A system and method for the preparation of isocyanatoalkoxysilanes by the phosgene method

Abstract

The application provides a system and a method for preparing isocyanate alkoxysilane by using phosgene, which comprises the following parts: a photochemical reactor, in which amine alkoxysilane is photochemically reacted with phosgene; a static gas-liquid separator, which separates the reaction liquid flowing out of the photochemical reactor to obtain reaction liquid I and gas phase I; a dynamic gas-liquid separator, which separates the reaction liquid I under stirring to obtain a crude product containing isocyanate alkoxysilane and gas phase II; a crude product buffer tank, which collects the crude product containing isocyanate alkoxysilane; a rectifying tower, which separates the crude product by rectification to obtain isocyanate alkoxysilane; and a tail gas recovery device, which collects the gas phase I and the gas phase II, condenses the collected gas phase I and the gas phase II, and returns the obtained phosgene to the photochemical reactor. The preparation method provided by the application can quickly reduce the content of phosgene and hydrogen chloride in the system, and can prepare silane isocyanate with excellent performance at a low cost and a high efficiency.

Description

Technical Field

[0001] This invention relates to the technical field of preparing silane isocyanates, and more specifically to a system and method for preparing silane isocyanates by the phosgene method. Background Technology

[0002] Currently, most industrial methods for manufacturing isocyanates involve the reaction of amines with carbamate chlorides. In this reaction, the amine and carbamate chloride first form carbamate chloride, which generates one mole of isocyanate group and simultaneously produces two moles of hydrogen chloride. At the same time, once hydrogen chloride is generated in the system, it reacts with functional groups in the amine precursor, intermediate, and isocyanate product, producing various byproducts.

[0003] Similar problems exist in the preparation of isocyanates containing siloxanes. When hydrogen chloride is generated, it reacts with the alkoxysilane in the isocyanate product to produce chlorosilanes and corresponding alcohols, leading to the formation of other byproducts and reducing the overall yield of the target isocyanate.

[0004] To address the aforementioned problems, US Patent 4,654,428 discloses the use of a tertiary amine, such as triethylamine or tripropylamine, in the reaction mixture. In this method, hydrogen chloride is neutralized by the tertiary amine to form an amine hydrochloride. The amine hydrochloride is precipitated and filtered off, yielding a filtrate containing the isocyanate product. Further distillation of the filtrate yields the isocyanate product. However, this method has several drawbacks. For example, the amine salt formed by the tertiary amine and hydrogen chloride is typically a high-volume, low-density, and loose solid, making it difficult and expensive to handle. Furthermore, the patent uses an alkali metal salt or alkaline earth metal salt of a carboxylic acid to treat the filtrate or distillate, adding to the cost of this additional treatment step. In practice, to ensure effective quenching of hydrogen chloride, an excess of amine is used, which necessitates an additional step of stripping the excess amine from the final product, further increasing the cost of the method.

[0005] Existing technology CN104334565A separates isocyanate compounds containing alkoxysilanes from the hydrochloride salt of the base obtained in the previous step by adding a base followed by centrifugation or filtration. For example, taking the starting material amine KH550 (aminopropyltriethoxysilane) as an example, isocyanate products prepared by the existing phosgene method are prone to contain dichloro and monochloro impurities, affecting yield and quality. The specific reaction process is as follows:

[0006]

[0007] During the phosgene process, the siloxane bonds in propyltriethoxysilane readily react with the HCl produced in the reaction, resulting in more reactive chlorinated byproducts with poorer storage stability and a greater susceptibility to polymerization with water.

[0008]

[0009] After the conventional photochemical reaction of isocyanates (such as MDI, TDI, and HDI) is completed, a post-treatment process of the reaction solution is performed. First, phosgene is removed to ensure that the phosgene and hydrogen chloride content in the photochemical reaction solution is below 100 ppm. This is generally achieved using a vacuum system for distillation or rectification, with small-scale nitrogen purging as needed. However, distillation or rectification requires heating, resulting in a certain residence time at high temperatures. Due to the varying stability of different isocyanates, for isocyanate-based siloxanes, a prolonged separation time leads to a significant replacement of the silicon-oxygen bonds in the isocyanate-based alkoxysilanes by chlorine. Furthermore, methanol or ethanol in the system can continue to undergo side reactions with the isocyanate groups, resulting in a substantial decrease in product yield.

