阅读说明：本技术 一种二甲基乙烯基硅氧基封端的低羟基含量mdt硅油的制备方法 (Preparation method of low-hydroxyl-content MDT silicone oil with end capped by dimethylvinylsiloxy group ) 是由 伍川 王细平 郭世平 方高 瞿志荣 刘川贵 董红 刘清月 张伟伟 于 2020-08-24 设计创作，主要内容包括：本发明涉及有机合成领域,为解决支链结构的MDT硅油分子中硅羟基含量高引起的硅油储存稳定性差及作为离型剂组分时与铂金催化剂反应释放出气体导致离型剂存在气泡,影响离型剂固化速率及品质的问题,本发明提出一种采取反应精馏法制备二甲基乙烯基硅氧基封端的低羟基含量MDT硅油的方法,制备的二甲基乙烯基硅氧基封端的MDT硅油残留的硅羟基含量低,硅油分子量分布均匀,制备过程工艺简单,便于大规模生产。(The invention relates to the field of organic synthesis, and aims to solve the problems that the storage stability of silicone oil is poor due to the high content of silicon hydroxyl in MDT silicone oil molecules with a branched chain structure, and the curing rate and quality of a release agent are influenced by bubbles in the release agent caused by gas released by reaction with a platinum catalyst when the MDT silicone oil molecules are used as the release agent components.)

1. A preparation method of low-hydroxyl-content MDT silicone oil blocked by dimethylvinylsiloxy is characterized by comprising the following steps:

(1) adding 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane into a reaction vessel and maintaining the temperature at 15-60 ℃; dropwise adding a hydrochloric acid solution into a reaction container, keeping the temperature at 10-105 ℃ after dropwise adding, reacting for 0.1-10.0 h, and then standing for layering;

(2) adding methyltrimethoxysilane and toluene into another reaction vessel, stirring and maintaining the temperature of the system at a certain temperature;

(3) dropwise adding a part of the upper-layer solution obtained in the step (1) into the reaction container in the step (2) under stirring; after the dropwise addition is finished, completely dropwise adding the lower layer solution obtained in the step (1) into a reaction container; finally, dropwise adding the residual upper layer solution in the step (1) into a reaction container; heating the mixture in the reaction vessel;

(4) putting the product obtained in the step (3) into a rectifying tower, heating, rectifying at normal pressure, and stopping normal-pressure rectification until no methanol exists in the distillate; and then washing or neutralizing the rectifying still substrate to be neutral, standing for layering, desalting, filtering, layering, transferring an oil phase into a rectifying tower, heating at normal pressure to remove water in the system, then carrying out reduced pressure distillation on the still residual liquid, removing low-boiling-point substances, and then cooling to room temperature to obtain the low-hydroxyl-content MDT silicone oil terminated by the dimethylvinylsiloxy group.

2. The method of claim 1, wherein the dimethylvinylsiloxy terminated low hydroxyl content MDT silicone oil has the following structural formula:

wherein a is 1, b is 0.50 to 2.00, c is 0.05 to 0.40, and d is 0.005 to 0.10.

3. The method for preparing the dimethylvinylsiloxy terminated low hydroxyl content MDT silicone oil according to claims 1 and 2, characterized in that the molar ratio of HCl to 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane in the hydrochloric acid solution in step (1) is 0.05 to 0.90: 1, the dripping time of the hydrochloric acid solution is 0.25-5.0 h.

4. The method for preparing the dimethylvinylsiloxy terminated low hydroxyl content MDT silicone oil as claimed in claims 1 and 2, characterized in that the molar ratio of methyltrimethoxysilane to 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane in step (2) is 0.5-2.5: 1.

5. the process for the preparation of dimethylvinylsiloxy terminated low hydroxyl content MDT silicone oil according to claims 1 and 2, characterized in that the temperature maintained in step (2) is comprised between 15 and 70 ℃.

6. The method for preparing the dimethylvinylsiloxy-terminated low-hydroxyl-content MDT silicone oil as claimed in claims 1 and 2, wherein the addition amount of the first upper solution in the step (3) is 0.05-0.95 of the mass or volume concentration of the reaction system in the step (2), the addition time is 0.1-10.0 h, the addition time of the lower acidic aqueous solution is 0.1-10.0 h, and the addition time of the remaining upper solution is 0.1-10.0 h.

7. The method for preparing the dimethylvinylsiloxy terminated MDT silicone oil with low hydroxyl content according to claims 1 and 2, characterized in that the temperature is kept between 15 ℃ and 109 ℃ after the dropwise addition in the step (3), and the reaction time is 0.1 to 12 hours.

8. The method for preparing dimethylvinylsiloxy terminated low hydroxyl content MDT silicone oil according to claims 1 and 2, characterized in that the rectifying still bottoms washing solution in step (4) is a saturated brine.

9. The method for preparing dimethylvinylsiloxy-terminated low hydroxyl content MDT silicone oil according to claims 1 and 2, characterized in that the neutralizing agent of the rectifier bottom in step (4) is selected from one or more of powdered sodium carbonate, powdered sodium bicarbonate, powdered potassium carbonate, powdered potassium bicarbonate, powdered sodium dihydrogen phosphate, powdered disodium hydrogen phosphate, powdered sodium phosphate, powdered potassium dihydrogen phosphate, powdered dipotassium hydrogen phosphate, powdered potassium phosphate, saturated solution of sodium carbonate, saturated solution of sodium hydrogen carbonate, saturated solution of potassium bicarbonate, saturated solution of sodium dihydrogen phosphate, saturated solution of disodium hydrogen phosphate, saturated solution of sodium phosphate, saturated solution of potassium dihydrogen phosphate, saturated solution of dipotassium hydrogen phosphate, and saturated solution of potassium phosphate.

