Salt-fog-aging-resistant marine halogen-free fireproof sealing material and preparation method thereof

Abstract

The application discloses a salt-mist-aging-resistant marine halogen-free fireproof sealing material and a preparation method thereof, and relates to the technical field of high polymer materials. The sealing material comprises A component and B component. The A component comprises vinyl-terminated polydimethylsiloxane, silicone resin, hydrophobic fumed silica, fireproof salt-mist-resistant filler, coupling agent, thixotropic agent, plasticizer and pigment. The B component comprises hydrogen-containing silicone oil crosslinking agent, alkyne alcohol inhibitor and platinum catalyst. The A component and the B component are mixed and cured for use. The obtained sealing material has good fire-retardant and smoke-suppressing performance, carbon-forming performance, flexibility, bonding performance and salt-mist-aging resistance, and is suitable for fireproof sealing of joints, pipeline through holes, cable through parts and cabin wall connecting parts in ships, marine engineering equipment and offshore facilities.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a halogen-free fireproof sealing material for marine applications that is resistant to salt spray aging and its preparation method. Background Technology

[0002] Ships, marine engineering equipment, and offshore facilities operate long-term in complex environments characterized by high humidity, high salt spray, strong ultraviolet radiation, fluctuating temperatures, and the presence of oil contaminants. Their hull joints, pipeline penetrations, cable penetrations, and bulkhead connections typically require sealing materials for waterproofing, moisture protection, corrosion resistance, and flame retardancy. These sealing materials, used in these environments, must not only possess excellent flexibility, adhesion, and sealing properties, but also maintain stable structural integrity and safety performance under long-term salt spray corrosion, humid heat aging, and fire conditions.

[0003] Existing marine sealing materials mainly include polyurethane, acrylic, epoxy, and silicone materials. Among them, silicone sealing materials have good application prospects in the shipbuilding and marine engineering fields due to their good weather resistance, high and low temperature resistance, and electrical insulation properties. However, ordinary silicone sealing materials have limited flame-retardant and char-forming capabilities. During heating or combustion, they easily form a loosely structured char layer, which is difficult to effectively block the transfer of heat, oxygen, and combustible volatiles. As a result, their fireproof and heat-insulating performance still cannot meet the requirements of high-grade marine fireproof sealing.

[0004] To improve the flame retardant properties of sealing materials, existing technologies typically modify them by adding halogenated flame retardants, metal hydroxides, phosphorus-nitrogen flame retardants, intumescent flame retardants, or inorganic refractory fillers. While halogenated flame retardants offer high flame retardant efficiency, they readily release corrosive and toxic fumes during combustion, failing to meet the low-smoke, low-toxicity, and environmental safety requirements of ships and confined spaces. Large additions of halogen-free flame retardant fillers such as metal hydroxides can lead to increased material viscosity, decreased processing performance, and potentially weakened flexibility, adhesion, and mechanical properties of the sealing material. Although common phosphorus-nitrogen or intumescent flame retardant fillers can improve char formation, their strong hydrophilicity makes them prone to moisture absorption, migration, or interfacial debonding in marine salt spray environments, resulting in decreased salt spray resistance.

[0005] Furthermore, marine sealing materials are subjected to the synergistic effects of chloride ions, moisture, and oxygen in the marine environment for extended periods. This can lead to problems such as hydrolysis, swelling, filler precipitation, or microcrack propagation at the material interface, resulting in a decline in sealing performance, fire resistance, and mechanical properties. While some existing halogen-free flame-retardant sealing materials can achieve a certain degree of flame retardancy in the initial stage, they suffer from insufficient compatibility and interfacial bonding between the flame-retardant filler and the silicone matrix. Additionally, the filler surface exhibits poor hydrophobicity and salt spray resistance, leading to reduced flame-retardant efficiency, sealing layer cracking, and decreased bond strength after long-term salt spray aging.

[0006] Therefore, there is an urgent need to provide a halogen-free fireproof sealing material suitable for marine and marine engineering environments, which can maintain good processability, curing properties, flexibility and sealing properties, while also having excellent fire-retardant properties, salt spray aging resistance and long-term service stability. Summary of the Invention

[0007] In view of this, the present invention provides a halogen-free fireproof sealing material for marine applications that is resistant to salt spray aging and its preparation method. The present invention effectively solves the problems of insufficient salt spray aging resistance, easy moisture absorption and migration of flame-retardant fillers, poor bonding between fillers and matrix, and decay of fireproof sealing performance after long-term service by using an organosilicon matrix system and fireproof and salt spray resistant fillers in synergy.

[0008] To better solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, a halogen-free fireproof sealing material for marine applications that is resistant to salt spray aging includes component A and component B, wherein the mass ratio of component A to component B is 100:(5-15). Component A, by weight, comprises 65-120 parts of vinyl-terminated polydimethylsiloxane, 5-20 parts of silicone resin, 8-25 parts of hydrophobic fumed silica, 8-25 parts of fire-retardant and salt spray resistant filler, 0.5-5 parts of coupling agent, 0-3 parts of thixotropic agent, 0-10 parts of plasticizer, and 0-5 parts of pigment. Component B, by weight, comprises: 2-10 parts of hydrogen-containing silicone oil crosslinking agent, 0.01-0.3 parts of alkynol inhibitor, and 0.1-1.8 parts of platinum catalyst.

[0009] The fire-retardant and salt spray-resistant filler has a multi-layer structure consisting of a core, an adhesive layer, a catalytic layer, and a hydrophobic shell. The core is a tannic acid-melamine salt or a tannic acid-phytic acid-melamine ternary supramolecular salt. The adhesive layer is a polydopamine layer. The catalytic layer is a multi-metallic organic framework, metal hydroxide, metal oxide, or a composite layer thereof containing Co, Ni, and Ce. The hydrophobic shell is a fluorosiloxane-silica-reactive silane cocondensation layer. The hydrophobic shell contains at least one reactive group selected from vinyl, epoxy, methacryloxy, or hydrosilyl groups.

