g; the carboxylated carbon nanotubes have a diameter of 8-35 nm, a length of 0.5-15 μm, and a carboxyl content of 1.5-6.0 wt%. Preferably, they have a diameter of 10-25 nm, a length of 1-8 μm, and a carboxyl content of 2.0-4.0 wt%.

[0035] The silane crosslinking agent is one or a mixture of two or more of γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, and bis-(γ-triethoxysilylpropyl)tetrasulfide.

[0036] The ionic liquid modifier is one or more of 1-butyl-3-methylimidazolium hexafluorophosphate, 1-allyl-3-methylimidazolium chloride, or 1-ethyl-3-methylimidazolium dicyandiamide.

[0037] The bio-based plasticizer is one or more of epoxidized soybean oil, castor oil-based polyol ester, or cashew phenol-based plasticizer.

[0038] The hygroscopic agent is calcium oxide, magnesium oxide, or molecular sieve powder; the organotin catalyst is dibutyltin dilaurate or dibutyltin diacetate; the antioxidant is one or more of antioxidant RD, antioxidant 4010NA, or antioxidant MMBI.

[0039] The core technical concept of this invention lies in constructing a dual network structure:

[0040] The first layer of network: silane chemical cross-linking network. A bifunctional silane (aminosilane KH-550 or mercaptosilane KH-590) is selected. The hydrolyzable alkoxy group at one end undergoes hydrolysis and condensation under moisture and a catalyst, forming a -Si-O-Si- chemical cross-linking bond. The organic functional group (-NH2 or -SH) at the other end chemically interacts with the chlorine atoms or double bonds on the chloroprene rubber molecular chain (nucleophilic substitution or free radical addition), "anchoring" the silane cross-linking network to the rubber molecular chain, forming a stable three-dimensional network structure.

[0041] The second layer of network: a nano-reinforcement network. Surface-functionalized nano-silica and / or carboxylated carbon nanotubes are used as the reinforcing phase. The nanomaterials are pretreated with a silane coupling agent, grafting organic functional groups compatible with the rubber matrix onto their surfaces. These functionalized nanomaterials are uniformly dispersed in the rubber matrix during the mixing process. Their surface active groups (-NH2, -SH, -COOH) can participate in the hydrolysis and condensation reactions of silanes, forming an integrated cross-linked network of "nanofiller-silane-rubber molecules," achieving a synergistic effect between the nano-reinforcing phase and the chemical cross-linked network.

[0042] Innovative Applications of Ionic Liquids: This invention introduces ionic liquids into silane crosslinked chloroprene rubber systems for the first time. Ionic liquids (such as [BMIM]PF6) have unique multiple functions in the silane crosslinking system of this invention: (1) as a dispersant for nanofillers, effectively preventing nanoparticle aggregation through ion-π interactions and electrostatic repulsion; (2) as a special promoter for silane hydrolysis and condensation, its anions and cations can form active intermediates with silane molecules, significantly accelerating the construction of the -Si-O- crosslinking network, an effect not present in traditional vulcanization systems; (3) as an interfacial coupling agent, improving the compatibility between fillers and rubber matrices and promoting the chemical bonding between nanofillers and crosslinking networks; (4) imparting certain ionic conductivity to the material, expanding its application in the field of antistatics.

[0043] Environmentally friendly design of bio-based plasticizers: Replacing traditional petroleum-based plasticizers (such as DOP) with bio-based plasticizers such as epoxidized soybean oil and castor oil-based polyol esters improves the environmental friendliness and sustainability of materials while ensuring processing performance. The epoxy groups in epoxidized soybean oil can also react with silanes or rubber molecules, participating in the construction of cross-linked networks.

[0044] Component selection and mechanism of action of this invention

[0045] (1) Chloroprene rubber (CR)

[0046] As the main material, it provides basic properties. Various Mooney viscosity CRs can be selected, with M-40 or M-50 types having a Mooney viscosity ML(1+4) of 40-60 at 100°C being preferred to ensure a good balance between processing performance and mechanical properties.

[0047] (2) Nano-reinforced phase

[0048] Surface-functionalized nano-silica: particle size 10-50 nm, specific surface area ≥200 m² / g. Surface modification is performed using KH-550 or KH-590 to graft amino or thiol groups onto the surface. The modified nano-silica not only provides reinforcement, but its surface active groups can also participate in silane crosslinking reactions, becoming multifunctional nodes in the crosslinking network.

