Low viscosity high flash point hyperbranched fluorosilicone oil, preparation method thereof and insulating medium

Abstract

This invention discloses a low-viscosity, high-flash-point hyperbranched fluorosilicone oil, its preparation method, and its insulating medium, belonging to the field of organosilicon polymer materials and electrical insulation technology. The branched fluorosilicone oil is polymerized from branched monomers, hexamethyldisiloxane, and siloxane cyclic compounds; the siloxane cyclic compounds are a mixture of dimethylsiloxane and fluorinated siloxane cyclic compounds. The above components are reacted at 80–120°C in the presence of a catalyst to obtain the hyperbranched fluorosilicone oil. This hyperbranched fluorosilicone oil has a three-dimensional molecular structure, low viscosity, a flash point above 300°C, high breakdown voltage, and an insulation performance retention rate greater than 85% after multiple breakdowns. This invention also discloses the application of this hyperbranched fluorosilicone oil as an insulating medium in power equipment, including at least one of transformers, reactors, instrument transformers, and cable terminals. The hyperbranched fluorosilicone oil provided by this invention is particularly suitable for electrical insulation applications requiring high fire resistance and long-term operational stability.

Description

Technical Field

[0001] This invention belongs to the field of organosilicon polymer materials and electrical insulation technology, specifically relating to a hyperbranched fluorosilicone oil, its preparation method, and its applications. The hyperbranched fluorosilicone oil has a three-dimensional molecular structure, low viscosity, and excellent electrical properties and environmental stability, making it suitable as an insulating medium in high-voltage, high-power-density electrical equipment. Background Technology

[0002] Insulating oil is an indispensable component of transformers: as an insulating medium, it fully fills the gaps between the windings, core, and casing, effectively preventing high-voltage breakdown; as a cooling medium, it dissipates heat through convection circulation, ensuring long-term stable operation of the equipment; in addition, it has the functions of arc extinguishing, protecting materials from oxidation and corrosion, and can promptly diagnose internal latent faults through dissolved gas analysis. For a long time, mineral oil has been widely used in the insulation systems of power equipment. However, mineral oil has disadvantages such as biotoxicity, poor biodegradability, and a low ignition point, making it difficult to meet increasingly stringent fire prevention and environmental protection requirements. In contrast, vegetable oil has a higher ignition point, better fire resistance, and is easily biodegradable, but its poor antioxidant capacity and hygroscopic nature have prevented its widespread application. Silicone oil, as an organosilicon liquid, is currently mainly used in equipment such as railway traction transformers, but the problem of significant degradation in insulation performance after multiple breakdowns is quite prominent. Chinese patent document CN223217606 U discloses a self-extinguishing fluorinated silicone oil insulation and aging test device. It mentions that the fluorinated silicone oil is a fluorinated modified silicone oil with an ignition point exceeding 300°C, making it difficult to ignite and capable of automatically extinguishing the flame after the electric arc stops. The fluorine atoms in the molecule have strong electronegativity, giving the fluorinated silicone oil superior arc-extinguishing ability. However, fluorination modification disrupts the symmetrical structure of methyl silicone oil, increasing molecular rotational energy and resulting in a higher viscosity for fluorinated silicone oil at the same molecular weight, affecting convective heat dissipation. Furthermore, the fluorocarbon chains are prone to breakage under the influence of an electric arc, leading to chain-linking reactions and the formation of cyclic siloxane oligomers. This makes the stability of fluorinated silicone oil lower than that of dimethyl silicone oil. Summary of the Invention

[0003] To address the aforementioned problems in existing technologies, this invention discloses a fluorinated modified silicone oil whose viscosity remains stable at 10-50 mm during use in insulating equipment. 2 It has a flash point of over 300℃ while maintaining a constant temperature, and also improves the stability of fluorinated silicone oil.

[0004] The specific technical solution is as follows: A low-viscosity, high-flash-point branched fluorosilicone oil, characterized in that the structure of the hyperbranched fluorosilicone oil is as follows: or ; In this invention, the fluorinated siloxane cyclic side group (R) f The value is selected from any of the following structures: including but not limited to CF3CH2CH2, C2F5CH2CH2, C3F7CH2CH2, CF3C6H5, FC6H5, where n1, n2, n3, n4, and n5 are any integers from 2 to 50, and the values ​​of n1, n2, n3, n4, and n5 may be the same or different.

