A boron-doped low end group chlorinated polymethylsilane and a method for preparing the same

Abstract

This invention discloses a boron-doped polymethylsilane with low-terminal chloride and its preparation method. The preparation method includes preparing a sodium sand mixture; mixing dichloromethylsilane, dichloromethylboron, tetrahydrofuran, and 15-crown ether-5 and then adding the mixture dropwise to the sodium sand mixture for reaction, followed by end-capping reaction. The sodium sand in this preparation method has the characteristics of uniform particle size, high activity, and clean surface. The addition of tetrahydrofuran and 15-crown ether-5 can improve the electron transfer rate, reduce the reaction activation energy, and improve the reaction efficiency. The introduction of dichloromethylboron and end-capping agent can avoid the formation of terminal chloride and introduce highly active Si-H bonds into the molecular chain. The resulting polymethylsilane has a low chloride content, high thermal crosslinking efficiency, and a narrow molecular weight distribution.

Description

Technical Field

[0001] This invention relates to the field of polymethylsilane technology, specifically to a boron-doped polymethylsilane with a low-terminal chloride group and its preparation method. Background Technology

[0002] Polymethylsilanes are key intermediates in the preparation of important precursors such as SiC ceramic fibers and silicon-carbon-nitrogen ceramics. Their synthesis mainly relies on the sodium condensation method, specifically the dechlorination polycondensation reaction between metallic sodium and chloromethylsilane in an inert solvent (such as xylene or tetrahydrofuran). The core step of this reaction is the attack of sodium on the Si-Cl bond, and the reaction rate and conversion are highly dependent on the specific surface area and fresh active surface of metallic sodium. Therefore, improving the activity of metallic sodium plays a crucial role in the subsequent synthesis of polymethylsilanes.

[0003] The traditional method involves mechanically cutting / crushing sodium blocks into thin slices or fragments in an inert glove box. This is the most primitive method, resulting in sodium fragments with limited surface area, easily re-adhesive edges, and rapid oxidation and subsequent NaCl coating of the active surface. It is extremely inefficient and highly dangerous.

[0004] Among the commonly used polycarbosilane-based SiC precursors, polycarbosilane (PCS), with Si-CH2 as the main chain and CH3 and H as side chains, is the most mature commercial SiC precursor, widely used in the preparation of SiC ceramics, SiC fibers, and matrix-modified C / C composites. PCS is a stable solid at room temperature, exhibits good solubility in common nonpolar solvents, has high ceramic yield, and a wide range of applications. However, due to the carbon-to-Si ratio in its molecular structure being greater than 2, PCS pyrolysis products show a significant carbon surplus. Furthermore, PCS is costly due to its complex preparation steps and stringent synthesis conditions. Additionally, the relatively low number of highly reactive Si-H groups and poor thermal crosslinking ability in its molecular structure lead to significant volume expansion in the PCS pyrolysis products, ultimately resulting in numerous residual pores within the ceramic. In 1991, Laine and Richard M discovered that polymethylsilane (PMS), with Si-Si as the main chain and CH3 and H as side chains, is a promising SiC precursor. It can be obtained in one step via the Wurtz dechlorination reaction. Its preparation process is simple and inexpensive, and it has great potential in the field of preparing SiC ceramic matrix composites.

[0005] However, because the Wurtz process uses dichloromethylhydrosilane as the monomer, the uncapped long-chain PMS has Si-Cl end groups. Si-Cl bonds are more reactive than Si-H bonds due to the greater difference in electronegativity between the bonding atoms, leading to PMS's hygroscopic and hydrolytic properties in air. The presence of numerous terminal chlorine segments in the reaction system also results in a wide molecular weight distribution in the PMS product. Therefore, our aim is to reduce the chlorine content of the polymer to obtain a PMS product with high thermal crosslinking efficiency and a narrower molecular weight distribution.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The present invention aims to provide a boron-doped polymethylsilane with low-terminal chloride, its preparation method, and its application. The preparation method involves high-temperature dispersion of metallic sodium in a specific organic solvent system, followed by rapid cooling to obtain sodium sand products with uniform particle size, high activity, clean surface, and suitability for polymethylsilane synthesis. Furthermore, by adding tetrahydrofuran and 15-crown ether-5 to dichloromethylsilane and dichloromethylboron, the single-electron transfer rate from metallic sodium to dichloromethylsilane can be increased, the activation energy of the reaction can be reduced, and the reaction efficiency can be improved. The introduction of dichloromethylboron and a capping agent can prevent the formation of terminal chloride, thus preventing the polymethylsilane from easily hygroscopically hydrolyzing due to Si-Cl bonds, while simultaneously introducing highly active Si-H bonds into the molecular chain. The resulting polymethylsilane has a low chlorine content, high thermal crosslinking efficiency, and a narrow molecular weight distribution.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] The first aspect of this invention provides a method for preparing boron-doped low-terminal chloride-based polymethylsilanes, the method comprising the following steps:

