A method for preparing solid polycarbosilane containing active functional groups

Abstract

The application discloses a method for preparing solid polycarbosilane containing active functional groups, and the product is solid polycarbosilane containing C=C. The method comprises the following steps: under the protection of inert gas, a toluene is used as a solvent, and a metallocene and a vinyl magnesium chloride are reacted to generate a metallocene containing active groups; and the metallocene containing active groups, chlorosilane and alkali metal are subjected to a polymerization reaction at high temperature to generate solid polycarbosilane containing active groups. The method has the advantages of low reaction temperature, high safety factor, and wide application prospect. The content of the introduced active groups and the content of metal elements can be effectively controlled by changing the feeding ratio.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic materials, and particularly discloses a method for preparing solid polycarbosilane containing active functional groups. BACKGROUND

[0002] Silicon carbide (SiC) ceramic materials have been widely concerned due to their excellent heat shock resistance, chemical corrosion resistance, high-temperature oxidation resistance, high modulus, low density, small thermal expansion rate and other excellent properties compared with other ceramic matrix composites (Si3N4, Al2O3). The preparation processes of SiC ceramic materials mainly include hot-pressing sintering, impregnation pyrolysis, reaction infiltration, chemical vapor infiltration, combined process CVI-PIP, CVI-RMI, etc. The impregnation pyrolysis method has the advantages of relatively mild reaction conditions and simple process flow, and has become the mainstream method for preparing SiC ceramic materials.

[0003] The biggest advantage of the impregnation pyrolysis method for synthesizing SiC ceramic materials is that changing the composition and structure of the precursor can change the composition and yield of the SiC ceramic product. Therefore, the synthesis of polycarbosilane precursor is the key to producing high-quality and high-yield SiC ceramics. Polycarbosilane mainly includes liquid hyperbranched polycarbosilane and solid Yajima polycarbosilane. There are more related reports on modifying liquid polycarbosilane by grafting different active groups to obtain products with different properties. For example, the Chinese patent document with the authorization announcement number CN114573821 obtains liquid polycarbosilane containing carbon-carbon double bonds by using chloromethyltrichlorosilane and chloromethyl(methyl)dichlorosilane, magnesium as raw materials, and tetrahydrofuran and aromatic hydrocarbon as mixed solvents through Grignard coupling reaction and reduction reaction. In addition, the paper by Tian Hua Huang et al. (Chinese Chemical Letters, 2007, 18(6), 754-757) synthesized hyperbranched liquid polycarbosilane containing vinyl groups by using chloromethyltrichlorosilane, chloromethyl(methyl)dichlorosilane and allyl chloride in a one-pot method.

[0004] In the actual production process, solid polycarbosilane has the advantages of low branching, good spinnability, and mature technology, and occupies an important position in production. However, the modification research related to solid polycarbosilane is very limited and mainly focuses on the introduction of heterogeneous elements (Zr, Hf, Ti, B, etc.). For example, Wang Hao et al. (CN102153760B) disclosed a method for preparing a BC polymer ceramic precursor containing an organic metal M (M is Zr, Hf, Ti), in which zirconium dichloride (hafnium, titanium) is reacted with vinyl magnesium chloride or allyl magnesium chloride to generate an organic zirconium (hafnium, titanium) monomer containing a double bond, which is then reacted with borane or borazane to generate an organic metal M (M is Zr, Hf, Ti)-BC polymer ceramic precursor. Wang Xiaozhou et al. (CN109054026B) disclosed a method for preparing an HfC-SiC ultra-high temperature ceramic precursor. First, hafnium dichloride, dihaloolefin, and magnesium are sequentially subjected to Grignard coupling reaction and condensation reaction. Then, trialkylchloroalkylsilane is added for end-capping reaction to obtain an intermediate product. Finally, the intermediate product is dissolved with polycarbosilane to undergo a hydrosilylation reaction to generate the HfC-SiC ultra-high temperature ceramic precursor. Therefore, it is very necessary to synthesize a solid polycarbosilane containing active functional groups. Summary of the Invention

[0005] The purpose of the present invention is to design a new method for preparing solid polycarbosilane containing active functional groups, so as to increase research on related modifications of solid polycarbosilane and promote the application of solid polycarbosilane containing active functional groups.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A new method for preparing solid polycarbosilane containing active functional groups comprises the following steps:

[0008] 1) In an inert atmosphere, using xylene as the solvent, zirconocene dichloride and vinyl magnesium chloride are reacted at low temperature for 2 to 10 hours, and then kept at room temperature for 5 to 24 hours;

[0009] 2) filtering and extracting the solid-liquid mixture synthesized in step 1), and vacuum drying the obtained solid product for 12 to 36 hours;

[0010] 3) In an inert atmosphere, sodium metal was added to toluene as a solvent to prepare sodium sand, and then the solid product obtained in step 2) and dimethyldichlorosilane were added and the mixture was kept warm for 5-15 hours. After the reaction was completed, the reaction was terminated by ventilation.

