CN114230795A - Method for continuously preparing controllable high molecular weight MQ resin at low power - Google Patents
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Abstract
The invention discloses a method for continuously preparing controllable high molecular weight MQ resin with low power, which comprises the steps of continuously adding a hydrochloric acid aqueous solution into an LOOP reactor A to fill the reactor A, continuously adding a water glass solution into the reactor A when the pH value of a system is less than 2, controlling the pH value to be stable, and carrying out hydrolysis condensation reaction in the reactor A to preliminarily form polysilicic acid hydrosol; and carrying out aging, end-capping reaction, phase separation and rectification to obtain the MQ resin. The method of the invention does not need high power shearing, effectively solves the problem of gel in the production process, thereby realizing the synthesis of the MQ resin with high molecular weight by increasing the concentration of the water glass, further generating the MQ resin with controllable high molecular weight, and the molecular weight distribution of the generated MQ resin is narrow.
Description
Technical Field
The invention belongs to the technical field of silicon resin, and particularly relates to a method for continuously preparing controllable high molecular weight MQ resin at low power.
Background
The organic silicon resin is one of the core products of the current organic silicon industry, is generally an organic silicon high molecular compound with a reticular structure, has properties between those of an organic high molecular compound and an inorganic high molecular compound, and has high temperature resistance, hydrophobicity and chemical resistance which are difficult to achieve by common resins. In addition, it has excellent electrical insulation, mechanical properties, heat resistance and weather resistance. The electric insulating paint, moulding plastic, laminated material, demoulding agent and moisture-proof agent made up by using said invented material as base material can be extensively used in the fields of motor, electric equipment, electronics, aviation and building.
The MQ silicon resin is one of organic silicon resins, has excellent heat resistance, low temperature resistance, film forming property, flexibility, water resistance and bonding property, can be used as a reinforcing filler of addition type liquid baby rubber, a tackifier, a filler of siloxane pressure sensitive adhesive and an LED packaging material, and is widely applied to the departments of electronics, electric appliances, motors, aviation, buildings and the like.
The MQ silicon resin is prepared from silicon-oxygen units (R3SiO1/2, M unit for short) with monofunctional chain links and silicon-oxygen units (SiO unit) with tetrafunctional chain links4/2Q unit for short) is hydrolyzed and condensed to form a silicone resin with a relatively special structure. Generally, the MQ silicon resin is a compact spherical object with a double-layer three-dimensional structure, and the spherical core part is cage-shaped SiO with Si-O chain connection, high density and polymerization degree of 15-502(ii) a Part of the spherical shell is surrounded by a less dense layer of R3SiO 1/2. The structural formula of the compound can be represented as (R1R2R3Si0.5) a (SiO2) b.
U.S. Pat. No. 4, 7951895, 2, European patent EP1976909, 1 and Japanese patent JP4972103, 2 provide a process for the preparation of MQ resins in a continuous process, using a process with a power of more than 10kW/m3The intensive mixing device solves the problem of rapid mixing in the polycondensation process. Japanese patent JP3772258B2 provides a process for preparing MQ resin by a batch method, and in order to solve the problem of mixing difficulty, the water glass concentration is controlled to be 3 to 15 wt%.
Chinese patent application CN109438709A discloses a method for preparing MQ resin by batch process. The patent adopts hydrochloric acid for priming in a three-neck flask by a batch method, and completes the mixing of the hydrochloric acid and the water glass in a mode of dropwise adding the water glass. Chinese patent application CN109161021A discloses a preparation method of controllable high molecular weight MQ silicon resin, which can synthesize high molecular weight MQ resin by introducing MD structure into prepared MQ structure through hydrosilylation. Chinese patent application CN 113321809 a discloses a method for preparing MQ resin with narrow molecular weight distribution. The patent accomplishes a continuous reaction of mixing of hydrochloric acid and water glass by continuously feeding into a static mixer.
