A polyborosilicate precursor with controllable B2NH and BNH ratio, its synthesis method and application

Abstract

The present application relates to a kind of B2NH and BNH proportion controllable polysilazane precursor and its synthesis method and application, belong to new material technical field, to solve the ratio of B2NH and BNH in existing method cannot be controlled, thereby at least one of the problems such as poor flexibility, large fluctuation of the high-temperature-resistant coating prepared is poor, etc..The synthesis method of the polysilazane precursor of the present application is to realize the preparation of different structural units in steps, by controlling the ratio of raw materials and reaction conditions of each step to realize the quantitative control of each structure, the cyclic structure synthesized in step (1) is B2NH structure, boron trichloride in step (3) is first reacted with the structural unit containing silicon in step (2), so that B exists as BNH structure, and then reacts with disilazane, thereby avoiding the reaction of boron trichloride alone and disilazane to form B2NH structure, the method of the present application uses step-by-step method, and the ratio of B2NH and BNH in the polysilazane precursor prepared by controlling the ratio of raw materials and conditions in each step is controllable.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and in particular to a polyborosilicate precursor with controllable B2NH and BNH ratio, its synthesis method, and its application. Background Technology

[0002] High-temperature and high-toughness coatings have wide applications in surface thermal protection and stealth of aircraft, rockets, and missiles. SiBCN ceramics prepared by the pyrolysis conversion of polyborosilazane (PBSN) possess excellent properties such as high-temperature resistance, oxidation resistance, and high-temperature creep resistance. They are widely used in the preparation of ceramic fibers, ceramic matrix composites, and high-temperature ceramic coatings, and have broad application prospects and development potential in the aerospace and aviation fields.

[0003] The simplest method for synthesizing polyborosilicates is the "one-pot method," which mainly uses chlorosilanes, boron trichloride, and hexamethyldisilazane as raw materials and prepares polyborosilicates through a high-temperature reaction.

[0004] The PBSN prepared by the above method is mainly used as a SiBCN ceramic precursor, and the ceramic yield is the focus. However, the control of the ratio of B2NH and BNH structural units in the PBSN precursor is not addressed, nor is the use of the PBSN precursor resin for the preparation of high-temperature resistant and high-toughness coatings. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a polyborosilicate precursor with controllable B2NH and BNH ratio, its synthesis method and application, in order to solve at least one of the problems in existing methods where the ratio of B2NH and BNH cannot be controlled, resulting in poor flexibility and large fluctuations in the high-temperature resistant coating.

[0006] In a first aspect, the present invention provides a method for synthesizing a polyborosilicate precursor with a controllable ratio of B2NH and BNH, comprising the following steps:

[0007] (1) Under an inert atmosphere, an organic solvent is added to the reactor, the temperature is lowered, boron trichloride is added, the mixture is mixed evenly, and disilazane is added under heat preservation conditions to carry out the reaction. After the temperature is raised, the reaction continues to obtain the first product.

[0008] (2) Chlorosilane and disilazane are added sequentially to the first product and reacted to obtain the second product;

[0009] (3) Cool the second product, add boron trichloride, stir, add disilazine, and react to obtain the third product;

[0010] (4) The third product is heated and distilled for the first time, and then heated and reacted for the second time to obtain a reaction intermediate. The intermediate is then treated under vacuum and cooled to room temperature to obtain the polyborosilicate precursor with a controllable ratio of B2NH and BNH.

[0011] Furthermore, in step (1), the organic solvent includes one or more of n-hexane, toluene, xylene, and tetrahydrofuran;

[0012] And / or, the molar ratio of disilazane to boron trichloride is 3 to 3.2:1.

[0013] Furthermore, in step (1), the temperature is lowered to -10 to -20°C;

[0014] And / or, the temperature for the heat preservation reaction is -10 to -20℃, and the reaction time is 6 to 8 hours;

[0015] And / or, raise the temperature to 20–30°C and continue the reaction for 4–6 hours.

[0016] Furthermore, in step (2), the molar ratio of chlorosilane to disilazine is 1:1 to 1:2.

[0017] Furthermore, the mass ratio of the organic solvent in step (1) to the total mass ratio of boron trichloride and chlorosilane in step (2) is 3:1 to 1:1.

[0018] Furthermore, in step (3), the temperature is lowered to -10 to -20°C, the stirring time is 1 to 2 hours, and the reaction time is 4 to 8 hours.

[0019] Furthermore, the molar ratio of boron trichloride in step (1) to boron trichloride in step (3) is 1:0.5 to 1:3.

[0020] Furthermore, in steps (1) to (3), the ratio of the total mole of disilazane to the sum of the moles of Si-Cl groups in chlorosilane and the moles of B-Cl groups in boron trichloride added in the whole reaction is 1:1 to 1:2.

[0021] Furthermore, in step (4), the temperature is raised to 130-150℃ at a heating rate of 5-30℃ / h and held for 1-8h;

[0022] And / or, the temperature for the second heating is 160–220℃, and the holding time for the reaction is 2–8 hours.