[0005] Experiments have shown that the high fluorine content side group R f Fluorosilicone oils can significantly increase their breakdown voltage and decrease their dielectric constant, but the high steric resistance of the side groups will increase the viscosity of the silicone oil. f CF3CH2CH2 and C2F5CH2CH2 are preferred.

[0006] The hyperbranched fluorosilicone oil is prepared by a method comprising the following steps: Branched monomers, hexamethyldisiloxane, and trifluoromethanesulfonic acid are added to a reactor and reacted at 80-100°C for 1-2 hours under stirring and nitrogen protection. Then, siloxane cyclic compounds are added and reacted at 60-160°C for 5-8 hours. After the reaction, anhydrous sodium carbonate is added, and the mixture is filtered and distilled under reduced pressure to remove low-boiling substances, yielding hyperbranched fluorosilicone oil. The siloxane cyclic compounds contain octamethylcyclotetrasiloxane and / or fluorosiloxane cyclic compounds. When octamethylcyclotetrasiloxane and fluorosiloxane cyclic compounds are present, the siloxane cyclic compounds contain both octamethylcyclotetrasiloxane and fluorosiloxane cyclic compounds. The mass ratio of the fluorosiloxane cyclic compounds to octamethylcyclotetrasiloxane is 1:0.1-1, preferably 1:0.1-0.5.

[0007] The branched monomer is selected from one or more of methyltrimethoxysilane, methyltriethoxysilane, tetramethyl orthosilicate, and tetraethyl orthosilicate, and the specific structural formula is as follows: .

[0008] In this invention, the mass ratio of branched monomer to hexamethyldisiloxane is 1:0.5 to 2.

[0009] In this invention, the mass ratio of branched monomer to siloxane cyclic compound is 1:4 to 16.

[0010] In this invention, after adding the siloxane cyclic compound, the reaction temperature is 80–120°C.

[0011] The degree of branching of the fluorosilicone oil described in this invention is adjusted by the mass ratio of branched monomer to end-capping agent hexamethyldisiloxane, while the molecular weight is adjusted by the mass ratio of siloxane cyclic compound to end-capping agent. Specifically, the degree of branching increases with the increase of the mass ratio of branched monomer to end-capping agent, and the molecular weight increases with the increase of the mass ratio of siloxane cyclic compound to end-capping agent. By synergistically controlling the above two mass ratios, the branching structure and molecular size of the fluorosilicone oil can be controlled within a corresponding range, thereby adjusting its viscosity and flash point, so that even low-viscosity fluorosilicone oils can have a high flash point.

[0012] The present invention also provides the use of the hyperbranched fluorosilicone oil in the preparation of an insulating medium for insulating equipment. The invention further discloses the application of branched fluorosilicone oil in electrical equipment, specifically, its use as an insulating medium in electrical equipment.

[0013] The insulating equipment includes at least one of power transformers, reactors, instrument transformers, cable terminals, high-voltage switchgear, gas-insulated switchgear, rotating motors, or power electronic devices. The hyperbranched fluorosilicone oil serves as the insulating medium, used to replace or partially replace mineral insulating oil, vegetable oil, or linear silicone oil in the insulating equipment.

[0014] An insulating medium or insulating device for use in insulating equipment, said insulating medium comprising the defined hyperbranched fluorosilicone oil.

[0015] A method for improving the insulation performance retention rate of an insulating device after multiple breakdowns includes filling the insulating device with a defined hyperbranched fluorosilicone oil as an insulating medium.

[0016] Compared with existing insulating oils, the hyperbranched fluorosilicone oil of the present invention has the following beneficial effects: (1) High flash point and self-extinguishing arc: Its flash point is higher than 300℃, making it difficult to ignite, and it can automatically extinguish the flame after the electric arc stops, meeting the requirements of high fire protection level.

[0017] (2) Excellent arc extinguishing ability: The strong electronegativity of fluorine atoms in the molecule gives it good arc extinguishing performance. At the same time, the branched structure inhibits the breakage of fluorocarbon chains and chain back bite reaction under the action of electric arc, reduces the generation of cyclic siloxane oligomers, thereby improving the insulation stability after multiple breakdowns.

