Preparation method of vinyl double-end socket

Abstract

The invention belongs to the technical field of organic silicon chemical products, and particularly relates to a preparation method of a vinyl double-end socket. Comprising the following steps: in a tubular fixed bed catalytic continuous reactor filled with a supported catalyst, carrying out nucleophilic substitution reaction on dimethyldichlorosilane and dimethyldiethoxysilane under the action of the supported catalyst to obtain a dimethyl ethoxychlorosilane intermediate; the method comprises the following steps: mixing liquid sodium with a solvent, carrying out Wuichi reaction on the mixture, a dimethyl ethoxy chlorosilane intermediate and vinyl chloride in a tubular continuous sodium condensation reactor, adding ethanol into the reacted mixture for treatment, carrying out solid-liquid separation to obtain a sodium salt mainly containing sodium chloride and a mixed solution, and carrying out rectification separation on the mixed solution to obtain the vinyl single end socket. And carrying out continuous hydrolysis reaction on the vinyl single end socket to obtain the vinyl double end socket. The tubular continuous technology is used, so that the safety of the whole production process is effectively improved, and the operation safety risk is reduced while the sodium utilization rate is improved.

Description

Technical Field

[0001] This invention belongs to the technical field of organosilicon chemical products, specifically relating to a method for preparing vinyl double-ended heads. Background Technology

[0002] 1,3-Divinyltetramethyldisiloxane, abbreviated as vinyl di-terminated, is a key functional intermediate in the organosilicon industry. The divinyl functional groups in its molecular structure endow the product with excellent reactivity and crosslinking properties. This compound holds an irreplaceable position in the synthesis of specialty silicone oils, particularly as an end-group modifier that can precisely control the degree of polymerization and molecular weight distribution of vinyl silicone oils. Furthermore, its application value as a crosslinking promoter and interface modifier is increasingly prominent in high-end fields such as addition-type liquid silicone rubber, photocurable coatings, and organic-inorganic hybrid materials.

[0003] Currently, the main process for producing vinyl double-ended heads is based on a multi-stage condensation reaction system. The specific synthetic route is as follows: Dimethyldichlorosilane is used as the starting material and undergoes an alcoholysis reaction with ethanol to generate dimethyldiethoxysilane; then, it is reacted with vinyl chloride using the sodium condensation method to synthesize the key intermediate dimethylvinylethoxysilane, which is referred to as a vinyl single-ended head; finally, the vinyl single-ended head is subjected to a hydrolysis-condensation reaction to achieve the directional assembly of the divinyl functional groups, thus obtaining the vinyl double-ended head.

[0004] The continuous production process for synthesizing dimethyldiethoxysilane via the alcoholysis reaction of dimethyldichlorosilane and ethanol is well-established, achieving yields of over 98%. However, the high-temperature sodium condensation reaction of dimethyldiethoxysilane and vinyl chloride produces sodium ethoxide and sodium chloride as byproducts. The large amount of sodium ethoxide generated, which precipitates as a viscous paste during the high-temperature reaction and coats unreacted sodium, poses certain operational safety risks and results in low sodium utilization, only 50%–60%. Summary of the Invention

[0005] To address the technical problems of existing technologies that generate large amounts of sodium ethoxide as a byproduct during the sodium condensation reaction, and that sodium ethoxide coats unreacted sodium, leading to operational safety risks and low sodium utilization, this invention provides a method for preparing vinyl double-ended heads.

[0006] The purpose of this invention is to provide a method for preparing vinyl double-ended heads, comprising the following steps: In a tubular fixed-bed catalytic continuous reactor packed with a supported catalyst, dimethyldichlorosilane and dimethyldiethoxysilane undergo a nucleophilic substitution reaction under the action of the supported catalyst to obtain a dimethylethoxychlorosilane intermediate. Liquid sodium is mixed with a solvent and then reacted with the dimethylethoxychlorosilane intermediate and vinyl chloride in a tubular continuous sodium condensation reactor to undergo a Wurtz reaction. Ethanol is added to the reacted mixture for further treatment. Solid-liquid separation yields a sodium salt (mainly sodium chloride) and a mixed solution. The mixed solution is then subjected to distillation to obtain a vinyl single-ended head. The vinyl single-ended head undergoes continuous hydrolysis to obtain a vinyl double-ended head. The specific synthetic route is shown below:

[0007] .