[0010] It is evident that in the actual industrial production of isocyanate-based alkoxysilanes via phosgenation, residual phosgene and hydrogen chloride in the system significantly affect the yield. Therefore, mastering the optimal technical conditions to improve the yield of isocyanate-based alkoxysilanes has become a major issue for expanding production capacity. Summary of the Invention

[0011] To overcome the shortcomings of existing technologies, this invention employs a phosgene method instead of the traditional pyrolysis reaction to prepare isocyanate-based alkoxysilanes. By rapidly separating phosgene and hydrogen chloride, the use of acid-binding agents is avoided, resulting in isocyanate-based alkoxysilanes with lower impurity content. This method reduces both production costs and environmental hazards.

[0012] To achieve the objectives of this invention, the following technical solution is adopted:

[0013] The first aspect of this invention provides a system for preparing isocyanate-based alkoxysilanes using a phosgene method, the system comprising:

[0014] Photochemical reactor: used to carry out photochemical reactions of aminoalkoxysilanes with phosgene;

[0015] Static gas-liquid separator: used to separate the reaction liquid flowing out of the photochemical reactor into gas and liquid phases to obtain separated reaction liquid phase 1 and gas phase phase 1;

[0016] Dynamic gas-liquid separator: used to separate the reaction liquid one into gas and liquid under stirring to obtain the separated crude product containing isocyanate-based alkoxysilane and gas phase two;

[0017] Crude product buffer tank: used to collect the crude product containing isocyanate-based alkoxysilanes;

[0018] Distillation column: used to distill and separate the crude product to obtain isocyanate-based alkoxysilane;

[0019] The exhaust gas recovery unit is used to collect the first and second phase gases, condense them, and return the condensed phosgene to the phosgene inlet of the photochemical reactor.

[0020] In the system for preparing isocyanate-based alkoxysilanes by the phosgene method provided by the present invention, the photochemical reactor is a tubular reactor. The tubular reactor is selected from microchannel tubular reactors or tubular reactors filled with spiral plates and / or wire mesh inside, which is used to increase the turbulence of the fluid in the reactor and make the material more uniformly mixed.

[0021] In the system provided by this invention, the static gas-liquid separator is selected from a separation tower filled with baffles and / or wire mesh. The reaction liquid flows rapidly in the static separator composed of baffles and wire mesh. Due to the complex and tortuous flow direction caused by the channel, droplets are captured by impacting the equipment surface under inertial force. Under gravity, they gradually gather downwards and are discharged through the bottom discharge pipe into the dynamic gas-liquid separator. In some preferred embodiments, after passing through the static gas-liquid separator, the content of phosgene and hydrogen chloride is reduced to below 1%.

[0022] In the system provided by this invention, the dynamic gas-liquid separator mainly utilizes the principle of cyclone separation. Due to the density difference between gas and liquid, when the liquid and gas mix and flow together, the centrifugal force on the liquid is greater than that on the gas. The liquid adheres to the separation wall and, due to gravity, flows downwards and collects together before being discharged through the discharge pipe. In some specific embodiments, the dynamic gas-liquid separator in the system provided by this invention can be selected from a cyclone separator; in some specific embodiments, the separation chamber in the dynamic gas-liquid separator has an inverted conical structure, and the cone angle of the separation chamber is 10–45°, preferably 25–30°.

[0023] In some specific embodiments, reaction liquid one enters the high-speed rotating chamber (separation chamber) through the feed inlet at the bottom of the dynamic gas-liquid separator. Within the separation chamber, reaction liquid one undergoes a spiral upward motion due to the high-speed rotation. Due to the different effects of gravity on the gas and liquid, they gradually separate during this spiral ascent, yielding a crude product containing isocyanate-based alkoxysilanes and a gas phase two. More specifically, the bottom of the dynamic gas-liquid separator has a high-speed rotating disk driven by a motor. The rotating disk is equipped with blade-shaped liquid-guiding protrusions, which adjust the rotation speed of the cyclone disk.