[0018] (3) Suitable viscosity characteristics: By adjusting the mass ratio of branched monomers to end-capping agents and the mass ratio of siloxane cyclic compounds to end-capping agents, a lower viscosity can be obtained while maintaining a higher molecular weight, thereby improving the convective heat dissipation efficiency and overcoming the problem of excessively high viscosity caused by the destruction of the symmetrical structure of linear fluorinated silicone oil. Attached Figure Description

[0019] Figure 1The infrared spectrum of the hyperbranched fluorosilicone oil obtained in Example 1 is shown.

[0020] Figure 2 The 1H NMR spectra of the hyperbranched fluorosilicone oils obtained in Examples 1-6 are shown.

[0021] Figure 3 The TGA thermogravimetric analysis (TGA) of the hyperbranched fluorosilicone oil obtained in Example 1 is shown.

[0022] Figure 4 The TGA thermogravimetric analysis (TGA) of the hyperbranched fluorosilicone oil obtained in Example 2 is shown.

[0023] Figure 5 The TGA thermogravimetric analysis (TGA) of the hyperbranched fluorosilicone oil obtained in Example 3 is shown.

[0024] Figure 6 The TGA thermogravimetric analysis (TGA) of the hyperbranched fluorosilicone oil obtained in Example 4 is shown.

[0025] Figure 7 The TGA thermogravimetric analysis (TGA) of the hyperbranched fluorosilicone oil obtained in Example 5 is shown.

[0026] Figure 8 The TGA thermogravimetric analysis (TGA) of the hyperbranched fluorosilicone oil obtained in Example 6 is shown.

[0027] Figure 9 The figures are physical images of the products of Examples 1-6 and Comparative Example 1. In the figures, number 1 represents Example 1, number 2 represents Example 2, number 3 represents Example 3, number 4 represents Example 4, number 5 represents Example 5, number 6 represents Example 6, and number 7 represents Comparative Example 1. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0029] Example 1 Under a dry nitrogen atmosphere, 140 g of methyltrimethoxysilane, 210 g of tetraethyl orthosilicate, 183 g of hexamethyldisiloxane, and 5 g of trifluoromethanesulfonic acid were added to a 5 L four-necked flask equipped with a stirrer and a constant-pressure dropping funnel. The mixture was heated to 80 °C and reacted for 2 h. Then, 1880 g of trifluoropropylmethylcyclotrisiloxane and 190 g of octamethylcyclotetrasiloxane were added, and the mixture was reacted at 80 °C for 8 h. Finally, 10 g of anhydrous sodium carbonate was added for neutralization, and the mixture was filtered. The filtrate was distilled under reduced pressure at 180 °C and -0.095 MPa to remove volatiles, yielding a colorless, transparent, hyperbranched fluorosilicone oil with the following structural formula: n1, n2, n3, n4, and n5 are 2-15.

[0030] Example 2 Under a dry nitrogen atmosphere, 140 g of methyltrimethoxysilane, 210 g of tetraethyl orthosilicate, 183 g of hexamethyldisiloxane, and 5 g of trifluoromethanesulfonic acid were added to a 5 L four-necked flask equipped with a stirrer and a constant-pressure dropping funnel. The mixture was heated to 80 °C and reacted for 2 h. Then, 2000 g of trifluoropropylmethylcyclotrisiloxane was added, and the mixture was reacted at 80 °C for 8 h. Finally, 10 g of anhydrous sodium carbonate was added for neutralization, and the mixture was filtered. The filtrate was distilled under reduced pressure at 180 °C and -0.095 MPa to remove volatiles, yielding a colorless, transparent, hyperbranched fluorosilicone oil with the following structural formula: n1, n2, n3, n4, and n5 are 2-15.

[0031] Example 3 The experimental procedure was the same as in Example 1, except that the branched monomer was replaced with tetraethyl orthosilicate and the mass ratio of it to hexamethyldisiloxane was 1:1.5 (the total mass of the branched monomer was the same as in Example 1), and the mass ratio of the fluorosiloxane ring to the siloxane ring was 1:0.5 (the total mass of the fluorosiloxane ring and the siloxane ring was the same as in Example 1). The resulting colorless and transparent hyperbranched fluorosilicone oil has the following structural formula: n1, n2, n3, n4, and n5 are 2-15.