[0010] (a) Under an inert gas atmosphere, metallic sodium is cut and crushed to obtain metallic sodium fragments;

[0011] (b) Under stirring conditions, sodium metal fragments are added to an organic solvent and heated until the sodium metal is molten to obtain a mixture; the organic solvent is a mixture of xylene and cyclohexane;

[0012] (c) Stir the mixture at a stirring speed of 400~600 rpm for a period of time, and then cool the mixture at a stirring speed of 800~1000 rpm and a cooling rate of 15~25℃ / min to obtain a sodium sand mixture.

[0013] (d) Dichloromethylsilane, dichloromethylboron, tetrahydrofuran and 15-crown ether-5 are mixed and then added dropwise to a sodium sand mixture to carry out a Wurtz coupled polymerization reaction. After the reaction is completed, a capping agent is added to carry out a capping reaction. The reaction solution is then cooled, separated into solid and liquid, and distilled to obtain the boron-doped low-terminal chloride polymethylsilane.

[0014] Preferably, in step (b), the solid-liquid ratio of the sodium metal fragments and the organic solvent is 1:(10~15).

[0015] Preferably, in step (b), the stirring speed is 100~250 rpm; the volume ratio of xylene to cyclohexane is (8~10):1; and the temperature is heated to 99~110℃.

[0016] Preferably, in step (c), the stirring time is 30-60 minutes; and the temperature is lowered to below 70°C.

[0017] Preferably, in step (a), the sodium metal fragments are cubes with a side length of 3-5 cm.

[0018] Preferably, in step (c), the cooling method is solvent quenching and jacketed cold bath.

[0019] Preferably, in step (d), the volume ratio of dichloromethylsilane, dichloromethylborane, tetrahydrofuran and 15-crown ether-5 is 1:(0.05~0.1):(0.8~1.2):(0.02~0.3); the molar ratio of the sum of the moles of dichloromethylsilane and dichloromethylborane to the molar ratio of sodium sand is 1:(2~2.2).

[0020] Preferably, in step (d), the dropping conditions are: temperature 60~80℃, dropping rate 0.5~1L / h, and stirring speed 200~600rpm;

[0021] The Wurtz coupled polymerization reaction conditions are: temperature 90~110℃, stirring speed 400~1000rpm, reaction time 10~15h, and nitrogen flow rate 0.5~1L / min.

[0022] Preferably, in step (d), the capping agent is selected from at least one of trimethylchlorosilane, trimethylethoxysilane, trimethylsilanol, dimethylhydrosilyltrimethylsilane, and methyldihydrosilyltrimethylsilane;

[0023] The molar ratio of the capping agent to dichloromethylsilane is (0.0025~0.0125):1;

[0024] The end-capping reaction conditions are as follows: temperature 65~80℃, stirring speed 400~1000rpm, reaction time 1~2h, and nitrogen flow rate 0.5~1L / min.

[0025] A second aspect of the present invention provides a boron-doped polymethylsilane with low-terminal chloride groups prepared by the above-described preparation method.

[0026] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0027] This invention obtains sodium sand with uniform particle size, high activity, and clean surface, suitable for the synthesis of polymethylsilane, by dispersing metallic sodium at high temperature in a specific organic solvent system followed by rapid cooling. This process results in a more stable reaction and higher conversion efficiency during subsequent polymethylsilane synthesis, improving the yield and quality of the final product. Furthermore, the sodium sand preparation method of this invention is simple, allowing for one-step production in a reaction vessel, eliminating the need for complex molten sodium tanks, closed pipelines, and specialized mechanical grinding equipment. This simplifies the process and reduces equipment investment, maintenance difficulty, and failure rate, while also lowering experimental risks. Additionally, this invention does not introduce foreign substances, ensuring the chemical purity of the sodium sand from the source. This not only directly improves the quality of the synthesized polymethylsilane but also eliminates the complex process of separating impurities and waste, reducing environmental pressure and treatment costs.

[0028] The preparation method of this invention improves the single-electron transfer rate of sodium metal to dichloromethylsilane by adding tetrahydrofuran and 15-crown ether-5 to dichloromethylsilane and dichloromethylborane, thereby reducing the activation energy and improving the reaction efficiency. Furthermore, the introduction of dichloromethylborane and end-capping agents avoids the formation of terminal chlorine groups, preventing the polymethylsilane from being easily hygroscopic and hydrolyzed due to Si-Cl bonds, while simultaneously introducing highly active Si-H bonds into the molecular chain. The resulting polymethylsilane has a low chlorine content, high thermal crosslinking efficiency, and a narrow molecular weight distribution. Attached Figure Description

[0029] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0030] Figure 1 This is a photograph of the sodium sand prepared for the synthesis of polymethylsilane in Example 3 of the present invention.

