Low-modulus bi-component silane modified sealant for silicon carbide ceramics and preparation method of low-modulus bi-component silane modified sealant

Abstract

The invention discloses a low-modulus bi-component silane modified sealant for silicon carbide ceramics and a preparation method of the low-modulus bi-component silane modified sealant, and relates to the technical field of sealants. The sealant is prepared by mixing a component A and a component B according to a mass ratio of (10-25): 1, the component A is prepared from silane modified polyether resin, a polyurea type thixotropic agent containing a plasticizer, a titanium modified siloxane bonding aid, heavy calcium carbonate, bifunctional polyether polyol and the like; the component B is composed of an amine catalyst, an organic tin catalyst and deionized water; the tensile strength of the low-modulus bi-component silane modified sealant for the silicon carbide ceramic is larger than or equal to 2.5 MPa, the 100% tensile modulus is smaller than or equal to 0.6 MPa, the prime coat-free tensile shear strength of the sealant and the silicon carbide ceramic is larger than or equal to 2.0 MPa, the mechanical property retention rate in the wide temperature range of-40 DEG C to 120 DEG C is larger than or equal to 85%, and the mechanical property retention rate in the wide temperature range is larger than or equal to 90%. The adhesive is suitable for sealing and bonding silicon carbide components in the field of military equipment such as land chariots and combat preparedness armors and semiconductors.

Description

Technical Field

[0001] This invention relates to the field of sealant technology, specifically to a low-modulus two-component silane-modified sealant for silicon carbide ceramics and its preparation method. Background Technology

[0002] Silicon carbide special ceramics are widely used in high-end equipment due to their high temperature resistance, high hardness, and strong chemical inertness. However, existing silane-modified sealants (MS sealants) have three main problems when bonding with silicon carbide ceramics: First, the hydroxyl content on the surface of silicon carbide is extremely low, and conventional silane coupling agents can only form single-site bonds, resulting in tensile bond strengths generally below 1.0 MPa. Second, existing thixotropic agents (such as fumed silica and organobentonite) increase the cohesive force of the system through physical accumulation when improving thixotropy, which increases the sealant modulus and cannot adapt to the small deformations after assembly of silicon carbide components. Third, silicon carbide components are often in a wide temperature range of -40℃ to 120℃, and existing single-component MS sealants cure very slowly at low temperatures (≤0℃), directly affecting subsequent construction, and their mechanical properties degrade severely at high temperatures (tensile strength loss ≥30% at 120℃).

[0003] Therefore, there is an urgent need to develop a sealant that bonds well to silicon carbide ceramics and can achieve wide temperature range curing and high mechanical stability. Summary of the Invention

[0004] To address the problems of weak adhesion between existing sealants and silicon carbide ceramics, wide-temperature-range curing, and poor mechanical stability, the present invention aims to provide a low-modulus two-component silane-modified sealant for silicon carbide ceramics and its preparation method.

[0005] To achieve the above objectives, the present invention employs the following technical solution: A low-modulus two-component silane-modified sealant for silicon carbide ceramics is obtained by mixing component A and component B in a mass ratio of 10-25:1. By weight, component A comprises: 45-65 parts of silane-modified polyether resin, 10-35 parts of a polyurea-type thixotropic agent containing a plasticizer, 3-7 parts of titanium-modified siloxane adhesive additive, 10-30 parts of heavy calcium carbonate, 5-20 parts of difunctional polyether polyol, 0.8-1.5 parts of antioxidant, 0.5-1 part of ultraviolet absorber, 0.5-1.5 parts of adhesion promoter, and 0.5-2.0 parts of dehydrating agent. Component B comprises: 2.5-4 parts of amine catalyst, 1-5 parts of organotin catalyst, and 2-7 parts of deionized water.

[0006] Preferably, the titanium-modified siloxane adhesive is prepared according to the following steps: Add silane coupling agent, hydrogen-containing silicone oil and alcohol solvent to the reaction vessel, stir and react for 15-20 minutes under nitrogen protection, add titanate coupling agent, continue stirring for 20-25 minutes, add Karstedt catalyst, stir for 5-10 minutes to disperse it evenly, and obtain a mixture. Add tetrabutyl titanate dropwise to the mixture. After the addition is complete, heat the reactor to 50-60°C and react for 1-2 hours. Add deionized water and stir for 10-15 minutes to terminate the reaction. Cool to 20-30°C and remove the solvent and water by vacuum distillation to obtain titanium-modified siloxane adhesive. The silane coupling agent is vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, or γ-aminopropyltriethoxysilane; The hydrogen-containing silicone oil is tetramethylcyclotetrasiloxane or hexamethyldisiloxane; The alcohol solvent is ethanol or isopropanol; The titanate coupling agent is KR-138S, KR-55 or NDZ-101; The mass ratio of silane coupling agent, hydrogen-containing silicone oil, alcohol solvent, titanate coupling agent, Karstedt catalyst, tetrabutyl titanate and deionized water is 100:30~50:150~200:10~20:0.1~0.3:20~40:5~10.

