Preparation method of MQ silicon resin

Abstract

The invention relates to the technical field of polymers, in particular to MQ silicon resin and a preparation method thereof. The preparation method of the MQ silicon resin comprises the following steps: mixing water glass, acetonitrile and an acid agent, and carrying out hydrolytic condensation reaction to obtain a polysilicic acid solution; and carrying out an end capping reaction on the polysilicic acid solution to obtain the MQ silicon resin. Acetonitrile is added into the reactor, so that the gelation problem of sodium silicate can be effectively inhibited, and particularly, the problem that the reactor is blocked by gel can be avoided when high-molecular MQ silicon resin is produced.

Description

Technical Field

[0001] The present application relates to the field of polymer technology, and in particular to a method for preparing MQ silicone resin. Background Art

[0002] MQ silicone resin is composed of monofunctional silicon-oxygen units (M group: R3SiO 1 / 2 ) and tetrafunctional silicon-oxygen units (Q group: SiO 4 / 2 ) is a high molecular polymer with a "core-shell" structure, which is mainly used in pressure-sensitive adhesives, defoamers, personal care and other fields. From the source of the Q group, its synthesis methods include silicate method and sodium silicate method, among which the sodium silicate method has lower cost and more advantages in industrial production. However, when the sodium silicate method is used to prepare MQ resin, the polymerization speed of the Q group is very fast, which is very easy to gel and block the reactor, affecting production. Summary of the invention

[0003] Based on this, the present application provides a method for preparing MQ silicone resin, and its technical solution is as follows:

[0004] A method for preparing MQ silicone resin comprises the following steps:

[0005] Mixing water glass, acetonitrile and an acid agent to cause a hydrolysis condensation reaction to obtain a polysilicic acid solution;

[0006] The polysilicic acid solution is subjected to a capping reaction to obtain MQ silicone resin.

[0007] Compared with the traditional solution, this application has the following beneficial effects:

[0008] Water glass can undergo hydrolysis and condensation reaction in the presence of an acid. In order to avoid the problem of clogging the reactor caused by gelation due to a fast condensation reaction, acetonitrile is added in the present application. The addition of acetonitrile can effectively suppress the gelation problem of sodium silicate, especially when producing high-molecular MQ silicone resin, it can avoid the problem of gel clogging the reactor. Moreover, compared with the method of vigorously stirring water glass to avoid gelation, the present application has low requirements for stirring equipment and can also save energy consumption.

[0009] Alternatively, the weight average molecular weight of the MQ silicone resin is 10000Da~40000Da. For example, the weight average molecular weight of the MQ silicone resin is 10000Da, 20000Da, 30000Da, 40000Da. The above-mentioned high molecular weight MQ silicone resin can be produced by controlling the reaction conditions of hydrolysis condensation, and the problem of gel blocking the reactor is avoided. Wherein, the reaction conditions of hydrolysis condensation include the pH value of the mixed system of water glass, acetonitrile and acidic agent, the mass ratio of the acidic compounds in the sodium silicate in the water glass, acetonitrile and the acidic agent, the concentration of sodium silicate in the water glass, the concentration of acidic substances in the acidic agent, the type of the acidic agent, the temperature of the hydrolysis condensation reaction, the average residence time of water glass, acetonitrile and the acidic agent in the reactor is relevant. Especially the concentration of the sodium silicate in the water glass.

[0010] Optionally, the pH value of the mixed system of water glass, acetonitrile and acid agent is less than 3. In this case, the hydrolysis condensation reaction is favorable. Preferably, the pH value of the mixed system of water glass, acetonitrile and acid agent is 1-2.

[0011] Optionally, the mass ratio of the sodium silicate in the water glass, acetonitrile and the acidic compound in the acid agent is (8-30): (1-3): (6-36). For example, the mass ratio is 8:1:6, 15:1:15, 30:1:36, 8:3:6, 15:3:15, 30:3:36, etc.

[0012] The stirring speed of mixing the water glass, acetonitrile and acid agent can be 100 rpm to 300 rpm. For example, the stirring speed is 100 rpm, 200 rpm, 300 rpm.

[0013] Optionally, mixing the water glass, acetonitrile and acid agent comprises the following steps:

[0014] Acetonitrile and an acid agent are continuously introduced into the reactor, and after the reactor is filled, water glass is continuously introduced.