[0032] Example 4 The experimental procedure was the same as in Example 1, except that the branched monomer was replaced with methyltriethoxysilane and the mass ratio of it to hexamethyldisiloxane was 1:1 (the total mass of the branched monomer was the same as in Example 1), and the mass ratio of the fluorinated siloxane ring to the siloxane ring was 1:1. The resulting colorless and transparent hyperbranched fluorosilicone oil (the total mass of the fluorinated siloxane ring and the siloxane ring was the same as in Example 1) has the following structural formula: n1, n2, n3, and n4 are 2-15.

[0033] Example 5 The experimental procedure was the same as in Example 1, except that the trifluoropropyl group (CF3CH2CH2) in the cyclic side chain of the fluorosiloxane was replaced with C2F5CH2CH2, and its structural formula is as follows: n1, n2, n3, n4, and n5 are 2-15.

[0034] Example 6 The experimental procedure was the same as in Example 1, except that the trifluoropropyl group (CF3CH2CH2) in the cyclic side chain of the fluorosiloxane was replaced with C4F9CH2CH2, and its structural formula is as follows: n1, n2, n3, n4, and n5 are 10-20.

[0035] Comparative Example 1 Under a dry nitrogen atmosphere, 140 g of methyltrimethoxysilane, 210 g of tetraethyl orthosilicate, 183 g of hexamethyldisiloxane, and 5 g of trifluoromethanesulfonic acid were added to a 5 L four-necked flask equipped with a stirrer and a constant-pressure dropping funnel. The mixture was heated to 80 °C and reacted for 2 h. Then, 1360 g of octamethylcyclotetrasiloxane was added, and the mixture was reacted at 80 °C for 8 h. Finally, 10 g of anhydrous sodium carbonate was added for neutralization, and the mixture was filtered. The filtrate was distilled under reduced pressure at 180 °C and -0.095 MPa to remove volatiles, yielding a colorless and transparent hyperbranched silicone oil. The structural formula of this silicone oil, simulated based on the reactants, is as follows: n1, n2, n3, n4, and n5 are 20-40.

[0036] Comparative Example 2 Purchase commercially available methyl fluorosilicone oil.

[0037] Comparative Example 3 Purchase commercially available silicone oil.

[0038] Performance testing: Closed-cup flash point test: The test shall be conducted in accordance with GB / T 261-2021 "Determination of flash point" using the Binsky-Martin closed-cup cup method.

[0039] Flash point test: The test was conducted according to the Cleveland open cup method of GB / T 3536-2008 "Determination of flash point and fire point of petroleum products".

[0040] Viscosity test: The viscosity of fluorosilicone oil was measured at 25°C using a rotational viscometer in accordance with GB / T 2794-2022 "Determination of viscosity of adhesives".

[0041] Average breakdown voltage test: The test shall be conducted in accordance with GB / T 507-2002 "Determination of Breakdown Voltage of Insulating Oil".

[0042] Fire resistance rating test: in accordance with GB / T 5169.24-2018 "Fire Hazard Testing of Electrical and Electronic Products - Part 24: Guidelines for Fire Hazard Assessment - Insulating Liquids".

[0043] Temperature rise test: The test shall be conducted in accordance with GB / T 1094.2-2013 Power Transformers Part 2: Temperature rise of liquid-immersed transformers.

[0044] The test results of Examples 1-6 and Comparative Examples 1-3 are listed in Table 1.

[0045] Table 1: Performance of different embodiments and comparative examples

[0046] As shown in Table 1, the viscosity of Examples 1-6 remained stable at 30 mm. 2The temperature rise was around 60K, which was below the standard limit and met the requirements. The performance was better than that of the comparative example 2-methyl fluorosilicone oil. The average breakdown voltage was higher than 70 kV. The breakdown voltage stability was expressed by the slope of the fitted curve. 0 indicates that the breakdown voltage is stable, a positive value indicates that the breakdown voltage has increased, and a negative value indicates that the breakdown voltage has decreased. Examples 1-6 all showed excellent self-extinguishing properties. After ignition, the surface reaction formed a complete solid barrier, which isolated oxygen and eventually extinguished the flame.

