Method and system for rapidly and efficiently preparing polysilazane

Abstract

The invention relates to a method and a system for rapidly and efficiently preparing polysilazane, belongs to the technical field of macromolecules, and is used for solving one of the problems of long ammonolysis time, low synthesis efficiency, high production cost and the like in the existing method. According to the method disclosed by the invention, the evaporation amount of liquid ammonia, the suction amount of ammonia gas and the spraying speed of the chlorosilane and the organic solvent in the spraying mixing device are controlled, so that the chlorosilane can be in full contact with the ammonia gas, the ammonolysis time of the chlorosilane is shortened, the synthesis efficiency of the silazane is improved, and the production cost of the polysilazane is reduced; the method can be used for large-scale production.

Description

Technical Field

[0001] The present invention relates to the field of polymer technology, and in particular to a method and system for rapidly and efficiently preparing polysilazane. Background Art

[0002] Polysilazanes are a class of polymeric materials with a main chain primarily composed of Si-N bonds and side chains containing organic groups or H. At high temperatures, they transform into SiC / Si3N4 or Si3N4 ceramics with excellent heat resistance and oxidation resistance. They are widely used in the preparation of ceramic-based composites, high-temperature-resistant adhesives, coatings, and fibers.

[0003] Currently, polysilazanes are widely prepared by passing ammonia gas into a chlorosilane solution (bubbling ammonolysis method). However, due to insufficient contact between chlorosilane and ammonia gas, this method results in a long ammonolysis time for the chlorosilane, which affects the synthesis efficiency of silazane and increases the production cost of polysilazanes, hindering their large-scale use. Summary of the Invention

[0004] In view of the above analysis, the present invention aims to provide a method and system for quickly and efficiently preparing polysilazane, so as to solve at least one of the problems of the existing method, such as long aminolysis time, low synthesis efficiency, and high production cost.

[0005] In a first aspect, the present invention provides a method for rapidly and efficiently preparing polysilazane, comprising the following steps:

[0006] (1) evaporating liquid ammonia at a rate of 10 to 100 L / min, sucking ammonia gas into a jet mixing device at a rate of 10 to 100 L / min, and simultaneously inputting a mixed liquid of chlorosilane and an organic solvent in a raw material mixing tank into the jet mixing device, spraying and mixing the mixture of ammonia gas, chlorosilane, and organic solvent uniformly in the jet mixing device, and spraying the chlorosilane and organic solvent in the jet mixing device at a rate of 2 to 30 L / min, thereby obtaining a mixture A;

[0007] (2) the mixture A is further mixed and reacted in a static mixer to obtain a mixture B, which is then fed into a raw material mixing tank and then sprayed into a spray mixing device to repeat step (1) until the pH value of the entire reaction system reaches ≥8, thereby obtaining a crude product;

[0008] (3) subjecting the crude product to solid-liquid separation to obtain a liquid, and subjecting the liquid to reduced pressure distillation to obtain the polysilazane.

[0009] Furthermore, in step (1), the molar ratio of the chlorine element in the injection mixing device to the inhaled ammonia gas is controlled to be 1:0.02-0.5.

[0010] Furthermore, in step (1), the organic solvent is one or more of C5-C10 alkanes, petroleum ether, ethers, tetrahydrofuran, aromatic hydrocarbons, acetone, esters or dichloromethane.

[0011] Furthermore, in step (1), the volume ratio of the organic solvent to the chlorosilane is 3:1 to 6:1.

[0012] Furthermore, in step (3), the distillation temperature is 40-80° C. and the vacuum degree is 50-1000 Pa.

[0013] In a second aspect, the present invention provides a jet mixing device for the above-mentioned polysilazane preparation method, comprising a receiving chamber, a mixing section and a diffusion section connected in sequence, wherein a nozzle is provided in the receiving chamber so that the fluid in the receiving chamber is sprayed into the mixing section, a fluid inlet is provided at one end of the receiving chamber, an ammonia inlet is provided at the other end of the receiving chamber, and a fluid outlet is provided in the diffusion section.

[0014] Furthermore, the diameter of the diffusion section gradually increases along the flow direction of the fluid.

[0015] Furthermore, the diameters of the fluid inlet and the fluid outlet are the same, the diameter of the nozzle is 4 to 12 mm, the diameter of the mixing section is 7 to 20 mm, the ratio of the diameter of the mixing section to the diameter of the nozzle is 1.7 to 1.8, and the length of the mixing section is 10 to 50 mm.

