Flame-retardant silicone sealant and preparation method thereof

Abstract

This application relates to the field of silicone sealants, specifically disclosing a flame-retardant silicone sealant and its preparation method. The flame-retardant silicone sealant comprises the following raw materials in parts by weight: 100 parts α,ω-dihydroxypolydimethylsiloxane, 10-30 parts dimethyl silicone oil, 15-25 parts phenylmethyl silicone oil, 4-10 parts crosslinking agent, 0.2-0.5 parts catalyst, 1-2 parts silane coupling agent, 30-50 parts flame retardant, 8-12 parts reinforcing agent, and 5-20 parts modified ceramic micropowder. The silicone sealant of this application has the advantages of good flame retardancy and excellent fire resistance.

Description

Technical Field

[0001] This application relates to the field of silicone sealants, and more specifically, to a flame-retardant silicone sealant and a method for preparing the same. Background Technology

[0002] Silicone sealants are made primarily of polydimethylsiloxane, mixed with crosslinking agents, fillers, coupling agents, etc. After curing, they form an elastic silicone rubber that can be used in numerous fields such as construction, aerospace, medical, military, and electronic devices. They are most commonly used for bonding and sealing materials such as glass and metal. With the increasing fire safety requirements in the construction industry and the miniaturization and high integration of electronic components, new demands have been placed on the flame-retardant properties of silicone sealants, making flame-retardant silicone sealants a hot topic in research and application.

[0003] While common silicone sealants can be used long-term at temperatures ranging from -60℃ to 200℃, they tend to debond, crack, break, or even pulverize at higher temperatures, especially above 300℃. The flame-retardant and heat-resistant properties of silicone sealants can usually be improved by adding flame-retardant and heat-resistant materials, such as halogenated flame retardants, inorganic flame retardants, and phosphorus-based flame retardants. Although this effectively improves flame-retardant and heat-resistant properties, the structural stability of silicone sealants remains insufficient at high temperatures, and shrinkage and cracking may still occur. Therefore, adding ceramic powder to increase the structural stability of silicone sealants at high temperatures has become one of the research directions in the silicone sealant field. Ceramic powder ceramizes at high temperatures, effectively solving the pulverization problem of silicone sealants at high temperatures.

[0004] In view of the above, this application is hereby submitted. Summary of the Invention

[0005] In order to provide a flame-retardant silicone sealant with good flame retardancy and stable sealing performance at high temperatures, this application provides a flame-retardant silicone sealant and its preparation method.

[0006] In a first aspect, this application provides a flame-retardant silicone sealant, which adopts the following technical solution:

[0007] A flame-retardant silicone sealant, comprising the following raw materials in parts by weight:

[0008] 100 parts of α,ω-dihydroxypolydimethylsiloxane, 10-30 parts of dimethyl silicone oil, 15-25 parts of phenylmethyl silicone oil, 4-10 parts of crosslinking agent, 0.2-0.5 parts of catalyst, 1-2 parts of silane coupling agent, 30-50 parts of flame retardant, 8-12 parts of reinforcing agent, and 5-20 parts of modified ceramic micro powder;

[0009] The flame retardant includes ammonium polyphosphate, resorcinol bis(diphenyl phosphate) and zinc borate;

[0010] The modified ceramic micro powder includes ceramic micro powder and a surface shell layer, the shell layer specifically including: a sodium polystyrene sulfonate-polyethyleneimine polymer layer formed by self-assembly of polyelectrolytes, and epoxy siloxane grafted onto the surface of the polymer coating layer.

[0011] Preferably, the mass ratio of ammonium polyphosphate, resorcinol bis(diphenyl phosphate), and zinc borate is (3-5):(2-4):1.

[0012] Preferably, the ceramic micropowder comprises silicon nitride, zirconium dioxide, alumina, and / or boehmite.

[0013] Preferably, the ceramic micro powder comprises silicon nitride, zirconium dioxide, alumina, and boehmite in a mass ratio of (1-2):(0.5-1.5):(4-6):(2-4).

[0014] Preferably, the silicon nitride has a particle size of 0.5-2 μm; the zirconium dioxide has a particle size of 1-4 μm; the alumina has a particle size of 2-12 μm; and the boehmite has a particle size of 2-12 μm.

[0015] Preferably, the mass ratio of the ceramic micro powder, sodium polystyrene sulfonate, polyethyleneimine, and epoxy siloxane is 100:(4-6):(5-8):(3-10).

[0016] Preferably, the epoxy siloxane is γ-glycidoxypropyltrimethoxysilane or γ-glycidoxypropyltriethoxysilane.

[0017] Preferably, the crosslinking agent is selected from one or more of acyloxysilane crosslinking agents, ketoxime silane crosslinking agents, and alkoxysilane crosslinking agents.

[0018] Preferably, the catalyst is selected from one or more of dibutyltin dilaurate, dibutyltin diacetate, stannous octoate, dioctyltin dilaurate, and dibutyltin acetylacetonate.

[0019] Preferably, the reinforcing agent is hydrophobic fumed silica.

[0020] Preferably, the viscosity of the α,ω-dihydroxy polydimethylsiloxane is 10,000-50,000 mPa·s (25°C), the viscosity of the dimethyl silicone oil is 100-500 mPa·s (25°C), and the viscosity of the phenylmethyl silicone oil is 500-1200 mPa·s (25°C).

[0021] Secondly, this application provides a method for preparing a flame-retardant silicone sealant, using the following technical solution:

[0022] Add α,ω-dihydroxypolydimethylsiloxane, dimethyl silicone oil, phenylmethyl silicone oil, and reinforcing agent to a planetary mixer, and stir at low speed of 50-100 rpm for 5-10 minutes under vacuum conditions, and then stir at high speed of 300-500 rpm for 30-40 minutes to obtain the base material.

[0023] Add flame retardant and modified ceramic powder, stir at low speed of 50-100 rpm for 10-20 minutes, then stir at high speed for 40-60 minutes; then add crosslinking agent, coupling agent and catalyst, stir at low speed of 30-50 rpm for 10-15 minutes, then degas under vacuum to obtain silicone sealant.

[0024] In summary, this application has the following beneficial effects:

[0025] 1. This application enables the silicone sealant to be ceramicized at high temperatures by adding modified ceramic micropowder, thereby improving the overall stability of the silicone sealant. Furthermore, the ceramic micropowder is modified to form a polyelectrolyte-silane hybrid shell on its surface, which avoids the separation of the interface between the silicone sealant matrix and the ceramic micropowder particles, reduces the possibility of the silicone sealant splitting and pulverizing, and synergistically optimizes the flame retardancy of the sealant with a specific flame retardant.

[0026] 2. This application uses a phase-graded mixture of silicon nitride, alumina, zirconium dioxide, and boehmite to create a ceramic phase that exhibits excellent high-temperature stability, high strength, and certain thermal shock resistance and toughness, while also providing inorganic flame retardant effects.

[0027] 3. This application improves the compounding of flame retardants to construct a multi-stage synergistic flame retardant and fluxing system. While achieving excellent flame retardant effect, it also plays a synergistic fluxing role, promoting the uniform formation of the ceramic continuous phase and improving the integrity of the ceramic phase. Detailed Implementation

[0028] To further aid in understanding the technical solution of this invention, several specific implementation examples are provided below to describe the technical solution of this invention in more detail. All described embodiments are only some embodiments of this invention, not all of them. It should be understood that the following description is merely illustrative and is not intended to limit the scope of this invention. The scope of protection of this invention is defined by the appended claims. Furthermore, those skilled in the art will understand that modifications can be made to the technical solution of this invention without departing from the spirit and intent of this invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter pertains. Before a detailed description of the invention, the following definitions are provided to better understand the invention.