[0049] Carboxylated carbon nanotubes: diameter 10-30 nm, length 1-10 μm, carboxyl content 2-5 wt%. Carboxyl groups can react with aminosilanes to form amide bonds, chemically bonding carbon nanotubes into the cross-linked network, significantly improving the material's modulus, electrical conductivity, and thermal stability.

[0050] Both can be used alone or in combination, with the preferred ratio being nano-silica:carbon nanotubes = 4:1~10:1 (by weight) to obtain the best overall performance.

[0051] (3) Silane crosslinking agent

[0052] γ-Aminopropyltriethoxysilane (KH-550): The amino group (-NH2) can undergo nucleophilic substitution with the chlorine atom on the CR chain to form a C-NH- chemical bond, grafting the silane molecule onto the rubber molecular chain. Simultaneously, the amino group can catalyze the hydrolysis of its own alkoxy group, achieving partial cross-linking without the need for an external catalyst.

[0053] γ-Mercaptopropyltrimethoxysilane (KH-590): The thiol group (-SH) can generate a thiol radical at the sulfidation temperature, which undergoes a radical addition reaction with the double bond on the CR molecular chain, thus achieving silane grafting. The thiol group can also react with the carboxyl group on the surface of carbon nanotubes to form a thioester bond, enhancing the filler-matrix interface bonding.

[0054] Bis-(γ-triethoxysilylpropyl)tetrasulfide (Si-69): Contains two triethoxysilane end groups and a tetrasulfide bond in the middle, which can participate in both silane hydrolysis condensation and sulfur sulfidation reactions. As a "bridging molecule", it connects the traditional sulfidation system and the silane crosslinking system, and is suitable for special application scenarios that require a dual crosslinking mechanism.

[0055] (4) Ionic liquid modifier

[0056] 1-Butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6): A hydrophobic ionic liquid with high thermal stability and good compatibility with CR. Its cations can form cation-π interactions with the π electron cloud of carbon nanotubes, while its anions form hydrogen bonds with the silanol groups on the surface of nano-silica, achieving synergistic dispersion of different nanomaterials.

[0057] 1-Allyl-3-methylimidazolium chloride ([AMIM]Cl): Contains an allyl group, which can participate in free radical reactions to chemically bond ionic liquids to the rubber network, preventing the migration and precipitation of ionic liquids.

[0058] 1-Ethyl-3-methylimidazolium dicyandiamide ([EMIM]DCA): A low-viscosity ionic liquid with good flowability, particularly suitable for improving low-temperature processing performance.

[0059] (5) Bio-based plasticizers

[0060] Epoxidized soybean oil (ESO): It is produced by epoxidation of soybean oil and has good compatibility with CR. The epoxy groups can react with carboxyl groups, amino groups, etc. during the sulfidation process and participate in network construction.

[0061] Castor oil-based polyol esters: These are produced by the esterification reaction of castor oil and polyols. Their molecular structure contains hydroxyl groups and long-chain alkyl groups, and they have both plasticizing and interfacial coupling functions.

[0062] Cashew nut phenolic plasticizer: Extracted from cashew nut shell liquid, it contains phenolic hydroxyl groups and unsaturated long chains, which can participate in free radical reactions, giving materials excellent heat resistance and anti-aging properties.

[0063] (6) Desiccant

[0064] Calcium oxide, magnesium oxide, or molecular sieve powders are used to precisely control the moisture content in the system. The appropriate amount of moisture is necessary for silane hydrolysis, but excessive moisture can lead to bubble formation and premature cross-linking during processing. The hygroscopic agent absorbs excess moisture during mixing and releases it slowly in the post-cross-linking stage, achieving "intelligent moisture control."

[0065] (7) Organotin catalysts

[0066] Dibutyltin dilaurate or dibutyltin diacetate can efficiently catalyze the hydrolysis and condensation reactions of silanes, reduce the post-crosslinking temperature, and shorten the processing time.

[0067] (8) Anti-aging agents

[0068] One or more of antioxidants RD (2,2,4-trimethyl-1,2-dihydroquinoline polymer), antioxidant 4010NA (N-isopropyl-N'-phenyl-p-phenylenediamine), or antioxidant MMBI (2-mercaptomethylbenzimidazole) synergistically protect the rubber network from thermo-oxidative aging damage.