[0008] This invention uses dimethyldichlorosilane and dimethyldiethoxysilane as raw materials. After filling a tubular fixed-bed catalytic continuous reactor with a supported catalyst, dimethyldichlorosilane and dimethyldiethoxysilane undergo a nucleophilic substitution reaction under the catalysis of the supported catalyst. The chlorine atom in dimethyldichlorosilane has high electronegativity, which polarizes the Si-Cl bond, and the chlorine atom ends with a partial negative charge. At the same time, the ethoxy group in dimethyldiethoxysilane acts as a nucleophilic group and launches a nucleophilic attack on the silicon atom in dimethyldichlorosilane. The ethoxy group is substituted as a leaving group to generate the dimethylethoxychlorosilane intermediate.

[0009] Preferably, the molar ratio of dimethyldichlorosilane to dimethyldiethoxysilane is 1:1 to 1.3.

[0010] It should be noted that the specific process for preparing the dimethylethoxychlorosilane intermediate is as follows: a supported catalyst is packed into a tubular fixed-bed catalytic continuous reactor; dimethyldichlorosilane and dimethyldiethoxysilane are completely mixed in a mixer and then introduced into the tubular fixed-bed catalytic continuous reactor; the temperature of the tubular fixed-bed catalytic continuous reactor is controlled at 25℃~60℃, and the residence time is 5min~15min. This invention utilizes a tubular fixed-bed catalytic continuous reactor to replace the traditional batch reactor, reducing backmixing, improving selectivity, and suppressing side reactions; based on dimethyldichlorosilane, the reaction selectivity can reach over 99%.

[0011] Preferably, the tubular fixed-bed catalytic continuous reactor is made of corrosion-resistant tubing; the material of the tubular fixed-bed catalytic continuous reactor is PTFE tubing, PTFE-lined steel tubing, silicon carbide tubing, or Hastelloy tubing.

[0012] The present invention utilizes a supported catalyst to promote the exchange reaction between dimethyldiethoxysilane and dimethyldichlorosilane; preferably, the supported catalyst is made of a first catalyst and a substrate supporting the first catalyst; wherein the first catalyst accounts for 5% to 10% of the mass percentage of the supported catalyst.

[0013] Preferably, the first catalyst is a Lewis acid catalyst.

[0014] Preferably, the first catalyst is at least one of aluminum trichloride, ferric chloride, boron trifluoride, antimony pentachloride, titanium tetrachloride, and trifluoromethanesulfonate; the trifluoromethanesulfonate in the first catalyst is yttrium trifluoromethanesulfonate, ytterbium trifluoromethanesulfonate, bismuth trifluoromethanesulfonate, lanthanum trifluoromethanesulfonate, or magnesium trifluoromethanesulfonate.

[0015] More preferably, the first catalyst is aluminum oxide and yttrium trifluoromethanesulfonate.

[0016] Preferably, the substrate supporting the first catalyst is a silica molecular sieve, a mesoporous molecular sieve, alumina, zeolite, or metal-organic framework material.

[0017] More preferably, the substrate supporting the first catalyst is a silica molecular sieve.

[0018] It should also be noted that in this invention, liquid sodium is first mixed with a solvent to disperse the liquid sodium, thereby reducing its concentration and preventing the hazards associated with excessively high concentrations. Preferably, the solvent is dimethyldiethoxysilane, as it is one of the starting materials of this invention, enabling the dimethylethoxychlorosilane intermediate to exist stably, and dimethyldiethoxysilane has the advantages of good stability and a high boiling point. Using dimethyldiethoxysilane as a solvent results in fewer byproducts after the reaction.

