A method for preparing a self-crosslinkable polysiloxane with adjustable boron content
By using Karstedt catalyst to catalyze the cross-linking reaction of Si-H bonds and carbon-carbon double bonds, a self-crosslinking polysiloxane with adjustable boron content was prepared. This solved the problems of unadjustable boron content and large weight loss in the existing technology, achieving high ceramic yield and excellent processing performance, and expanding its application in aerospace and other fields.
Patent Information
- Application Number
- CN202310630916.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-05-31
- Publication Date
- 2025-12-02
- Estimated Expiration
- 2043-05-31
AI Technical Summary
Existing technologies make it difficult to prepare self-crosslinkable polysiloxane with adjustable boron content, resulting in significant weight loss during ceramization and limiting its application in high-temperature ablation-resistant fields such as aerospace.
The cross-linking reaction of Si-H bonds and carbon-carbon double bonds was catalyzed by Karstedt catalyst. The boron content of polysiloxane was adjusted by controlling the amount of carborane and chlorosilane added, and a three-stage heating reaction was carried out to obtain self-crosslinkable polysiloxane with adjustable boron content.
It improves ceramic yield, reduces weight loss, and provides excellent processing performance. It is suitable for the preparation of high-temperature resistant, oxidation-resistant, and ablation-resistant materials, expanding its applications in aerospace and other fields.
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Figure CN116675864B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer materials technology and relates to a method for preparing a self-crosslinkable polysiloxane with adjustable boron content. Background Technology
[0002] Polymer-derived silicon boron carbon nitride (SiBCN) ceramics have been extensively studied over the past 50 years. Part of the motivation is their ability to be preformed using polymer processing techniques, and another is the excellent thermal, mechanical, and chemical stability of the resulting ceramics at high temperatures. Numerous applications have been developed across various fields, including high-temperature resistant and functional materials in electrical engineering and nanoelectronics. In the preparation of SiBCN ceramics, the structure of the polymer precursor plays a decisive role in the final ceramic structure and properties; therefore, the structural design and elemental content control of the ceramic precursor—polyborosilicate—have received considerable attention. Introducing active reactive sites into the polyborosilicate molecule can increase the reactivity of the polymer during the ceramicization transformation process, effectively increasing the ceramic yield and providing new modification sites. Furthermore, carboranes are a class of icosahedral borohydrides formed by replacing two equally charged BH units with two CH units. This closed, cage-like structure possesses a highly symmetrical framework and a large volume, while also exhibiting many typical properties of aromatic structures, as well as thermal and chemical stability. Therefore, using high-boron-content carboranes as the boron source for polysiloxanes (PSBZ) facilitates wide-range control of the boron content in the precursor, promoting the further application and expansion of related materials in high-temperature ablation-resistant fields such as aerospace. It can also significantly improve the high-temperature carbon residue rate of polymer resin structures and the ceramicization yield of embedded structures. In summary, self-crosslinking polysiloxanes with controllable boron content have significant value in the aerospace industry and in fields requiring high temperature resistance, oxidation resistance, and ablation resistance. Summary of the Invention
[0003] The purpose of this invention is to address the aforementioned problems in the prior art by proposing a self-crosslinking polysiloxane with adjustable boron content, which utilizes a Karstedt catalyst to catalyze the crosslinking reaction of Si-H bonds and carbon-carbon double bonds.
[0004] The objective of this invention can be achieved through the following technical solutions:
[0005] A method for preparing a self-crosslinkable polysiloxane with adjustable boron content, the method comprising:
[0006] S1. Inert gas is introduced into the reaction flask containing carborane. Then, reaction solvent is added into the reaction flask under ice bath conditions, and n-butyllithium is added dropwise. After the addition is completed, the first reaction is carried out.
[0007] S2. At -40 to -100°C, chlorosilane is added dropwise to the reaction flask containing the reaction product of step S1, which is filled with inert gas. After the addition is complete, the second reaction is carried out.
