Multi-branched-chain silicone oil for single-phase immersed cooling liquid and preparation method of multi-branched-chain silicone oil

Abstract

The invention provides multi-branched-chain silicone oil for a single-phase immersed cooling liquid and a preparation method of the multi-branched-chain silicone oil. The multi-branched-chain silicone oil structurally comprises a silicate ester central functional group; and at least three siloxane chain segments connected to the silicate ester central functional group, wherein the siloxane chain segments are grafted with long-chain alkyl groups. A multi-branched chain structure with a silicate ester central functional group as a core is introduced into a silicone oil molecular structure, and a long-chain alkyl group is introduced into a siloxane chain segment, so that the obtained silicone oil can have relatively high molecular weight and relatively low system viscosity at the same time, and a relatively low dielectric constant is kept; therefore, the liquid coolant has excellent flowing property while maintaining good electrical insulation property and chemical stability, and is more suitable for being used as a liquid coolant in a single-phase immersed liquid cooling system.

Description

Technical Field

[0001] This application relates to the field of coolant technology, specifically to a multi-branched silicone oil for single-phase immersion coolants and its preparation method. Background Technology

[0002] Immersion liquid cooling is a technology that dissipates heat by completely immersing electronic devices in a coolant. The coolant directly contacts the heat-generating components, carrying heat away from the system through convection circulation. Compared to traditional air cooling, immersion liquid cooling utilizes the high heat capacity and thermal conductivity of liquids to significantly improve heat exchange efficiency, thus overcoming the heat dissipation bottleneck caused by the limited thermal conductivity of air. With the rapid development of technologies such as artificial intelligence, cloud computing, and 5G communication, the computing density of data centers is constantly increasing, and chip power consumption is continuously rising. The resulting demand for heat dissipation is growing rapidly, and immersion liquid cooling technology is gradually becoming an important development direction for heat dissipation in high-density data centers.

[0003] Depending on whether the coolant undergoes a phase change during operation, immersion liquid cooling technology is generally divided into two approaches: single-phase immersion liquid cooling and phase change immersion liquid cooling. In a single-phase immersion liquid cooling system, the coolant remains liquid throughout the entire circulation process, carrying away the heat generated during equipment operation through its circulation and high specific heat capacity. In contrast, a phase change immersion liquid cooling system utilizes the latent heat absorbed by the coolant during a gas-liquid phase change when heated, and requires a steam condensation and recovery device for working fluid circulation. Comparatively, single-phase immersion liquid cooling systems have a simpler structure, better operational stability, and lower maintenance costs, thus gradually becoming the mainstream in data center liquid cooling applications.

[0004] In single-phase immersion liquid cooling systems, the coolant needs to possess good electrical insulation properties, low viscosity, and high chemical and thermal stability simultaneously. Currently, common immersion coolant base fluids mainly include fluorinated fluids, carbon-based synthetic oils, and silicone oils. Fluorinated fluids typically have good electrical insulation properties and thermal stability, but they are more expensive, and some products have environmental compatibility issues. While carbon-based synthetic oils offer some cost advantages, their structural stability and flash point are relatively low, making them prone to oxidative degradation during long-term use, thus affecting their service life.

[0005] Organosilicon oils are considered a promising class of immersion-type liquid coolants due to their good chemical inertness, electrical insulation properties, and wide operating temperature range. Currently, silicone oil systems used in liquid cooling systems mostly use low-viscosity methyl silicone oil as the base oil, and their thermal conductivity is improved by adding inorganic fillers or introducing aryl silicone oils. For example, patent CN116731689A improves thermal conductivity by introducing inorganic fillers into the silicone oil system; patent CN119410346A improves system performance by introducing aryl silicone oil. Furthermore, patent CN119613724A improves system performance by introducing long-chain alkyl groups into the ends or side chains of the silicone oil molecule.

[0006] On the other hand, to obtain a silicone oil system with high stability, silicone oil polymers with relatively high molecular weights are usually required. However, as the molecular weight of the silicone oil increases, the viscosity of the system also increases significantly, thus affecting the flow performance of the coolant in the circulation system. To reduce the system viscosity, existing technologies also involve diluting the silicone oil system by adding carbon-based oils such as mineral oil. However, due to the polarity differences between different types of oils, stratification or separation can easily occur during long-term circulation of submerged coolants, thereby affecting the stability and service life of the coolant system.