[0069] (9) Processing aids

[0070] Stearic acid, polyethylene wax, etc., improve the processing fluidity and release properties of the rubber compound.

[0071] This invention develops a five-step preparation process to ensure uniform dispersion of nanomaterials and effective construction of a dual network:

[0072] Step 1: Pretreatment of Nano-Reinforced Phase

[0073] The nanomaterials were dispersed in an ethanol solution and surface grafting modification was performed by adding a silane coupling agent. The core of this step is: (1) introducing active groups that can react with the rubber matrix into the surface of the nanoparticles in advance; (2) reducing the surface energy of the nanoparticles through surface modification to prevent secondary agglomeration in the subsequent mixing process; (3) controlling the modification conditions (temperature 60-80°C, time 2-4 hours) to achieve monolayer grafting and avoid excessive modification leading to agglomeration of nanoparticles.

[0074] Step 2: Masterbatch Preparation

[0075] In a Banbury mixer, chloroprene rubber is blended with functionalized nanomaterials, ionic liquids, bio-based plasticizers, and hygroscopic agents. The timing of the addition of the ionic liquid is crucial: the ionic liquid is premixed with the rubber before the nanomaterials are added. The high polarity of the ionic liquid breaks up the entanglement of the rubber molecular chains, creating conditions for the uniform dispersion of the nanomaterials. The masterbatch preparation temperature is controlled at 80-100°C to ensure thorough mixing of all components while preventing premature hydrolysis of silanes.

[0076] Step Three: Final Refinement

[0077] Add the silane crosslinking agent and organotin catalyst at a low temperature (40-50°C) on an open mill. The low temperature prevents premature hydrolysis and crosslinking (scorching) of the silane during processing, ensuring the processing safety of the rubber compound. Pass through a thin pass 5-8 times to ensure uniform distribution of trace components.

[0078] Step 4: Vulcanization molding

[0079] The first stage of hot-press vulcanization is carried out on a flat vulcanizing machine. The main functions of this stage are: (1) to make the rubber material flow and fill the mold cavity to form the shape of the product; (2) to initiate the initial reaction between silane and rubber molecular chains (amino nucleophilic substitution or mercapto radical addition); (3) some silane begins to hydrolyze and condense to form a preliminary cross-linked structure, so that the product has sufficient strength after demolding.

[0080] Step 5: Post-crosslinking treatment

[0081] The product after the first stage of vulcanization is placed in a constant temperature and humidity chamber for gradient temperature and humidity treatment. This is a key step in building a complete cross-linking network.

[0082] Low temperature range (70°C): Water molecules slowly penetrate into the interior of the product, activating the organotin catalyst, and silane begins to hydrolyze to generate silanol;

[0083] In the intermediate temperature range (85°C): the concentration of silanol reaches its peak, the condensation reaction accelerates, and a large number of -Si-O-Si- crosslinks are formed;

[0084] High-temperature section (95°C): Residual silanol undergoes further condensation, while simultaneously promoting the chemical bonding between the surface-active groups of the nanomaterials and the cross-linked network, forming an integrated "nanofiller-cross-linked network" structure. The gradient heating process avoids structural inhomogeneity caused by excessively rapid reaction rates at a single temperature, ensuring the formation of a dense and uniform dual-network structure. Detailed Implementation

[0085] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0086] Examples 1-5 and Comparative Examples 1-3

[0087] The formula is shown in Table 1 (unit: parts by weight).

[0088] Comparative Example 1: A traditional metal oxide sulfidation system (zinc oxide / magnesium oxide), without nanomaterials or silane crosslinking. Comparative Example 2: A silane crosslinking system (same formulation as Example 1), but without the nano-reinforcing phase and ionic liquid. Comparative Example 3: A nano-reinforced silane crosslinking system, but the nanomaterials were not surface-functionalized. Examples 1-5: The nano-reinforced silane crosslinking system of the present invention, with variations in the type of nanomaterial, the type of ionic liquid, and the silane ratio.

[0089] Table 1: Formula Table

[0090]

[0091] Preparation process:

[0092] Comparative Example 1:

[0093] First stage of compounding: After CR plasticizing, add silica, zinc oxide, magnesium oxide, antioxidant, and stearic acid. Mix thoroughly, then sheet and let stand for 6 hours. Second stage of compounding: Add accelerator NA-22. Vulcanization: 170°C × 90°C. No post-treatment.

