High-purity ultralow-viscosity dimethyl silicone oil and preparation method thereof
By using triflatesulphonic acid as a catalyst, combined with balanced reaction and distillation technology, the problem of difficult separation of ring impurities and high purity requirements in traditional methods is solved, and the preparation of high purity and low viscosity dimethyl silicone oil is achieved, meeting the daily chemical grade usage requirements.
Patent Information
- Application Number
- CN202510303332.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-14
- Publication Date
- 2025-06-13
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
When producing ultra-low viscosity dimethyl silicone oil, traditional preparation methods have problems such as difficulty in separation of ring impurities, catalysts affect the formation, and high requirements for raw material purity, resulting in low product purity and many by-products, which seriously restricts the production of low viscosity dimethyl silicone oil.
A specific acidic catalyst trifluoromethanesulfonic acid is used to prepare mixed silicone oil with a large content of the target component through the balanced reaction and formulation adjustment, and then distilled in stages through the distillation tower to obtain high-purity and low-viscosity dimethyl silicone oil.
The preparation of ultra-low viscosity dimethyl silicone oil with high purity (>99%) is achieved, which meets the daily chemical grade usage requirements and improves production efficiency and product quality.
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Figure CN120137172A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of materials, and particularly relates to a high-purity ultra-low viscosity dimethyl silicone oil and a preparation method thereof. Background Art
[0002] Traditional volatile silicone oils are mainly cyclotetramethylsiloxane (D4), cyclopentamethylsiloxane (D5), and cyclohexasiloxane (D6), which are widely used in industries such as personal care, cosmetics, medicine, and textiles. They are compounds synthesized by hydrolysis of dimethyldichlorosilane and then purified by rectification. On May 17, 2024, the EU Commission's Amendment No. 2024 / 1328 published in the Official Journal of the European Union imposed new restrictions on D4, D5, and D6 in the list of restricted substances in Annex XVII of the REACH Regulation: as of June 6, 2026, D4, D5, and D6 shall not be placed on the market as substances themselves, components of other substances, or mixtures at a weight concentration equal to or greater than 0.1%.
[0003] Ultra-low viscosity dimethyl silicone oil (especially 1-2 cs silicone oil) has excellent chemical stability, thermal stability, lubricity, and hydrophobicity. It has special requirements and application prospects in the fields of electronics, cosmetics, medicine, etc. For example, in the electronics field, it can be used as a cleaning agent and heat dissipating agent for precision instruments; in cosmetics, it can improve the touch and spreadability of products; in medicine, it can be used as a drug carrier, etc., and can replace EU restricted substances such as D4, D5, and D6.
[0004] However, there are some problems in the traditional preparation method for producing ultra-low viscosity dimethyl silicone oil. In the traditional synthesis process of dimethyl silicone oil, it is easy to generate cyclic impurities such as octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6). The boiling points of these cyclic compounds are very close to those of linear siloxanes, making it difficult to separate them by conventional methods, which seriously affects the purity and performance of the product.
[0005] In addition, in the traditional equilibration reaction, the catalyst may cause the formation of cyclic compounds. At the same time, precise control of its dosage and reaction conditions is required to prepare ultra-low viscosity dimethyl silicone oil, which has extremely high requirements for the purity of raw materials. The presence of impurities in the raw materials may lead to incomplete reactions or the formation of by-products, affecting the product quality.
[0006] Problems such as difficult control of the above reactions, low product purity, and many by-products seriously restrict the production of low viscosity dimethyl silicone oil. Therefore, it is necessary to develop a new preparation method to obtain high-quality ultra-low viscosity dimethyl silicone oil. Summary of the Invention
[0007] The main objective of the present invention is to develop a preparation method for ultra-low viscosity dimethyl silicone oil to obtain high-quality ultra-low viscosity dimethyl silicone oil.