[0015] The above method can continuously produce MQ silicone resin. Compared with the batch method for producing MQ silicone resin, the various indicators of different batches of MQ silicone resin are stable. More importantly, the full tank operation of the reactor can prevent the easy formation of skin in the empty volume of the reactor, which is conducive to long-term stable production. Moreover, the full tank operation of the reactor can also improve the stability of the hydrolysis condensation reaction and narrow the molecular weight distribution of the MQ silicone resin.

[0016] It is understood that the reactor can be a conventional tank reactor in the art, with an inlet and an outlet, and the inlet is located at the bottom and the outlet is located at the top. Compared with a tubular reactor, the use of a tank reactor can avoid molecular weight fluctuations or gel effects caused by feed fluctuations when preparing high molecular weight resins.

[0017] Acetonitrile and the acid agent can be pre-mixed before being introduced into the reactor, for example, mixed in a static mixer, and then continuously introduced into the reactor through the static mixer. The static mixer can be of SV type, SK type, SX type, SH type or SL type, with 1 to 100 units.

[0018] Optionally, after the water glass is introduced, the pH value of the mixed system in the reactor is controlled to be less than 3. In this case, it is beneficial to control the rate of the hydrolysis condensation reaction. Preferably, the pH value of the mixed system in the reactor is controlled to be 1-2.

[0019] It is understandable that after the water glass is introduced, the stirring function of the reactor is turned on. The stirring speed can be 100 rpm to 300 rpm. For example, the stirring speed is 100 rpm, 200 rpm, and 300 rpm.

[0020] Optionally, after the water glass is introduced, the flow rates of the water glass, the acid agent and the acetonitrile are controlled so that the mass ratio of the sodium silicate in the water glass, the acetonitrile and the acidic compound in the acid agent per unit time is (8-30):(1-3):(6-36). For example, the mass ratio is 8:1:6, 15:1:15, 30:1:36, 8:3:6, 15:3:15, 30:3:36, etc.

[0021] Optionally, the concentration of sodium silicate in the water glass is 10wt%~30wt%. When the concentration of sodium silicate is higher, it is more conducive to obtaining a molecular weight MQ silicone resin. Optionally, the concentration of sodium silicate in the water glass is 16wt%~30wt%, for example, the concentration of sodium silicate in the water glass is 16wt%, 20wt%, 25wt%, 30wt%, at this time, it is conducive to combining other hydrolysis condensation reaction conditions to prepare a high molecular weight MQ silicone resin, and there is no gel problem. For example, a MQ silicone resin with a weight average molecular weight of 10000Da~40000Da is prepared. A MQ silicone resin with a weight average molecular weight of 15000Da~25000Da is further prepared.

[0022] Optionally, the concentration of the acidic substance in the acid agent is 8wt% to 36wt%. For example, the concentration of the acidic substance in the acid agent is 8wt%, 10wt%, 15wt%, 20wt%, 30wt%, or 36wt%.

[0023] Optionally, the acid agent includes at least one of hydrochloric acid and sulfuric acid.

[0024] When hydrochloric acid, acetonitrile and acid agent coexist in the reactor, the three are in contact with each other to undergo a hydrolysis-condensation reaction to generate a polysilicic acid aqueous solution, and because the three are continuously introduced and the tank is fully operated, the hydrolysis-condensation reaction is carried out dynamically. The residence time of the acid agent is defined as the total volume of the reactor divided by the flow rate of the acid agent, the residence time of acetonitrile is the total volume of the reactor divided by the flow rate of the acetonitrile, and the residence time of water glass is the total volume of the reactor divided by the flow rate of the water glass. The average residence time of the water glass, acetonitrile and acid agent in the reactor is the average value of the residence time of the water glass, the residence time of the acetonitrile and the residence time of the acid agent. Optionally, the average residence time is 0.1min~10min. Preferably, the average residence time is 0.1min~3min. Optionally, the temperature of the hydrolysis-condensation reaction is 0℃~40℃. Preferably, the temperature of the hydrolysis-condensation reaction is 10℃~30℃.

[0025] Optionally, the polysilicic acid solution, alcohol reagent, capping agent and solvent are mixed to carry out a capping reaction.