[0023] Secondly, the present invention provides a polyborosilicate precursor prepared by the synthesis method described above, wherein the ratio of B2NH to BNH in the polyborosilicate precursor is 1:0.5 to 1:3.

[0024] Thirdly, the present invention provides an application of the aforementioned polyborosilazane precursor in the preparation of high-temperature resistant and high-toughness coatings.

[0025] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0026] (1) The method of synthesizing polyborosilicate precursor of the present invention is to prepare different structural units step by step. The quantitative control of each structure is achieved by controlling the proportion of raw materials and reaction conditions in each step. The cyclic structure synthesized in step (1) is B2NH structure. In step (3), boron trichloride first reacts with the silicon-containing structural unit in step (2) so that B exists in the BNH structure, and then reacts with disilicate, thereby avoiding the formation of B2NH structure by boron trichloride reacting alone with disilicate. The method of the present invention adopts a step-by-step method. The proportion of B2NH and BNH in the polyborosilicate precursor prepared by controlling the proportion of raw materials and conditions in each step can be controlled.

[0027] (2) The ratio of B2NH to BNH in the polyborosilicate precursor obtained by the synthesis method of the present invention is 1:0.5 to 1:3, preferably 1:1 to 1:1.8, and the number average molecular weight is 800 to 1500 g / mol;

[0028] (3) The high-temperature resistant and high-toughness coating prepared by using the B2NH and BNH polyborosilicate precursor prepared by the present invention has a flexibility of ≤2mm at room temperature, preferably 1-2mm, and a flexibility of ≤3mm at high temperature (400℃, 1h), preferably 2-3mm.

[0029] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objectives and other advantages of this invention can be realized and obtained through the specific points highlighted in the description. Detailed Implementation

[0030] The principles of the present invention are explained below with reference to specific embodiments, but are not intended to limit the scope of the present invention.

[0031] A specific embodiment of the present invention discloses a method for synthesizing a polyborosilicate precursor with a controllable ratio of B2NH and BNH, comprising the following steps:

[0032] (1) Under an inert atmosphere, an organic solvent is added to the reactor, the temperature is lowered, boron trichloride is added, the mixture is mixed evenly, and disilazane is added under heat preservation conditions to carry out the reaction. After the temperature is raised, the reaction continues to obtain the first product.

[0033] (2) Chlorosilane and disilazane are added sequentially to the first product and reacted to obtain the second product;

[0034] (3) Cool the second product, add boron trichloride, stir, add disilazine, and react to obtain the third product;

[0035] (4) The third product is heated and distilled for the first time, and then heated and reacted for the second time to obtain a reaction intermediate. The intermediate is then treated under vacuum and cooled to room temperature to obtain the polyborosilicate precursor with a controllable ratio of B2NH and BNH.

[0036] Compared with existing technologies, this invention achieves the preparation of different structural units in steps. Quantitative control of each structure is achieved by controlling the proportion of raw materials and reaction conditions in each step. The cyclic structure synthesized in step (1) is a B2NH structure. In step (3), boron trichloride first reacts with the silicon-containing structural unit in step (2), resulting in B existing in the BNH structure, and then reacts with disilazane, thus avoiding the formation of the B2NH structure by boron trichloride reacting alone with disilazane. In traditional one-pot preparation, boron trichloride, compared to chlorosilanes, has higher reactivity and preferentially reacts with disilazane, ultimately forming a precursor where B is predominantly in the B2NH structure. The method of this invention uses a stepwise approach to prepare a polyborosilicate precursor with controllable B2NH and BNH ratios.

[0037] The chemical formula of the disilazane of the present invention is (R 1 R 2 R 3 )2Si2NH, where R 1 R 2 and R 3 Same or different, R 1 R 2 and R 3 The group is independently selected from one of the following groups: H, methyl, ethyl, vinyl.

[0038] The disilazine used in this invention may be one or more of the disilazines mentioned above, or a mixture thereof.

[0039] The reaction equations involved in step (1) are as follows:

[0040]

[0041] It should be noted that the entire reaction of this invention is carried out under an inert atmosphere, wherein the inert atmosphere is nitrogen or argon. The reactor needs to be repeatedly evacuated during the reaction, and the inert atmosphere needs to be replaced at least three times. Boron trichloride in this invention is either a gas or a liquid.

[0042] Specifically, in step (1), the organic solvent includes one or more of n-hexane, toluene, xylene, and tetrahydrofuran. Preferably, the organic solvent is n-hexane.

[0043] Specifically, in step (1), the molar ratio of disilazane to boron trichloride is 3 to 3.2:1, for example, 3.11:1, 3.12:1, 3.13:1, 3.14:1, 3.15:1, 3.16:1, 3.17:1, 3.18:1, 3.19:1.

