High-viscosity dimethyl silicone oil and preparation method thereof

Abstract

The invention discloses high-viscosity dimethyl silicone oil and a preparation method thereof.The preparation method comprises the following steps that a siloxane polymer is heated, a basic catalyst is added in the inert gas atmosphere, and a first mixture is obtained; continuously heating and adding an end-capping reagent into the first mixture in a vacuum environment for reaction to prepare a second polymer; adding a neutralizer into the second polymer for reaction to obtain a third polymer; and heating and devolatilizing light components in the third polymer in a vacuum environment to obtain the finished product silicone oil. A high-viscosity dimethyl silicone oil product prepared by carrying out a catalytic reaction in a potassium hydroxide silanolate-silicon-based phosphate catalytic neutralization system and then using a linear siloxane oligomer as a main polymer has the advantages of low polymerization intermediate volatile matter, high product viscosity and low molecular weight distribution coefficient, and has a wide application prospect.

Description

Technical Field

[0001] The present application relates to the field of organic silicon technology, and in particular to a high-viscosity dimethyl silicone oil and a preparation method thereof. Background Art

[0002] High viscosity dimethyl silicone oil is a polysiloxane with chain structures of different polymerization degrees. Its general structural formula is MD n M. According to the viscosity range, dimethyl silicone oil can be divided into low viscosity (0.65mm 2 / s~50mm 2 / s), medium viscosity (50mm 2 / s~1000mm 2 / s) and high viscosity (5000mm 2 / s~500000mm 2 / s) three types of specifications. Due to its unique physical and chemical properties, such as high surface activity, low surface tension, hydrophobicity and anti-adhesion, high viscosity dimethyl silicone oil is widely used in the fields of anti-vibration and anti-fouling oil, lubricants, etc., especially in the surface applications of automobiles, aircraft, ships and other equipment.

[0003] The preparation method for producing high-viscosity dimethyl silicone oil in the market mainly adopts the intermittent method, which has the characteristics of less labor, high process overlap, and high production efficiency, but has the disadvantages of difficult catalyst filtration, difficult emulsification, large thermal expansion coefficient, and poor lubricity. In addition, the production of dimethyl silicone oil by enterprises in the industry now mainly focuses on the production and preparation of medium and low viscosity dimethyl silicone oil, while high-viscosity dimethyl silicone oil is often used to replace traditional oily raw materials such as paraffin and vaseline due to its wide range of applications and huge market demand. However, there are few reports on the production of high-viscosity dimethyl silicone oil. Therefore, the market demand for efficient, low-cost and environmentally friendly new preparation methods to produce high-viscosity dimethyl silicone oil is increasingly urgent. Summary of the invention

[0004] One object of the present application is to provide a high-viscosity dimethyl silicone oil and a preparation method thereof, which is beneficial to reducing the molecular weight distribution coefficient of silicone oil products and improving the polymerization uniformity of the product.

[0005] Another object of the present application is to provide a high-viscosity dimethyl silicone oil and a preparation method thereof, which is beneficial to reducing the production process of raw materials and improving the reaction production efficiency.

[0006] Another object of the present application is to provide a high-viscosity dimethyl silicone oil and a preparation method thereof, which is beneficial to reducing the volatile content of silicone oil and improving the product rate and product quality.

[0007] In order to achieve the above purpose, the technical solution adopted in this application is: a high viscosity dimethyl silicone oil and a preparation method thereof, the method comprising the following steps:

[0008] S100, heating the siloxane polymer and adding a basic catalyst under an inert gas atmosphere to obtain a first mixture;

[0009] S200, continuing to raise the temperature and adding a capping agent to the first mixture under vacuum to react to obtain a second polymer;

[0010] S300, adding a neutralizing agent to the second polymer to react, thereby obtaining a third polymer;

[0011] S400, under vacuum environment, the light components in the third polymer are devolatilized by increasing the temperature to obtain finished silicone oil.

[0012] In one embodiment, the siloxane polymer is a linear siloxane oligomer, and the inert gas is one or more of nitrogen and argon.

[0013] In one embodiment, the catalyst is an alkaline catalyst, and the alkaline catalyst includes one or more of potassium hydroxide siliconate, potassium hydroxide, cesium hydroxide and tetramethylammonium hydroxide.

[0014] In one embodiment, in step S200, the end-capping agent is low-viscosity dimethyl silicone oil.

[0015] In one embodiment, in step S300, the neutralizing agent is silicon-based phosphate ester, the amount of silicon-based phosphate ester is 0.04 g to 0.10 g, and the reaction time is 20 min to 40 min.

