Mildew-proof flame-retardant silicone sealant for buildings and preparation method thereof

Abstract

The invention discloses a mildew-proof and flame-retardant silicone sealant for buildings and a preparation method of the mildew-proof and flame-retardant silicone sealant, and belongs to the technical field of high polymer materials. The sealant comprises dihydroxy polydimethylsiloxane, a composite mildew-proof agent, a composite flame retardant, a reinforcing filler and a cross-linking system, wherein the composite mildew preventive is silver-loaded nano silicon dioxide which is subjected to surface modification by a silane coupling agent and is loaded with BIT, and an organic / inorganic synergistic and slow-release mildew-proof network is constructed; the composite flame retardant is composed of surface modified aluminum hydroxide, silicon resin powder and a plant char-forming compound, the heat absorption, char-forming and ceramization multi-synergistic flame-retardant effect is achieved, all functional components are subjected to silanization treatment, and the compatibility with a silicone matrix is excellent. The silicone sealant prepared by the invention has 0-level long-acting mildew resistance, V-0-level efficient flame retardance, excellent mechanical property and storage stability, solves the problems that a mildew inhibitor is easy to migrate and a flame retardant is high in filling and poor in compatibility with a matrix, and is particularly suitable for building sealing scenes with double high requirements on sanitation and safety.

Description

A mildew-proof and flame-retardant silicone sealant for building and its preparation method Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a silicone sealant, and more particularly to a building silicone sealant with both long-lasting anti-mildew and high-efficiency flame-retardant properties, and its preparation method. Background Technology

[0002] Silicone sealants are widely used for sealing and bonding in building curtain walls, door and window joints, and kitchen and bathroom facilities due to their excellent weather resistance, high and low temperature resistance, and elasticity. However, ordinary silicone sealants are prone to mold growth in long-term humid and hot environments, affecting aesthetics and hygiene; at the same time, they lack flame retardancy, posing a fire hazard and making them unsuitable for places with strict safety and hygiene requirements such as hospitals, schools, and hotels. Currently, the mainstream method to give silicone sealants anti-mold or flame-retardant functions is to add appropriate functional additives to the formulation. However, the following technical bottlenecks exist: conventional anti-mold agents (such as isothiazolinones and organic guanidine salts) are mostly small-molecule polar organic compounds with poor compatibility with the weakly polar silicone matrix, easily migrating and precipitating, leading to a rapid decline in anti-mold effect and potential contamination of contact objects. To achieve effective flame retardancy (such as UL94 V-0 rating), large amounts of inorganic flame retardants (such as aluminum hydroxide and magnesium hydroxide) are often required. High filler content can severely degrade the mechanical properties of sealants, such as flexibility and elongation, and lead to poor thixotropy and extrusion difficulties. When mildew inhibitors and multiple flame retardants are added simultaneously, components with different polarities and forms are more difficult to disperse uniformly in the silicone matrix, and are prone to phase separation, agglomeration, and sedimentation, which seriously affects the product's storage stability, application performance, and final overall performance.

[0003] Therefore, developing a silicone sealant that can simultaneously achieve high efficiency, long-lasting mildew prevention and flame retardancy, with excellent compatibility of its components and good comprehensive mechanical properties has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a mildew-proof and flame-retardant silicone sealant for building applications and its preparation method. This sealant, through innovative component design and surface treatment processes, solves the core contradictions of easy migration of mildew inhibitors, high filler content of flame retardants, and poor compatibility with the matrix, achieving an excellent balance of mildew resistance, flame retardancy, mechanical properties, and processability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a mildew-proof and flame-retardant silicone sealant for building use, comprising the following components by weight: 100 parts of dihydroxy polydimethylsiloxane; 30-35 parts of composite flame retardant; 2-3 parts of composite mildew inhibitor; 10-15 parts of plasticizer; 20-25 parts of nanoporous carrier; 5-8 parts of crosslinking agent; 1-2 parts of coupling agent; and 0.1-0.3 parts of catalyst; wherein the composite flame retardant comprises: 15-20 parts of surface-modified aluminum hydroxide; 5-8 parts of silicone resin powder; and 2-5 parts of plant-based charcoal composite.