[0007] Preferably, the polyurea-type thixotropic agent containing plasticizer is prepared according to the following steps: After vacuum dehydration, the plasticizer is mixed and dispersed with small molecule amine under nitrogen protection. Polyisocyanate is added dropwise at 40~65℃. After the addition is complete, the reaction is kept at 70~90℃ for 2~4 hours. After cooling to 20~30℃, the mixture is filtered to obtain a polyurea-type thixotropic agent containing plasticizer. The plasticizer is one or two of the following: dioctyl adipate, trioctyl trimellitate, dioctyl sebacate, or tributyl citrate. The small molecule amine is ethylenediamine, cyclohexanediamine, 1,6-hexanediamine, diethylenetriamine, or triethylenetetramine; The polyisocyanate is one or two of hexamethylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate or 4-fluorophenyl isocyanate; The mass ratio of plasticizer, small molecule amine and polyisocyanate is 100:5~12:15~25.

[0008] Preferably, the silane-modified polyether resin is one of Kaneka Corporation's MAX602, Asahi Glass's S2410E, Nanjing Qingqi's 250S or 410E.

[0009] Preferably, the antioxidant is antioxidant 3114, antioxidant HP136, or antioxidant 425.

[0010] Preferably, the ultraviolet absorber is UV-3808PP5, UV-1130, or Tinuvin 770DF.

[0011] Preferably, the adhesion promoter is γ-ureopropyltriethoxysilane, bis(γ-trimethoxysilylpropyl)amine, or N-phenyl-γ-aminopropyltrimethoxysilane.

[0012] Preferably, the dehydrating agent is methyltris(methylethyl ketone oxime)silane, MTMS, or silane coupling agent A-172.

[0013] Preferably, the amine catalyst is one or two of triethylenediamine, N,N-dimethylbenzylamine, 2,4,6-tris(dimethylaminomethyl)phenol, or diethylenetriamine; the organotin catalyst is one or two of dibutyltin dilaurate, dibutyltin bis(acetylacetonate), dibutyltin dioctanoate, or dibutyltin oxide.

[0014] This invention also includes a method for preparing a low-modulus two-component silane-modified sealant for silicon carbide ceramics, comprising the following steps: ① Preparation of Component A: By weight, 45-65 parts of silane-modified polyether resin, 10-35 parts of polyurea-type thixotropic agent containing plasticizer, and 3-7 parts of titanium-modified siloxane adhesive additive are added to a mixer and stirred for 10-15 minutes. Then, 10-30 parts of heavy calcium carbonate, 5-20 parts of difunctional polyether polyol, 0.8-1.5 parts of antioxidant, 0.5-1 part of ultraviolet absorber, 0.5-1.5 parts of adhesion promoter, and 0.5-2.0 parts of dehydrating agent are added. The mixture is stirred for 35-45 minutes under a vacuum of -0.09 to -0.095 MPa, and Component A is obtained by discharging the material. ② Preparation of component B: Mix 2.5-4 parts of amine catalyst, 1-5 parts of organotin catalyst and 2-7 parts of deionized water evenly to obtain component B; ③ Mix component A obtained in step ① and component B obtained in step ② at a mass ratio of 10~25:1 to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics.

[0015] The present invention has the following advantages over the prior art: The low-modulus two-component silane-modified sealant for silicon carbide ceramics of the present invention has a tensile strength ≥2.5MPa and a 100% tensile modulus ≤0.6MPa after room temperature treatment, and a primerless tensile shear strength of silicon carbide ceramics ≥2.5MPa. The mechanical properties retain ≥85% in a wide temperature range of -40℃ to 120℃. It is suitable for sealing and bonding of silicon carbide components in military equipment such as land vehicles and armored vehicles, as well as in the semiconductor field.

[0016] The two-component silane-modified sealant of the present invention contains a titanium-modified siloxane adhesive aid. The adhesive aid is constructed from silane coupling agents and hydrogen-containing silicone oil to form a flexible and compatible organosilicon framework. Ti-O-Si coordination bonds are formed through the synergistic effect of titanate coupling agents and tetrabutyl titanate to strengthen interfacial bonding. The reaction efficiency is controlled by Karstedt catalyst, and the component homogeneity is ensured by using alcohol solvents as dispersion media. The reaction is terminated with deionized water and excess titanium components are hydrolyzed. The adhesive aid forms a dual coordination structure of Si-OC bonds and Ti-O-Si bonds with the silicon carbide surface, enabling the sealant to bond to silicon carbide ceramics without a primer.

[0017] The two-component silane-modified sealant of this invention contains a polyurea-type thixotropic agent. This polyurea-type thixotropic agent forms strong hydrogen bonds between the NH groups of the urea bonds and the C=O groups of another urea bond through a reaction between amines and polyisocyanates. Multiple molecular chains intertwine through these hydrogen bonds, forming a three-dimensional network structure. By constructing a physically cross-linked network through dynamically reversible non-covalent bonds (hydrogen bonds, hydrophobic interactions), a thixotropic cycle of "thickening upon standing and thinning upon shearing" is achieved, thereby endowing the product with excellent thixotropic properties and ensuring workability and anti-sagging properties.