The reaction of water glass and hydrochloric acid belongs to a fast reaction, the reaction time belongs to millisecond level, simultaneously, a large amount of heat is emitted, gelation is easy under the condition of poor mass transfer and heat transfer, particularly, the synthesis of high molecular weight MQ resin from high-concentration raw materials is more difficult to control, the problem of reaction gelation is solved no matter domestic intermittent mixing is carried out in a dropwise adding mode or abroad by adopting high-power powerful mixing equipment, and continuous mixing is carried out by a static mixer, and meanwhile, in order to reduce the reaction difficulty, the concentration of the raw materials is often reduced, for example, the concentration of the water glass is controlled below 15%.
Although the gel problem is solved by adopting a mode of slowly dripping by an intermittent method in the prior document, the problem of wide molecular weight distribution cannot be solved because the time for water glass to enter a system is different; the high-power continuous production method has better mass and heat transfer, but can put high requirements on equipment, and has the advantages of corrosion resistance, high strength and high energy consumption; although the gel problem is solved in a short time and the requirement on mixing equipment is low by adopting the static mixer for continuous mixing, the high requirement is provided for feeding equipment, the tolerance on fluctuation is extremely low, and even if the content of hydrochloric acid is excessive, the gel is easily caused by slight fluctuation in the long-time operation process, so that pipelines are blocked.
Disclosure of Invention
In order to solve the existing problems, the invention provides a method for continuously preparing controllable high molecular weight MQ resin with low power, and the synthesis of the high molecular weight MQ resin is realized by using a loop reactor to control the reaction pH value and improve the integral concentration after mixing.
In order to achieve the above purpose, the invention is realized by the following technical scheme:
a method for continuously preparing controllable high molecular weight MQ resin with low power comprises the steps of preparing polysilicic acid hydrosol, aging, end capping reaction, phase splitting and rectifying to obtain the MQ resin, wherein the preparation of the polysilicic acid hydrosol comprises the following steps: in the reactor A, hydrochloric acid aqueous solution is continuously added to fill the reactor A, when the pH value in the reactor is less than 2, water glass solution is continuously added into the reactor A, the mixture is continuously extracted and partially flows back, the pH value in the reactor is controlled to be stable, and at the moment, hydrolysis condensation reaction occurs in the reactor A, and polysilicic acid hydrosol is initially formed.
In a specific embodiment, the method comprises the steps of:
1) in the reactor A, firstly, continuously adding a hydrochloric acid aqueous solution to fill the reactor A, when the pH value in the reactor is less than 2, continuously adding a water glass solution into the reactor A, continuously extracting and partially refluxing, controlling the pH value in the reactor to be stable, and then carrying out hydrolysis condensation reaction in the reactor A to preliminarily form polysilicic acid hydrosol;
2) in the reactor B, the preliminarily formed polysilicic acid hydrosol is continuously aged to obtain the polysilicic acid hydrosol with certain molecular weight, namely SiO4(iii)/2, Q unit for short;
3) continuously adding the product, alcohol, solvent and end-capping reagent in the reactor B to carry out end-capping reaction in a reactor C;
4) in the reactor D, continuously carrying out phase separation on the product in the reactor C, dividing the product into two phases, namely an organic phase containing MQ resin and a water phase not containing the MQ resin, washing the two phases to be used as wastewater treatment, and continuously washing the organic phase;
5) and in the reactor E, continuously rectifying the water-washed organic phase in the reactor E to obtain the MQ resin.
In a specific embodiment, the reactor a in step 1) is a LOOP reactor, and is composed of a power device, a mixing device and a LOOP, wherein the power device is used for providing power for extraction and/or reflux of the reaction liquid, the mixing device is used for mixing and reacting the hydrochloric acid aqueous solution and the water glass solution, and the LOOP is used for reflux of the reaction liquid;
preferably, the power equipment is selected from one or more of diaphragm pump, centrifugal pump and peristaltic pump, and the power density epsilon is less than10kW/m3(ii) a The mixing device is a static mixer, preferably selected from SV type, SK type, SX type, SH type and SL type, and the number of units is 1-100.
In a specific embodiment, the pH value in the reactor is controlled to be stabilized at 1-3 in the step 1).
