A fluorine-free liquid coolant, its preparation method and application

Abstract

The present invention provides a fluorine-free liquid coolant and its preparation method and application, belonging to the technical field of liquid coolants. The present invention is a straight-chain alkyl-modified polysiloxane with a specific number of carbon atoms in the whole chain segment, and its molecular structure has clarity and specificity, avoiding problems such as excessive numbers of chain alkyl carbon atoms and siloxane chain segments, too large molecular weight, too high viscosity, and the need to add solvent and other components to reduce viscosity and improve fluidity when used as a liquid cooling medium; and on the basis of low viscosity (<50 cSt / 40 °C), the physical property indexes such as boiling point, flash point, dielectric constant, volume resistivity, thermal conductivity, specific heat capacity, health and environmental protection are all superior to those of mainstream fluorinated liquid immersion coolants such as perfluoropolyether, fully meeting and exceeding the specification standards of YD / T 3982-2021 "Technical Requirements and Test Methods for Cooling Liquids in Data Center Liquid Cooling Systems", being able to meet the higher demands of the industry, and being an upgraded alternative product to fluorinated liquid immersion coolants.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid coolants, and particularly to a fluorine-free liquid coolant, a preparation method thereof, and an application thereof. Background Art

[0002] In fields such as IT and communication, the cooling media used for cooling semiconductor cooling plates and immersion cooling in data centers include mineral oil, polyolefin synthetic oil (PAO), dimethyl silicone oil (PDMS), fluorinated materials, fluorine-free liquid coolants, etc.

[0003] Mineral oil is relatively inexpensive and can play a role in heat transfer. However, during use, due to its inherent characteristics, it will bring potential dangers and hazards. For example, mineral oil contains corrosive impurities such as sulfur, which will cause rust on equipment such as Tank boxes and heat exchangers and cause impurity pollution to the cooling system; mineral oil will cause swelling of ethylene propylene diene monomer (EPDM) insulation parts and seals, and long-term use may lead to failures of CBB capacitors; mineral oil has flammability and degradation problems over time;

[0004] PAO has properties similar to and superior to those of mineral oil, but the risk of swelling of EPMD and direct contact with data center equipment still exists;

[0005] PDMS has outstanding advantages in terms of temperature resistance, degradation resistance, safety and health. However, due to the inevitable large amount of silicone rubber encapsulation, coating, sheath, miscellaneous parts, and silicone rubber adhesives in data center electronic components, long-term use of PDMS may cause problems such as swelling, delamination, shedding, and reduced thermal coupling of silicone rubber, resulting in data center equipment failures;

[0006] Fluorinated liquid belongs to organic fluorine products and is favored because of its colorless, odorless, insulating, and non-flammable characteristics. Perfluoropolyether (PFC) is a high-end product in fluorinated liquids and is also the mainstream fluorinated liquid variety commercially used for immersion liquid cooling at present. It is also one of the main liquid coolant products used for immersion liquid cooling. However, fluorinated liquids including perfluoropolyether have the common properties of high density, high cost, physiological toxicity, ozone layer depletion, and high global warming potential; especially fluorine is called the "dead element", and fluorinated liquid is a class III carcinogen, which has a great potential hazard to the occupational health of personnel. At the same time, fluorinated liquid will cause the greenhouse effect and damage the environment. Seeking a more high-quality, low-cost, healthy and environmentally friendly liquid coolant to replace fluorinated liquid mainly based on perfluoropolyether has become an urgent need in the industry.

[0007] Fluorine-free liquid coolants have already appeared in the prior art. Fluorine-free liquid coolants do not have physiological toxicity and do not damage the ozone layer, and are powerful alternatives to fluorinated liquids. For example, CN116438502A discloses that the cooling fluid is an alkyl-modified organosilicon oil with the following average chemical structure:

[0008] (CH 3 ) 3 SiO-[(CH 3 ) 2 )SiO] m -[R(CH 3 )SiO] n -Si(CH 3 ) 3 ,

[0009] However, there are problems such as too large molecular weight and too high viscosity. It is necessary to reduce the viscosity by adding components such as solvents to ensure that the viscosity is < 50 cSt under the conditions of the lowest use temperature. The introduction of components such as solvents inevitably brings impurity effects on the life and stability of the product during use. Summary of the Invention

[0010] In view of this, the purpose of the present invention is to provide a fluorine-free liquid coolant and its preparation method and application. The fluorine-free liquid coolant provided by the present invention has low viscosity, good fluidity, and a small dielectric constant.