[0026] It is understandable that the end-capping reaction can be carried out in another reactor, and the reactor can be a conventional autoclave reactor in the art, with an inlet and an outlet, and the inlet is located at the top and the outlet is located at the bottom. The reactor where the above-mentioned hydrolysis and condensation reaction is located is defined as reactor A, and the end-capping reaction occurs in reactor B. The outlet of reactor A is connected to the inlet of reactor B, and while the fluid is continuously introduced from the bottom inlet of the full tank reactor A, the hydrolysis and condensation reaction product continuously flows into reactor B from the top outlet of the full tank reactor A. In addition, after other substances in reactor A except the hydrolysis and condensation reaction product enter reactor B, they do not affect the end-capping reaction occurring in reactor B.

[0027] Optionally, the end-capping agent is selected from one or more of trimethylchlorosilane, hexamethyldisiloxane, vinyldimethylchlorosilane and divinyltetramethyldisiloxane.

[0028] Optionally, the mass of the end-capping agent accounts for 5wt% to 20wt% of the total mass of the polysilicic acid solution, the end-capping agent, the alcohol reagent and the solvent. For example, the mass of the end-capping agent accounts for 5wt%, 10wt%, 15wt%, 20wt% of the total mass of the polysilicic acid solution, the end-capping agent, the alcohol reagent and the solvent.

[0029] Optionally, the alcohol reagent is selected from one or more of methanol, ethanol, propanol, butanol, isopropanol and isobutanol.

[0030] Optionally, the mass of the alcoholic reagent accounts for 10wt% to 25wt% of the total mass of the polysilicic acid solution, the end-capping agent, the alcoholic reagent and the solvent. For example, the mass of the alcoholic reagent accounts for 10wt%, 15wt%, 20wt%, 25wt% of the total mass of the polysilicic acid solution, the end-capping agent, the alcoholic reagent and the solvent.

[0031] Optionally, the solvent is selected from one or more of benzene, toluene, xylene, hexamethyldisiloxane, C6-C8 straight-chain alkanes and C6-C8 branched-chain alkanes.

[0032] Optionally, the mass of the solvent accounts for 15wt% to 50wt% of the total mass of the polysilicic acid solution, the end-capping agent, the alcohol reagent and the solvent. For example, the mass of the solvent accounts for 15wt%, 25wt%, 40wt%, or 50wt% of the total mass of the polysilicic acid solution, the end-capping agent, the alcohol reagent and the solvent.

[0033] Optionally, the reaction temperature of the end-capping reaction is 40° C. to 90° C. For example, the reaction temperature of the end-capping reaction is 40° C., 70° C., or 90° C.

[0034] Optionally, the reaction time of the end-capping reaction is 1 h to 3 h. For example, the reaction time of the end-capping reaction is 1 h, 2 h, or 3 h.

[0035] Optionally, after the end-capping reaction, the following steps are further included:

[0036] The product obtained by the end-capping reaction is phase-separated, and the organic phase obtained by the phase separation is subjected to rectification.

[0037] Further optionally, the product obtained from the end-capping reaction is separated into phases, comprising the following steps: allowing the product obtained from the end-capping reaction to stand for a first time to obtain a first aqueous phase and a first organic phase; mixing the first organic phase and desalted water, and allowing to stand for a second time to obtain a second aqueous phase and a second organic phase, wherein the second organic phase is the organic phase obtained by phase separation.

[0038] It can be understood that the product obtained by the end-capping reaction can be passed into the reactor C and first allowed to stand. Optionally, the temperature of the first standing is 60°C to 90°C. Optionally, the time of the first standing is 0.5h to 3h. Reactor C can be a conventional kettle reactor in the art, having an inlet and an outlet, and the inlet is located at the top, the first aqueous phase is extracted from the bottom, the first organic phase is extracted from the top, and the outlet of reactor B is connected to the inlet of reactor C.

[0039] Optionally, the mass ratio of the first organic phase to the desalted water is 1:(0.5-3). For example, the mass ratio of the first organic phase to the desalted water is 1:0.5, 1:1, 1:2, 1:3.

