A method for preparing a silicon-boron-carbon-nitrogen precursor with high synthesis yield, low cost and short cycle

Abstract

The present application relates to a kind of silicon boron carbon nitrogen precursor high synthesis yield, low cost, short cycle preparation method, belong to inorganic non-metallic material preparation technical field, the present application is by introducing high reactivity gas, the gas phase reaction of silazane gas and high reactivity gas in the reaction process, realizes the efficient use of silazane, effectively improves precursor synthesis yield, reduces production cost.The input of high reactivity gas can improve the polymerization degree of reaction system, avoid a large number of oligomers in the process of heating gasification removal, play the effect of catalytic polymerization, simultaneously save precursor low step, effectively shorten the precursor synthesis cycle.By the proportion of raw material, reaction process parameter control, realize the process performance of silicon boron carbon nitrogen precursor, element composition and structure control, can be prepared to be suitable for high-temperature coating, ceramic fiber and ceramic matrix composite matrix with different element composition and processing performance resin.

Description

Technical Field

[0001] This invention belongs to the field of inorganic non-metallic material preparation technology, specifically relating to a high-yield, low-cost, and short-cycle preparation method for silicon-boron-carbon-nitrogen precursors. Background Technology

[0002] With the continuous development of the advanced ceramics industry, especially the surge in demand for high-performance ceramic fibers and ceramic matrix composites in fields such as aerospace, the precursor conversion method for preparing carbon fiber reinforced ceramic matrix composites has become the mainstream approach for preparing thermal structural composites. Among these, SiBCN ceramics prepared by the precursor conversion method exhibit significantly improved high-temperature resistance, anti-crystallization, and anti-oxidation properties due to the formation of a BCN layered structure. Therefore, C / SiBCN ceramic matrix composites prepared using SiBCN as the ceramic matrix have broad application prospects in the aerospace field.

[0003] SiBCN precursors are key raw materials for the preparation of C / SiBCN ceramic matrix composites. Their preparation typically involves the co-ammonolysis of chlorosilanes, boron trichloride, and hexamethyldisilazane. Hexamethyldisilazane is used in extremely large quantities, resulting in high production costs. Furthermore, the preparation process generates significant amounts of ammonium salts and small-molecule byproducts, leading to low actual product yields. The post-processing of these ammonium salts and byproducts also poses a significant environmental concern. Therefore, the high price of SiBCN precursors currently limits their widespread application in the aerospace field. CN117069946A uses chlorosilane, boron trichloride and disilazane, and SiBCN ceramic precursor by-products as raw materials. It employs a one-pot method, heating the reaction under an inert atmosphere to prepare SiBCN ceramic precursor (PBSZ), which can recycle and reuse the by-products of SiBCN precursor synthesis to a certain extent. However, it inevitably involves atmospheric pressure and high temperature treatment and decompression polymerization steps, which generate a large amount of small molecule by-products again. The reuse effect is not obvious, and the synthesis cost is high, the cycle is long, and the efficiency is low.

[0004] Therefore, improving the yield of precursor synthesis, reducing the manufacturing cost of SiBCN precursors, and shortening the precursor preparation cycle are urgent problems to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned defects of the prior art and provide a high-yield, low-cost, and short-cycle preparation method for silicon-boron-carbon-nitrogen precursors. By introducing a highly reactive gas, the efficient utilization of silicon-boron-carbon-nitrogen precursors is achieved through the gas-phase reaction between the silicon-boron-carbon-nitrogen gas and the highly reactive gas during the reaction process. This can effectively improve the precursor synthesis yield and reduce production costs.

[0006] The above-mentioned objectives of the present invention are mainly achieved through the following technical solutions: A method for preparing silicon-boron-carbon-nitrogen precursors with high synthesis yield, low cost, and short cycle time is characterized by the following steps: (1) Add reaction raw material A to an organic solvent and stir until homogeneous, then add hexamethyldisilazane dropwise; the reaction raw material A includes at least one of chlorosilane or boron trichloride; (2) Heat and keep warm the solution obtained in step (1) until the organic solvent and small molecule byproducts are completely evaporated; (3) Heat the solution obtained in step (2) and continuously introduce a highly reactive gas into the system; (4) Monitor the viscosity of the solution in step (3) in real time. When the viscosity reaches the preset value, stop the introduction of highly reactive gas to obtain the polymer precursor.

