High-strength silicone sealant and preparation method thereof

Abstract

The invention relates to the technical field of sealants, in particular to a high-strength silicone sealant and a preparation method thereof. The preparation method comprises the following steps: adding alpha, omega-dihydroxy polydimethylsiloxane into a kneading machine, adding modified wollastonite, zinc borate, a flame-retardant cross-linking agent and simethicone, uniformly mixing, heating to 120-130 DEG C, carrying out vacuum kneading for 1-3 hours, and cooling to room temperature to obtain a base material; mixing the base material and the ketoxime crosslinking agent, stirring for 10-20 minutes, adding fumed silica, a coupling agent and a catalyst, stirring for 60-120 minutes in vacuum, and sealing and packaging to obtain the high-strength silicone sealant. The high-strength silicone sealant prepared by the invention has excellent mechanical property and flame retardant property, so that the service life of the high-strength silicone sealant is prolonged.

Description

Technical Field

[0001] This invention relates to the field of sealant technology, specifically to a high-strength silicone sealant and its preparation method. Background Technology

[0002] Silicone sealants possess excellent weather resistance, water resistance, and temperature resistance, making them widely used in construction, automotive, and electronics industries. However, traditional silicone sealants have shortcomings in terms of strength and curing speed, making it difficult to meet the demands of modern industry for high-performance sealing materials. For example, in building curtain wall construction, sealants need to cure quickly and reach high strength to ensure the safety and stability of the structure; in electronic equipment manufacturing, sealants need to possess high strength to withstand vibration and impact. Furthermore, traditional silicone sealants are flammable, especially during automotive operation and use. If exposed to fire, their insufficient flame-retardant properties could lead to serious safety hazards.

[0003] Therefore, developing a high-strength and fast-curing silicone sealant has significant application value. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength silicone sealant and its preparation method to solve the problems raised in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a high-strength silicone sealant includes the following steps: Add α,ω-dihydroxypolydimethylsiloxane to a kneader, then add modified wollastonite, zinc borate, flame retardant crosslinking agent, and dimethyl silicone oil and mix thoroughly. Heat to 120-130℃ and knead under vacuum for 1-3 hours. After cooling to room temperature, obtain the base material. Mix the base material with a ketoxime crosslinking agent and stir for 10-20 minutes. Add fumed silica, coupling agent, and catalyst, and stir under vacuum for 60-120 minutes. Seal and package to obtain a high-strength silicone sealant.

[0006] Furthermore, the high-strength silicone sealant is composed of the following components in parts by weight: 100-120 parts of α,ω-dihydroxypolydimethylsiloxane, 30-50 parts of modified wollastonite, 10-20 parts of zinc borate, 5-10 parts of flame retardant crosslinking agent, 15-30 parts of dimethyl silicone oil, 50-70 parts of fumed silica, 10-15 parts of ketoxime crosslinking agent, 2-5 parts of catalyst, and 1-3 parts of coupling agent.

[0007] Furthermore, the modified wollastonite is prepared as follows: Step A: Disperse wollastonite ultrasonically in a mixed solution of anhydrous ethanol and deionized water, adjust the pH to 10-11 by adding ammonia dropwise, add tetraethyl orthosilicate and 3-aminopropyltrimethoxysilane, react at 60-70℃ for 12-24 h, and obtain aminated wollastonite after filtration, washing and drying. Step B: Under nitrogen protection, 1,1,1,3,5,5,5-heptamethyltrisiloxane and terminal epoxy allyl polyether are mixed evenly, chloroplatinic acid-isopropanol solution is added, and the mixture is reacted at 75-85℃ for 4-6 hours. The mixture is then distilled under reduced pressure to obtain terminal epoxy polyether modified trisiloxane. Step C: Mix aminated wollastonite, terminal epoxy polyether modified trisiloxane and tetrahydrofuran evenly, react at 40-50℃ for 10-12h, filter, wash and dry to obtain modified wollastonite.

[0008] Further, in step A, the mass ratio of wollastonite, anhydrous ethanol and deionized water is 1:(10-12):(3-5).

[0009] Furthermore, in step A, the concentration of ammonia is 1 mol / L.