[0040] The first organic phase and the desalted water can be pre-mixed, for example, in a static mixer, and then the two are continuously pumped into the reactor D through the static mixer, and the second standing. Wherein, the model of the static mixer can be SV type, SK type, SX type, SH type or SL type, and the number of units is 1 to 100. Optionally, the temperature of the second standing is 60°C to 90°C. Optionally, the second standing time is 0.5h to 3h. Reactor D can be a conventional kettle reactor in the art, with an inlet and outlet, and the inlet is located at the top, the second aqueous phase is extracted from the bottom, and the second organic phase is extracted from the top. The first organic phase and the desalted water of reactor C are mixed by a static mixer and connected to the inlet of reactor D.

[0041] The first aqueous phase and the second aqueous phase are both treated as wastewater for post-treatment. The organic phase is distilled to remove light components and part of the solvent in the organic phase.

[0042] Optionally, the distillation temperature is 140° C. to 160° C. For example, the distillation temperature is 140° C., 150° C., or 160° C.

[0043] The above method can effectively suppress the gel problem of sodium silicate by adding acetonitrile, especially when producing high molecular MQ silicone resin, it can avoid the problem of gel blocking the reactor. In addition, the above method of continuously introducing acetonitrile, acid agent and water glass into the reactor can realize the continuous production of MQ resin, the production process is stable, and the indicators of MQ silicone resin between batches are stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more completely understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0045] Figure 1 Schematic diagram of the structure of the production device of MQ silicone resin in various embodiments and comparative examples. DETAILED DESCRIPTION

[0046] The present application will be further described in detail below in conjunction with specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly understood.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0048] the term

[0049] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0050] In the present application, "plurality", "multiple", "multiple times", "plurality", etc., unless otherwise specified, refer to a number greater than 2 or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0051] In the present application, “several” means at least one, such as one, two, etc., unless otherwise clearly defined.

[0052] In this application, "optionally", "optional" and "optional" refer to optional, that is, to any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0053] In this application, in the "first aspect", "second aspect", "third aspect", "fourth aspect", etc., the terms "first", "second", "third", "fourth", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0054] In the present application, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the optional numerical distribution is considered continuous within the above numerical interval, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical range, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints. In this article, it is equivalent to directly listing each integer, such as t is an integer selected from 1 to 10, indicating that t is any integer selected from the integer group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all sub-ranges included therein.

[0055] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0056] In the present application, the percentage content, unless otherwise specified, refers to mass percentage for solid-liquid mixing and solid-solid mixing, and volume percentage for liquid-liquid mixing.

[0057] In this application, when it comes to percentage concentration, unless otherwise specified, it refers to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of the component.

[0058] In the present application, %(w / w) and wt% both represent weight percentage, %(v / v) refers to volume percentage, and %(w / v) refers to mass volume percentage.

[0059] The following is further described in conjunction with specific embodiments and comparative examples. The raw materials involved in the following specific embodiments and comparative examples, unless otherwise specified, can all be commercially available, the instruments used, unless otherwise specified, can all be commercially available, and the processes involved, unless otherwise specified, are all routinely selected by those skilled in the art.

[0060] In the following specific examples and comparative examples, the molecular weight and its distribution are tested by gel chromatography (GPC), using ethyl acetate as the mobile phase, and the GPC instrument model is Agilent 1260II GPC MDS. The specific test method is as follows: the sample is dissolved in ethyl acetate, separated by gel chromatography, and the molecular weight and molecular weight distribution of the MQ silicone resin sample are determined by relative calibration using a standard curve prepared with standard PS (polystyrene).

[0061] See also Figure 1 The production apparatus of MQ silicone resin in each embodiment and comparative example is the same, including reactor A 10, reactor B 20, reactor C 30, reactor D 40 and static mixer 50. The outlet of reactor A 10 is connected to the inlet of reactor B, the outlet of reactor B is connected to the inlet of reactor C, and the outlet of reactor C is connected to the inlet of reactor D through the static mixer 50.