[0007] The reaction raw material A includes chlorosilane and boron trichloride, and the molar ratio of chlorosilane, boron trichloride and hexamethyldisilazane is 0~10:0~10:10~100.

[0008] The chlorosilane has the following structural formula:

[0009] R1, R2, and R3 are Cl, H, methyl, vinyl, allyl, ynyl, or phenyl.

[0010] In step (1), the organic solvent includes at least one of benzene, toluene, xylene, n-hexane, tetrahydrofuran, petroleum ether, or diethylene glycol dimethyl ether.

[0011] In step (1), the reaction system is protected by an inert gas and the temperature of the reaction system is -20~0℃.

[0012] In step (2), the heating temperature is 120-150℃, the heating rate is 0.1~2℃ / min, and the holding time is 0-5h.

[0013] In step (3), the flow rate of the highly reactive gas is 1~10 ml / min, the heating temperature is 180-300℃, and the heating rate is 0.1~2℃ / min.

[0014] The highly reactive gas includes at least one of trichlorosilane or tetrachlorosilane.

[0015] The molar ratio of the reaction raw material A, hexamethyldisilazane, and highly reactive gas is 0~20:10~100:0~10.

[0016] A silicon-boron-carbon-nitrogen precursor was prepared according to the above-described preparation method.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention achieves efficient utilization of silazane by introducing a highly reactive gas to enable gas-phase reaction between silazane gas and the highly reactive gas during the reaction process. This effectively improves the precursor synthesis yield and reduces production costs. The introduction of the highly reactive gas can rapidly increase the degree of polymerization of the reaction system, avoiding the vaporization and removal of a large amount of oligomers during the heating process, thus catalyzing the polymerization. At the same time, it eliminates the precursor removal step, effectively shortening the precursor synthesis cycle. It has the advantages of high synthesis yield and simple synthesis steps.

[0018] (2) In the preferred embodiment of the present invention, the structure, composition and process performance of the final precursor are controlled by controlling the amount of highly reactive chlorosilane gas introduced.

[0019] (3) The precursor of the present invention has a wide range of adjustable elemental composition, and can be used to prepare resins with different elemental compositions and processing properties suitable for use as high-temperature coatings, fiber reinforcements and ceramic matrix composites. Attached Figure Description

[0020] Figure 1 This is a TGA curve of the silicon-boron-carbon-nitrogen precursor of Example 1 of the present invention; Figure 2 The infrared spectrum of the silicon-boron-carbon-nitrogen precursor of Example 1 of the present invention is shown. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments: A high-yield, low-cost, and short-cycle preparation method for silicon (boron) carbon nitrogen precursors includes the following steps: Step 1: Add reaction raw material A to an organic solvent and stir evenly, then slowly add hexamethyldisilazane dropwise to the system. The entire process is protected by an inert gas and the temperature is maintained at -20~0℃.

[0022] Step 2: After the addition is complete, raise the system temperature to 120-150℃ at a rate of 0.1~2℃ / min and keep it at that temperature for 0-5 hours until no more waste liquid evaporates from the system.

[0023] Step 3: Close the system outlet and open the inlet valve. Slowly introduce the highly reactive gas through the inlet valve at a flow rate of 1~10 ml / min. At the same time, heat the system to 180℃-300℃ at a rate of 0.1~2℃ / min. By controlling the heating rate and the mixed gas introduction rate, the low molecular weight silazane and the mixed gas can be fully reacted in the gas phase. After the reaction, a high molecular weight polymer is formed and liquefied and reintroduced into the reaction system.

[0024] Step 4: Monitor the viscosity of the reaction system in real time. Stop the introduction of mixed gas when the viscosity of the system reaches the required level to obtain a polymer precursor with a certain molecular weight.

[0025] The reaction raw material A includes chlorosilane and boron trichloride, and the molar ratio of chlorosilane, boron trichloride and hexamethyldisilazane is (0~10):(0~10):(10~100).