[0019] This invention involves mixing liquid sodium with a solvent, then reacting it with a dimethylethoxychlorosilane intermediate and vinyl chloride in a tubular continuous sodium condensation reactor to undergo a Wurtz reaction. The specific reaction mechanism is as follows: liquid sodium undergoes a single-electron transfer with one molecule of the dimethylethoxychlorosilane intermediate to generate an alkyl radical and sodium chloride. The alkyl radical further reacts with liquid sodium to generate alkyl sodium, which then undergoes a nucleophilic substitution reaction with another molecule of the dimethylethoxychlorosilane intermediate to yield a vinyl monocapped head. Simultaneously, vinyl chloride reacts with liquid sodium to generate an alkyl radical, which further reacts with liquid sodium to generate an alkyl anion. The alkyl anion then reacts with the remaining dimethylethoxychlorosilane intermediate to generate a vinyl monocapped head. Due to the high activation energy of the reaction, this invention controls the sodium condensation reaction at a relatively low temperature.

[0020] Preferably, the flow ratio of dimethylethoxychlorosilane intermediate to vinyl chloride is 1:1; the flow ratio of vinyl chloride to liquid sodium is 1~5.5:1; and the flow ratio of solvent to vinyl chloride is 0.97~5.2:1.

[0021] This invention uses dimethylethoxychlorosilane intermediate as raw material and employs the sodium condensation method to prepare vinyl single-ended heads. The main byproduct, sodium salt, is sodium chloride. The reacted material is homogeneous. During post-processing, ethanol is added to react all unreacted sodium. After solid-liquid separation, a mixture of sodium salt (mainly sodium chloride) and a distillate is obtained. This mixture is then distilled to obtain the vinyl single-ended head.

[0022] Preferably, the specific method for preparing vinyl single-ended heads is as follows: Liquid sodium, dimethylethoxychlorosilane intermediate, and solvent are preheated to 100℃~110℃ respectively; vinyl chloride is preheated to 40℃~50℃; the preheated liquid sodium and preheated solvent are mixed and then reacted with the preheated dimethylethoxychlorosilane intermediate and preheated vinyl chloride in a tubular continuous sodium condensation reactor to undergo a Wurtz reaction. Ethanol is added to the mixture after the reaction is completed for treatment. Through solid-liquid separation, sodium salt with sodium chloride as the main component and a mixed solution are obtained. The mixed solution is then subjected to distillation to obtain vinyl single-ended head.

[0023] Preferably, the conditions for the Wuci reaction are: temperature of 105℃~115℃, time of 2.5min~3.5min, and pressure of 0.5Mpa~1.5Mpa.

[0024] Preferably, the main material of the tubular continuous sodium shrinkage reactor is 316L stainless steel, silicon carbide or Hastelloy; more preferably, the main material of the tubular continuous sodium shrinkage reactor is 316L stainless steel or silicon carbide.

[0025] Preferably, the specific method for preparing vinyl double end caps is as follows: In a continuous tubular reactor, a vinyl single-ended head and a second catalyst are subjected to a continuous hydrolysis reaction to obtain a vinyl double-ended head.

[0026] Preferably, the mass ratio of the vinyl single-ended head to the second catalyst used in the continuous hydrolysis reaction is 1 to 1.6:1.

[0027] The preferred conditions for the continuous hydrolysis reaction are: temperature of 95℃~125℃, pressure of 0.5Mpa~1Mpa, and time of 30s~260s.

[0028] Preferably, the second catalyst used in the continuous hydrolysis reaction is a sodium hydroxide solution, potassium hydroxide solution, sulfuric acid solution, or hydrochloric acid solution; the concentration of the second catalyst used in the continuous hydrolysis reaction is 10wt%~15wt%.

[0029] More preferably, the second catalyst used in the continuous hydrolysis reaction is a sulfuric acid solution. This is because in acid-catalyzed hydrolysis, the sulfuric acid used can be reused indefinitely; however, the water produced by hydrolysis reduces the acid concentration, requiring concentration after several reuses. Continuous catalytic hydrolysis produces only a small amount of water and virtually no other byproducts.