[0047] As shown in Table 1, the breakdown voltage stability and self-extinguishing properties of Examples 1-6 are superior to those of methyl fluorosilicone oil and silicone oil, and other performance parameters meet the relevant standards of GB6451. This indicates that the hyperbranched fluorosilicone oil of the present invention has high breakdown voltage and strong impact insulation characteristics, demonstrating significant technical advantages. Specifically, compared with methyl fluorosilicone oil, the hyperbranched fluorosilicone oils of Examples 1-6 of the present invention have lower viscosity and lower temperature rise test values, indicating that the hyperbranched fluorosilicone oil of the present invention has good heat dissipation function. Compared with silicone oil, the hyperbranched fluorosilicone oils of Examples 1-6 have higher closed-cup flash point and ignition point, indicating that the hyperbranched fluorosilicone oil of the present invention has better high-temperature resistance. In Example 4, due to the 1:1 mass ratio of fluorinated siloxane rings to siloxane rings, the fluorine content of the silicone oil decreased, and its average breakdown voltage decreased, but it was still higher than 70 kV. In Example 6, due to the large steric hindrance of the side groups, the silicone oil viscosity increased, but the insulation performance was excellent.

[0048] Example 8: Transformer containing hyperbranched fluorosilicone oil insulating medium The hyperbranched fluorosilicone oil prepared in Example 1 was used to fill a 10 kV / 0.4 kV, 1000 kVA oil-immersed transformer, replacing the original mineral oil. Temperature rise and power frequency withstand voltage tests were conducted according to GB / T 1094. The results showed that the temperature rise of the top layer oil was 52 K (below the standard limit of 60 K), the power frequency withstand voltage of 42 kV / 1 min was passed, and the partial discharge was ≤10 pC. After 1000 hours of continuous operation, oil samples were taken for testing; the breakdown voltage remained above 72 kV, and the acid value did not increase, indicating that the insulating medium has good long-term stability.

[0049] It should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A low-viscosity, high-flash-point hyperbranched fluorosilicone oil, characterized in that, The hyperbranched fluorosilicone oil has a hyperbranched molecular structure, the structural formula of which is as follows: or The fluorinated siloxane cyclic side group Rf in the hyperbranched fluorosilicone oil is selected from any one of the following structures: CF3CH2CH2-, C2F5CH2CH2-, C3F7CH2CH2-, CF3C6H4-, FC6H4-, where n1, n2, n3, n4, and n5 are any integers from 2 to 50, and may have the same or different values.

2. The method for preparing hyperbranched fluorosilicone oil according to claim 1, characterized in that, The hyperbranched fluorosilicone oil is produced by the following steps: Branched monomers, hexamethyldisiloxane, and trifluoromethanesulfonic acid are added to a reactor and reacted at 80-100°C for 1-2 hours under stirring and nitrogen protection. Then, siloxane cyclic compounds are added and reacted at 60-160°C for 5-8 hours. After the reaction is completed, anhydrous sodium carbonate is added, and the mixture is filtered and distilled under reduced pressure to remove low-boiling substances, yielding hyperbranched fluorosilicone oil. The siloxane cyclic compounds include octamethylcyclotetrasiloxane and fluorosiloxane cyclic compounds, wherein the mass ratio of the fluorosiloxane cyclic compounds to octamethylcyclotetrasiloxane is 1:0.1-1.

3. The method for preparing hyperbranched fluorosilicone oil according to claim 2, characterized in that, The branched monomer is selected from one or a mixture of two or more of methyltrimethoxysilane, methyltriethoxysilane, tetramethyl orthosilicate, and tetraethyl orthosilicate.

4. The method for preparing hyperbranched fluorosilicone oil according to claim 2, characterized in that, The mass ratio of the branched monomer, hexamethyldisiloxane, and siloxane cyclic compound is 1:0.5 to 2:4 to 16.

5. Use of the hyperbranched fluorosilicone oil according to any one of claims 1-4 in the preparation of an insulating medium for insulating equipment.

6. The use according to claim 5, characterized in that, The insulating equipment includes at least one of power transformers, reactors, instrument transformers, cable terminals, high-voltage switchgear, gas-insulated switchgear, rotating motors, or power electronic devices. The hyperbranched fluorosilicone oil serves as the insulating medium, used to replace or partially replace mineral insulating oil, vegetable oil, or linear silicone oil in the insulating equipment.

7. An insulating medium or insulating device for use in insulating equipment, characterized in that, The insulating medium comprises the hyperbranched fluorosilicone oil as described in claim 1.

8. A method for improving the insulation performance retention rate of insulating equipment after multiple breakdowns, characterized in that, This includes filling the insulating device with the hyperbranched fluorosilicone oil as described in claim 1 as an insulating medium.

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