10. The method for preparing the dimethylvinylsiloxy-terminated low-hydroxyl-content MDT silicone oil according to claims 1 and 2, characterized in that the reduced pressure distillation pressure in the step (4) is between-0.0800 and-0.0999 MPa, and the temperature is between 150 and 250 ℃.

Technical Field

The invention relates to the field of organic synthesis, in particular to a method for preparing low-hydroxyl-content MDT silicone oil with a dimethyl vinyl siloxane-terminated end by adopting a reactive distillation coupling method.

Background

The MDT silicone oil is branched silicone oil, which is liquid polyorganosiloxane containing polyorganosiloxane branched chains formed by introducing trifunctional chain links as branch points into linear silicone oil molecular chains. The winding degree of a branched chain silicone oil molecular chain is larger than that of linear polydimethylsiloxane due to the existence of a branched chain structure in a molecule, and the viscosity of the branched chain silicone oil is reduced under the action of a shearing force, namely, the branched chain silicone oil has a shear thinning effect and belongs to non-Newtonian fluid. At present, the branched silicone oil is widely used in the fields of cosmetics, paper anti-sticking release agents, hydraulic transmission oil, defoaming agents and the like.

Compared with linear polydimethylsiloxane, the MDT silicone oil has better compatibility with various cosmetics and is not easy to be polluted by sebum, and the cosmetics prepared by taking the MDT silicone oil as the main component have good cosmetic persistence, excellent smooth feeling and cleaning effect and comfortable skin touch feeling, and can be used in products such as skin care products, hair care products, antiperspirants, color cosmetics, sun protection products and the like.

The paper release agent is one of the main application fields of linear silicone oil, and is usually cured by adopting a hydrosilylation mode, and the curing speed is a key factor influencing the production efficiency of the paper release agent. Compared with the addition type release agent prepared by adopting the linear vinyl silicone oil, the addition type anti-sticking release agent prepared by adopting the MDT silicone oil containing vinyl has lower curing temperature and lower mobility. The solvent-free addition type anti-sticking isolating agent prepared from MDT silicone oil with a branched chain and an end capping both containing a vinyl structure and a longer chain link of the branched chain can be cured after 21 seconds at 100 ℃, and the solvent-free addition type anti-sticking isolating agent prepared from MDT silicone oil with a branched chain link of a short length and a branched chain and an end capping both containing a vinyl structure can be cured after 20 seconds at 120 ℃.

The branched chain structure in the MDT silicone oil molecule can also inhibit the crystallization tendency of the linear dimethyl silicone oil at low temperature and reduce the glass transition temperature of the silicone oil, for example, the pour point of the linear dimethyl silicone oil is usually between-65 ℃ and-50 ℃, while the pour point of the branched chain dimethyl MDT silicone oil can be as low as-90 ℃ to-85 ℃, so that the branched chain dimethyl MDT silicone oil can be used as low-temperature resistant hydraulic transmission oil and brake oil, and the low-temperature use range and the application field of the dimethyl silicone oil are further expanded.

Although the dimethyl silicone oil is widely applied to the defoaming field, when the branched chain MDT silicone oil is used for preparing the defoaming agent, the defoaming effect and the defoaming durability of the branched chain MDT silicone oil are superior to those of common linear dimethyl silicone oil, and particularly, the defoaming effect of the branched chain MDT silicone oil is better for a high-shear foaming system.

From the aspect of molecular structure, the MDT silicone oil with a branched structure introduces a branch, namely a T chain link, into a dimethyl silicone oil molecule with a linear structure, namely has three functionalities capable of participating in reaction. The introduction of T chain easily causes the cross-linking polymerization of silicon oil molecules during the reaction process, leading to the occurrence of gelation phenomenon, or reducing the storage stability of the product. According to the source of T chain links, the current method for preparing the dimethyl MDT silicone oil with the branched chain structure comprises the following steps: (1) using methyl trichlorosilane as a T chain link source; (2) methyl trimethoxy silane is used as a T chain link source; (3) alkyl trialkoxy silane is used as a T chain link source; (4) 1, 1, 1, 3, 5, 7, 7, 7-octamethyl-3, 5-dihydroxy-tetrasiloxane (MHTS) is used as a T chain link source; (5) polymethyl hydrogen siloxane is used as a T chain link source.

In order to solve the problem of gelation in the preparation of branched silicone oil, the chinese patent CN 102329427 discloses a preparation method of branched silicone oil (MDT), which comprises the steps of firstly carrying out alcohol hydrolysis on a chlorosilane mixture to prepare low-viscosity alkoxy silicone oil, then carrying out hydrolysis neutralization on the low-viscosity alkoxy silicone oil, removing low boiling point to obtain low-viscosity and high-viscosity branched silicone oil (MDT), thereby avoiding the gelation of T group, improving the yield, and increasing the viscosity of the branched silicone oil without adding DMC or silicone oil for telomerization.