[0016] In one embodiment, the step S200 specifically includes the steps of: continuing to heat up, stopping the introduction of inert gas, and continuously adding a capping agent to the first mixture under a vacuum environment for reaction, the heating treatment temperature range is 140°C to 165°C, the vacuum degree is -70KPa to -30KPa, the mass fraction of the added capping agent is 0.05wt.% to 5.5wt.%, the continuous addition of the capping agent treatment time is 20min to 50min, and the reaction time is 50min to 100min.

[0017] In one embodiment, the step S100 specifically includes the steps of weighing the siloxane polymer and heating it, adding the alkaline catalyst under an inert gas atmosphere and stirring, the heating treatment temperature range is 115°C to 145°C, the catalyst dosage is 0.02g to 0.08g, and the inert gas flow rate is 5Nm 3 / h-15Nm 3 / h, and the stirring treatment time is 20min to 50min.

[0018] In one embodiment, in step S400, the devolatilization treatment equipment is a low molecular weight device.

[0019] In one embodiment, the step S400 specifically includes the steps of: pressing the silicone oil into a low-molecular-weight remover with an inert gas, and under a vacuum environment, heating to devolatilize the light components in the third polymer to obtain a finished silicone oil, wherein the vacuum degree is not less than -90 KPa, and the heating treatment temperature range is 160°C to 190°C.

[0020] According to another aspect of the present application, a high-viscosity dimethyl silicone oil prepared by the above preparation method is also provided.

[0021] Compared with the prior art, the beneficial effects of this application are:

[0022] (1) The present invention provides a high-viscosity dimethyl silicone oil and a preparation method thereof, wherein linear siloxane oligomers are used as the main polymer to prepare the high-viscosity dimethyl silicone oil, simplifying the production process of octamethylcyclotetrasiloxane produced by cracking siloxane oligomers, further optimizing the production process, and using a continuous method in the preparation process to increase the production rate, so that the production process can be put into large-scale production;

[0023] (2) The present invention provides a high-viscosity dimethyl silicone oil and a preparation method thereof. In the polymerization process, the polymerization is first performed and then a capping agent is continuously added to reduce viscosity to balance the reaction, thereby reducing the molecular weight distribution coefficient of the silicone oil product, reducing the volatile content in the silicone oil polymerization intermediate, improving the reaction yield, and improving the polymerization uniformity of the silicone oil product;

[0024] (3) The present invention provides a high-viscosity dimethyl silicone oil and a preparation method thereof. The process has mild reaction conditions and reaction rate, and reduces the consumption cost during post-processing, which has a promoting effect on the preparation of high-viscosity dimethyl silicone oil. DETAILED DESCRIPTION

[0025] Below, the present application is further described in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0026] It should be noted that the terms "first", "second", etc. in the description and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0027] The terms "including" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0028] The following further describes specific embodiments applicable to the above-mentioned high-viscosity dimethyl silicone oil and its preparation method.

[0029] According to one aspect of the present invention, a high viscosity dimethyl silicone oil and a preparation method thereof, comprising the steps of:

[0030] S100, heating the siloxane polymer and adding a basic catalyst under an inert gas atmosphere to obtain a first mixture;

[0031] S200, continuing to raise the temperature and adding a capping agent to the first mixture under vacuum to react to obtain a second polymer;

[0032] S300, adding a neutralizing agent to the second polymer to react, thereby obtaining a third polymer;

[0033] S400, under vacuum environment, the light components in the third polymer are devolatilized by increasing the temperature to obtain finished silicone oil.

[0034] The high-viscosity dimethyl silicone oil product prepared by the method has a low volatile content of the polymerization intermediate, and thanks to the selection of the alkaline catalyst and the process of continuously adding the end-capping agent, the production process is optimized, and the reaction production efficiency is improved. At the same time, the product polymerization uniformity of the prepared high-viscosity dimethyl silicone oil product is good. The continuous method proposed by the present invention has a simple preparation process, can be mass-produced, further improves production efficiency, and shows a wide range of application prospects in multiple industries.

[0035] In one embodiment, the siloxane polymer is a linear siloxane oligomer, and by directly selecting the linear siloxane oligomer as the main polymer, the step of cracking the siloxane oligomer into octamethylcyclotetrasiloxane is optimized, thereby simplifying the entire production process. In other words, the optimization of this process can not only reduce the complexity of the production process, which is conducive to shortening the reaction time, but also help reduce production costs and operating difficulties, and further improve production efficiency.