[0011] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0012] The present invention provides a fluorine-free liquid coolant having a structure shown in Formula I:

[0013] X(CH 3 ) 2 SiO[R(CH 3 )SiO] m Si(CH 3 ) 2 X Formula I,

[0014] wherein, m Rs include one or more of alkyl groups having 7, 8, 9, and 10 carbon atoms, X is an alkyl group having 7 to 10 carbon atoms or a methyl group, and m is a positive integer from 6 to 35.

[0015] Preferably, the m is a positive integer from 8 to 15.

[0016] Preferably, the m Rs include two or three of alkyl groups having 7, 8, 9, and 10 carbon atoms.

[0017] Preferably, the R is an alkyl group having 7 and 10 carbon atoms, an alkyl group having 7 and 9 carbon atoms, an alkyl group having 7 and 8 carbon atoms, an alkyl group having 8 and 9 carbon atoms, or an alkyl group having 7, 8, and 9 carbon atoms.

[0018] Preferably, the R is a straight-chain alkyl group.

[0019] Preferably, the 40°C viscosity of the fluorine-free coolant is 15 to 50 cSt, the volume resistivity is 10^12 to 10^16 Ω·cm, the flash point of the open cup is 170 to 330°C, and the dielectric constant is 2.1 to 2.4.

[0020] The present invention also provides a preparation method of the fluorine-free coolant described in the above technical solution, including the following steps:

[0021] Under a protective atmosphere, tetramethylcyclotetrasiloxane, unsaturated olefin and a platinum catalyst are mixed for an addition reaction to obtain a crude product of long-chain alkyl polysiloxane ring; the number of carbon atoms of the unsaturated olefin is 7 to 10;

[0022] The crude product of long-chain alkyl polysiloxane ring is refined to obtain a refined product of long-chain alkyl polysiloxane ring;

[0023] The refined product of long-chain alkyl polysiloxane ring is mixed with a capping agent for a ring-opening equilibration reaction to obtain the fluorine-free coolant; the capping agent includes a chain alkyl capping agent or a methyl capping agent, and the number of carbon atoms of the chain alkyl capping agent is 7 to 10.

[0024] Preferably, the amount of the platinum catalyst is calculated by platinum content, and the content of the platinum catalyst in the system obtained by mixing tetramethylcyclotetrasiloxane, unsaturated olefin and the platinum catalyst is 3 to 80 ppm.

[0025] Preferably, the refining is distillation, and the temperature of the distillation is 250 to 350°C, and the pressure is 5 to 80 kPa.

[0026] The present invention also provides an application of the fluorine-free coolant described in the above technical solution as a cooling liquid for a data center liquid cooling system, a new energy vehicle power battery system, a new energy vehicle charging pile system and a wind power generation system.

[0027] The present invention provides a fluorine-free coolant. The fluorine-free coolant provided by the present invention is a long-chain alkyl-modified polyorganosiloxane, and its molecular structure is a polysiloxane formed by the combination of a long-chain alkyl with a specified carbon atom number range and a siloxane group, that is, each repeating structural unit of the entire molecular structure is capped with an alkyl containing a specified carbon chain length or a trimethylsiloxy group, and each repeating structural unit of the entire molecular structure contains an alkyl with a specified carbon chain length.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The molecular chain of the fluorine-free coolant provided by the present invention does not contain dimethylsiloxane segments, and the molecular structure has definiteness and specificity. By limiting the number of carbon atoms in R, it avoids excessive carbon atoms, large molecular weight, high viscosity, poor processability, and is not conducive to the separation of components. Moreover, the excessive viscosity will lead to poor fluidity and is not conducive to being used as a liquid cooling medium. The fluorine-free coolant provided by the present invention is superior to the cooling fluid in CN116438502A in terms of specific indicators such as viscosity, heat resistance, flame retardancy, thermal conductivity, electrical properties, boiling point, flash point, and dielectric constant, and can meet the urgent needs of the industry.