[0018] On the other hand, polyurea thixotropic agents have a reversible thixotropic effect due to the hydrogen bond network formed between urea bonds, but they suffer from severe yellowing, insufficient thixotropic efficiency, or excessively high system viscosity. This technology improves the reaction compatibility and optimizes the performance of the product by adding plasticizers to polyurea thixotropic agents to adjust the reaction medium and properties. Detailed Implementation

[0019] The purpose of this invention is to provide a low-modulus two-component silane-modified sealant for silicon carbide ceramics and its preparation method, which is achieved through the following technical solution: The polyurea-type thixotropic agent in this invention is obtained by reacting amines with polyisocyanates. The amino group undergoes a nucleophilic addition reaction with the isocyanate group, and the lone pair electrons of the amino group attack the carbonyl carbon of the isocyanate, forming an unstable urethane intermediate. This intermediate rapidly rearranges, releasing carbon dioxide and forming a urea bond (-NH-CO-NH-). Simultaneously, the other amino group of the amine can continue to react with the isocyanate, achieving cross-linking. The reaction equation is as follows:

[0020] Amine compounds act as chain extenders or crosslinking agents in the reaction, which determines the structure and properties of polyurea.

[0021] The alcohol solvents of this invention need to be dehydrated before use.

[0022] The present invention will be further described below with reference to specific embodiments. Example

[0023] A low-modulus two-component silane-modified sealant for silicon carbide ceramics is obtained by mixing component A and component B in a mass ratio of 10:1. Component A consists of the following components: 45 kg of silane-modified polyether resin, 10 kg of polyurea-type thixotropic agent containing plasticizer, 3 kg of titanium-modified siloxane adhesive additive, 10 kg of heavy calcium carbonate, 5 kg of difunctional polyether polyol, 0.8 kg of antioxidant 3114, 0.5 kg of ultraviolet absorber UV-3808PP5, 0.5 kg of γ-ureidopropyltriethoxysilane, and 0.5 kg of methyltris(methylethyl ketone oxime)silane. Component B consists of the following components: 3.5 kg of triethylenediamine, 1.4 kg of dibutyltin dilaurate, and 2.8 kg of deionized water. Mix 75 kg of component A and 7.5 kg of component B to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics; The silane-modified polyether resin is Kaneka's MAX602 from Japan. The polyurea-type thixotropic agent containing plasticizer is prepared according to the following steps: 10 kg of dioctyl adipate was dehydrated under vacuum and then mixed and dispersed with 0.5 kg of ethylenediamine under nitrogen protection. 1.5 kg of hexamethylene diisocyanate (HDI) was added dropwise at 40 °C. After the addition was completed, the mixture was kept at 70 °C for 4 hours, cooled to 20 °C, and filtered to obtain a polyurea-type thixotropic agent containing plasticizer. The titanium-modified siloxane adhesive was prepared according to the following steps: 5 kg of vinyltrimethoxysilane, 1.5 kg of tetramethylcyclotetrasiloxane and 7.5 kg of ethanol were added to a reaction vessel and stirred for 15 minutes under nitrogen protection. Then, 0.5 kg of titanate coupling agent was added and stirred for another 20 minutes. Finally, 0.005 kg of Karstedt catalyst was added and stirred for 5 minutes to disperse the mixture evenly. Add 1 kg of tetrabutyl titanate KR-138S dropwise to the mixture. After the addition is complete, heat the reactor to 50°C and react for 1 hour. Add 0.25 kg of deionized water and stir for 10 minutes to terminate the reaction. Cool to 20°C and remove the solvent and water by vacuum distillation to obtain titanium-modified siloxane adhesive. Example

[0024] A low-modulus two-component silane-modified sealant for silicon carbide ceramics is obtained by mixing component A and component B in a mass ratio of 25:1. Component A consists of the following components: 65 kg of silane-modified polyether resin, 35 kg of polyurea-type thixotropic agent containing plasticizer, 7 kg of titanium-modified siloxane adhesive additive, 30 kg of heavy calcium carbonate, 20 kg of difunctional polyether polyol, 1.5 kg of antioxidant HP136, 1 kg of ultraviolet absorber UV-1130, 1.5 kg of bis(γ-trimethoxysilylpropyl)amine, and 2.0 kg of dehydrating agent MTMS. Component B consists of the following components: 4 kg of N,N-dimethylbenzylamine, 5 kg of dibutyltin bis(acetylacetone) and 7 kg of deionized water; 160 kg of component A and 6.4 kg of component B were mixed to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics; The silane-modified polyether resin is S2410E from Asahi Glass Co., Ltd. (AGC). The polyurea-type thixotropic agent containing plasticizer is prepared according to the following steps: 30 kg of trioctyl trimellitate was dehydrated under vacuum and then mixed and dispersed with 3.6 kg of cyclohexanediamine under nitrogen protection. 7.5 kg of diphenylmethane diisocyanate (MDI) was added dropwise at 65 °C. After the addition was completed, the reaction was kept at 90 °C for 4 hours, cooled to 30 °C, and filtered to obtain a polyurea-type thixotropic agent containing plasticizer. The titanium-modified siloxane adhesive was prepared according to the following steps: 4 kg of γ-glycidyl etheroxypropyltrimethoxysilane, 2 kg of hexamethyldisiloxane and 8 kg of ethanol were added to a reaction vessel and stirred for 20 minutes under nitrogen protection. Then, 0.8 kg of titanate coupling agent KR-55 was added and stirred for another 25 minutes. Finally, 0.012 kg of Karstedt catalyst was added and stirred for 10 minutes to disperse the mixture evenly. 1.6 kg of tetrabutyl titanate was added dropwise to the mixture. After the addition was complete, the reaction vessel was heated to 60°C and reacted for 2 hours. Then, 0.4 kg of deionized water was added and the reaction was stopped by stirring for 15 minutes. The mixture was cooled to 30°C and the solvent and water were removed by vacuum distillation to obtain the titanium-modified siloxane adhesive. Example