[0010] Preferably, the tannic acid-melamine salt is formed by tannic acid and melamine through hydrogen bonding and ionic association, and the molar ratio of tannic acid to melamine is 1:(0.5-5).

[0011] Preferably, the tannic acid-phytic acid-melamine ternary supramolecular salt is formed by tannic acid, phytic acid and melamine through hydrogen bonding, ion association and phosphorus-nitrogen synergistic carbonization; the molar ratio of tannic acid, phytic acid and melamine is 1:(0.05-1.5):(0.5-5).

[0012] Preferably, the molar ratio of Co, Ni, and Ce in the catalyst layer is 1:(0.1-1.5):(0.02-0.8); the Ce is in the form of Ce... 3+ Ce 4+ or Ce 3+ / Ce 4+ Mixed valence states exist.

[0013] Preferably, the hydrophobic shell is formed by co-hydrolysis and condensation of tetraethoxysilane, fluorinated silane, vinyl silane, and epoxy silane; the fluorinated silane includes one or more of perfluorooctyltriethoxysilane, perfluorodecyltrimethoxysilane, and tridecafluorooctyltriethoxysilane; the vinyl silane includes one or more of vinyltriethoxysilane, vinyltrimethoxysilane, and methacryloxypropyltrimethoxysilane; and the epoxy silane includes one or more of γ-glycidoxypropyltrimethoxysilane and γ-glycidoxypropyltriethoxysilane.

[0014] Preferably, the D50 particle size of the fire-retardant and salt spray resistant filler is 0.3-10 μm; the thickness of the polydopamine layer is 5-100 nm; the thickness of the catalyst layer is 10-300 nm; and the thickness of the hydrophobic shell layer is 10-500 nm.

[0015] Preferably, the organosilicon resin is a phenyl silicone resin, MQ silicone resin, or a combination thereof.

[0016] Preferably, the coupling agent includes one or more of titanate coupling agents and borate coupling agents; the alkynol inhibitor includes one or more of 1-ethynylcyclohexanol, 3-methyl-1-butyn-3-ol, and 3,5-dimethyl-1-hexyn-3-ol; the thixotropic agent includes one of hydrogenated castor oil, polyamide wax, and organobentonite; and the plasticizer includes one of dimethyl silicone oil and methylphenyl silicone oil.

[0017] Secondly, a method for preparing a salt spray resistant, halogen-free fireproof sealing material for marine applications includes the following steps: (1) Dissolve melamine in hot water at 80-95℃, adjust the pH of tannic acid solution or tannic acid-phytic acid mixed solution to 5.0-7.0 and add it to the melamine solution to react, filter, wash and dry to obtain the kernel; (2) Disperse the kernel obtained in step (1) in Tris buffer, add dopamine hydrochloride, and react for 12-24 h at pH 8.0-8.8 to obtain polydopamine-coated kernel; (3) The polydopamine-coated core obtained in step (2) is dispersed in a solution containing 2-methylimidazole, and cobalt salt, nickel salt and cerium salt are added to carry out an in-situ growth reaction to obtain particles with a multi-metal catalytic layer. (4) Disperse the particles obtained in step (3) in an ethanol / water mixed solution, add tetraethoxysilane, fluorinated silane, vinyl silane and epoxy silane, co-hydrolyze and condense under alkaline conditions, and dry to obtain fireproof and salt spray resistant filler. (5) Mix and degas the vinyl-terminated polydimethylsiloxane, organosilicon resin, hydrophobic fumed silica, fire-retardant and salt spray resistant filler obtained in step (4), coupling agent, thixotropic agent, plasticizer and pigment to obtain component A; (6) Mix the hydrogen-containing silicone oil crosslinking agent, platinum catalyst, and alkynol inhibitor evenly to obtain component B.

[0018] Preferably, in step (1), the tannic acid solution or tannic acid-phytic acid mixed solution is added at a time of 15-60 min; the reaction temperature is 80-90℃ and the reaction time is 2-4 h.

[0019] Preferably, in step (3), the concentration of the 2-methylimidazole solution is 0.2-0.4 mol / L, and the molar ratio of 2-methylimidazole to the total metal ions of Co, Ni, and Ce is (6:1)-(15:1).

[0020] Preferably, in step (3), the cobalt salt, nickel salt and cerium salt are selected from their nitrates, chlorides, acetates or sulfates, respectively, and the in-situ growth temperature is 20-60℃ and the time is 6-24h.

[0021] Preferably, in step (4), the volume ratio of ethanol to water in the ethanol / water mixed solution is 1:(0.05-1); the alkaline condition is pH 8.0-11.0; the co-hydrolysis condensation reaction temperature is 20-60℃ and the time is 4-24h.

[0022] Preferably, in step (5), the mixing pressure is -0.06MPa to -0.10MPa, and the mixing time is 20-120min.

[0023] When using, mix component A and component B at a mass ratio of 100:(5-15) and cure to obtain the sealing material; the curing temperature is 20-120℃ and the curing time is 0.5-24h.

[0024] Compared with the prior art, the present invention has at least the following advantages: This invention uses vinyl-terminated polydimethylsiloxane and silicone resin as the silicone matrix system, and adds hydrophobic fumed silica and fire-retardant salt spray resistant fillers, giving the resulting sealing material excellent flexibility, weather resistance, media resistance, and sealing stability. The silicone resin helps improve the film-forming strength and thermal stability of the material, making the sealing material more suitable for long-term service environments in ships and marine engineering.