[0024] In some specific embodiments, the degassed crude product is discharged into a crude product buffer tank through the overflow port on the dynamic gas-liquid separator for later use, and the content of phosgene and hydrogen chloride in the obtained crude product is reduced to below 100 ppm. The remaining phosgene and hydrogen chloride gas move upward with the internal swirling flow, and after being discharged from the upper gas outlet pipe of the dynamic gas-liquid separator, they enter the tail gas recovery unit. The phosgene is condensed and separated from the hydrogen chloride, and then returned to the phosgene inlet of the photochemical reactor.

[0025] In the system provided by the present invention, the distillation column is a packed column, the packing material is preferably stainless steel, and the theoretical number of trays is 2 to 30, preferably 5 to 20.

[0026] A second aspect of the present invention provides a method for preparing isocyanate-based alkoxysilanes using the above-described system, the method comprising the following steps:

[0027] a. React aminoalkoxysilane with phosgene in a photochemical reactor to obtain a reaction solution containing isocyanate-based alkoxysilane;

[0028] b. The reaction liquid is separated in a static gas-liquid separator to obtain reaction liquid one and gas phase one;

[0029] After the obtained gas phase is condensed by the tail gas recovery unit, the resulting phosgene is returned to the photochemical reactor;

[0030] The resulting reaction liquid flows into a dynamic gas-liquid separator for separation, yielding a crude product containing isocyanate-based alkoxysilane and a second gas phase. The second gas phase is condensed by a tail gas recovery unit, and the resulting phosgene is returned to the photochemical reactor.

[0031] c. The crude product containing isocyanate-based alkoxysilane is separated by distillation in a distillation column to obtain isocyanate-based alkoxysilane.

[0032] In step a of the method of the present invention, the reaction temperature is 0-50°C, preferably 0-30°C; the reaction time is 0.1-20 min, preferably 1-5 min; in some preferred embodiments, the molar amount of phosgene supplied in the reaction is 2-20 times, preferably 5-10 times, for example, 2 times, 3 times, 8 times, or 15 times, of the molar amount of aminoalkoxysilane.

[0033] In a specific embodiment of the method of the present invention, the aminoalkoxysilane is dissolved in an organic solvent to form an aminoalkoxysilane solution, and then reacted with phosgene (i.e., photochemical reaction); preferably, the mass content of aminoalkoxysilane in the aminoalkoxysilane solution is 1-50%, more preferably 3-30%; more preferably, the organic solvent can be selected from one or more of benzene, toluene, n-hexane, cyclohexane, halogenated hydrocarbons or ester solvents; wherein, the halogenated hydrocarbons can be selected from dichloromethane, chlorobenzene, o-dichlorobenzene, dichlorobenzene, chloroform or trichloroethylene; the ester solvents can be selected from methyl acetate or ethyl acetate; the ether solvents can be selected from diethyl ether, 1,2-diethoxyethane or dioxane.

[0034] In some specific embodiments, the aminoalkoxysilane is selected from one or more of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldibutoxymethylsilane, 3-aminopropyldipropoxymethylsilane, 3-aminopropyldimethoxymethylsilane, 3-aminopropyldiethoxymethylsilane, 1-aminomethyltrimethoxysilane, 1-aminomethyldimethoxymethylsilane, and 1-aminomethyldiethoxymethylsilane.

[0035] In step b of the method of the present invention, the residence time of the reaction liquid in the static gas-liquid separator is 0.1–10 min, preferably 1–3 min; the residence time of the reaction liquid in the dynamic gas-liquid separator is 0.1–10 min, preferably 1–3 min. In the preparation process of the present invention, the short residence time of the reaction liquid in the static and dynamic gas-liquid separation processes avoids side reactions such as the substitution of silicon-oxygen bonds in isocyanate-based alkoxysilanes, thereby improving the product yield.