[0044] In this invention, the molar ratio of disilazane to boron trichloride is selected within the range mentioned above. If the ratio is too low, some boron trichloride will not react completely, and the result of the first step in the reaction formula in step (1) will not be formed. The first product formed by the reaction cannot exist completely in a cyclic form and will have a partially linear structure, that is, B cannot be completely in the B2NH structure. If the ratio is too high, it will inhibit the second step in the reaction formula in step (1).

[0045] Specifically, in step (1), the temperature is lowered to -10 to -20℃, for example, -11℃, -12℃, -13℃, -14℃, -15℃, -16℃, -17℃, -18℃, and -19℃.

[0046] It should be noted that if the reaction temperature is too low, the reaction rate will decrease and the reaction time will be too long. If the reaction temperature is too high, the reaction between boron trichloride and disilazane is an exothermic reaction, and the exothermic reaction will cause the temperature to rise, which will lead to the escape of boron trichloride.

[0047] Specifically, in step (1), the temperature of the heat preservation reaction is -10 to -20℃, for example, -11℃, -12℃, -13℃, -14℃, -15℃, -16℃, -17℃, -18℃, -19℃, and the reaction time is 6 to 8 hours, for example, 6.2 hours, 6.4 hours, 6.8 hours, 7.0 hours, 7.2 hours, 7.4 hours, 7.6 hours, 7.8 hours.

[0048] It should be noted that if the reaction time is too short, boron trichloride cannot react fully with disilazane, resulting in a low synthesis yield; if the time is too long, the reaction yield does not increase significantly.

[0049] Specifically, in step (1), the temperature is raised to 20-30℃, for example, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, and the reaction continues for 4-6 hours, for example, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours, 5.0 hours, 5.2 hours, 5.4 hours, 5.6 hours, 5.8 hours.

[0050] It should be noted that the chemical formula of the chlorosilane in step (2) is as follows: R 4 R 5SiCl2, where R 4 R 5 They can be the same or different, R 4 R 5 The group is independently selected from one of the following groups: H, C1-4 alkanes, and C2-4 alkenes.

[0051] Preferably, the C1-4 alkyl group is a straight-chain or branched saturated monovalent hydrocarbon group having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, butyl, isopropyl, n-butyl, isobutyl, sec-butyl, or tert-butyl. The C2-4 olefin group is a straight-chain or branched olefin group, such as vinyl, allyl, or 1-butenyl.

[0052] The chlorosilanes described in this invention can be one or more of the above-mentioned compounds, or a mixture thereof.

[0053] Specifically, in step (2), the molar ratio of chlorosilane to disilazine is 1:1 to 1:2, for example, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9.

[0054] It should be noted that using the above-mentioned range for the molar ratio of chlorosilane and disilazine ensures that at least one of the chlorine molecules in the dichlorosilane reacts with the disilazine, facilitating the subsequent reaction of boron trichloride with the intermediate formed in this step to form the BNHSi structure. If the ratio is too low, some unreacted dichlorosilane will remain; if the ratio is too high, the boron trichloride added in the third step will react alone with the disilazine to form a cyclic structure.

[0055] Specifically, the mass ratio of the organic solvent in step (1) to the total mass of boron trichloride and chlorosilane in step (2) is 3:1 to 1:1, for example, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2.0:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1.

[0056] Specifically, in step (2), the reaction time is 3 to 4 hours, for example, 3.2 hours, 3.4 hours, 3.6 hours, or 3.8 hours.

[0057] It should be noted that the reaction equations involved in step (2) are as follows:

[0058]

[0059] In the reaction in step (2), dichlorosilane will not react with the first product in step (1), and its activity is not so high. It will preferentially react with disilazane. When the ratio of dichlorosilane to disilazane is less than 1:2, a structure similar to R3Si-NH-R2Si-Cl will exist.

[0060] Specifically, in step (3), the temperature is lowered to -10 to -20℃, for example, -11℃, -12℃, -13℃, -14℃, -15℃, -16℃, -17℃, -18℃, -19℃, the stirring time is 1 to 2 hours, for example, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, and the reaction time is 4 to 8 hours, for example, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours, 5.0 hours, 5.2 hours, 5.4 hours, 5.6 hours, 5.8 hours, 6.0 hours, 6.2 hours, 6.4 hours, 6.6 hours, 6.8 hours, 7.0 hours, 7.2 hours, 7.4 hours, 7.6 hours, 7.8 hours.

[0061] It should be noted that the temperature and stirring time described above are used to allow the newly added boron trichloride to react with the second product obtained in step (2). Too high a temperature will cause the boron trichloride to volatilize due to the heat generated by the reaction, while too low a temperature will reduce the reaction rate. The disilazane is added and reacted for a period of time after the above reaction is complete because the boron trichloride and the second product in step (2) still contain chlorine, allowing it to continue reacting with the disilazane. Too short a reaction time results in incomplete reaction, while extending the time does not significantly increase the yield.

[0062] Specifically, the molar ratio of boron trichloride in step (1) to boron trichloride in step (3) is 1:0.5 to 1:3, for example, 1:0.7, 1:0.9, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2.0, 1:2.2, 1:2.4, 1:2.6, 1:2.8.