[0030] In cases where numerical ranges are provided, such as concentration ranges, percentage ranges, or ratio ranges, it should be understood that, unless the context explicitly specifies otherwise, all intermediate values ​​between the upper and lower limits of the range, up to one-tenth of the lower limit unit, and any other values ​​or intermediate values ​​within the range are included in the subject matter. The upper and lower limits of these smaller ranges may be independently included in the smaller ranges, and such embodiments are also included in the subject matter, limited by any specific excluded limit values ​​within the range. Where the range includes one or two limit values, the range excluding any one or both of those included limit values ​​is also included in the subject matter.

[0031] In the context of this invention, many embodiments use the expressions "comprising," "including," or "basically / mainly composed of." The expressions "comprising," "including," or "basically / mainly composed of" are generally understood as open-ended expressions, indicating that they include not only the elements, components, parts, or method steps specifically listed after the expression, but also other elements, components, parts, or method steps. However, in this document, the expressions "comprising," "including," or "basically / mainly composed of" can also be understood as closed-ended expressions in certain cases, indicating that they only include the elements, components, parts, or method steps specifically listed after the expression, and do not include any other elements, components, parts, or method steps. In this case, the expression is equivalent to the expression "composed of."

[0032] To better understand this teaching and without limiting its scope, all figures and other numerical values ​​used in the specification and claims to express quantities, percentages, or proportions should, in all cases, be understood to be modified by the term "about." Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​that may vary depending on the desired properties sought. At a minimum, each numerical parameter should be interpreted based at least on the reported significant figures and by applying common rounding techniques.

[0033] In the context of the invention, ordinal numbers such as “first,” “second,” “third,” or “(1),” “(2),” “(3)” are used to describe the invention. It should be understood that the purpose of using ordinal numbers is only to distinguish the different components, structures, elements, steps, etc. involved in the description of the invention, and is not intended to limit the order or hierarchy of these different components, structures, elements, steps, etc., unless explicitly stated in the context.

[0034] In order to obtain a silicone sealant that is structurally stable at high temperatures, not prone to cracking and powdering, and has good flame retardancy, this application provides a flame-retardant silicone sealant, its preparation method, and its application.

[0035] In a first aspect, this application provides a flame-retardant silicone sealant comprising the following raw materials in parts by weight:

[0036] 100 parts of α,ω-dihydroxypolydimethylsiloxane, 10-30 parts of dimethyl silicone oil, 15-25 parts of phenylmethyl silicone oil, 4-10 parts of crosslinking agent, 0.2-0.5 parts of catalyst, 1-2 parts of silane coupling agent, 30-50 parts of flame retardant, 8-12 parts of reinforcing agent, and 5-20 parts of modified ceramic micro powder.

[0037] This application improves the overall stability of silicone sealant by adding modified ceramic micropowder, enabling the sealant to be ceramicized at high temperatures. To prevent the silicone rubber from splitting due to interfacial separation between the silicone rubber and ceramic micropowder particles caused by high-temperature shrinkage, this application modifies the ceramic micropowder by constructing a polyelectrolyte-silane hybrid shell on its surface.

[0038] In a preferred embodiment, the modified ceramic micropowder comprises ceramic micropowder and a shell layer constructed on its surface through self-assembly of polyelectrolyte layers and silanization reaction. Specifically, the shell layer is sodium polystyrene sulfonate-polyethyleneimine-epoxysiloxane. With the ceramic micropowder particles as the core and the hybrid polymer layer as the shell, this polymer shell layer can promote the chemical bonding and sintering synergy between the ceramic micropowder and the silicone matrix at high temperatures. At high temperatures, the polymer layer will first transform and decompose, acting as a flux to help lower the temperature at which the ceramic micropowder and the silicone matrix undergo eutectic reaction, promoting the formation of a more continuous and denser ceramic protective layer. Furthermore, through interfacial bonding, it can anchor the ceramic micropowder within the silicone matrix network, forming a three-dimensional network skeleton. This effectively avoids interfacial separation and crack propagation problems caused by the high-temperature decomposition and shrinkage of silicone rubber, thereby significantly enhancing the density, integrity, and bonding strength with the matrix of the ceramicized layer. This helps improve the overall structural stability and fire-resistant sealing performance of the silicone sealant at high temperatures.

[0039] In a preferred embodiment, the ceramic micropowder is selected from one or more of alumina, zirconium dioxide, silicon carbide, silicon nitride, boehmite, silicon dioxide, titanium dioxide, magnesium dioxide, barium sulfate, zirconium oxide, and calcium oxide. Further, the ceramic micropowder includes silicon nitride, zirconium dioxide, alumina, and / or boehmite. Alumina and silicon nitride possess high-temperature stability and high strength, providing strength support as the basic ceramic framework. Silicon nitride oxidizes at high temperatures to form a silicon dioxide protective layer, which can cooperate with the silicon dioxide in the silicone matrix to enhance the strength of the ceramic layer. Zirconium dioxide has a phase transformation toughening effect and can serve as a high-performance toughening phase, improving the thermal shock resistance and toughness of the ceramic layer at high temperatures, thus reducing cracking of the ceramic layer during flame impact or cooling. Boehmite, also known as boehmite, decomposes at high temperatures, absorbing heat and releasing water vapor, thus providing an inorganic flame retardant effect. The alumina produced during decomposition can participate in the formation of the ceramic framework layer.

[0040] In a preferred embodiment, the ceramic micropowder comprises silicon nitride, zirconium dioxide, alumina, and boehmite in a mass ratio of (1-2):(0.5-1.5):(4-6):(2-4). The silicon nitride has a particle size of 0.5-2 μm; the zirconium dioxide has a particle size of 1-4 μm; the alumina has a particle size of 2-12 μm; and the boehmite has a particle size of 2-12 μm. Using alumina as the main framework ceramic material, supplemented by a phase gradation of smaller-sized silicon nitride, a stable ceramic framework layer can be formed at high temperatures. Replacing some alumina with a certain amount of boehmite allows the ceramic micropowder to exert a synergistic flame-retardant effect. Simultaneously, the mixing of a certain amount of zirconium dioxide improves the toughness of the ceramic layer and ensures its structural stability.

[0041] In a preferred embodiment, the method for preparing the modified ceramic material includes the following steps:

[0042] Surface activation treatment of ceramic micro powder yields ceramic micro powder with a surface rich in cations;

[0043] The ceramic micro powder was ultrasonically dispersed in water to obtain a primary suspension. Sodium polystyrene sulfonate was added to the suspension, and the mixture was stirred and reacted at room temperature. After centrifugation, primary particles were obtained.

[0044] The primary particles were ultrasonically dispersed in water to obtain a secondary suspension;

[0045] Polyethyleneimine was dissolved in water and mixed with a secondary suspension under stirring. The mixture was stirred at room temperature and then centrifuged to obtain secondary particles.

[0046] Epoxysiloxanes were hydrolyzed in ethanol solution to prepare a siloxane solution. Secondary particles were added, and the pH was adjusted to 8-9 with triethylamine. The mixture was stirred and reacted at 50-60℃ under a nitrogen atmosphere for 4-12 hours. After centrifugation, washing, vacuum drying at 40-60℃, and heat treatment at 100-120℃ for 20-40 minutes under a nitrogen atmosphere, modified ceramic micro powder was obtained.