[0025] The fire-retardant and salt-spray-resistant filler used in this invention has a multi-layered composite structure consisting of a core, an adhesive layer, a catalytic layer, and a hydrophobic shell. The core, composed of a tannic acid-melamine salt or a tannic acid-phytic acid-melamine ternary supramolecular salt, exerts a synergistic flame-retardant effect with phosphorus and nitrogen and promotes char formation. The polydopamine adhesive layer improves the load stability of subsequent functional layers and enhances the interfacial bonding between the filler and the organosilicon matrix. The multi-metallic catalytic layer containing Co, Ni, and Ce promotes the densification and ceramization of the char layer during heating or combustion, improving the strength and barrier properties of the residual char layer. The hydrophobic shell layer reduces the hygroscopicity of the filler surface, improving the dispersibility and salt-spray resistance of the filler in the organosilicon matrix. The addition of this fire-retardant and salt-spray-resistant filler enables the sealing material to form a more continuous, dense, and stable protective char layer under flame conditions, thereby improving its fire-retardant performance.

[0026] The outer layer of the fire-retardant and salt spray resistant filler of the present invention is a hydrophobic shell layer of fluorinated siloxane-silica-reactive silane co-condensation. This hydrophobic shell layer can not only significantly improve the hydrophobicity and salt spray erosion resistance of the filler, but also contains reactive groups such as vinyl, epoxy, methacryloxy, or hydrosilyl groups. These reactive groups can form physical entanglement or chemical bonding with the organosilicon matrix during the material curing or interfacial bonding process, reducing filler agglomeration, migration and interfacial debonding, and improving the retention rate of mechanical properties, adhesion stability and flame retardant properties of the sealing material after salt spray aging.

[0027] Furthermore, this invention does not use halogenated flame retardants, which avoids the problem of traditional halogenated flame retardant systems generating a large amount of toxic and corrosive smoke during combustion, and better meets the requirements of ships, offshore platforms and enclosed compartments for low smoke, low toxicity and environmental safety. Detailed Implementation

[0028] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0029] The raw material parameters and sources in the following examples are as follows. Unless otherwise specified, other raw materials are all commercially available products.

[0030] Vinyl-terminated polydimethylsiloxane: viscosity 10000 mPa·s, Hubei Handafei Biotechnology Co., Ltd.; MQ silicone resin: DY-VMQ101, Shandong Dayi Chemical Co., Ltd.; Phenyl silicone resin: Auspisil 8537, Suzhou Qitian New Materials Co., Ltd.; Methylphenyl silicone oil: Benzyl silicone oil 274, Shanghai Hengyuan Biotechnology Development Co., Ltd.; Dimethyl silicone oil: PMX200, Dow (Zhangjiagang) Investment Co., Ltd.; Hydrophobic fumed silica: AEROSIL R8200, Evonik Degussa; Pigment: Rutile titanium dioxide, grade R996, Xiangyang Longmang Titanium Industry Co., Ltd.; Hydrogen-containing silicone oil crosslinking agent: MSD-D212, Qingdao Meiside Organosilicon Co., Ltd.; Polyamide wax: Arkema SL, Arkema Shanghai Chemical Co., Ltd.; Organic bentonite: Bentone 38, Haiming Sideqian.

[0031] Example 1

[0032] A halogen-free fireproof sealing material for marine applications that is resistant to salt spray aging, comprising component A and component B, wherein the mass ratio of component A to component B is 100:10; Its preparation method includes the following steps: (1) Weigh out melamine and tannic acid in a molar ratio of 2:1; add melamine to deionized water, heat to 85°C and stir to fully dissolve melamine to obtain a melamine solution with a concentration of 0.10 mol / L; dissolve tannic acid in deionized water and adjust the pH to 6.0 to obtain a tannic acid solution with a concentration of 0.05 mol / L; add the tannic acid solution dropwise to the melamine solution within 30 min; after the addition is complete, continue the reaction at 85°C for 3 h; after the reaction is complete, filter the obtained product, wash it and dry it at 60°C to obtain the kernel; (2) By weight, 100 parts of the core were dispersed in 1000 parts of Tris buffer at pH 8.5, and 10 parts of dopamine hydrochloride were added. The mixture was stirred at room temperature for 18 h. After the reaction was completed, the core was separated by centrifugation, and the precipitate was washed and dried to obtain polydopamine-coated core. (3) By weight, 100 parts of polydopamine-coated core were dispersed in 1200 parts of 0.30 mol / L 2-methylimidazole solution. After stirring evenly, cobalt nitrate, nickel nitrate and cerium nitrate were added. The molar ratio of Co, Ni and Ce was 1:0.5:0.1, and the molar ratio of 2-methylimidazole to the total metal ions of Co, Ni and Ce was 10:1. The reaction system was reacted at 40℃ for 12 h. After the reaction was completed, the mixture was centrifuged, the precipitate was washed and dried to obtain particles with a multi-metal catalyst layer. (4) By weight, 100 parts of particles with a multi-metal catalyst layer were dispersed in 1000 parts of ethanol / water mixed solution (volume ratio of ethanol to water was 1:0.2), and then 20 parts of tetraethoxysilane, 6 parts of perfluorooctyltriethoxysilane, 4 parts of vinyltriethoxysilane and 4 parts of γ-glycidoxypropyltrimethoxysilane were added. The pH of the system was adjusted to 9.5, and the co-hydrolysis condensation reaction was carried out at 40°C for 8 h. After the reaction was completed, the product was filtered, washed and dried to obtain fire-resistant and salt spray resistant filler. (5) By weight, 85 parts of vinyl-terminated polydimethylsiloxane and 10 parts of phenyl silicone resin were added to a planetary mixer and mixed evenly. Then, 15 parts of hydrophobic fumed silica, 15 parts of fire-retardant and salt spray resistant filler, 1.5 parts of titanate coupling agent, 1 part of hydrogenated castor oil, 5 parts of dimethyl silicone oil and 2 parts of pigment were added and mixed and degassed under vacuum conditions. The vacuum degree was -0.08 MPa and the mixing time was 60 min to obtain component A. (6) Mix 5 parts of hydrogen-containing silicone oil crosslinking agent, 0.08 parts of 1-ethynylcyclohexanol and 0.5 parts of platinum catalyst (platinum content is 5000ppm) evenly to obtain component B.