[0036] In step b of the method of the present invention, the absolute pressure of static gas-liquid separation and dynamic gas-liquid separation is 80-99 kPa; in some preferred embodiments, the absolute pressure of static gas-liquid separation and dynamic gas-liquid separation is 90-98 kPa, which ensures the effective separation of HCl and residual phosgene in the reaction system. If the pressure is too low, it will be detrimental to the subsequent separation and recovery of phosgene.

[0037] In step b of the method of the present invention, the phosgene in gas phase one and gas phase two is recycled and reused in the photochemical reactor. Specifically, the recycling method includes steps such as condensation absorption to separate phosgene from hydrogen chloride. This separation step is well known to those skilled in the art, and the specific operation process will not be described in detail here.

[0038] In step c of the method of the present invention, the temperature of the distillation separation process is 100-200°C; the absolute pressure of the distillation separation is 0.1-10 kPa, preferably 0.5-5 kPa.

[0039] The above technical solution achieves the following technical effects:

[0040] The system for preparing silane isocyanates by phosgene method provided by the present invention has a small equipment size and a small liquid holding capacity, thereby achieving a large separation and processing capacity and obvious processing effect.

[0041] The phosgene method for preparing silane isocyanates provided by this invention can rapidly reduce the content of phosgene and hydrogen chloride in the system, thereby preparing high-performance silane isocyanates at a lower cost and higher efficiency. Compared with existing technologies, the preparation method of this invention does not use acid-binding agents, generates no solid waste such as waste salts, has low production costs, and high reaction yields, thus possessing significant practical value and environmental benefits. Attached Figure Description

[0042] Figure 1 The flowchart of the phosgene method for preparing isocyanate-based alkoxysilanes of the present invention.

[0043] The components include: 1. Photochemical reactor; 2. Static gas-liquid separator; 3. Dynamic gas-liquid separator; 4. Crude product buffer tank; 5. Tail gas recovery unit; and 6. Distillation column. Detailed Implementation

[0044] To better understand the technical solution of the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0045] The following test methods are used in the embodiments and comparative examples of the present invention:

[0046] (1) Purity and chlorinated impurity content in isocyanate-based alkoxysilanes: qualitative and quantitative analysis was performed by gas chromatography;

[0047] The analysis and detection were performed using an Agilent 7890B gas chromatograph under the following conditions:

[0048] Column: Agilent 19091J-413DP-5;

[0049] 0℃-325℃(350℃):30m×320μm×0.25μm;

[0050] Carrier gas: High-purity N2 (purity above 99.999%) that has been purified and dried;

[0051] Combustion gas: H2 (purity above 99.999%), flow rate 40 mL / min;

[0052] Combustion aid: purified and dry air with a flow rate of 400 mL / min;

[0053] Purging gas: N2, with a flow rate of 30 mL / min;

[0054] Column flow rate: 1.2 mL / min, split ratio: 30:1;

[0055] Column oven temperature, injection port temperature, detector temperature: 280℃;

[0056] Injection volume: 0.001 mL.

[0057] (2) Conversion rate: Calculated based on the results of normalized gas chromatographic area analysis.

[0058] Conversion rate = (100-aminoalkoxysilane area percentage) / 100 × 100%.

[0059] Adopting such Figure 1 The method shown is used to prepare isocyanate-based alkoxysilanes:

[0060] a. A microchannel tubular reactor is used as the photochemical reactor 1. Chlorobenzene solutions of KH550 (3-aminopropyltriethoxysilane) of different concentrations are prepared and slowly introduced through the top of the photochemical reactor 1. Phosgene is introduced into the reactor through the inlet of the photochemical reactor 1 to carry out the photochemical reaction. The temperature range of the reaction is controlled and the molar amount of phosgene supplied is adjusted.

[0061] b. A separation tower filled with baffles is used as the static gas-liquid separator 2. The reaction liquid from the outlet of the photochemical reactor 1 is fed into the inlet of the static gas-liquid separator 2. The flow rate of the reaction liquid is adjusted to control the absolute pressure of the static gas-liquid separator 2. The interior of the static gas-liquid separator 2 is filled with corrugated stainless steel packing. The reaction liquid is atomized into small droplets for gas-liquid separation, resulting in reaction liquid phase 1 and gas phase 1. The separated gas phase 1 is then transported to the tail gas recovery unit 5.