[0047] Sodium polystyrene sulfonate exhibits negative charge (-SO3) due to the ionization of its sulfonic acid groups in aqueous solution. - Sodium polystyrene sulfonate (PSS) can be adsorbed onto the surface of ceramic micropowder through electrostatic interactions, forming a negatively charged layer. The rigidity and steric hindrance of its benzene ring structure reduce excessive inter-chain entanglement, facilitating the formation of a uniform negatively charged PSS coating layer. Polyethyleneimine, being cationic, can undergo layer-by-layer self-assembly onto the ceramic micropowder through electrostatic interactions, and the hydrogen bonding between polyethyleneimine chains enhances the stability and density of the coating film. The polyelectrolyte coating layer of sodium polystyrene sulfonate-polyethyleneimine achieves self-assembly through strong electrostatic interactions, forming a stable shell structure that helps absorb and disperse internal stress. It also reduces ceramic particle agglomeration through electrostatic repulsion and steric hindrance. At high temperatures, the polymer shell melts and decomposes first, acting as a flux, which helps lower the ceramic phase formation temperature and promotes the formation of a continuous ceramic phase, resulting in a more ordered sintering of ceramic particles. On the other hand, there is an ionic bond between polyethyleneimine and ammonium polyphosphate, a hydrogen bond between polyethyleneimine and the phosphine oxide of resorcinol bis(diphenyl phosphate), a coordination effect with zinc ions in zinc borate, and a bond with borate ions. Based on these different forces, the polyethyleneimine shell facilitates the adhesion and uniform distribution of the mixed flame retardant of ammonium polyphosphate (APP), resorcinol bis(diphenyl phosphate) (RDP), and zinc borate (ZB). Therefore, the polymer shell can attract flame retardant molecules to the vicinity of ceramic particles through electrostatic adsorption, hydrogen bonding, and coordination. These molecules should be uniformly mixed and distributed near the ceramic particles based on different forces to reduce the migration and precipitation of flame retardant molecules and enhance the fluxing effect of the flame retardant.

[0048] To further improve the overall compatibility between ceramic microparticles and the silicone matrix and reduce interfacial separation, this application uses epoxy-based siloxanes for further surface modification. Epoxy-based siloxanes can covalently bond with the polyelectrolyte coating layer and anchor on the surface of ceramic microparticles. The surface siloxane segments and the matrix have very good compatibility, which is conducive to the effective connection and uniform distribution of ceramic microparticles and silicone matrix, and helps to reduce microcracks and pores at the interface with the silicone matrix, so as to form a ceramic phase with higher strength and better overall stability.

[0049] In a preferred embodiment, the mass ratio of ceramic micro powder, sodium polystyrene sulfonate, polyethyleneimine, and epoxy siloxane is 100:(4-6):(5-8):(3-10).

[0050] In a preferred embodiment, the epoxy siloxane is γ-glycidoxypropyltrimethoxysilane or γ-glycidoxypropyltriethoxysilane.

[0051] In a preferred embodiment, the activation treatment is selected from any of the following: pickling, plasma treatment, surface modification with cationic surfactants, etc.

[0052] In a preferred embodiment, the flame retardant comprises ammonium polyphosphate (APP), resorcinol bis(diphenyl phosphate) (RDP), and zinc borate (ZB). By improving the selection of the flame retardant compound, a multi-stage synergistic flame retardant and fluxing system was constructed. On the one hand, in the initial stage of temperature rise, zinc borate absorbs heat and releases water of crystallization, and begins to melt to form an initial glassy state, providing initial flame retardant function. As the temperature rises, ammonium polyphosphate decomposes to produce polyphosphoric acid substances and ammonia. The decomposition product polyphosphoric acid has strong dehydration properties, which can catalyze the decomposition products of silicone polymer matrix and resorcinol bis(diphenyl phosphate) to undergo dehydration and crosslinking reaction. Resorcinol bis(diphenyl phosphate) decomposes rapidly under the catalysis of polyphosphoric acid to achieve gas phase flame retardancy and participate in char formation to exert a condensed phase flame retardant effect. The resulting melt has a low viscosity, which promotes the formation and expansion of the expanded char layer, and can further react with the decomposition products of zinc borate to generate borophosphate glass with better thermal stability and higher viscosity. The borophosphate glass is combined with the char skeleton phase, and the borate glass formed by zinc borate itself participates in filling and reinforcing the expanded char layer, which can form a dense char flame retardant layer. On the other hand, eutectic borate and borophosphate glass can reduce the melt viscosity of the system, play a bonding and lubricating role to promote the flow and sintering of ceramic micropowder, promote the formation and densification of the ceramic continuous phase at a lower temperature, so that it can play a flame-retardant role together with the char layer, while improving the overall stability of the silicone char layer.

[0053] In a preferred embodiment, the mass ratio of ammonium polyphosphate, resorcinol bis(diphenyl phosphate), and zinc borate is (3-5):(2-4):1.

[0054] In a preferred embodiment, the crosslinking agent is selected from one or more of acyloxysilane crosslinking agents, ketoxime silane crosslinking agents, and alkoxysilane crosslinking agents. Acyloxysilane crosslinking agents may be methyltriacetoxysilane, vinyltriacetoxysilane, etc.; ketoxime silane crosslinking agents may be methyltriketoxime silane, vinyltriketoxime silane, or methyltributanone oxime silane, etc.; alkoxysilane crosslinking agents may be methyltrimethoxysilane, methyltriethoxysilane, or tetraethyl orthosilicate, etc. In a specific embodiment, the crosslinking agent is methyltributanone oxime silane.

[0055] Preferably, the catalyst is selected from one or more of dibutyltin dilaurate, dibutyltin diacetate, stannous octoate, dioctyltin dilaurate, and dibutyltin acetylacetonate. In one specific embodiment, the catalyst is dibutyltin dilaurate.

[0056] Preferably, the silane coupling agent may be selected from any one or more of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-aminoethyl γ-aminopropyltrimethoxysilane, N-β-aminoethyl γ-aminopropyltriethoxysilane, γ-glycidyl etheroxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, 3-isocyanate-propyltrimethoxysilane, glycidyltriethoxysilane, and mercaptopropyltrimethoxysilane.

[0057] In a preferred embodiment, the reinforcing agent is hydrophobic fumed silica. The particle size of the fumed silica is 1-100 nm.

[0058] In a preferred embodiment, the viscosity of α,ω-dihydroxypolydimethylsiloxane can be 10,000-50,000 mPa·s (25°C), the viscosity of dimethyl silicone oil can be 100-500 mPa·s (25°C), and the viscosity of phenylmethyl silicone oil can be 500-1200 mPa·s (25°C).

[0059] In a second aspect, this application provides a method for preparing a flame-retardant silicone sealant, comprising the following steps:

[0060] Add α,ω-dihydroxy polydimethylsiloxane, dimethyl silicone oil, phenylmethyl silicone oil, and reinforcing agent to a planetary mixer, stir at low speed of 50-100 rpm for 5-10 minutes under vacuum, and then stir at high speed of 300-500 rpm for 30-40 minutes to obtain the base material.

[0061] Add flame retardant and modified ceramic powder, stir at low speed of 50-100 rpm for 10-20 minutes, then stir at high speed for 40-60 minutes; then add crosslinking agent, coupling agent and catalyst, stir at low speed of 30-50 rpm for 10-15 minutes, then degas under vacuum to obtain silicone sealant.