[0008] S3. Remove lithium salt to obtain monomer CB of polyborosilazane;
[0009] S4. Mix the monomer CB of polyborosilazane, chlorosilane, and amine compounds, and add a reaction solvent to carry out a three-stage heating reaction to obtain polyborosilazane;
[0010] S5. Dissolve polyborosilazane in a solvent and react it with the catalyst at 60–300°C for 2–12 hours.
[0011] The advantage of this invention, which allows for self-crosslinking and adjustable boron content, is that it can catalyze the crosslinking and curing reactions of reactive groups in the polymer, such as Si-H bonds and carbon-carbon double bonds, thereby reducing the weight loss of polyborosilicates during the ceramicization process. This can provide support for subsequent applications such as coating curing or 3D printing technology.
[0012] In step S2, the dropping environment is -40 to -100°C. If the temperature is higher than -40°C, it will cause a violent polymerization reaction between the chlorosilane and the drug in the flask during the dropping process, so that the final product of this step is a polymer, rather than the monomer CB of the target product polyborosilazane.
[0013] Preferably, the structure of the polyborosilazane monomer CB obtained in step S3 is as follows:
[0014]
[0015] Preferably, the carborane in step S1 is one or more of ortho-carborane, meta-carborane, and para-carborane.
[0016] Preferably, the reaction solvent in steps S1 and S4 is one or more of tetrahydrofuran, xylene, and n-hexane.
[0017] Preferably, the mass-to-volume ratio of carborane to reaction solvent in step S1 is 1:(13-20).
[0018] Preferably, the molar ratio of carborane to n-butyllithium in step S1 is 1:(2-3).
[0019] Preferably, the molar ratio of carborane in step S1 to chlorosilane in step S2 is 1:(5-12).
[0020] Preferably, the molar ratio of carborane in step S1 to chlorosilane in step S4 is 1:(0.1-20).
[0021] Preferably, the first reaction in step S1 is carried out at 10-60°C for 1-10 hours; the second reaction in step S2 is carried out at 10-60°C for 5-50 hours.
[0022] Preferably, the lithium salt removal process in step S3 includes: hexane extraction followed by filtration.
[0023] Preferably, in step S4, the molar ratio of the monomer monomer CB, chlorosilane, and amine compound of the polyborosilazane is 1:(0.01-20):(0.1-30).
[0024] More preferably, the molar ratio of chlorosilane to amine compound in step S4 is 1:(1.01-30).
[0025] Preferably, step S4 involves a three-stage heating process: the first stage temperature is 15–37°C, and the reaction time is 4–10 h; the second stage temperature is 130–180°C, and the reaction time is 0.5–2 h; and the third stage temperature is 200–300°C, and the reaction time is 3–20 h.
[0026] Preferably, the catalyst in step S5 is a Karstedt catalyst, and the amount added is 0.01 to 10.0 wt.%.
[0027] Preferably, the chlorosilane includes one or more of dichloromethylsilane, dichloromethylvinylsilane, and dichlorophenylvinylsilane.
[0028] Further preferably, the chlorosilanes in steps S2 and S4 are the same or different.
[0029] Preferably, the amine compound includes one or more of hexamethyldisilazane (hexamethyldisilaimide), ethylenediamine, and allylamine.
[0030] Preferably, the entire preparation process is carried out under an inert gas atmosphere.
[0031] The present invention also discloses a self-crosslinking polysiloxane with adjustable boron content, wherein the self-crosslinking polysiloxane with adjustable boron content is PBSZx:y, and the structure is as follows; wherein x>0, y>0.
[0032]
[0033] This invention also discloses that self-crosslinking polysiloxane with adjustable boron content can be used to prepare high-temperature resistant, oxidation-resistant, and ablation-resistant materials.
[0034] Compared with the prior art, the present invention has the following beneficial effects:
[0035] 1. This invention involves mixing the monomer monomer CB of polyborosilazane, chlorosilane, and amine compounds, and carrying out a three-stage heating reaction to obtain the product, which is then reacted with a Karstedt catalyst to catalyze the solidification reaction of Si-H bonds and carbon-carbon double bonds.