[0006] Further, preferably: the composite antifungal agent comprises 8-10 parts of silver-loaded nano-SiO2 with an Ag loading of 2-2.5%, 3-5 parts of BIT, and 0.2-0.3 parts of KH-570, and its preparation method is as follows: the silver-loaded nano-SiO2 is treated with ethanol containing KH-570, dried, and then ball-milled with BIT powder and anhydrous ethanol for 2 hours, dried and pulverized to obtain the final product.

[0007] Further, preferably: the preparation method of the surface-modified aluminum hydroxide is as follows: ultrafine aluminum hydroxide is preheated to 110°C, and then 50% by mass of KH-570 ethanol solution is sprayed into it. The mixture is stirred and reacted for 30 minutes to obtain surface-modified aluminum hydroxide.

[0008] Further, preferably: the preparation method of the plant char complex is as follows: tannic acid and pregelatinized starch are dissolved in water, impregnated in fumed silica, dried, and then sprayed with a 5% KH-570 ethanol solution to obtain the plant char complex.

[0009] Further, preferably, the plasticizer is dimethyl silicone oil.

[0010] Furthermore, preferably, the nanoporous support is fumed silica or nano-calcium carbonate.

[0011] Further, preferably, the crosslinking agent is methyltributanone oxime silane.

[0012] Further, preferably, the coupling agent is γ-aminopropyltriethoxysilane.

[0013] Further, preferably, the catalyst is dibutyltin dilaurate.

[0014] The present invention also provides a method for preparing a mildew-proof and flame-retardant silicone sealant for building, comprising the following steps: (1) Base material mixing and dehydration: Dihydroxy polydimethylsiloxane, plasticizer, nanoporous carrier, surface-modified aluminum hydroxide, plant char complex and composite mildew inhibitor are added to a stirring device and dehydrated and mixed for 1.5 to 2 hours under vacuum conditions at 120~130℃; (2) Cooling and final mixing: The base material obtained in step (1) is cooled to below 50℃, silicone resin powder, crosslinking agent and coupling agent are added, and vacuum is mixed evenly; (3) The material is cooled to room temperature, and stirring and vacuum are maintained. Then dibutyltin dilaurate is added, and the vacuum degree is increased to above -0.098MPa. Stirring and degassing are carried out, and the time is controlled within 3-5 minutes. When no obvious bubbles are observed in the adhesive, stirring is stopped, and the material is discharged and filled.

[0015] The beneficial effects of this invention are:

[0016] This invention combines the organic antifungal agent BIT with the inorganic antibacterial component silver-loaded nano-SiO2, and uses a silane coupling agent to anchor them together on a nano-carrier. This achieves synergistic enhancement and physical fixation of the antifungal agents, effectively preventing migration and precipitation, and ensuring long-lasting and stable antifungal performance, with the expectation of reaching the 0-level antifungal standard.

[0017] This invention employs a surface-modified aluminum hydroxide / silicone resin / plant char composite ternary flame retardant system, which leverages multiple synergistic flame retardant effects of endothermic cooling, gas phase dilution, catalytic char formation, and ceramic barrier. During combustion, it forms a dense and robust ceramic-carbon-silicon composite protective layer, enabling the product to easily meet the UL94 V-0 flame retardant standard with low smoke production.

[0018] This invention employs a silane coupling agent (such as KH-570) to surface-treat all functional inorganic and organic-inorganic hybrid particles (aluminum hydroxide, plant-based charcoal composite carrier, silver-loaded nano-SiO2), ensuring their surface properties are highly compatible with the silicone matrix. This fundamentally solves the compatibility problem of multi-component, multi-phase systems. This allows each component to be uniformly and stably dispersed in the matrix, achieving a high flame retardant rating while avoiding the damage to mechanical properties caused by high filler content. The sealant still maintains good tensile strength, high elongation, and flexibility.

[0019] The flame-retardant system of the silicone sealant of this invention is based on halogen-free modified aluminum hydroxide and incorporates natural plant-based ingredients, making it more environmentally friendly. It requires less mildew inhibitor and is highly efficient, with controllable overall formulation costs and excellent cost performance. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative effort are also described.