[0030] Compared with the prior art, the present invention has the following technical effects: 1. This invention uses dimethyldiethoxysilane and dimethyldichlorosilane as raw materials. In a tubular fixed-bed catalytic continuous reactor filled with a supported catalyst, the raw materials undergo a nucleophilic substitution reaction under the action of the supported catalyst to generate a dimethylethoxychlorosilane intermediate. Using a sodium condensation method, liquid sodium and solvent are mixed and then reacted with the dimethylethoxychlorosilane intermediate and vinyl chloride in a tubular continuous sodium condensation reactor to undergo a Wurtz reaction. Ethanol is added to the mixture after the reaction is completed for treatment. Through solid-liquid separation, a sodium salt mainly composed of sodium chloride and a mixed liquid are obtained. The mixed liquid is then separated by distillation to obtain a vinyl single-ended head. The vinyl single-ended head is subjected to a continuous hydrolysis reaction to obtain a vinyl double-ended head. This invention solves the technical problem of generating a large amount of sodium ethoxide as a byproduct in the sodium condensation reaction process of existing technologies.

[0031] 2. This invention involves adding ethanol and dimethyldichlorosilane during the post-processing of vinyl single-ended heads, so that the ethanol reacts completely with the unreacted sodium to generate sodium ethoxide, which then reacts with dimethyldichlorosilane to generate the raw material dimethyldiethoxysilane. After solid-liquid separation, a sodium salt mainly composed of sodium chloride and a mixture are obtained. The mixture is then subjected to distillation to obtain vinyl single-ended heads, thereby improving the utilization rate of raw materials.

[0032] 3. This invention uses tubular continuous technology to replace the traditional batch reactor process, which effectively improves the safety of the entire production process. In particular, the tubular continuous sodium condensation reaction technology improves sodium utilization while greatly reducing operational safety risks. Attached Figure Description

[0033] Figure 1 A schematic diagram of the reaction apparatus for preparing vinyl single-ended heads.

[0034] Figure label: 1-Sodium tank; 11-Sodium tank first branch; 12-Sodium tank second branch; 13-Sodium tank third branch; 2-Solvent tank; 3-Vinyl chloride tank; 31-Vinyl chloride tank first branch; 32-Vinyl chloride tank second branch; 4-Dimethylethoxychlorosilane intermediate tank; 5-Tubular continuous sodium condensation reactor; 51-First inlet; 52-Second inlet; 53-Third inlet; 54-Fourth inlet; 6-Material buffering system; 61-Buffer tank; 62-Buffer tank; 63-Buffer tank; 64-Crude product tank; 7-Three-way mixer; 8-Four-way mixer. Detailed Implementation

[0035] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0036] Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0037] like Figure 1 As shown, the reaction apparatus for preparing vinyl single-headed products includes a sodium tank 1, a solvent tank 2, a vinyl chloride tank 3, a dimethylethoxychlorosilane intermediate tank 4, a tubular continuous sodium condensation reactor 5, and a material buffering system 6.

[0038] The outlet of the tubular continuous sodium shrinkage reactor 5 is connected to the material buffer treatment system 6. The tubular continuous sodium shrinkage reactor 5 has four inlets: a first inlet 51, a second inlet 52, a third inlet 53, and a fourth inlet 54. The outlet of the sodium tank 1 is distributed with a first branch 11, a second branch 12, and a third branch 13. The first branch 11 is connected to the first inlet 51 of the tubular continuous sodium shrinkage reactor 5, the second branch 12 is connected to the second inlet 52, and the third branch 13 is connected to the third inlet 53. The first branch 11 is connected to the first inlet 51 of the tubular continuous sodium shrinkage reactor 5 through a three-way mixer 7 and a four-way mixer 8.

[0039] The outlet of solvent tank 2 is connected to the first inlet 51 of tubular continuous sodium condensation reactor 5.

[0040] The outlet of the vinyl chloride tank 3 is distributed with a first branch line 31 and a second branch line 32; the first branch line 31 is connected to the first inlet 51 of the tubular continuous sodium shrinkage reactor 5, and the second branch line 32 is connected to the fourth inlet 54 of the tubular continuous sodium shrinkage reactor 5; the first branch line 31 is connected to the first inlet 51 of the tubular continuous sodium shrinkage reactor 5 through a four-way mixer 8.

[0041] The outlet of the dimethylethoxychlorosilane intermediate tank 4 is connected to the first inlet 51 of the tubular continuous sodium condensation reactor 5.