[0010] Further, in step A, the mass ratio of wollastonite, tetraethyl orthosilicate, and 3-aminopropyltrimethoxysilane is 1:(1.5-2.5):(0.3-0.8).

[0011] Further, in step B, the molar ratio of 1,1,1,3,5,5,5-heptamethyltrisiloxane and terminal epoxy-terminated allyl polyether is 1:(1.0-1.2).

[0012] Further, in step B, the amount of chloroplatinic acid-isopropanol solution used, measured in Pt, is 2-4 ppm of the total mass of terminal epoxy allyl polyether and boron- and hydrogen-containing silicone oil.

[0013] Further, in step C, the mass ratio of aminated wollastonite, terminal epoxy polyether modified trisiloxane, and tetrahydrofuran is 1:(0.3-0.6):(4-6).

[0014] Furthermore, the preparation method of the flame-retardant crosslinking agent is as follows: Step 1: Esterify pentaerythritol and phosphoric acid to obtain pentaerythritol phosphate liquid; mix melamine and deionized water evenly, heat to 60-80℃, add pentaerythritol phosphate liquid, react at 80-100℃ for 4-6 hours, centrifuge to dehydrate and dry to obtain pentaerythritol phosphate melamine salt. Step 2: Mix the terminal epoxy polyether modified trisiloxane, pentaerythritol phosphate melamine salt and N,N-dimethylformamide evenly, react at 40-50℃ for 6-8 hours, and after filtration, washing and drying, obtain the flame retardant crosslinking agent.

[0015] Furthermore, in step 1, the molar ratio of pentaerythritol to phosphoric acid is 1:2, and the esterification reaction conditions are: reaction temperature 100-120℃ and reaction time 3-6h.

[0016] Further, in step 1, the mass ratio of melamine, deionized water and pentaerythritol phosphate liquid is 1:(10-12):(1.1-1.3).

[0017] Furthermore, in step 2, the mass ratio of the terminal epoxy polyether modified trisiloxane, pentaerythritol phosphate melamine salt and N,N-dimethylformamide is 1:(1-3):(4-6).

[0018] Furthermore, the viscosity of the α,ω-dihydroxypolydimethylsiloxane at 25°C is 5000-200000 mPa·s.

[0019] Furthermore, the viscosity of the dimethyl silicone oil at 25°C is 200-500 mPa·s.

[0020] Furthermore, the catalyst is one or two of dibutyltin diacetate, dibutyltin dilaurate, dibutyltin diacetylacetone, and dibutyltin diacetate.

[0021] Furthermore, the ketoxime crosslinking agent is two or more of the following: methyl tributanone oxime silane, vinyl tributanone oxime silane, phenyl tributanone oxime silane, and tetrabutanone oxime silane.

[0022] Furthermore, the vacuum degree of the vacuum stirring is -0.08 to -0.10 MPa.

[0023] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention discloses a high-strength silicone sealant and its preparation method. Using tetraethyl orthosilicate (TEOS) and 3-aminopropyltriethoxysilane (KH550) as raw materials, a sol-gel process is employed to coat and modify wollastonite, resulting in SiO2-coated aminated wollastonite. The abundant siloxane structure significantly enhances its dispersion performance in the sealant. Using 1,1,1,3,5,5,5-heptamethyltrisiloxane (HTSO) and terminal epoxy-based allyl polyether as raw materials, a hydrosilylation reaction is conducted to obtain terminal epoxy-based polyether-modified trisiloxane. The reaction between the aminated wollastonite and the terminal epoxy-based polyether-modified trisiloxane forms a strong and tough cross-linked network, enhancing the overall mechanical strength of the sealant while retaining the imino groups of the aminosilane coupling agent, thus also possessing the function of a silane coupling agent.