[0062] The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments; and the reaction apparatus, monomer compounds, etc. involved in the following embodiments are all commercially available. Specifically, the raw materials that can be used in the following embodiments include:

[0063] α,ω-Dihydroxypolydimethylsiloxane (viscosity 20000 mPa·s, 25℃), Wacker FD20; dimethyl silicone oil (viscosity 300 mPa·s, 25℃), ordered from Jinan Longcheng Organosilicon Co., Ltd.; phenylmethyl silicone oil (viscosity 1000 mPa·s, 25℃), model IOTA BJ510; hydrophobic fumed silica, model AEROSIL R106 (average particle size 7 nm); silicon nitride (average particle size 0.8 μm), ordered from Zhongke Xinci; zirconium dioxide (average particle size 2 μm), ordered from Xi'an Bona Materials Technology Co., Ltd.; alumina (average particle size 6 μm), ordered from Xi'an Bona Materials Technology Co., Ltd.; boehmite (average particle size 4 μm), ordered from Zhongshan Laipeng New Materials Co., Ltd.; sodium polystyrene sulfonate, model Jiyesheng A00280; polyethyleneimine, model BASF Lupasol® PR. 8515; Ammonium polyphosphate, model HT-208 APP200; Resorcinol bis(diphenyl phosphate), model Wansheng WSFR-RDP; Zinc borate, model HT-207.

[0064] Example

[0065] Example 1

[0066] This embodiment discloses a flame-retardant silicone sealant, the preparation method of which is as follows:

[0067] (1) Modified ceramic micro powder

[0068] Silicon nitride, zirconium dioxide, alumina, and boehmite were ball-milled and mixed in a mass ratio of 1:1:6:2 to obtain mixed ceramic micro powder.

[0069] Take 200g of mixed ceramic micro powder and spread it evenly in a plasma surface treatment machine. Use NH3 to perform plasma treatment to obtain activated ceramic micro powder.

[0070] The activated ceramic micro powder was added to water at a solid-liquid ratio of 1:5 (g / mL), the pH was adjusted to 5-6, and the mixture was ultrasonically dispersed at 40℃ for 20 min to obtain a primary suspension.

[0071] 10g of sodium polystyrene sulfonate was added to water to prepare a sodium polystyrene sulfonate solution of 10mg / ml. The sodium polystyrene sulfonate solution was added to the primary suspension under stirring. The pH was adjusted to 5-6. The mixture was stirred and reacted at room temperature for 2 hours. After centrifugation, the mixture was washed with 0.05mol / L sodium chloride aqueous solution to obtain primary particles.

[0072] The primary particles were added to water at a solid-liquid ratio of 1:5 (g / mL) and ultrasonically dispersed at 40℃ for 20 min to obtain a secondary suspension. 15 g of polyethyleneimine was added to water to prepare a 15 mg / mL polyethyleneimine solution, and the pH was adjusted to 5-6. The solution was stirred until fully dissolved and homogeneous. The polyethyleneimine solution was added to the secondary suspension at a uniform rate while stirring, and the mixture was stirred at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain the secondary particles.

[0073] 16g of KH560 silane coupling agent was added to a 95% (v / v) aqueous ethanol solution to prepare a 5% (w / w) siloxane solution, and stirred for 20 min. Secondary particles were added to ethanol at a solid-liquid ratio of 1:2 (g / mL), dispersed evenly, and then mixed with the siloxane solution. Triethylamine was added to adjust the pH to 8-9. The mixture was stirred and reacted at 60℃ under a nitrogen atmosphere for 6 h. After centrifugation, the mixture was washed three times, dried under vacuum at 45℃, and heat-treated at 100℃ for 30 min under a nitrogen atmosphere to obtain modified ceramic micropowder.

[0074] (2) Silicone sealant

[0075] 1000g of α,ω-dihydroxypolydimethylsiloxane, 260g of dimethyl silicone oil, 150g of phenylmethyl silicone oil, and 100g of hydrophobic fumed silica were added to a planetary mixer and stirred at 50 rpm for 10 minutes under vacuum conditions of -0.090 to 0.092 MPa, followed by high-speed stirring at 500 rpm for 30 minutes to obtain the base material.

[0076] Add 200g ammonium polyphosphate, 150g resorcinol bis(diphenyl phosphate), 50g zinc borate, and 100g modified ceramic powder. Stir at low speed of 50rpm for 20 minutes under vacuum conditions of -0.090 to 0.092 MPa, and then stir at high speed of 500rpm for 45 minutes.

[0077] Add 60g of crosslinking agent methyl tributanone oxime silane, 20g of coupling agent KH560, and 4g of catalyst dibutyltin dilaurate. Stir at low speed of 30-50 rpm for 10-15 minutes, degas under vacuum, and dispense to obtain silicone sealant.

[0078] Example 2

[0079] This embodiment discloses a flame-retardant silicone sealant, the preparation method of which is as follows:

[0080] (1) Modified ceramic micro powder

[0081] Silicon nitride, zirconium dioxide, alumina, and boehmite were ball-milled and mixed in a mass ratio of 1.5:0.5:5:3 to obtain mixed ceramic micro powder.

[0082] Take 200g of mixed ceramic micro powder and spread it evenly in a plasma surface treatment machine. Use NH3 to perform plasma treatment to obtain activated ceramic micro powder.

[0083] Activated ceramic micropowder was added to water at a solid-liquid ratio of 1:5 (g / mL), the pH was adjusted to 5-6, and the mixture was ultrasonically dispersed at 40℃ for 20 min to obtain a primary suspension. 10 g of sodium polystyrene sulfonate was added to water to prepare a 10 mg / mL sodium polystyrene sulfonate solution. The sodium polystyrene sulfonate solution was added to the primary suspension while stirring, and the mixture was stirred and reacted at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain primary particles.

[0084] The primary particles were added to water at a solid-liquid ratio of 1:5 (g / mL) and ultrasonically dispersed at 40℃ for 20 min to obtain a secondary suspension. 15 g of polyethyleneimine was added to water to prepare a 15 mg / mL polyethyleneimine solution, and the pH was adjusted to 5-6. The solution was stirred until fully dissolved and homogeneous. The polyethyleneimine solution was added to the secondary suspension at a uniform rate while stirring, and the mixture was stirred at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain the secondary particles.

[0085] 16g of KH560 silane coupling agent was added to a 95% (v / v) aqueous ethanol solution to prepare a 5% (w / w) siloxane solution, and stirred for 20 min. Secondary particles were added to ethanol at a solid-liquid ratio of 1:2 (g / mL), dispersed evenly, and then mixed with the siloxane solution. Triethylamine was added to adjust the pH to 8-9. The mixture was stirred and reacted at 60℃ under a nitrogen atmosphere for 6 h. After centrifugation, the mixture was washed three times, dried under vacuum at 45℃, and heat-treated at 100℃ for 30 min under a nitrogen atmosphere to obtain modified ceramic micropowder.

[0086] (2) Silicone sealant

[0087] 1000g of α,ω-dihydroxypolydimethylsiloxane, 250g of dimethyl silicone oil, 200g of phenylmethyl silicone oil, and 100g of hydrophobic fumed silica were added to a planetary mixer and stirred at 50 rpm for 10 minutes under vacuum conditions of -0.090 to 0.092 MPa, followed by high-speed stirring at 500 rpm for 30 minutes to obtain the base material.

[0088] Add 180g ammonium polyphosphate, 120g resorcinol bis(diphenyl phosphate), 50g zinc borate, and 120g modified ceramic powder. Stir at low speed of 50rpm for 20 minutes under vacuum conditions of -0.090 to 0.092 MPa, and then stir at high speed of 500rpm for 45 minutes.

[0089] Add 65g of crosslinking agent methyl tributanone oxime silane, 20g of coupling agent KH560, and 4g of catalyst dibutyltin dilaurate. Stir at low speed of 30-50 rpm for 10-15 minutes, degas under vacuum, and dispense to obtain silicone sealant.