[0030] The present invention also provides a preparation method of the fluorine-free coolant described in the above technical solution. Through refining, it can provide better and more sufficient guarantees for the quality and performance of the fluorine-free coolant.

[0031] The present invention also provides an application of the fluorine-free coolant described in the above technical solution as a cooling liquid for a liquid cooling system in a data center. It does not involve other components such as hydrocarbons and antioxidants, nor does it involve compounding processes and formulations, and the fluorine-free coolant can be directly used as a cooling liquid for a liquid cooling system in a data center. Description of the Drawings

[0032] Figure 1 It is the nuclear magnetic resonance hydrogen spectrum of the fluorine-free coolant prepared in Example 2. Detailed Description of the Invention

[0033] The present invention provides a fluorine-free coolant having the structure shown in Formula I:

[0034] X(CH 3 ) 2 SiO[R(CH 3 )SiO] m Si(CH 3 ) 2 X Formula I,

[0035] wherein, m Rs include one or more of alkyl groups with 7, 8, 9, and 10 carbon atoms, X is an alkyl group with 7 to 10 carbon atoms or a methyl group, and m is a positive integer from 6 to 35.

[0036] In the present invention, m is preferably a positive integer from 8 to 15.

[0037] In the present invention, the m Rs preferably include alkyl groups with 7 and 10 carbon atoms, alkyl groups with 7 and 9 carbon atoms, alkyl groups with 7 and 8, alkyl groups with 8 and 9, or alkyl groups with 7, 8, and 9 carbon atoms; when the number of carbon atoms in R is less than 6, the product's electrical properties, flash point, and other indicators are poor and do not meet the standards; when the number of carbon atoms in R is more than 10, it will lead to a sharp increase in viscosity and poor processability.

[0038] In the present invention, the number of carbon atoms in X is preferably the same as that in R.

[0039] In the present invention, R is preferably a straight-chain alkyl group.

[0040] In the present invention, the rotational viscosity of the non-fluorinated liquid coolant at 40 °C is preferably 15 to 50 cSt, the volume resistivity is preferably 10^12 to 10^16 Ω·cm, the flash point of the open cup is preferably 170 to 330 °C, and the dielectric constant is preferably 2.1 to 2.4.

[0041] The present invention also provides a preparation method of the non-fluorinated liquid coolant described in the above technical solution, including the following steps:

[0042] Under a protective atmosphere, tetramethylcyclotetrasiloxane, unsaturated olefin and a platinum catalyst are mixed for an addition reaction to obtain a crude product of long-chain alkyl polysiloxane cyclic oligomer; the number of carbon atoms in the unsaturated olefin is 7 to 10;

[0043] The crude product of long-chain alkyl polysiloxane cyclic oligomer is refined to obtain a refined product of long-chain alkyl polysiloxane cyclic oligomer;

[0044] The refined product of long-chain alkyl polysiloxane cyclic oligomer is mixed with a capping agent for a ring-opening equilibration reaction to obtain the non-fluorinated liquid coolant; the capping agent includes a chain alkyl capping agent or a methyl capping agent, and the number of carbon atoms in the chain alkyl capping agent is 7 to 10.

[0045] In the present invention, unless otherwise specified, the raw materials used are commercially available products in the art.

[0046] In the present invention, under a protective atmosphere, tetramethylcyclotetrasiloxane, unsaturated olefin and a platinum catalyst are mixed for an addition reaction to obtain a crude product of long-chain alkyl polysiloxane cyclic oligomer; the number of carbon atoms in the unsaturated olefin is 7 to 10.

[0047] In the present invention, the protective atmosphere is preferably nitrogen.

[0048] In the present invention, the molar ratio of tetramethylcyclotetrasiloxane to unsaturated olefin is preferably 1:3.5 to 4.5, more preferably 1:4.