[0062] A hydrocyclone separator is used as the dynamic gas-liquid separator 3. The reaction liquid flowing out of the outlet of the static gas-liquid separator 2 is pumped to the inlet of the dynamic gas-liquid separator 3. Dynamic gas-liquid separators 3 with different cone angles are used. After starting the motor of the separator, the speed of the hydrocyclone is adjusted. The crude product containing isocyanate-based alkoxysilane is sent to the crude product buffer tank 4 through the upper overflow port. The gas phase obtained after separation is sent to the tail gas recovery unit 5. The tail gas recovery unit 5 obtains phosgene by condensation at -10℃ and reuses it at the inlet of the photochemical reactor 1.

[0063] c. The crude product containing isocyanate-based alkoxysilane is distilled in a 10-theoretical-plate distillation column 6, wherein the distillation solvent is chlorobenzene, the distillation pressure is 10 kPa, and the distillation temperature is 80 °C. After removing chlorobenzene by vacuum distillation, the colorless liquid obtained by vacuum distillation in a 20-theoretical-plate distillation column at a distillation pressure of 0.1 kPa and a still temperature of 140 °C is 3-isocyanate-propyltriethoxysilane.

[0064] Examples 1-6 and Comparative Examples 1-6 of this invention were prepared using the above method. Examples 7-9 used the same method as Example 3, except that 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, and 3-aminopropylmethyldimethoxysilane were used as reactants for photochemical reactions, respectively. The specific parameter settings and analysis data for each example are shown in Tables 1-3 below:

[0065] Specifically, the parameters such as phosgene flux, residence time in the reaction section, and reaction temperature in photochemical reactor 1, as well as the analytical data of the reaction liquid, are shown in Table 1:

[0066] Table 1

[0067]

[0068] Note: "Reaction concentration" in the table refers to the mass percentage of KH550 in the chlorobenzene solution of KH550; "phosgene / amine" refers to the ratio of the molar amount of phosgene supplied to the molar amount of aminoalkoxysilane in the reaction; "Reaction solution purity" refers to the purity of the reaction solution containing isocyanate-based alkoxysilane.

[0069] The pressure, flow rate and other parameters of the static gas-liquid separator 2, as well as the data of the obtained reaction liquid 1, are analyzed and shown in Table 2.

[0070] Table 2

[0071]

[0072]

[0073] Note: The "pressure of the separator" in the table refers to the pressure of the static gas-liquid separator.

[0074] The cone angle, motor speed, pressure parameters inside the separator, and crude product containing isocyanate-based alkoxysilanes of the dynamic gas-liquid separator 3 were analyzed, and the data are shown in Table 3.

[0075] Table 3

[0076]

[0077] Note: "Pressure", "Speed", and "Cone Angle" in the table refer to the parameters of the dynamic gas-liquid separator; "Purity of Crude Product" in the table refers to the content of isocyanate-based alkoxysilane in the crude product.

[0078] Comparative Examples 7-9

[0079] Comparative Examples 7-9 employed a hot-cold liquid-phase phosgene process. First, a 1L reaction apparatus equipped with a stirrer and thermometer was placed in a water bath. Then, 30g of KH550 (3-aminopropyltriethoxysilane) was dissolved in 270g of chlorobenzene, and the solution was added to the reaction apparatus and stirred, maintaining the temperature between 5℃ and 30℃.

[0080] Then, carbonyl chloride was introduced into the reaction apparatus at a rate of 150 L / h for a cold-thermal photochemical reaction, with the cold reaction temperature controlled at 5–50 °C and the reaction residence time at 40 min. A hot reaction was then carried out, with the hot reaction temperature controlled at 50–100 °C and the reaction residence time at 150 min. After the reaction, an acid-binding agent was used to bind the acid, and the reaction solution was neutralized with triethylamine before centrifugation and filtration to separate triethylamine hydrochloride. The crude product was then subjected to the following separation operations: It was distilled in a 10-theoretical-plate distillation column, with chlorobenzene as the distillate, a distillation pressure of 10 kPa, and a distillation temperature of 80 °C. After removing chlorobenzene by vacuum distillation, the product was vacuum distilled in a 20-theoretical-plate distillation column at a distillation pressure of 0.1 kPa and a vessel temperature of 140 °C to obtain a colorless liquid, yielding 3-isocyanate propyltriethoxysilane.