In a specific embodiment, the reflux ratio of the reactor A in the step 1) is 2-30, the reaction temperature is 10-30 ℃, and the retention time is 1-3 min.
In a specific embodiment, the mass concentration of the hydrochloric acid aqueous solution in the step 1) is 12-36%, the feeding speed is 200-600g/min, the mass concentration of the water glass solution is 15-36%, and the feeding speed is 793-2087 g/min; preferably, SiO therein2The molar ratio of HCl/1.48 to 1.60.
In a specific embodiment, the reactor B in the step 2) is a pipeline reactor or a kettle type reactor and is used for aging the Q group unit; preferably, the aging time is 2-10 min.
In a specific embodiment, the reactor C in step 3) is a tank reactor, and is mainly used for the capping reaction of the M units to the Q units to form a crude MQ resin;
preferably, the blocking agent is selected from one or more of trimethylchlorosilane, vinyldimethylchlorosilane, hexamethyldisiloxane, tetramethyldisiloxane, divinyltetramethyldisiloxane;
preferably, the solvent is selected from one or more of xylene, toluene, benzene, n-heptane, hexamethyldisiloxane;
preferably, the alcohol is selected from one or more of methanol, ethanol, propanol, isopropanol, isobutanol;
more preferably, the flow rate of the product continuously added into the reactor B in the reactor C is 1000-2687g/min, the flow rate of the alcohol is 450-550g/min, the flow rate of the solvent is 550-750g/min, and the flow rate of the blocking agent is 75-125 g/min.
In a specific embodiment, the reactor D in the step 4) is a continuous water-washing phase separator selected from a kettle-type phase-separating water scrubber or a tower-type water-washing phase separator.
In a specific embodiment, the reactor E in the step 5) is a rectifying tower, and the atmospheric rectification is carried out, wherein the operation temperature is 20-30 ℃ higher than the boiling point of the solvent.
Compared with the prior art, the invention has the following beneficial effects:
1) compared with the intermittent kettle type synthesis MQ resin, the invention has the advantages that the pH value is kept unchanged after the water glass and the hydrochloric acid are mixed due to the continuous reaction in the loop reactor, and meanwhile, the molecular weight distribution is narrower under the same aging time.
2) Compared with the prior art, the loop reactor adopted by the invention controls the reflux ratio, and the power density epsilon is less than 10kW/m3The pH value of the system can be controlled, so that the problem of gelation is solved, and energy is effectively saved.
3) Compared with a static mixer, the loop reactor adopted by the invention ensures the stability of the whole pH value because part of the acidic liquid flows back all the time, thereby avoiding the problem of gelation caused by the sudden change of instantaneous pH due to unstable flow of the static mixer; thereby realizing the possibility of increasing the concentration of the water glass on the reaction equipment, synthesizing the high molecular weight MQ resin by the increase of the concentration and not being easy to gel. Meanwhile, due to the improvement of the material concentration, the content of introduced water is correspondingly reduced, the wastewater generated in production is greatly reduced, the energy consumption for treating the wastewater is reduced, and the utilization rate of the kettle is improved by more than 50 percent.
Drawings
FIG. 1 is a schematic view of the structure of a LOOP reactor of the present invention.
Wherein, 1 is mixing equipment, 2 power equipment, 3 ring pipes, 4 water glass, 5 hydrochloric acid and 6 extracted liquid.
Detailed Description
The following examples will further illustrate the method provided by the present invention in order to better understand the technical solution of the present invention, but the present invention is not limited to the listed examples, and should also include any other known modifications within the scope of the claims of the present invention.