[0021] Pretreatment of raw materials used in this invention:

[0022] Preparation process of compound antifungal agent:

[0023] (1) Mix 25 parts anhydrous ethanol, 0.5 parts deionized water and 1 drop of glacial acetic acid, stir well, and then slowly add 0.25 parts KH-570 to the above solution. After the addition is complete, continue stirring for 30 minutes to obtain a clear KH-570 hydrolysis prepolymer solution; (2) Disperse 10 parts of dry silver-loaded nano-SiO2 (silver loading content 2%, Zhejiang Zhitai Nano Micro New Materials Co., Ltd.) and 45 parts anhydrous ethanol ultrasonically for 15 minutes to form a uniform suspension. Slowly add the prepared KH-570 hydrolysis prepolymer solution to the suspension through a constant pressure dropping funnel within 30 minutes. After the addition is complete, reflux and condense at 60°C, and continue stirring (300 rpm) for 6 hours. After the reaction is completed, cool the mixture to room temperature, transfer it to a centrifuge tube, and centrifuge at 8000 rpm. Centrifuge at rpm for 10 minutes, collect the solid, ultrasonically wash with anhydrous ethanol and centrifuge, repeat this process 3 times to completely remove the physically adsorbed silane, and dry in a vacuum drying oven at 60℃ for 12 hours; gently grind the dried block and pass it through a 200-mesh sieve to obtain KH-570 modified silver-loaded nano-SiO2, and seal it for later use; (3) accurately weigh all the above KH-570 modified silver-loaded nano-SiO2 and 4.0 parts of ultrafine BIT powder, place them in a zirconia ball mill jar, add 20 parts of anhydrous ethanol as a process control agent, add zirconia grinding balls, the ball-to-material mass ratio is 10:1, and the size ball ratio (Φ5mm:Φ10mm=1:2) is used to optimize the grinding efficiency. Set the parameters: revolution speed 300 rpm, rotation speed 600 rpm. rpm, using an intermittent mode of running for 30 minutes and pausing for 5 minutes, the total effective ball milling time is 2 hours; (4) After ball milling, transfer the slurry to a glass petri dish and pre-dry it in a 50℃ forced-air drying oven for 4 hours. Transfer the pre-dried material to a 40℃ vacuum drying oven and continue drying for 8 hours to ensure complete solvent removal. Grind the dried loose blocks and pass them through a 400-mesh sieve to obtain a composite anti-mildew agent.

[0024] Surface-modified aluminum hydroxide:

[0025] 1000 parts of ultrafine ATH powder (D50=1.5±0.2 μm, moisture content ≤0.5%) were added to a high-speed heating mixer. The mixer was started, and the stirring speed was set to 300 rpm. Heating was initiated. The material temperature was raised to 110±2°C at a uniform rate, and stirring was performed for 20-30 minutes. The sight glass of the mixer was observed to ensure that no steam or water mist was generated. 15 parts of KH-570 were added to 15 parts of anhydrous ethanol, and the mixture was stirred with a glass rod until completely homogeneous, forming a 50% concentration KH-570 ethanol solution. The KH-570 ethanol solution was sprayed evenly and slowly onto the continuously churning ATH powder. After spraying, the temperature was maintained at 110°C, and the stirring speed was increased to 500 rpm. The reaction was continued for 30 minutes. After the reaction was completed, heating was stopped, and the material was cooled to below 40°C under continuous stirring before being discharged. The obtained surface-modified aluminum hydroxide product was a loose, free-flowing white powder.

[0026] Preparation method of plant char-forming complex: Add 50 parts tannic acid and 100 parts pregelatinized starch sequentially to 500 parts deionized water at 150 rpm, heat to 60°C, and stir continuously for about 30 minutes until a homogeneous, slightly viscous, light yellow transparent solution is obtained; slowly and in portions, add all the prepared char precursor solution to 200 parts fumed silica. After the addition is complete, continue stirring for 10 minutes to obtain a moist but loose homogeneous mixture without visible large droplets. Place the moist mixture at 80°C and dry for 6 hours until the material is completely dry and can be easily crumbled by hand; dissolve 5 parts KH-570 in 100 parts anhydrous ethanol and stir evenly for later use.