[0033] When using, mix component A and component B at a mass ratio of 100:10 until homogeneous, and cure at 25°C for 12 hours.

[0034] Example 2

[0035] A halogen-free fireproof sealing material for marine applications that is resistant to salt spray aging, comprising component A and component B, wherein the mass ratio of component A to component B is 100:8; Its preparation method includes the following steps: (1) Weigh out melamine, tannic acid and phytic acid in a molar ratio of 2.5:1:0.4. Add melamine to deionized water, heat to 90°C and stir to fully dissolve melamine to obtain a melamine solution with a concentration of 0.10 mol / L. Separately dissolve tannic acid and phytic acid in deionized water and adjust the pH to 5.8 to obtain a tannic acid-phytic acid mixed solution (tannic acid concentration of 0.04 mol / L). Add the tannic acid-phytic acid mixed solution dropwise to the melamine solution within 45 min. After the addition is complete, continue the reaction at 88°C for 3 h. After the reaction is complete, filter the obtained product, wash it and dry it at 60°C to obtain the kernel. (2) By weight, 100 parts of the core were dispersed in 1000 parts of Tris buffer at pH 8.5, and 12 parts of dopamine hydrochloride were added. The mixture was stirred at room temperature for 20 h. After the reaction was completed, the core was separated by centrifugation, and the precipitate was washed and dried to obtain polydopamine-coated core. (3) By weight, 100 parts of polydopamine-coated core were dispersed in 1200 parts of 0.25 mol / L 2-methylimidazole solution. After stirring evenly, cobalt chloride, nickel chloride and cerium chloride were added. The molar ratio of Co, Ni and Ce was 1:0.8:0.2, and the molar ratio of 2-methylimidazole to the total metal ions of Co, Ni and Ce was 12:1. The reaction system was reacted at 35°C for 18 h. After the reaction was completed, the mixture was centrifuged, the precipitate was washed and dried to obtain particles with a multi-metal catalyst layer. (4) By weight, 100 parts of particles with a multi-metal catalyst layer were dispersed in 1000 parts of ethanol / water mixed solution (volume ratio of ethanol to water is 1:0.3), and then 22 parts of tetraethoxysilane, 7 parts of tridecafluorooctyltriethoxysilane, 5 parts of vinyltrimethoxysilane and 5 parts of γ-glycidoxypropyltriethoxysilane were added. The pH of the system was adjusted to 10.0, and the co-hydrolysis condensation reaction was carried out at 45°C for 10 h. After the reaction was completed, the product was filtered, washed and dried to obtain fire-resistant and salt spray resistant filler. (5) By weight, 95 parts of vinyl-terminated polydimethylsiloxane and 12 parts of MQ silicone resin were added to a planetary mixer and mixed evenly. Then, 18 parts of hydrophobic fumed silica, 18 parts of fire-retardant and salt spray resistant filler, 2 parts of borate coupling agent, 1.5 parts of polyamide wax, 4 parts of methyl phenyl silicone oil and 1 part of pigment were added and mixed and degassed under vacuum conditions. The vacuum degree was -0.09 MPa and the mixing time was 80 min to obtain component A. (6) By weight, 4 parts of hydrogen-containing silicone oil crosslinking agent, 0.06 parts of 3-methyl-1-butyn-3-ol and 0.6 parts of platinum catalyst (platinum content is 5000ppm) are mixed evenly to obtain component B.

[0036] When using, mix component A and component B evenly at a mass ratio of 100:8 and cure at 50°C for 6 hours.

[0037] Example 3

[0038] A halogen-free fireproof sealing material for marine applications that is resistant to salt spray aging, comprising component A and component B, wherein the mass ratio of component A to component B is 100:12. Its preparation method includes the following steps: (1) Weigh out melamine and tannic acid in a molar ratio of 3:1; add melamine to deionized water, heat to 95°C and stir to fully dissolve melamine to obtain a melamine solution with a concentration of 0.12 mol / L; dissolve tannic acid in deionized water and adjust the pH to 6.5 to obtain a tannic acid solution with a concentration of 0.04 mol / L; add the tannic acid solution dropwise to the melamine solution over 60 min; after the addition is complete, continue the reaction at 90°C for 2.5 h; after the reaction is complete, filter the obtained product, wash it and dry it at 60°C to obtain the kernel; (2) By weight, 100 parts of the core were dispersed in 1000 parts of Tris buffer at pH 8.5, and 15 parts of dopamine hydrochloride were added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, the core was separated by centrifugation, and the precipitate was washed and dried to obtain polydopamine-coated core. (3) By weight, 100 parts of polydopamine-coated core were dispersed in 1200 parts of 0.40 mol / L 2-methylimidazole solution. After stirring evenly, cobalt acetate, nickel acetate and cerium acetate were added. The molar ratio of Co, Ni and Ce was 1:1.0:0.3, and the molar ratio of 2-methylimidazole to the total metal ions of Co, Ni and Ce was 15:1. The reaction system was reacted at 50 °C for 10 h. After the reaction was completed, the mixture was centrifuged, the precipitate was washed and dried to obtain particles with a multi-metal catalyst layer. (4) By weight, 100 parts of particles with a multi-metal catalyst layer were dispersed in 1000 parts of ethanol / water mixed solution (volume ratio of ethanol to water is 1:0.5), and then 25 parts of tetraethoxysilane, 8 parts of perfluorodecyltrimethoxysilane, 6 parts of methacryloyloxypropyltrimethoxysilane and 6 parts of γ-glycidoxypropyltrimethoxysilane were added. The pH of the system was adjusted to 9.0, and the co-hydrolysis condensation reaction was carried out at 50°C for 12 h. After the reaction was completed, the product was filtered, washed and dried to obtain fire-resistant and salt spray resistant filler. (5) By weight, 90 parts of vinyl-terminated polydimethylsiloxane and 15 parts of phenyl silicone resin were added to a planetary mixer and mixed evenly. Then, 22 parts of hydrophobic fumed silica, 22 parts of fire-retardant and salt spray resistant filler, 3 parts of titanate coupling agent, 2 parts of organobentonite, 6 parts of methylphenyl silicone oil and 3 parts of pigment were added and mixed and degassed under vacuum conditions. The vacuum degree was -0.1 MPa and the mixing time was 100 min to obtain component A. (6) Mix 7 parts by weight of hydrogen-containing silicone oil crosslinking agent, 0.12 parts by weight of 3,5-dimethyl-1-hexyn-3-ol and 0.8 parts by weight of platinum catalyst (platinum content is 5000ppm) to obtain component B.