Chinese patent CN 105524280 discloses another method for preparing branched silicone oil, which is firstly prepared by dimethyl cyclosiloxane hospital (D)₄Or DMC), tetramethyltetravinylcyclotetrasiloxane (D)₄ ^Vi) And a chain terminator is used for preparing vinyl silicone oil through an alkali-catalyzed equilibrium reaction, and then the vinyl silicone oil and heptamethyltrisiloxane are used for preparing branched silicone oil through a hydrosilylation reaction. Chinese patent CN 105669981 also discloses a preparation method of branched silicone oil, after siloxane, silsesquioxane and hexamethylsiloxane are mixed, potassium hydroxide is added, stirring is maintained at 100-150 ℃ until the silsesquioxane is completely dissolved, then cooling to room temperature, adding an end capping agent to terminate the reaction, filtering and distilling to obtain the branched silicone oil, the method overcomes the defects of complex process, environmental pollution and poor process repeatability in the traditional preparation process of the branched silicone oil, meanwhile, the content of branched chains in the silicone oil can be accurately controlled, a series of branched chain type silicone oil with controllable viscosity can be prepared by adding different contents of silsesquioxane and hexamethylsiloxane, the prepared silicone oil has the characteristics of controllable viscosity, good low-temperature performance, low production cost, simple process and the like, the traditional silicone oil preparation process can be greatly improved, and the method can be widely applied to the fields of aviation and other machinery.

Although various methods for preparing branched MDT silicone oil are disclosed in the patent literature, the influence of residual silicon hydroxyl groups in the molecules of the branched MDT silicone oil and silicon hydroxyl groups on the storage stability of the branched silicone oil and the performance of downstream products is less reported, as is well known to those skilled in the art, the branched MDT silicone oil is easy to condense due to the existence of the silicon hydroxyl groups, particularly, when the temperature is raised, the branched MDT silicone oil is easily depolymerized due to the 'back biting' of the hydroxyl groups, and the storage stability of the branched silicone oil and the performance of the downstream products are seriously influenced.

Disclosure of Invention

In order to solve the problems of poor storage stability of the silicone oil caused by high content of silicon hydroxyl in MDT silicone oil molecules with a branched chain structure and the influence on curing rate and quality of a release agent due to the fact that the release agent has bubbles caused by reaction with a platinum catalyst to release gas when being used as the release agent component, the invention provides a preparation method of the low-hydroxyl-content MDT silicone oil with the dimethyl vinyl siloxane-terminated end.

The structural formula of the low-hydroxyl-content MDT silicone oil with the end capped by the dimethylvinylsiloxy group is shown as follows:

wherein a is 1, b, c and d each represents [ CH ]₃SiO_3/2]Chain link, [ CH ]₃(CH₃O)SiO_2/2]Chain links and [ CH₃(OH)SiO_2/2]Chain link to end capping group [ CH₂＝CH(CH₃)₂SiO_1/2]The mole fraction of mer; b is 0.50-2.00, c is 0.05-0.40, and d is 0.005-0.10; relative to a polydimethylsiloxane standard sample, the number average molecular weight (Mn) of the prepared dimethylvinylsiloxy terminated low-hydroxyl-content MDT silicone oil is 400-1000, and the polydispersity index (PDI) is 1.10-1.50.

The invention is realized by the following technical scheme: the preparation method of the low-hydroxyl-content MDT silicone oil with the end capped by the dimethylvinylsiloxy group comprises the following steps:

(1) adding 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane into a reaction vessel and maintaining the temperature at 15-60 ℃; dropwise adding a hydrochloric acid solution into a reaction container, keeping the temperature at 10-105 ℃ after dropwise adding, reacting for 0.1-10.0 h, and then preferably standing and layering at room temperature;

hydrochloric acid is used as a catalyst to catalyze the hydrolysis reaction of 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane and the subsequent condensation reaction. The molar ratio of the effective component HCl to the 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane in the hydrochloric acid aqueous solution is 0.05-0.90: 1, and the dripping time of the hydrochloric acid solution is 0.25-5.0 h.

Preferably, the 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane is maintained at a temperature of 25 to 50 ℃, the ratio of the amount of the effective component (HCl) to the amount of the 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane in hydrochloric acid is preferably 0.075 to 0.25: 1, the dripping time of the hydrochloric acid is preferably 1.0 to 3.0 hours, the reaction temperature of the 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane and the aqueous solution of the hydrochloric acid is preferably 55 to 80 ℃, and the reaction time is preferably 2.0 to 5.0 hours.

Because 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane is oily, and the aqueous solution of hydrochloric acid is aqueous, the dimethyl vinyl silanol generated by hydrolysis has partial solubility in the aqueous phase and partial solubility in the oil phase, the reaction starts to be layered, the reaction is layered as the reaction proceeds, the phenomenon of no significant layering (slight emulsification) occurs when the temperature is too high, the emulsification phenomenon disappears after the temperature is reduced to room temperature, the materials are layered into a lower aqueous phase (acidity) and an upper oil phase, and the oil phase is mainly dimethyl vinyl silanol.

(2) Adding methyltrimethoxysilane and toluene into another reaction vessel, stirring and maintaining the temperature of the system at a certain temperature;

the molar ratio of the methyltrimethoxysilane to the 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane is 0.5-2.5: 1, preferably 0.75-1.25: 1.