[0008] To achieve the above objective, the present invention discloses a preparation method for ultra-low viscosity dimethyl silicone oil, which is characterized by including the following steps: Step 1: Select dehydrated octamethylcyclotetrasiloxane and hexamethyldisiloxane as raw materials, and prepare an appropriate amount of acidic catalyst. Step 2: Add octamethylcyclotetrasiloxane and hexamethyldisiloxane into a reaction kettle equipped with a stirrer, a thermometer and a reflux condenser in a ratio of 1:1.5 - 2.5. Under stirring conditions, slowly add the acidic catalyst. Step 3: After the reaction is completed, add an alkaline substance to neutralize the reaction system until the system is neutral to remove the acidic catalyst. Step 4: Filter to filter out the salts after neutralization. Step 5: Perform vacuum distillation on the filtered mixture to remove low-boiling impurities and unreacted raw materials to obtain dimethyl silicone oil. Step 6: Perform rectification. Transfer the dimethyl silicone oil after vacuum distillation to a rectification column and fractionally rectify dimethyl silicone oil with viscosities of 1 cs, 1.5 cs, and 2 cs.
[0009] Preferably, in Step 1, the acidic catalyst is selected from concentrated sulfuric acid, acidic ion exchange resin or trifluoromethanesulfonic acid, and the acidic catalyst is preferably trifluoromethanesulfonic acid.
[0010] Preferably, in Step 2, the reaction temperature is controlled at 60 - 80 °C, and the reaction time is 2 - 4 hours.
[0011] Preferably, the alkaline substance in Step 3 is selected from sodium carbonate or sodium bicarbonate.
[0012] Preferably, in Step 5, the distillation pressure of vacuum distillation is controlled at 1 - 5 kPa, and the temperature is 40 - 80 °C.
[0013] The present invention also discloses the application of the above preparation method in the production of ultra-low viscosity dimethyl silicone oil.
[0014] Compared with the prior art, the present invention has the following advantages: In view of the low purity of the components of ultra-low viscosity dimethyl silicone oil in the prior art, most of which are low-viscosity mixed silicone oils. In the present invention, from the perspective of formulation design, ultra-low viscosity dimethyl silicone oil with a viscosity below 5 cs is synthesized. In particular, the proportion of silicone oil with a viscosity of 1-2 cs can account for more than 50% of the total amount of silicone oil (which can be detected and analyzed by gas chromatography). Then, the self-made ultra-low viscosity dimethyl silicone oil is transferred to a rectification column, and silicone oils with viscosities of 1 cs, 1.5 cs, and 2 cs are rectified in segments, with a purity > 99% to meet the requirements for daily chemical grade use. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art and experiments, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.
[0016] Figure 1 GC spectrum of 1 cs silicone oil in Example 1.
[0017] Figure 2 GC spectrum of 1.5 cs silicone oil in Example 1.
[0018] Figure 3 GC spectrum of 2 cs silicone oil in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0019] The technical solutions of the present invention will be described in detail below in conjunction with the drawings and embodiments, but the present invention is not limited to the scope of the described embodiments. The experimental methods and techniques without specific conditions noted in the following embodiments are generally carried out according to the conventional conditions in the relevant field or according to the conditions recommended by the manufacturers.
[0020] The present invention provides a method for preparing ultra-low viscosity dimethyl silicone oil. In this method, organosilicon cyclic bodies and methyl end-capping agents are subjected to an equilibration reaction under acidic conditions. Through formulation adjustment, a mixed silicone oil with a relatively large content of the target components is prepared, and then high-purity and low-viscosity dimethyl silicone oil is refined through a rectification column.