[0007] Therefore, while maintaining the good electrical insulation properties and chemical stability of silicone oil, how to obtain a silicone oil material with both high stability and low viscosity, and which can maintain good flow properties without the addition of carbon-based solvent oil, remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] This application provides a multi-branched silicone oil for single-phase immersion coolants and its preparation method, which solves the problems in the prior art where silicone oils used in single-phase immersion coolants have high viscosity and poor fluidity when the molecular weight is high, and adding carbon-based oils such as mineral oil to reduce viscosity easily leads to system stratification and decreased stability. The resulting silicone oil has low viscosity and good fluidity while maintaining good electrical insulation and chemical stability, thus making it more suitable for the long-term stable operation of single-phase immersion liquid cooling systems.

[0009] In a first aspect, this application provides a multi-branched silicone oil for single-phase immersion coolant, the multi-branched silicone oil comprising: a silicate ester central functional group; and at least three siloxane segments connected to the silicate ester central functional group, wherein long-chain alkyl groups are grafted onto the siloxane segments.

[0010] According to this application, by introducing a multi-branched structure with a silicate ester central functional group into the molecular structure of silicone oil and introducing long-chain alkyl groups into the siloxane segments, the resulting silicone oil can simultaneously possess a high molecular weight and a low system viscosity, while maintaining a low dielectric constant. Thus, while maintaining good electrical insulation performance and chemical stability, it also has excellent flow properties, making it more suitable for use as a coolant in single-phase immersion liquid cooling systems.

[0011] Specifically, in this application, the silicate ester central functional group serves as the connecting core in the molecular structure, connecting with multiple siloxane segments via siloxane bonds to form a siloxane backbone with multi-branched structural characteristics. Compared to traditional linear silicone oils, this multi-branched structure can reduce the degree of entanglement between molecular chains to a certain extent, resulting in a more dispersed spatial configuration of the molecular structure. While maintaining a high molecular weight, it avoids a significant increase in system viscosity, thereby improving the system's flow properties. Simultaneously, the siloxane segments retain the Si–O main chain structure unique to organosilicon materials, giving the material good chemical inertness and excellent electrical insulation properties.

[0012] Furthermore, by introducing long-chain alkyl groups onto the siloxane segments, the long-chain alkyl groups can form flexible organic segment structures on the molecular periphery, creating spatial isolation between molecular chains, thereby further reducing intermolecular forces and improving system fluidity. Simultaneously, since the long-chain alkyl groups are covalently linked to the siloxane segments, they can exist stably within the molecular structure, allowing for viscosity adjustment without the need for additional mineral oil or other carbon-based solvents, avoiding compatibility issues that may arise from mixing different types of oils. Therefore, through the synergistic effect of the silicate ester central functional group, the multi-branched siloxane structure, and the long-chain alkyl groups, the resulting multi-branched silicone oil possesses the stability of organosilicon materials as well as lower viscosity and lower dielectric constant, making it more suitable as a base oil for single-phase submerged coolants.

[0013] In some embodiments, the silicate central functional group includes at least one of orthosilicate groups, disilicate groups linked by C1-C4 alkylene groups, and oligomeric silicate groups.

[0014] In some of the above embodiments, the orthosilicate groups, the disilicate groups linked by C1-C4 alkylene groups, and the oligomeric silicate groups all belong to silicate structures that can provide multiple reaction sites. During the polycondensation reaction, they can act as connecting nodes in the molecular structure, allowing multiple siloxane segments to be connected to the central structure via siloxane bonds, thereby forming a siloxane framework with multi-branched structural characteristics. The multi-branched structure constructed through the aforementioned silicate central functional groups can, on the one hand, reduce entanglement between linear molecular chains while maintaining a high molecular weight, thus helping to reduce system viscosity and improve flow properties; on the other hand, since the main chain formed is still predominantly composed of Si–O–Si bonds, the resulting material can maintain the good chemical stability and electrical insulation properties of the organosilicon system. Furthermore, the multi-branched siloxane framework formed through the aforementioned silicate central structure can also form a relatively stable spatial structure within the molecule, which helps to improve the structural stability of the material under long-term cyclic use conditions. Therefore, by introducing the aforementioned silicate ester central functional group, a multi-branched structure can be constructed at the molecular structure level, enabling the resulting silicone oil to maintain stability while exhibiting good flow properties, thus making it more suitable as a base oil for single-phase submerged coolants.