[0025] A low-modulus two-component silane-modified sealant for silicon carbide ceramics is obtained by mixing component A and component B in a mass ratio of 15:1. Component A consists of the following components: 50 kg of silane-modified polyether resin, 20 kg of polyurea-type thixotropic agent containing plasticizer, 4 kg of titanium-modified siloxane adhesive additive, 15 kg of heavy calcium carbonate, 10 kg of difunctional polyether polyol, 1 kg of antioxidant 425, 0.6 kg of ultraviolet absorber Tinuvin 770DF, 0.6 kg of N-phenyl-γ-aminopropyltrimethoxysilane, and 0.6 kg of silane coupling agent A-172. Component B consists of the following components: 3 kg of 2,4,6-tris(dimethylaminomethyl)phenol, 2 kg of dibutyltin dioctanoate, and 3 kg of deionized water. Mix 90 kg of component A and 6 kg of component B to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics; The silane-modified polyether resin is 250S from Nanjing Qingqi Company. The polyurea-type thixotropic agent containing plasticizer is prepared according to the following steps: 20 kg of trioctyl trimellitate was dehydrated under vacuum and then mixed and dispersed with 1.2 kg of 1,6-hexanediamine under nitrogen protection. 3.2 kg of isophorone diisocyanate (IPDI) was added dropwise at 50 °C. After the addition was complete, the reaction was maintained at 75 °C for 2.5 hours. The mixture was then cooled to 25 °C and filtered to obtain a polyurea-type thixotropic agent containing plasticizer. The titanium-modified siloxane adhesive was prepared according to the following steps: 3 kg of γ-aminopropyltriethoxysilane, 1.05 kg of tetramethylcyclotetrasiloxane and 4.8 kg of isopropanol were added to a reaction vessel and stirred for 16 minutes under nitrogen protection. Then, 0.36 kg of titanate coupling agent NDZ-101 was added and stirred for another 22 minutes. Finally, 4.5 g of Karstedt catalyst was added and stirred for 6 minutes to disperse the mixture evenly. Add 0.75 kg of tetrabutyl titanate dropwise to the mixture. After the addition is complete, heat the reactor to 52°C and react for 1.5 hours. Add 0.18 kg of deionized water and stir for 12 minutes to terminate the reaction. Cool to 22°C and remove the solvent and water by vacuum distillation to obtain titanium-modified siloxane adhesive. Example

[0026] A low-modulus two-component silane-modified sealant for silicon carbide ceramics is obtained by mixing component A and component B in a mass ratio of 22:1. Component A consists of the following components: 60 kg of silane-modified polyether resin, 25 kg of polyurea-type thixotropic agent containing plasticizer, 6 kg of titanium-modified siloxane adhesive additive, 25 kg of heavy calcium carbonate, 15 kg of difunctional polyether polyol, 1.2 kg of antioxidant 3114, 0.8 kg of ultraviolet absorber UV-1130, 0.8 kg of N-phenyl-γ-aminopropyltrimethoxysilane, and 1.6 kg of methyltris(methylethyl ketone oxime)silane. Component B consists of the following components: 1.5 kg of triethylenediamine, 2 kg of diethylenetriamine, 2 kg of dibutyltin dilaurate, 1 kg of dibutyltin bis(acetylacetone), and 6 kg of deionized water. 132 kg of component A and 6 kg of component B were mixed to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics. The silane-modified polyether resin is 410E from Nanjing Qingqi Company. The polyurea-type thixotropic agent containing plasticizer is prepared according to the following steps: 25 kg of tributyl citrate was dehydrated under vacuum and then mixed and dispersed with 2.5 kg of diethylenetriamine under nitrogen protection. 4.5 kg of 4-fluorophenyl isocyanate was added dropwise at 55 °C. After the addition was completed, the mixture was kept at 85 °C for 3 hours, cooled to 25 °C, and filtered to obtain a polyurea-type thixotropic agent containing plasticizer. The titanium-modified siloxane adhesive was prepared according to the following steps: 4 kg of vinyltrimethoxysilane, 1.6 kg of hexamethyldisiloxane and 7.2 kg of isopropanol were added to the reactor and stirred for 18 minutes under nitrogen protection. Then, 0.6 kg of titanate coupling agent KR-55 was added and stirred for another 24 minutes. Finally, 8 g of Karstedt catalyst was added and stirred for 6 minutes to disperse the mixture evenly. 1.2 kg of tetrabutyl titanate was added dropwise to the mixture. After the addition was complete, the reaction vessel was heated to 54°C and reacted for 1.5 hours. 0.32 kg of deionized water was added and the reaction was stopped by stirring for 12 minutes. The mixture was then cooled to 24°C and the solvent and water were removed by vacuum distillation to obtain the titanium-modified siloxane adhesive. Example