[0024] 2. This invention discloses a high-strength silicone sealant and its preparation method. Pentaerythritol phosphate melamine salt is synthesized from pentaerythritol, phosphoric acid, and melamine. Then, a flame-retardant structure is successfully introduced into the crosslinking agent by reacting a terminal epoxy polyether-modified trisiloxane with the pentaerythritol phosphate melamine salt, thus obtaining a flame-retardant crosslinking agent. This agent can synergistically improve the flame-retardant properties of the material with zinc borate. Furthermore, this crosslinking agent has multiple hydrolyzable groups. The hydrolyzed silanol groups can react with α,ω-dihydroxy polydimethylsiloxane, thereby significantly improving the cohesive strength of the silicone sealant. Simultaneously, it contains flexible polyether segments, enabling the prepared silicone sealant to maintain high strength while retaining good elasticity and flexibility, thus extending its service life. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise specified, all quantities below are by weight. It should be noted that there are no special restrictions on the suppliers of any of the raw materials involved in this invention. Exemplary examples (in this embodiment) include: α,ω-dihydroxypolydimethylsiloxane: 107 silica gel viscosity, 50000 mPa·s, purchased from Hubei Xingchuang New Materials Co., Ltd.; dimethyl silicone oil: grade 201, viscosity 350 mPa·s, industrial grade, purchased from Guangdong Yuexingfa Import & Export Co., Ltd.; wollastonite: particle size 10-20 μm; zinc borate: model ZR-001, purchased from Zhengzhou Juepai Chemical Products Co., Ltd.; fumed silica: model H... P-150 was purchased from Foshan Yujia New Materials Co., Ltd.; coupling agent: model FD-1146, purchased from Anhui Boiling Point New Materials Co., Ltd.; the ketoxime crosslinking agent used in the embodiments of this invention is a compound of methyl tributanone oxime silane and vinyl tributanone oxime silane in a mass ratio of 1:1, both of which were purchased from Hubei Xinlantian New Materials Co., Ltd.; catalyst: organotin catalyst HT2401A, purchased from Nantong Haotai Chemical Products Co., Ltd.; terminal epoxy allyl polyether: model KL-11, purchased from Liaoning Kelong Fine Chemical Co., Ltd.

[0027] Example 1: A method for preparing a high-strength silicone sealant, comprising the following processes: 100 parts of α,ω-dihydroxypolydimethylsiloxane were added to a kneader, along with 30 parts of modified wollastonite, 10 parts of zinc borate, 5 parts of flame retardant crosslinking agent, and 15 parts of dimethyl silicone oil. The mixture was stirred until homogeneous, heated to 120°C, and vacuum kneaded for 1 hour. After cooling to room temperature, the base material was obtained. The base material and 10 parts of ketoxime crosslinking agent were added to a planetary mixer and stirred for 10 minutes. Then, 50 parts of fumed silica, 1 part of coupling agent, and 2 parts of catalyst were added. The mixture was stirred for 60 minutes under a vacuum of -0.08 MPa and sealed in a package to obtain a high-strength silicone sealant. The preparation method of modified wollastonite is as follows: Step A: Disperse 30 parts of wollastonite ultrasonically in a mixed solution of 300 parts of anhydrous ethanol and 90 parts of deionized water, adjust the pH to 10 by adding 1 mol / L ammonia, add 45 parts of tetraethyl orthosilicate and 9 parts of 3-aminopropyltrimethoxysilane, react at 60°C for 12 h, filter, wash and dry to obtain aminated wollastonite; Step B: Under nitrogen protection, 1,1,1,3,5,5,5-heptamethyltrisiloxane and terminal epoxy-based allyl polyether were mixed evenly in a molar ratio of 1:1, and a chloroplatinic acid-isopropanol solution was added. The mixture was reacted at 75°C for 4 hours and then distilled under reduced pressure to obtain terminal epoxy-based polyether modified trisiloxane. The amount of chloroplatinic acid-isopropanol solution used was 2 ppm of the total mass of the terminal epoxy-based allyl polyether and the boron- and hydrogen-containing silicone oil, measured by Pt. Step C: Mix 30 parts of aminated wollastonite, 9 parts of terminal epoxy polyether modified trisiloxane and 120 parts of tetrahydrofuran evenly, and react at 40°C for 10 hours to obtain modified wollastonite. The preparation method of the flame retardant crosslinking agent is as follows: Step 1: Esterification reaction of pentaerythritol and phosphoric acid at a molar ratio of 1:2 (reaction temperature 100℃, reaction time 3h) to obtain pentaerythritol phosphate liquid; Mix 5 parts of melamine and 50 parts of deionized water evenly, heat to 60℃, add 5.5 parts of pentaerythritol phosphate liquid, react at 80℃ for 4h, and after centrifugation, dehydration and drying, obtain pentaerythritol phosphate melamine salt; Step 2: Mix 5 parts of terminal epoxy polyether modified trisiloxane, 5 parts of pentaerythritol phosphate melamine salt and 20 parts of N,N-dimethylformamide evenly, react at 40°C for 6 hours, and after filtration, washing and drying, obtain flame retardant crosslinking agent.