[0015] In some embodiments, the siloxane segment comprises 1 to 20 -Si-O- segments.

[0016] In some of the above embodiments, by controlling the length of the siloxane segments within the range of 1 to 20 -Si-O- segments, a good balance can be achieved between molecular structural stability and system flow properties. When the siloxane segments are shorter, the overall molecular structure is more compact, which is beneficial for reducing system viscosity and improving flow properties, thus making it easier for the resulting silicone oil to form stable flow during the circulation of the liquid cooling system. When the siloxane segments are appropriately increased, the flexibility and molecular weight of the molecules can be improved to a certain extent, thereby helping to enhance the thermal and chemical stability of the system. By controlling the length of the siloxane segments within the above range, the molecular chain entanglement problem caused by excessively long molecular chains can be avoided while ensuring the high stability of the silicone oil. This results in a multi-branched silicone oil that maintains good electrical insulation properties and chemical stability while having low system viscosity and good flow properties, making it more suitable as a base oil for single-phase submerged coolants.

[0017] In some embodiments, the long-chain alkyl group is a C6-C16 alkyl group.

[0018] In some of the above embodiments, by introducing C6-C16 long-chain alkyl groups onto the siloxane segments, flexible organic segments of a certain length can be formed on the periphery of the molecule, thereby creating spatial separation between adjacent molecules, reducing intermolecular interaction forces, and thus helping to reduce the viscosity of the system and improve overall flow properties. Simultaneously, the long-chain alkyl groups are covalently linked to the siloxane segments, allowing them to exist stably in the molecular structure and resisting migration or separation during long-term cycling, thus helping to maintain the stability of the system structure. Furthermore, alkyl chains of appropriate length can also adjust the overall polarity of the molecule to a certain extent, enabling the material to maintain good electrical insulation properties of the organosilicon system while having a low dielectric constant. Therefore, by introducing C6-C16 long-chain alkyl groups, the flow properties of the silicone oil system can be improved without the addition of carbon-based solvent oil, while maintaining good stability, thereby further enhancing its overall performance as a base oil for single-phase submerged coolants. Preferably, the long-chain alkyl groups are C6-C12 alkyl groups.

[0019] Secondly, this application provides a method for preparing a multi-branched silicone oil for single-phase immersion coolant, comprising the following steps: S1: Polycondensation reaction of polydentate silicate and long-chain alkyl siloxane dual-endogen agent under the action of acid catalyst to obtain a multi-branched siloxane intermediate containing long-chain alkyl groups. S2: The multi-branched siloxane intermediate is subjected to a capping reaction with a methyl capping agent to obtain a multi-branched silicone oil.

[0020] According to this application, a multi-branched siloxane framework structure is constructed by polycondensation reaction of multidentate silicate and long-chain alkylsiloxane dual-capping agent, and the active end groups in the reaction system are capped by methyl capping agent, so that the resulting silicone oil can maintain a high molecular weight while having a low system viscosity and good flow properties, thus making it more suitable as a base oil for single-phase submerged coolant.

[0021] Specifically, in step S1, the multidentate silicate molecule contains multiple silicate functional groups that can participate in the polycondensation reaction. Under the action of an acid catalyst, it can undergo a polycondensation reaction with a long-chain alkylsiloxane dual-endogen agent, connecting multiple siloxane segments to the same central structure through the formation of Si-O-Si bonds, thereby constructing a siloxane framework with multi-branched characteristics. This multi-branched structure can reduce the entanglement between linear molecular chains to a certain extent, allowing the obtained silicone oil to maintain a high molecular weight while avoiding a significant increase in system viscosity, and is beneficial to improving the system's flow properties.

[0022] Furthermore, in step S2, a methyl end-capping agent is added to cap the active end groups such as silanol or alkoxy groups in the reaction system, converting them into stable siloxane structures, thereby terminating the polycondensation reaction and stabilizing the molecular structure. This end-capping step effectively controls the molecular weight distribution of the product and prevents further polycondensation reactions during subsequent storage or use, thus contributing to improved structural and operational stability of the obtained multi-branched silicone oil. Therefore, through the synergistic effect of the polycondensation reaction and the end-capping reaction, a structurally stable multi-branched silicone oil with good flow properties can be obtained, making it more suitable for single-phase immersion coolant systems.