[0039] When using, mix component A and component B at a mass ratio of 100:12 until homogeneous, and cure at 80°C for 2 hours.

[0040] Example 4

[0041] A halogen-free fireproof sealing material for marine applications that is resistant to salt spray aging, comprising component A and component B, wherein the mass ratio of component A to component B is 100:6; Its preparation method includes the following steps: (1) Weigh out melamine, tannic acid and phytic acid in a molar ratio of 1.5:1:0.2. Add melamine to deionized water, heat to 85°C and stir to fully dissolve melamine to obtain a melamine solution with a concentration of 0.10 mol / L. Separately dissolve tannic acid and phytic acid in deionized water and adjust the pH to 6.2 to obtain a tannic acid-phytic acid mixed solution (tannic acid concentration of 0.05 mol / L). Add the tannic acid-phytic acid mixed solution dropwise to the melamine solution within 20 min. After the addition is complete, continue the reaction at 85°C for 4 h. After the reaction is complete, filter the obtained product, wash it and dry it at 60°C to obtain the kernel. (2) By weight, 100 parts of the core were dispersed in 1000 parts of Tris buffer at pH 8.5, and 6 parts of dopamine hydrochloride were added. The mixture was stirred at room temperature for 12 h. After the reaction was completed, the core was separated by centrifugation, and the precipitate was washed and dried to obtain polydopamine-coated core. (3) By weight, 100 parts of polydopamine-coated core were dispersed in 1200 parts of 0.2 mol / L 2-methylimidazole solution. After stirring evenly, cobalt chloride, nickel chloride and cerium chloride were added. The molar ratio of Co, Ni and Ce was 1:0.3:0.05, and the molar ratio of 2-methylimidazole to the total metal ions of Co, Ni and Ce was 8:1. The reaction system was reacted at 30°C for 24 h. After the reaction was completed, the mixture was centrifuged, the precipitate was washed and dried to obtain particles with a multi-metal catalyst layer. (4) By weight, 100 parts of particles with a multi-metal catalyst layer were dispersed in 1000 parts of ethanol / water mixed solution (volume ratio of ethanol to water was 1:0.1), and then 16 parts of tetraethoxysilane, 5 parts of tridecafluorooctyltriethoxysilane, 3 parts of vinyltriethoxysilane and 3 parts of γ-glycidyloxypropyltriethoxysilane were added. The pH of the system was adjusted to 8.5, and the co-hydrolysis condensation reaction was carried out at 35°C for 16 h. After the reaction was completed, the product was filtered, washed and dried to obtain fire-resistant and salt spray resistant filler. (5) By weight, 90 parts of vinyl-terminated polydimethylsiloxane and 18 parts of MQ silicone resin were added to a planetary mixer and mixed evenly. Then, 12 parts of hydrophobic fumed silica, 12 parts of fire-retardant and salt spray resistant filler, 2.5 parts of titanate coupling agent, 0.8 parts of hydrogenated castor oil, 3 parts of methyl phenyl silicone oil and 1.5 parts of pigment were added and mixed and degassed under vacuum conditions. The vacuum degree was -0.07 MPa and the mixing time was 50 min to obtain component A. (6) Mix 3 parts by weight of hydrogen-containing silicone oil crosslinking agent, 0.05 parts by weight of 1-ethynylcyclohexanol and 0.4 parts by weight of platinum catalyst (platinum content is 5000ppm) to obtain component B.

[0042] When using, mix component A and component B evenly at a mass ratio of 100:6 and cure at 25°C for 24 hours.