[0027] The initially dried lumpy material is ground and passed through a 200-mesh sieve to obtain a fine loaded powder. A prepared KH-570 ethanol solution is sprayed onto the loaded powder. After spraying, the material is allowed to stand in a ventilated area at room temperature for 30 minutes, then placed back into an 80°C forced-air drying oven for 3 hours to completely remove the ethanol and promote complete curing of KH-570. After drying, it is removed, cooled to room temperature, ground, and passed through a 200-mesh sieve to obtain the final product—a plant-based charcoal composite. This product is a grayish-white to light grayish-brown, highly free-flowing ultrafine powder.

[0028] The viscosity of dihydroxy polydimethylsiloxane is 50,000 mPa·s, the viscosity of dimethyl silicone oil is 350 mPa·s, the particle size of nano-calcium carbonate is 40-80 nm, and the silicone resin powder is methyl silicone resin with a D50 of 8 μm. Other raw materials have no special requirements and only need to meet relevant raw material standards. Example 1

[0029] The composition includes: 100 parts of dihydroxypolydimethylsiloxane; 33 parts of composite flame retardant; 2 parts of composite mildew inhibitor; 12 parts of plasticizer; 22 parts of nanoporous carrier; 6 parts of crosslinking agent; 1 part of coupling agent; and 0.2 parts of catalyst. The composite flame retardant comprises: 15 parts of surface-modified aluminum hydroxide; 6 parts of silicone resin powder; and 3 parts of plant-based charcoal composite. The plasticizer is dimethyl silicone oil; the nanoporous carrier is nano-calcium carbonate; the crosslinking agent is methyl tributanone oxime silane; the coupling agent is γ-aminopropyltriethoxysilane; and the catalyst is dibutyltin dilaurate.

[0030] The preparation method includes the following steps: (1) Base material mixing and dehydration: Dihydroxy polydimethylsiloxane, plasticizer, nano calcium carbonate, surface-modified aluminum hydroxide, plant char-forming complex and composite antifungal agent are added to the stirring equipment and dehydrated and mixed for 1.5 hours under vacuum at 130°C; (2) Cooling and final mixing: The base material obtained in step S2 is cooled to below 50°C, silicone resin powder, crosslinking agent and coupling agent are added, and vacuum is mixed evenly; (3) The material is cooled to room temperature (25-30°C), and stirring and vacuum are maintained. Then dibutyltin dilaurate is added, and the vacuum degree is increased to above -0.098MPa. Stirring and degassing are carried out, and the time is controlled within 3-5 minutes. When no obvious bubbles are observed in the adhesive, stirring is stopped, and the material is discharged and filled. Example 2

[0031] A mildew-proof and flame-retardant silicone sealant for building use, comprising the following components by weight: 100 parts dihydroxy polydimethylsiloxane; 30 parts composite flame retardant; 2.5 parts composite mildew inhibitor; 13 parts plasticizer; 20 parts nanoporous carrier; 5 parts crosslinking agent; 1.5 parts coupling agent; and 0.1 parts catalyst. The composite flame retardant comprises: 18 parts surface-modified aluminum hydroxide; 7 parts silicone resin powder; and 4 parts plant-based charcoal composite. The plasticizer is dimethyl silicone oil; the nanoporous carrier is nano-calcium carbonate; the crosslinking agent is methyl tributanone oxime silane; the coupling agent is γ-aminopropyltriethoxysilane; and the catalyst is dibutyltin dilaurate.