[0023] It should be noted that, in this application, "polydentate silicate" refers to a silicon compound whose molecular structure contains three or more silicate functional groups capable of participating in polycondensation reactions. These compounds typically contain two or more Si(OR) groups. x The structural unit can provide multiple reaction sites during the polycondensation reaction, thus serving as a connecting node in the molecular structure. This allows multiple siloxane segments to be connected to the same central structure through Si–O–Si bonds, thereby forming a siloxane skeleton with multi-branched structural features.

[0024] In some implementations, in step S1, The polydentate silicate includes at least one of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, dimethyl orthosilicate, trimermethyl orthosilicate, bis(trimethoxysilyl)ethane, and bis(methyldimethoxysilyl)ethane; The long-chain alkylsiloxane dual-capping agent includes at least one of tetramethyldihexyldisiloxane, tetramethyldioctyldisiloxane, tetramethyldidecyldisiloxane, tetramethyldi(dodecyl)disiloxane, tetramethyldi(tetradecyl)disiloxane, and tetramethyldi(hexadecyl)disiloxane. The acid catalyst includes at least one of a strong acid sulfonic acid resin and zirconium sulfate.

[0025] In some of the above embodiments, by selecting silicon compounds containing multiple silicate functional groups as polydentate silicates, multiple reaction sites can be provided during the polycondensation reaction, which is beneficial for constructing a multi-branched siloxane framework structure with the silicate structure as the central node. Simultaneously, the long-chain alkylsiloxane dual-heading agent contains siloxane structures and long-chain alkyl groups, which can participate in the formation of Si-O-Si bonds during the polycondensation process, stably introducing the long-chain alkyl groups into the siloxane framework structure. This allows for the regulation of the organic segments surrounding the molecular structure while constructing a multi-branched structure, which helps reduce intermolecular forces and improve the system's flow properties.

[0026] Furthermore, the acid catalyst effectively promotes the polycondensation reaction between silicate functional groups, enabling the siloxane framework structure to form under milder conditions, thereby improving reaction efficiency and reducing side reactions. Through the synergistic effect of the multidentate silicate, long-chain alkylsiloxane dual-endogen agent, and acid catalyst, a siloxane system with multi-branched structural characteristics can be constructed more stably, thus facilitating the acquisition of multi-branched silicone oils with both high stability and good flow properties.

[0027] In some implementations, in step S1, The molar ratio of the multidentate silicate and the long-chain alkylsiloxane dual-end-capping agent is 1:4~6; The amount of acid catalyst used is 0.1wt% to 5wt% of the amount of polydentate silicate.

[0028] In some of the above embodiments, by controlling the molar ratio of polydentate silicate to long-chain alkylsiloxane dual-terminant within the range of 1:4 to 6, multiple silicate functional groups in the polydentate silicate and the long-chain alkylsiloxane dual-terminant can fully participate in the polycondensation reaction, thereby facilitating the formation of a relatively uniform multi-branched siloxane framework. When the proportion of the long-chain alkylsiloxane dual-terminant is too low, some reaction sites in the polydentate silicate may not be able to fully participate in the polycondensation reaction, thus affecting the formation of the multi-branched structure; while when its proportion is too high, it may lead to too many siloxane segments participating in the reaction, which is not conducive to the effective construction of the multi-branched structure. By controlling the molar ratio of the two within the above range, the polycondensation reaction can be more complete, thereby facilitating the obtaining of structurally stable multi-branched siloxane intermediates.

[0029] Meanwhile, by controlling the amount of acid catalyst within the range of 0.1wt% to 5wt% of the amount of multidentate silicate, the side reaction problems caused by excessive catalyst can be avoided while ensuring the smooth progress of polycondensation reaction. This improves the reaction efficiency while maintaining the stability of the reaction system, thus facilitating the acquisition of structurally stable multi-branched silicone oil.

[0030] In some embodiments, the conditions for the polycondensation reaction in step S1 include reacting at 65~150°C for 2~12 hours.

[0031] In some of the above embodiments, by controlling the reaction temperature and reaction time within the above range, the polycondensation reaction between the multidentate silicate and the long-chain alkylsiloxane dual-endogen can proceed smoothly, thereby facilitating the formation of a structurally stable multi-branched siloxane intermediate.