[0063] It should be noted that within the above-mentioned range, the ratio of B2NH and BNH in the synthesized polyborosilazane precursor can be controlled more precisely.

[0064] Specifically, the total molar ratio of boron trichloride in step (1) and step (3) to the molar ratio of chlorosilane in step (2) is 1:1 to 1:4, for example, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2.0, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3.0, 1:3.2, 1:3.4, 1:3.6, 1:3.8.

[0065] Specifically, in steps (1) to (3), the ratio of the total moles of disilazane to the sum of the moles of Si-Cl groups in chlorosilane and the moles of B-Cl groups in boron trichloride added in the whole reaction is 1:1 to 1:2, for example, 1:1.2, 1:1.4, 1:1.6, 1:1.8, denoted as: disilazane:(Si-Cl+B-Cl)=1:1~1:2.

[0066] It should be noted that the reaction equations involved in step (3) are as follows:

[0067]

[0068] As shown in the above equations, B forms a branched borazane structure, existing as the BNH structure. The cycloborazane structure endows the PBSZ precursor with good flexibility at high temperatures, while the branched borazane structure endows the PBSZ precursor with good temperature resistance. This invention allows for the control of the B2NH / BNH ratio through a batch-feed reaction method.

[0069] Specifically, in step (4), the temperature is raised to 130-150℃ at a rate of 5-30℃ / h and held for 1-8 hours.

[0070] It should be noted that the purpose of the first heating and distillation in step (4) is to remove the solvent, the byproduct monochlorosilane and unreacted disilazine. After no more distillate is released, the temperature is gradually increased to a certain level and held at that temperature for a certain period of time to obtain the reaction intermediate.

[0071] Specifically, in step (4), the temperature of the second heating is 160-220℃, for example, 165℃, 170℃, 175℃, 180℃, 185℃, 190℃, 195℃, 200℃, 205℃, 210℃, 215℃, and the heat preservation reaction time is 2-8h, for example, 2.5h, 3.0h, 3.5h, 4.0h, 4.5h, 5.0h, 5.5h, 6.0h, 6.5h, 7.0h, 7.5h.

[0072] It should be noted that when the temperature is below 160°C, the synthesized product contains more low molecular weight products, and the coating made using the polyborosilicate precursor will have poor strength and toughness. When the temperature is above 220°C, the viscosity and crosslinking degree of the polyborosilicate precursor are difficult to control, and gelation is likely to occur.

[0073] Specifically, in step (4), the temperature of the vacuum treatment is 80 to 200°C, for example, 100°C, 120°C, 140°C, 160°C, 180°C, the vacuum degree is 10 to 100Pa, for example, 20Pa, 30Pa, 40Pa, 50Pa, 60Pa, 70Pa, 80Pa, 90Pa, and the vacuum treatment time is 2 to 6 hours, for example, 2.5 hours, 3.0 hours, 3.5 hours, 4.0 hours, 4.5 hours, 5.0 hours, 5.5 hours.

[0074] It should be noted that if the vacuum treatment temperature is too low, the synthesized product will contain more low molecular weight products, resulting in coatings made from polyborosilazane precursors with poor strength and toughness. If the temperature is too high, the viscosity and crosslinking degree of the polyborosilazane precursor are difficult to control, easily leading to gelation. Low vacuum levels result in incomplete removal of small molecules, while excessively high vacuum levels lead to a more vigorous polycondensation reaction, making it impossible to control the state of the reaction products.

[0075] Specifically, in step (4), the ratio of B2NH to BNH in the polyborosilazane precursor is 1:0.5 to 1:3, for example, 1:0.7, 1:0.9, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2.0, 1:2.2, 1:2.4, 1:2.6, 1:2.8, preferably 1:1 to 1:1.8, and the number average molecular weight is 800 to 1500 g / mol.

[0076] It should be noted that the B2NH / BNH ratio in the polyborosilicate precursor of this invention is determined by 1H NMR spectroscopy (NMR spectroscopy). 1 The area ratio of the B2NH peak located between 4.2 and 2.6 ppm to the BNH peak located between 2.6 and 1.2 ppm is determined by ¹H NMR.

[0077] Specifically, in step (4), the number-average molecular weight of the polyborosilicate precursor is 600-1500 g / mol, for example, 700 g / mol, 800 g / mol, 900 g / mol, 1000 g / mol, 1100 g / mol, 1200 g / mol, 1300 g / mol, 1400 g / mol, preferably 800-1200 g / mol.

[0078] A specific embodiment of the present invention discloses a polyborosilicate precursor prepared by the above method with a controllable ratio of B2NH and BNH.

[0079] Another specific embodiment of the present invention discloses a high-temperature resistant and high-toughness coating prepared using the above-mentioned polyborosilicate precursor with controllable B2NH and BNH ratio.

[0080] Specifically, the raw materials for the coating, by mass percentage, include: a polyborosilazane precursor: 1-20% (e.g., 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%), a solvent: 80-98% (e.g., 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%), and a catalyst: 0.1-3% (0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8%).