[0036] 2. The ceramic yield of the present invention is significantly improved after catalysis by Karstedt catalyst;
[0037] 3. By adjusting the amount of carborane added in step S1 and chlorosilane added in step S4, the present invention controls the value of x:y in polysiloxane PBSZx:y, thereby obtaining polyborosilicates with different boron contents, such that x>0 and y>0.
[0038] 4. The self-crosslinking polysiloxane with adjustable boron content prepared by this invention can be a low-viscosity liquid to a resin-type solid, and is easily soluble in various organic solvents.
[0039] 5. The self-crosslinkable polyborosilicate with adjustable boron content obtained by this invention has a suitable melting temperature and excellent processing performance; it can be used to prepare high-temperature resistant, oxidation-resistant, and ablation-resistant composite materials, ceramic precursors, high-temperature resistant coatings, etc. Attached Figure Description
[0040] Figure 1 This is a flowchart illustrating the preparation process of the self-crosslinking polyborosilicate with adjustable boron content according to the present invention.
[0041] Figure 2 The image shows the self-crosslinking polyborosilicate with adjustable boron content and its FT-IR image after curing, as described in Example 1 of this invention.
[0042] Figure 3 The image shows the TG curve of the self-crosslinking polyborosilicate with adjustable boron content and the cured polyborosilicate from Example 1 of this invention. Detailed Implementation
[0043] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.
[0044] Unless otherwise specified, the materials used in this invention are commercially available products, and the methods used are conventional technical means.
[0045] Example 1
[0046] Preparation of self-crosslinkable polyborosilicates with adjustable boron content:
[0047] S1. Add 2.46 g (0.017 mol) of m-carborane to a 250 mL four-necked flask equipped with a magnetic stirrer and a constant pressure dropping funnel to replace the gas in the system with an inert gas (nitrogen, the same below), add 40 mL of tetrahydrofuran, and add 15 mL (0.036 mol) of n-butyllithium dropwise under ice-water bath conditions. React at room temperature for 5 hours.
[0048] S2. At -80℃, 23 mL (0.17 mol) of dichloromethylvinylsilane was added dropwise to the reaction flask containing the reaction product of step S1, which was filled with inert gas. After the addition was complete, the mixture was reacted at 25℃ for 12 h.
[0049] S3, hexane extraction, followed by filtration to remove lithium salt, yielding polyborosilicate monomer CB;
[0050] S4. Add 40 mL of xylene to a 250 mL four-necked flask equipped with a mechanical stirrer and a constant pressure dropping funnel to prepare monomer CB. Add 32 mL (0.3 mol) of dichloromethylsilane and 73 mL (0.35 mol) of hexamethyldisilazane dropwise under an ice-water bath. After reacting at room temperature for 6 hours, raise the temperature to 150 °C to distill off the solvent and byproducts. Then raise the temperature to 260 °C and react for 8 hours to obtain the product polyborosilicate.
[0051] S5. Under an inert atmosphere, the product polyborosilicate was dissolved in tetrahydrofuran, and 0.05 wt.% of Karstedt catalyst was added and reacted at 70°C for 10 hours.
[0052] The self-crosslinking polyborosilicate with adjustable boron content obtained in this embodiment is PBSZ18:1.
[0053] Example 2
[0054] Preparation of self-crosslinkable polyborosilicates with adjustable boron content:
[0055] S1. Add 7.23 g (0.05 mol) of m-carborane to a 250 mL four-necked flask equipped with a magnetic stirrer and a constant pressure dropping funnel to replace the gas in the system with an inert gas. Add 90 mL of tetrahydrofuran and add 44 mL (0.105 mol) dropwise under ice-water bath conditions. React at room temperature for 5 hours.
[0056] S2. At -80℃, 52 mL (0.5 mol) of dichloromethylsilane was added dropwise to the reaction flask containing the reaction product of step S1, which was filled with inert gas. After the addition was complete, the mixture was reacted at 25℃ for 12 h.