A low-power continuous method for preparing MQ resin with controllable high molecular weight and a synthetic method thereof comprise the following steps:
1) in the reactor A, firstly, continuously adding a hydrochloric acid aqueous solution to fill the reactor A, when the pH value of the system is less than 2, continuously adding a water glass solution into the reactor A, and then carrying out a hydrolytic condensation reaction on the hydrochloric acid aqueous solution and the water glass solution in the reactor A to preliminarily form polysilicic acid hydrosol;
2) continuously aging the preliminarily formed polysilicic acid hydrosol in a reactor B to obtain the polysilicic acid hydrosol with a certain molecular weight, namely SiO4/2, which is called Q unit for short;
3) continuously adding the product, alcohol, solvent and end-capping reagent in the reactor B to carry out end-capping reaction in a reactor C;
4) in the reactor D, continuously carrying out phase separation on the product in the reactor C, dividing the product into two phases, namely an organic phase containing MQ resin and a water phase not containing the MQ resin, washing the two phases to be used as wastewater treatment, and continuously washing the organic phase;
5) and in the reactor E, continuously rectifying the water-washed organic phase in the reactor E to obtain the MQ resin product with a single solvent system.
Wherein, the reactor A in the step 1) is a loop reactor, as shown in figure 1, the loop reactor consists of three parts, namely power equipment 2, mixing equipment 1 and a loop pipe 3, wherein the power equipment provides loop power circulation to ensure that liquid always flows in the loop, the power equipment is selected from one or more of a diaphragm pump, a centrifugal pump and a peristaltic pump, and the power density epsilon is less than 10kW/m 3; mixing apparatus provides the mixture of material, guarantees that equipment can be abundant mixes, accomplishes the mass transfer heat transfer, and this mixing apparatus is static mixer, has following characteristic: selected from SV type, SK type, SX type, SH type, SL type, the number of units is 1-100; the ring pipe is a liquid conveying pipeline, and the infinite circulation of liquid can be realized under the condition that no new liquid is input when the ring pipe is full of liquid.
In the LOOP reactor shown in figure 1, water glass is continuously fed into a mixing device 1, hydrochloric acid 5 is continuously supplemented into the mixing device 1 through a power device 2 under a certain pH condition and is continuously extracted, a part of extracted liquid 6 enters a reactor B for aging, most of the extracted liquid flows back to the mixing device 1 again through a LOOP pipe 3 under the drive of the power device 2, wherein the extracted amount of the extracted liquid 6 entering the reactor B is equal to the continuous supplementing feeding amount of the water glass 1 and the hydrochloric acid 2.
Step 1) reaction taking place in reactor a: firstly, hydrochloric acid and water glass are subjected to hydrolysis reaction to generate an intermediate product a, and then the intermediate product a is extremely unstable and rapidly subjected to polycondensation reaction to generate a product b, wherein the principle can be illustrated by the following reaction scheme:
step 1) the reaction occurring in the reactor a is extremely liable to gel, and the applicant has found that the root of the gel is the instantaneous pH change caused by uneven mixing, which is caused when the corresponding pH value corresponds to an unstable state of the mixed material. The invention can avoid the occurrence of gel to a great extent by controlling the pH value in the reactor A to be basically maintained stable within the range of 1-3, thereby improving the concentration of materials and preparing the MQ resin with high molecular weight.
Specifically, in order to achieve the stable control of the pH value, the reactor A disclosed by the invention adopts a LOOP reactor, materials of hydrochloric acid and water glass are mixed in the reactor A, and partial acidic materials are enabled to flow back in a LOOP all the time in a backflow mode, and the stability of the whole pH value of a system is basically ensured by cooperating with the control of the flow of each material flow, so that the stability of the molecular weight is realized, and the MQ resin with narrow molecular weight distribution is obtained.
In step 1), the reflux ratio of the present invention is controlled to be 2 to 30, for example, 2, 5, 8, 10, 12, 18, 20, 22, 25, 27, 30, and the reflux ratio of the present invention is the amount of liquid stream refluxed to the reactor a divided by the amount of stream withdrawn to the reactor B. The reaction temperature in the reactor A is 10-30 ℃, and the average residence time is 1-3 min.