[0094] Comparative Example 2:

[0095] First stage of compounding: After CR plasticizing, add silica, calcium oxide, epoxidized soybean oil, antioxidant, and stearic acid. Mix thoroughly, then sheet and let stand for 6 hours. Second stage of compounding (45°C): Add KH-550 and dibutyltin dilaurate. Vulcanization: 170°C × 90°C. Post-treatment: 80°C × 80%RH × 12h.

[0096] Comparative Example 3:

[0097] Similar to Comparative Example 2, but the silica was not surface-functionalized.

[0098] Examples 1-5:

[0099] (1) Pretreatment of nano-reinforced phase: Disperse nano-SiO2 and / or carbon nanotubes in ethanol, add KH-550 and / or KH-590 (5% relative to the mass of nanomaterials), stir at 70°C for 3 hours, filter, and vacuum dry at 60°C for 12 hours.

[0100] (2) Preparation of masterbatch: In the internal mixer, after plasticizing with CR for 2 minutes, add ionic liquid and mix for 3 minutes; add functionalized nanomaterials, epoxidized soybean oil, calcium oxide, antioxidant and stearic acid in sequence, mix at 90°C for 12 minutes, remove glue and let stand for 10 hours.

[0101] (3) Final refining: The masterbatch is passed through a two-roll mill at 45°C, and silane crosslinking agent and dibutyltin dilaurate are added. The mixture is passed through 6 times and then sheeted.

[0102] (4) Vulcanization: 170°C × 90°C, pressure 12MPa.

[0103] (5) Post-crosslinking: Gradient temperature rise process: 70°C×6h → 85°C×12h → 95°C×6h, relative humidity 85%. Performance testing:

[0104] The vulcanized test pieces were tested according to national standards, and the results are shown in Table 2.

[0105] Table 2: Performance Test Results

[0106]

[0107] Results analysis:

[0108] (1) Significant nano-enhancement effect

[0109] As shown in Table 2, the mechanical properties of Examples 1-5 of this invention are comprehensively superior to those of the comparative examples. Example 2 (functionalized nano-SiO2 + carbon nanotube composite) achieved a tensile strength of 26.5 MPa, a 43% increase compared to Comparative Example 1 and a 54% increase compared to Comparative Example 2 (without nanomaterials); its tear strength was increased by more than 60%. This indicates that the dual network structure formed by the functionalized nanomaterials and the silane crosslinking network produces a significant synergistic enhancement effect.

[0110] (2) The necessity of surface functionalization

[0111] Comparing Example 1 and Comparative Example 3: Comparative Example 3 used unmodified nano-SiO2. Although the formulation was the same, the tensile strength was only 16.5 MPa, far lower than the 22.8 MPa of Example 1. This shows that surface functionalization of nanomaterials is a prerequisite for them to exert their reinforcing effect. Unmodified nanomaterials have poor dispersion and weak interfacial bonding in the rubber matrix, and may even become stress concentration points, leading to a decline in performance.

[0112] (3) Synergistic enhancement of carbon nanotubes

[0113] Example 2 (with 5 parts carbon nanotubes) showed a 16% increase in tensile strength, an 18% increase in tear strength, and a 33% increase in abrasion resistance compared to Example 1 (nano SiO2 only). The one-dimensional structure and high aspect ratio of carbon nanotubes form a "fiber-reinforced" network in the rubber matrix, which complements the "spherical reinforcement" of nano SiO2. At the same time, the high conductivity of carbon nanotubes also makes it possible for the material to have antistatic properties.

[0114] (4) The multifunctional role of ionic liquids

[0115] Example 3 increased the amount of ionic liquid to 3 parts; although the total amount of nanomaterials remained the same, the crosslinking density increased to 4.1 × 10⁻⁶. 4 The compression set was further reduced to mol / cm³. Ionic liquids not only promoted the dispersion of nanomaterials, but their anions and cations also participated in the catalytic process of silane hydrolysis and condensation, improving crosslinking efficiency. Example 4 used allyl-containing [AMIM]Cl, whose ability to participate in free radical reactions made the crosslinked network more stable and exhibited excellent heat aging resistance.