[0031] Figure 2 This is a photograph of the sodium sand prepared for the synthesis of polymethylsilanes in Comparative Example 1 of this invention.

[0032] Figure 3 This is a photograph of the sodium sand prepared for the synthesis of polymethylsilanes in Comparative Example 2 of this invention.

[0033] Figure 4 This is a photograph of the sodium sand prepared for the synthesis of polymethylsilanes in Comparative Example 3 of this invention.

[0034] Figure 5 This is a photograph of the sodium sand prepared for the synthesis of polymethylsilanes in Comparative Example 4 of this invention.

[0035] Figure 6 The infrared spectrum of the polymethylsilane prepared in Example 3 of this invention is shown. Detailed Implementation

[0036] The embodiments of the technical solution of the present invention will be described in detail below with reference to the examples. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore only examples, and should not be used to limit the scope of protection of the present invention.

[0037] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0038] This invention provides a method for preparing boron-doped low-terminal chloride-based polymethylsilanes, the method comprising the following steps:

[0039] (a) Under an inert gas atmosphere, metallic sodium is cut and crushed to obtain metallic sodium fragments;

[0040] (b) Under stirring conditions, sodium metal fragments are added to an organic solvent and heated until the sodium metal is molten to obtain a mixture; the organic solvent is a mixture of xylene and cyclohexane;

[0041] (c) Stir the mixture at a stirring speed of 400~600 rpm for a period of time, and then cool the mixture at a stirring speed of 800~1000 rpm and a cooling rate of 15~25℃ / min to obtain a sodium sand mixture.

[0042] (d) Dichloromethylsilane, dichloromethylboron, tetrahydrofuran and 15-crown ether-5 are mixed and then added dropwise to a sodium sand mixture to carry out a Wurtz coupled polymerization reaction. After the reaction is completed, a capping agent is added to carry out a capping reaction. The reaction solution is then cooled, separated into solid and liquid, and distilled to obtain the boron-doped low-terminal chloride polymethylsilane.

[0043] In one embodiment, in step (b), the solid-liquid ratio of the sodium metal fragments and the organic solvent is 1:(10~15).

[0044] In one embodiment, in step (b), the stirring speed is 100~250 rpm; the volume ratio of xylene to cyclohexane is (8~10):1.

[0045] In one embodiment, in step (b), the temperature is raised to 99-110°C.

[0046] In one embodiment, in step (c), the stirring time is 30-60 minutes.

[0047] In one embodiment, in step (c), the temperature is lowered to below 70°C.

[0048] In one embodiment, in step (a), the sodium metal fragments are cubes with a side length of 3 to 5 cm.

[0049] In one embodiment, in step (c), the cooling method is solvent quenching and jacketed cold bath.

[0050] In one embodiment, in step (d), the volume ratio of dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 is 1:(0.05~0.1):(0.8~1.2):(0.02~0.3); the molar ratio of the sum of the moles of dichloromethylsilane and dichloromethylborane to that of sodium sand is 1:(2~2.2).

[0051] In one embodiment, in step (d), the dropping conditions are: temperature 60~80℃, dropping rate 0.5~1L / h, and stirring speed 200~600rpm;

[0052] The Wurtz coupled polymerization reaction conditions are: temperature 90~110℃, stirring speed 400~1000rpm, reaction time 10~15h, and nitrogen flow rate 0.5~1L / min.

[0053] In one embodiment, in step (d), the capping agent is selected from at least one of trimethylchlorosilane, trimethylethoxysilane, trimethylsilanol, dimethylhydrosilyltrimethylsilane, and methyldihydrosilyltrimethylsilane;

[0054] The molar ratio of the capping agent to dichloromethylsilane is (0.0025~0.0125):1;

[0055] The end-capping reaction conditions are as follows: temperature 65~80℃, stirring speed 400~1000rpm, reaction time 1~2h, and nitrogen flow rate 0.5~1L / min.

[0056] Another embodiment of the present invention provides a boron-doped polymethylsilane with low-terminal chloride obtained by the above preparation method.

[0057] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0058] Example 1

[0059] This embodiment describes a method for preparing boron-doped low-terminal chloride-based polymethylsilanes, the preparation method comprising the following steps:

[0060] (a) Under an inert gas atmosphere, metallic sodium is cut and crushed to obtain square fragments of metallic sodium with a side length of 3~5cm;

[0061] (b) With a solid-liquid ratio of sodium metal fragments to organic solvent of 1:10, sodium metal fragments are added to organic solvent under stirring at 100 rpm and heated to 99°C and kept at that temperature until the sodium metal is in a molten state to obtain a mixture; the organic solvent is a mixture of xylene and cyclohexane in a volume ratio of 10:1.