Wherein, on the premise of stable pH value and no gelation, the molecular weight can be improved by improving the concentration of the raw materials, and the mass concentration of the hydrochloric acid aqueous solution of the material A in the reactor A in the step 1) is 12 to 36 percent, such as but not limited to 12 percent, 14 percent,16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, preferably 18-28%, with a feed rate of 200-600g/min, including for example but not limited to 200g/min, 250g/min, 300g/min, 50g/min, 400g/min, 450g/min, 500g/min, 550g/min, 600g/min, preferably 300-500 g/min; the mass concentration of the water glass aqueous solution is 15-36%, such as but not limited to 15%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, preferably 20-30%, and the feeding speed is 800-2087g/min, such as but not limited to 800g/min, 850g/min, 900g/min, 950g/min, 1000g/min, 1100g/min, 1200g/min, 1300g/min, 1400g/min, 1500g/min, 1600g/min, 1700g/min, 1800g/min, 1900 g/min, 2087g/min, preferably 1100-1500 g/min; wherein SiO in the added water glass solution and hydrochloric acid aqueous solution2the/HCl molar ratio is from 1.48 to 1.60, including for example but not limited to 1.48, 1.49, 1.5, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, 1.57, 1.58, 1.59, 1.60. The concentration of the water glass solution can be far higher than the raw material concentration level of 15 percent in the prior art, and the concentration of the raw materials can not be further improved in the prior art due to gel, so that the preparation of the MQ resin with high molecular weight is difficult.
The reactor B in the step 2) is mainly used for aging the Q group unit, and the reactor is one or more of a pipeline reactor and a kettle type reactor. Generally, the feeding amount continuously entering the reactor B and the reactor C is the actual output amount of the reactor A and is also equal to the sum of the continuous feeding amounts of the water glass solution and the hydrochloric acid aqueous solution in the reactor A. Namely, the feeding speed of the hydrochloric acid aqueous solution of the material in the reactor A is 600g/min minus 200-.
The reactor C in the step 3) is a kettle type reactor which is mainly used for the end capping reaction of the M unit to the Q unit to form coarse MQ resin, and the reaction principle is that
Wherein the blocking agent in the reactor C is selected from one or more of trimethylchlorosilane, vinyldimethylchlorosilane, hexamethyldisiloxane, tetramethyldisiloxane and divinyltetramethyldisiloxane, and the flow rate is controlled to be 75-125 g/min; the solvent is one or more of dimethylbenzene, methylbenzene, benzene, n-heptane and hexamethyldisiloxane, and the flow rate is controlled at 550-750 g/min; the alcohol is one or more of methanol, ethanol, propanol, isopropanol and isobutanol, and the flow rate is controlled at 550 g/min.
In the step 4), the reactor D is a continuous washing phase separator, and a kettle-type phase separator or a tower-type washing phase separator is selected;
in the step 5), the reactor E is a rectifying tower, the aim is to rectify the solvent and low-boiling-point substances, different rectification conditions are set according to different solvents, normal-pressure rectification is usually carried out, and the operating temperature is 20-30 ℃ higher than the boiling point of the solvent.
It should be noted that, except for the specific description of the present invention, the related operations of steps 2) to 5) can all refer to the prior art, and the present invention is not particularly limited. The relevant operating and process conditions of the prior art are applicable to the present invention, and are conventional in the art.
The invention is further illustrated, but not limited, by the following more specific examples. In the following examples, molecular weight and its distribution were tested: the measurement was carried out by gel chromatography (GPC) using ethyl acetate as a mobile phase, model LC-20AD by GPC apparatus and Shimadzu corporation. The specific test method is as follows: dissolving the sample in ethyl acetate, performing gel chromatography, and preparing a standard curve by using a standard PS (polystyrene) to relatively correct to determine the molecular weight and the molecular weight distribution of the MQ class silicon resin material sample.
Sources of raw materials in examples: water glass was purchased from lezhou soda ash ltd; the remaining materials were purchased from Sigma-Aldrich.