[0028] Example 2: A method for preparing a high-strength silicone sealant, comprising the following processes: 110 parts of α,ω-dihydroxypolydimethylsiloxane were added to a kneader, along with 40 parts of modified wollastonite, 15 parts of zinc borate, 8 parts of flame retardant crosslinking agent, and 25 parts of dimethyl silicone oil. The mixture was stirred until homogeneous, heated to 125°C, and vacuum kneaded for 2 hours. After cooling to room temperature, the base material was obtained. The base material and 12 parts of ketoxime crosslinking agent were added to a planetary mixer and stirred for 15 minutes. 60 parts of fumed silica, 2 parts of coupling agent, and 3 parts of catalyst were added and stirred for 100 minutes under a vacuum of -0.09 MPa. The mixture was then sealed and packaged to obtain a high-strength silicone sealant. The preparation method of modified wollastonite is as follows: Step A: 40 parts of wollastonite were ultrasonically dispersed in a mixed solution of 440 parts of anhydrous ethanol and 160 parts of deionized water. Ammonia was added dropwise to adjust the pH to 10.5. 80 parts of tetraethyl orthosilicate and 20 parts of 3-aminopropyltrimethoxysilane and anhydrous ethanol were added. The mixture was reacted at 65°C for 20 hours. After filtration, washing and drying, aminated wollastonite was obtained. Step B: Under nitrogen protection, 1,1,1,3,5,5,5-heptamethyltrisiloxane and terminal epoxy-based allyl polyether were mixed evenly at a molar ratio of 1:1.1, and a chloroplatinic acid-isopropanol solution was added. The mixture was reacted at 80°C for 5 hours and then distilled under reduced pressure to obtain terminal epoxy-based polyether modified trisiloxane. The amount of chloroplatinic acid-isopropanol solution used was 3 ppm of the total mass of the terminal epoxy-based allyl polyether and the boron- and hydrogen-containing silicone oil, measured by Pt. Step C: Mix 40 parts of aminated wollastonite, 20 parts of terminal epoxy polyether modified trisiloxane and 200 parts of tetrahydrofuran evenly, and react at 45°C for 11 hours to obtain modified wollastonite. The preparation method of the flame retardant crosslinking agent is as follows: Step 1: Esterification reaction of pentaerythritol and phosphoric acid at a molar ratio of 1:2 (reaction temperature 110℃, reaction time 4h) to obtain pentaerythritol phosphate liquid; mix 16 parts of melamine and 180 parts of deionized water evenly, heat to 70℃, add 19.2 parts of pentaerythritol phosphate liquid, react at 90℃ for 5h, and after centrifugation, dehydration and drying, obtain pentaerythritol phosphate melamine salt; Step 2: Mix 8 parts of terminal epoxy polyether modified trisiloxane, 16 parts of pentaerythritol phosphate melamine salt and 40 parts of N,N-dimethylformamide evenly, and react at 45°C for 7 hours to obtain a flame retardant crosslinking agent.