[0049] In the present invention, the unsaturated olefin preferably includes one or more of 1-heptene, 1-octene, 1-nonene and 1-decene.

[0050] In the present invention, the platinum catalyst is preferably a complex of hexachloroplatinic acid (H 2 PtCl 6 ) and isopropanol (Wilking platinum catalyst), and the mass ratio of hexachloroplatinic acid to isopropanol in the complex is preferably 1:100 to 500.

[0051] In the present invention, the platinum catalyst is preferably a complex of hexachloroplatinic acid (H 2 PtCl 6 ) and divinyltetramethyldisiloxane (Karstedt platinum catalyst). The molar ratio of hexachloroplatinic acid to divinyltetramethyldisiloxane in the complex is preferably 1:1 to 5.

[0052] In the present invention, based on the platinum content, the content of the platinum catalyst in the system obtained by mixing the tetramethylcyclotetrasiloxane, unsaturated olefin and platinum catalyst is preferably 3 to 80 ppm, more preferably 10 to 30 ppm, further preferably 15 to 20 ppm, and most preferably 16 to 18 ppm.

[0053] In the present invention, preferably in a three-necked flask, the unsaturated olefin is added, protected by nitrogen, then the platinum catalyst is added, and the temperature is raised with stirring to the temperature of the addition reaction. The tetramethylcyclotetrasiloxane is gradually added dropwise. The dropping time is preferably 1 to 5 h. After the dropping is completed, stirring is continued for 3 to 4 h.

[0054] In the present invention, the temperature of the addition reaction is preferably 70 to 125 °C, more preferably 80 to 85 °C.

[0055] After obtaining the crude product of the long-chain alkyl polysiloxane cyclic body, the present invention refines the crude product of the long-chain alkyl polysiloxane cyclic body to obtain a refined product of the long-chain alkyl polysiloxane cyclic body ([R(CH 3 )SiO] 4 ).

[0056] In the present invention, the refining is preferably distillation. The distillation temperature is preferably 250 to 350 °C, more preferably 280 to 330 °C, and most preferably 300 to 320 °C. The pressure is preferably 5 to 80 kPa, more preferably 30 to 50 kPa.

[0057] In the present invention, the end point of the refining is preferably that no substance is distilled out.

[0058] In the present invention, the refining is preferably carried out in a rotary evaporator.

[0059] After obtaining the refined product of the long-chain alkyl polysiloxane cyclic body, the present invention mixes the refined product of the long-chain alkyl polysiloxane cyclic body with a capping agent to carry out a ring-opening equilibration reaction to obtain the non-fluorinated refrigerant. The capping agent includes a chain alkyl capping agent or a methyl capping agent. The carbon atom number of the chain alkyl capping agent is 7 to 10.

[0060] In the present invention, the chain alkyl capping agent is preferably tetraoctyltetramethyldisiloxane, tetranonyltetramethyldisiloxane, tetraheptyltetramethyldisiloxane or tetradecyltetramethyldisiloxane; the methyl capping agent is preferably hexamethyldisiloxane.

[0061] In the present invention, the molar ratio of the refined long-chain alkyl polysiloxane cyclic body to the end-capping agent is preferably 1:0.1 to 1.

[0062] In the present invention, the ring-opening equilibration reaction is preferably carried out under acidic or basic conditions. The acid is preferably provided by sulfuric acid, sulfonic acid resin or trifluoromethanesulfonic acid, and the base is preferably provided by KOH or alkaline glue.

[0063] In the present invention, the temperature of the ring-opening equilibration reaction is preferably 40 to 130 °C, more preferably 50 to 120 °C, most preferably 90 °C, and the time is preferably 2 to 6 h.

[0064] After the ring-opening equilibration reaction is completed, the present invention preferably neutralizes the obtained ring-opening equilibration product to neutral and removes low-boiling raw materials in sequence to obtain the fluorine-free liquid coolant.

[0065] In the present invention, the temperature for removing low-boiling raw materials is preferably 150 to 200 °C.