The system is kept at a temperature of 15-70 ℃, preferably 25-50 ℃.

Toluene acts as a solvent and is used in an amount to dissolve the solute, preferably, the molar ratio of toluene to 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane is 0.25 to 5.0: 1, more preferably 0.5 to 1.5: 1.

(3) Dropwise adding a part of the upper-layer solution obtained in the step (1) into the reaction container in the step (2) under stirring; after the dropwise addition is finished, completely dropwise adding the lower layer solution obtained in the step (1) into a reaction container; finally, dropwise adding the residual upper layer solution in the step (1) into a reaction container; heating the mixture in the reaction vessel;

the adding amount of the first upper layer solution is 0.05-0.95 of the mass or volume concentration of the reaction system in the step (2), the adding time is 0.1-10.0 h, the adding time of the lower layer acidic aqueous solution is 0.1-10.0 h, the adding time of the rest upper layer solution is 0.1-10.0 h, preferably, the mass fraction or volume fraction of the part upper layer solution is 0.25-0.75, and the adding time is 0.5-4.0 h; the dripping time of the lower-layer acidic aqueous solution is 0.5-4.0 h; and the dripping time of the residual upper-layer part solution is 0.5-4.0 h.

After dropwise adding, keeping the temperature at 15-109 ℃ and the reaction time at 0.1-12 h, preferably, the reaction temperature of the reaction mixture is 50-100 ℃ and the reaction time is 0.5-6.0 h.

The solubility of the oil phase dimethyl vinyl silanol in the step (1) in toluene is increased, the acidic aqueous solution in the water phase catalyzes methyl trimethoxy silane to hydrolyze to generate methyl trisilol, and the methyl trisilol migrates to toluene due to high solubility in toluene and condenses with the dimethyl vinyl silanol to obtain MDT silicone oil. (4) Putting the product obtained in the step (3) into a rectifying tower, heating, rectifying at normal pressure, distilling out by-products such as methanol and the like, monitoring the components and the composition of the distillate by adopting GC and GC-MS (gas chromatography-mass spectrometer), and stopping the normal-pressure rectification until no methanol exists in the distillate; and then washing or neutralizing the distillation kettle substrate to be neutral, standing for layering, desalting, filtering, layering, transferring an oil phase into a distillation tower, heating at normal pressure, removing water in a system by using an azeotrope formed by toluene and water, then carrying out reduced pressure distillation on kettle residual liquid, removing low-boiling-point substances, and cooling to room temperature to obtain the low-hydroxyl-content MDT silicone oil terminated by the dimethylvinylsiloxy group.

The rectification kettle substrate washing solution is saturated salt solution, and the using amount of the rectification kettle substrate washing solution is 1.0-15 times of the volume of the rectification kettle substrate; preferably 3-8 times of the volume of the rectifying still substrate.

The neutralizing agent of the rectifying still substrate is selected from one or more of powdered sodium carbonate, powdered sodium bicarbonate, powdered potassium carbonate, powdered potassium bicarbonate, powdered sodium dihydrogen phosphate, powdered disodium hydrogen phosphate, powdered sodium phosphate, powdered potassium dihydrogen phosphate, powdered dipotassium hydrogen phosphate, powdered potassium phosphate, saturated solution of sodium carbonate, saturated solution of sodium bicarbonate, saturated solution of potassium carbonate, saturated solution of potassium bicarbonate, saturated solution of sodium dihydrogen phosphate, saturated solution of disodium hydrogen phosphate, saturated solution of sodium phosphate, saturated solution of potassium dihydrogen phosphate, saturated solution of dipotassium hydrogen phosphate and saturated solution of potassium phosphate, and preferably at least one of powdered sodium carbonate, powdered sodium bicarbonate, saturated solution of sodium carbonate and saturated solution of sodium bicarbonate;

the pressure (gauge pressure) for removing low-boiling-point substances by reduced pressure distillation is-0.0800 to-0.0999 MPa, the temperature is 150 to 250 ℃, preferably-0.090 to-0.099 MPa, and the temperature is preferably 180 to 220 ℃.

The dimethyl vinyl siloxy terminated MDT silicone oil prepared by the reactive distillation coupling method has low hydroxyl content, and when the dimethyl vinyl siloxy terminated MDT silicone oil is used as an addition type release agent component, the curing speed is high, and bubbles are not generated.

Compared with the prior art, the invention has the beneficial effects that:

(1) the prepared dimethylvinylsiloxy terminated MDT silicone oil has low residual silicon hydroxyl content and uniform molecular weight distribution;

(2) the preparation process is simple and is suitable for large-scale industrial production;

drawings

FIG. 1 is a sample of a branched silicone oil of the dimethylvinylsiloxy terminated MDT type prepared in example 3¹H NMR spectrum.

Detailed Description

The present invention is further illustrated by the following examples and figures, which are not intended to limit the scope of the invention, and the starting materials used in the examples are commercially available or can be prepared by conventional methods.