[0042] The material buffering system 6 includes buffer tank 61, buffer tank 62, buffer tank 63, and crude product tank 64; the inlet of buffer tank 61 is connected to the outlet of the tubular continuous sodium condensation reactor 5, the inlet of buffer tank 62 is connected to the outlet of the tubular continuous sodium condensation reactor 5, and the inlet of buffer tank 63 is connected to the outlet of the tubular continuous sodium condensation reactor 5; the outlet of buffer tank 61 is connected to the crude product tank 64, the outlet of buffer tank 62 is connected to the crude product tank 64, and the outlet of buffer tank 63 is connected to the crude product tank 64.

[0043] Example 1 A method for preparing a vinyl double-ended head includes the following steps: Step 1: Preparation of dimethylethoxychlorosilane intermediate: An aluminum trichloride-supported silica molecular sieve catalyst is filled into a tubular fixed-bed catalytic continuous reactor with an outer diameter of 8 mm, an inner diameter of 6 mm, and a length of 10 m; wherein the tubular fixed-bed catalytic continuous reactor is made of steel lined with PTFE tubing.

[0044] The flow rates of dimethyldichlorosilane and dimethyldiethoxysilane were controlled at 4.8 g / min and 5.63 g / min, respectively. After being mixed in an SK-type static mixer, the mixture was introduced into a tubular fixed-bed catalytic continuous reactor. The reaction temperature of the tubular fixed-bed catalytic continuous reactor was controlled at 25 °C and the residence time was controlled at 25 min to obtain the dimethylethoxychlorosilane intermediate.

[0045] Step 2: Prepare vinyl single-ended heads: The flow rate of dimethyldiethoxysilane in solvent tank 2 is set to 80 kg / h; the flow rate of liquid sodium in sodium tank 1 is set to 15 kg / h, of which the flow rates of sodium tank first branch 11, sodium tank second branch 12 and sodium tank third branch 13 are all 5 kg / h; the flow rate of dimethylethoxychlorosilane intermediate in dimethylethoxychlorosilane intermediate in dimethylethoxychlorosilane tank 4 is set to 36 kg / h; and the flow rate of vinyl chloride in vinyl chloride tank 3 is set to 36 kg / h, of which the flow rates of vinyl chloride tank first branch 31 and vinyl chloride tank second branch 32 are both 18 kg / h.

[0046] The dimethyldiethoxysilane in solvent tank 2 is preheated to 105°C and mixed with liquid sodium in the first branch 11 of sodium tank through a three-way mixer 7. This mixture is then mixed with vinyl chloride in the first branch 31 of vinyl chloride tank (preheated to 45°C) and dimethylethoxychlorosilane intermediate in dimethylethoxysilane intermediate tank 4 (preheated to 105°C), and then mixed through a four-way mixer 8 before entering the tubular continuous sodium shrinkage reactor 5. The tubular continuous sodium shrinkage reactor 5 has an outer diameter of 20 mm, an inner diameter of 15 mm, and a length of 75 m. The temperature of the tubular continuous sodium shrinkage reactor 5 is controlled at 110°C, and the reaction residence time is 3.5 min. Liquid sodium in the second branch 12 and the third branch 13 of sodium tank is introduced into the tubular continuous sodium shrinkage reactor 5. Vinyl chloride in the second branch 32 of vinyl chloride tank is also introduced into the tubular continuous sodium shrinkage reactor 5, and the pressure of the entire reaction system is controlled at 0.8 MPa. The main material of the tubular continuous sodium shrinkage reactor 5 is silicon carbide.

[0047] After the reaction mixture was cooled to 70°C, 35 kg of ethanol and 75 kg of dimethyldichlorosilane were added, and the mixture was stirred for 30 min to remove unreacted sodium, thus obtaining a reaction mixture. The reaction mixture was subjected to solid-liquid separation, and the obtained liquid was distilled to obtain a vinyl single-ended head. The yield of the vinyl single-ended head was 98% based on the dimethylethoxychlorosilane intermediate, and the sodium utilization rate was 80%.