[0032] The preparation method includes the following steps: (1) Base material mixing and dehydration: Dihydroxy polydimethylsiloxane, plasticizer, nano calcium carbonate, surface modified aluminum hydroxide, plant char complex and composite antifungal agent are added to the stirring equipment, the speed is 500 rpm, and the mixture is dehydrated and mixed for 2 hours under vacuum at 120°C; (2) Cooling and final mixing: The base material obtained in step S2 is cooled to below 50°C, silicone resin powder, crosslinking agent and coupling agent are added, and the mixture is vacuum mixed evenly; (3) The material is cooled to room temperature (25-30°C), and stirring and vacuum are maintained. Then dibutyltin dilaurate is added, the vacuum degree is increased to above -0.098MPa, and stirring and degassing are carried out. The time is controlled within 3-5 minutes. When no obvious bubbles are observed in the adhesive, stirring is stopped, and the material is discharged and filled. Example 3

[0033] A mildew-proof and flame-retardant silicone sealant for building use, comprising the following components by weight: 100 parts dihydroxy polydimethylsiloxane; 35 parts composite flame retardant; 3 parts composite mildew inhibitor; 15 parts plasticizer; 25 parts nanoporous carrier; 7 parts crosslinking agent; 1.2 parts coupling agent; and 0.3 parts catalyst. The composite flame retardant comprises: 20 parts surface-modified aluminum hydroxide; 5 parts silicone resin powder; and 2 parts plant-based charcoal composite. The plasticizer is dimethyl silicone oil; the nanoporous carrier is nano-calcium carbonate; the crosslinking agent is methyl tributanone oxime silane; the coupling agent is γ-aminopropyltriethoxysilane; and the catalyst is dibutyltin dilaurate.

[0034] The preparation method includes the following steps: (1) Base material mixing and dehydration: Dihydroxy polydimethylsiloxane, plasticizer, nano calcium carbonate, surface modified aluminum hydroxide, plant char complex and composite antifungal agent are added to the stirring equipment, the speed is 500 rpm, and dehydration and mixing are carried out at 125℃ and vacuum for 2 hours; (2) Cooling and final mixing: The base material obtained in step S2 is cooled to below 50℃, silicone resin powder, crosslinking agent and coupling agent are added, and vacuum mixing is carried out evenly; (3) The material is cooled to room temperature (25-30℃), and stirring and vacuum are maintained. Then dibutyltin dilaurate is added, the vacuum degree is increased to above -0.098MPa, and stirring and degassing are carried out. The time is controlled within 3-5 minutes. When no obvious bubbles are observed in the adhesive, stirring is stopped, and the material is discharged and filled. Example 4

[0035] A mildew-proof and flame-retardant silicone sealant for building use, by weight, comprises the following components: 100 parts dihydroxy polydimethylsiloxane; 32 parts composite flame retardant; 2 parts composite mildew inhibitor; 10 parts plasticizer; 23 parts nanoporous carrier; 8 parts crosslinking agent; 2 parts coupling agent; and 0.2 parts catalyst. The composite flame retardant comprises: 17 parts surface-modified aluminum hydroxide; 8 parts silicone resin powder; and 5 parts plant-based charcoal composite. The plasticizer is dimethyl silicone oil; the nanoporous carrier is nano-calcium carbonate; the crosslinking agent is methyl tributanone oxime silane; the coupling agent is γ-aminopropyltriethoxysilane; and the catalyst is dibutyltin dilaurate.

[0036] The preparation method includes the following steps: (1) Base material mixing and dehydration: Dihydroxy polydimethylsiloxane, plasticizer, nano calcium carbonate, surface modified aluminum hydroxide, plant char complex and composite antifungal agent are added to the stirring equipment, the speed is 500 rpm, and the mixture is dehydrated and mixed for 2 hours under vacuum at 120℃; (2) Cooling and final mixing: The base material obtained in step S2 is cooled to below 50℃, silicone resin powder, crosslinking agent and coupling agent are added, and the mixture is vacuum mixed evenly; (3) The material is cooled to room temperature (25-30℃), and stirring and vacuum are maintained. Then dibutyltin dilaurate is added, the vacuum degree is increased to above -0.098MPa, and stirring and degassing are carried out. The time is controlled within 3-5 minutes. When no obvious bubbles are observed in the adhesive, stirring is stopped, and the material is discharged and filled.

[0037] Comparative Example 1

[0038] The process is basically the same as in Example 1, except that the composite antifungal agent is replaced by directly adding silver-loaded nano-SiO2 and 4.0 parts of ultrafine BIT powder, without pre-composite and loading. The other components and processes are the same as in Example 1.