[0090] Example 3

[0091] This embodiment discloses a flame-retardant silicone sealant, the preparation method of which is as follows:

[0092] (1) Modified ceramic micro powder

[0093] Take 200g of alumina and spread it evenly in a plasma surface treatment machine. Use NH3 to perform plasma treatment to obtain activated ceramic micro powder.

[0094] Activated ceramic micropowder was added to water at a solid-liquid ratio of 1:5 (g / mL), the pH was adjusted to 5-6, and the mixture was ultrasonically dispersed at 40℃ for 20 min to obtain a primary suspension. 10 g of sodium polystyrene sulfonate was added to water to prepare a 10 mg / mL sodium polystyrene sulfonate solution. The sodium polystyrene sulfonate solution was added to the primary suspension while stirring, and the mixture was stirred and reacted at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain primary particles.

[0095] The primary particles were added to water at a solid-liquid ratio of 1:5 (g / mL) and ultrasonically dispersed at 40℃ for 20 min to obtain a secondary suspension. 15 g of polyethyleneimine was added to water to prepare a 15 mg / mL polyethyleneimine solution, and the pH was adjusted to 5-6. The solution was stirred until fully dissolved and homogeneous. The polyethyleneimine solution was added to the secondary suspension at a uniform rate while stirring, and the mixture was stirred at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain the secondary particles.

[0096] 16g of KH560 silane coupling agent was added to a 95% (v / v) aqueous ethanol solution to prepare a 5% (w / w) siloxane solution. The mixture was stirred for 20 min. Secondary particles were added to the ethanol at a solid-liquid ratio of 1:2 (g / mL). After being dispersed evenly, the particles were mixed with the siloxane solution. Triethylamine was added to adjust the pH to 8-9. The mixture was stirred and reacted at 60℃ under a nitrogen atmosphere for 6 h. After centrifugation, the particles were washed three times, dried under vacuum at 45℃, and heat-treated at 100℃ for 30 min under a nitrogen atmosphere to obtain modified ceramic micropowder.

[0097] (2) Silicone sealant

[0098] 1000g of α,ω-dihydroxypolydimethylsiloxane, 260g of dimethyl silicone oil, 150g of phenylmethyl silicone oil, and 100g of hydrophobic fumed silica were added to a planetary mixer and stirred at 50 rpm for 10 minutes under vacuum conditions of -0.090 to 0.092 MPa, followed by high-speed stirring at 500 rpm for 30 minutes to obtain the base material.

[0099] Add 200g ammonium polyphosphate, 150g resorcinol bis(diphenyl phosphate), 50g zinc borate, and 100g modified ceramic powder. Stir at low speed of 50rpm for 20 minutes under vacuum conditions of -0.090 to 0.092 MPa, and then stir at high speed of 500rpm for 45 minutes.

[0100] Add 60g of crosslinking agent methyl tributanone oxime silane, 20g of coupling agent KH560, and 4g of catalyst dibutyltin dilaurate. Stir at low speed of 30-50 rpm for 10-15 minutes, degas under vacuum, and dispense to obtain silicone sealant.

[0101] Example 4

[0102] This embodiment discloses a flame-retardant silicone sealant, the preparation method of which is as follows:

[0103] (1) Modified ceramic micro powder

[0104] Zirconia, alumina and boehmite were ball-milled and mixed in a mass ratio of 1:7:2 to obtain mixed ceramic micro powder;

[0105] Take 200g of the mixed ceramic micro powder and spread it evenly in a plasma surface treatment machine. Use NH3 for plasma treatment to obtain activated ceramic micro powder.

[0106] Activated ceramic micropowder was added to water at a solid-liquid ratio of 1:5 (g / mL), the pH was adjusted to 5-6, and the mixture was ultrasonically dispersed at 40℃ for 20 min to obtain a primary suspension. 10 g of sodium polystyrene sulfonate was added to water to prepare a 10 mg / mL sodium polystyrene sulfonate solution. The sodium polystyrene sulfonate solution was added to the primary suspension while stirring, and the mixture was stirred and reacted at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain primary particles.

[0107] The primary particles were added to water at a solid-liquid ratio of 1:5 (g / mL) and ultrasonically dispersed at 40℃ for 20 min to obtain a secondary suspension. 15 g of polyethyleneimine was added to water to prepare a 15 mg / mL polyethyleneimine solution, and the pH was adjusted to 5-6. The solution was stirred until fully dissolved and homogeneous. The polyethyleneimine solution was added to the secondary suspension at a uniform rate while stirring, and the mixture was stirred at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain the secondary particles.

[0108] 16g of KH560 silane coupling agent was added to a 95% (v / v) aqueous ethanol solution to prepare a 5% (w / w) siloxane solution. Secondary particles were added to the ethanol at a solid-liquid ratio of 1:2 (g / mL), dispersed evenly, and then mixed with the siloxane solution. Triethylamine was added to adjust the pH to 8-9. The mixture was stirred and reacted at 60℃ under a nitrogen atmosphere for 6 hours. After centrifugation, the mixture was washed three times, dried under vacuum at 45℃, and heat-treated at 100℃ for 30 minutes under a nitrogen atmosphere to obtain modified ceramic micropowder.

[0109] (2) Silicone sealant

[0110] 1000g of α,ω-dihydroxypolydimethylsiloxane, 260g of dimethyl silicone oil, 150g of phenylmethyl silicone oil, and 100g of hydrophobic fumed silica were added to a planetary mixer and stirred at 50 rpm for 10 minutes under vacuum conditions of -0.090 to 0.092 MPa, followed by high-speed stirring at 500 rpm for 30 minutes to obtain the base material.

[0111] Add 200g ammonium polyphosphate, 150g resorcinol bis(diphenyl phosphate), 50g zinc borate, and 100g modified ceramic powder. Stir at low speed of 50rpm for 20 minutes under vacuum conditions of -0.090 to 0.092 MPa, and then stir at high speed of 500rpm for 45 minutes.

[0112] Add 60g of crosslinking agent methyl tributanone oxime silane, 20g of coupling agent KH560, and 4g of catalyst dibutyltin dilaurate. Stir at low speed of 30-50 rpm for 10-15 minutes, degas under vacuum, and dispense to obtain silicone sealant.

[0113] Example 5

[0114] This embodiment discloses a flame-retardant silicone sealant, the preparation method of which is as follows:

[0115] (1) Modified ceramic micro powder

[0116] Silicon nitride, alumina, and boehmite were ball-milled and mixed in a mass ratio of 1:7:2 to obtain mixed ceramic micro powder.

[0117] Take 200g of the mixed ceramic micro powder and spread it evenly in a plasma surface treatment machine. Use NH3 for plasma treatment to obtain activated ceramic micro powder.

[0118] Activated ceramic micropowder was added to water at a solid-liquid ratio of 1:5 (g / mL), the pH was adjusted to 5-6, and the mixture was ultrasonically dispersed at 40℃ for 20 min to obtain a primary suspension. 10 g of sodium polystyrene sulfonate was added to water to prepare a 10 mg / mL sodium polystyrene sulfonate solution. The sodium polystyrene sulfonate solution was added to the primary suspension while stirring, the pH was adjusted to 5-6, and the mixture was stirred and reacted at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain primary particles.

[0119] The primary particles were added to water at a solid-liquid ratio of 1:5 (g / mL) and ultrasonically dispersed at 40℃ for 20 min to obtain a secondary suspension. 15 g of polyethyleneimine was added to water to prepare a 15 mg / mL polyethyleneimine solution, and the pH was adjusted to 5-6. The solution was stirred until fully dissolved and homogeneous. The polyethyleneimine solution was added to the secondary suspension at a uniform rate while stirring, and the mixture was stirred at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain the secondary particles.