[0026] The chlorosilane has the following structure:

[0027] R1, R2, and R3 can be one or more organic groups such as Cl, H, methyl, vinyl, allyl, alkynyl, and phenyl.

[0028] The organic solvents used are benzene, toluene, xylene, n-hexane, tetrahydrofuran, petroleum ether, or diethylene glycol dimethyl ether.

[0029] The highly reactive gas is one or both of trichlorosilane and tetrachlorosilane.

[0030] The molar ratio of chlorosilane, boron trichloride, hexamethyldisilazane and highly reactive gas introduced into the system is (0~10):(0~10):(10~100):(0~10).

[0031] The novel SiBCN precursor prepared by introducing highly reactive gases has a large adjustable range of process properties and elemental composition, and can be used to prepare resins with different elemental compositions and processing properties suitable for use as high-temperature coatings, ceramic fibers, and ceramic matrix composites.

[0032] Example 1 Step 1: Add 2 mol of dimethyldichlorosilane and 1 mol of boron trichloride to 200 ml of n-hexane and stir until homogeneous. Slowly add 6 mol of hexamethyldisilazane dropwise to the system. The entire process is protected by an inert gas and the temperature is maintained at -10~0℃.

[0033] Step 2: After the addition is complete, slowly raise the system temperature to 140℃ and keep it at that temperature for 2 hours until no more waste liquid evaporates from the system.

[0034] Step 3: Close the system outlet, open the inlet valve, slowly introduce 1 mol of trichlorosilane gas through the inlet valve, and at the same time slowly heat the system to 200℃, keep it at this temperature for 4 hours, and then cool it down to obtain the final product.

[0035] Figure 1 The figure shown is the TGA curve of the silicon-boron-carbon-nitrogen precursor in this embodiment; Figure 2The image shows the infrared spectrum of the silicon-boron-carbon-nitrogen precursor in this embodiment. The product obtained in this embodiment is a viscous liquid. The number-average molecular weight of the product, Mn, was determined to be 1126 by gel permeation chromatography. TGA analysis showed that the ceramic yield of the Si(B)CN precursor at 1000℃ under Ar gas was 63wt%, the room temperature viscosity was 3442cp, and the actual product obtained was 220g, with a synthesis yield of approximately 89%.

[0036] Example 2 Step 1: Add 2 mol of methyldichlorosilane and 1 mol of boron trichloride to 200 ml of tetrahydrofuran and stir well. Slowly add 7 mol of hexamethyldisilazane dropwise to the system. The entire process is protected by an inert gas and the temperature is maintained at -10~0℃.

[0037] Step 2: After the addition is complete, slowly raise the system temperature to 150℃ and keep it at that temperature for 2 hours until no more waste liquid evaporates from the system.

[0038] Step 3: Close the system outlet, open the inlet valve, slowly introduce 1 mol of tetrachlorosilane gas through the inlet valve, and at the same time slowly heat the system to 200℃, keep it at this temperature for 2 hours, and then cool it down to obtain the final product.

[0039] The product obtained was a viscous liquid. TGA analysis showed that the residual weight of the Si(B)CN precursor at 1000℃ under Ar gas was 75wt%, and the viscosity at room temperature was 5500cp. The actual product obtained was 200g, and the synthesis yield was about 81%.

[0040] Example 3 Step 1: Add 2 mol of methylallyldichlorosilane and 1 mol of boron trichloride to 200 ml of tetrahydrofuran and stir until homogeneous. Slowly add 10 mol of hexamethyldisilazane dropwise to the system. The entire process is carried out under inert gas protection and the temperature is maintained between -10 and 0℃. Step 2: After the addition is complete, slowly raise the system temperature to 150℃ and hold for 2 hours until no more waste liquid evaporates. Step 3: Close the system outlet and open the inlet valve. Slowly introduce 1 mol of tetrachlorosilane gas through the inlet valve while simultaneously raising the system temperature to 260℃. Hold for 2 hours and then cool to obtain the final product. The obtained product is a solid with a softening point of 85℃. TGA analysis shows that the residual weight of the Si(B)CN precursor at 1000℃ under Ar gas is 78 wt%. The actual product obtained is 280 g, with a synthesis yield of approximately 85%.