[0032] In some embodiments, in step S1, a chain extender is also added to the system, the chain extender including dimethyldimethoxysilane, and the molar ratio of the polydentate silicate to the chain extender is 1:2~10.

[0033] In some of the above embodiments, by adding a chain extender to the polycondensation reaction system, the chain extender can participate in the formation of Si-O-Si bonds, introducing or extending siloxane segments between the central structures of the polydentate silicate, thereby facilitating the adjustment of the length and distribution of siloxane segments in the multi-branched siloxane structure. When the molar ratio of the polydentate silicate to the chain extender is controlled within the above range, siloxane segments of appropriate length can be formed while avoiding excessively long segments, thus enabling the obtained multi-branched silicone oil to maintain a high molecular weight while still possessing low viscosity and good flow properties.

[0034] In some embodiments, the molar ratio of the methyl end-capping agent in step S2 to the multidentate silicate in step S1 is 1:1 to 4; the methyl end-capping agent includes at least one of hexamethyldisiloxane and trimethylchlorosilane.

[0035] In some of the above embodiments, by adding a methyl end-capping agent, it can react with the active silanol or alkoxy groups in the multi-branched siloxane intermediate, thereby end-capping the siloxane segments, inhibiting further polycondensation reactions, and stabilizing the multi-branched siloxane structure. When the molar ratio of the methyl end-capping agent to the multidentate silicate is controlled within the above range, the end-capping reaction can be ensured to proceed fully while avoiding the adverse effects of excessive end-capping agent on the system composition, thus facilitating the acquisition of a structurally stable and compositionally uniform multi-branched silicone oil.

[0036] Compared with the prior art, the beneficial effects of this application are at least as follows: This application introduces a silicate ester central functional group into the molecular structure and attaches multiple siloxane segments around it, while simultaneously grafting long-chain alkyl groups onto the siloxane segments, thereby constructing a multi-branched silicone oil molecule. This structure allows the molecule to have both a high molecular weight and maintain low intermolecular forces, resulting in a multi-branched silicone oil with low viscosity, low dielectric constant, and good flow properties. Furthermore, through the synergistic effect of the multi-branched structure and long-chain alkyl groups, the material maintains the excellent chemical stability and electrical insulation properties of the organosilicon system while also maintaining good flowability and system stability without the introduction of mineral oil or carbon-based solvent oil. This helps to avoid the problems of liquid separation or performance degradation in submerged coolants during long-term cyclic use. Therefore, the multi-branched silicone oil provided in this application has good application prospects as a base oil for single-phase submerged coolants with high stability and low viscosity. Attached Figure Description

[0037] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0038] Figure 1 The Fourier transform infrared (FT-IR) spectra of the products and intermediate products in some embodiments are shown.

[0039] Figure 2 The following are the proton NMR spectra of the products and intermediates in some embodiments. 1 H-MNR).

[0040] Figure 3 The following are the carbon NMR spectra of the products in some embodiments. 13 C-MNR).

[0041] Figure 4 The following are the NMR silicon spectra of the products and intermediates in some embodiments. 29 Si-MNR). Detailed Implementation

[0042] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0043] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0044] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0045] In this specification, unless otherwise specified, "parts" refers to "parts by weight".

[0046] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0047] Preparation Example 1 Preparation of tetramethyldihexyldisiloxane: 176g of n-hexene and 1g of caster catalyst were added to a three-necked flask and stirred and heated to 70°C under nitrogen protection. Then, 134g of tetramethyldihydrodisiloxane was slowly added dropwise, and the reaction was carried out in steps from 70 to 120°C. The reaction solution was washed with water, separated, and decolorized with activated carbon. The product was distilled to remove unreacted n-hexene and a small amount of tetramethylhexyldihydrodisiloxane, yielding 278g of tetramethyldihexyldisiloxane, with a yield of 92%.

[0048] Preparation Example 2 Preparation of tetramethyldioctyldisiloxane: 235g of n-octene and 1g of caster catalyst were added to a three-necked flask and stirred and heated to 70°C under nitrogen protection. Then, 134g of tetramethyldihydrodisiloxane was slowly added dropwise, and the reaction was carried out in steps from 70 to 120°C. The reaction solution was washed with water, separated, and decolorized with activated carbon. The product was distilled to remove unreacted n-hexene and a small amount of tetramethyl-octyl-hydrodisiloxane, yielding 336g of tetramethyldioctyldisiloxane, with a yield of 94%.