[0062] Example 1

[0063] This embodiment provides an MQ silicone resin and a preparation method thereof, the steps are as follows:

[0064] At 25°C, 10.5wt% hydrochloric acid aqueous solution and acetonitrile are continuously introduced into reactor A at flow rates of 80g / min and 1g / min respectively until the tank is full, and then 25wt% water glass solution is continuously introduced into the full tank reactor A at a flow rate of 100g / min, and a hydrolysis condensation reaction occurs to obtain a polysilicic acid aqueous solution. Reactor A is kept stirring to ensure the mixing effect of the three materials. After the water glass is introduced, the pH of the mixed system in the reactor is measured to be 1.5. The average retention time is 7min. Polysilicic acid aqueous solution, ethanol, toluene, and hexamethyldisiloxane are continuously introduced into reactor B at speeds of 181g / min, 65g / min, 70g / min, and 17g / min, respectively, for end-capping reaction. The end-capping reaction temperature is 65°C and the reaction time is 2h. The end-capping reaction product is then sent to reactor C for the first standing. The temperature of the first standing is 65°C and the residence time is 1h to obtain the first aqueous phase and the first organic phase. The first organic phase was separated, mixed with desalted water in a static mixer, and then continuously pumped into the reactor D for a second static state. The feed rate of desalted water was 30 g / min, the temperature of the second static state was 65°C, and the residence time was 2 h to obtain a second aqueous phase and a second organic phase. The second organic phase was then continuously distilled at a distillation operating temperature of 150°C and an operating pressure of normal pressure to remove light components and part of the solvent in the second organic phase, and finally an MQ silicone resin solution was obtained. The obtained product was measured by GPC, and the weight average molecular weight was 22013 Da, and the molecular weight distribution was 1.31.

[0065] After the reactor A of this example was operated for 24 hours, no gel was produced.

[0066] Example 2

[0067] This embodiment provides an MQ silicone resin and a preparation method thereof, the steps are as follows:

[0068] At 15°C, 8wt% hydrochloric acid aqueous solution and acetonitrile are continuously introduced into reactor A at flow rates of 100g / min and 3g / min respectively until the tank is full, and then 25wt% water glass solution is continuously added to the full tank reactor A at a flow rate of 100g / min, and a hydrolysis condensation reaction occurs to obtain a polysilicic acid aqueous solution. Reactor A is kept stirring to ensure the mixing effect of the three materials. After the water glass is introduced, the pH of the mixed system in the reactor is measured to be 1.3. The average retention time is 5min, and the polysilicic acid aqueous solution, isopropanol, xylene, and divinyltetramethyldisiloxane are continuously introduced into reactor B at speeds of 203g / min, 50g / min, 85g / min, and 21g / min, respectively, for end-capping reaction. The end-capping reaction temperature is 50°C and the reaction time is 3h. Then the end-capping reaction product is sent to reactor C for the first standing. The temperature of the first standing is 60°C and the residence time is 1.5h to obtain the first aqueous phase and the first organic phase. The first organic phase was separated, mixed with desalted water in a static mixer, and then continuously pumped into the reactor D for a second static state. The feed rate of desalted water was 40 g / min, the temperature of the second static state was 70°C, and the residence time was 1 h to obtain a second aqueous phase and a second organic phase. The second organic phase was then continuously distilled at a distillation operating temperature of 150°C and an operating pressure of normal pressure to remove light components and part of the solvent in the second organic phase, and finally an MQ silicone resin solution was obtained. The obtained product was measured by GPC, and the weight average molecular weight was 20816 Da, and the molecular weight distribution was 1.22.

[0069] After the reactor A of this example was operated for 24 hours, no gel was produced.

[0070] Example 3

[0071] This embodiment provides an MQ silicone resin and a preparation method thereof, the steps are as follows:

[0072] At 30°C, 8wt% hydrochloric acid aqueous solution and acetonitrile are continuously introduced into reactor A at flow rates of 80g / min and 2g / min respectively until the tank is full, and then 23wt% water glass solution is continuously introduced into the full tank reactor A at a flow rate of 80g / min, and a hydrolysis condensation reaction occurs to obtain a polysilicic acid aqueous solution. Reactor A is kept stirring to ensure the mixing effect of the three materials. After the water glass is introduced, the pH of the mixed system in the reactor is measured to be 1. The average retention time is 10min, and the polysilicic acid aqueous solution, methanol, benzene, and trimethylchlorosilane are continuously introduced into reactor B at speeds of 162g / min, 45g / min, 60g / min, and 19g / min, respectively, for end-capping reaction. The temperature of the end-capping reaction is 70°C and the reaction time is 1h. Then the end-capping reaction product is sent to reactor C for the first standing. The temperature of the first standing is 70°C and the residence time is 1h to obtain the first aqueous phase and the first organic phase. The first organic phase was separated, mixed with desalted water in a static mixer, and then continuously pumped into the reactor D for a second static state. The feed rate of desalted water was 35 g / min, the temperature of the second static state was 70°C, and the residence time was 2 h to obtain a second aqueous phase and a second organic phase. The second organic phase was then continuously distilled at a distillation operating temperature of 150°C and an operating pressure of normal pressure to remove light components and part of the solvent in the second organic phase, and finally an MQ silicone resin solution was obtained. The obtained product was measured by GPC, and the weight average molecular weight was 18926 Da, and the molecular weight distribution was 1.42.