[0011] 4) In an inert atmosphere, the solid-liquid mixture obtained in step 3) is filtered, rotary evaporated and pretreated at high temperature to obtain a solid polyzirconium carbosilane containing a C=C active functional group.

[0012] Preferably, the molar ratio of the dichlorobis-cyclopentadienyl zirconium and the vinyl magnesium chloride in step 1) is 0.1-2; the temperature of the low-temperature reaction is -30-10℃.

[0013] Preferably, the extractant in step 2) is selected from one or more of N,N-N-n-octylamine dimethylene phenyl phosphonic acid, naphthenic acid, 2-ethylhexyl phosphonic acid 2-ethylhexyl ester, di(2,4,4-trimethylpentyl) phosphinic acid, 2-ethylhexyl phosphonic acid mono(2-ethylhexyl) ester and a mixture of one or more of methyl isobutyl ketone, cyclohexanone, isoamyl alcohol, sec-octanol, petroleum ether;

[0014] The vacuum drying temperature is 50-150℃.

[0015] Preferably, the molar ratio of the solid product obtained in step 2) and dimethyl dichlorosilane in step 3) is 1 / 20-1 / 2; the amount of sodium added is 1.1-2 times the molar amount; sodium sand is prepared by high-temperature stirring; the reaction temperature is 50-110℃; the type of gas selected is one or more of nitrogen, hydrogen, argon, ammonia and helium.

[0016] Preferably, the rotary evaporation temperature in step 4) is 50-180℃; the high-temperature pretreatment temperature is 150-350℃.

[0017] The present application has the following beneficial effects:

[0018] The reaction and post-treatment process of the present application are both in an inert gas atmosphere, and the oxygen content in the product is low; the carbon-carbon double bond active group is introduced by the reaction of dichlorobis-cyclopentadienyl zirconium and vinyl magnesium chloride, and theoretically the molar ratio of the two can control the content of the introduced vinyl group; the molar ratio of the dichlorobis-cyclopentadienyl zirconium containing vinyl group and dimethyl dichlorosilane can control the zirconium content in the product; the solid-state poly-zirconium carbosilane containing C=C is synthesized, which has broad application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The infrared spectrum of the solid-state poly-zirconium carbosilane containing active functional groups prepared in Example 3. DETAILED DESCRIPTION

[0020] The present application will be further described below in conjunction with specific examples. Other examples obtained by those skilled in the art on the basis of the examples of the present application without making creative efforts are all within the scope of protection of the present application.

[0021] Example 1

[0022] 1) Under high purity nitrogen protection, add 250 mL of xylene, 17.54 g (0.06 mol) of Cl2Cp2Zr and 18.75 mL (0.03 mol) of ClMgCH=CH2 into a three-neck flask in sequence. Keep the reaction at -20°C for 4 h at a rotation speed of 500 rpm, and then keep it at 20°C overnight. Filter the reaction solution, and extract the filtrate with N,N-N-n-octylamine dimethylene phenyl phosphonic acid and sec-octyl alcohol. Filter the extract to obtain a yellowish solid product, which is dried under vacuum overnight to remove water, and obtain 5.79 g of vinyl bicyclopentadienyl zirconium chloride.

[0023] 2) Under high purity nitrogen protection, add 150 mL of toluene into a four-neck flask, and heat it to 105°C, then add 6.36 g of small sodium pieces, and keep it at rest for 0.5 h, then quickly stir to obtain silver-white sodium sand. Reduce the temperature to 90°C, and then add 5.9 g of dried vinyl cyclopentadienyl zirconium dichloride obtained in step 1) and 10 mL of Me2Cl2Si in sequence. The solution gradually turns wine red after 20 min of reaction, and the reaction is stirred for 10 h, then terminated by passing NH3 for half an hour. After the solution is cooled, filter the solution, and evaporate the solvent toluene at 150°C for 1 h to perform preliminary cross-linking and solidification, and obtain 4.96 g of polyzirconium carbosilane under liquid nitrogen cooling, with a yield of about 45.55%. Put 3.72 g of the solid product into a tube furnace, and heat it at 260°C for 2 h under argon atmosphere to obtain 3.09 g, with a yield of about 83%. The synthesized solid product is proved to contain vinyl by infrared characterization.