[0048] Step 3: Prepare vinyl double end caps: The flow rate of the vinyl single-ended head and the flow rate of the alkali were both controlled at 72 g / min. The alkali and vinyl single-ended head were introduced into a continuous tubular reactor with an outer diameter of 10 mm, an inner diameter of 8 mm, a high-temperature section of 40 m, and a cooling section of 5 m via a feed pump at a mass ratio of 1:1. The alkali was a 10% sodium hydroxide aqueous solution. The reaction temperature of the continuous tubular reactor was controlled at 95℃, the cooling section temperature at 40℃, the outlet pressure at 0.5 MPa, and the residence time at 240 s, resulting in a vinyl double-ended head. The conversion rate of the vinyl single-ended head was greater than 99%, and the yield of the vinyl double-ended head was greater than 98%.

[0049] Example 2 A method for preparing a vinyl double-ended head includes the following steps: Step 1: Preparation of dimethylethoxychlorosilane intermediate: The intermediate dimethylethoxychlorosilane was prepared according to the method in Example 1, with the difference that the effects of different parameters on the yield of the intermediate were investigated by changing the size of the tubular fixed-bed catalytic continuous reactor, the flow rate of dimethyldichlorosilane, the flow rate of dimethyldiethoxysilane, the reaction temperature, and the residence time. The specific results are summarized in Table 1. Table 1. Yields of dimethylethoxychlorosilane intermediates synthesized under different conditions Note: The dimensions of a tubular fixed-bed catalytic continuous reactor are expressed as the outer diameter - inner diameter - length of the tubular fixed-bed catalytic continuous reactor.

[0050] Step 2, Preparation of vinyl single end caps: Performed according to the method in Example 1.

[0051] Step 3: Preparation of vinyl double end caps: Performed according to the method in Example 1.

[0052] Analysis of the results in Table 1 shows that when the molar ratio of dimethyldichlorosilane to dimethyldiethoxysilane is 1:1, the yield of the dimethylethoxychlorosilane intermediate, calculated as chlorosilane, is 85.4%. This is because excess dimethyldichlorosilane is detrimental to post-processing. Therefore, in this embodiment of the invention, by increasing the amount of dimethyldiethoxysilane, the conversion rate of dimethyldichlorosilane reaches over 98% when the molar ratio of dimethyldiethoxysilane to dimethyldichlorosilane is 1.3:1. In a tubular fixed-bed catalytic continuous reactor with an outer diameter of 8 mm, an inner diameter of 6 mm, and a length of 10 m, increasing the reaction temperature and reducing the reaction residence time have minimal impact on the reaction. By increasing the size of the tubular fixed-bed catalytic continuous reactor, with an outer diameter of 14 mm, an inner diameter of 12 mm, and a length of 10 m, and continuously increasing the flow rates of dimethyldichlorosilane and dimethyldiethoxysilane while shortening the reaction residence time, it was found that under these reactor specifications, the residence time could be shortened to 1 min, and the flow rate of dimethyldichlorosilane could reach 615 g / min, while the flow rate of dimethyldiethoxysilane could reach 575 min, with the yield still maintained at 98%.

[0053] This demonstrates that the reaction process for preparing the dimethylethoxychlorosilane intermediate using dimethyldichlorosilane and dimethyldiethoxysilane as raw materials in this embodiment of the invention is less affected by reaction temperature and residence time. Because excessively high temperatures result in significant fumes from the decomposition of chlorosilane at the outlet, the reaction temperature is controlled below 60°C.

[0054] Example 3 A method for preparing a vinyl double-ended head includes the following steps: Step 1: Preparation of dimethylethoxychlorosilane intermediate: carried out according to the method of Example 1.

[0055] Step 2: Preparation of vinyl single-ended heads: Vinyl single-ended heads were prepared according to the method in Example 1, with the difference that the effects of different parameters on the yield of synthesized vinyl single-ended heads were investigated by changing the size of the tubular continuous sodium condensation reactor, the residence time, and the feeding methods of vinyl chloride and liquid sodium. The specific results are summarized in Table 2. Table 2. Yields of vinyl single-ended heads synthesized under different conditions Note: The dimensions of a tubular continuous sodium condenser are expressed as the outer diameter - inner diameter - length of the tubular continuous sodium condenser.

[0056] Step 3: Preparation of vinyl double end caps: Performed according to the method in Example 1.