[0036] In one embodiment, the inert gas is selected from one or more of nitrogen and argon. More preferably, the inert gas is nitrogen. Both nitrogen and argon can provide an oxygen-free environment for the synthesis reaction, preventing the raw materials from producing side reactions during the heating and dehydration process. Furthermore, nitrogen is widely available in industry, easy to obtain, and has stable chemical properties, and is relatively safe to use.

[0037] In one embodiment, the alkaline catalyst includes one or more of potassium hydroxide silicon alkoxide, potassium hydroxide, cesium hydroxide and tetramethylammonium hydroxide. More preferably, the alkaline catalyst is potassium hydroxide silicon alkoxide. It is understood that the present invention uses colloidal potassium hydroxide silicon alkoxide prepared by reacting a certain amount of octamethylcyclotetrasiloxane and potassium hydroxide powder at 75°C to 130°C by reflux stirring for a period of time.

[0038] It is understandable that acidic catalysts are generally used to promote the reaction in the technology of synthesizing high-viscosity dimethyl silicone oil, but acidic catalysts may cause corrosion to the equipment during the reaction, thereby affecting the service life and safety of the equipment. In addition, acidic catalysts are not easy to separate from raw materials and silicone oil products after the reaction is completed, and silicone oil is preferentially subjected to end-capping agent bond breaking reaction during catalysis, resulting in a slower main chain polymerization rate, thereby reducing the production rate. And it is difficult to remove the acid subsequently, thereby increasing the difficulty and cost of post-processing, so acidic catalysts are not the best catalyst selection for high-viscosity dimethyl silicone oil. In contrast, the alkaline catalyst used in this application has mild reaction conditions and a faster reaction rate, and has good dispersibility, so it is promoted to prepare high-viscosity dimethyl silicone oil.

[0039] In one embodiment, in step S200, the end-capping agent is selected from low-viscosity dimethyl silicone oil. Since the polymerization is first performed and then the end-capping agent is continuously added to perform a viscosity reduction equilibrium reaction, it is beneficial to reduce the molecular weight distribution coefficient of the silicone oil product and improve the polymerization uniformity of the product.

[0040] In one embodiment, in step S300, the neutralizing agent is silicon-based phosphate, and the amount of silicon-based phosphate is 0.04g-0.10g, specifically, the amount of silicon-based phosphate is 0.04g, 0.05g, 0.06g, 0.07g, 0.08g, 0.09g, 0.10g, and more preferably, the amount of silicon-based phosphate is 0.06g-0.10g, and the reaction time is 20min-40min, specifically, the reaction time is 20min, 25min, 30min, 35min, 40min, and more preferably, the reaction time is 30min-40min. By selecting silicon-based phosphate as the neutralizing agent, due to the small hydroxyl end-capping ratio, this means that the hydroxyl content in the silicone oil is low during the neutralization process, which helps to improve the thermal stability and chemical stability of the silicone oil. In other words, since high-purity linear siloxane oligomers are the main polymers in the polymerization reaction and potassium hydroxide silicon alkoxide-silicon-based phosphate is used as the catalytic neutralization system to carry out the catalytic reaction, the physical and chemical properties of silicone oil products are improved, the production steps are further reduced, and the production cost is reduced.

[0041] In one embodiment, the step S200 specifically includes the steps of: continuing to raise the temperature, stopping the introduction of the inert gas, and continuously adding the end-capping agent to the first mixture under a vacuum environment for reaction. By converting from an inert atmosphere to a vacuum environment, the moisture and volatile substances in the reaction system are further effectively removed, thereby reducing the occurrence of side reactions and improving the purity of the silicone oil products prepared subsequently. Furthermore, since the vapor pressure of the reactants is reduced and the presence of oxygen is reduced in a vacuum environment, the risk of side reactions is reduced, and it also helps to improve the reaction efficiency of the end-capping agent, ensure that the end-capping agent can react quickly with the polymer, and control the molecular weight and viscosity of the polymer, thereby improving the synthesis efficiency and product quality of the prepared high-viscosity dimethyl silicone oil.

[0042] In one embodiment, the step S100 specifically includes the steps of weighing the siloxane polymer and heating it, adding an alkaline catalyst under an inert gas atmosphere and stirring. By completely removing water molecules under an inert gas atmosphere, it is prevented that the residual water molecules react with the catalyst, the activity of the catalyst is reduced and the side reactions are caused, thereby affecting the degree of polymerization, polymerization uniformity and final viscosity of the silicone oil product. In other words, the dehydration treatment helps to remove impurities in the raw materials and subsequent products, reduce the cost of post-processing consumption, and further reduce the volatile content in the high-viscosity dimethyl silicone oil product.