[0024] Example 2

[0025] 1) Under high purity nitrogen protection, add 250 mL of xylene, 17.54 g (0.06 mol) of Cl2Cp2Zr and 18.75 mL (0.03 mol) of ClMgCH=CH2 into a three-neck flask in sequence. Keep the reaction at -20°C for 4 h at a rotation speed of 500 rpm, and then keep it at 20°C overnight. Filter the reaction solution, and extract the filtrate with N,N-N-n-octylamine dimethylene phenyl phosphonic acid and sec-octyl alcohol. Filter the extract to obtain a yellowish solid product, which is dried under vacuum overnight to remove water, and obtain 5.79 g of vinyl bicyclopentadienyl zirconium chloride.

[0026] 2) Under high purity nitrogen protection, add 150 mL of toluene to a four-necked flask, and then add 6.39 g of small sodium pieces after heating to 105°C. After standing for 0.5 h, fast stirring is performed to obtain silver-white sodium sand. The temperature is reduced to 90°C, and then 5.7 g of the dry solid product obtained in step 1) and 10 mL of Me2Cl2Si are sequentially added. After 20 min of reaction, the solution gradually turns wine red. After 10 h of stirring reaction, the reaction is terminated by passing NH3 for half an hour. After the solution is cooled, the solution is suction filtered, and the filtrate is rotary evaporated at 150°C for 1 h to remove the solvent toluene and to perform preliminary cross-linking solidification. After liquid nitrogen cooling, 4.1 g of polyzirconium carbosilane is obtained, with a yield of about 37.65%. 3.25 g of the solid product is placed into a tube furnace, and is baked at 260°C for 2 h under an argon atmosphere to obtain 2.50 g, with a yield of about 76.9%. Infrared characterization proves that the synthesized solid product contains vinyl groups.

[0027] Example 3

[0028] 1) Under high purity nitrogen protection, 250 mL of xylene, 35 g (0.12 mol) of Cl2Cp2Zr, and 37.5 mL (0.06 mol) of ClMgCH=CH2 are sequentially added to a three-necked flask. After standing at a rotation speed of 500 rpm and at -20°C for 4 h, and then at room temperature (20°C) overnight, the reaction solution is suction filtered, and then bis(2,4,4-trimethylpentyl) phosphinic acid and isoamyl alcohol are added to the filtrate for extraction. The extracted solution is suction filtered to obtain a light yellow solid product, which is vacuum dried overnight to remove water to obtain 11.14 g of vinyl biscyclopentadienyl zirconium chloride.

[0029] 2) Under high purity nitrogen protection, 150 mL of toluene is added to a four-necked flask, and then 6.39 g of small sodium pieces is added after heating to 105°C. After standing for 0.5 h, fast stirring is performed to obtain silver-white sodium sand. The temperature is reduced to 90°C, and then 9.46 g of the dry vinyl cyclopentadienyl zirconium dichloride obtained in step 1) and 10 mL of Me2Cl2Si are sequentially added. After 20 min of reaction, the solution gradually turns wine red. After 10 h of stirring reaction, the reaction is terminated by passing NH3 for half an hour. After the solution is cooled, the solution is suction filtered, and the filtrate is rotary evaporated at 150°C for 1 h to remove the solvent toluene and to perform preliminary cross-linking solidification. After liquid nitrogen cooling, 6.61 g of polyzirconium carbosilane is obtained, with a yield of about 50.08%. 4.96 g of the solid product is placed into a tube furnace, and is baked at 260°C for 2 h under an argon atmosphere to obtain 4.19 g, with a yield of about 84.47%. Infrared characterization proves that the synthesized solid product contains vinyl groups (as shown in FIG. 2). Figure 1

[0030] Example 4

[0031] ​In order to verify the effect of the extractant on the yield of the polyzirconocarbosilane, a comparative experiment was conducted, the operation conditions were the same as those in Example 1, only the extractant was replaced by n-hexane, and the following was the experimental procedure:

[0032] 1) Under the protection of high-purity nitrogen, 250 mL of dimethylbenzene, 17.54 g (0.06 mol) of Cl2Cp2Zr and 18.75 mL (0.03 mol) of ClMgCH=CH2 were sequentially added to a three-necked flask. The reaction was incubated at -20°C for 4 h at a rotation speed of 500 rpm, and then incubated at 20°C overnight. The reaction solution was suction filtered, and the filtrate was added to n-hexane for extraction. The extracted solution was suction filtered to obtain a light yellow solid product, which was vacuum dried overnight to remove moisture, and 3.55 g of vinyl biscyclopentadienyl zirconium chloride was obtained.