Example 1
In reactor A, 12 wt% aqueous hydrochloric acid and 15 w/w hydrochloric acid were continuously added at 10 ℃ at flow rates of 500g/min and 1376g/min, respectivelyt% water glass solution, SiO2The HCl/ratio was 1.58. The power equipment in the reactor A is a centrifugal pump, the mixing equipment is an SV type static mixer, the average residence time is 1min, the pH value is 2, the reflux ratio is 2, the aging time in the reactor B is 2min, and the reactor B is a tubular reactor. All the products in the reactor B and isopropanol, trimethylchlorosilane and xylene are continuously added into a reactor C at the speed of 450g/min, 120g/min and 550g/min respectively. The reaction temperature of the reactor C is 60 ℃, and the end capping reaction time is 120 min. And continuously feeding the product of the reactor C into a reactor D, and washing and phase-separating the reactor D for 40 min. And finally, continuously feeding the organic phase in the reactor D into a reactor E for rectification at the operating temperature of 155 ℃ and the operating pressure of normal pressure, and removing low-boiling-point substances after rectification to obtain the MQ resin solution. The resulting product MQ resin was determined to have a molecular weight Mw of 14178 and a molecular weight distribution of 1.3.
Example 2
In reactor A, a 24 wt% aqueous hydrochloric acid solution and a 20 wt% aqueous glass solution were continuously added at flow rates of 400g/min and 1546g/min, respectively, at 20 ℃ and a SiO2/HCl ratio of 1.48. The power equipment in the reactor A is a diaphragm pump, the mixing equipment is an SK type static mixer, the average residence time is 2min, the pH value is 1, the reflux ratio is 10, the aging time in the reactor B is 4min, and the reactor B is a tubular reactor. All the products in the reactor B, methanol, vinyl dimethylchlorosilane and toluene are continuously added into the reactor C at 500g/min, 125g/min and 700g/min respectively. The reaction temperature of the reactor C is 65 ℃, and the end capping reaction time is 135 min. And continuously feeding the product of the reactor C into a reactor D, and washing and phase-separating the reactor D for 30 min. And finally, continuously feeding the organic phase in the reactor D into a reactor E for rectification at the operating temperature of 155 ℃ and the operating pressure of normal pressure, and removing low-boiling-point substances after rectification to obtain the MQ resin solution. The resulting product MQ resin was determined to have a molecular weight Mw of 16021 and a molecular weight distribution of 1.3.
Example 3
36 wt% aqueous hydrochloric acid and 25 wt% aqueous glass solution were continuously added at 30 ℃ and flow rates of 300g/min and 1495g/min, respectively, to the reactor A, the SiO2/HCl ratio being 1.59. The power equipment in the reactor A is a peristaltic pump, the mixing equipment is an SX type static mixer, the average residence time is 3min, the pH value is 2, the reflux ratio is 15, the aging time in the reactor B is 6min, and the reactor B is a tubular reactor. All of the product from reactor B and ethanol, hexamethyldisilazane were continuously fed into reactor C at 550g/min, 85g/min, and 750g/min, respectively. The reaction temperature of the reactor C is 70 ℃, and the end capping reaction time is 150 min. And continuously feeding the product of the reactor C into a reactor D, and washing and phase-separating the reactor D for 50 min. And finally, continuously feeding the organic phase in the reactor D into a reactor E for rectification at the operating temperature of 155 ℃ and the operating pressure of normal pressure, and removing low-boiling-point substances after rectification to obtain the MQ resin solution. The resulting product MQ resin was determined to have a molecular weight Mw of 18565 and a molecular weight distribution of 1.3.
Example 4
36 wt% aqueous hydrochloric acid and 30 wt% aqueous sodium silicate were continuously added at flow rates of 200g/min and 800g/min, respectively, at 10 ℃ to a reactor A, the SiO2/HCl ratio being 1.53. The power equipment in the reactor A is a centrifugal pump, the mixing equipment is an SL-type static mixer, the average residence time is 1min, the pH value is 1, the reflux ratio is 20, the aging time in the reactor B is 8min, and the reactor B is a tubular reactor. All the products in reactor B and propanol, divinyltetramethyldisiloxane, benzene were continuously fed into reactor C at 500g/min, 100g/min, 500g/min, respectively. The reaction temperature of the reactor C is 75 ℃, and the end capping reaction time is 165 min. And continuously feeding the product of the reactor C into a reactor D, and washing and phase-separating the reactor D for 60 min. And finally, continuously feeding the organic phase in the reactor D into a reactor E for rectification at the operating temperature of 155 ℃ and the operating pressure of normal pressure, and removing low-boiling-point substances after rectification to obtain the MQ resin solution. The resulting product MQ resin (I) was determined to have a molecular weight Mw of 20256 and a molecular weight distribution of 1.3.