[0120] 16g of KH560 silane coupling agent was added to a 95% (v / v) aqueous ethanol solution to prepare a 5% (w / w) siloxane solution. Secondary particles were added to the ethanol at a solid-liquid ratio of 1:2 (g / mL), dispersed evenly, and then mixed with the siloxane solution. Triethylamine was added to adjust the pH to 8-9. The mixture was stirred and reacted at 60℃ under a nitrogen atmosphere for 6 hours. After centrifugation, the mixture was washed three times, dried under vacuum at 45℃, and heat-treated at 100℃ for 30 minutes under a nitrogen atmosphere to obtain modified ceramic micropowder.

[0121] (2) Silicone sealant

[0122] 1000g of α,ω-dihydroxypolydimethylsiloxane, 260g of dimethyl silicone oil, 150g of phenylmethyl silicone oil, and 100g of hydrophobic fumed silica were added to a planetary mixer and stirred at 50 rpm for 10 minutes under vacuum conditions of -0.090 to 0.092 MPa, followed by high-speed stirring at 500 rpm for 30 minutes to obtain the base material.

[0123] Add 200g ammonium polyphosphate, 150g resorcinol bis(diphenyl phosphate), 50g zinc borate, and 100g modified ceramic powder. Stir at low speed of 50rpm for 20 minutes under vacuum conditions of -0.090 to 0.092 MPa, and then stir at high speed of 500rpm for 45 minutes.

[0124] Add 60g of crosslinking agent methyl tributanone oxime silane, 20g of coupling agent KH560, and 4g of catalyst dibutyltin dilaurate. Stir at low speed of 30-50 rpm for 10-15 minutes, degas under vacuum, and dispense to obtain silicone sealant.

[0125] Example 6

[0126] This embodiment discloses a flame-retardant silicone sealant, the preparation method of which is as follows:

[0127] (1) Modified ceramic micro powder

[0128] Silicon nitride, zirconium dioxide, and alumina were ball-milled and mixed in a mass ratio of 1:1:8 to obtain mixed ceramic micro powder;

[0129] Take 200g of the mixed ceramic micro powder and spread it evenly in a plasma surface treatment machine. Use NH3 for plasma treatment to obtain activated ceramic micro powder.

[0130] Activated ceramic micropowder was added to water at a solid-liquid ratio of 1:5 (g / mL), the pH was adjusted to 5-6, and the mixture was ultrasonically dispersed at 40℃ for 20 min to obtain a primary suspension. 10 g of sodium polystyrene sulfonate was added to water to prepare a 10 mg / mL sodium polystyrene sulfonate solution. The sodium polystyrene sulfonate solution was added to the primary suspension while stirring, and the mixture was stirred and reacted at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain primary particles.

[0131] The primary particles were added to water at a solid-liquid ratio of 1:5 (g / mL) and ultrasonically dispersed at 40℃ for 20 min to obtain a secondary suspension. 15 g of polyethyleneimine was added to water to prepare a 15 mg / mL polyethyleneimine solution, and the pH was adjusted to 5-6. The solution was stirred until fully dissolved and homogeneous. The polyethyleneimine solution was added to the secondary suspension at a uniform rate while stirring, and the mixture was stirred at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain the secondary particles.

[0132] 16g of KH560 silane coupling agent was added to a 95% (v / v) aqueous ethanol solution to prepare a 5% (w / w) siloxane solution. The mixture was stirred for 20 min. Secondary particles were added to the ethanol at a solid-liquid ratio of 1:2 (g / mL). After being dispersed evenly, the particles were mixed with the siloxane solution. Triethylamine was added to adjust the pH to 8-9. The mixture was stirred and reacted at 60℃ under a nitrogen atmosphere for 6 h. After centrifugation, the particles were washed three times, dried under vacuum at 45℃, and heat-treated at 100℃ for 30 min under a nitrogen atmosphere to obtain modified ceramic micropowder.

[0133] (2) Silicone sealant

[0134] 1000g of α,ω-dihydroxypolydimethylsiloxane, 260g of dimethyl silicone oil, 150g of phenylmethyl silicone oil, and 100g of hydrophobic fumed silica were added to a planetary mixer and stirred at 50 rpm for 10 minutes under vacuum conditions of -0.090 to 0.092 MPa, followed by high-speed stirring at 500 rpm for 30 minutes to obtain the base material.

[0135] Add 200g ammonium polyphosphate, 150g resorcinol bis(diphenyl phosphate), 50g zinc borate, and 100g modified ceramic powder. Stir at low speed of 50rpm for 20 minutes under vacuum conditions of -0.090 to 0.092 MPa, and then stir at high speed of 500rpm for 45 minutes.

[0136] Add 60g of crosslinking agent methyl tributanone oxime silane, 20g of coupling agent KH560, and 4g of catalyst dibutyltin dilaurate. Stir at low speed of 30-50 rpm for 10-15 minutes, degas under vacuum, and dispense to obtain silicone sealant.

[0137] Example 7

[0138] This embodiment discloses a flame-retardant silicone sealant, the preparation method of which is as follows:

[0139] (1) Modified ceramic micro powder

[0140] Silicon nitride, zirconium dioxide, alumina, and boehmite were ball-milled and mixed in a mass ratio of 1:1:6:2 to obtain mixed ceramic micro powder.

[0141] Take 200g of the mixed ceramic micro powder and spread it evenly in a plasma surface treatment machine. Use NH3 for plasma treatment to obtain activated ceramic micro powder.

[0142] Activated ceramic micropowder was added to water at a solid-liquid ratio of 1:5 (g / mL), the pH was adjusted to 5-6, and the mixture was ultrasonically dispersed at 40℃ for 20 min to obtain a primary suspension. 10 g of sodium polystyrene sulfonate was added to water to prepare a 10 mg / mL sodium polystyrene sulfonate solution. The sodium polystyrene sulfonate solution was added to the primary suspension while stirring, and the mixture was stirred and reacted at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain primary particles.

[0143] The primary particles were added to water at a solid-liquid ratio of 1:5 (g / mL) and ultrasonically dispersed at 40℃ for 20 min to obtain a secondary suspension. 15 g of polyethyleneimine was added to water to prepare a 15 mg / mL polyethyleneimine solution, and the pH was adjusted to 5-6. The solution was stirred until fully dissolved and homogeneous. The polyethyleneimine solution was added to the secondary suspension at a uniform rate while stirring, and the mixture was stirred at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain the secondary particles.

[0144] 16g of KH560 silane coupling agent was added to a 95% (v / v) aqueous ethanol solution to prepare a 5% (w / w) siloxane solution. The mixture was stirred for 20 min. Secondary particles were added to the ethanol at a solid-liquid ratio of 1:2 (g / mL). After being dispersed evenly, the particles were mixed with the siloxane solution. Triethylamine was added to adjust the pH to 8-9. The mixture was stirred and reacted at 60℃ under a nitrogen atmosphere for 6 h. After centrifugation, the particles were washed three times, dried under vacuum at 45℃, and heat-treated at 100℃ for 30 min under a nitrogen atmosphere to obtain modified ceramic micropowder.

[0145] (2) Silicone sealant

[0146] 1000g of α,ω-dihydroxypolydimethylsiloxane, 260g of dimethyl silicone oil, 150g of phenylmethyl silicone oil, and 100g of hydrophobic fumed silica were added to a planetary mixer and stirred at 50 rpm for 10 minutes under vacuum conditions of -0.090 to 0.092 MPa, followed by high-speed stirring at 500 rpm for 30 minutes to obtain the base material.