[0081] Specifically, the solvents include one or more of the following: alkane solvents, ether solvents, ketone solvents, ester solvents, and benzene derivative solvents.

[0082] Preferably, the alkane solvent includes one or more of n-hexane, n-octane, n-decane, chloroform, dichloromethane, and dichloroethylene;

[0083] The ether solvents mentioned include one or more of diethyl ether and dibutyl ether;

[0084] The ketone solvents mentioned include one or more of acetone, methyl ethyl ketone, cyclohexanone, and isophorone;

[0085] The ester solvents mentioned include one or more of ethyl acetate, propyl acetate, and butyl acetate;

[0086] The benzene derivative solvents include one or more of toluene, m-xylene, p-xylene, o-xylene, and chlorobenzene.

[0087] Specifically, the catalysts include peroxide catalysts and / or platinum metal catalysts.

[0088] Preferably, the peroxide catalyst includes one or more of benzoyl peroxide (BPO), dicumyl peroxide (DCP), and cumyl hydroperoxide (CHP).

[0089] The platinum metal catalysts mentioned include chloroplatinic acid and / or cassette catalysts.

[0090] Specifically, the coating has a flexibility of ≤2mm at room temperature, preferably 1-2mm, and a flexibility of ≤3mm at high temperature (400℃, 1h), preferably 2-3mm.

[0091] Another specific embodiment of the present invention discloses a method for preparing the coating, comprising the following steps:

[0092] (a) Weigh each ingredient according to the proportions, mix them, and form a solution;

[0093] (b) The solution is coated and cured to obtain the coating.

[0094] Specifically, in step (b), the coating includes one or more of spraying, spin coating, dip coating, or wiping coating.

[0095] Specifically, in step (b), the curing temperature is 100–300°C (e.g., 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C, 280°C), preferably 150–270°C, and the curing time is 5–50 h (e.g., 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h), preferably 10–30 h.

[0096] The technical solution of the present invention will be further explained below with reference to specific embodiments. All raw materials used in the present invention are commercially available products or prepared by existing methods.

[0097] Example 1

[0098] This embodiment describes a method for synthesizing a polyborosilazane precursor with a controllable ratio of B2NH and BNH, comprising the following steps:

[0099] (1) Under a nitrogen atmosphere, n-hexane was added to the reactor, the temperature was lowered to -10℃, boron trichloride was added, and the mixture was stirred evenly. Hexamethyldisilazane was added under heat preservation conditions, and the reaction was carried out for 6 hours to obtain the first product intermediate. The mass ratio of n-hexane to the total mass of boron trichloride and methylvinyldichlorosilane in step (2) was 3:1. The first product intermediate was heated to 20℃ and the reaction was continued for 4 hours to obtain the first product.

[0100] (2) Methylvinyldichlorosilane and hexamethyldisilazane are added sequentially to the first product, with a molar ratio of 1:1 between methylvinyldichlorosilane and hexamethyldisilazane. The reaction is carried out for 3 hours to obtain the second product.

[0101] (3) Cool the second product to -10℃, add boron trichloride, stir for 1 hour, add hexamethyldisilazane, and ensure that the temperature inside the container is always kept at -10℃ during the addition process to react for 4 hours to obtain the third product.

[0102] In step (1), the molar ratio of boron trichloride in step (3) is 1:0.5, the total molar ratio of boron trichloride in step (1) and step (3) to the molar ratio of chlorosilane in step (2) is 1:1, and in steps (1) to (3), hexamethyldisilazane: (Si-Cl+B-Cl)=1:1;

[0103] (4) The third product is heated and distilled for the first time at a heating rate of 5℃ / h, heated to 150℃ and held for 1h, and then the system is slowly heated to 220℃ and held for 2h to obtain a reaction intermediate. The intermediate is subjected to vacuum treatment at 200℃ and 100Pa for 2h to remove small molecule byproducts. The system is then cooled to room temperature to obtain the polyborosilicate precursor with controllable B2NH and BNH ratio.

[0104] Example 2

[0105] This embodiment describes a method for synthesizing a polyborosilazane precursor with a controllable ratio of B2NH and BNH, comprising the following steps:

[0106] (1) Under a nitrogen atmosphere, toluene was added to the reactor, the temperature was lowered to -20°C, boron trichloride was added, and the mixture was stirred evenly. Tetramethyldivinyldisilazane was added under heat preservation conditions, and the reaction was carried out for 8 hours to obtain the first product intermediate. The molar ratio of tetramethyldivinyldisilazane to boron trichloride was 3.1:1, and the mass ratio of toluene to the total mass of boron trichloride and methyldichlorosilane in step (2) was 2:1. The first product intermediate was heated to 30°C and the reaction was continued for 6 hours to obtain the first product.

[0107] (2) Methyldichlorosilane and tetramethyldivinyldisilazane are added sequentially to the first product, with a molar ratio of methyldichlorosilane to tetramethyldivinyldisilazane of 1:1.5. The reaction is carried out for 4 hours to obtain the second product.