[0043] In one embodiment, the temperature range of the heating treatment is 115°C to 145°C, specifically, the heating treatment temperature is 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, the amount of the catalyst is 0.02g to 0.08g, specifically, the amount of the catalyst is 0.02g, 0.03g, 0.04g, 0.05g, 0.06g, 0.07g, 0.08g, and the inert gas flow rate is 5Nm 3 / h-15Nm 3 / h, specifically, the inert gas flow rate is 5Nm 3 / h、10Nm 3 / h、15Nm 3 / h, the stirring treatment time is 20min~50min, specifically, the stirring treatment time can be 20min, 25min, 30min, 35min, 40min, 45min, 50min, and further preferably, the stirring treatment time is 20min~40min. It can be understood that the vapor pressure of water in the raw material can be increased by heating treatment, thereby promoting the evaporation of water from the raw material, which is beneficial to enhance the efficiency of removing water molecules. In other words, since the dehydration reaction is carried out at high temperature, the use of an inert gas atmosphere can avoid unnecessary side reactions of the raw materials during the heating process. In an oxygen-free or low-oxygen environment, many side reactions that may cause the quality of silicone oil products to deteriorate are suppressed, thereby ensuring the purity and performance of the polymer product.

[0044] In one embodiment, the temperature range of the heating treatment is 140°C to 165°C, specifically, the temperature range of the heating treatment is 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, further preferably, the temperature range of the heating treatment is 145°C to 155°C, the vacuum degree is -70KPa to -30KPa, specifically, the vacuum degree is -70KPa, -60KPa, -50KPa, -40KPa, -30KPa, further preferably, the vacuum degree is -70KPa to -50KPa, the mass fraction of the end-capping agent added is 0.05wt.% to 5.50wt.%, specifically, the mass fraction of the end-capping agent is 0.05wt.%, 0.25wt.%, 0.50wt.%, 0.75wt.%, 1. 00wt.%, 2.00wt.%, 3.00wt.%, 4.00wt.%, 5.00wt.%, 5.50wt.%, further preferably, the mass fraction of the end-capping agent is 3.00wt.% to 5.50wt.%, the continuous addition of the end-capping agent treatment time is 20min to 50min, specifically, the end-capping agent treatment time is 20min, 30min, 40min, 50min, further preferably, the end-capping agent treatment time is 20min to 40min, the reaction time is 50min to 100min, specifically, the reaction time is 50min, 60min, 70min, 80min, 90min, 100min, further preferably, the reaction time is 60min to 80min. By adding the end-capping agent, the molecular weight of the polymer product can be effectively controlled, and then the amount of the end-capping agent added can be accurately controlled to prepare a silicone oil product with a specific viscosity. It is understandable that the addition of end-capping agents can improve the thermal and chemical stability of silicone oil products, allowing them to maintain stable performance in various application environments, especially in high temperature or chemically active environments. Precise control of the reaction time of the end-capping agent is conducive to controlling the viscosity and other properties of the silicone oil product, and further improving the uniformity and purity of the polymer product.

[0045] In one embodiment, in the step S400, the devolatilization treatment instrument is selected to be a low-molecular-weight devolatilizer. The devolatilization treatment of dimethyl silicone oil products generally adopts a kettle devolatilization method or a scraper evaporator and devolatilization. In contrast, the kettle devolatilization method is suitable for the devolatilization treatment of low-viscosity silicone oil products. However, when this method is used to devolatilize high-viscosity dimethyl silicone oil products, it will cause the equipment to vibrate greatly, and a thicker liquid silicone oil film will be formed on the heating surface of the devolatilizer, so that the volatile components in the silicone oil product are not completely removed during the devolatilization treatment, thereby reducing the purity of the silicone oil product. Therefore, it takes a long time to repeatedly devolatilize, further affecting production efficiency. The use of a scraper evaporator belongs to a continuous devolatilization method, which has a high heat transfer efficiency and is therefore suitable for the devolatilization treatment of medium and low viscosity silicone oil products. However, this method also has the phenomenon that it will cause the equipment to vibrate greatly during the devolatilization treatment, increase the complexity of operations in the production process, and reduce safety.