[0039] Comparative Example 2

[0040] The process is basically the same as in Example 1, except that the composite flame retardant is replaced by directly adding ultrafine aluminum hydroxide, and silicone resin powder and plant-based charcoal composite are not added. The remaining components and processes are the same as in Example 1.

[0041] Comparative Example 3

[0042] The difference from Example 1 is that all surface modification steps are omitted: untreated raw materials are used for both aluminum hydroxide and silver-loaded nano-SiO2, and no composite is prepared; the surface-modified aluminum hydroxide is replaced with 18 parts of ordinary ATH; the plant-based char composite is replaced with fumed silica; and the composite antifungal agent is replaced with BIT powder + ordinary silver-loaded nano-SiO2 powder. The remaining components and processes are the same as in Example 1.

[0043] Comparative Example 4

[0044] This comparative example is a basic silicone sealant without any added flame retardants or mildew inhibitors. The formulation is: 100 parts 107 adhesive, 10 parts silicone oil, 15 parts nano-calcium carbonate, 6 parts crosslinking agent, 1.5 parts coupling agent, and 0.2 parts catalyst. The preparation process is the same as S2 and S3 of Example 1 (no need for prolonged dehydration).

[0045] Performance Testing and Result Analysis

[0046] The sealants prepared in Examples 1-4 and Comparative Examples 1-4 were cured under standard conditions (23±2℃, 50±5% humidity) for 7 days, and then their performance was tested according to the corresponding national standards. The results are shown in Table 1 below.

[0047]

[0048] As shown in Table 1, the silicone sealant of the present invention has excellent performance: the highest anti-mildew rating (0 grade), the highest flame retardant rating (V-0), and a fire resistance integrity of more than 7 hours. At the same time, it maintains good mechanical properties (tensile strength of more than 2.60 MPa and adhesive strength of about 2.10 MPa) and is stable in storage.

[0049] In Comparative Example 1, the antifungal agent was untreated, and its antifungal performance was initially acceptable but not durable (it deteriorated later), and there was a slight risk of BIT precipitation. Comparative Example 2 (using only a large amount of untreated ATH flame retardant) showed that the flame retardant effect was substandard (only V-1), and the mechanical properties were severely impaired. Comparative Example 3 (all components untreated) had the worst overall performance: both flame retardancy (V-2) and antifungal performance (level 2) were significantly reduced, compatibility was extremely poor (settling and agglomeration), and the mechanical strength was also the lowest.

[0050] This invention's composite antifungal agent achieves a synergistic breakthrough in antifungal efficacy and system compatibility through innovative structural design. Structurally, porous nano-SiO2 serves as a carrier, and BIT antifungal agent is loaded onto its surface and pores using a ball milling process. Surface grafting modification is then performed using KH-570 silane coupling agent to construct composite particles of BIT / silver-loaded nano-SiO2 / KH-570. Functionally, the silver-loaded nano-SiO2 releases Ag... + BIT and antifungal agents exert a synergistic antibacterial effect through two different mechanisms: disrupting cell membrane / enzyme systems and interfering with respiratory metabolism. This broadens the antibacterial spectrum and delays drug resistance. Simultaneously, BIT's gas-phase protection works in conjunction with Ag... + The contact-based killing mechanism forms a dual defense of atmosphere and contact, giving the product rapid and long-lasting anti-mold capabilities. In terms of compatibility, the organosilane layer of KH-570 fundamentally alters the surface properties of the particles, making them highly compatible with the polarity of the silicone matrix. This stabilizes the anti-mold active components within the system, completely solving the industry problem of difficult dispersion and easy migration of anti-mold agents in hydrophobic silicone systems.

[0051] The composite flame retardant system of this invention achieves a dual improvement in flame retardant efficiency and system compatibility through the synergistic effect of multiple components.

[0052] In terms of flame retardant performance: the surface-modified aluminum hydroxide first absorbs heat and decomposes, cooling the system and diluting the combustible gas, creating conditions for subsequent reactions; the plant-based charcoal complex then catalyzes the formation of an expanded charcoal layer, effectively insulating the heat; the silicone resin powder is transformed into a robust ceramic layer at high temperature, which encapsulates and reinforces the aforementioned charcoal layer and Al2O3 residue, ultimately forming a stable Al2O3 / charcoal / ceramic composite barrier that efficiently isolates heat and oxygen.