[0029] Example 3: A method for preparing a high-strength silicone sealant, comprising the following processes: 120 parts of α,ω-dihydroxypolydimethylsiloxane were added to a kneader, along with 50 parts of modified wollastonite, 20 parts of zinc borate, 10 parts of flame retardant crosslinking agent, and 30 parts of dimethyl silicone oil. The mixture was stirred evenly, heated to 130°C, and vacuum kneaded for 3 hours. After cooling to room temperature, the base material was obtained. The base material and 15 parts of ketoxime crosslinking agent were added to a planetary mixer and stirred for 20 minutes. 70 parts of fumed silica, 3 parts of coupling agent, and 5 parts of catalyst were added and stirred for 120 minutes under a vacuum of -0.10 MPa. The mixture was then sealed and packaged to obtain a high-strength silicone sealant. The preparation method of modified wollastonite is as follows: Step A: Disperse 50 parts of wollastonite ultrasonically in a mixed solution of 600 parts of anhydrous ethanol and 250 parts of deionized water, adjust the pH to 11 by adding ammonia dropwise, add 125 parts of tetraethyl orthosilicate and 40 parts of 3-aminopropyltrimethoxysilane, react at 70°C for 24 hours, and obtain aminated wollastonite after filtration, washing and drying. Step B: Under nitrogen protection, 1,1,1,3,5,5,5-heptamethyltrisiloxane and terminal epoxy-based allyl polyether were mixed evenly at a molar ratio of 1:1.2, and a chloroplatinic acid-isopropanol solution was added. The mixture was reacted at 85°C for 6 hours, followed by vacuum distillation to obtain terminal epoxy-based polyether modified trisiloxane. The amount of chloroplatinic acid-isopropanol solution used was 4 ppm of the total mass of the terminal epoxy-based allyl polyether and the boron- and hydrogen-containing silicone oil, measured by Pt. Step C: Mix 50 parts of aminated wollastonite, 30 parts of terminal epoxy polyether modified trisiloxane and 300 parts of tetrahydrofuran evenly, and react at 50°C for 12 hours to obtain modified wollastonite. The preparation method of the flame retardant crosslinking agent is as follows: Step 1: Esterification reaction of pentaerythritol and phosphoric acid at a molar ratio of 1:2 (reaction temperature 120℃, reaction time 6h) to obtain pentaerythritol phosphate liquid; mix 30 parts of melamine and 360 parts of deionized water evenly, heat to 80℃, add 39 parts of pentaerythritol phosphate liquid, react at 100℃ for 6h, and after centrifugation, dehydration and drying, obtain pentaerythritol phosphate melamine salt; Step 2: Mix 10 parts of terminal epoxy polyether modified trisiloxane, 30 parts of pentaerythritol phosphate melamine salt and 60 parts of N,N-dimethylformamide evenly, and react at 50°C for 8 hours to obtain a flame retardant crosslinking agent.

[0030] Comparative Example 1: A method for preparing a high-strength silicone sealant, comprising the following processes: 110 parts of α,ω-dihydroxypolydimethylsiloxane were added to a kneader, along with 40 parts of modified wollastonite, 15 parts of zinc borate, 8 parts of dimethoxymethylvinylsilane, and 25 parts of dimethyl silicone oil. The mixture was stirred until homogeneous, heated to 125°C, and kneaded under vacuum for 2 hours. After cooling to room temperature, the base material was obtained. The base material and 12 parts of ketoxime crosslinking agent were added to a planetary mixer and stirred for 15 minutes. Then, 60 parts of fumed silica, 2 parts of coupling agent, and 3 parts of catalyst were added. The mixture was stirred for 100 minutes under a vacuum of -0.09 MPa. The mixture was then sealed and packaged to obtain a high-strength silicone sealant. Comparative Example 1 is based on Example 2, except that the flame retardant crosslinking agent is replaced with the same mass of dimethoxydimethylsilane, and the remaining process steps and reaction parameters are the same as in Example 2.

[0031] Comparative Example 2: A method for preparing a high-strength silicone sealant, comprising the following processes: 110 parts of α,ω-dihydroxypolydimethylsiloxane were added to a kneader, along with 40 parts of wollastonite, 15 parts of zinc borate, 8 parts of flame retardant crosslinking agent, and 25 parts of dimethyl silicone oil. The mixture was stirred until homogeneous, heated to 125°C, and vacuum kneaded for 2 hours. After cooling to room temperature, the base material was obtained. The base material and 12 parts of ketoxime crosslinking agent were added to a planetary mixer and stirred for 15 minutes. 60 parts of fumed silica, 2 parts of coupling agent, and 3 parts of catalyst were added and stirred for 100 minutes under a vacuum of -0.09 MPa. The mixture was then sealed and packaged to obtain a high-strength silicone sealant. Comparative Example 2 is based on Example 2, except that the modified wollastonite is replaced with the same mass of wollastonite, and the remaining process steps and reaction parameters are the same as in Example 2.