[0062] (c) Stir the mixture at 400 rpm for 60 min, and then cool the mixture to below 70°C at a cooling rate of 15°C / min while stirring at 800 rpm (cooling method is solvent quenching and jacketed cold bath, solvent is the same as the organic solvent in step (b)) to obtain sodium sand mixture.

[0063] (d) Dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 were mixed and added dropwise to a sodium sand mixture for Wurtz coupled polymerization. After the reaction was completed, a capping agent was added for capping. The reaction solution was then cooled, separated from the solid, and distilled to obtain the polymethylsilane. The volume ratio of dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 was 1:0.1:0.8:0.02; the molar ratio of the sum of the molar numbers of dichloromethylsilane and dichloromethylborane to that of sodium sand was 1:2; the dropping conditions were: temperature 60°C, dropping rate 1 L / h, and stirring speed 600 rpm; the Wurtz coupled polymerization conditions were: temperature 90°C. The stirring rate was 1000 rpm, the reaction time was 15 h, and the nitrogen flow rate was 0.5 L / min. The end-capping agent was trimethylethoxysilane. The molar ratio of the end-capping agent to dichloromethylsilane was 0.0025:1. The end-capping reaction conditions were as follows: temperature was 65℃, stirring rate was 1000 rpm, reaction time was 2 h, and nitrogen flow rate was 0.5 L / min.

[0064] Example 2

[0065] This embodiment describes a method for preparing boron-doped low-terminal chloride-based polymethylsilanes, the preparation method comprising the following steps:

[0066] (a) Under an inert gas atmosphere, metallic sodium is cut and crushed to obtain square fragments of metallic sodium with a side length of 3~5cm;

[0067] (b) With a solid-liquid ratio of sodium metal fragments to organic solvent of 1:15, sodium metal fragments are added to organic solvent under stirring at 250 rpm and heated to 110°C and kept at that temperature until the sodium metal is in a molten state to obtain a mixture; the organic solvent is a mixture of xylene and cyclohexane in a volume ratio of 8:1.

[0068] (c) Stir the mixture at 600 rpm for 30 min, and then cool the mixture to below 70°C at a cooling rate of 25°C / min while stirring at 1000 rpm (cooling method is solvent quenching and jacketed cold bath, solvent is the same as the organic solvent in step (b)) to obtain sodium sand mixture.

[0069] (d) Dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 were mixed and added dropwise to a sodium sand mixture for Wurtz coupled polymerization. After the reaction was completed, a capping agent was added for capping. The reaction solution was then cooled, separated from the solid, and distilled to obtain the polymethylsilane. The volume ratio of dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 was 1:0.05:1.2:0.3; the molar ratio of the sum of the molar numbers of dichloromethylsilane and dichloromethylborane to that of sodium sand was 1:2.2; the dropping conditions were: temperature 80℃, dropping rate 0.5 L / h, and stirring speed 200 rpm; the Wurtz coupled polymerization conditions were: temperature 110℃. The stirring rate was 400 rpm, the reaction time was 10 h, and the nitrogen flow rate was 1 L / min. The end-capping agent was trimethylethoxysilane. The molar ratio of the end-capping agent to dichloromethylsilane was 0.0125:1. The end-capping reaction conditions were as follows: temperature was 80℃, stirring rate was 400 rpm, reaction time was 1 h, and nitrogen flow rate was 1 L / min.

[0070] Example 3

[0071] This embodiment describes a method for preparing boron-doped low-terminal chloride-based polymethylsilanes, the preparation method comprising the following steps:

[0072] (a) Under an inert gas atmosphere, metallic sodium is cut and crushed to obtain square fragments of metallic sodium with a side length of 3~5cm;

[0073] (b) With a solid-liquid ratio of sodium metal fragments to organic solvent of 1:12, sodium metal fragments are added to organic solvent under stirring at 200 rpm and heated to 105°C and kept at that temperature until the sodium metal is in a molten state to obtain a mixture; the organic solvent is a mixture of xylene and cyclohexane in a volume ratio of 9:1.

[0074] (c) Stir the mixture at 500 rpm for 40 min, and then cool the mixture to below 70°C at a cooling rate of 20°C / min while stirring at 900 rpm (cooling method is solvent quenching and jacketed cold bath, solvent is the same as the organic solvent in step (b)) to obtain sodium sand mixture.