[0108] (3) Cool the second product to -20°C, add boron trichloride, stir for 2 hours, add tetramethyldivinyldisilazane, and ensure that the temperature inside the container is kept at -20°C throughout the addition process for 6 hours to obtain the third product.

[0109] In step (1), the molar ratio of boron trichloride in step (3) is 1:1.75, the total molar ratio of boron trichloride in step (1) and step (3) to the molar ratio of chlorosilane in step (2) is 1:2.5, and in steps (1) to (3), tetramethyldivinyldisilazane: (Si-Cl+B-Cl)=1:1.5;

[0110] (4) The third product is heated and distilled for the first time at a heating rate of 30℃ / h, heated to 130℃ and held for 8h, and then the system is slowly heated to 160℃ and held for 8h to obtain a reaction intermediate. The intermediate is subjected to vacuum treatment at 140℃ and 10Pa for 6h to remove small molecule byproducts. The system is then cooled to room temperature to obtain the polyborosilicate precursor with controllable B2NH and BNH ratio.

[0111] Example 3

[0112] This embodiment describes a method for synthesizing a polyborosilazane precursor with a controllable ratio of B2NH and BNH, comprising the following steps:

[0113] (1) Tetrahydrofuran was added to the reactor under a nitrogen atmosphere, the temperature was lowered to -15°C, boron trichloride was added, and the mixture was stirred evenly. Tetramethyldivinyldisilazane was added under heat preservation conditions, and the reaction was carried out for 7 hours to obtain the first product intermediate. The molar ratio of tetramethyldivinyldisilazane to boron trichloride was 3.2:1, and the mass ratio of tetrahydrofuran to the total mass of boron trichloride and methyldichlorosilane in step (2) was 1:1. The first product intermediate was heated to 25°C and the reaction was continued for 5 hours to obtain the first product.

[0114] (2) Methyldichlorosilane and tetramethyldivinyldisilazane are added sequentially to the first product, with a molar ratio of methyldichlorosilane to tetramethyldivinyldisilazane of 1:2, and the reaction is carried out for 3.5 h to obtain the second product;

[0115] (3) Cool the second product to -15℃, add boron trichloride, stir for 1.5h, add tetramethyldivinyldisilazane, and ensure that the temperature inside the container is kept at -15℃ throughout the addition process for 8h to obtain the third product.

[0116] In step (1), the molar ratio of boron trichloride in step (3) is 1:3, the total molar ratio of boron trichloride in step (1) and step (3) to the molar ratio of chlorosilane in step (2) is 1:4, and in steps (1) to (3), tetramethyldivinyldisilazane: (Si-Cl+B-Cl)=1:2;

[0117] (4) The third product is heated and distilled for the first time at a heating rate of 10℃ / h, heated to 140℃ and held for 5h, and then the system is slowly heated to 200℃ and held for 8h to obtain a reaction intermediate. The intermediate is subjected to vacuum treatment at 200℃ and 50Pa for 4h to remove small molecule byproducts. The system is then cooled to room temperature to obtain the polyborosilicate precursor with controllable B2NH and BNH ratio.

[0118] Example 4

[0119] This embodiment describes a method for synthesizing a polyborosilazane precursor with a controllable ratio of B2NH and BNH, comprising the following steps:

[0120] (1) Under a nitrogen atmosphere, n-hexane was added to the reactor, the temperature was lowered to -20°C, boron trichloride was added, and the mixture was stirred evenly. Hexamethyldisilazane was added under heat preservation conditions, and the reaction was carried out for 6 hours to obtain the first product intermediate. The molar ratio of disilazane to boron trichloride was 3:1, and the mass ratio of n-hexane to the total mass of boron trichloride and methyldichlorosilane in step (2) was 2.5:1. The first product intermediate was heated to 30°C and the reaction was continued for 4 hours to obtain the first product.

[0121] (2) Methyldichlorosilane and hexamethyldisilazane are added sequentially to the first product, with a molar ratio of methyldichlorosilane to hexamethyldisilazane of 1:1.3, and the reaction is carried out for 3 hours to obtain the second product;

[0122] (3) Cool the second product to -20°C, add boron trichloride, stir for 2 hours, add hexamethyldisilazane, and ensure that the temperature inside the container is always kept at -20°C during the addition process to react for 5 hours to obtain the third product.

[0123] In step (1), the molar ratio of boron trichloride in step (3) is 1:1, the total molar ratio of boron trichloride in step (1) and step (3) to the molar ratio of chlorosilane in step (2) is 1:2, and in steps (1) to (3), hexamethyldisilazane: (Si-Cl+B-Cl)=1:1.3;

[0124] (4) The third product is heated and distilled for the first time at a heating rate of 20℃ / h, heated to 150℃ and held for 5h, and then the system is slowly heated to 180℃ and held for 6h to obtain a reaction intermediate. The intermediate is subjected to vacuum treatment at 80℃ and 50Pa for 4h to remove small molecule byproducts. The system is then cooled to room temperature to obtain the polyborosilicate precursor with controllable B2NH and BNH ratio.