[0053] In terms of compatibility: both aluminum hydroxide and the plant-based composite carrier are surface-treated with silane coupling agents, which change them from hydrophilic to hydrophobic, and their polarity is highly matched with that of the silicone matrix; the silicone resin achieves perfect compatibility with its intrinsic chemical structure, ensuring that all fillers are uniformly and stably dispersed in the matrix, thereby achieving high flame retardancy (V-0 rating) while maximizing the mechanical properties, processability and storage stability of the sealant.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A mildew-proof and flame-retardant silicone sealant for building applications, characterized in that, By weight, it includes the following components: 100 parts of dihydroxy polydimethylsiloxane; 30-35 parts of composite flame retardant; 2-3 parts of composite mildew inhibitor; 10-15 parts of plasticizer; 20-25 parts of nanoporous carrier; 5-8 parts of crosslinking agent; and 1-2 parts of coupling agent. Catalyst 0.1~0.3 parts; the composite flame retardant includes: surface-modified aluminum hydroxide: 15~20 parts, silicone resin powder: 5~8 parts; Plant-based charcoal complex: 2-5 parts.

2. The mildew-proof and flame-retardant silicone sealant for building construction according to claim 1, characterized in that: The composite antifungal agent comprises 8-10 parts of silver-loaded nano-SiO2 with an Ag loading of 2-2.5%, 3-5 parts of BIT, and 0.2-0.3 parts of KH-570. The preparation method is as follows: the silver-loaded nano-SiO2 is treated with ethanol containing KH-570, dried, and then ball-milled with BIT powder and anhydrous ethanol for 2 hours, dried and pulverized to obtain the final product.

3. The mildew-proof and flame-retardant silicone sealant for building construction according to claim 1 or 2, characterized in that: The preparation method of the surface-modified aluminum hydroxide is as follows: ultrafine aluminum hydroxide is preheated to 110°C, and then 50% by mass of KH-570 ethanol solution is sprayed into it. The mixture is stirred and reacted for 30 minutes to obtain surface-modified aluminum hydroxide.

4. The mildew-proof and flame-retardant silicone sealant for building construction according to claim 1 or 2, characterized in that: The preparation method of the plant char complex is as follows: tannic acid and pregelatinized starch are dissolved in water, impregnated in fumed silica, dried, and then sprayed with a 5% KH-570 ethanol solution to obtain the plant char complex.

5. The mildew-proof and flame-retardant silicone sealant for building construction according to claim 4, characterized in that: The plasticizer is dimethyl silicone oil.

6. The mildew-proof and flame-retardant silicone sealant for building construction according to claim 4, characterized in that: The nanoporous support is fumed silica or nano-calcium carbonate.

7. The mildew-proof and flame-retardant silicone sealant for building construction according to claim 4, characterized in that: The crosslinking agent is methyltributanone oxime silane.

8. The mildew-proof and flame-retardant silicone sealant for building construction according to claim 4, characterized in that: The coupling agent is γ-aminopropyltriethoxysilane.

9. The mildew-proof and flame-retardant silicone sealant for building construction according to claim 4, characterized in that: The catalyst is dibutyltin dilaurate.

10. A method for preparing a mildew-proof and flame-retardant silicone sealant for building use as described in any one of claims 1-9, comprising the following steps: (1) Base material mixing and dehydration: Dihydroxy polydimethylsiloxane, plasticizer, nanoporous carrier, surface modified aluminum hydroxide, plant char complex and composite antifungal agent are added to the stirring equipment and dehydrated and mixed for 1.5 to 2 hours under vacuum at 120~130℃; (2) Cooling and final mixing: Cool the base material obtained in step (1) to below 50℃, add silicone resin powder, crosslinking agent and coupling agent, and mix evenly under vacuum; (3) Cool the material to room temperature, and keep stirring and vacuum, then add dibutyltin dilaurate, increase the vacuum degree to above -0.098MPa, stir and degas, control the time within 3-5 minutes, observe that there are no obvious bubbles in the rubber material, stop stirring, and discharge and fill.

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