[0075] (d) Dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 were mixed and added dropwise to a sodium sand mixture for Wurtz coupled polymerization. After the reaction was completed, a capping agent was added for capping. The reaction solution was then cooled, separated from the solid, and distilled to obtain the polymethylsilane. The volume ratio of dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 was 1:0.08:1:0.2; the molar ratio of the sum of the molar numbers of dichloromethylsilane and dichloromethylborane to sodium sand was 1:2.1; the dropping conditions were: temperature 70℃, dropping rate 0.8 L / h, and stirring speed 400 rpm; the Wurtz coupled polymerization conditions were: temperature 100℃. The stirring rate was 800 rpm, the reaction time was 12 h, and the nitrogen flow rate was 0.8 L / min. The end-capping agent was trimethylethoxysilane. The molar ratio of the end-capping agent to dichloromethylsilane was 0.01:1. The end-capping reaction conditions were as follows: temperature was 70℃, stirring rate was 800 rpm, reaction time was 1.5 h, and nitrogen flow rate was 0.8 L / min.

[0076] Comparative Example 1

[0077] This comparative example illustrates a method for preparing boron-doped polymethylsilane with a low-terminal chloride group, the method comprising the following steps:

[0078] (a) Under an inert gas atmosphere, metallic sodium is cut and crushed to obtain square fragments of metallic sodium with a side length of 3~5cm;

[0079] (b) With a solid-liquid ratio of sodium metal fragments to organic solvent of 1:12, sodium metal fragments are added to organic solvent under stirring at 200 rpm and heated to 105°C and kept at that temperature until the sodium metal is in a molten state to obtain a mixture; the organic solvent is xylene.

[0080] (c) Stir the mixture at 500 rpm for 40 min, and then cool the mixture to below 70°C at a cooling rate of 20°C / min while stirring at 900 rpm (cooling method is solvent quenching and jacketed cold bath, solvent is the same as the organic solvent in step (b)) to obtain sodium sand mixture.

[0081] (d) Dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 were mixed and added dropwise to a sodium sand mixture for Wurtz coupled polymerization. After the reaction was completed, a capping agent was added for capping. The reaction solution was then cooled, separated from the solid, and distilled to obtain the polymethylsilane. The volume ratio of dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 was 1:0.08:1:0.2; the molar ratio of the sum of the molar numbers of dichloromethylsilane and dichloromethylborane to sodium sand was 1:2.1; the dropping conditions were: temperature 70℃, dropping rate 0.8 L / h, and stirring speed 400 rpm; the Wurtz coupled polymerization conditions were: temperature 100℃. The stirring rate was 800 rpm, the reaction time was 12 h, and the nitrogen flow rate was 0.8 L / min. The end-capping agent was trimethylethoxysilane. The molar ratio of the end-capping agent to dichloromethylsilane was 0.01:1. The end-capping reaction conditions were as follows: temperature was 70℃, stirring rate was 800 rpm, reaction time was 1.5 h, and nitrogen flow rate was 0.8 L / min.

[0082] Comparative Example 2

[0083] This comparative example illustrates a method for preparing boron-doped polymethylsilane with a low-terminal chloride group, the method comprising the following steps:

[0084] (a) Under an inert gas atmosphere, metallic sodium is cut and crushed to obtain square fragments of metallic sodium with a side length of 3~5cm;

[0085] (b) With a solid-liquid ratio of sodium metal fragments to organic solvent of 1:12, sodium metal fragments are added to organic solvent under stirring at 200 rpm and heated to 105°C and kept at that temperature until the sodium metal is in a molten state to obtain a mixture; the organic solvent is a mixture of xylene and n-hexane in a volume ratio of 9:1.

[0086] (c) Stir the mixture at 500 rpm for 40 min, and then cool the mixture to below 70°C at a cooling rate of 20°C / min while stirring at 900 rpm (cooling method is solvent quenching and jacketed cold bath, solvent is the same as the organic solvent in step (b)) to obtain sodium sand mixture.

[0087] (d) Dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 were mixed and added dropwise to a sodium sand mixture for Wurtz coupled polymerization. After the reaction was completed, a capping agent was added for capping. The reaction solution was then cooled, separated from the solid, and distilled to obtain the polymethylsilane. The volume ratio of dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 was 1:0.08:1:0.2; the molar ratio of the sum of the molar numbers of dichloromethylsilane and dichloromethylborane to sodium sand was 1:2.1; the dropping conditions were: temperature 70℃, dropping rate 0.8 L / h, and stirring speed 400 rpm; the Wurtz coupled polymerization conditions were: temperature 100℃. The stirring rate was 800 rpm, the reaction time was 12 h, and the nitrogen flow rate was 0.8 L / min. The end-capping agent was trimethylethoxysilane. The molar ratio of the end-capping agent to dichloromethylsilane was 0.01:1. The end-capping reaction conditions were as follows: temperature was 70℃, stirring rate was 800 rpm, reaction time was 1.5 h, and nitrogen flow rate was 0.8 L / min.