[0066] The present invention also provides the application of the fluorine-free liquid coolant described in the above technical solution as a cooling liquid for a data center liquid cooling system, a new energy vehicle power battery system, a new energy vehicle charging pile system and a wind power generation system.

[0067] In the present invention, the application preferably uses the fluorine-free liquid coolant directly as a cooling liquid, without involving other components such as hydrocarbons and antioxidants.

[0068] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0069] The raw materials used in the embodiments of the present invention are shown in Table 1.

[0070] Table 1 Raw materials used in the embodiments

[0071]

[0072]

[0073] Example 1

[0074] Add 520 g of 1-heptene into a three-necked flask, protect it by passing nitrogen, add 10 ppm of Karstedt's platinum catalyst (calculated by platinum content), stir and heat up to 80 °C, gradually dropwise add 285 g of tetramethylcyclotetrasiloxane, and the dropping time is 1 h. After the dropping is completed, continue to stir for 3 h. Keep the temperature and remove the unreacted 1-heptene under negative pressure to obtain the crude product of tetraheptyltetramethylcyclotetrasiloxane. Heat the crude product of tetraheptyltetramethylcyclotetrasiloxane to 280 °C and reduce the pressure to below 50 kPa, and distill to obtain the refined product of tetraheptyltetramethylcyclotetrasiloxane without platinum residue. Add 192 g of hexamethyldisiloxane and 70 g of concentrated sulfuric acid to the obtained refined product of tetraheptyltetramethylcyclotetrasiloxane, catalyze and equilibrate at 50 °C for 6 h, neutralize with sodium bicarbonate and filter, heat up to remove the low-boiling components, and the obtained product is the target product of methyl-terminated 7C long-chain alkyl (heptyl) polysiloxane, 897.3 g, with a purity of 99.5% and a yield of 90%. After testing, the product viscosity is 35.6 cSt (40 °C), the volume resistivity is 1.9×10^14 Ω·cm, the open-cup flash point is 252 °C, the dielectric constant is 2.4, and the boiling point is 316 °C.

[0075] Example 2

[0076] Add 580 g of 1-octene into a three-necked flask, protect it by passing nitrogen, add 30 ppm of Karstedt's platinum catalyst (calculated by platinum content), stir and heat up to 85 °C, gradually dropwise add 302 g of tetramethylcyclotetrasiloxane, and the dropping time is 1 h. After the dropping is completed, continue to stir for 3 h. Keep the temperature and remove the unreacted 1-octene under negative pressure to obtain the crude product of tetraoctyltetramethylcyclotetrasiloxane. Heat the crude product of tetraoctyltetramethylcyclotetrasiloxane to 300 °C and reduce the pressure to below 50 kPa, and distill to obtain the refined product of tetraoctyltetramethylcyclotetrasiloxane without platinum residue. Add 120 g of hexamethyldisiloxane and 80 g of sulfonic acid resin to the obtained refined product of tetraoctyltetramethylcyclotetrasiloxane, catalyze and equilibrate at 50 °C for 6 h, filter, heat up to remove the low-boiling components, and the obtained product is the target product of methyl-terminated 8C long-chain alkyl (octyl) polysiloxane, 921.8 g, with a purity of 99.68% and a yield of 92%. After testing, the product viscosity is 30.3 cSt (40 °C), the volume resistivity is 1.2×10^15 Ω·cm, the dielectric constant is 2.2, the boiling point is 342 °C, and the open-cup flash point is 268 °C.

[0077] Figure 1 1H NMR spectrum of the non-fluorinated liquid coolant prepared in Example 2.

[0078] Comparative Example

[0079] Refer to the preparation method in CN116438502A to prepare the compound with the structural formula (CH 3 ) 3 SiO[(CH 3 ) 2 SiO] 3 [(C8 H 17 )(CH 3 )SiO] 6 Si(CH 3 ) 3 The silicone oil and... After testing, the viscosity of the silicone oil in the comparative example is 38.1 cSt (40 °C), the volume resistivity is 0.63×10^12 Ω·cm, the dielectric constant is 2.5, the boiling point is 301 °C, and the flash point of the open cup is 167 °C. It can be seen that the flame retardancy performance is lower than that of the present invention, and the volume resistivity does not meet the standard requirement of >10^12 Ω·cm specified in YD / T 3982-2021 "Technical Requirements and Test Methods for Cooling Liquids in Data Center Liquid Cooling Systems".