[0057] S3, hexane extraction, followed by filtration to remove lithium salt, yielding polyborosilicate monomer CB;
[0058] S4. Add 40 mL of xylene to a 250 mL four-necked flask equipped with a mechanical stirrer and a constant pressure dropping funnel to prepare monomer CB. Add 1.5 mL (0.012 mol) of dichloromethylvinylsilane and 29 mL (0.14 mol) of hexamethyldisilazane dropwise under an ice-water bath. After reacting at room temperature for 6 hours, raise the temperature to 150 °C to distill off the solvent and byproducts. Then raise the temperature to 260 °C and react for 8 hours to obtain the product polyborosilicate.
[0059] S5. Under an inert atmosphere, the product polyborosilicate was dissolved in tetrahydrofuran, and 0.05 wt.% of Karstedt catalyst was added and the reaction was carried out at 75°C for 9 hours.
[0060] In this embodiment, the self-crosslinking polyborosilicate with adjustable boron content was prepared as PBSZ0.24:1.
[0061] Example 3
[0062] Preparation of self-crosslinkable polyborosilicates with adjustable boron content:
[0063] S1. Add 2.46 g (0.017 mol) of p-carborane to a 250 mL four-necked flask equipped with a magnetic stirrer and a constant pressure dropping funnel to replace the gas in the system with an inert gas. Add 40 mL of tetrahydrofuran and add 15 mL (0.036 mol) of n-butyllithium dropwise under ice-water bath conditions. React at room temperature for 5 hours.
[0064] S2. At -80℃, 23 mL (0.17 mol) of dichloromethylvinylsilane was added dropwise to the reaction flask containing the reaction product of step S1, which was filled with inert gas. After the addition was complete, the mixture was reacted at 25℃ for 12 h.
[0065] S3, hexane extraction, followed by filtration to remove lithium salt, yielding polyborosilicate monomer CB;
[0066] S4. Add 40 mL of xylene to a 250 mL four-necked flask equipped with a mechanical stirrer and a constant pressure dropping funnel to prepare monomer CB. Add 32 mL (0.3 mol) of dichloromethylsilane and 73 mL (0.35 mol) of hexamethyldisilazane dropwise under an ice-water bath. After reacting at room temperature for 6 hours, raise the temperature to 150 °C to distill off the solvent and byproducts. Then raise the temperature to 260 °C and react for 8 hours to obtain the product polyborosilicate.
[0067] S5. Under an inert atmosphere, the product polyborosilicate was dissolved in tetrahydrofuran, and 0.05 wt.% of Karstedt catalyst was added and reacted at 70°C for 10 hours.
[0068] The self-crosslinking polyborosilicate with adjustable boron content obtained in this embodiment is PBSZ18:1.
[0069] In Examples 1-3, the ceramic yields of self-crosslinking polyborosilicates with adjustable boron content reached over 70 wt%; however, without a catalyst, the ceramic yield was low (45 wt%), and the product exhibited a 3056 cm⁻¹ in FT-IR. -1 And 1593cm -1 The signal peak at the carbon-carbon double bond.
[0070] Figure 1 This is a flowchart illustrating the preparation process of self-crosslinkable polyborosilicates with adjustable boron content.
[0071] Figure 2 The image shows the FT-IR spectra of the self-crosslinking polyborosilicate with adjustable boron content from Example 1 and its cured form. The image shows that the cured polyborosilicate is 3056 cm⁻¹. -1 And 1593cm -1 The almost disappearance of the signal peak representing the carbon-carbon double bond indicates that the Karstedt catalyst used in step S5 significantly catalyzed the cross-linking reaction of the carbon-carbon double bond, causing the signal peak of the carbon-carbon double bond to disappear.