[0125] Comparative Example 1

[0126] The method for synthesizing a polyborosilicate precursor with controllable B2NH and BNH ratio in this comparative example is the same as that in Example 1, the mass ratio of n-hexane to boron trichloride and the total mass ratio of methylvinyldichlorosilane in step (2) is 4:1, and the molar ratio of hexamethyldisilazane to boron trichloride is 3.5:1.

[0127] Comparative Example 2

[0128] The synthesis method of the B2NH and BNH ratio controllable polyborosilicate precursor in this comparative example is the same as that in Example 1, except that in step (2), the molar ratio of chlorosilane and hexamethyldisilazane is 1:3.

[0129] Comparative Example 3

[0130] The synthesis method of the polyborosilicate precursor with controllable B2NH and BNH ratio in this comparative example is the same as that in Example 1, except that the molar ratio of boron trichloride in step (1) to boron trichloride in step (3) is 1:4.

[0131] Comparative Example 4

[0132] The method for synthesizing a polyborosilicate precursor with controllable B2NH and BNH ratio in this comparative example is the same as that in Example 1, except that the total molar ratio of boron trichloride in step (1) and step (3) to the molar ratio of chlorosilane in step (2) is 1:5.

[0133] Comparative Example 5

[0134] The synthesis method of the polyborosilicate precursor with controllable B2NH and BNH ratio in this comparative example is the same as that in Example 1, except that hexamethyldisilazane:(Si-Cl+B-Cl)=1:3.

[0135] Application Example 1

[0136] This application example provides a high-temperature resistant and high-toughness coating. The coating materials include 1g of the polyborosilazane precursor prepared in Example 1 and 99g of butyl acetate, which are prepared into a 1% solution. Using tinplate as the substrate, the coating is applied to the tinplate by dip coating. The tinplate is immersed in the solution for 10 seconds, then removed and left to air dry at room temperature for 10 minutes. Then, it is heated to 300°C in an oven and cured for 5 hours.

[0137] Application Example 2

[0138] The coating raw materials and preparation method in this application example are the same as those in application example 1. The difference is that the polyborosilicate precursor prepared in example 1 is replaced with the polyborosilicate precursor prepared in example 2.

[0139] Application Example 3

[0140] The coating raw materials and preparation method in this application example are the same as those in application example 1. The difference is that the polyborosilicate precursor prepared in example 1 is replaced with the polyborosilicate precursor prepared in example 3.

[0141] Application Example 4

[0142] The coating raw materials and preparation method in this application example are the same as those in application example 1. The difference is that the polyborosilicate precursor prepared in example 1 is replaced with the polyborosilicate precursor prepared in example 4.

[0143] Application Example 5

[0144] This application example provides a high-temperature resistant and high-toughness coating. The raw materials for the coating include 20g of the polyborosilazane precursor prepared in Example 1, 78g of xylene, and 2g of DCP. Using tinplate as the substrate, the coating is applied to the tinplate by spraying, left to dry at room temperature for 15 minutes, and then heated to 150°C in an oven for 30 hours to cure.

[0145] Application Example 6

[0146] This application example provides a high-temperature resistant and high-toughness coating. The raw materials for the coating include 5g of the polyborosilazane precursor prepared in Example 2, 94.9g of petroleum ether, and 0.1g of BPO. Using tinplate as the substrate, the coating is applied to the tinplate by spin coating, left to dry at room temperature for 5 minutes, and then heated to 270°C in an oven for 10 hours to cure.

[0147] Application Example 7

[0148] This application example presents a high-temperature resistant and high-toughness coating. The coating materials include 10g of the polyborosilazane precursor prepared in Example 3, 89g of dibutyl ether, and 1g of BPO. Using tinplate as a substrate, the coating is applied to the tinplate by spin coating, allowed to dry at room temperature for 5 minutes, and then heated to 200°C in an oven for 30 hours for curing.

[0149] Application Example 8

[0150] This application example presents a high-temperature resistant and high-toughness coating. The coating materials include 15g of the polyborosilazane precursor prepared in Example 4, 82g of methyl ethyl ketone (MEK), and 3g of CHP. Using tinplate as a substrate, the coating is applied by brushing, allowed to air dry at room temperature for 8 minutes, and then cured in an oven at 220°C for 15 hours.

[0151] Application Example 9

[0152] This application example provides a high-temperature resistant and high-toughness coating. The raw materials and preparation method are the same as those in application example 1. The difference is that the polyborosilazane precursor prepared in example 1 is replaced with the polyborosilazane precursor prepared in comparative example 1.

[0153] Application Example 10

[0154] This application example provides a high-temperature resistant and high-toughness coating. The raw materials and preparation method are the same as those in application example 1. The difference is that the polyborosilicate precursor prepared in example 1 is replaced with the polyborosilicate precursor prepared in comparative example 2.