[0041] Comparative Example Step 1: Add 2 mol of methylallyldichlorosilane and 1 mol of boron trichloride to 200 ml of tetrahydrofuran and stir until homogeneous. Slowly add 10 mol of hexamethyldisilazane dropwise to the system. The entire process is carried out under inert gas protection and the temperature is maintained between -10 and 0℃. Step 2: After the addition is complete, slowly raise the system temperature to 200℃ and hold for 2 hours until no more waste liquid evaporates. Step 3: Open the vacuum valve to perform a de-lowering treatment at 200℃. Hold for 1 hour, then cool to obtain the final product.

[0042] The obtained product was a viscous solid with a softening point of 85°C. TGA analysis showed that the residual weight of the Si(B)CN precursor at 1000°C under Ar gas was 78 wt%, and the actual product obtained was 120 g, with a synthesis yield of approximately 36%. The above description is merely the preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this invention should be included within the scope of protection of this invention.

[0043] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for preparing silicon-boron-carbon-nitrogen precursors with high synthesis yield, low cost, and short cycle time, characterized in that: Includes the following steps: (1) Add reaction raw material A to an organic solvent and stir until homogeneous, then add hexamethyldisilazane dropwise; the reaction raw material A includes at least one of chlorosilane or boron trichloride; (2) Heat and keep warm the solution obtained in step (1) until the organic solvent and small molecule byproducts are completely evaporated; (3) Heat the solution obtained in step (2) and continuously introduce a highly reactive gas into the system; (4) Monitor the viscosity of the solution in step (3) in real time. When the viscosity reaches the preset value, stop the introduction of highly reactive gas to obtain the polymer precursor.

2. The method for preparing silicon-boron-carbon-nitrogen precursors with high synthesis yield, low cost, and short cycle time according to claim 1, characterized in that: The reaction raw material A includes chlorosilane and boron trichloride, and the molar ratio of chlorosilane, boron trichloride and hexamethyldisilazane is 0~10:0~10:10~100.

3. The method for preparing silicon-boron-carbon-nitrogen precursors with high synthesis yield, low cost, and short cycle time according to claim 1, characterized in that: The chlorosilane has the following structural formula: R1, R2, and R3 are Cl, H, methyl, vinyl, allyl, ynyl, or phenyl.

4. The method for preparing silicon-boron-carbon-nitrogen precursors with high synthesis yield, low cost, and short cycle time according to claim 1, characterized in that: In step (1), the organic solvent includes at least one of benzene, toluene, xylene, n-hexane, tetrahydrofuran, petroleum ether, or diethylene glycol dimethyl ether.

5. The method for preparing silicon-boron-carbon-nitrogen precursors with high synthesis yield, low cost, and short cycle time according to claim 1, characterized in that: In step (1), the reaction system is protected by an inert gas and the temperature of the reaction system is -20~0℃.

6. The method for preparing silicon-boron-carbon-nitrogen precursors with high synthesis yield, low cost, and short cycle time according to claim 1, characterized in that: In step (2), the heating temperature is 120-150℃, the heating rate is 0.1~2℃ / min, and the holding time is 0-5h.

7. The method for preparing silicon-boron-carbon-nitrogen precursors with high synthesis yield, low cost, and short cycle time according to claim 1, characterized in that: In step (3), the flow rate of the highly reactive gas is 1~10 ml / min, the heating temperature is 180-300℃, and the heating rate is 0.1~2℃ / min.

8. The method for preparing silicon-boron-carbon-nitrogen precursors with high synthesis yield, low cost, and short cycle time according to claim 1, characterized in that: The highly reactive gas includes at least one of trichlorosilane or tetrachlorosilane.

9. The method for preparing silicon-boron-carbon-nitrogen precursors with high synthesis yield, low cost, and short cycle time according to claim 1, characterized in that: The molar ratio of the reaction raw material A, hexamethyldisilazane, and highly reactive gas is 0~20:10~100:0~10.

10. A silicon-boron-carbon-nitrogen precursor, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 9.

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