[0049] Preparation Example 3 Preparation of tetramethyldi(dodecyl)disiloxane: 353g of n-dodecene and 1g of caster catalyst were added to a three-necked flask and stirred and heated to 70°C under nitrogen protection. Then, 134g of tetramethyldihydrodisiloxane was slowly added dropwise, and the reaction was carried out in steps from 70 to 120°C. The reaction solution was washed with water, separated, and decolorized with activated carbon. The product was distilled to remove unreacted n-dodecene and a small amount of tetramethyl-dodecyl-dihydrodisiloxane, yielding 414g of tetramethyldi(dodecyl)disiloxane, with a yield of 88%.

[0050] Preparation Example 4 Preparation of tetramethyldi(hexadecyl)disiloxane: 470g of n-hexadecene and 1g of caster catalyst were added to a three-necked flask and stirred and heated to 70°C under nitrogen protection. Then, 134g of tetramethyldihydrodisiloxane was slowly added dropwise, and the reaction was carried out in a stepwise manner from 70 to 120°C. The reaction solution was washed with water, separated, and decolorized with activated carbon. The product was distilled to remove unreacted n-hexadecene and a small amount of tetramethyl-hexadecyl-hydrodisiloxane, yielding 466g of tetramethyldis(hexadecyl)disiloxane, with a yield of 80%.

[0051] Example 1 Preparation of multi-branched silicone oils for single-phase submerged coolants: 302g of tetramethyldihexyldisiloxane and 3g of sulfonic acid resin were added to a three-necked flask, stirred and heated to 70°C, and 76g of tetramethoxysilane was slowly added dropwise. During the reaction, methanol was gradually separated out by a water separator. The reaction was continued until there was no reflux and then kept at the temperature for 2 hours. Subsequently, 10g of trimethylchlorosilane was added dropwise and the reaction was kept at the temperature for 1 hour. The temperature was then lowered and the sulfonic acid resin was separated by pouring. The mother liquor was distilled under reduced pressure to remove unreacted low-boiling substances. It was then washed successively with saturated sodium carbonate aqueous solution and deionized water, decolorized with activated carbon, and degraded under high vacuum to obtain 308g of hexyl-terminated multi-branched silicone oil.

[0052] Example 2 Preparation of multi-branched silicone oils for single-phase submerged coolants: 358g of tetramethyldioctyldisiloxane and 5g of sulfonic acid resin were added to a three-necked flask, stirred and heated to 70°C, and 76g of tetramethoxysilane was slowly added dropwise. During the reaction, methanol was gradually separated out by a water separator. The reaction was continued until there was no reflux and then kept at the temperature for 2 hours. Subsequently, 20g of trimethylchlorosilane was added dropwise and the reaction was kept at the temperature for 1 hour before cooling. The sulfonic acid resin was separated by pouring, and the mother liquor was distilled under reduced pressure to remove low-boiling substances. Then, it was washed successively with saturated sodium carbonate aqueous solution and deionized water, decolorized with activated carbon, and degraded under high vacuum to obtain 375g of octyl-terminated multi-branched silicone oil.

[0053] Example 3 Preparation of multi-branched silicone oils for single-phase submerged coolants: 470g of tetramethyldis(dodecyl)disiloxane and 20g of sulfonic acid resin were added to a three-necked flask. The mixture was stirred and heated to 70°C. 76g of tetramethoxysilane was slowly added dropwise. During the reaction, methanol was gradually separated out by a water separator. The reaction was continued until no reflux was observed, and then the temperature was raised to 100°C and maintained for 2 hours. Subsequently, 20g of hexamethyldisiloxane was added dropwise and the reaction was maintained for another hour before cooling. The sulfonic acid resin was then separated by pouring. The mother liquor was distilled under reduced pressure to remove low-boiling substances. It was then washed successively with saturated sodium carbonate aqueous solution and deionized water, decolorized with activated carbon, and degraded under high vacuum to obtain 477g of dodecyl-terminated multi-branched silicone oil.