[0155] Application Example 11

[0156] This application example provides a high-temperature resistant and high-toughness coating. The raw materials and preparation method are the same as those in application example 1. The difference is that the polyborosilicate precursor prepared in example 1 is replaced with the polyborosilicate precursor prepared in comparative example 3.

[0157] Application Example 12

[0158] This application example provides a high-temperature resistant and high-toughness coating. The raw materials and preparation method are the same as those in application example 1. The difference is that the polyborosilicate precursor prepared in example 1 is replaced with the polyborosilicate precursor prepared in comparative example 4.

[0159] Application Example 13

[0160] This application example provides a high-temperature resistant and high-toughness coating. The raw materials and preparation method are the same as those in application example 1. The difference is that the polyborosilazane precursor prepared in example 1 is replaced with the polyborosilazane precursor prepared in comparative example 5.

[0161] Experimental Example 1

[0162] The number-average molecular weight and the ratio of B2NH to BNH of the polyborosilicate precursors prepared in Examples 1-4 and Comparative Examples 1-5 were tested respectively, and the results are shown in Table 1.

[0163] Table 1

[0164] Group Number-average molecular weight (g / mol) <![CDATA[B2NH / BNH ratio]]> Example 1 1450 1:0.52 Example 2 893 1:1.83 Example 3 1218 1:2.87 Example 4 809 1:0.98 Comparative Example 1 1732 1:0.38 Comparative Example 2 518 1:0.41 Comparative Example 3 1018 1:3.98 Comparative Example 4 1657 1:0.86 Comparative Example 5 gel Unable to determine

[0165] Experimental Example 2

[0166] The high-temperature resistant and high-toughness coatings prepared in Application Examples 1-13 were tested for flexibility according to the national standard GB / T 1731-2020. The flexibility at room temperature is shown in Table 2. The coatings were treated in a muffle furnace at 400℃ for 1 hour and then cooled to room temperature. The flexibility (i.e., high-temperature flexibility) of the coatings was measured and is shown in Table 2.

[0167] Table 2

[0168]

[0169]

[0170] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for synthesizing a polyborosilicate precursor with a controllable ratio of B2NH and BNH, characterized in that, Includes the following steps: (1) Under an inert atmosphere, an organic solvent is added to the reactor, the temperature is lowered, boron trichloride is added, the mixture is mixed evenly, and disilazane is added under heat preservation conditions to carry out the reaction. After the temperature is raised, the reaction continues to obtain the first product. (2) Chlorosilane and disilazane are added sequentially to the first product and reacted to obtain the second product; (3) Cool the second product, add boron trichloride, stir, add disilazine, and react to obtain the third product; (4) The third product is heated and distilled for the first time, and then heated and reacted for the second time to obtain a reaction intermediate. The intermediate is then treated under vacuum and cooled to room temperature to obtain the polyborosilicate precursor with a controllable ratio of B2NH and BNH.

2. The synthesis method according to claim 1, characterized in that, In step (1), the organic solvent includes one or more of n-hexane, toluene, xylene, and tetrahydrofuran; And / or, the molar ratio of disilazane to boron trichloride is 3 to 3.2:

1.

3. The synthesis method according to claim 1, characterized in that, In step (1), the temperature is lowered to -10 to -20℃; And / or, the temperature for the heat preservation reaction is -10 to -20℃, and the reaction time is 6 to 8 hours; And / or, raise the temperature to 20–30°C and continue the reaction for 4–6 hours.

4. The synthesis method according to any one of claims 1-3, characterized in that, In step (2), the molar ratio of chlorosilane and disilazine is 1:1 to 1:

2.

5. The synthesis method according to any one of claims 1-3, characterized in that, The mass ratio of the organic solvent in step (1) to the total mass of boron trichloride and chlorosilane in step (2) is 3:1 to 1:

1.

6. The synthesis method according to claim 1, characterized in that, In step (3), the temperature is lowered to -10 to -20°C, the stirring time is 1 to 2 hours, and the reaction time is 4 to 8 hours.

7. The synthesis method according to claim 1, characterized in that, The molar ratio of boron trichloride in step (1) to boron trichloride in step (3) is 1:0.5 to 1:3; And / or, in steps (1) to (3), the ratio of the total mole of disilazane to the sum of the moles of Si-Cl groups in chlorosilane and the moles of B-Cl groups in boron trichloride added in the whole reaction is 1:1 to 1:

2.

8. The synthesis method according to claim 1, characterized in that, In step (4), the temperature is raised to 130-150℃ at a rate of 5-30℃ / h and held for 1-8 hours; And / or, the temperature for the second heating is 160–220℃, and the holding time for the reaction is 2–8 hours.

9. A polyborosilicate precursor with a controllable ratio of B2NH and BNH prepared by the synthesis method according to any one of claims 1-8, characterized in that, The ratio of B2NH to BNH in the polyborosilazane precursor is 1:0.5 to 1:

3.

10. The application of the polyborosilicate precursor of claim 9 in the preparation of a high-temperature resistant and high-toughness coating.

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