[0073] After the reactor A of this example was operated for 24 hours, no gel was produced.

[0074] Example 4

[0075] The present embodiment provides an MQ silicone resin and a preparation method thereof, which is basically the same as Example 1, with the main difference that 10.5wt% hydrochloric acid aqueous solution and acetonitrile are continuously passed into reactor A at a flow rate of 40g / min and 0.5g / min, respectively, and reactor A is not full, and then 25wt% water glass solution is continuously passed into reactor A at a flow rate of 50g / min, and reactor A is still not full, and a hydrolysis condensation reaction occurs to obtain a polysilicic acid aqueous solution. Stirring is maintained in reactor A to ensure the mixing effect of the three streams of materials. After the water glass is passed, the pH of the mixed system in the reactor is measured to be 1.5. The average retention time is 7min, and polysilicic acid aqueous solution, ethanol, toluene, and hexamethyldisiloxane are continuously passed into reactor B at a speed of 90.5g / min, 32.5g / min, 35g / min, and 8.5g / min, respectively, for end-capping reaction, and the end-capping reaction temperature is 65°C and the reaction time is 2h. The end-capping reaction product is then sent to the reactor C for the first standing, the temperature of the first standing is 65°C, the residence time is 1h, and the first aqueous phase and the first organic phase are obtained. The first organic phase is separated, mixed with desalted water in a static mixer, and then continuously pumped into the reactor D for the second standing, the feed rate of desalted water is 15g / min, the temperature of the second standing is 65°C, the residence time is 2h, and the second aqueous phase and the second organic phase are obtained. The second organic phase is then continuously distilled, the distillation operating temperature is 150°C, the operating pressure is normal pressure, the light components and part of the solvent in the second organic phase are removed, and finally an MQ silicone resin solution is obtained. The obtained product was measured by GPC, and the weight average molecular weight was 22517Da and the molecular weight distribution was 1.73.

[0076] As the hydrolysis and condensation reaction proceeds, it is found that in this embodiment, after the reactor A is operated for 120 minutes, although no gel is produced, there is a crust on the empty volume reactor wall. At the same time, compared with the product of Example 1, the molecular weight distribution of the product of this embodiment is significantly broadened, indicating that the system is unstable.

[0077] Comparative Example 1

[0078] This comparative example provides an MQ silicone resin and a preparation method thereof, which are basically the same as Example 1, with the main difference that a 10.5 wt % hydrochloric acid aqueous solution is continuously introduced into the reactor A at a flow rate of 40 g / min, acetonitrile is not introduced, and the reactor A is not full, and then a 25 wt % water glass solution is continuously introduced into the reactor A at a flow rate of 50 g / min, and the reactor A is still not full, and a hydrolysis condensation reaction occurs.

[0079] As the hydrolysis and condensation reaction proceeded, it was found that in this comparative example, the reactor A produced gel and became blocked after running for 5 minutes.

[0080] Comparative Example 2

[0081] This comparative example provides an MQ silicone resin and a preparation method thereof, which are basically the same as Example 1, except that a 10.5 wt % aqueous hydrochloric acid solution is continuously introduced into the reactor A at a flow rate of 80 g / min until the tank is full, and acetonitrile is not introduced, and then a 25 wt % water glass solution is continuously introduced into the full tank of the reactor A at a flow rate of 100 g / min to cause a hydrolysis condensation reaction.

[0082] As the hydrolysis and condensation reaction proceeded, it was found that in this comparative example, the reactor A produced gel and became blocked after running for 15 minutes.