[0033] 2) Under the protection of high-purity nitrogen, 75 mL of toluene was added to a four-necked flask, and the temperature was increased to 105°C, then 3.21 g of small sodium pieces were added, and the reaction was incubated for 0.5 h, then the silver-white sodium sand was obtained by rapid stirring. The temperature was reduced to 90°C, and 3.0 g of the dried vinyl cyclopentadienyl zirconium dichloride obtained in step 1) and 5 mL of Me2Cl2Si were sequentially added, and the solution gradually turned wine red after 20 min of reaction, and the stirring reaction was terminated after 10 h of reaction by passing NH3 for half an hour. After the solution was cooled, the solution was suction filtered, and the filtrate was rotary evaporated at 150°C for 1 h to remove the solvent toluene and to perform preliminary cross-linking and solidification, and 1.11 g of polyzirconocarbosilane was obtained by liquid nitrogen cooling, and the yield was about 18.55%. The entire product was placed in a tube furnace and sintered at 260°C for 2 h under an argon atmosphere to obtain 0.41 g, and the yield was about 36.9 %. The synthesized solid product was proved to contain vinyl groups by infrared characterization, but the product yield and ceramic yield were significantly reduced compared to before.

[0034] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method for preparing a solid polycarbosilane containing active functional groups, characterized in that The following steps are involved: 1) In an inert atmosphere, using toluene as a solvent, a metallocene and vinyl magnesium chloride are reacted at low temperature for 2 to 10 hours, and then kept at room temperature for 5 to 24 hours. The metallocene is zirconocene dichloride, hafnocene dichloride, titanocene dichloride, or ferrocene dichloride, and the molar ratio of the metallocene to vinyl magnesium chloride is 1 to 2. 2) filtering, extracting, and purifying the solid-liquid mixture synthesized in step 1), and drying the resulting solid product for 12 to 36 hours; 3) In an inert atmosphere, add an alkali metal to the solvent, then add the solid product obtained in step 2) and dimethyldichlorosilane, and react for 5 to 15 hours. Then, ventilate to terminate the reaction. 4) In an inert atmosphere, the solid-liquid mixture obtained in step 3) is filtered and rotary evaporated to obtain a solid polymetallic carbosilane containing a C=C active functional group.

2. The method for preparing a solid polycarbosilane containing active functional groups according to claim 1, characterized in that: The low-temperature reaction temperature in step 1) is -30 to 10°C.

3. The method for preparing a solid polycarbosilane containing active functional groups according to claim 1, characterized in that: The extractant used in the extraction in step 2) is selected from a mixture of one or more of N,NN-n-octylaminodimethylphenylphosphonic acid, cycloalkanoic acid, 2-ethylhexyl phosphate, di(2,4,4-trimethylpentyl) hypophosphorous acid, 2-ethylhexylphosphonic acid mono(2-ethylhexyl) ester and one or more of methyl isobutyl ketone, cyclohexanone, isoamyl alcohol, sec-octanol, and petroleum ether.

4. The method for preparing a solid polycarbosilane containing active functional groups according to claim 1, characterized in that: Step 2) is vacuum drying, and the vacuum drying temperature is 50 to 150°C.

5. The method for preparing a solid polycarbosilane containing active functional groups according to claim 1, characterized in that: In step 3), the molar ratio of the solid product obtained in step 2) to dimethyldichlorosilane is 1 / 20 to 1 / 2.

6. The method for preparing a solid polycarbosilane containing active functional groups according to claim 1, characterized in that: The alkali metal added in step 3) is potassium, sodium, or lithium, and the molar amount of the added alkali metal is 1.1 to 2 times.

7. The method for preparing a solid polycarbosilane containing active functional groups according to claim 1, characterized in that: The reaction temperature in step 3) is 50-110°C.

8. The method for preparing a solid polycarbosilane containing active functional groups according to claim 1, characterized in that: The type of ventilation in step 3) is ammonia.

9. The method for preparing a solid polycarbosilane containing active functional groups according to claim 1, wherein: In step 4), the rotary evaporation temperature is 50 to 180°C.

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