[0021] Example 1: In a 1L reactor, 100g of dehydrated octamethylcyclotetrasiloxane (D4) and 100g of hexamethyldisiloxane (MM) were added. 3g of concentrated sulfuric acid was added under stirring, and the reaction temperature was controlled at 60°C for 3 hours. After the reaction, an appropriate amount of sodium carbonate was added for neutralization, and the filtration was completed. Then, in a vacuum distillation device, under a pressure of 2kPa and a temperature of 70°C, low-boiling components were removed to obtain an ultra-low viscosity dimethyl silicone oil mixture, which was transferred to a rectification column for fractional rectification: The vacuum system was started, the rectification parameters were set, and the fraction at 43°C / -0.01MPa was collected, which was 1cs silicone oil (see the GC chromatogram in Figure 1 , the same below), and the yield reached 8%. Its purity was analyzed to be 99.8%; The fraction at 70°C / -0.01MPa was intercepted, which was 1.5cs silicone oil (see the GC chromatogram in Figure 2 , the same below), and the yield reached 15%. Its purity was analyzed to be 99.7%; The fraction at 95°C / -0.01MPaKPa was intercepted, which was 2cs silicone oil (see the GC chromatogram in Figure 3 , the same below), and the yield was 18%. Its purity was analyzed to be 99.6%; The bottom liquid was taken, and the yield was 48%. Its kinematic viscosity was analyzed to be 4.2cs; The low-boiling components generated during the previous low-boiling removal could be put into the next batch of reactions for recycling.
[0022] Example 2: Using the same device and procedure as in Example 1, the raw materials were changed to 100g of dehydrated D4 and 100g of MM, the catalyst was changed to 0.3g of trifluoromethanesulfonic acid, the reaction temperature was 60°C, and the reaction time was 3 hours. After the reaction, an appropriate amount of sodium carbonate was added for neutralization, and the filtration was completed. Then, in a vacuum distillation device, under a pressure of 2kPa and a temperature of 70°C, vacuum distillation was carried out to obtain an ultra-low viscosity dimethyl silicone oil mixture, which was transferred to a rectification column for fractional rectification: The vacuum system was started, the rectification parameters were set, and the fraction at 43°C / -0.01MPa was collected, which was 1cs silicone oil, and the yield reached 18%. Its purity was analyzed to be 99.79%; The fraction at 70°C / -0.01MPa was intercepted, and the yield reached 17%. Its purity was analyzed to be 99.87%; The fraction at 95°C / -0.01MPaKPa was intercepted, and the yield was 10%. Its purity was analyzed to be 99.68%; The bottom liquid was taken, and the yield was 37%. Its kinematic viscosity was analyzed to be 3.9cs; The low-boiling components generated during the previous low-boiling removal could be put into the next batch of reactions for recycling.
[0023] Example 3: Using the same apparatus and procedures as in Example 1, the raw materials were changed to 100 g of dehydrated D4 and 120 g of MM, the catalyst was changed to 0.3 g of trifluoromethanesulfonic acid, the reaction temperature was 30 °C, and the reaction time was 5 hours. After the reaction, an appropriate amount of sodium carbonate was added for neutralization, and the filtration was completed. Then, in a vacuum distillation apparatus, vacuum distillation was carried out at a pressure of 2 kPa and a temperature of 70 °C to obtain an ultra-low viscosity dimethyl silicone oil mixture, which was transferred to a rectification column for fractional rectification: the vacuum system was turned on, the rectification parameters were set, and the fraction at 43 °C / -0.01 MPa was collected, which was 1 cs silicone oil, with a yield of 17.5%, and its purity was analyzed to be 99.78%; the fraction at 70 °C / -0.01 MPa was intercepted, with a yield of 15%, and its purity was analyzed to be 99.7%; the fraction at 95 °C / -0.01 MPa KPa was intercepted, with a yield of 12%, and its purity was analyzed to be 99.6%; the bottom liquid was taken, with a yield of 37%, and its kinematic viscosity was analyzed to be 3.8 cs; the low-boiling substances generated during the previous low removal can be put into the next batch of reactions for recycling.