[0016] Furthermore, the diffusion angle of the diffusion section is 6° to 16°, and the ratio of the mouth-throat distance to the nozzle diameter is 1 to 3.5.

[0017] In a third aspect, the present invention provides a system for preparing the above-mentioned polysilazane, comprising a liquid ammonia tank, a jet mixing device, a static mixer, a reaction storage tank, a filtration device and a distillation kettle connected in sequence, wherein the jet mixing device is also connected to a raw material mixing tank.

[0018] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0019] (1) In the method of the present invention, the amount of liquid ammonia evaporation and the amount of ammonia gas inhaled, as well as the injection speed of chlorosilane and organic solvent in the injection mixing device, can make chlorosilane fully contact with ammonia gas, reduce the ammonolysis time of chlorosilane, and improve the synthesis efficiency of silazane. The ammonolysis time of chlorosilane is 1.786-1.825% of the time consumed by the bubbling gas ammonia ammonolysis method, thereby reducing the production cost of polysilazane. Moreover, the method of the present invention can be produced on a large scale.

[0020] (2) The present invention utilizes a jet mixing device to form turbulent or turbulent fluids such as chlorosilane, organic solvent, and ammonia, so that the reactants are fully contacted in the jet tube and the reaction storage tank, thereby improving the mass transfer efficiency during the ammonolysis of chlorosilane, shortening the ammonolysis reaction time, and achieving efficient preparation of silazane. The reactants are mixed by the jet mixing device, and the jet reaction can be regarded as a contact reaction process between tiny droplets and the gas phase, which is called a micro-reaction process. The series combination of numerous micro-reactions promotes the rapid and efficient synthesis of silazane. The jet cycle reaction makes full use of ammonia, reduces the amount of ammonia used, and greatly reduces the amount of ammonia discharged.

[0021] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be described in the following description, and some advantages will become apparent from the description or be learned through practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0023] Figure 1 Schematic diagram of the structure of the jet mixing device of the present invention;

[0024] Figure 2 Schematic diagram of the system for preparing polysilazane according to the present invention.

[0025] Reference numerals:

[0026] 1-jet mixing device, 11-fluid inlet, 111-ammonia gas inlet, 112-nozzle, 12-receiving chamber, 13-mixing section, 14-diffusion section, 15-fluid outlet, 2-liquid ammonia tank, 3-static mixer, 4-reaction storage tank, 5-raw material mixing tank, 6-filtration device, 7-still kettle, 8-input pump, 9-check valve. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0028] A specific embodiment of the present invention discloses a method for rapidly and efficiently preparing polysilazane, comprising the following steps:

[0029] (1) evaporating liquid ammonia at a rate of 10 to 100 L / min, sucking ammonia gas into a jet mixing device at a rate of 10 to 100 L / min, and simultaneously spraying a mixture of chlorosilane and an organic solvent in a raw material mixing tank into the jet mixing device, uniformly mixing the ammonia gas with the mixture of chlorosilane and the organic solvent in the jet mixing device, and spraying the chlorosilane and the organic solvent in the jet mixing device at a rate of 2 to 30 L / min, to obtain a mixture A;

[0030] (2) the mixture A is further mixed and reacted in a static mixer to obtain a mixture B, which is then fed into a raw material mixing tank and then sprayed into a spray mixing device to repeat step (1) until the pH value of the entire reaction system reaches ≥8, thereby obtaining a crude product;

[0031] (3) subjecting the crude product to solid-liquid separation to obtain a liquid, and subjecting the liquid to reduced pressure distillation to obtain the polysilazane.

[0032] Compared with the prior art, the method of the present invention controls the amount of liquid ammonia evaporation and the amount of ammonia gas inhaled, as well as the injection speed of chlorosilane and the organic solvent in the injection mixing device, so that the chlorosilane and the ammonia gas are fully contacted, and the ammonolysis time of the chlorosilane is reduced. The ammonolysis time of the chlorosilane is 1.786 to 1.825% of the time consumed by the bubbling gas ammonia ammonolysis method. Therefore, the synthesis efficiency of silazane is improved, the production cost of polysilazane is reduced, and the method of the present invention can be used for large-scale production.