[0043] Example 5

[0044] A halogen-free fireproof sealing material for marine applications that is resistant to salt spray aging, comprising component A and component B, wherein the mass ratio of component A to component B is 100:15; Its preparation method includes the following steps: (1) Weigh out melamine and tannic acid in a molar ratio of 1.2:1; add melamine to deionized water, heat to 85°C and stir to fully dissolve melamine to obtain a melamine solution with a concentration of 0.10 mol / L; dissolve tannic acid in deionized water and adjust the pH to 6.0 to obtain a tannic acid solution with a concentration of 0.05 mol / L; add the tannic acid solution dropwise to the melamine solution within 30 min; after the addition is complete, continue the reaction at 85°C for 3 h; after the reaction is complete, filter the obtained product, wash it and dry it at 60°C to obtain the kernel; (2) By weight, 100 parts of the core were dispersed in 1000 parts of Tris buffer at pH 8.5, and 11 parts of dopamine hydrochloride were added. The mixture was stirred at room temperature for 18 h. After the reaction was completed, the core was separated by centrifugation, and the precipitate was washed and dried to obtain polydopamine-coated core. (3) By weight, 100 parts of polydopamine-coated core were dispersed in 1200 parts of 0.30 mol / L 2-methylimidazole solution. After stirring evenly, cobalt nitrate, nickel nitrate and cerium nitrate were added. The molar ratio of Co, Ni and Ce was 1:0.6:0.15, and the molar ratio of 2-methylimidazole to the total metal ions of Co, Ni and Ce was 9:1. The reaction system was reacted at 40℃ for 12 h. After the reaction was completed, the mixture was centrifuged, the precipitate was washed and dried to obtain particles with a multi-metal catalyst layer. (4) By weight, 100 parts of particles with a multi-metal catalyst layer were dispersed in 1000 parts of ethanol / water mixed solution (volume ratio of ethanol to water was 1:0.2), and then 21 parts of tetraethoxysilane, 6 parts of perfluorooctyltriethoxysilane, 4 parts of vinyltrimethoxysilane and 4 parts of γ-glycidoxypropyltrimethoxysilane were added. The pH of the system was adjusted to 9.5, and the co-hydrolysis condensation reaction was carried out at 40°C for 8 h. After the reaction was completed, the product was filtered, washed and dried to obtain fire-resistant and salt spray resistant filler. (5) By weight, 90 parts of vinyl-terminated polydimethylsiloxane and 12 parts of phenyl silicone resin were added to a planetary mixer and mixed evenly. Then, 16 parts of hydrophobic fumed silica, 16 parts of fire-retardant and salt spray resistant filler, 2 parts of titanate coupling agent, 1 part of polyamide wax, 4 parts of dimethyl silicone oil and 2 parts of pigment were added. The mixture was then kneaded and degassed under vacuum conditions. The vacuum degree was -0.08 MPa and the kneading time was 70 min to obtain component A. (6) Mix 8 parts by weight of hydrogen-containing silicone oil crosslinking agent, 0.1 parts by weight of 1-ethynylcyclohexanol and 1.0 parts by weight of platinum catalyst (platinum content is 5000ppm) to obtain component B.

[0045] When using, mix component A and component B at a mass ratio of 100:15 until homogeneous, and cure at 60°C for 3 hours.

[0046] Comparative Example 1 The difference between this example and Example 1 is that the fire-resistant and salt spray-resistant filler does not include a hydrophobic shell layer, while the other operations are the same as in Example 1.

[0047] Comparative Example 2 The difference between this example and Example 1 is that the fire-resistant and salt spray-resistant filler does not include a multi-metal catalytic layer, while the other operations are the same as in Example 1.

[0048] Comparative Example 3 The difference between this example and Example 1 is that no fire-retardant and salt spray resistant filler is added to component A, while the other operations are the same as in Example 1.

[0049] The performance of the materials prepared in the above embodiments and comparative examples was tested. The test methods and results are as follows: Performance testing standards and methods 1. Flame retardant properties: (1) Limiting oxygen index (LOI): determined according to GB / T 2406.2-2009, with a sample size of 150mm×6mm×3mm.

[0050] (2) Vertical flammability rating: determined according to GB / T 2408-2021, with a sample size of 125mm×13mm×3mm.

[0051] (3) Smoke density: determined according to the smoke box method of GB / T 8627-2007, with sample size of 75mm×75mm×3mm and flameless mode.

[0052] 2. Mechanical properties: (1) Tensile strength and elongation at break: determined according to GB / T 528-2009, type I dumbbell-shaped specimen, tensile speed 500 mm / min.

[0053] (2) Bond strength: Measured according to GB / T 13477.3-2017, the substrate is sandblasted stainless steel plate, and the overlap shear tensile speed is 50 mm / min.

[0054] 3. Salt spray aging resistance: According to GB / T 10125-2021 Neutral Salt Spray Test (NSS), 5% NaCl solution was used for continuous spraying for 1000 hours at a test chamber temperature of 35℃. After aging, the test pieces were removed, rinsed with deionized water, and dried at room temperature for 24 hours. The tensile strength and adhesive strength were then measured according to the above method. The performance retention rate was used to characterize the salt spray aging resistance.

[0055] Performance retention rate = (performance value after aging / performance value before aging) × 100%.

[0056] 4. Charcoal-forming properties: Carbon residue at 800℃: determined by thermogravimetric analysis (TGA) under nitrogen atmosphere at a heating rate of 10℃ / min.

[0057] The test results are shown in Table 1.

[0058] Table 1 ; As can be seen from the test results in Table 1, the marine halogen-free fireproof sealing materials with salt spray aging resistance obtained in the embodiments of the present invention all exhibit excellent flame retardant properties, mechanical properties, adhesive properties, salt spray aging resistance and char formation properties. This indicates that the organosilicon matrix and the multi-layer composite fireproof and salt spray resistant filler in the sealing material of the present invention have a good synergistic effect, which can effectively improve the comprehensive performance of the sealing material in the service environment of ships and marine engineering.

[0059] In terms of flame retardant performance, the limiting oxygen index (LOI) of Examples 1-5 all reached over 35.8%, with Examples 2 and 3 reaching 38.2% and 39.0% respectively, significantly higher than Comparative Example 2's 30.2% and Comparative Example 3's 22.5%. Simultaneously, the vertical burning rating of Examples 1-5 all reached V-0, while Comparative Example 3 without the fire-retardant and salt-spray resistant filler was only HB, and Comparative Example 2 lacking the multi-metal catalyst layer dropped to V-1. These results demonstrate that the fire-retardant and salt-spray resistant filler of the present invention can significantly improve the flame retardant efficiency of the sealing material. In particular, the tannic acid-melamine salt or tannic acid-phytic acid-melamine ternary supramolecular salt in the core can exert a synergistic flame retardant effect of phosphorus and nitrogen and promote char formation during combustion. At the same time, the multi-metal catalyst layer containing Co, Ni, and Ce can further promote the densification and stabilization of the char layer, enabling the material to form a continuous, dense, and high-strength protective char layer under flame action, thereby effectively blocking the transfer of heat, oxygen, and combustible volatiles.