[0027] A low-modulus two-component silane-modified sealant for silicon carbide ceramics is obtained by mixing component A and component B in a mass ratio of 20:1. Component A consists of the following components: 50 kg of silane-modified polyether resin, 25 kg of polyurea-type thixotropic agent containing plasticizer, 5 kg of titanium-modified siloxane adhesive additive, 15 kg of heavy calcium carbonate, 15 kg of difunctional polyether polyol, 1.2 kg of antioxidant 425, 0.7 kg of ultraviolet absorber UV-3808PP5, 1.2 kg of γ-ureidopropyltriethoxysilane, and 1.5 kg of silane coupling agent A-172. Component B consists of the following components: 2 kg of N,N-dimethylbenzylamine, 1 kg of 2,4,6-tris(dimethylaminomethyl)phenol, 2 kg of dibutyltin dioctanoate, 1 kg of dibutyltin oxide, and 5 kg of deionized water. Mix 110 kg of component A and 5.5 kg of component B to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics; The silane-modified polyether resin is S2410E from Asahi Glass Co., Ltd. (AGC). The polyurea-type thixotropic agent containing plasticizer is prepared according to the following steps: 15 kg of dioctyl adipate and 10 kg of trioctyl trimellitate were vacuum dehydrated and then mixed and dispersed with 2.5 kg of triethylenetetramine under nitrogen protection. 3 kg of hexamethylene diisocyanate (HDI) and 2 kg of diphenylmethane diisocyanate (MDI) were added dropwise at 55 °C. After the addition was complete, the mixture was kept at 80 °C for 2.5 hours, cooled to 25 °C, and filtered to obtain a polyurea-type thixotropic agent containing plasticizer. The titanium-modified siloxane adhesive was prepared according to the following steps: 3 kg of γ-glycidyl etheroxypropyltrimethoxysilane, 1.05 kg of tetramethylcyclotetrasiloxane and 4.8 kg of isopropanol were added to a reaction vessel and stirred for 16 minutes under nitrogen protection. Then, 0.36 kg of titanate coupling agent KR-138S was added and stirred for another 24 minutes. Finally, 4.8 g of Karstedt catalyst was added and stirred for 6 minutes to disperse the mixture evenly. 1.08 kg of tetrabutyl titanate was added dropwise to the mixture. After the addition was complete, the reaction vessel was heated to 55°C and reacted for 1.5 hours. 0.24 kg of deionized water was added and the reaction was stopped by stirring for 14 minutes. The mixture was then cooled to 25°C and the solvent and water were removed by vacuum distillation to obtain the titanium-modified siloxane adhesive. Example

[0028] A low-modulus two-component silane-modified sealant for silicon carbide ceramics is obtained by mixing component A and component B in a mass ratio of 18:1. Component A consists of the following components: 55 kg of silane-modified polyether resin, 25 kg of polyurea-type thixotropic agent containing plasticizer, 5 kg of titanium-modified siloxane adhesive additive, 20 kg of heavy calcium carbonate, 10 kg of difunctional polyether polyol, 1 kg of antioxidant HP136, 0.8 kg of ultraviolet absorber UV-1130, 1 kg of bis(γ-trimethoxysilylpropyl)amine, and 1 kg of dehydrating agent MTMS. Component B consists of the following components: 3 kg of diethylenetriamine, 1.5 kg of dibutyltin bis(acetylacetone), 1.5 kg of dibutyltin dioctanoate, and 5 kg of deionized water. 108 kg of component A and 6 kg of component B were mixed to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics. The silane-modified polyether resin is 250S from Nanjing Qingqi Company. The polyurea-type thixotropic agent containing plasticizer is prepared according to the following steps: 10 kg of dioctyl sebacate and 15 kg of tributyl citrate were dehydrated under vacuum and then mixed and dispersed with 2 kg of cyclohexanediamine under nitrogen protection. 4 kg of 4-fluorophenyl isocyanate was added dropwise at 55 °C. After the addition was completed, the mixture was kept at 80 °C for 3 hours, cooled to 25 °C, and filtered to obtain a polyurea-type thixotropic agent containing plasticizer. The titanium-modified siloxane adhesive was prepared according to the following steps: 3 kg of γ-aminopropyltriethoxysilane, 1.2 kg of tetramethylcyclotetrasiloxane and 5.4 kg of ethanol were added to a reaction vessel and stirred for 16 minutes under nitrogen protection. Then, 0.45 kg of titanate coupling agent NDZ-101 was added and stirred for another 24 minutes. Finally, 4.5 g of Karstedt catalyst was added and stirred for 6 minutes to disperse the mixture evenly. Add 0.9 kg of tetrabutyl titanate dropwise to the mixture. After the addition is complete, heat the reactor to 55°C and react for 1.5 hours. Add 0.18 kg of deionized water and stir for 12 minutes to terminate the reaction. Cool to 22°C and remove the solvent and water by vacuum distillation to obtain titanium-modified siloxane adhesive. Example