[0033] Secondly, the present invention utilizes a jet mixing device to form turbulent and turbulent fluids such as chlorosilane, organic solvent, and ammonia, so that the reactants are fully contacted in the reaction storage tank, thereby improving the mass transfer efficiency during the ammonolysis of chlorosilane, shortening the ammonolysis reaction time, and achieving efficient preparation of silazane. The reactants are mixed by the jet mixing device, and the jet reaction can be regarded as a contact reaction process between tiny droplets and the gas phase, referred to as a micro-reaction process. The series combination of numerous micro-reactions promotes the rapid and efficient synthesis of silazane. The jet cycle reaction fully utilizes the ammonia, reduces the amount of ammonia used, and greatly reduces ammonia emissions.

[0034] It should be noted that in the present invention, the injection speed of the chlorosilane and organic solvent in the jet mixing device is too low, making it difficult for a large amount of ammonia to fully mix and react with the chlorosilane. A large amount of ammonia remains inside the jet mixing device, causing the local pressure of the jet mixing device to increase, posing a hidden danger to production. If the injection speed is too high, the amount of ammonia that needs to be inhaled increases accordingly, the heat release of the reaction increases, and the heat generated cannot be removed in time inside the jet mixing device, causing a significant increase in the pressure of the reaction system, creating a safety hazard. Therefore, in the present invention, the injection speed of the chlorosilane and organic solvent in the jet mixing device is selected to be 2 to 30 L / min.

[0035] In a specific embodiment, in step (1), the entire reaction is carried out in an inert gas, and the inert gas is nitrogen or argon.

[0036] It should be noted that the chlorosilanes described in the present invention are all commercially available products, for example, the structural formula is R 1 m R 2 n SiCl x , where R 1 and R 2 They are H, methyl, vinyl, ethyl, ethynyl, allyl, phenyl, trifluoropropyl and other groups, which can be the same or different, m+n=1 or 2, m or n can be 0, x≥2, and m+n+x=4.

[0037] The chlorosilane is specifically but not limited to the following chlorosilanes, dichlorosilane, trichlorosilane, tetrachlorosilane, dimethyldichlorosilane, methylhydrogendichlorosilane, methylphenyldichlorosilane, methyltrichlorosilane, methylvinyldichlorosilane, ethynyltrichlorosilane, trifluoropropylmethyldichlorosilane, diphenyldichlorosilane, phenyltrichlorosilane, ethyltrichlorosilane, ethyldichlorosilane, diethyldichlorosilane, vinyltrichlorosilane, etc. One or more.

[0038] In a specific embodiment, in step (1), the organic solvent is one or more of C5-C10 alkanes, petroleum ether, ethers, tetrahydrofuran, aromatic hydrocarbons, acetone, esters or dichloromethane.

[0039] In a specific embodiment, in step (1), the volume ratio of the organic solvent to the chlorosilane is 3:1 to 6:1.

[0040] In a specific embodiment, in step (1), the molar ratio of the chlorine element in the injection mixing device to the inhaled ammonia gas is 1:0.02-0.5.

[0041] It should be noted that the injection rate of chlorosilane and organic solvent in the injection mixing device is 2 to 30 L / min, and the above injection rate is regulated by the feed rate of the raw material delivery pump 8 .

[0042] Specifically, in step (2), the mixture after the mixing reaction is again subjected to multiple cycle reactions through a jet mixing device. During the cycle, if there are a lot of solid by-products that hinder the progress of the jet reaction, it can be preliminarily filtered through a tank filter device, and the filtrate then enters the reaction system.

[0043] In a specific embodiment, in step (3), the distillation temperature is 40-80° C. and the vacuum degree is 50-1000 Pa.

[0044] Specifically, in step (3), the solid-liquid separation device includes a separation device such as a filter press and a centrifuge.

[0045] Specifically, in step (3), the reduced pressure distillation is carried out until no fraction is distilled out from the outlet of the condenser, at which time polysilazane is obtained.

[0046] The polysilazane of the present invention may be liquid or solid. The melting point of the solid polysilazane is 60 to 180° C., and the viscosity of the liquid polysilazane is 50 to 100,000 cp.

[0047] The method of the present invention can be used to prepare modified silazane polymers, including but not limited to the following polymers: polyborosilazanes, aluminum-containing polysilazanes, polycarbosilazanes, and zirconium-containing silazanes. It can also be used to prepare alkoxy polysilazanes and polysilazanes containing heteroelements, including but not limited to Al, B, Ti, Zr, and Hf.