[0060] The smoke density test results show that the maximum smoke density DS,max of Examples 1-5 is 98-138, which is significantly lower than that of Comparative Examples 1-3. Example 3, in particular, has the lowest smoke density, indicating that it has a better smoke suppression effect during combustion. This result demonstrates that the present invention uses a halogen-free flame retardant system and promotes char layer formation and densification through a multi-metal catalytic layer. This not only improves flame retardant performance but also reduces smoke release during combustion, meeting the requirements for low smoke, low toxicity, and environmental safety in applications such as ships, offshore platforms, and enclosed compartments.

[0061] From a mechanical property perspective, the tensile strength of Examples 1-5 was 5.5-6.5 MPa, the elongation at break was 280%-340%, and the bond strength was 2.6-3.2 MPa. Compared with Comparative Example 3 without the addition of fire-retardant and salt spray resistant filler, Examples 1-5 showed significantly improved flame retardant performance without significant deterioration in mechanical properties; on the contrary, the tensile strength and bond strength were improved. This result indicates that the fire-retardant and salt spray resistant filler of the present invention is not simply dispersed as an inert inorganic filler in an organosilicon matrix, but rather improves the interfacial bonding between the filler and the organosilicon matrix through a polydopamine adhesive layer and a hydrophobic shell containing reactive groups. The reactive groups such as vinyl, epoxy, methacryloyloxy, or hydrosilyl groups in the hydrophobic shell can physically entangle or chemically bond with the organosilicon matrix during curing or interfacial bonding, thereby reducing filler agglomeration, interfacial debonding, and stress concentration, enabling the material to achieve high structural strength and bond stability while maintaining flexibility.

[0062] In terms of salt spray aging resistance, after 1000 hours of neutral salt spray aging, Examples 1-5 still maintained a tensile strength retention rate of 90%-95% and an adhesive strength retention rate of 87%-93%. In contrast, Comparative Example 1, which did not include a hydrophobic shell layer in its fire-retardant salt spray aging filler, had a tensile strength retention rate of only 68% and an adhesive strength retention rate of only 55% after 1000 hours of salt spray aging; Comparative Example 3, which did not add fire-retardant salt spray aging filler, had tensile strength and adhesive strength retention rates of 72% and 60%, respectively. These results indicate that a hydrophobic shell layer can improve the salt spray aging stability of sealing materials. This hydrophobic shell layer, formed by the copolymerization of fluorosiloxane, silica, and reactive silane, effectively reduces the hydrophilicity of the filler surface, hinders the penetration of moisture, chloride ions, and salt spray media into the filler interface, reduces moisture absorption, migration, and interface peeling of the filler, thereby significantly improving the retention rate of mechanical properties and adhesive properties of the material after long-term salt spray aging.

[0063] In terms of char formation performance, the char residue rates of Examples 1-5 at 800℃ were 40.1%-48.2%, significantly higher than those of Comparative Examples 2 and 3. Example 3 achieved a char residue rate of 48.2%. This result indicates that the tannic acid, phytic acid, and melamine components in the fire-retardant and salt-spray resistant filler of this invention can provide carbon, acid, and gas sources during thermal decomposition, promoting expansion and char formation. Simultaneously, the multi-metal catalytic layer can catalyze the cross-linking, aromatization, and densification of the char layer, and together with the inorganic silicon-oxygen structure generated by the thermal decomposition of the organosilicon matrix, form a stable carbon-silicon composite barrier layer, thereby significantly improving the high-temperature char residue rate and fire-resistant and heat-insulating capabilities of the material. Compared to the examples, Comparative Example 1, lacking a hydrophobic shell layer, still exhibited certain flame-retardant properties, but its tensile strength retention rate and adhesive strength retention rate after salt spray aging significantly decreased, indicating that the hydrophobic shell layer has a significant impact on the interfacial stability and performance retention under long-term marine salt spray conditions. In Comparative Example 2, without the multi-metal catalyst layer, the LOI dropped to 30.2%, the vertical burning rating decreased to V-1, and the char residue at 800℃ dropped to 28.5%, indicating that the multi-metal catalyst layer has a significant effect on improving flame retardant efficiency, promoting char formation, and reducing smoke density. In Comparative Example 3, without the addition of fire-retardant and salt spray-resistant filler, the LOI was only 22.5%, the vertical burning rating was HB, the smoke density was as high as 280, and the char residue at 800℃ was only 12.3%, indicating that the ordinary organosilicon sealing system itself has limited flame retardant and char-forming capabilities, making it difficult to meet the requirements of high-grade marine fire-retardant sealing materials.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A halogen-free fireproof sealing material for marine applications, resistant to salt spray aging, characterized in that, It includes component A and component B, wherein the mass ratio of component A to component B is 100:(5-15); Component A, by weight, comprises 65-120 parts of vinyl-terminated polydimethylsiloxane, 5-20 parts of silicone resin, 8-25 parts of hydrophobic fumed silica, 8-25 parts of fire-retardant and salt spray resistant filler, 0.5-5 parts of coupling agent, 0-3 parts of thixotropic agent, and 0-10 parts of plasticizer. 0-5 parts of pigment; Component B, by weight, comprises: 2-10 parts of hydrogen-containing silicone oil crosslinking agent, 0.01-0.3 parts of alkynol inhibitor, and 0.1-1.8 parts of platinum catalyst; The fire-retardant and salt spray-resistant filler has a multi-layer structure consisting of a core, an adhesive layer, a catalytic layer, and a hydrophobic shell. The core is a tannic acid-melamine salt or a tannic acid-phytic acid-melamine ternary supramolecular salt. The adhesive layer is a polydopamine layer. The catalytic layer is a multi-metallic organic framework, metal hydroxide, metal oxide, or a composite layer thereof containing Co, Ni, and Ce. The hydrophobic shell is a fluorosiloxane-silica-reactive silane cocondensation layer. The hydrophobic shell contains at least one reactive group selected from vinyl, epoxy, methacryloxy, or hydrosilyl groups.