Example 1

(1) 727.20g (3.90mo1) of 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane is added into a 3000mL three-neck flask provided with a stirring device, a thermometer and a reflux condenser pipe at normal temperature, the temperature is raised to 35 ℃ under stirring, then a mixed solution of 702.00g (39.0mol) of deionized water and 62.88g (0.637mol) of concentrated HCl with the concentration of 37 percent, which are mixed in advance, is dropwise added into a reaction container through a constant-pressure dropping funnel at constant speed for 2 hours, and after the dropwise addition is finished, the temperature of reactants is raised to 70 ℃ and the reactants react for 3 hours at the temperature. After the reaction is finished, cooling to room temperature, and obtaining an upper layer and a lower layer of reaction products;

(2) 531.60g (3.90mol) of methyltrimethoxysilane and 314.40g of toluene are added into another 5000mL three-neck flask which is provided with a stirring device, a thermometer and a reflux condenser tube, and the temperature of the system is maintained at 30 ℃ after uniform stirring;

(3) 1/2 (volume) of the upper solution obtained in the step (1) is put into a constant pressure dropping funnel and is dripped into a mixed solution consisting of methyltrimethoxysilane and toluene at a constant speed for 3 hours; after the dropwise addition is finished, dropwise adding all the lower-layer acidic aqueous solution obtained in the step (1) into a reaction container at a constant speed for 2 hours; after the dropwise addition of the acidic aqueous solution is finished, dropwise adding the residual upper-layer solution into the reaction container at a constant speed for 2 hours. After the addition was complete, the reaction mixture was warmed to 70 ℃ with stirring and maintained at this temperature for 2 h.

(4) And (3) after the reaction in the step (3) is finished, transferring the obtained product to a normal pressure rectifying tower, controlling the temperature at the top of the tower to be less than or equal to 68 ℃, firstly distilling out by-products such as methanol and the like, simultaneously measuring the composition of the distillate by adopting GC and GC-MS, and stopping the normal pressure rectifying when the distillate does not contain the methanol. And cooling the rectifying still substrate to room temperature, and adding saturated salt water which is 5 times of the total volume of the rectifying still residual liquid in batches for washing until the pH value of the rectifying still residual liquid is between 6 and 7. And transferring the kettle residual liquid which is washed and is deprived of saturated salt water to a rectifying tower, firstly heating up and rectifying under normal pressure to deprive a toluene-water azeotrope and residual toluene components, then gradually heating up to 190 ℃ under-0.098 MPa, and then cooling to room temperature after depriving residual low-boiling-point substances, thus obtaining 387.0g of the low-hydroxyl-content MDT silicone oil of the dimethylvinylsiloxy end capping.

Example 2

(1) 727.20g (3.90mol) of 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane is added into a 3000mL three-neck flask provided with a stirring device, a thermometer and a reflux condenser pipe at normal temperature, the temperature is raised to 45 ℃ under stirring, then a mixed solution consisting of 702.00g (39.0mol) of deionized water and 62.88g (0.637mol) of concentrated HCl with the concentration of 37 percent, which are mixed in advance, is dripped into a reaction vessel at constant speed for 2.5h through a constant pressure dropping funnel, and after the dripping is finished, the temperature of reactants is raised to 70 ℃ and the reactants react for 3h at the temperature. After the reaction is finished, cooling to room temperature, and obtaining an upper layer and a lower layer of reaction products;

(2) 531.60g (3.90mol) of methyltrimethoxysilane and 314.40g of toluene are added into another 5000mL three-neck flask which is provided with a stirring device, a thermometer and a reflux condenser tube, and the temperature of the system is maintained at 40 ℃ after uniform stirring;

(3) 1/2 in the volume of the upper solution obtained in the step (1) is put into a constant pressure dropping funnel and is dripped into a mixed solution consisting of methyltrimethoxysilane and toluene at a constant speed for 2 hours; after the dropwise addition is finished, dropwise adding all the lower-layer acidic aqueous solution obtained in the step (1) into a reaction container at a constant speed for 2 hours; after the dropwise addition of the acidic aqueous solution is finished, dropwise adding the residual upper-layer solution into the reaction container at a constant speed for 2 hours. After the upper layer solution and the lower layer solution obtained in the step (1) are dropwise added according to the method, heating the reaction mixture to 70 ℃ under stirring and maintaining the temperature for 3 hours;

(4) and (3) after the reaction in the step (3), transferring the obtained product to a normal pressure rectifying tower, controlling the temperature at the top of the tower to be less than or equal to 68 ℃, firstly distilling out by-products such as methanol and the like, simultaneously measuring the composition of the distillate by adopting GC and GC-MS, and stopping the normal pressure rectifying when the distillate does not contain the methanol. And cooling the rectifying still substrate to room temperature, and adding saturated salt water which is 8 times of the total volume of the rectifying still residual liquid in batches for washing until the pH value of the rectifying still residual liquid is between 6 and 7. And transferring the kettle residual liquid which is washed and is subjected to saturated salt water removal to a rectifying tower, heating and rectifying under normal pressure to remove a toluene-water azeotrope and the residual toluene component, gradually heating to 195 ℃ under-0.099 MPa, removing residual low-boiling-point substances, and cooling to room temperature to obtain 438.0g of the low-hydroxyl-content MDT silicone oil of the dimethylvinylsiloxy end capping.