[0046] In other words, for the devolatilization of high-viscosity dimethyl silicone oil, a devolatilizer is used for devolatilization. Thanks to the advantages of the devolatilizer, such as larger surface area, simple operation and excellent heat transfer effect, the volatile content in the prepared silicone oil intermediate product is lower, thereby increasing the purity of the silicone oil product.

[0047] In one embodiment, the step S400 specifically includes the steps of: pressing the silicone oil product into a low-molecular-weight remover with an inert gas, and under a vacuum environment, heating and devolatilizing the light components in the third polymer to obtain a finished silicone oil, wherein the vacuum degree is not less than -90KPa, and the temperature range of the heating treatment is 160°C to 190°C, and specifically, the heating treatment temperature can be 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, and further preferably, the temperature range of the heating treatment is 170°C to 190°C. It can be understood that the fluidity of the silicone oil product can be enhanced and its viscosity can be reduced by heating treatment, which is conducive to the diffusion and removal of volatile components. At the same time, the heating treatment can also increase the diffusion coefficient of the volatile component and strengthen the mass transfer process. Devolatilization under vacuum conditions can more thoroughly remove the volatile components in the silicone oil product, thereby improving the purity and quality of the silicone oil product.

[0048] In one embodiment, the high viscosity dimethyl silicone oil and its preparation method are suitable for preparing high viscosity dimethyl silicone oil. The high viscosity dimethyl silicone oil product prepared by using linear siloxane oligomers under potassium hydroxide silicon alkoxide catalysis conditions in the present application has low volatile content of polymerization intermediates, high product viscosity and low molecular weight distribution coefficient. Since the polymerization process adopts a reaction process of first polymerization, then degradation, and then equilibrium to ensure the uniformity of the silicone oil product, the volatile content of the silicone oil polymerization intermediate after the conventional silicone oil reaction equilibrium is in the range of 12-15%. The silicone oil product produced by the preparation method provided in this application has a volatile content of the silicone oil intermediate product after equilibrium of less than 10%. While improving the reaction efficiency of the polymerization reaction, the yield and product quality of the silicone oil product are further improved, so it has a wide range of application prospects.

[0049] Example 1

[0050] (1) Weigh 1000 g of linear siloxane oligomer, heat to 130°C, add 0.04 g of potassium oxide silicon alkoxide and blow in nitrogen at a nitrogen flow rate of 10 Nm 3 / h, and stirred for 30 min under a nitrogen atmosphere to obtain a first mixture product.

[0051] (2) After the temperature is raised to 150° C., the nitrogen blowing is stopped and vacuuming is started, the vacuum degree is -60 KPa, and 0.05 kg of low-viscosity dimethyl silicone oil is continuously added to the stirred first mixture product within 35 minutes for reaction, and the reaction time is 70 minutes to obtain a second polymer product.

[0052] (3) Add 0.08 g of silicon-based phosphate to the second polymer product and continue the reaction for 40 minutes to obtain a third polymer product.

[0053] (4) The heating system, high vacuum media breaking condensation system and material circulation system of the de-low molecular weight device are turned on, and the silicone oil is pressed into the de-low molecular weight device with nitrogen. The third polymer product is placed in a vacuum environment and heated to 180°C. The vacuum degree is -0.095 MPa, and the light components in the third polymer are devolatilized by heating. The devolatilization time is 1 hour. The finished silicone oil enters the silicone oil storage tank, is cooled, and then is filtered and packaged to obtain high-viscosity dimethyl silicone oil.

[0054] Example 2

[0055] The difference between Example 2 and Example 1 is that in step (1), an equal mass of potassium hydroxide solution is used to replace potassium hydroxide siliconate.

[0056] Example 3

[0057] The difference between Example 3 and Example 1 is that in step (1), tetramethylammonium hydroxide alkali gel with an equal mass of active ingredient and a concentration of 20% is used instead of potassium hydroxide siliconate.

[0058] Example 4

[0059] (1) Weigh 1000 g of linear siloxane oligomer, and continuously add 0.05 kg of low-viscosity dimethyl silicone oil within 35 minutes to obtain a first mixture product.

[0060] (2) Raise the temperature to 130° C., add 0.04 g of potassium oxide silicon alkoxide and stir for 30 minutes to obtain a second mixture product.

[0061] (3) Add 0.08 g of silicon-based phosphate to the second mixture product and continue the reaction for 40 minutes to obtain a third polymer product.