[0147] Add 250g ammonium polyphosphate, 150g resorcinol bis(diphenyl phosphate), and 100g modified ceramic powder. Stir at low speed of 50rpm for 20 minutes under vacuum conditions of -0.090 to 0.092 MPa, and then stir at high speed of 500rpm for 45 minutes.

[0148] Add 60g of crosslinking agent methyl tributanone oxime silane, 20g of coupling agent KH560, and 4g of catalyst dibutyltin dilaurate. Stir at low speed of 30-50 rpm for 10-15 minutes, degas under vacuum, and dispense to obtain silicone sealant.

[0149] Example 8

[0150] This embodiment discloses a flame-retardant silicone sealant, the preparation method of which is as follows:

[0151] (1) Modified ceramic micro powder

[0152] Silicon nitride, zirconium dioxide, alumina, and boehmite were ball-milled and mixed in a mass ratio of 1:1:6:2 to obtain mixed ceramic micro powder.

[0153] Take 200g of the mixed ceramic micro powder and spread it evenly in a plasma surface treatment machine. Use NH3 for plasma treatment to obtain activated ceramic micro powder.

[0154] Activated ceramic micropowder was added to water at a solid-liquid ratio of 1:5 (g / mL), the pH was adjusted to 5-6, and the mixture was ultrasonically dispersed at 40℃ for 20 min to obtain a primary suspension. 10 g of sodium polystyrene sulfonate was added to water to prepare a 10 mg / mL sodium polystyrene sulfonate solution. The sodium polystyrene sulfonate solution was added to the primary suspension while stirring, and the mixture was stirred and reacted at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain primary particles.

[0155] The primary particles were added to water at a solid-liquid ratio of 1:5 (g / mL) and ultrasonically dispersed at 40℃ for 20 min to obtain a secondary suspension. 15 g of polyethyleneimine was added to water to prepare a 15 mg / mL polyethyleneimine solution, and the pH was adjusted to 5-6. The solution was stirred until fully dissolved and homogeneous. The polyethyleneimine solution was added to the secondary suspension at a uniform rate while stirring, and the mixture was stirred at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain the secondary particles.

[0156] 16g of KH560 silane coupling agent was added to a 95% (v / v) aqueous ethanol solution to prepare a 5% (w / w) siloxane solution. Secondary particles were added to the ethanol at a solid-liquid ratio of 1:2 (g / mL), dispersed evenly, and then mixed with the siloxane solution. Triethylamine was added to adjust the pH to 8-9. The mixture was stirred and reacted at 60℃ under a nitrogen atmosphere for 6 hours. After centrifugation, the mixture was washed three times, dried under vacuum at 45℃, and heat-treated at 100℃ for 30 minutes under a nitrogen atmosphere to obtain modified ceramic micropowder.

[0157] (2) Silicone sealant

[0158] 1000g of α,ω-dihydroxypolydimethylsiloxane, 260g of dimethyl silicone oil, 150g of phenylmethyl silicone oil, and 100g of hydrophobic fumed silica were added to a planetary mixer and stirred at 50 rpm for 10 minutes under vacuum conditions of -0.090 to 0.092 MPa, followed by high-speed stirring at 500 rpm for 30 minutes to obtain the base material.

[0159] Add 350g ammonium polyphosphate, 50g zinc borate, and 100g modified ceramic powder. Stir at low speed of 50rpm for 20 minutes under vacuum conditions of -0.090 to 0.092 MPa, and then stir at high speed of 500rpm for 45 minutes.

[0160] Add 60g of crosslinking agent methyl tributanone oxime silane, 20g of coupling agent KH560, and 4g of catalyst dibutyltin dilaurate. Stir at low speed of 30-50 rpm for 10-15 minutes, degas under vacuum, and dispense to obtain silicone sealant.

[0161] Comparative Example

[0162] Comparative Example 1

[0163] Compared with Example 1, this comparative example did not contain any modified ceramic micropowder, specifically including:

[0164] 1000g of α,ω-dihydroxypolydimethylsiloxane, 260g of dimethyl silicone oil, 150g of phenylmethyl silicone oil, and 100g of hydrophobic fumed silica were added to a planetary mixer and stirred at 50 rpm for 10 minutes under vacuum conditions of -0.090 to 0.092 MPa, followed by high-speed stirring at 500 rpm for 30 minutes to obtain the base material.

[0165] Add 200g ammonium polyphosphate, 150g resorcinol bis(diphenyl phosphate), and 50g zinc borate. Stir at low speed of 50rpm for 20 minutes under vacuum conditions of -0.090 to 0.092 MPa, and then stir at high speed of 500rpm for 45 minutes.

[0166] Add 60g of crosslinking agent methyl tributanone oxime silane, 20g of coupling agent KH560, and 4g of catalyst dibutyltin dilaurate. Stir at low speed of 30-50 rpm for 10-15 minutes, degas under vacuum, and dispense to obtain silicone sealant.

[0167] Comparative Example 2

[0168] Compared with Comparative Example 1, this comparative example only uses silane coupling agents to modify ceramic micropowder, specifically including:

[0169] (1) Modified ceramic micro powder

[0170] Silicon nitride, zirconium dioxide, alumina, and boehmite were ball-milled and mixed in a mass ratio of 1:1:6:2 to obtain mixed ceramic micro powder.

[0171] 16g of KH560 silane coupling agent was added to a 95% (v / v) ethanol solution to prepare a 5% (w / w) siloxane solution, and stirred for 20 min. 200g of mixed ceramic micropowder was added to ethanol at a solid-liquid ratio of 1:2 (g / mL), dispersed evenly, and then mixed with the siloxane solution. The mixture was stirred and reacted at 60℃ under a nitrogen atmosphere for 2 h. After centrifugation, the mixture was washed three times and dried under vacuum at 65℃ to obtain the modified ceramic micropowder.

[0172] (2) Silicone sealant

[0173] 1000g of α,ω-dihydroxypolydimethylsiloxane, 260g of dimethyl silicone oil, 150g of phenylmethyl silicone oil, and 100g of hydrophobic fumed silica were added to a planetary mixer and stirred at 50 rpm for 10 minutes under vacuum conditions of -0.090 to 0.092 MPa, followed by high-speed stirring at 500 rpm for 30 minutes to obtain the base material.

[0174] Add 200g ammonium polyphosphate, 150g resorcinol bis(diphenyl phosphate), 50g zinc borate, and 100g modified ceramic powder. Stir at low speed of 50rpm for 20 minutes under vacuum conditions of -0.090 to 0.092 MPa, and then stir at high speed of 500rpm for 45 minutes.

[0175] Add 60g of crosslinking agent methyl tributanone oxime silane, 20g of coupling agent KH560, and 4g of catalyst dibutyltin dilaurate. Stir at low speed of 30-50 rpm for 10-15 minutes, degas under vacuum, and dispense to obtain silicone sealant.

[0176] Comparative Example 3

[0177] The only difference between this comparative example and Example 1 is that only a polyelectrolyte layer is used to modify the ceramic micropowder, specifically including:

[0178] (1) Modified ceramic micro powder

[0179] Silicon nitride, zirconium dioxide, alumina, and boehmite were ball-milled and mixed in a mass ratio of 1:1:6:2 to obtain mixed ceramic micro powder.

[0180] Take 200g of the mixed ceramic micro powder and spread it evenly in a plasma surface treatment machine. Use NH3 for plasma treatment to obtain activated ceramic micro powder.