Example 3

(1) 181.80g (0.975mol) of 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane is added into a 1000mL three-neck flask provided with a stirring device, a thermometer and a reflux condenser pipe at normal temperature, the temperature is raised to 30 ℃ under stirring, then a mixed solution of 175.50g (9.75mol) of deionized water and 15.72g (0.159mol) of concentrated HCl with the concentration of 37 percent, which are mixed in advance, is dropwise added into a reaction container through a constant pressure dropping funnel at a constant speed for 0.75h, and after the dropwise addition is finished, the temperature of reactants is raised to 65 ℃ and the reactants react for 4h at the temperature. After the reaction is finished, cooling to room temperature, and obtaining an upper layer and a lower layer of reaction products;

(2) adding 132.90g (0.976mol) of methyltrimethoxysilane and 78.60g of toluene into another 1000mL three-neck flask which is provided with a stirring device, a thermometer and a reflux condenser pipe, and maintaining the temperature of the system at 25 ℃ after uniform stirring;

(3) 2/3 in the upper solution obtained in the step (1) is put into a constant pressure dropping funnel and is dripped into a mixed solution consisting of methyltrimethoxysilane and toluene at a constant speed for 2 hours; after the dropwise addition is finished, dropwise adding all the lower-layer acidic aqueous solution obtained in the step (1) into a reaction container at a constant speed for 1 h; after the dropwise addition of the acidic aqueous solution is finished, the residual upper-layer solution is dropwise added into the reaction container at a constant speed for 1.5 h. After the upper layer solution and the lower layer solution obtained in the step (1) are dropwise added according to the method, heating the reaction mixture to 75 ℃ under stirring and maintaining the temperature for 4 hours;

(4) and (3) after the reaction in the step (3), transferring the obtained product to a normal pressure rectifying tower, controlling the temperature at the top of the tower to be less than or equal to 68 ℃, firstly distilling out by-products such as methanol and the like, simultaneously measuring the composition of the distillate by adopting GC and GC-MS, and stopping the normal pressure rectifying when the distillate does not contain the methanol. And cooling the rectifying still substrate to room temperature, and adding saturated salt water which is 4 times of the total volume of the rectifying still residual liquid in batches for washing until the pH value of the rectifying still residual liquid is between 6 and 7. And transferring the kettle residual liquid which is washed and is subjected to saturated salt water removal to a rectifying tower, heating and rectifying under normal pressure to remove a toluene-water azeotrope and the residual toluene component, gradually heating to 195 ℃ under-0.099 MPa, removing residual low-boiling-point substances, and cooling to room temperature to obtain 77.40g of the low-hydroxyl-content MDT silicone oil with the end capped by the dimethylvinylsiloxy group.

Example 4

(1) 838.80g (4.50mol) of 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane is added into a 3000mL three-neck flask provided with a stirring device, a thermometer and a reflux condenser pipe at normal temperature, the temperature is raised to 25 ℃ under stirring, then a mixed solution consisting of 405.00g (22.5mol) of deionized water and 62.88g (0.637mol) of concentrated HCl with the concentration of 37 percent, which are mixed in advance, is dropwise added into a reaction vessel through a constant-pressure dropping funnel at constant speed for 3 hours, and after the dropwise addition is finished, the temperature of reactants is raised to 60 ℃ and the reactants react for 5 hours at the temperature. After the reaction is finished, cooling to room temperature, and obtaining an upper layer and a lower layer of reaction products;

(2) 490.39g (3.60mol) of methyltrimethoxysilane and 558.90g of toluene are added into another 5000mL three-neck flask which is provided with a stirring device, a thermometer and a reflux condenser tube, and the temperature of the system is maintained at 25 ℃ after uniform stirring;

(3) 1/4 mass in the upper layer solution obtained in the step (1) is put into a constant pressure dropping funnel and is dripped into a mixed solution consisting of methyltrimethoxysilane and toluene at a constant speed for 0.5 h; after the dropwise addition is finished, dropwise adding all the lower-layer acidic aqueous solution obtained in the step (1) into a reaction container at a constant speed for 4 hours; after the dropwise addition of the acidic aqueous solution is finished, dropwise adding the residual upper-layer solution into the reaction container at a constant speed for 4 hours. After the upper layer solution and the lower layer solution obtained in the step (1) are dropwise added according to the method, heating the reaction mixture to 60 ℃ under stirring and maintaining the temperature for 6 hours;

(4) and (3) after the reaction in the step (3), transferring the obtained product to a normal pressure rectifying tower, controlling the temperature at the top of the tower to be less than or equal to 68 ℃, firstly distilling out by-products such as methanol and the like, simultaneously measuring the composition of the distillate by adopting GC and GC-MS, and stopping the normal pressure rectifying when the distillate does not contain the methanol. And cooling the rectifying still substrate to room temperature, and adding saturated salt water which is 8 times of the total volume of the rectifying still residual liquid in batches for washing until the pH value of the rectifying still residual liquid is between 6 and 7. And transferring the kettle residual liquid which is washed and is subjected to saturated salt water removal to a rectifying tower, heating and rectifying under normal pressure to remove a toluene-water azeotrope and the residual toluene component, then gradually heating to 205 ℃ under-0.095 MPa, removing residual low-boiling-point substances, and then cooling to room temperature to obtain 425.0g of the dimethylvinylsiloxy terminated MDT silicone oil with low hydroxyl content.