[0088] Comparative Example 3

[0089] This comparative example illustrates a method for preparing boron-doped polymethylsilane with a low-terminal chloride group, the method comprising the following steps:

[0090] (a) Under an inert gas atmosphere, metallic sodium is cut and crushed to obtain square fragments of metallic sodium with a side length of 3~5cm;

[0091] (b) With a solid-liquid ratio of sodium metal fragments to organic solvent of 1:12, sodium metal fragments are added to organic solvent under stirring at 200 rpm and heated to 105°C and kept at that temperature until the sodium metal is in a molten state to obtain a mixture; the organic solvent is a mixture of xylene and cyclohexane in a volume ratio of 9:1.

[0092] (c) Stir the mixture at 500 rpm for 40 min, and then cool the mixture to below 70°C at a cooling rate of 10°C / min while stirring at 900 rpm (cooling method is solvent quenching and jacketed cold bath, solvent is the same as the organic solvent in step (b)) to obtain sodium sand mixture.

[0093] (d) Dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 were mixed and added dropwise to a sodium sand mixture for Wurtz coupled polymerization. After the reaction was completed, a capping agent was added for capping. The reaction solution was then cooled, separated from the solid, and distilled to obtain the polymethylsilane. The volume ratio of dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 was 1:0.08:1:0.2; the molar ratio of the sum of the molar numbers of dichloromethylsilane and dichloromethylborane to sodium sand was 1:2.1; the dropping conditions were: temperature 70℃, dropping rate 0.8 L / h, and stirring speed 400 rpm; the Wurtz coupled polymerization conditions were: temperature 100℃. The stirring rate was 800 rpm, the reaction time was 12 h, and the nitrogen flow rate was 0.8 L / min. The end-capping agent was trimethylethoxysilane. The molar ratio of the end-capping agent to dichloromethylsilane was 0.01:1. The end-capping reaction conditions were as follows: temperature was 70℃, stirring rate was 800 rpm, reaction time was 1.5 h, and nitrogen flow rate was 0.8 L / min.

[0094] Comparative Example 4

[0095] This comparative example illustrates a method for preparing boron-doped polymethylsilane with a low-terminal chloride group, the method comprising the following steps:

[0096] (a) Under an inert gas atmosphere, metallic sodium is cut and crushed to obtain square fragments of metallic sodium with a side length of 3~5cm;

[0097] (b) With a solid-liquid ratio of sodium metal fragments to organic solvent of 1:12, sodium metal fragments are added to organic solvent under stirring at 200 rpm and heated to 105°C and kept at that temperature until the sodium metal is in a molten state to obtain a mixture; the organic solvent is a mixture of xylene and cyclohexane in a volume ratio of 9:1.

[0098] (c) Stir the mixture at 500 rpm for 40 min, and then cool the mixture to below 70°C at a cooling rate of 20°C / min while stirring at 500 rpm (cooling method is solvent quenching and jacketed cold bath, solvent is the same as the organic solvent in step (b)) to obtain sodium sand mixture.

[0099] (d) Dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 were mixed and added dropwise to a sodium sand mixture for Wurtz coupled polymerization. After the reaction was completed, a capping agent was added for capping. The reaction solution was then cooled, separated from the solid, and distilled to obtain the polymethylsilane. The volume ratio of dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 was 1:0.08:1:0.2; the molar ratio of the sum of the molar numbers of dichloromethylsilane and dichloromethylborane to sodium sand was 1:2.1; the dropping conditions were: temperature 70℃, dropping rate 0.8 L / h, and stirring speed 400 rpm; the Wurtz coupled polymerization conditions were: temperature 100℃. The stirring rate was 800 rpm, the reaction time was 12 h, and the nitrogen flow rate was 0.8 L / min. The end-capping agent was trimethylethoxysilane. The molar ratio of the end-capping agent to dichloromethylsilane was 0.01:1. The end-capping reaction conditions were as follows: temperature was 70℃, stirring rate was 800 rpm, reaction time was 1.5 h, and nitrogen flow rate was 0.8 L / min.

[0100] Comparative Example 5

[0101] This comparative example illustrates a method for preparing boron-doped polymethylsilane with a low-terminal chloride group, the method comprising the following steps:

[0102] (a) Under an inert gas atmosphere, metallic sodium is cut and crushed to obtain square fragments of metallic sodium with a side length of 3~5cm;

[0103] (b) With a solid-liquid ratio of sodium metal fragments to organic solvent of 1:12, sodium metal fragments are added to organic solvent under stirring at 200 rpm and heated to 105°C and kept at that temperature until the sodium metal is in a molten state to obtain a mixture; the organic solvent is a mixture of xylene and cyclohexane in a volume ratio of 9:1.

[0104] (c) Stir the mixture at 500 rpm for 40 min, and then cool the mixture to below 70°C at a cooling rate of 20°C / min while stirring at 900 rpm (cooling method is solvent quenching and jacketed cold bath, solvent is the same as the organic solvent in step (b)) to obtain sodium sand mixture.