Example 5
36 wt% aqueous hydrochloric acid and 36 wt% aqueous glass solution were continuously added to the reactor A at 10 ℃ at flow rates of 600g/min and 2087g/min, respectively, and the SiO2/HCl ratio was 1.60. The power equipment in the reactor A is a centrifugal pump, the mixing equipment is an SH type static mixer, the average residence time is 1min, the pH value is 3, the reflux ratio is 30, the aging time in the reactor B is 10min, and the reactor B is a tubular reactor. All the products in reactor B and isobutanol, tetramethyldisiloxane, n-heptane were continuously fed into reactor C at 550g/min, 75g/min, 700g/min, respectively. The reaction temperature of the reactor C is 80 ℃, and the end capping reaction time is 180 min. And continuously feeding the product of the reactor C into a reactor D, and washing and phase-separating the reactor D for 30 min. And finally, continuously feeding the organic phase in the reactor D into a reactor E for rectification at the operating temperature of 155 ℃ and the operating pressure of normal pressure, and removing low-boiling-point substances after rectification to obtain the MQ resin solution. The resulting product MQ resin (I) was determined to have a molecular weight Mw of 21521 and a molecular weight distribution of 1.4.
Comparative example 1
At 10 ℃, 500g of 12 wt% hydrochloric acid aqueous solution is added into a batch reaction kettle for priming, the maximum rotating speed is started, 1376g of 15 wt% water glass is rapidly added within 5min, and gel appears in the kettle.
Comparative example 2
Reactor a in example 1 was changed to an SK type static mixer, and the rest of the conditions were unchanged. After 5h of continuous run the gel was allowed to set.
Comparative example 3
Reactor A of example 1 was operated to raise the pH to 3.5 by increasing the water glass feed to 1391g/min, with the remainder of the conditions unchanged. The resulting product MQ resin was determined to have a molecular weight Mw of 21371 and a molecular weight distribution of 3.6.
Comparative example 4
The reactor a reflux ratio in example 1 was replaced with 40 and the remaining conditions were unchanged. The resulting product MQ resin was determined to have a molecular weight Mw of 14371 and a molecular weight distribution of 1.7.
It can be seen that, by the comparative examples 1 to 2, in which experiments were carried out by the batch method or the static mixer, it was extremely difficult to stably prepare the high molecular weight MQ resin having a narrow molecular weight distribution by increasing the concentration of the raw material, and gelation occurred very easily.
By comparative examples 3 to 4, when the pH and reflux ratio were out of the range, the system was relatively unstable and the molecular weight distribution was broadened.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. It will be appreciated by those skilled in the art that modifications or adaptations to the invention may be made in light of the teachings of the present specification. Such modifications or adaptations are intended to be within the scope of the present invention as defined in the claims.
Claims (10)
1. A method for continuously preparing controllable high molecular weight MQ resin with low power comprises the steps of preparing polysilicic acid hydrosol, aging, end capping reaction, phase splitting and rectifying to obtain the MQ resin, and is characterized in that the preparation of the polysilicic acid hydrosol comprises the following steps: in the reactor A, hydrochloric acid aqueous solution is continuously added to fill the reactor A, when the pH value in the reactor is less than 2, water glass solution is continuously added into the reactor A, the mixture is continuously extracted and partially flows back, the pH value in the reactor is controlled to be stable, and at the moment, hydrolysis condensation reaction occurs in the reactor A, and polysilicic acid hydrosol is initially formed.