Example 5

(1) 932.00g (5.00mol) of 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane is added into a 3000mL three-neck flask provided with a stirring device, a thermometer and a reflux condenser pipe at normal temperature, the temperature is raised to 50 ℃ under stirring, then a mixed solution consisting of 1350.00g (75.0mol) of deionized water and 42.00g (0.426mol) of concentrated HCl with the concentration of 37 percent, which are mixed in advance, is dropwise added into a reaction vessel through a constant-pressure dropping funnel at a constant speed for 1.5h, and after the dropwise addition is finished, the temperature of reactants is raised to 75 ℃ and the reactants react for 2.5h at the temperature. After the reaction is finished, cooling to room temperature, and obtaining an upper layer and a lower layer of reaction products;

(2) 817.32g (6.0mol) of methyltrimethoxysilane and 460g of toluene are added into another 5000mL three-neck flask which is provided with a stirring device, a thermometer and a reflux condenser tube, and the temperature of the system is maintained at 45 ℃ after uniform stirring;

(3) 3/4 (volume) in the upper solution obtained in the step (1) is put into a constant pressure dropping funnel and is dripped into a mixed solution consisting of methyltrimethoxysilane and toluene at a constant speed for 3.5 h; after the dropwise addition is finished, dropwise adding all the lower-layer acidic aqueous solution obtained in the step (1) into a reaction container at a constant speed for 3 hours; after the dropwise addition of the acidic aqueous solution is finished, the residual upper-layer solution is dropwise added into the reaction container at a constant speed for 0.5 h. After the upper layer solution and the lower layer solution obtained in the step (1) are dropwise added according to the method, heating the reaction mixture to 90 ℃ under stirring and maintaining the temperature for 3 hours;

(4) and (3) after the reaction in the step (3), transferring the obtained product to a normal pressure rectifying tower, controlling the temperature at the top of the tower to be less than or equal to 68 ℃, firstly distilling out by-products such as methanol and the like, simultaneously measuring the composition of the distillate by adopting GC and GC-MS, and stopping the normal pressure rectifying when the distillate does not contain the methanol. And cooling the rectification kettle substrate to room temperature, and adding powdered sodium bicarbonate in batches for neutralization until the pH value of the kettle residual liquid is between 6 and 7. And transferring the residue after filtering and desalting to a rectifying tower, heating and rectifying at normal pressure to remove a toluene-water azeotrope and the residual toluene component, gradually heating to 210 ℃ under-0.092 MPa, removing residual low-boiling-point substances, and cooling to room temperature to obtain 709.0g of the dimethylvinylsiloxy terminated MDT silicone oil with low hydroxyl content.

Example 6

(1) 559.20g (3.00mol) of 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane is added into a 3000mL three-neck flask provided with a stirring device, a thermometer and a reflux condenser pipe at normal temperature, the temperature is raised to 40 ℃ under stirring, then a mixed solution consisting of 1263.60g (75.0mol) of deionized water and 62.88g (0.637mol) of concentrated HCl with the concentration of 37 percent, which are mixed in advance, is dropwise added into a reaction vessel through a constant-pressure dropping funnel at a constant speed for 2 hours, and after the dropwise addition is finished, the temperature of reactants is raised to 60 ℃ and the reactants react for 4 hours at the temperature. After the reaction is finished, cooling to room temperature, and obtaining an upper layer and a lower layer of reaction products;

(2) 368.80g (2.7mol) of methyltrimethoxysilane and 179.4g of toluene are added into another 5000mL three-neck flask which is provided with a stirring device, a thermometer and a reflux condenser, and the temperature of the system is maintained at 40 ℃ after uniform stirring;

(3) 40 percent of the upper layer solution obtained in the step (1) is filled into a constant pressure dropping funnel and is dripped into a mixed solution consisting of methyltrimethoxysilane and toluene at a constant speed for 2.5 hours; after the dropwise addition is finished, dropwise adding all the lower-layer acidic aqueous solution obtained in the step (1) into a reaction container at a constant speed for 2.5 hours; after the dropwise addition of the acidic aqueous solution is finished, dropwise adding the residual upper-layer solution into the reaction container at a constant speed for 3 hours. After the upper layer solution and the lower layer solution obtained in the step (1) are dropwise added according to the method, heating the reaction mixture to 80 ℃ under stirring and maintaining the temperature for 4 hours;

(4) and (3) after the reaction in the step (3), transferring the obtained product to a normal pressure rectifying tower, controlling the temperature at the top of the tower to be less than or equal to 68 ℃, firstly distilling out by-products such as methanol and the like, simultaneously measuring the composition of the distillate by adopting GC and GC-MS, and stopping the normal pressure rectifying when the distillate does not contain the methanol. Cooling a rectifying still substrate to room temperature, adding a sodium carbonate saturated solution in batches for neutralization until the pH of the still residual liquid is between 6 and 7, filtering to remove salt, layering filtrate, transferring an oil phase layer into a rectifying tower, heating to rectify and remove a toluene-water azeotrope and the residual toluene component at normal pressure, gradually heating to 200 ℃ under-0.097 MPa, removing residual low-boiling-point substances, and cooling to room temperature to obtain 473.0g of the low-hydroxyl-content MDT silicone oil with the end capped dimethylvinylsiloxy group.