[0048] Another specific embodiment of the present invention is as follows Figure 1 As shown, a jet mixing device 1 is disclosed, comprising a receiving chamber 12, a mixing section 13 and a diffusion section 14 connected in sequence, wherein a nozzle 112 is provided in the receiving chamber 12 so that the fluid in the receiving chamber 12 is sprayed into the mixing section 13, a fluid inlet 11 is provided at one end of the receiving chamber 12, an ammonia inlet 111 is provided at the other end of the receiving chamber 12, and a fluid outlet 15 is provided in the diffusion section 14.

[0049] In a specific embodiment, the diameter of the diffuser section 14 gradually increases along the fluid flow direction.

[0050] The jet mixing device 1 of the present invention forms a turbulent flow between the mixture of chlorosilane and solvent and ammonia, a turbulent flow and other fluids, so that the reactants are fully contacted within the reaction device, thereby improving the mass transfer efficiency during the ammonolysis of chlorosilane, shortening the ammonolysis reaction time, and achieving efficient preparation of silochloroalkane. In the present invention, the existing kettle reaction is replaced by a jet cycle reaction. The jet reaction can be regarded as a contact reaction process between tiny droplets and the gas phase, referred to as a microreaction process. The series combination of numerous microreactions promotes the rapid and efficient synthesis of silochloroalkane. The jet cycle reaction fully utilizes the ammonia, reduces the amount of ammonia used, and greatly reduces ammonia emissions.

[0051] It should be noted that the jet mixing device 1 of the present invention is a device for mixing two fluids with different pressures to exchange energy and form a mixed fluid. The mixed fluid can form a turbulent flow state.

[0052] In a specific embodiment, the diameters of the fluid inlet 11 and the fluid outlet 15 are the same, for example, DN20, DN25, DN32, DN40 or DN50.

[0053] In a specific embodiment, the diameter of the ammonia inlet 111 is DN20 (G1 / 2).

[0054] In a specific embodiment, the diameter of the nozzle 112 is 4 to 12 mm, the diameter of the mixing section 13 is 7 to 20 mm, the ratio of the diameter of the mixing section 13 to the diameter of the nozzle 112 is 1.7 to 1.8, and the length of the mixing section 13 is 10 to 50 mm.

[0055] Specifically, the diffusion angle of the diffusion section 14 (the angle between the central axis and the hypotenuse) is 6° to 16°, and the ratio of the mouth-throat distance (the position from the nozzle 112 mouth to the connection between the receiving chamber 12 and the mixing section 13) to the diameter of the nozzle 112 is 1 to 3.5.

[0056] It should be noted that the mouth-throat distance is adjusted according to the diameter of the nozzle 112. The smaller the diameter of the nozzle 112, the larger the mouth-throat distance. By adjusting the ratio of the mouth-throat distance to the diameter of the nozzle 112, the receiving chamber 12 can generate negative pressure, and the negative pressure range is -0.001 to -0.0098 MPa.

[0057] Specifically, the entire reaction system is carried out under the protection of an inert atmosphere, and the aminolysis reaction is carried out at a temperature of -25 to 35°C.

[0058] The mixing section 13 and the diffusion section 14 are provided with a sandwich structure, and the sandwich structure is connected to a high and low temperature circulation device to achieve control of the reaction temperature.

[0059] Another specific embodiment of the present invention is as follows Figure 2 As shown, a system for preparing polysilazane is disclosed, which includes a liquid ammonia tank 2, a spray mixing device 1, a static mixer 3, a reaction storage tank 4, a filtering device 6 and a distillation kettle 7 connected in sequence, and the spray mixing device 1 is also connected to a raw material mixing tank 5.

[0060] It should be noted that after the chlorosilane and the organic solvent are mixed in the raw material mixing tank 5, they are input into the jet mixing device 1 through the fluid inlet 11 by the delivery pump 8. At the same time, ammonia is sucked into the jet mixing device 1 from the ammonia inlet 111. The chlorosilane and the organic solvent are sprayed into the mixing section 13 through the nozzle 112. After being evenly mixed with the ammonia, they flow out from the fluid outlet 15 through the diffusion section 14, are further evenly mixed through the static mixer 3, and are transported to the reaction storage tank 4. The liquid in the reaction storage tank 4 then enters the jet mixing device 1 through the fluid inlet 11 for circulation until the pH value of the reaction system is 8-9. The reactants are filtered through the filter device 6 and transferred to the distillation kettle 7 for reduced pressure distillation to obtain the polysilazane.