[0072] Figure 3 In Example 1, the self-crosslinkable polyborosilicate with adjustable boron content and its thermogravimetric analysis (TGA) curves after curing are shown. As can be seen from the figures, compared with the polyborosilicate before curing, the cured polyborosilicate exhibits a lower weight loss rate at high temperatures, and the ceramic yield increases from 40 wt% to 60 wt% under an argon atmosphere. Therefore, the self-crosslinkable polyborosilicate with adjustable boron content of this invention can be extended to applications such as the preparation of ceramic coatings and 3D printing technology.
[0073] In summary, compared with the products obtained by existing polyborosilicate synthesis methods, the polyborosilicate prepared by the present invention, which is self-crosslinkable and has adjustable boron content, has advantages such as self-crosslinking reactive sites, adjustable boron content, and good heat resistance. Moreover, the preparation process produces fewer by-products and is simpler.
[0074] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.
Claims
1. A method for preparing a self-crosslinkable polysiloxane with adjustable boron content, characterized in that, The preparation method includes: S1. Inert gas is introduced into the reaction flask containing carborane. Then, reaction solvent is added into the reaction flask under ice bath conditions, and n-butyllithium is added dropwise. After the addition is completed, the first reaction is carried out. S2. At -40~-100℃, chlorosilane is added dropwise to the reaction flask containing the reaction product of step S1, which is filled with inert gas. After the addition is complete, the second reaction is carried out. S3. The lithium salt is removed to obtain the monomer CB of polyborosilazane. S4. Mix the monomer CB of polyborosilazane, chlorosilane, and amine compounds, and add a reaction solvent to carry out a three-stage heating reaction to obtain polyborosilazane; S5. Dissolve polyborosilicate in a solvent and react with Karstedt catalyst at 60~300℃ for 2~12 hours; In step S2, the chlorosilane is dichloromethylsilane, and in step S4, the chlorosilane is dichloromethylvinylsilane. Alternatively, the chlorosilane in step S2 may be dichloromethylvinylsilane, and the chlorosilane in step S4 may be dichloromethylsilane.
2. The method for preparing the self-crosslinkable polysiloxane with adjustable boron content according to claim 1, characterized in that, The molar ratio of carborane in step S1 to chlorosilane in step S2 is 1:(5~12).
3. The method for preparing the self-crosslinkable polysiloxane with adjustable boron content according to claim 1, characterized in that, The molar ratio of carborane in step S1 to chlorosilane in step S4 is 1:(0.1~20).
4. The method for preparing the self-crosslinkable polysiloxane with adjustable boron content according to claim 1, characterized in that, In step S4, the molar ratio of the monomer CB, chlorosilane, and amine compound of polyborosilazane is 1:(0.01~20):(0.1~30).
5. The method for preparing the self-crosslinkable polysiloxane with adjustable boron content according to claim 1, characterized in that, In step S4, the temperature rises in three stages: the first stage temperature is 15~37℃ and the reaction time is 4~10h; the second stage temperature is 130~180℃ and the reaction time is 0.5~2h; and the third stage temperature is 200~300℃ and the reaction time is 3~20h.
6. The method for preparing the self-crosslinkable polysiloxane with adjustable boron content according to claim 1, characterized in that, The amount of catalyst added in step S5 is 0.01~10.0 wt.%.
7. The method for preparing the self-crosslinkable polysiloxane with adjustable boron content according to claim 1, characterized in that, The entire preparation process is carried out under an inert gas atmosphere.
8. The method for preparing the self-crosslinkable polysiloxane with adjustable boron content according to claim 1, characterized in that, The amine compounds include one or more of hexamethyldisilazane, ethylenediamine, and allylamine.
9. A self-crosslinkable polysiloxane with adjustable boron content, characterized in that, The polysiloxane with adjustable boron content and self-crosslinking capability is prepared by the method described in any one of claims 1 to 8, wherein the polysiloxane with adjustable boron content and self-crosslinking capability is PBSZx:y, where x > 0 and y > 0.
10. An application of the self-crosslinkable polysiloxane with adjustable boron content as described in claim 9, characterized in that, The self-crosslinking polysiloxane with adjustable boron content can be used to prepare high-temperature resistant, oxidation-resistant, and ablation-resistant materials.