[0057] Analysis of the results in Table 2 shows that when neither vinyl chloride nor liquid sodium is fed in batches, the utilization rate of liquid sodium is 40%, and the yield of the vinyl chloride single-ended head is 51%, which is significantly low. When liquid sodium is fed in batches, but vinyl chloride is not fed in batches, the utilization rate of liquid sodium increases significantly to 65%, but the yield of the vinyl chloride single-ended head is 73%, which is still low. When both vinyl chloride and liquid sodium are fed in batches, the conversion rate of liquid sodium increases to over 80%, and the yield of the vinyl chloride single-ended head reaches a maximum of 98%. By expanding the size of the tubular continuous sodium condensation reactor to an outer diameter of 30 mm, an inner diameter of 20 mm, and a length of 100 m, the flow rates of each raw material can be increased to 2.3 times the original flow rates, the residence time is shortened to 2.5 min, the sodium utilization rate is still maintained above 80%, and the product yield can reach 96%.

[0058] This demonstrates that the embodiments of the present invention improve the utilization rate of sodium and the yield of vinyl chloride single-ended heads by designing batch feeding of liquid sodium and vinyl chloride.

[0059] Since some elemental sodium is still present in the reactants after the reaction, ethanol is added to generate sodium ethoxide and hydrogen gas; then dimethyldichlorosilane is added to remove sodium ethoxide and ethanol, generating dimethyldiethoxysilane; the main byproduct obtained is solid sodium chloride, which has a uniform shape and a content of over 98%.

[0060] Example 4 A method for preparing a vinyl double-ended head includes the following steps: Step 1: Preparation of dimethylethoxychlorosilane intermediate: carried out according to the method of Example 1.

[0061] Step 2, Preparation of vinyl single end caps: Performed according to the method in Example 1.

[0062] Step 3: Preparation of vinyl dual-endogen. Vinyl dual-endogen was prepared according to the method in Example 1, with the difference that the effects of different parameters on the yield of the synthesized vinyl dual-endogen were investigated by changing the size of the continuous tubular reactor, the flow rate of the vinyl single-endogen, the flow rate of the alkali, the reaction temperature, the cooling temperature, and the residence time. The specific details are summarized in Table 3. Table 3. Yields of vinyl double-ended heads synthesized under alkaline-catalyzed hydrolysis under different conditions Note: The dimensions of a continuous tubular reactor are expressed as the outer diameter - inner diameter - length of the high-temperature section - length of the cooling section.

[0063] Analysis of the results in Table 3 shows that the amount of alkali has a relatively small effect on the reaction yield. Increasing the reaction temperature and shortening the reaction residence time also have minimal impacts on the yield. When the mass ratio of alkali to vinyl end-capsule is 2.6, the monomer dispersion is more complete, and the reaction is more thorough. When the reaction temperature exceeds 130℃, the vinyl end-capsule is prone to polymerization under alkaline conditions, leading to other side reactions. Furthermore, the alkali solution used in the alkali-catalyzed hydrolysis can be reused 5-6 times.

[0064] Example 5 A method for preparing a vinyl double-ended head includes the following steps: Step 1: Preparation of dimethylethoxychlorosilane intermediate: carried out according to the method of Example 1.

[0065] Step 2, Preparation of vinyl single end caps: Performed according to the method in Example 1.

[0066] Step 3: Preparation of vinyl dual-ends. Vinyl dual-ends were prepared according to the method in Example 1, with the difference that: under acid-catalyzed hydrolysis, the effects of different parameters on the yield of synthesized vinyl dual-ends were investigated by changing the size of the continuous tubular reactor, the flow rate of the vinyl single-end, the flow rate of the acid, the reaction temperature, the cooling temperature, and the residence time. The specific results are summarized in Table 4. Table 4. Yields of vinyl double-ended heads synthesized under acid-catalyzed hydrolysis under different conditions Note: The dimensions of a continuous tubular reactor are expressed as the outer diameter - inner diameter - length of the high-temperature section - length of the cooling section.