[0181] Activated ceramic micropowder was added to water at a solid-liquid ratio of 1:5 (g / mL), the pH was adjusted to 5-6, and the mixture was ultrasonically dispersed at 40℃ for 20 min to obtain a primary suspension. 10 g of sodium polystyrene sulfonate was added to water to prepare a 10 mg / mL sodium polystyrene sulfonate solution. The sodium polystyrene sulfonate solution was added to the primary suspension while stirring, and the mixture was stirred and reacted at room temperature for 2 h. After centrifugation, the mixture was washed with a 0.05 mol / L sodium chloride aqueous solution to obtain primary particles.

[0182] The primary particles were added to water at a solid-liquid ratio of 1:5 (g / mL) and ultrasonically dispersed at 40℃ for 20 min to obtain a secondary suspension. 15g of polyethyleneimine was added to water to prepare a 15mg / ml polyethyleneimine solution, and the pH was adjusted to 5-6. The solution was stirred until fully dissolved and homogeneous. The polyethyleneimine solution was added to the secondary suspension at a uniform rate while stirring, and the mixture was stirred at room temperature for 2 h. After centrifugation, the mixture was washed with 0.05mol / L sodium chloride aqueous solution and vacuum dried at 45℃ to obtain modified ceramic micro powder.

[0183] (2) Silicone sealant

[0184] 1000g of α,ω-dihydroxypolydimethylsiloxane, 260g of dimethyl silicone oil, 150g of phenylmethyl silicone oil, and 100g of hydrophobic fumed silica were added to a planetary mixer and stirred at 50 rpm for 10 minutes under a vacuum of 0.090-0.092 MPa, followed by high-speed stirring at 500 rpm for 30 minutes to obtain the base material.

[0185] Add 200g ammonium polyphosphate, 150g resorcinol bis(diphenyl phosphate), 50g zinc borate, and 100g modified ceramic powder. Stir at low speed of 50rpm for 20 minutes under vacuum of 0.090-0.092 MPa, and then stir at high speed of 500rpm for 45 minutes.

[0186] Add 60g of crosslinking agent methyl tributanone oxime silane, 20g of coupling agent KH560, and 4g of catalyst dibutyltin dilaurate. Stir at low speed of 30-50 rpm for 10-15 minutes, degas under vacuum, and dispense to obtain silicone sealant.

[0187] Performance testing

[0188] The silicone sealants from each embodiment and comparative example were injected into standard molds to prepare samples (150mm×15mm×5mm). These samples were cured for 28 days at 23(±2)℃ and 50(±10)% relative humidity, and then dried in an oven at 65℃ for 72 hours. The flame retardancy rating was tested according to standard GB / T 24267-2009, the oxygen index was tested according to standard GB / T 2406-2008, and the unnotched impact strength was tested according to standard GB / T1843-2008.

[0189] Take the silicone sealant from each example and comparative example, and prepare fireproof sealing material specimens for gaps according to standard GB 23864-2009. Curing them for 28 days at a temperature of 23 (±2)℃ and a relative humidity of 50 (±10)% will be carried out for fire resistance integrity testing.

[0190] Glass-aluminum sheet H-shaped bonding specimens were prepared according to standard GB / T 13477.8-2017, and cured for 28 days at a temperature of 23 (±2)℃ and a relative humidity of 50 (±10)% before the maximum tensile strength was tested.

[0191] The test results are summarized in Table 1.

[0192] Table 1

[0193]

[0194] As can be seen from Examples 1 and 2, the silicone sealant prepared by the method disclosed in this application has excellent flame retardancy and fire resistance integrity, as well as high mechanical strength and toughness.

[0195] As can be seen from Examples 1, 3-6, and Comparative Example 1, and Table 1, the use of silicon nitride, zirconium dioxide, alumina, and boehmite in the compounding process results in a synergistic effect among the ceramic micropowders, which improves the fire resistance of the silicone sealant while also giving it better tensile strength and impact strength.

[0196] As can be seen from Example 1, Comparative Examples 2-3 and Table 1, the use of polyelectrolyte coating and silanization synergistic modification helps to further improve the interfacial bonding between ceramic micropowder and silicone matrix, promotes the ceramization of flame retardant and ceramic powder, and helps to further improve the fire resistance and mechanical properties of silicone.

[0197] As can be seen from Examples 1 and 7-8 and Table 1, the combination of three flame retardants can achieve a significant improvement in flame retardant effect.

[0198] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A flame-retardant silicone sealant, characterized in that, The raw materials include the following parts by weight: 100 parts of α,ω-dihydroxypolydimethylsiloxane, 10-30 parts of dimethyl silicone oil, 15-25 parts of phenylmethyl silicone oil, 4-10 parts of crosslinking agent, 0.2-0.5 parts of catalyst, 1-2 parts of silane coupling agent, 30-50 parts of flame retardant, 8-12 parts of reinforcing agent, and 5-20 parts of modified ceramic micro powder; The flame retardant includes ammonium polyphosphate, resorcinol bis(diphenyl phosphate) and zinc borate; The modified ceramic micro powder includes ceramic micro powder and a surface shell layer, the shell layer specifically including: a sodium polystyrene sulfonate-polyethyleneimine polymer coating layer formed by polyelectrolyte self-assembly, and epoxy siloxane grafted onto the surface of the polymer coating layer; The mass ratio of ammonium polyphosphate, resorcinol bis(diphenyl phosphate), and zinc borate is (3-5):(2-4):1; The ceramic micro powder comprises silicon nitride, zirconium dioxide, alumina, and boehmite in a mass ratio of (1-2):(0.5-1.5):(4-6):(2-4).

2. The flame-retardant silicone sealant according to claim 1, characterized in that, The silicon nitride has a particle size of 0.5-2 μm; the zirconium dioxide has a particle size of 1-4 μm; the alumina has a particle size of 2-12 μm; and the boehmite has a particle size of 2-12 μm.

3. The flame-retardant silicone sealant according to claim 1, characterized in that, The mass ratio of the ceramic micro powder, sodium polystyrene sulfonate, polyethyleneimine, and epoxy siloxane is 100:(4-6):(5-8):(3-10).

4. The flame-retardant silicone sealant according to claim 1, characterized in that, The epoxy siloxane is γ-glycidoxypropyltrimethoxysilane or γ-glycidoxypropyltriethoxysilane.

5. The flame-retardant silicone sealant according to claim 1, characterized in that, The viscosity of the α,ω-dihydroxy polydimethylsiloxane at 25°C is 10000-50000 mPa·s, the viscosity of the dimethyl silicone oil at 25°C is 100-500 mPa·s, and the viscosity of the phenylmethyl silicone oil at 25°C is 500-1200 mPa·s.

6. The flame-retardant silicone sealant according to claim 1, characterized in that, The reinforcing agent is hydrophobic fumed silica, and / or the crosslinking agent is selected from one or more of acyloxysilane crosslinking agents, ketoxime silane crosslinking agents, and alkoxysilane crosslinking agents, and / or the catalyst is selected from one or more of dibutyltin dilaurate, dibutyltin diacetate, stannous octoate, dioctyltin dilaurate, and dibutyltin acetylacetonate.

7. A method for preparing a flame-retardant silicone sealant as described in any one of claims 1-6, characterized in that, Includes the following steps: Add α,ω-dihydroxypolydimethylsiloxane, dimethyl silicone oil, phenylmethyl silicone oil, and reinforcing agent to a planetary mixer, and stir at low speed of 50-100 rpm for 5-10 minutes under vacuum conditions, and then stir at high speed of 300-500 rpm for 30-40 minutes to obtain the base material. Add flame retardant and modified ceramic powder, stir at low speed of 50-100 rpm for 10-20 minutes, then stir at high speed for 40-60 minutes; then add crosslinking agent, silane coupling agent and catalyst, stir at low speed of 30-50 rpm for 10-15 minutes, then degas under vacuum to obtain silicone sealant.

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