[0116] (5) Synergistic effect of silane complex

[0117] Example 5 uses a blend of KH-550 and KH-590, achieving optimal performance: tensile strength 27.2 MPa, compression set 16%, and oxygen permeability coefficient 2.8 × 10⁻¹. 7 m²·s⁻¹·Pa⁻¹. Analysis suggests that the amino group of KH-550 bonds to the CR molecular chain through nucleophilic substitution, while the thiol group of KH-590 bonds to the CR molecular chain through free radical addition. The synergistic effect of these two different reaction mechanisms forms a more complete and uniform cross-linked network.

[0118] (6) Excellent heat aging resistance

[0119] Under harsh aging conditions of 150°C for 168 hours, all examples exhibited tensile strength retention exceeding 90% and elongation at break retention exceeding 84%, significantly better than Comparative Example 1's 68% and 52%, respectively. This demonstrates that the -Si-O-Si crosslinked network and nano-reinforced network possess excellent resistance to thermo-oxidative aging. The physical shielding effect of the nanomaterials delays the diffusion of oxygen into the material interior, while the chemically bonded network structure inhibits chain breakage during thermal degradation.

[0120] (7) Compression permanent deformation is significantly reduced

[0121] Example 5, under high-temperature compression conditions of 125°C for 70 hours, exhibited a compression set of only 24%, compared to 68% in Comparative Example 1. This performance advantage is crucial for high-temperature sealing applications, meaning that seals made with the material of this invention can maintain reliable sealing performance even under long-term high-temperature service conditions.

[0122] (8) Overall performance adjustability

[0123] By adjusting the proportions of nanomaterials (Examples 1-3) and the types of silanes (Examples 4-5), different combinations of properties can be obtained: high tensile strength (Example 2), high tear strength (Example 2), low compression set (Example 5), high barrier properties (Example 5), and good processing flowability (Example 3). This designability of properties allows the materials of the present invention to meet the customized needs of different application fields.

[0124] Application Example 1: High-Temperature Resistant Seals for Aerospace Applications

[0125] The O-ring prepared using the formulation in Example 5, after immersion in aviation hydraulic oil (Skydrol LD-4) (135°C × 72h), showed a volume change rate of only +8.2% and a compression set of 21% (135°C × 24h), meeting the requirements of the aerospace seal standard HB 7483-2014. No cracks were observed during the -55°C low-temperature brittleness test, demonstrating wide temperature range adaptability.

[0126] Application Example 2: Deep-sea cable sheath

[0127] The cable sheath material prepared using the formulation in Example 2 was tested in a simulated deep-sea environment (pressure 60 MPa, temperature 4°C, pressure holding for 30 days). The material had a water absorption rate of 0.32%, a volume resistivity change of <5%, and a tensile strength retention rate of 96%, meeting the requirements for long-term service of deep-sea cables.

[0128] Application Example 3: High-pressure hoses for new energy vehicles

[0129] The cooling water pipe prepared using the formulation of Example 5 underwent 1 million cycles of dynamic pulse testing (0-0.5MPa, frequency 1Hz) in a coolant at 135°C, without any leakage or bulging. Its service life is more than 3 times longer than that of traditional neoprene rubber hoses.

[0130] Application Example 4: Radiation-resistant seals for nuclear power plants

[0131] The seal prepared using the formulation of Example 3, after being irradiated with gamma rays (total dose 500 kGy, dose rate 10 kGy / h), retained 88% of its tensile strength and increased its compression set (100°C × 24h) from 20% before irradiation to 24%, still meeting the requirements for use in nuclear power plant seals and demonstrating excellent radiation resistance.

[0132] This invention innovatively constructs a dual network structure of "nano-reinforced silane crosslinking" and introduces ionic liquids and bio-based plasticizers, successfully developing a chloroprene rubber material with superior comprehensive performance. This material significantly outperforms traditional chloroprene rubber in terms of mechanical properties, heat aging resistance, compression set, and barrier properties, and is completely free of heavy metals, aligning with the trend of green and environmentally friendly development. Its designability and excellent comprehensive performance make it a promising candidate for applications in high-end fields such as aerospace, deep-sea exploration, new energy vehicles, and nuclear energy.