[0062] (4) The heating system, high vacuum media breaking condensation system and material circulation system of the de-low molecular weight device are turned on, and the silicone oil is pressed into the de-low molecular weight device with nitrogen. The third polymer product is placed in a vacuum environment and heated to 180°C. The vacuum degree is -0.095 MPa, and the light components in the third polymer are devolatilized by heating. The devolatilization time is 1 hour. The finished silicone oil enters the silicone oil storage tank, is cooled, and then is filtered and packaged to obtain high-viscosity dimethyl silicone oil.

[0063] Example 5

[0064] The difference between Example 5 and Example 1 is that in step (1), octamethylcyclotetrasiloxane is used instead of the linear siloxane oligomer.

[0065] Example 6

[0066] The difference between Example 6 and Example 1 is that in step (1), octamethylcyclotetrasiloxane is used instead of linear siloxane oligomer, and an equal mass of potassium hydroxide solution is used instead of potassium hydroxide siliconate.

[0067] Example 7

[0068] The difference between Example 7 and Example 1 is that in step (1), octamethylcyclotetrasiloxane is used instead of linear siloxane oligomer, and tetramethylammonium hydroxide alkali gel with an equal mass of active ingredient and a concentration of 20% is used instead of potassium hydroxide siliconate.

[0069] Example 8

[0070] (1) Weigh 1000 g of octamethylcyclotetrasiloxane, and continuously add 0.05 kg of low-viscosity dimethyl silicone oil within 35 minutes to obtain a first mixture product.

[0071] (2) Raise the temperature to 130° C., add 0.04 g of potassium oxide silicon alkoxide and stir for 30 minutes to obtain a second mixture product.

[0072] (3) Add 0.08 g of silicon-based phosphate to the second mixture product and continue the reaction for 40 minutes to obtain a third polymer product.

[0073] (4) The heating system, high vacuum media breaking condensation system and material circulation system of the de-low molecular weight device are turned on, and the silicone oil is pressed into the de-low molecular weight device with nitrogen. The third polymer product is placed in a vacuum environment and heated to 180°C. The vacuum degree is -0.095 MPa, and the light components in the third polymer are devolatilized by heating. The devolatilization time is 1 hour. The finished silicone oil enters the silicone oil storage tank, is cooled, and then is filtered and packaged to obtain high-viscosity dimethyl silicone oil.

[0074] Performance Evaluation

[0075] The volatile matter content of the high viscosity dimethyl silicone oil prepared in Examples 1 to 8 was determined by comparing the mass difference of the silicone oil samples before and after heating with reference to the ASTM D4559-99 (2018) test standard. The viscosity of the high viscosity dimethyl silicone oil prepared in Examples 1 to 8 was measured using an IVS800 fully automatic Ubbelohde viscometer, and the molecular weight distribution coefficient of the high viscosity dimethyl silicone oil prepared in Examples 1 to 8 was measured using an Agilent 1260 Infinity II gel permeation chromatograph. The results are shown in Table 1. Table 1: Performance test of high viscosity dimethyl silicone oil

[0076] It is understandable that the selection of different catalysts has a great influence on the performance of the high viscosity dimethyl silicone oil product. Commonly used acidic catalysts include acidic clay, solid acid, concentrated sulfuric acid, etc. Commonly used alkaline catalysts mainly include potassium hydroxide, cesium hydroxide and its silicon alkoxide, temporary catalyst tetramethylammonium hydroxide, etc. Among them, potassium hydroxide silicon alkoxide is a colloidal potassium hydroxide silicon alkoxide solution obtained by a certain amount of octamethylcyclotetrasiloxane and potassium hydroxide powder at 75°C to 130°C by reflux stirring for a period of time, which belongs to one of the alkaline catalysts. As shown in Table 1, it can be seen from Example 1, Example 2 and Example 3 that compared with the use of potassium hydroxide silicon alkoxide as a catalyst in Example 1, it provides a better ability to control the polymerization reaction for the synthesis reaction, which helps to obtain a high viscosity dimethyl silicone oil with a more uniform polymer molecular weight distribution, and further improves the performance of the high viscosity dimethyl silicone oil. Compared with the potassium hydroxide solution selected as the catalyst in Example 2, although it can effectively promote the polymerization reaction, potassium hydroxide, as a strong base, has a certain corrosiveness to the equipment, which is not conducive to large-scale production process, and because the strong base may cause side reactions, thereby affecting the purity and molecular weight distribution coefficient of the product, the high viscosity dimethyl silicone oil prepared in Example 2 has a higher volatile content and molecular weight distribution coefficient of the polymerization intermediate. In Example 3, tetramethylammonium hydroxide alkali gel is used as a catalyst in the preparation process. Since the catalyst breaking process usually involves heating and vacuuming, at this stage, due to the trace amount of catalyst residue, a certain ammonia smell will be emitted, and since tetramethylammonium hydroxide has a certain toxicity, the environmental friendliness is further reduced.