[0032] Comparative Example 3: A method for preparing a high-strength silicone sealant, comprising the following processes: The preparation method of modified wollastonite is as follows: Step A: 40 parts of wollastonite were ultrasonically dispersed in a mixed solution of 440 parts of anhydrous ethanol and 160 parts of deionized water. Ammonia was added dropwise to adjust the pH to 10.5. 80 parts of tetraethyl orthosilicate and 20 parts of 3-aminopropyltrimethoxysilane and anhydrous ethanol were added. The mixture was reacted at 65°C for 20 hours. After filtration, washing and drying, aminated wollastonite was obtained. Step B: Mix 40 parts of aminated wollastonite, 20 parts of terminal epoxy allyl polyether and 200 parts of tetrahydrofuran evenly, and react at 45°C for 11 hours to obtain modified wollastonite. Comparative Example 3 is based on Example 2, except that the terminal epoxy polyether modified trisiloxane is replaced with the same mass of terminal epoxy allyl polyether, and the remaining process steps and reaction parameters are the same as those in Example 2.

[0033] Comparative Example 4: A method for preparing a high-strength silicone sealant, comprising the following processes: 110 parts of α,ω-dihydroxypolydimethylsiloxane were added to a kneader, along with 40 parts of modified wollastonite, 15 parts of zinc borate, 8 parts of pentaerythritol phosphate melamine salt, and 25 parts of dimethyl silicone oil. The mixture was stirred until homogeneous, heated to 125°C, and vacuum kneaded for 2 hours. After cooling to room temperature, the base material was obtained. The base material and 12 parts of ketoxime crosslinking agent were added to a planetary mixer and stirred for 15 minutes. 60 parts of fumed silica, 2 parts of coupling agent, and 3 parts of catalyst were added and stirred for 100 minutes under a vacuum of -0.09 MPa. The mixture was then sealed and packaged to obtain a high-strength silicone sealant. Comparative Example 4 is based on Example 2, except that the flame retardant crosslinking agent is replaced with the same mass of pentaerythritol phosphate melamine salt, and the remaining process steps and reaction parameters are the same as in Example 2.

[0034] Experiment: High-strength silicone sealants obtained in Examples 1-3 and Comparative Examples 1-4 were used to prepare samples. Their properties were tested and the test results were recorded. Tensile strength and elongation at break: Performed in accordance with GB / T 528-2009 standard, tested on a tensile testing machine at a tensile speed of 500 mm / min, and the tensile strength and elongation at break were recorded; Vertical burning test: Performed in accordance with UL94-2009 standard, the silicone sealant sample size was 120 mm × 12.7 mm × 3.2 mm.

[0035] The test results are shown in Table 1.

[0036] Table 1 Performance test results of high-strength silicone sealant Based on the data in the table above, the following conclusions can be clearly drawn: The silicone sealants prepared in Examples 1-3 possess excellent mechanical and flame-retardant properties. Compared to Examples 1-3, the flame-retardant properties of the product obtained in Comparative Example 1 decreased, indicating that the flame-retardant crosslinking agent prepared in this invention has a better flame-retardant effect than ordinary crosslinking agents (dimethoxymethylvinylsilane); the tensile strength of the products obtained in Comparative Examples 2 and 3 both decreased, indicating that this invention effectively improves the mechanical properties of the material by modifying wollastonite; compared to terminal epoxy-based allyl polyethers, the terminal epoxy polyether-modified trisiloxane prepared in this invention has a better modification effect, thereby improving the compatibility between the material and the base adhesive; the tensile strength and elongation at break of the product obtained in Comparative Example 4 both decreased, indicating that this invention introduces a flame-retardant crosslinking agent by reacting terminal epoxy polyether-modified trisiloxane with pentaerythritol phosphate melamine salt, thereby obtaining the flame-retardant crosslinking agent.

[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A process for the preparation of high strength silicone sealant, characterized by: It comprises the following steps: The alpha, omega-dihydroxy polydimethylsiloxane is added into a kneader, the modified wollastonite, zinc borate, flame-retardant crosslinking agent and dimethyl silicone oil are added and mixed uniformly, the temperature is raised to 120-130 DEG C, vacuum kneading is carried out for 1-3 h, after cooling to room temperature, the base material is obtained; the base material and ketoxime crosslinking agent are mixed, stirring is carried out for 10-20 min, fumed white carbon black, coupling agent and catalyst are added, vacuum stirring is carried out for 60-120 min, sealing packaging is carried out, and the high-strength silicone sealant is obtained.