[0029] The preparation method of the low-modulus two-component silane-modified sealant for silicon carbide ceramics described in Example 1 includes the following steps: ① Preparation of Component A: Add 45 kg of silane-modified polyether resin, 10 kg of polyurea-type thixotropic agent containing plasticizer, and 3 kg of titanium-modified siloxane adhesive to a mixer and stir for 10-15 minutes. Then add 10 kg of heavy calcium carbonate, 5 kg of difunctional polyether polyol, 0.8 kg of antioxidant 3114, 0.5 kg of ultraviolet absorber UV-3808PP5, 0.5 kg of γ-ureidopropyltriethoxysilane, and 0.5 kg of methyltris(methylethyl ketone oxime)silane. Stir under a vacuum of -0.09 to -0.095 MPa for 35-45 minutes and discharge to obtain Component A. ② Preparation of component B: Mix 3.5 kg of triethylenediamine, 1.4 kg of dibutyltin dilaurate and 2.8 kg of deionized water evenly to obtain component B; ③ Take 75 kg of component A obtained in step ① and 7.5 kg of component B obtained in step ② and mix them evenly to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics. Example

[0030] The preparation method of the low-modulus two-component silane-modified sealant for silicon carbide ceramics described in Example 2 includes the following steps: ① Preparation of Component A: Add 65 kg of silane-modified polyether resin, 35 kg of polyurea-type thixotropic agent containing plasticizer, and 7 kg of titanium-modified siloxane adhesive to a mixer and stir for 10-15 minutes. Then add 30 kg of heavy calcium carbonate, 20 kg of difunctional polyether polyol, 1.5 kg of antioxidant HP136, 1 kg of ultraviolet absorber UV-1130, 1.5 kg of bis(γ-trimethoxysilylpropyl)amine, and 2.0 kg of dehydrating agent MTMS. Stir under a vacuum of -0.09 to -0.095 MPa for 35-45 minutes and discharge to obtain Component A. ② Preparation of component B: Mix 4 kg of N,N-dimethylbenzylamine, 5 kg of dibutyltin bis(acetylacetonate), and 7 kg of deionized water evenly to obtain component B; ③ Mix 160 kg of component A obtained in step ① and 6.4 kg of component B obtained in step ② evenly to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics. Example

[0031] The preparation method of the low-modulus two-component silane-modified sealant for silicon carbide ceramics described in Example 3 includes the following steps: ① Preparation of Component A: Add 50 kg of silane-modified polyether resin, 20 kg of polyurea-type thixotropic agent containing plasticizer, and 4 kg of titanium-modified siloxane adhesive to a mixer and stir for 10-15 minutes. Then add 15 kg of heavy calcium carbonate, 10 kg of difunctional polyether polyol, 1 kg of antioxidant 425, 0.6 kg of ultraviolet absorber Tinuvin 770DF, 0.6 kg of N-phenyl-γ-aminopropyltrimethoxysilane, and 0.6 kg of silane coupling agent A-172. Stir under a vacuum of -0.09 to -0.095 MPa for 35-45 minutes and discharge to obtain Component A. ② Preparation of component B: Mix 3 kg of 2,4,6-tris(dimethylaminomethyl)phenol, 2 kg of dibutyltin dioctanoate and 3 kg of deionized water evenly to obtain component B; ③ Mix 90 kg of component A obtained in step ① and 6 kg of component B obtained in step ② evenly to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics. Example

[0032] The preparation method of the low-modulus two-component silane-modified sealant for silicon carbide ceramics described in Example 4 includes the following steps: ① Preparation of Component A: 60 kg of silane-modified polyether resin, 25 kg of polyurea-type thixotropic agent containing plasticizer, and 6 kg of titanium-modified siloxane adhesive additive are added to a mixer and stirred for 10-15 minutes. Then, 25 kg of heavy calcium carbonate, 15 kg of difunctional polyether polyol, 1.2 kg of antioxidant 3114, 0.8 kg of ultraviolet absorber UV-1130, 0.8 kg of N-phenyl-γ-aminopropyltrimethoxysilane, and 1.6 kg of methyltris(methylethyl ketone oxime)silane are added. The mixture is stirred under a vacuum of -0.09 to -0.095 MPa for 35-45 minutes, and the resulting material is Component A. ② Preparation of component B: Mix 1.5 kg of triethylenediamine, 2 kg of diethylenetriamine, 2 kg of dibutyltin dilaurate, 1 kg of dibutyltin bis(acetylacetone) and 6 kg of deionized water evenly to obtain component B; ③ Mix 132 kg of component A obtained in step ① and 6 kg of component B obtained in step ② evenly to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics. Example