[0024] Example 4: Using the same apparatus and procedures as in Example 1, the raw materials were changed to 100 g of dehydrated D4 and 120 g of MM, the catalyst was changed to 0.3 g of trifluoromethanesulfonic acid, the reaction temperature was 60 °C, and the reaction time was 3 hours. After the reaction, an appropriate amount of sodium carbonate was added for neutralization, and the filtration was completed. Then, in a vacuum distillation apparatus, vacuum distillation was carried out at a pressure of 2 kPa and a temperature of 70 °C to obtain an ultra-low viscosity dimethyl silicone oil mixture, which was transferred to a rectification column for fractional rectification: the vacuum system was turned on, the rectification parameters were set, and the fraction at 43 °C / -0.01 MPa was collected, which was 1 cs silicone oil, with a yield of 21%, and its purity was analyzed to be 99.8%; the fraction at 70 °C / -0.01 MPa was intercepted, with a yield of 18%, and its purity was analyzed to be 99.7%; the fraction at 95 °C / -0.01 MPa KPa was intercepted, with a yield of 12%, and its purity was analyzed to be 99.6%; the bottom liquid was taken, with a yield of 36%, and its kinematic viscosity was analyzed to be 3.2 cs; the low-boiling substances generated during the previous low removal can be put into the next batch of reactions for recycling.
[0025] Table 1
[0026] Conclusion: Judging from the results obtained in the present invention, by using the specific acidic catalyst trifluoromethanesulfonic acid in the present invention, compared with sulfuric acid commonly used in the prior art, the proportion of low-viscosity silicone oil in the obtained dimethyl silicone oil is higher.
[0027] Through the above formulation design and rectification, high-purity, low-viscosity and ultra-low-viscosity dimethyl silicone oil can be obtained, with a relatively high yield, which is suitable for industrial production.
[0028] The above embodiments are preferred embodiments of the present invention. However, the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.
Claims
1. A method for preparing ultra-low viscosity dimethyl silicone oil, characterized in that: The following steps are involved: Step 1: Selecting dehydrated octamethylcyclotetrasiloxane and hexamethyldisiloxane as raw materials, and preparing an appropriate amount of acidic catalyst; Step 2: adding octamethylcyclotetrasiloxane and hexamethyldisiloxane in a molar ratio of 1:1.5-2.5 into a reaction kettle equipped with a stirrer, a thermometer and a reflux condenser, and slowly adding an acidic catalyst under stirring; Step 3: After the reaction is completed, add an alkaline substance to neutralize the reaction system until the system is neutral to remove the acidic catalyst; Step 4: Filter the neutralized salt; Step 5: distilling under reduced pressure, distilling the filtered mixture under reduced pressure to remove low-boiling impurities and unreacted raw materials to obtain dimethyl silicone oil; Step 6: distillation, transfer the dimethyl silicone oil after vacuum distillation to a distillation tower, and distill in stages to obtain 1cs, 1.5cs, and 2cs dimethyl silicone oil.
2. The method for preparing an ultra-low viscosity dimethyl silicone oil according to claim 1, characterized in that: Step 1: The acidic catalyst is selected from concentrated sulfuric acid, acidic ion exchange resin or trifluoromethanesulfonic acid.
3. The method for preparing an ultra-low viscosity dimethyl silicone oil according to claim 1, characterized in that: In step 2, the reaction temperature is controlled at 60-80°C and the reaction time is 2-4 hours.
4. The method for preparing an ultra-low viscosity dimethyl silicone oil according to claim 1, characterized in that: The alkaline substance in step 3 is selected from sodium carbonate or sodium bicarbonate.
5. The method for preparing an ultra-low viscosity dimethyl silicone oil according to claim 1, characterized in that: In step 5, the distillation pressure of the reduced pressure distillation is controlled at 1-5 kPa and the temperature is 40-80°C.
6. Application of the preparation method according to any one of claims 1 to 5 in the production of ultra-low viscosity dimethyl silicone oil.