[0067] Analysis of the results in Table 4 shows that the yields of acid-catalyzed and base-catalyzed reactions are basically the same. The amount of acid used has a small effect on the reaction yield, and increasing the reaction temperature and shortening the reaction residence time also have a small impact on the yield. When the reaction temperature exceeds 130℃, a polymerization side reaction will occur in the vinyl single-head under acidic conditions. The acid in the acid catalysis can be reused indefinitely. Currently, the acid in the engineered unit has been continuously replenished and reused for 120 days, averaging 4 times per day.

[0068] It should be noted that when numerical ranges are involved in this invention, it should be understood that the two endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described in this invention to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments, and all such changes and modifications fall within the scope of this invention.

[0069] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If these modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a vinyl double-ended head, characterized in that, Includes the following steps: In a tubular fixed-bed catalytic continuous reactor filled with a supported catalyst, dimethyldichlorosilane and dimethyldiethoxysilane undergo a nucleophilic substitution reaction under the action of a supported catalyst to obtain a dimethylethoxychlorosilane intermediate. Liquid sodium is mixed with a solvent and then reacted with dimethylethoxychlorosilane intermediate and vinyl chloride in a tubular continuous sodium condensation reactor to undergo a volcanic reaction. Ethanol is added to the mixture after the reaction is completed for treatment. Through solid-liquid separation, sodium salt with sodium chloride as the main component and a mixture are obtained. The mixture is then subjected to distillation to obtain vinyl single-ended head. A continuous hydrolysis reaction was carried out on the vinyl single end cap to obtain a vinyl double end cap.

2. The method for preparing vinyl double-ended heads according to claim 1, characterized in that, The molar ratio of dimethyldichlorosilane to dimethyldiethoxysilane is 1:1 to 1.

3.

3. The method for preparing vinyl double-ended heads according to claim 1, characterized in that, The temperature range for nucleophilic substitution reactions is 25℃~60℃.

4. The method for preparing vinyl double-ended heads according to claim 1, characterized in that, The supported catalyst is made of a first catalyst and a substrate supporting the first catalyst; wherein the first catalyst accounts for 5% to 10% of the mass percentage of the supported catalyst. The first catalyst is at least one of aluminum trichloride, ferric chloride, boron trifluoride, antimony pentachloride, titanium tetrachloride, and trifluoromethanesulfonate; the substrate supporting the first catalyst is silica molecular sieve, mesoporous molecular sieve, alumina, zeolite, or metal-organic framework material.

5. The method for preparing vinyl double-ended heads according to claim 1, characterized in that, The flow ratio of dimethylethoxychlorosilane intermediate to vinyl chloride is 1:1; The flow rate ratio of vinyl chloride to liquid sodium is 1~5.5:1; The flow rate ratio of solvent to vinyl chloride is 0.97~5.2:

1.

6. The method for preparing vinyl double-ended heads according to claim 1, characterized in that, The solvent is dimethyldiethoxysilane.

7. The method for preparing vinyl double-ended heads according to claim 1, characterized in that, The conditions for the Wuci reaction are: temperature 105℃~115℃, time 2.5min~3.5min, and pressure 0.5Mpa~1.5Mpa.

8. The method for preparing vinyl double-ended heads according to claim 1, characterized in that, The specific method for preparing vinyl single-ended heads is as follows: Liquid sodium, dimethylethoxychlorosilane intermediate, and solvent were preheated to 100°C~110°C; vinyl chloride was preheated to 40°C~50°C. Preheated liquid sodium and preheated solvent are mixed and then reacted with preheated dimethylethoxychlorosilane intermediate and preheated vinyl chloride in a tubular continuous sodium condensation reactor. The mixture is then treated with ethanol and separated by solid-liquid separation to obtain sodium salt and a mixture mainly composed of sodium chloride. The mixture is then separated by distillation to obtain vinyl single-ended head.

9. The method for preparing vinyl double-ended heads according to claim 1, characterized in that, The mass ratio of the vinyl single-ended head to the second catalyst used in the continuous hydrolysis reaction is 1~1.6:1; The second catalyst used in the continuous hydrolysis reaction is a sodium hydroxide solution, potassium hydroxide solution, sulfuric acid solution, or hydrochloric acid solution; the concentration of the second catalyst used in the continuous hydrolysis reaction is 10wt%~15wt%.

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