[0080] Example 3

[0081] Add 605 g of 1-nonene to a three-necked flask, protect it with nitrogen, add 15 ppm of Karstedt platinum catalyst (calculated by platinum content), stir and heat up to 85 °C, gradually add 270 g of tetramethylcyclotetrasiloxane dropwise, and the dropping time is 1 h. After the dropping is completed, continue to stir for 3 h. Keep the temperature and remove the unreacted 1-nonene under negative pressure to obtain the crude product of tetranonyltetramethylcyclotetrasiloxane. Heat the crude product of tetranonyltetramethylcyclotetrasiloxane to 330 °C and reduce the pressure below 50 kPa, and distill to obtain the refined product of tetranonyltetramethylcyclotetrasiloxane without platinum residue. Add 140 g of hexamethyldisiloxane and 0.1 g of trifluoromethanesulfonic acid to the obtained refined product of tetranonyltetramethylcyclotetrasiloxane, and carry out catalytic equilibration at 50 °C for 6 h, filter, and heat up to remove the low-boiling components. The obtained product is the target product of methyl-terminated 9C long-chain alkyl (nonyl) polysiloxane, 903.3 g, with a purity of 99.5% and a yield of 89%. After testing, the viscosity of the product is 48.1 cSt (40 °C), the volume resistance is 0.95×10^14 Ω·cm, the flash point of the open cup is 312 °C, the dielectric constant is 2.26, and the boiling point is 360 °C.

[0082] Example 4

[0083] Add 360 g of 1-heptene and 240 g of 1-decene into a three-necked flask, protect with nitrogen, add 10 ppm of Karstedt's platinum catalyst (calculated by platinum content), stir and heat up to 85 °C, gradually add 302 g of tetramethylcyclotetrasiloxane dropwise, and the dropping time is 2 h. After the dropping is completed, continue to stir for 4 h. Keep the temperature and remove the unreacted 1-heptene and 1-decene under negative pressure to obtain the crude product of long-chain alkyl polysiloxane. Heat the crude product of long-chain alkyl polysiloxane to 330 °C and reduce the pressure below 50 kPa, and distill to obtain the refined product of long-chain alkyl polysiloxane without platinum residue. Add 145 g of hexamethyldisiloxane and 100 g of concentrated sulfuric acid to the obtained refined product of long-chain alkyl polysiloxane, catalyze and equilibrate at 40 °C for 6 h, filter, heat up to remove the low-boiling components at 255, and the obtained product is the target product of 942.3 g of methyl-terminated polysiloxane containing two long-chain alkyl combinations of 7C long-chain alkyl (heptyl) and 10C long-chain alkyl (decyl), with a purity of 99.5% and a yield of 90%. The viscosity of the product is detected to be 33.4 cSt (40 °C), the volume resistivity is 0.52×10^14 Ω·cm, the open-cup flash point is 295 °C, the dielectric constant is 2.3, and the boiling point is not measured (≥360 °C).

[0084] Example 5

[0085] Add 560 g of 1-octene into a three-necked flask, protect with nitrogen, add 18 ppm of Karstedt's platinum catalyst (calculated by platinum content), stir and heat up to 85 °C, gradually add 295 g of tetramethylcyclotetrasiloxane dropwise, and the dropping time is 1 h. After the dropping is completed, continue to stir for 3 h. Keep the temperature and remove the unreacted 1-octene under negative pressure to obtain the crude product of tetraoctyltetramethylcyclotetrasiloxane. Heat the crude product of tetraoctyltetramethylcyclotetrasiloxane to 300 °C and reduce the pressure below 50 kPa, and distill to obtain the refined product of tetraoctyltetramethylcyclotetrasiloxane without platinum residue. Add 205 g of octyltetramethyldisiloxane and 2 g of alkali gel to the obtained refined product of tetraoctyltetramethylcyclotetrasiloxane, catalyze and equilibrate at 90 °C for 2 h, filter, heat up to remove the low-boiling components, and the obtained product is the target product of 946.6 g of octyl-terminated 8C long-chain alkyl (octyl) polysiloxane, with a purity of 99.5% and a yield of 91%. The viscosity of the product is detected to be 28.9 cSt (40 °C), the volume resistivity is 1.96×10^14 Ω·cm, the open-cup flash point is 289 °C, the dielectric constant is 2.4, and the boiling point is 351 °C.