[0105] (d) Dichloromethylsilane, dichloromethylborane, and tetrahydrofuran were mixed and added dropwise to a sodium sand mixture for Wurtz coupled polymerization. After the reaction was completed, a capping agent was added for capping. The reaction solution was then cooled, separated from the solid, and distilled to obtain the polymethylsilane. The volume ratio of dichloromethylsilane, dichloromethylborane, and tetrahydrofuran was 1:0.08:1.2; the molar ratio of the sum of the molar numbers of dichloromethylsilane and dichloromethylborane to that of sodium sand was 1:2.1; the dropping conditions were: temperature 70℃, dropping rate 0.8 L / h, and stirring speed 400 rpm; the Wurtz coupled polymerization conditions were: temperature 100℃. The stirring rate was 800 rpm, the reaction time was 12 h, and the nitrogen flow rate was 0.8 L / min. The end-capping agent was trimethylethoxysilane. The molar ratio of the end-capping agent to dichloromethylsilane was 0.01:1. The end-capping reaction conditions were as follows: temperature was 70℃, stirring rate was 800 rpm, reaction time was 1.5 h, and nitrogen flow rate was 0.8 L / min.

[0106] Comparative Example 6

[0107] This comparative example illustrates a method for preparing a low-terminal chlorine-based polymethylsilane, the method comprising the following steps:

[0108] (a) Under an inert gas atmosphere, metallic sodium is cut and crushed to obtain square fragments of metallic sodium with a side length of 3~5cm;

[0109] (b) With a solid-liquid ratio of sodium metal fragments to organic solvent of 1:12, sodium metal fragments are added to organic solvent under stirring at 200 rpm and heated to 105°C and kept at that temperature until the sodium metal is in a molten state to obtain a mixture; the organic solvent is a mixture of xylene and cyclohexane in a volume ratio of 9:1.

[0110] (c) Stir the mixture at 500 rpm for 40 min, and then cool the mixture to below 70°C at a cooling rate of 20°C / min while stirring at 900 rpm (cooling method is solvent quenching and jacketed cold bath, solvent is the same as the organic solvent in step (b)) to obtain sodium sand mixture.

[0111] (d) Dichloromethylsilane, tetrahydrofuran, and 15-crown ether-5 were mixed and added dropwise to a sodium sand mixture for Wurtz coupled polymerization. After the reaction was completed, a capping agent was added for capping. The reaction solution was then cooled, separated from the solid, and distilled to obtain the polymethylsilane. The volume ratio of dichloromethylsilane, tetrahydrofuran, and 15-crown ether-5 was 1.08:1:0.2; the molar ratio of dichloromethylsilane to sodium sand was 1:2.1; the dropping conditions were: temperature 70℃, dropping rate 0.8 L / h, and stirring speed 400 rpm; the Wurtz coupled polymerization conditions were: temperature 100℃. The stirring rate was 800 rpm, the reaction time was 12 h, and the nitrogen flow rate was 0.8 L / min. The end-capping agent was trimethylethoxysilane. The molar ratio of the end-capping agent to dichloromethylsilane was 0.01:1. The end-capping reaction conditions were as follows: temperature was 70℃, stirring rate was 800 rpm, reaction time was 1.5 h, and nitrogen flow rate was 0.8 L / min.

[0112] Experimental Example

[0113] Sodium sand mixtures from Example 3 and Comparative Examples 1-4 were obtained, and after settling and filtration, sodium sand was obtained.

[0114] Sodium sand prepared in Example 3, such as Figure 1 As shown, the sodium sand prepared in Comparative Examples 1-4 are respectively shown in the diagrams. Figures 2-5 ;

[0115] Boron-doped low-terminal chloride polymethylsilanes were prepared according to the preparation methods of Examples 3 and Comparative Examples 1-6, respectively.

[0116] The yield of the above preparation method was calculated, and the calculation formula is shown in Equation 1. The calculation results are shown in Table 1.

[0117] Formula 1

[0118] In the formula, γ is the yield of synthesized polymethylsilane, %; m is the actual yield, kg; and M is the theoretical yield, kg.

[0119] The molecular weight, molecular weight distribution, porosity, and chlorine content of the boron-doped low-terminal chlorine polymethylsilane were calculated, and the results are shown in Table 1.

[0120] The chlorine content and molecular weight of the different polymethylsilanes obtained were detected using the following methods:

[0121] Infrared spectroscopy analysis was performed on the polymethylsilane prepared in Example 3: a Nicolet-360 FT-IR spectrometer (Japan) was used. Solid samples were prepared using the KBr pellet method, and liquid samples were prepared using the KBr film coating method. Samples unstable in air were prepared beforehand in a nitrogen atmosphere. FT-IR scanning range: 400~4000 cm⁻¹ -1 Scanning rate 3cm -1 / sec; the result is as follows Figure 6 As shown.