[0054] Example 4 Preparation of multi-branched silicone oils for single-phase submerged coolants: 582g of tetramethyldis(hexadecyl)disiloxane and 25g of sulfonic acid resin were added to a three-necked flask, stirred and heated to 70°C, and 76g of tetramethoxysilane was slowly added dropwise. During the reaction, methanol was gradually separated out by a water separator. The reaction was continued until there was no reflux and then kept at the temperature for 2 hours. Subsequently, 20g of trimethylchlorosilane was added dropwise and the reaction was kept at the temperature for 1 hour. The temperature was then lowered and the sulfonic acid resin was decanted to separate the resin. The mother liquor was distilled under reduced pressure to remove low-boiling substances, and then washed successively with saturated sodium carbonate aqueous solution and deionized water. The solution was decolorized with activated carbon and deionized under high vacuum to obtain 493g of hexadecyl-terminated multi-branched silicone oil.

[0055] Example 5 Preparation of multi-branched silicone oils for single-phase submerged coolants: 358g of tetramethyldioctyldisiloxane, 240g of dimethyldimethoxysilane, and 20g of sulfonic acid resin were added to a three-necked flask. The mixture was stirred and heated to 70°C. 76g of tetramethoxysilane was added dropwise. During the reaction, methanol was gradually separated out by a water separator. The reaction was continued until no reflux was observed, and then kept at the temperature for 2 hours. Subsequently, 50g of trimethylchlorosilane was added dropwise, and the reaction was kept at the temperature for another 1 hour before cooling. The sulfonic acid resin was then separated by pouring. The mother liquor was distilled under reduced pressure to remove low-boiling substances. It was then washed successively with saturated sodium carbonate aqueous solution and deionized water, decolorized with activated carbon, and degraded under high vacuum to obtain 501g of octyl-terminated multi-branched silicone oil.

[0056] Examples 6 to 15 Preparation of multi-branched silicone oils for single-phase submerged coolants: It is largely the same as Example 5, except that some raw materials are used differently, as shown in Table 1.

[0057] The Fourier transform infrared spectra, proton nuclear magnetic resonance (HMR) spectra, carbon nuclear magnetic resonance (CMR) spectra, and silicon nuclear magnetic resonance (SMR) spectra of the products and intermediates obtained in the above embodiments are as follows: Figures 1-4 As shown.

[0058] Figure 1 The figures show the Fourier transform infrared (FT-IR) spectra of the products and intermediates in some embodiments. As can be seen from the comparison, the absorption peaks of the multi-branched silicone oil product and its corresponding intermediate dual-endopeptide in the same embodiment are not significantly different. Based on the analysis of the assignment of each absorption peak and its structural correspondence, it can be concluded that the end-capping of long-chain alkyl silanes has been completed by grafting onto the silicate ester center. Because the product structures in each embodiment are similar, with only differences in alkyl length, the shapes of their absorption peaks are not significantly different, with a slight difference at 1463 cm⁻¹. -1 At this point, the peak represents the bending vibration of -CH2-. The longer the alkyl chain segment, the more -CH2- there is, and the higher the absorption peak intensity, which is consistent with the molecular structure.

[0059] Figure 2 The following are the proton NMR spectra of the products and intermediates in some embodiments. 1 As shown in the H-MNR figure, the absorption peaks of the multi-branched silicone oil product and its corresponding intermediate dual-capping agent in the same embodiment are not significantly different, which is consistent with their structural characteristics. The chemical shifts of H at different positions on each functional group can be found as corresponding peaks in the spectrum. The peak located at 1.25~1.30 ppm represents the methylene-CH2- peak, and its absorption peak increases significantly with the increase of the alkyl chain, while the absorption peaks at other positions remain unchanged.

[0060] Figure 3 The following are the carbon NMR spectra of the products in some embodiments. 13According to the changes in alkyl chain length, the carbon absorption peaks corresponding to each embodiment are significantly different, and the carbon atoms at the corresponding positions can be found based on the absorption peaks.

[0061] Figure 4 The following are the NMR silicon spectra of the products and intermediates in some embodiments. 29 (Si-MNR). In the molecular structure of the long-chain alkyl multi-branched silicone oil designed in this invention, the symmetry of each branch structure is good, and the chemical shifts corresponding to Si and alkyl-substituted Si in the silicate ester are all in the range of 0~20ppm, which correspond one-to-one with the absorption peak energies in the figure.

[0062] comprehensive Figures 1-4 This demonstrates that multi-branched silicone oils with different alkyl lengths involved in this invention have been successfully prepared.

[0063] Table 1

[0064] Note: In Table 1, " / " indicates that the component was not added.