[0061] Specifically, the unreacted ammonia in the reaction storage tank 4 can be sucked into the injection mixing device 1 after passing through the one-way valve 9. The function of the distillation kettle 7 is to remove the solvent and concentrate, which needs to be carried out under inert gas.

[0062] The technical solution of the present invention is further explained below in conjunction with specific embodiments.

[0063] Example 1

[0064] This embodiment discloses a spray mixing device 1, such as Figure 1 As shown, it includes a receiving chamber 12, a mixing section and a diffusion section 14 connected in sequence. A nozzle 112 is provided in the receiving chamber 12 to allow the fluid in the receiving chamber 12 to be sprayed into the mixing section 13. A fluid inlet 11 is provided at one end of the receiving chamber 12, and an ammonia inlet 111 is provided at the other end of the receiving chamber 12. The diffusion section 14 is provided with a fluid outlet 15. The diameter of the diffusion section 14 gradually increases along the direction of fluid flow.

[0065] Among them, the diameters of the fluid inlet 11 and the fluid outlet 15 are the same, both are DN25, the diameter of the ammonia inlet 111 is DN20 (G1 / 2), the diameter of the nozzle 112 is 8 mm, the diameter of the mixing section 13 is 14 mm, the length of the mixing section 13 is 40 mm, the diffusion angle of the diffusion section 14 is 9°, and the mouth-throat distance is 15 mm.

[0066] Example 2

[0067] like Figure 1-2 As shown, a method for quickly and efficiently preparing polysilazane in this embodiment uses the spray mixing device 1 of Example 1, and the specific method includes the following steps:

[0068] (1) Under nitrogen atmosphere, 15.6 L (150 mol) of methylhydrodichlorosilane, 7.26 L (75 mol) of dimethyldichlorosilane, and 68.61 L of toluene solvent were added to a 100 L raw material mixing tank 5 and mixed uniformly to obtain a mixture A; the temperature of the raw material mixing tank 5 was controlled at 0°C;

[0069] (2) Evaporating the liquid ammonia at a rate of 55 L / min, and sucking the ammonia gas into the jet mixing device 1 at a suction rate of 55 L / min, setting the injection speed of the mixture A to 2 L / min, and making the mixture A and the ammonia gas fully contact and react in the mixing section 13 and the diffusion section 14 of the jet mixing device 1 according to the condition that the molar ratio of the chlorine element in the chlorosilane to the sucked ammonia gas is 1:0.5, and the mixture can be further mixed in the pipeline and the static mixer 3 before entering the reaction storage tank 4. The reaction temperature in the reaction storage tank 4 is 0°C. The solid-liquid mixture after the reaction is subjected to preliminary solid-liquid separation by using a filter, and the separated liquid is injected into the raw material mixing tank 5. According to the initial set conditions, multiple rounds of injection reaction are carried out until the pH value of the entire reaction system reaches 8.7, thereby obtaining a crude product.

[0070] This embodiment actually requires 4 rounds of cyclic injection reaction. A single round of aminolysis reaction takes 45 to 46 minutes, and a total of 180 to 184 minutes for the 4 rounds of aminolysis.

[0071] (3) The crude product was subjected to solid-liquid separation using a filter press, and the separated liquid entered a distillation kettle 7 for distillation at a distillation temperature of 60° C. and a vacuum degree of 100 Pa until no fraction was distilled out, thereby obtaining polysilazane with a viscosity of 50 cp.