2. The method for preparing a high-strength silicone sealant according to claim 1, characterized in that: The high-strength silicone sealant is composed of the following components in parts by weight: alpha, omega-dihydroxy polydimethylsiloxane 100-120 parts, modified wollastonite 30-50 parts, zinc borate 10-20 parts, flame-retardant crosslinking agent 5-10 parts, dimethyl silicone oil 15-30 parts, fumed white carbon black 50-70 parts, ketoxime crosslinking agent 10-15 parts, catalyst 2-5 parts and coupling agent 1-3 parts.

3. The method for preparing a high-strength silicone sealant according to claim 2, characterized in that: The preparation method of the modified wollastonite is as follows: Step A: the wollastonite is ultrasonically dispersed in a mixed solution of anhydrous ethanol and deionized water, ammonia water is added dropwise to adjust pH to 10-11, tetraethyl orthosilicate and 3-aminopropyltrimethoxysilane are added, reaction is carried out at 60-70 DEG C for 12-24 h, after filtration, washing and drying, the aminated wollastonite is obtained; Step B: under nitrogen protection, 1,1,1,3,5,5,5-heptamethyltrisiloxane and epoxy-terminated allyl polyether are uniformly mixed, chloroplatinic acid-isopropyl alcohol solution is added, reaction is carried out at 75-85 DEG C for 4-6 h, and vacuum distillation is carried out, and the epoxy-terminated polyether modified trisiloxane is obtained; Step C: the aminated wollastonite, epoxy-terminated polyether modified trisiloxane and tetrahydrofuran are uniformly mixed, reaction is carried out at 40-50 DEG C for 10-12 h, after filtration, washing and drying, the modified wollastonite is obtained.

4. The method for preparing a high-strength silicone sealant according to claim 3, characterized in that: In step B, the molar ratio of 1,1,1,3,5,5,5-heptamethyltrisiloxane and epoxy-terminated allyl polyether is 1: (1.0-1.2).

5. The method for preparing a high-strength silicone sealant according to claim 3, characterized in that: In step C, the mass ratio of aminated wollastonite, epoxy-terminated polyether modified trisiloxane and tetrahydrofuran is 1: (0.3-0.6): (4-6).

6. The method for preparing a high-strength silicone sealant according to claim 2, characterized in that: The preparation method of the flame-retardant crosslinking agent is as follows: Step 1: esterification reaction is carried out on pentaerythritol and phosphoric acid to obtain pentaerythritol phosphate liquid; melamine and deionized water are uniformly mixed, the temperature is raised to 60-80 DEG C, pentaerythritol phosphate liquid is added, reaction is carried out at 80-100 DEG C for 4-6 h, after centrifugal dewatering and drying, the pentaerythritol phosphate melamine salt is obtained; Step 2: the epoxy-terminated polyether modified trisiloxane, pentaerythritol phosphate melamine salt and N,N-dimethylformamide are uniformly mixed, reaction is carried out at 40-50 DEG C for 6-8 h, after filtration, washing and drying, the flame-retardant crosslinking agent is obtained.

7. The method for preparing a high-strength silicone sealant according to claim 6, characterized in that: In step 2, the mass ratio of epoxy-terminated polyether modified trisiloxane, pentaerythritol phosphate melamine salt and N,N-dimethylformamide is 1: (1-3): (4-6).

8. The method for preparing a high-strength silicone sealant according to claim 1, characterized in that: The catalyst is one or two of dibutyl tin diacetate, dibutyl tin dilaurate, dibutyl tin diacetylacetone and dibutyl tin diacetylacetate.

9. The method for preparing a high-strength silicone sealant according to claim 1, characterized in that: The ketoxime crosslinking agent is two or more kinds of mixture of methyl tributanone oxime silane, vinyl tributanone oxime silane, phenyl tributanone oxime silane, tetrabutanone oxime silane.

10. A high-strength silicone sealant prepared by the method according to any one of claims 1 to 9.

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