[0077] In other words, the prior art usually uses an acidic catalyst to promote the reaction, however, the acidic catalyst may cause corrosion to the equipment during the reaction, further affecting the service life and safety of the equipment. And the acidic catalyst is not easy to separate from the raw material and the product after the reaction is completed. When catalyzing, the silicone oil is preferentially subjected to a capping agent bond breaking reaction, which makes the main chain polymerization rate slower and the subsequent separation and removal of the acid more difficult, thereby increasing the difficulty and cost of post-processing, and is not the most preferred catalyst for high-viscosity dimethyl silicone oil. For example, when using concentrated sulfuric acid as an acidic catalyst for catalytic reaction, although there is a faster reaction rate and a lower reaction temperature, after preparing high-viscosity dimethyl silicone oil, it is difficult to separate from the product, so it is not suitable for large-scale industrialization. The present application uses a basic catalyst with mild reaction conditions and reaction rate, and it is easy to separate and process with the product after the reaction is complete, so it has a promoting effect on the preparation of high-viscosity dimethyl silicone oil.

[0078] As shown in Table 1, it can be seen from Example 1, Example 4 and Example 8 that the stirring treatment was not carried out under a nitrogen atmosphere before preparation, so that the dehydration treatment was lacking, resulting in moisture in the raw material. In the synthesis process, an alkaline catalyst is used to increase the reaction rate, but in the catalytic reaction, the surface active sites of the catalyst are crucial for the reaction, and the residual water molecules may react with these active sites, thereby reducing the activity of the alkaline catalyst and affecting the catalytic reaction efficiency. On the other hand, the residual water molecules may introduce the generation of side reactions, and the products generated by the side reactions further increase the difficulty of separating and purifying silicone oil products, resulting in a decrease in the selectivity of the polymer product, affecting the quality of the final silicone oil product, and increasing the post-processing cost. As shown in Table 1, in other words, the silicone oil product obtained by Example 4 without dehydration treatment has a higher content of volatile components in the polymerization intermediate, a wider molecular weight distribution, and a lower quality than the silicone oil product obtained in Example 1 after dehydration treatment. It can be understood that in the process of synthesizing high-viscosity dimethyl silicone oil, removing water molecules from the raw material is one of the important steps.

[0079] At present, the process for producing dimethyl silicone oil mainly uses octamethylcyclotetrasiloxane as the main polymer. However, the ring-opening polymerization reaction of octamethylcyclotetrasiloxane during the synthesis process is relatively violent and difficult to control, resulting in harsh reaction conditions and requiring precise temperature and pressure control, thereby increasing production costs. Referring to Example 1 and Example 5, it can be seen that the high-viscosity dimethyl silicone oil product synthesized from linear siloxane oligomers has a lower volatile content of the polymerization intermediate, and reduces the production process of producing octamethylcyclotetrasiloxane by cracking siloxane oligomers, optimizes the production process of high-viscosity dimethyl silicone oil products, thereby improving the reaction production efficiency, and obtaining silicone oil products with greater viscosity and more uniform polymer molecular weight distribution.

[0080] It is understandable that when octamethylcyclotetrasiloxane is selected as the main polymer to prepare high-viscosity dimethyl silicone oil products, a suitable catalytic system and a corresponding end-capping agent are selected for polymerization. Commonly used acidic catalysts include acidic clay, solid acid and concentrated sulfuric acid. However, acidic clay, cationic resin and solid acid have the problem of separation difficulty when blended with high-viscosity dimethyl silicone oil, which increases the cost consumption of subsequent filtration and post-treatment, thereby affecting the production efficiency and product quality of silicone oil products. For example, when concentrated sulfuric acid is used as a catalyst, although the reaction speed is fast and the reaction temperature is low, when blended with the obtained high-viscosity dimethyl silicone oil products, the separation treatment after the reaction is completed is more difficult, which is not conducive to large-scale industrial application. With reference to Example 1, Example 5, Example 6, Example 7 and Example 8, it can be seen that the high-viscosity dimethyl silicone oil products obtained by using alkaline catalysts instead of acidic catalysts have a lower content of volatile components in the polymerization intermediates, and the volatilization loss ratio of the obtained silicone oil products during use is small, so they have better stability and durability. However, compared with the silicone oil product prepared in Example 1, the viscosity of the silicone oil product prepared with octamethylcyclotetrasiloxane as the main polymer is lower than that of the silicone oil product prepared with linear siloxane oligomers as the main polymer, and the prepared product has a larger polymer molecular weight distribution coefficient, the polymerization uniformity of the silicone oil product is not good, and a certain odor is emitted in the polymerization product, further reducing the quality of the product.