Comparative example 1

27.94g (0.15mol) of 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane, 19.41g (0.143mol) of methyltrimethoxysilane, 10.40g (0.58mol) of deionized water and 2.37g (0.024mol) of a 37% HCl solution are added into a 250mL three-neck flask equipped with a magnetic stirring device, a thermometer, a reflux condenser and a water separator, stirred at 25 ℃ for 15min, heated to 45 ℃ and maintained for 1h, heated to 70 ℃ and maintained for 1h, then rapidly heated to 90 ℃ and maintained for 2h, and simultaneously dehydrated and methanol are removed by the water separator. After the reaction is finished, cooling to 25 ℃, adding 47.35g of toluene for dissolving, then adding saturated salt water for repeated washing until the solution is neutral, then washing for 1 time by deionized water, layering, collecting an oil phase, and then adding 7.5g of anhydrous CaCl₂Drying for 24h, filtering to remove salt, collecting filtrate, and removing low-boiling-point substances from the filtrate under reduced pressure of-0.098 MPa and 190 ℃ to obtain 12.4g of MDT silicone oil.

Comparative example 2

39.84g (0.214mol) of 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane, 19.41g (0.143mol) of methyltrimethoxysilane and 59.21g of toluene were placed in a 250mL three-necked flask equipped with a magnetic stirrer, a thermometer and a reflux condenser, and 28.85g (1.436mol) of deionized water was mixed with 2.96g (0.03mol) of a 37% HCl solution at 25 ℃ and then dropped into the reaction system over 2 hours. Heating the reaction mixture to 70 deg.C, maintaining at the temperature for 3 hr, cooling to room temperature, washing the reaction mixture with saturated saline solution repeatedly to neutrality, washing with deionized water for 1 time, and adding 10.0g anhydrous CaCl₂Drying at normal temperature for 24 h. Filtering the mixed solution, collecting filtrate, and removing low-boiling-point substances under reduced pressure at-0.099 MPa and 185 deg.CThus, 9.9g of MDT silicone oil was obtained.

Test example: analysis and characterization

(a)¹Characterization by H NMR

The samples obtained in examples 1 to 6 and comparative examples 1 and 2 were dissolved in deuterated chloroform¹H NMR measurement of¹H NMR spectrogram for determining [ CH ] in MDT silicone oil₃SiO_3/2]Chain link, [ CH ]₃(CH₃O)SiO_2/2]Chain links and [ CH₃(OH)SiO_2/2]Chain link to end capping group [ CH₂＝CH(CH₃)₂SiO_1/2]Molar fraction of chain units (definition [ CH ]₂＝CH(CH₃)₂SiO_1/2]The number of moles of the mer is 1). Preparation of MDT Silicone oil from example 3¹For example, as shown in FIG. 1, H NMR indicates-CH at a concentration of. delta. -. 5.610 to 5.969ppm₂Chemical shift of proton in CH-, delta 3.043ppm is-Si-O-CH₃Chemical shift of the middle proton, wherein delta is 1.456-1.476 ppm and is-Si-CH in the vicinity of delta 0.000ppm₃Chemical shift of the middle proton. to-CH₂-Si-O-CH by area integration of CH-mesogen, defining the integration value as 1.000₃The area of the mesogen peak is 0.103, the area of the-Si-OH mesogen peak is 0.080, and-Si-CH₃The mesogen peak area was 3.584.

Due to the definition of-CH₂The integrated value of the peak area of 3 protons in CH-is 1.000, the molecular structural formula of the dimethylvinylsiloxy terminated MDT type branched silicone oil prepared in example 3 contains CH₂The chain link ratio a of the CH-structure is 1.00; -Si-O-CH₃Contains 3 protons, and the integrated value of the peak area is 0.103, so that c is 0.10; si — OH contains 1 proton, and its peak area integral value is 0.080, so d is 0.080/3 ≈ 0.03; -Si-CH₃Contains 3 protons, and the integrated value of the peak area is 3.584, so that b is 3.584-2a-c-d is 1.45. The molar fractions of the individual units in the MDT silicone oil molecule obtained in example 3 and the MDT silicone oil were determined from theseThe structure of (a) is as follows:

the same method was used for samples obtained in each of examples and comparative examples¹H NMR data was processed to obtain values of a, b, c and d in each sample molecule as shown in Table 1; calculating to obtain the content of silicon hydroxyl chain links in each sample by adopting a formula (1), calculating to obtain the content of silicon methoxyl chain links in each sample by adopting a formula (2), and calculating to obtain the content of vinyl chain links in each sample by adopting a formula (3):

in the formula, a, b, c and d respectively represent [ CH₂＝CH(CH₃)₂SiO_1/2]Chain link, [ CH ]₃SiO_3/2]Chain link, [ CH ]₃(CH₃O)SiO_2/2]Chain links and [ CH₃(OH)SiO_2/2]Mole fraction of mer.

Table 1 structural parameters of the dimethylvinylsiloxy terminated MDT branched silicone oils prepared in the various examples and comparative examples:

(b) GPC characterization

An Agilent PL-GPC50 type Gel Permeation Chromatograph (GPC) is adopted, toluene is taken as a mobile phase, a polysiloxane sample is taken as a standard sample, the column temperature is set to be 35 ℃, and the type of a separation column isHT2 (size 7.8X 300mm), the number average molecular weight (Mn) and polydispersity index (PDI) of each sample were determined, and the results are shown in Table 2.

TABLE 2 molecular weights and distributions of the dimethylvinylsiloxy terminated MDT type branched silicone oils prepared in the respective examples and comparative examples