[0086] Example 6

[0087] Add 482 g of 1-heptene, 315 g of 1-octene, and 240 g of 1-nonene into a three-necked flask. Protect with nitrogen, add 20 ppm of Karstedt's platinum catalyst (calculated by platinum content), stir and heat up to 80 °C, gradually add dropwise 445 g of tetramethylcyclotetrasiloxane. During the dropping process, when the material temperature rises to 105 °C, continue dropping. The dropping is completed in 1 h. After the dropping is completed, continue stirring for 3 h. Keep warm and remove unreacted 1-heptene, 1-decene, and 1-nonene under negative pressure to obtain the crude long-chain alkyl polysiloxane. Heat the crude long-chain alkyl polysiloxane to 320 °C and reduce the pressure to below 50 kPa to distill and obtain the refined long-chain alkyl polysiloxane without platinum residue. Add 195 g of hexamethyldisiloxane to the obtained refined long-chain alkyl polysiloxane, stir evenly, dehydrate under reduced pressure at 90 °C for 1 h, add 1 g of pre-prepared KOH octamethylcyclotetrasiloxane solution, heat up to 110 °C and catalyze for equilibrium for 3 h, and introduce CO 2 Bubble and stir for 1.5 h, heat up to remove low-boiling components. The obtained product is the target product of 1108.8 g with methyl end-capped and a combination of three long-chain alkyls of 7C (heptyl), 8C (octyl), and 9C (nonyl), with a purity of 99.6% and a yield of 90%. After testing, the product viscosity is 32.1 cSt (40 °C), the volume resistivity is 1.31×10^14 Ω·cm, the open cup flash point is 223 °C, the dielectric constant is 2.3, and the boiling point is 358 °C.

[0088] Example 7

[0089] Add 620 g of 1-heptene and 430 g of 1-nonene into a three-necked flask. Protect with nitrogen, add an isopropanol solution of 16 ppm of chloroplatinic acid (calculated by platinum content), stir and heat up to 85 °C, gradually add dropwise 400 g of tetramethylcyclotetrasiloxane. The dropping is completed in 2 h. After the dropping is completed, continue stirring for 4 h. Keep warm and remove unreacted 1-heptene and 1-nonene under negative pressure to obtain the crude long-chain alkyl polysiloxane. Heat the crude long-chain alkyl polysiloxane to 330 °C and reduce the pressure to below 50 kPa to distill and obtain the refined long-chain alkyl polysiloxane without platinum residue. Add 275 g of pre-prepared diheptyltetramethyldisiloxane and 50 ppm of potassium hydroxide to the obtained refined long-chain alkyl polysiloxane, catalyze for equilibrium at 130 °C for 2 h, neutralize with 0.5 mol of phosphoric acid, heat up to remove low-boiling components. The obtained product is the target product of 1587 g with heptyl end-capped and a combination of two long-chain alkyls of 7C (heptyl) and 9C (nonyl), with a purity of 99.5% and a yield of 92%. After testing, the product viscosity is 40.4 cSt (40 °C), the volume resistivity is 0.92×10^15 Ω·cm, the open cup flash point is 326 °C, the dielectric constant is 2.3, and the boiling point is 346 °C.