[0072] Example 3

[0073] A method for rapidly and efficiently preparing polysilazane in this embodiment includes the following steps:

[0074] (1) Under a nitrogen atmosphere, 5.21 L (50 mol) of methylhydrodichlorosilane, 5.87 L (50 mol) of methyltrichlorosilane, and 66.48 L of petroleum ether solvent were added to a 100 L raw material mixing tank 5 and mixed uniformly to obtain a mixture A. The temperature of the raw material mixing tank 5 was controlled at 0°C;

[0075] (2) Evaporating liquid ammonia at a rate of 50 L / min, ammonia gas was sucked into the jet mixing device 1 at a suction rate of 44 L / min, setting the injection rate of the mixture A to 30 L / min, and making the mixture A and ammonia gas fully contact and react in the mixing section 13 and the diffusion section 14 of the jet mixing device 1 according to the condition that the molar ratio of the chlorine element in the chlorosilane to the ammonia gas is 1:0.02. The mixture can be further mixed in the pipeline and the static mixer 3 before entering the reaction storage tank 4. The reaction temperature in the reaction storage tank 4 is -5°C. After 100 rounds of injection reaction in this embodiment, the pH value of the system reached 8.5, and a crude product was obtained. The aminolysis reaction took 4 hours and 18 minutes;

[0076] (3) The crude product was subjected to solid-liquid separation using a filter press, and the separated liquid entered a distillation kettle 7 for distillation at a distillation temperature of 40° C. and a vacuum degree of 50 Pa until no fraction was distilled out, thereby obtaining polysilazane with a viscosity of 98842 cp.

[0077] Example 4

[0078] A method for rapidly and efficiently preparing polysilazane in this embodiment includes the following steps:

[0079] (1) Under nitrogen atmosphere, 13 L (80 mol) of methylphenyldichlorosilane, 9.39 L (80 mol) of methyltrichlorosilane, and 67.17 L of tetrahydrofuran solvent were added to a 100 L mixing tank and mixed uniformly to obtain a mixture A; the temperature of the raw material mixing tank 5 was controlled at 30°C;

[0080] (2) Evaporating liquid ammonia at a rate of 100 L / min, sucking ammonia into the jet mixing device 1 at a rate of 100 L / min, setting the injection rate of the mixture A to 10 L / min, and subjecting the mixture A to a molar ratio of chlorine element in chlorosilane to ammonia of 1:0.2, bringing the mixture A into full contact with the ammonia in the mixing section 13 and the diffusion section 14 of the jet mixing device 1 to react, the mixture can be further mixed in the pipeline and the static mixer 3 before entering the reaction storage tank 4. The reaction temperature in the reaction storage tank 4 is 35°C. After 10 rounds of injection reaction, the pH value of the system reaches 8.8, and a crude product is obtained. The ammonia decomposition reaction takes 89 minutes and 35 seconds.

[0081] (3) The crude product is subjected to solid-liquid separation using a filter press, and the separated liquid enters a distillation kettle 7 for distillation at a distillation temperature of 80° C. and a vacuum degree of 1000 Pa until no fraction is distilled out, thereby obtaining solid polysilazane with a melting range of 110 to 120° C.

[0082] Example 5

[0083] A method for rapidly and efficiently preparing polysilazane in this embodiment includes the following steps:

[0084] (1) Under nitrogen atmosphere, 13.24 L (160 mol) of dihydrodichlorosilane and 79.44 L of dichloromethane were added to a 100 L mixing tank and mixed uniformly to obtain a mixture A. The temperature of the raw material mixing tank 5 was controlled at -10°C;

[0085] (2) Evaporating liquid ammonia at a rate of 40 L / min, sucking ammonia into the jet mixing device 1 at a rate of 40 L / min, setting the injection rate of the mixture A to 5 L / min, and subjecting the mixture A to a molar ratio of chlorine element in chlorosilane to ammonia of 1:0.1, fully contacting and reacting the mixture A with the ammonia in the mixing section 13 and the diffusion section 14 of the jet mixing device 1, the mixture can be further mixed in the pipeline and the static mixer 3 before entering the reaction storage tank 4. The reaction temperature in the reaction storage tank 4 is -25°C. After 20 rounds of injection reaction, the pH value of the system reaches 9.0, and a crude product is obtained. The aminolysis reaction takes 190 minutes;

[0086] (3) The crude product was subjected to solid-liquid separation using a filter press, and the separated liquid entered a distillation kettle 7 for distillation at a distillation temperature of 40° C. and a vacuum degree of 50 Pa until no fraction was distilled out, thereby obtaining polysilazane with a viscosity of 1200 cp.