[0083] From the above comparison, it can be seen that in Examples 1 to 3, after adding acetonitrile, the situation of gel blocking the reactor can be avoided. Compared with Example 1, in Example 4, acetonitrile was added to the reactor A but the tank was not fully operated. Although the gel blocking can be suppressed, the molecular weight distribution is wide, and the empty volume is easy to form a skin, which is not conducive to long-term stable production. In Comparative Example 1, acetonitrile was not added to the reactor A and the tank was not fully operated. The reactor A was blocked by gel in a short time. In Comparative Example 2, acetonitrile was not added but the tank was fully operated. At a high water glass concentration (25%), gel blocking occurred.

[0084] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0085] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for preparing MQ silicone resin, characterized in that: The following steps are involved: Mixing water glass, acetonitrile and an acid agent to cause a hydrolysis condensation reaction to obtain a polysilicic acid solution; The polysilicic acid solution is subjected to a capping reaction to obtain MQ silicone resin.

2. The method for preparing MQ silicone resin according to claim 1, characterized in that: The weight average molecular weight of the MQ silicone resin is 10000Da~40000Da.

3. The method for preparing MQ silicone resin according to claim 1, characterized in that: The pH value of the mixed system of water glass, acetonitrile and acid agent is less than 3.

4. The method for preparing MQ silicone resin according to claim 2, characterized in that: The mass ratio of the sodium silicate in the water glass, acetonitrile and the acidic compound in the acid agent is (8-30): (1-3): (6-36).

5. The method for preparing MQ silicone resin according to claim 1, characterized in that: The water glass, acetonitrile and acid agent are mixed, comprising the following steps: Acetonitrile and an acid agent are continuously introduced into the reactor, and after the reactor is filled, water glass is continuously introduced.

6. The method for preparing MQ silicone resin according to claim 5, characterized in that: After the water glass is introduced, the pH value of the mixed system in the reactor is controlled to be less than 3; optionally, after the water glass is introduced, the flow rates of the water glass, acetonitrile and the acidic agent are controlled so that the mass ratio of the sodium silicate in the water glass, acetonitrile and the acidic compound in the acidic agent per unit time is (8-30): (1-3): (6-36); optionally, the average residence time of the water glass, acetonitrile and the acidic agent in the reactor is 0.1 min-10 min.

7. The method for preparing the MQ silicone resin according to any one of claims 1 to 6, characterized in that: Includes at least one of the following features: (1) The concentration of sodium silicate in the water glass is 10wt%~30wt%; (2) The concentration of the acidic substance in the acid agent is 8wt%~36wt%; (3) The acidic agent includes at least one of hydrochloric acid and sulfuric acid; (4) The temperature of the hydrolysis condensation reaction is 0°C to 40°C.

8. The method for preparing the MQ silicone resin according to any one of claims 1 to 6, characterized in that: The polysilicic acid solution, the end-capping agent, the alcohol reagent and the solvent are mixed to carry out an end-capping reaction.

9. The method for preparing MQ silicone resin according to claim 8, characterized in that: Includes at least one of the following features: (1) The end-capping agent is selected from one or more of trimethylsilyl chloride, hexamethyldisiloxane, vinyldimethylsilyl chloride and divinyltetramethyldisiloxane; (2) The mass of the end-capping agent accounts for 5wt% to 20wt% of the total mass of the polysilicic acid solution, the end-capping agent, the alcohol reagent and the solvent; (3) The alcohol reagent is selected from one or more of methanol, ethanol, propanol, butanol, isopropanol and isobutanol; (4) The mass of the alcohol reagent accounts for 10wt% to 25wt% of the total mass of the polysilicic acid solution, the end-capping agent, the alcohol reagent and the solvent; (5) The solvent is selected from one or more of benzene, toluene, xylene, hexamethyldisiloxane, C6-C8 straight-chain alkanes and C6-C8 branched-chain alkanes; (6) The mass of the solvent accounts for 15wt% to 50wt% of the total mass of the polysilicic acid solution, the end-capping agent, the alcohol reagent and the solvent; (7) The reaction temperature of the end-capping reaction is 40°C~90°C; (8) The reaction time of the end-capping reaction is 1h~3h.

10. The method for preparing the MQ silicone resin according to any one of claims 1 to 6 and 9, characterized in that: After the end-capping reaction, the following steps are also included: The product obtained by the end-capping reaction is phase-separated, and the organic phase obtained by the phase separation is subjected to rectification.

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