[0090] Table 2 shows the performance test comparison between the fluorine-free coolant of the present invention and the perfluoropolyether coolant PFC (perfluoropolyether is a product of organic fluorides and is the mainstream fluorine-containing coolant on the market at present, with certain toxicity and environmental destructiveness). The present invention is a straight-chain alkyl-modified polysiloxane with a specific number of carbon atoms in the whole chain segment, and its molecular structure has clarity and specificity, avoiding the problems of excessive numbers of carbon atoms in the chain alkyl and siloxane chain segments, too large molecular weight, too high viscosity, and the need to add solvent and other components to reduce viscosity and improve fluidity when used as a liquid cooling medium; and on the basis of low viscosity (<50 cSt / 40 °C), the physical property indexes such as boiling point, flash point, dielectric constant, volume resistivity, thermal conductivity, specific heat capacity, health and environmental protection are all superior to those of mainstream fluorinated liquid immersion coolants such as perfluoropolyether. It fully meets and is superior to the specification standards of YD / T 3982-2021 "Technical Requirements and Test Methods for Cooling Liquids in Data Center Liquid Cooling Systems", can meet the higher requirements of the industry, and is an upgraded alternative product to fluorinated liquid immersion coolants.

[0091] Table 2 Performance test comparison between the fluorine-free coolant of the present invention and the perfluoropolyether coolant PFC

[0092]

[0093] The above are only the preferred embodiments of the present invention and do not impose any form of limitation on the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A fluorine-free liquid coolant having a structure shown in Formula I: X(CH3)2SiO[R(CH3)SiO] m Si(CH3)2X of formula I in, The m Rs are one or more of an alkyl group having 7, 8, 9 and 10 carbon atoms, X is an alkyl group having 7 to 10 carbon atoms or a methyl group, and m is a positive integer of 6 to 35.

2. The fluorine-free liquid coolant according to claim 1, characterized in that: The m is a positive integer ranging from 8 to 15.

3. The fluorine-free liquid coolant according to claim 1 or 2, characterized in that: The m Rs are two or three of the alkyl groups having 7, 8, 9 and 10 carbon atoms.

4. The fluorine-free liquid coolant according to claim 3, characterized in that: The R is an alkyl group having 7 and 10 carbon atoms, an alkyl group having 7 and 9 carbon atoms, an alkyl group having 7 and 8 carbon atoms, an alkyl group having 8 and 9 carbon atoms, or an alkyl group having 7, 8 and 9 carbon atoms.

5. The fluorine-free liquid coolant according to claim 1 or 4, characterized in that: The alkyl group in the R is a straight-chain alkyl group.

6. The fluorine-free liquid coolant according to claim 1, characterized in that: The fluorine-free liquid coolant has a viscosity of 15 to 50 cSt at 40°C and a volume resistivity of 10 12 ~10 16 Ω·cm, open cup flash point is 170~330℃, and dielectric constant is 2.1~2.

4.

7. The method for preparing the fluorine-free liquid coolant according to any one of claims 1 to 6, characterized in that: The following steps are involved: Under a protective atmosphere, tetramethylcyclotetrasiloxane, an unsaturated olefin and a platinum catalyst are mixed for addition reaction to obtain a crude long-chain alkyl polysiloxane ring body; the unsaturated olefin has 7 to 10 carbon atoms; Refining the crude long-chain alkyl polysiloxane ring body to obtain a refined long-chain alkyl polysiloxane ring body; The refined long-chain alkyl polysiloxane ring body product is mixed with a capping agent to carry out a ring-opening equilibrium reaction to obtain the fluorine-free liquid coolant; the capping agent includes a chain alkyl capping agent or a methyl capping agent, and the chain alkyl capping agent has 7 to 10 carbon atoms.

8. The preparation method according to claim 7, characterized in that: The amount of the platinum catalyst is calculated based on the platinum content. The content of the platinum catalyst in the system obtained by mixing the tetramethylcyclotetrasiloxane, the unsaturated olefin and the platinum catalyst is 3 to 80 ppm.

9. The preparation method according to claim 7 or 8, characterized in that: The refining is distillation, the distillation temperature is 250-350° C., and the pressure is 5-80 kPa.

10. Use of the fluorine-free liquid coolant according to any one of claims 1 to 6 as cooling liquid for a data center liquid cooling system, a new energy vehicle power battery system, a new energy vehicle charging pile system, and a wind power generation system.

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