2. The method of claim 1, comprising the steps of:
1) in the reactor A, firstly, continuously adding a hydrochloric acid aqueous solution to fill the reactor A, when the pH value in the reactor is less than 2, continuously adding a water glass solution into the reactor A, continuously extracting and partially refluxing, controlling the pH value in the reactor to be stable, and then carrying out hydrolysis condensation reaction in the reactor A to preliminarily form polysilicic acid hydrosol;
2) in the reactor B, the preliminarily formed polysilicic acid hydrosol is continuously aged to obtain the polysilicic acid hydrosol with certain molecular weight, namely SiO4(iii)/2, Q unit for short;
3) continuously adding the product, alcohol, solvent and end-capping reagent in the reactor B to carry out end-capping reaction in a reactor C;
4) in the reactor D, continuously carrying out phase separation on the product in the reactor C, dividing the product into two phases, namely an organic phase containing MQ resin and a water phase not containing the MQ resin, washing the two phases to be used as wastewater treatment, and continuously washing the organic phase;
5) and in the reactor E, continuously rectifying the water-washed organic phase in the reactor E to obtain the MQ resin.
3. The method as claimed in claim 1 or 2, wherein the reactor A in the step 1) is a LOOP reactor and is composed of a power device, a mixing device and a LOOP, wherein the power device is used for providing power for the extraction and/or the reflux of the reaction liquid, the mixing device is used for the mixing and the reaction of the hydrochloric acid aqueous solution and the water glass solution, and the LOOP is used for the reflux of the reaction liquid;
preferably, the power equipment is selected from one or more of diaphragm pump, centrifugal pump and peristaltic pump, and the power density epsilon is less than 10kW/m3(ii) a The mixing device is a static mixer, preferably selected from SV type, SK type, SX type, SH type and SL type, and the number of units is 1-100.
4. The method as claimed in any one of claims 1 to 3, wherein the pH value in the reactor is controlled to be stabilized at 1 to 3 in the step 1).
5. The method according to any one of claims 1 to 4, wherein the reflux ratio of the reactor A in the step 1) is 2 to 30, the reaction temperature is 10 to 30 ℃, and the residence time is 1 to 3 min.
6. The method according to any one of claims 1 to 5, wherein the mass concentration of the aqueous hydrochloric acid solution in the step 1) is 12% to 36%, preferably 18% to 28%, and the feeding speed is 200 to 600g/min, preferably 300 to 500 g/min; the mass concentration of the water glass solution is 15-36%, preferably 20-30%, and the feeding speed is 800-2087g/min, preferably 1100-1500 g/min; preferably, SiO therein2The molar ratio of HCl/1.48 to 1.60.
7. The method according to any one of claims 1 to 6, wherein the reactor B in the step 2) is a pipeline reactor or a tank reactor for aging of the Q group unit; preferably, the aging time is 2-10 min.
8. The process according to any one of claims 1 to 7, wherein the reactor C in step 3) is a tank reactor, and is mainly used for the capping reaction of the M units to the Q units to form a crude MQ resin;
preferably, the blocking agent is selected from one or more of trimethylchlorosilane, vinyldimethylchlorosilane, hexamethyldisiloxane, tetramethyldisiloxane, divinyltetramethyldisiloxane;
preferably, the solvent is selected from one or more of xylene, toluene, benzene, n-heptane, hexamethyldisiloxane;
preferably, the alcohol is selected from one or more of methanol, ethanol, propanol, isopropanol, isobutanol;
more preferably, the flow rate of the product continuously added into the reactor B in the reactor C is 1000-2687g/min, the flow rate of the alcohol is 450-550g/min, the flow rate of the solvent is 550-750g/min, and the flow rate of the blocking agent is 75-125 g/min.
9. The method according to any one of claims 1 to 8, wherein the reactor D in the step 4) is a continuous water-washing phase separator selected from a kettle-type phase-separation water scrubber or a tower-type water-washing phase separator.
10. The process according to any one of claims 1 to 7, wherein in step 5), the reactor E is a rectification column, and the atmospheric rectification is carried out at an operating temperature of 20 to 30 ℃ higher than the boiling point of the solvent.
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