[0065] Test section: The test method for kinematic viscosity shall be performed in accordance with the provisions of national standard GB / T 265-2010; The pour point test method shall be performed in accordance with the provisions of national standard GB / T 3535-2006; The flash point test method shall be performed in accordance with the provisions of national standard GB / T 261-2021; The breakdown voltage test method shall be performed in accordance with the provisions of national standard GB / T 16927.1-2011.

[0066] The test results are shown in Table 2.

[0067] Table 2

[0068] Note: “—” in Table 2 indicates that the data was not measured.

[0069] As shown in Table 2, the viscosity of the multi-branched silicone oils prepared in each embodiment of this application is 3.3~15.2 mm at 25°C. 2 The multi-branched silicone oil exhibits good flow properties even at -20°C, while also possessing a low pour point (below -40°C) and high electrical breakdown strength (26.0~32.3kV / mm). Furthermore, the high flash point (183~246°C) indicates excellent thermal stability and safety. Therefore, the multi-branched silicone oil provided in this application demonstrates excellent comprehensive performance in terms of viscosity, low-temperature flowability, electrical insulation properties, and thermal stability, meeting the performance requirements of single-phase submerged coolants for base oils.

[0070] Further analysis of the data shows that the overall performance of each embodiment is good. Selection can be made based on specific needs. Generally, the longer the alkyl chain segment, the higher the freezing point, which is unfavorable for use in low-temperature environments, but the flash point will be correspondingly higher. Relatively speaking, multi-branched silicone oils containing 6-12 carbon alkyl branches have better overall performance.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A multi-branched silicone oil for use in single-phase submerged coolants, characterized in that, The structure of the multi-branched silicone oil includes: Silicate central functional group; And at least three siloxane segments connected to the central functional group of the silicate ester, wherein long-chain alkyl groups are grafted onto the siloxane segments.

2. The multi-branched silicone oil according to claim 1, characterized in that, The silicate ester central functional group includes at least one of the following: orthosilicate group, disilicate group linked by C1-C4 alkylene groups, and oligomeric silicate group.

3. The multi-branched silicone oil according to claim 1, characterized in that, The siloxane segment comprises 1 to 20 -Si-O- segments.

4. The multi-branched silicone oil according to claim 1, characterized in that, The long-chain alkyl group is a C6~C16 alkyl group.

5. A method for preparing a multi-branched silicone oil for use in single-phase submerged coolants, characterized in that, Includes the following steps: S1: Polycondensation reaction of polydentate silicate and long-chain alkyl siloxane dual-endogen agent under the action of acid catalyst to obtain a multi-branched siloxane intermediate containing long-chain alkyl groups. S2: The multi-branched siloxane intermediate is subjected to a capping reaction with a methyl capping agent to obtain a multi-branched silicone oil.

6. The method according to claim 5, characterized in that, In step S1 The multidentate silicate includes at least one of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, methyltrimethoxysilane, dimethyl orthosilicate, trimomethyl orthosilicate, bis(trimethoxysilyl)ethane, and bis(methyldimethoxysilyl)ethane; The long-chain alkylsiloxane dual-capping agent includes at least one of tetramethyldihexyldisiloxane, tetramethyldioctyldisiloxane, tetramethyldidecyldisiloxane, tetramethyldi(dodecyl)disiloxane, tetramethyldi(tetradecyl)disiloxane, and tetramethyldi(hexadecyl)disiloxane. The acid catalyst includes at least one of a strong acid sulfonic acid resin and zirconium sulfate.

7. The method according to claim 5, characterized in that, In step S1 The molar ratio of the multidentate silicate and the long-chain alkylsiloxane dual-end-capping agent is 1:4~6; The amount of acid catalyst used is 0.1wt% to 5wt% of the amount of polydentate silicate.

8. The method according to claim 5, characterized in that, In step S1 The conditions for the polycondensation reaction include reacting at 65~150℃ for 2~12 hours.

9. The method according to claim 5, characterized in that, In step S1 The system also contains a chain extender, which includes dimethyldimethoxysilane, and the molar ratio of the polydentate silicate to the chain extender is 1:2~10.

10. The method according to claim 5, characterized in that, In step S2, the molar ratio of the methyl end-capping agent to the multidentate silicate in step S1 is 1:1 to 4; the methyl end-capping agent includes at least one of hexamethyldisiloxane and trimethylchlorosilane.

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