[0122] Molecular weight (Mn): Determined by gel permeation chromatography (GPC) using THF as the mobile phase at a flow rate of 1 ml / min. Test method: Care must be taken to prevent the introduction of impurities at each step of the procedure. The syringe must be washed three times with standard purified THF solvent, and the sample solution must be thoroughly filtered. Prepare a THF solution of approximately 1 mg / ml PMS concentration. After the recorder baseline has stabilized, rapidly inject 15 μL. Normalize the recorded elution curve.

[0123] Porosity testing: water displacement method.

[0124] Chlorine content determination: Hydrolysis titration method was used.

[0125] Table 1

[0126] Group Yield (%) Chlorine content (Wt%) Molecular weight (Mw) Molecular weight distribution (Mn / Mw) Porosity (%) Example 3 80.68 0.26 982 1.37 9.25 Comparative Example 1 67.20 0.39 746 1.65 15.98 Comparative Example 2 73.68 0.32 787 1.86 17.36 Comparative Example 3 72.43 0.28 864 1.58 12.05 Comparative Example 4 70.84 0.22 842 1.79 14.52 Comparative Example 5 80.14 0.36 896 1.42 13.50 Comparative Example 6 79.80 0.25 912 1.65 20.35

[0127] As shown in Table 1:

[0128] Compared to the comparative example, the polymethylsilane prepared in this application has better yield, lower aluminum content, and lower kJ / g efficiency.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a boron-doped polymethylsilane with a low-terminal chloride group, characterized in that, The preparation method includes the following steps: (a) Under an inert gas atmosphere, metallic sodium is cut and crushed to obtain metallic sodium fragments; (b) Under stirring conditions, sodium metal fragments are added to an organic solvent and heated until the sodium metal is molten to obtain a mixture; the organic solvent is a mixture of xylene and cyclohexane; (c) Stir the mixture at a stirring speed of 400~600 rpm for a period of time, and then cool the mixture at a stirring speed of 800~1000 rpm and a cooling rate of 15~25℃ / min to obtain a sodium sand mixture. (d) Dichloromethylsilane, dichloromethylboron, tetrahydrofuran and 15-crown ether-5 are mixed and then added dropwise to a sodium sand mixture to carry out a Wurtz coupled polymerization reaction. After the reaction is completed, a capping agent is added to carry out a capping reaction. The reaction solution is then cooled, separated into solid and liquid, and distilled to obtain the boron-doped low-terminal chloride polymethylsilane.

2. The preparation method according to claim 1, characterized in that, In step (b), the solid-liquid ratio of the sodium metal fragments and the organic solvent is 1:(10~15).

3. The preparation method according to claim 1, characterized in that, In step (b), the stirring speed is 100~250 rpm; the volume ratio of xylene to cyclohexane is (8~10):1; and the temperature is heated to 99~110℃.

4. The preparation method according to claim 1, characterized in that, In step (c), the stirring is carried out for 30 to 60 minutes; the temperature is then lowered to below 70°C.

5. The preparation method according to claim 1, characterized in that, In step (a), the sodium metal fragments are cubes with a side length of 3-5 cm.

6. The preparation method according to claim 1, characterized in that, In step (c), the cooling method is solvent quenching and jacketed cold bath.

7. The preparation method according to claim 1, characterized in that, In step (d), the volume ratio of dichloromethylsilane, dichloromethylborane, tetrahydrofuran, and 15-crown ether-5 is 1:(0.05~0.1):(0.8~1.2):(0.02~0.3); the molar ratio of the sum of the moles of dichloromethylsilane and dichloromethylborane to that of sodium sand is 1:(2~2.2).

8. The preparation method according to claim 1, characterized in that, In step (d), the dropping conditions are: temperature 60~80℃, dropping rate 0.5~1L / h, and stirring speed 200~600rpm; The Wurtz coupled polymerization reaction conditions are: temperature 90~110℃, stirring speed 400~1000rpm, reaction time 10~15h, and nitrogen flow rate 0.5~1L / min.

9. The preparation method according to claim 1, characterized in that, In step (d), the capping agent is selected from at least one of trimethylchlorosilane, trimethylethoxysilane, trimethylsilanol, dimethylhydrosilyltrimethylsilane, and methyldihydrosilyltrimethylsilane; The molar ratio of the capping agent to dichloromethylsilane is (0.0025~0.0125):1; The end-capping reaction conditions are as follows: temperature 65~80℃, stirring speed 400~1000rpm, reaction time 1~2h, and nitrogen flow rate 0.5~1L / min.

10. The boron-doped low-terminal chloride polymethylsilane prepared by the preparation method according to any one of claims 1 to 9.

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