2. The marine halogen-free fireproof sealing material resistant to salt spray aging according to claim 1, characterized in that, The tannic acid-melamine salt is formed by tannic acid and melamine through hydrogen bonding and ionic association, and the molar ratio of tannic acid to melamine is 1:(0.5-5). Alternatively, the tannic acid-phytic acid-melamine ternary supramolecular salt is formed by tannic acid, phytic acid and melamine through hydrogen bonding, ion association and phosphorus-nitrogen synergistic carbonization; the molar ratio of tannic acid, phytic acid and melamine is 1:(0.05-1.5):(0.5-5).

3. The marine halogen-free fireproof sealing material resistant to salt spray aging according to claim 1, characterized in that, The molar ratio of Co, Ni, and Ce in the catalyst layer is 1:(0.1-1.5):(0.02-0.8); the Ce content is Ce... 3+ Ce 4+ or Ce 3+ / Ce 4+ Mixed valence states exist.

4. The marine halogen-free fireproof sealing material resistant to salt spray aging according to claim 1, characterized in that, The hydrophobic shell is formed by co-hydrolysis and condensation of tetraethoxysilane, fluorinated silane, vinyl silane, and epoxy silane; the fluorinated silane includes one or more of perfluorooctyltriethoxysilane, perfluorodecyltrimethoxysilane, and tridecafluorooctyltriethoxysilane; the vinyl silane includes one or more of vinyltriethoxysilane, vinyltrimethoxysilane, and methacryloxypropyltrimethoxysilane; and the epoxy silane includes one or more of γ-glycidoxypropyltrimethoxysilane and γ-glycidoxypropyltriethoxysilane.

5. The marine halogen-free fireproof sealing material resistant to salt spray aging according to claim 1, characterized in that, The fire-retardant and salt spray-resistant filler has a D50 particle size of 0.3-10μm; the polydopamine layer has a thickness of 5-100nm; the catalyst layer has a thickness of 10-300nm; and the hydrophobic shell has a thickness of 10-500nm.

6. The marine halogen-free fireproof sealing material resistant to salt spray aging according to claim 1, characterized in that, The organosilicon resin is phenyl silicone resin, MQ silicone resin, or a combination thereof; Alternatively, the coupling agent may include one or more of titanate coupling agents and borate coupling agents; the alkynol inhibitor may include one or more of 1-ethynylcyclohexanol, 3-methyl-1-butyn-3-ol, and 3,5-dimethyl-1-hexyn-3-ol. Alternatively, the thixotropic agent may include one of hydrogenated castor oil, polyamide wax, or organobentonite; and the plasticizer may include one of dimethyl silicone oil or methylphenyl silicone oil.

7. A method for preparing a salt spray resistant, halogen-free marine fireproof sealing material according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Dissolve melamine in hot water at 80-95℃, adjust the pH of tannic acid solution or tannic acid-phytic acid mixed solution to 5.0-7.0 and add it to the melamine solution to react, filter, wash and dry to obtain the kernel; (2) Disperse the kernel obtained in step (1) in Tris buffer, add dopamine hydrochloride, and react for 12-24 h at pH 8.0-8.8 to obtain polydopamine-coated kernel; (3) The polydopamine-coated core obtained in step (2) is dispersed in a solution containing 2-methylimidazole, and cobalt salt, nickel salt and cerium salt are added to carry out an in-situ growth reaction to obtain particles with a multi-metal catalytic layer. (4) Disperse the particles obtained in step (3) in an ethanol / water mixed solution, add tetraethoxysilane, fluorinated silane, vinyl silane and epoxy silane, co-hydrolyze and condense under alkaline conditions, and dry to obtain fireproof and salt spray resistant filler. (5) Mix and degas the vinyl-terminated polydimethylsiloxane, organosilicon resin, hydrophobic fumed silica, fire-retardant and salt spray resistant filler obtained in step (4), coupling agent, thixotropic agent, plasticizer and pigment to obtain component A; (6) Mix the hydrogen-containing silicone oil crosslinking agent, platinum catalyst, and alkynol inhibitor evenly to obtain component B.

8. The method for preparing a salt spray resistant marine halogen-free fireproof sealing material according to claim 7, characterized in that, In step (1), the tannic acid solution or tannic acid-phytic acid mixed solution is added dropwise over a period of 15-60 min; the reaction temperature is 80-90℃ and the reaction time is 2-4 h.

9. The method for preparing a salt spray aging resistant marine halogen-free fireproof sealing material according to claim 7, characterized in that, In step (3), the concentration of the 2-methylimidazole solution is 0.2-0.4 mol / L, and the molar ratio of 2-methylimidazole to the total metal ions of Co, Ni, and Ce is (6:1)-(15:1). Alternatively, the cobalt salt, nickel salt, and cerium salt may be selected from their respective nitrates, chlorides, acetates, or sulfates; Alternatively, the in-situ growth temperature may be 20-60℃, and the time may be 6-24h.

10. The method for preparing a salt spray resistant marine halogen-free fireproof sealing material according to claim 7, characterized in that, In the ethanol / water mixed solution, the volume ratio of ethanol to water is 1:(0.05-1); the alkaline conditions are pH 8.0-11.0; the co-hydrolysis condensation reaction temperature is 20-60℃, and the time is 4-24h. Alternatively, the mixing pressure can be -0.06MPa to -0.10MPa, and the mixing time can be 20-120min.