[0033] The preparation method of the low-modulus two-component silane-modified sealant for silicon carbide ceramics described in Example 5 includes the following steps: ① Preparation of Component A: Add 50 kg of silane-modified polyether resin, 25 kg of polyurea-type thixotropic agent containing plasticizer, and 5 kg of titanium-modified siloxane adhesive to a mixer and stir for 10-15 minutes. Then add 15 kg of heavy calcium carbonate, 15 kg of difunctional polyether polyol, 1.2 kg of antioxidant 425, 0.7 kg of ultraviolet absorber UV-3808PP5, 1.2 kg of γ-ureidopropyltriethoxysilane, and 1.5 kg of silane coupling agent A-172. Stir under a vacuum of -0.09 to -0.095 MPa for 35-45 minutes and discharge to obtain Component A. ② Preparation of component B: Mix 2 kg of N,N-dimethylbenzylamine, 1 kg of 2,4,6-tris(dimethylaminomethyl)phenol, 2 kg of dibutyltin dioctanoate, 1 kg of dibutyltin oxide and 5 kg of deionized water evenly to obtain component B; ③ Mix 110 kg of component A obtained in step ① and 5.5 kg of component B obtained in step ② evenly to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics. Example

[0034] The preparation method of the low-modulus two-component silane-modified sealant for silicon carbide ceramics described in Example 6 includes the following steps: ① Preparation of Component A: Add 55 kg of silane-modified polyether resin, 25 kg of polyurea-type thixotropic agent containing plasticizer, and 5 kg of titanium-modified siloxane adhesive to a mixer and stir for 10-15 minutes. Then add 20 kg of heavy calcium carbonate, 10 kg of difunctional polyether polyol, 1 kg of antioxidant HP136, 0.8 kg of ultraviolet absorber UV-1130, 1 kg of bis(γ-trimethoxysilylpropyl)amine, and 1 kg of dehydrating agent MTMS. Stir under a vacuum of -0.09 to -0.095 MPa for 35-45 minutes and discharge to obtain Component A. ② Preparation of component B: Mix 3 kg of diethylenetriamine, 1.5 kg of dibutyltin bis(acetylacetonate), 1.5 kg of dibutyltin dioctanoate and 5 kg of deionized water evenly to obtain component B; ③ Mix 108 kg of component A obtained in step ① and 6 kg of component B obtained in step ② evenly to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics.

[0035] The performance of the low-modulus two-component silane-modified sealants for silicon carbide ceramics obtained in Examples 7-12 was tested. The surface drying time was tested according to GB / T 13477.5, the Shore A hardness according to GB / T 531.1, the tensile shear strength according to GB / T 7124, the tensile strength according to GB / T 528, the elongation at break according to GB / T 528, and the 100% tensile modulus according to GB / T 528. After curing at 21-25℃ and 45-55%RH (at room temperature) for 168 hours, the data of tensile shear strength, tensile strength, elongation at break, and 100% tensile modulus of the sealant are shown in Table 1.

[0036] Table 1. Performance test results of the low-modulus two-component silane-modified sealants for silicon carbide ceramics obtained in Examples 7-12.

[0037] The sealant that was placed at room temperature for 168 hours was placed at -40℃ for 168 hours, and then the tensile shear strength, tensile strength, elongation at break and 100% tensile modulus of the sealant were measured. The data are shown in Table 2.

[0038] Table 2. Performance test results of the low-modulus two-component silane-modified sealants for silicon carbide ceramics obtained in Examples 7-12 after treatment at -40℃.

[0039] After curing the above sealant at 21~25℃ and 45~55%RH for 168 hours, it was then placed at -40℃ for 168 hours. The tensile shear strength, tensile strength, elongation at break and 100% tensile modulus of the sealant were then measured and the data are shown in Table 2.

[0040] The sealant that was placed at room temperature for 168 hours was placed at 120℃ for 168 hours, and then the tensile shear strength, tensile strength, elongation at break and 100% tensile modulus of the sealant were measured. The data are shown in Table 3.

[0041] Table 3. Performance test results of the low-modulus two-component silane-modified sealants for silicon carbide ceramics obtained in Examples 7-12 after treatment at 120°C.

[0042] As can be seen from the results in Tables 1 to 3, the low-modulus two-component silane-modified sealant for silicon carbide ceramics of this invention exhibits excellent adhesion to silicon carbide substrates and excellent adhesion to silicon carbide sheets at room temperature. This sealant possesses balanced mechanical properties and can achieve wide-temperature curing, meeting the requirements of extreme temperature-changing conditions.

Claims

1. A low-modulus two-component silane-modified sealant for silicon carbide ceramics, characterized in that: It is obtained by mixing component A and component B in a mass ratio of 10~25:1; By weight, component A consists of the following components: 45-65 parts of silane-modified polyether resin, 10-35 parts of polyurea-type thixotropic agent containing plasticizer, 3-7 parts of titanium-modified siloxane adhesive aid, 10-30 parts of heavy calcium carbonate, 5-20 parts of difunctional polyether polyol, 0.8-1.5 parts of antioxidant, 0.5-1 part of ultraviolet absorber, 0.5-1.5 parts of adhesive accelerator, and 0.5-2.0 parts of dehydrating agent; component B consists of the following components: 2.5-4 parts of amine catalyst, 1-5 parts of organotin catalyst, and 2-7 parts of deionized water.