[0081] The specific reaction conditions and analytical data of the above comparative examples 7-9 are shown in Table 4:

[0082] Table 4

[0083]

[0084] The analysis data from Comparative Examples 7-9 show that side reactions continue to occur during the existing preparation process, resulting in the enrichment of by-products, leading to poor product purity and low product yield.

[0085] Comparative Example 10

[0086] Taking KH550 (3-aminopropyltriethoxysilane) as an example, the thermal cracking process for synthesizing isocyanate-based alkoxysilanes consists of two steps:

[0087] Step 1: First, [3-(triethoxysilyl)propyl]carbamate (UPTS) was synthesized. KH550, diethyl carbonate, and sodium carbonate catalyst were added sequentially to a reactor in a molar ratio of 1:1.3:0.05, and the reaction was carried out at 60°C for 6 hours. After the reaction, phosphoric acid was added in a 1:1 molar ratio to quench the catalyst. The resulting UPTS had a purity of 88.3%.

[0088] After synthesis, the UPTS reaction solution needs to be post-treated. First, light components such as ethanol, acetic acid, and diethyl carbonate are removed from the reaction solution at 70℃ / 10KPaA. After removing the light components, the crude UPTS is distilled at 120℃ / 20PaA to obtain crude UPTS.

[0089] Step 2: The crude carbamate (UPTS) obtained in Step 1 was subjected to thermal pyrolysis. UPTS product and pyrolysis catalyst (zinc oxide) were added to a reactor, and the pyrolysis reaction was carried out at 180℃ / 3KPaA, with continuous distillation to collect the product. The collected distillate was a mixture of UPTS / IPTS, and the product 3-isocyanate propyltriethoxysilane (IPTS) had a purity of 83.6%.

[0090] The UPTS / IPTS mixed fraction from the cracking was separated by distillation at 150℃ / 20PaA to obtain the final isocyanate-based alkoxysilane product with an overall yield of 58.6%.

[0091] Compared with the pyrolysis method of Comparative Example 10, the reaction steps are numerous, catalysts and quenchers are used, the reaction time is long, the energy consumption is high, and the thermal pyrolysis process is difficult to control, resulting in low yield and difficult waste treatment. The phosgene preparation method of the present invention has many advantages.

Claims

1. A system for the preparation of isocyanatoalkoxysilanes by the phosgene method, characterized in that The system comprises: a photochemical reactor (1) for photochemical reaction of amine alkoxysilane with phosgene; a static gas-liquid separator (2) for gas-liquid separation of reaction liquid flowing out of the photochemical reactor (1) to obtain separated reaction liquid I and gas phase I; a dynamic gas-liquid separator (3) for gas-liquid separation of the reaction liquid I under high-speed agitation to obtain a crude product containing isocyanate alkoxysilane and gas phase II; a crude product buffer tank (4) for collecting the crude product containing isocyanate alkoxysilane; a rectifying column (6) for rectifying separation of the crude product to obtain isocyanate alkoxysilane; a tail gas recovery device (5) for collecting the gas phase I and gas phase II, condensing the same, and returning the condensed phosgene to a phosgene inlet of the photochemical reactor (1).

2. The system of claim 1, wherein, The photochemical reactor (1) is a tubular reactor. The tubular reactor is selected from a micro-channel tubular reactor or a tubular reactor internally filled with spiral plates and / or wire mesh.

3. The system of claim 1 or 2, wherein, The static gas-liquid separator (2) in the system is selected from a separation column filled with baffles and / or wire mesh.

4. The system of claim 3, wherein, The dynamic gas-liquid separator (3) in the system is selected from a cyclone separator. The separation chamber in the dynamic gas-liquid separator (3) is in a conical structure, and the cone angle of the separation chamber is 10-45°.