[0081] With reference to Example 1, Example 4 and Example 8, it can be seen that adding the end-capping agent first and then the alkaline catalyst during the reaction process can make the reaction process difficult to control due to the early reaction of the end-capping agent with the siloxane, affecting the viscosity control of the silicone oil and ultimately reducing the quality of the silicone oil product. It is understandable that since the polymerization cycle of the reaction is short when the alkaline catalyst is used for the polymerization reaction, adding the end-capping agent before adding the catalyst can extend the reaction time, thereby reducing the reaction efficiency and increasing the production cost.

[0082] In other words, the high-viscosity dimethyl silicone oil prepared by using linear siloxane oligomers as the main polymer and potassium hydroxide siliconate as the alkaline catalyst has the lowest volatile content of the polymerization intermediate, the highest product viscosity and the lowest molecular weight distribution coefficient, and the best product uniformity. The preparation method proposed in the present invention has the characteristics suitable for process development and the potential for large-scale production.

[0083] The above describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited by the above embodiments, and the above embodiments and the specification only describe the principles of the present application. The present application may have various changes and improvements without departing from the spirit and scope of the present application, and these changes and improvements fall within the scope of the present application for which protection is sought. The scope of protection claimed by the present application is defined by the attached claims and their equivalents.

Claims

1. A method for preparing high viscosity dimethyl silicone oil, characterized in that: It includes the following steps : S100, heating the siloxane polymer and adding a basic catalyst under an inert gas atmosphere to obtain a first mixture; S200, continuing to raise the temperature and adding a capping agent to the first mixture under vacuum to react to obtain a second polymer; S300, adding a neutralizing agent to the second polymer to react, thereby obtaining a third polymer; S400, under vacuum environment, the light components in the third polymer are devolatilized by heating to obtain finished silicone oil.

2. The preparation method according to claim 1, characterized in that The siloxane polymer is a linear siloxane oligomer, and the inert gas is selected from one or more of nitrogen and argon.

3. The preparation method according to claim 1, characterized in that: The alkaline catalyst includes one or more of potassium hydroxide siliconate, potassium hydroxide, cesium hydroxide and tetramethylammonium hydroxide.

4. The preparation method according to claim 1, characterized in that: In the step S200, the end-capping agent is low-viscosity dimethyl silicone oil.

5. The preparation method according to claim 1, characterized in that: In the step S300, the neutralizing agent is silicon-based phosphate, the amount of silicon-based phosphate is 0.04 g to 0.10 g, and the reaction time is 20 min to 40 min.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The step S200 specifically includes the steps of continuing to heat up, stopping the introduction of inert gas, and continuously adding a capping agent to the first mixture under a vacuum environment for reaction, wherein the temperature range of the heating treatment is 140°C to 165°C, the vacuum degree is -70KPa to -30KPa, the mass fraction of the added capping agent is 0.05wt.% to 5.5wt.%, the continuous addition of the capping agent treatment time is 20min to 50min, and the reaction time is 50min to 100min.

7. The preparation method according to any one of claims 1 to 5, characterized in that: The step S100 specifically includes the steps of weighing the siloxane polymer and heating it, adding the alkaline catalyst in an inert gas atmosphere and stirring it, wherein the heating treatment temperature range is 115° C. to 145° C., the catalyst dosage is 0.02 g to 0.08 g, and the inert gas flow rate is 5 Nm 3 / h-15Nm 3 / h, and the stirring treatment time is 20min to 50min.

8. The preparation method according to claim 1, characterized in that: In the step S400, the devolatilization treatment equipment is a low molecular weight device.

9. The preparation method according to claim 1, characterized in that: The step S400 specifically includes the steps of: pressing the silicone oil into a low-molecular-weight remover with an inert gas, and heating and devolatilizing the light components in the third polymer under a vacuum environment to obtain a finished silicone oil, wherein the vacuum degree is not less than -90 KPa, and the heating treatment temperature range is 160°C to 190°C.

10. A high viscosity dimethyl silicone oil, characterized in that: The method is prepared by any one of claims 1 to 9.

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