2. The low-modulus two-component silane-modified sealant for silicon carbide ceramics according to claim 1, characterized in that: The titanium-modified siloxane adhesive was prepared according to the following steps: Add silane coupling agent, hydrogen-containing silicone oil and alcohol solvent to the reaction vessel, stir and react for 15-20 minutes under nitrogen protection, add titanate coupling agent, continue stirring for 20-25 minutes, add Karstedt catalyst, stir for 5-10 minutes to disperse it evenly, and obtain a mixture. Add tetrabutyl titanate dropwise to the mixture. After the addition is complete, heat the reactor to 50-60°C and react for 1-2 hours. Add deionized water and stir for 10-15 minutes to terminate the reaction. Cool to 20-30°C and remove the solvent and water by vacuum distillation to obtain titanium-modified siloxane adhesive. The silane coupling agent is vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, or γ-aminopropyltriethoxysilane; The hydrogen-containing silicone oil is tetramethylcyclotetrasiloxane or hexamethyldisiloxane; The alcohol solvent is ethanol or isopropanol; The titanate coupling agent is KR-138S, KR-55 or NDZ-101; The mass ratio of silane coupling agent, hydrogen-containing silicone oil, alcohol solvent, titanate coupling agent, Karstedt catalyst, tetrabutyl titanate and deionized water is 100:30~50:150~200:10~20:0.1~0.3:20~40:5~10.

3. The low-modulus two-component silane-modified sealant for silicon carbide ceramics according to claim 1, characterized in that: The polyurea-type thixotropic agent containing plasticizer is prepared according to the following steps: After vacuum dehydration, the plasticizer is mixed and dispersed with small molecule amine under nitrogen protection. Polyisocyanate is added dropwise at 40~65℃. After the addition is complete, the reaction is kept at 70~90℃ for 2~4 hours. After cooling to 20~30℃, the mixture is filtered to obtain a polyurea-type thixotropic agent containing plasticizer. The plasticizer is one or two of the following: dioctyl adipate, trioctyl trimellitate, dioctyl sebacate, or tributyl citrate. The small molecule amine is ethylenediamine, cyclohexanediamine, 1,6-hexanediamine, diethylenetriamine, or triethylenetetramine; The polyisocyanate is one or two of hexamethylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate or 4-fluorophenyl isocyanate; The mass ratio of plasticizer, small molecule amine and polyisocyanate is 100:5~12:15~25.

4. The low-modulus two-component silane-modified sealant for silicon carbide ceramics according to claim 1, characterized in that: The silane-modified polyether resin is one of Kaneka Corporation's MAX602, Asahi Glass's S2410E, or Nanjing Qingqi's 250S or 410E.

5. The low-modulus two-component silane-modified sealant for silicon carbide ceramics according to claim 1, characterized in that: The antioxidant is antioxidant 3114, antioxidant HP136, or antioxidant 425.

6. The low-modulus two-component silane-modified sealant for silicon carbide ceramics according to claim 1, characterized in that: The ultraviolet absorber is UV-3808PP5, UV-1130, or Tinuvin 770DF.

7. The low-modulus two-component silane-modified sealant for silicon carbide ceramics according to claim 1, characterized in that: The adhesion promoter is γ-ureopropyltriethoxysilane, bis(γ-trimethoxysilylpropyl)amine or N-phenyl-γ-aminopropyltrimethoxysilane.

8. The low-modulus two-component silane-modified sealant for silicon carbide ceramics according to claim 1, characterized in that: The dehydrating agent is methyltris(methylethyl ketone oxime)silane, MTMS, or silane coupling agent A-172.

9. The low-modulus two-component silane-modified sealant for silicon carbide ceramics according to claim 1, characterized in that: The amine catalyst is one or two of triethylenediamine, N,N-dimethylbenzylamine, 2,4,6-tris(dimethylaminomethyl)phenol, or diethylenetriamine; the organotin catalyst is one or two of dibutyltin dilaurate, dibutyltin bis(acetylacetonate), dibutyltin dioctanoate, or dibutyltin oxide.

10. The method for preparing a low-modulus two-component silane-modified sealant for silicon carbide ceramics according to claim 1, characterized in that: Includes the following steps: ① Preparation of Component A: By weight, 45-65 parts of silane-modified polyether resin, 10-35 parts of polyurea-type thixotropic agent containing plasticizer, and 3-7 parts of titanium-modified siloxane adhesive additive are added to a mixer and stirred for 10-15 minutes. Then, 10-30 parts of heavy calcium carbonate, 5-20 parts of difunctional polyether polyol, 0.8-1.5 parts of antioxidant, 0.5-1 part of ultraviolet absorber, 0.5-1.5 parts of adhesion promoter, and 0.5-2.0 parts of dehydrating agent are added. The mixture is stirred for 35-45 minutes under a vacuum of -0.09 to -0.095 MPa, and Component A is obtained by discharging the material. ② Preparation of component B: Mix 2.5-4 parts of amine catalyst, 1-5 parts of organotin catalyst and 2-7 parts of deionized water evenly to obtain component B; ③ Mix component A obtained in step ① and component B obtained in step ② at a mass ratio of 10~25:1 to obtain a low-modulus two-component silane-modified sealant for silicon carbide ceramics.

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