[0087] Example 6

[0088] A method for rapidly and efficiently preparing polysilazane in this embodiment includes the following steps:

[0089] (1) Under nitrogen atmosphere, 15.61 L (150 mol) of methylhydrogendichlorosilane, 4.87 L (37.5 mol) of methylvinyldichlorosilane, and 61.44 L of n-pentane solvent were added to a 100 L mixing tank and mixed uniformly to obtain a mixture A. The temperature of the raw material mixing tank 5 was controlled at 5°C;

[0090] (2) Evaporating liquid ammonia at a rate of 10 L / min, sucking ammonia into the jet mixing device 1 at a rate of 10 L / min, setting the injection speed of the mixture A to 15 L / min, and subjecting the mixture A to a molar ratio of chlorine element in chlorosilane to ammonia of 1:0.02, fully contacting and reacting the mixture A with the ammonia in the mixing section 13 and the diffusion section 14 of the jet mixing device 1, the mixture can be further mixed in the pipeline and the static mixer 3 before entering the reaction storage tank 4. The reaction temperature in the reaction storage tank 4 is -5°C. After 100 rounds of injection reaction, the pH value of the system reaches 8.6, and a crude product is obtained. The single round of ammonolysis reaction takes 6 minutes, and the total ammonolysis reaction takes 600 minutes.

[0091] (3) The crude product was subjected to solid-liquid separation using a filter press, and the separated liquid entered a distillation kettle 7 for distillation at a distillation temperature of 70° C. and a vacuum degree of 200 Pa until no fraction was distilled out, thereby obtaining polysilazane with a viscosity of 100 cp.

[0092] Comparative Example 1

[0093] Under a nitrogen atmosphere, 15.61L (150mol) of methylhydrogendichlorosilane, 7.26L (75mol) of dimethyldichlorosilane, and 68.61L of toluene solvent were added to a 100L reactor and mixed uniformly. The reactor temperature was controlled at 0°C and, under mechanical stirring, ammonia was introduced at a rate of 2L / min until the pH value of the reaction system reached ≥8. The introduction of ammonia was stopped and a total ammonia amount (20160L) was required. The ammonia-passing time was 7 days. The mixture after ammonia solution was subjected to solid-liquid separation by filter press, and the separated liquid entered a distillation kettle 7 for distillation. The distillation temperature was controlled at 60°C and the vacuum degree was 100Pa until no fraction was evaporated to obtain a silazane oligomer with a viscosity of 50cP.

[0094] Compared with the bubbling ammonolysis method in Comparative Example 1, the ammonolysis time in Example 1 is greatly shortened, which is 1.786-1.825% of the ammonolysis time in Comparative Example 1, and the ammonolysis efficiency is increased by more than 100 times.

[0095] Comparative Example 2

[0096] The preparation method of the polysilazane in this comparative example is the same as that in Example 2, except that in step (2), the injection rate of the mixture A is 1 L / min.

[0097] A large amount of ammonia is difficult to fully mix and react with chlorosilane, and a large amount of ammonia remains inside the injection device, causing the local pressure of the injection device to increase, posing a hidden danger to production.

[0098] Comparative Example 3

[0099] The preparation method of the polysilazane in this comparative example is the same as that in Example 2, except that in step (1), the ammonia intake rate is 100 L / min.

[0100] In this comparative example, a large amount of ammonia gas is inhaled, and the ammonolysis rate of methylhydrogendichlorosilane is higher than that of methylvinyldichlorosilane. Methylhydrogendichlorosilane and methylvinyldichlorosilane will be ammonolyzed separately to form methylhydrogensilazane and methylvinylsilazane, rather than forming silazane containing both methylhydrogensilane and methylvinylsilane-silane segments in the molecule, which is not the target product. At the same time, the number average molecular weight of the synthesized silazane is reduced from 800-900 in Example 2 to 500-600, and the ceramic yield is reduced from 80% in Example 2 to 65%.

[0101] Comparative Example 4

[0102] The preparation method of polysilazane in this comparative example is the same as that in Example 2, except that the ratio of the diameter of the mixing section 13 to the diameter of the nozzle 112 is 2.0, the diffusion angle of the diffusion section 14 (the angle between the central axis and the hypotenuse) is 3°, and the ratio of the mouth-to-throat distance (the position from the nozzle 112 mouth to the connection between the receiving chamber 12 and the mixing section 13) to the diameter of the nozzle 112 is 6. At this time, the receiving chamber 12 can generate a negative pressure in the range of -0.12Mpa. At this time, ammonia can only be inhaled into the injection mixing device 1 at an intake volume of 2L / min. According to Example 2, only 4 rounds of cyclic injection reaction are required. Currently, a single round of aminolysis reaction takes 1238 to 1265 minutes, and 4 rounds of aminolysis require a total of 4950-5060 minutes; the aminolysis time is much higher than the time required to complete the aminolysis according to Example 2.