5. The system of claim 4, wherein, The cone angle of the separation chamber is 25-30°.

6. A method for producing isocyanatoalkoxysilane using the system according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: a. reacting amine alkoxysilane with phosgene in a photochemical reactor (1) to obtain a reaction liquid containing isocyanate alkoxysilane; b. separating the reaction liquid in a static gas-liquid separator (2) to obtain reaction liquid I and gas phase I; The obtained gas phase I is condensed by a tail gas recovery device (5), and the obtained phosgene is returned to the photochemical reactor (1); The obtained reaction liquid I flows into a dynamic gas-liquid separator (3) for separation to obtain a crude product containing isocyanate alkoxysilane and gas phase II; the obtained gas phase II is condensed by a tail gas recovery device (5), and the obtained phosgene is returned to the photochemical reactor (1); c. rectifying separation of the crude product containing isocyanate alkoxysilane by a rectifying column (6) to obtain isocyanate alkoxysilane.

7. The method of claim 6, wherein, In step a, the reaction temperature is 0-50°C, and the reaction time is 0.1-20 min.

8. The method of claim 7, wherein, In step a, the reaction temperature is 0-30°C.

9. The method of claim 7, wherein, In step a, the reaction time is 1-5 min.

10. The method of claim 7, wherein, The supply molar amount of phosgene in the reaction is 2-20 times the molar amount of amine alkoxysilane.

11. The method of claim 10, wherein, The supply molar amount of phosgene in the reaction is 5-10 times the molar amount of amine alkoxysilane.

12. The method of claim 7, wherein, In step a, the amine alkoxysilane is dissolved in an organic solvent to form an amine alkoxysilane solution, and then the reaction is performed with phosgene.

13. The method of claim 12, wherein, In the amine alkoxysilane solution, the mass content of amine alkoxysilane is 1-50%.

14. The method of claim 13, wherein, In the amine alkoxysilane solution, the mass content of amine alkoxysilane is 3-30%.

15. The method of claim 12, wherein, The amine-based alkoxysilane is selected from one or more of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyl dibutoxymethylsilane, 3-aminopropyl dipropoxymethylsilane, 3-aminopropyl dimethoxymethylsilane, 3-aminopropyl diethoxymethylsilane, 1-aminomethyltrimethoxysilane, 1-aminomethyl dimethoxymethylsilane, and 1-aminomethyl diethoxymethylsilane; The organic solvent is selected from one or more of benzene, toluene, n-hexane, cyclohexane, chlorinated hydrocarbon, or ester solvent.

16. The method according to any one of claims 6 to 15, characterized in that, During the separation in step b, the residence time of the reaction liquid in the static gas-liquid separator (2) is 0.1-10 min. The residence time of the reaction liquid in the dynamic gas-liquid separator (3) is 0.1-10 min.

17. The method of claim 16, wherein, During the separation in step b, the residence time of the reaction liquid in the static gas-liquid separator (2) is 1-3 min.

18. The method of claim 16, wherein, The residence time of the reaction liquid in the dynamic gas-liquid separator (3) is 1-3 min.

19. The method of claim 16, wherein, During the separation in step b, the absolute pressure of the static gas-liquid separator (2) and the dynamic gas-liquid separator (3) is 80-99 kPa.

20. The method of claim 19, wherein, During the separation in step b, the absolute pressure of the static gas-liquid separator (2) and the dynamic gas-liquid separator (3) is 90-98 kPa.

21. The method of claim 16, wherein, During the separation in step b, the flow rate of the reaction liquid into the static gas-liquid separator (2) is 0.5-3 mL / s. The flow rate of the reaction liquid into the dynamic gas-liquid separator (3) is 0.5-3 mL / s.

22. The method of claim 21, wherein, The rotation speed of the high-speed agitation in the dynamic gas-liquid separator (3) is 300-3000 r / min.

23. The method of claim 21, wherein, In step c, the temperature of the rectification separation is 100-200℃. The absolute pressure of the rectification separation is 0.1-10 kPa.

24. The method of claim 23, wherein, The absolute pressure of the rectification separation is 0.5-5 kPa.

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