[0133] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A nano-reinforced silane crosslinked chloroprene rubber composition, characterized in that: By weight, it comprises the following components: chloroprene rubber: 100 parts; nano-reinforcing phase: 5-30 parts; silane crosslinking agent: 2-10 parts; ionic liquid modifier: 0.5-5 parts; bio-based plasticizer: 3-15 parts; hygroscopic agent: 0.5-3 parts; organotin catalyst: 0.1-1.5 parts; antioxidant: 1-4 parts; processing aid: 1-5 parts.

2. The nano-reinforced silane crosslinked chloroprene rubber composition according to claim 1, characterized in that: The nano-reinforcing phase is surface-functionalized nano-silica and / or carboxylated carbon nanotubes, and the surface functionalization is carried out in situ by silane coupling agents KH-550 or KH-590.

3. The multidimensional reinforced silane crosslinked chlorosulfonated polyethylene nanocomposite material according to claim 2, characterized in that: The nano-silica has a particle size of 10-50 nm and a specific surface area of ​​≥200 m² / g; the carboxylated carbon nanotubes have a diameter of 10-30 nm, a length of 1-10 μm, and a carboxyl content of 2-5 wt%.

4. A nano-reinforced silane crosslinked chloroprene rubber composition according to claim 1 or 3, characterized in that: The silane crosslinking agent is one or a mixture of two or more of γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, and bis-(γ-triethoxysilylpropyl)tetrasulfide.

5. A nano-reinforced silane crosslinked chloroprene rubber composition according to claim 1 or 3, characterized in that: The ionic liquid modifier is one or more of 1-butyl-3-methylimidazolium hexafluorophosphate, 1-allyl-3-methylimidazolium chloride, or 1-ethyl-3-methylimidazolium dicyandiamide.

6. A nano-reinforced silane crosslinked chloroprene rubber composition according to claim 1 or 3, characterized in that: The bio-based plasticizer is one or more of epoxidized soybean oil, castor oil-based polyol ester, or cashew phenol-based plasticizer.

7. A nano-reinforced silane crosslinked chloroprene rubber composition according to claim 1 or 3, characterized in that: The hygroscopic agent is calcium oxide, magnesium oxide, or molecular sieve powder; the organotin catalyst is dibutyltin dilaurate or dibutyltin diacetate; the antioxidant is one or more of antioxidant RD, antioxidant 4010NA, or antioxidant MMBI.

8. A method for preparing a nano-reinforced silane crosslinked chloroprene rubber composition as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Pretreatment of nano-reinforced phase: Disperse nano-silica and / or carboxylated carbon nanotubes in ethanol solution, add silane coupling agent KH-550 or KH-590, stir and react at 60-80°C for 2-4 hours, filter and dry to obtain surface functionalized nano-reinforced phase; (2) Preparation of masterbatch: In a mixer, add chloroprene rubber raw rubber, plasticize until it wraps around the roller, then add surface functionalized nano-reinforcing phase, ionic liquid modifier, bio-based plasticizer, hygroscopic agent, antioxidant and processing aid in sequence, mix at 80-100°C for 10-15 minutes, discharge the rubber to obtain masterbatch, and let it stand for 8-12 hours; (3) Final mixing: Place the masterbatch back on the open mill, add silane crosslinking agent and organotin catalyst at 40-50°C, pass through the mill 5-8 times, mix evenly and then sheet; (4) Vulcanization molding: Place the final rubber in the mold and perform the first stage of vulcanization on a flat vulcanizing machine. The temperature is 160-180°C, the pressure is 10-15MPa, and the time is the positive vulcanization time t90. (5) Post-crosslinking treatment: Place the product after the first stage of vulcanization in a constant temperature and humidity chamber at a temperature of 70-95°C and a relative humidity of 70-95% for 12-36 hours to complete the full hydrolysis and condensation of silane and the in-situ bonding of the nano-reinforcing phase.

9. The method for preparing the nano-reinforced silane crosslinked chloroprene rubber composition according to claim 8, characterized in that: The post-crosslinking treatment in step (5) adopts a gradient heating process: first, it is treated at 70°C for 6 hours, then heated to 85°C for 12 hours, and finally treated at 95°C for 6 hours.

10. The application of the nano-reinforced silane crosslinked chloroprene rubber composition according to any one of claims 1-7 in the preparation of aerospace seals, deep-sea cable sheaths, high-pressure hoses for new energy vehicles, or radiation-resistant sealing products for nuclear power plants.

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