[0103] Comparative Example 5

[0104] The preparation method of the polysilazane in this comparative example is the same as that in Example 2, except that, in step (2), the molar ratio of the chlorine element in the chlorosilane to the inhaled ammonia is 1:0.6, and the corresponding liquid ammonia evaporation rate is 66 L / min. The ammonia is inhaled into the injection mixing device 1 at an intake rate of 66 L / min. At this time, the temperature in the injection device rises to 45-50° C., and the pressure of the reaction system increases. On the one hand, the intake rate of ammonia is significantly reduced from the set 66 L / min to 5 L / min, which reduces the ammonolysis efficiency. At the same time, the pressure in the reaction system increases, causing leakage of chlorosilane and ammonia, posing a safety hazard to production.

[0105] The above description is only a preferred specific 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 thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for rapidly and efficiently preparing polysilazane, characterized in that: The steps include: (1) evaporating liquid ammonia at a rate of 10 to 100 L / min, sucking ammonia gas into a jet mixing device at a rate of 10 to 100 L / min, and simultaneously inputting a mixed liquid of chlorosilane and an organic solvent in a raw material mixing tank into the jet mixing device, spraying and mixing the mixture of ammonia gas, chlorosilane, and organic solvent uniformly in the jet mixing device, and spraying the chlorosilane and organic solvent in the jet mixing device at a rate of 2 to 30 L / min, thereby obtaining a mixture A; (2) the mixture A is further mixed and reacted in a static mixer to obtain a mixture B, which is then fed into a raw material mixing tank and then sprayed into a spray mixing device to repeat step (1) until the pH value of the entire reaction system reaches ≥8, thereby obtaining a crude product; (3) subjecting the crude product to solid-liquid separation to obtain a liquid, and subjecting the liquid to reduced pressure distillation to obtain the polysilazane.

2. A method for rapidly and efficiently preparing polysilazane according to claim 1, characterized in that: In step (1), the molar ratio of the chlorine element in the injection mixing device to the inhaled ammonia gas is controlled to be 1:0.02-0.

5.

3. A method for rapidly and efficiently preparing polysilazane according to claim 1 or 2, characterized in that: In step (1), the organic solvent is one or more of C5-C10 alkanes, petroleum ether, ethers, tetrahydrofuran, aromatic hydrocarbons, acetone, esters or dichloromethane.

4. A method for rapidly and efficiently preparing polysilazane according to claim 1, characterized in that: In step (1), the volume ratio of the organic solvent to the chlorosilane is 3:1 to 6:

1.

5. A method for rapidly and efficiently preparing polysilazane according to claim 1, characterized in that: In step (3), the distillation temperature is 40-80° C. and the vacuum degree is 50-1000 Pa.

6. A jet mixing device for use in any one of the methods of claims 1 to 5, characterized in that: It includes a receiving chamber, a mixing section and a diffusion section connected in sequence. The receiving chamber is provided with a nozzle to allow the fluid in the receiving chamber to be sprayed into the mixing section. One end of the receiving chamber is provided with a fluid inlet, the other end of the receiving chamber is provided with an ammonia suction port, and the diffusion section is provided with a fluid outlet.

7. The jet mixing device according to claim 6, characterized in that The diameter of the diffusion section gradually increases along the flow direction of the fluid.

8. The jet mixing device according to claim 6, characterized in that The diameters of the fluid inlet and the fluid outlet are the same, the diameter of the nozzle is 4-12 mm, the diameter of the mixing section is 7-20 mm, the ratio of the diameter of the mixing section to the diameter of the nozzle is 1.7-1.8, and the length of the mixing section is 10-50 mm.

9. The jet mixing device according to claim 8, characterized in that The diffusion angle of the diffusion section is 6° to 16°, and the ratio of the mouth-throat distance to the nozzle diameter is 1 to 3.

5.

10. A system for preparing the polysilazane according to any one of claims 1 to 5, characterized in that: The invention comprises a liquid ammonia tank, a spray mixing device, a static mixer, a reaction material storage tank, a filtering device and a distillation kettle which are connected in sequence. The spray mixing device is also connected to a raw material mixing tank.

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