PAO4 ultra-pure immersion cooling liquid and preparation method thereof, and liquid cooling case

Abstract

The application discloses a PAO4 ultra-pure immersion cooling liquid and a preparation method and a liquid cooling case thereof, the PAO4 ultra-pure immersion cooling liquid contains the following components in percentage by weight: 99.82-99.88% of ultra-pure poly-alpha-olefin synthetic base oil PAO4, 0.1-0.15% of an antioxidant, 0.019-0.03% of a passivator, and 0.001% of a defoaming agent, and the sum of the percentage by weight of the components is 100%; the preparation method comprises the following steps: adding the ultra-pure poly-alpha-olefin synthetic base oil PAO4 into a reaction kettle and heating to 55-65 DEG C; adding the antioxidant into the reaction kettle and stirring until completely dissolved; after cooling to 55 DEG C, adding the passivator into the reaction kettle and stirring; after cooling to 50 DEG C, adding the defoaming agent into the reaction kettle and stirring, filtering, and obtaining the PAO4 ultra-pure immersion cooling liquid, the kinematic viscosity of which at 40 DEG C is 18-21 cSt, and the viscosity index is 120-130.

Description

Technical Field

[0001] This invention relates to the field of immersion coolants, specifically to a PAO4 ultrapure immersion coolant and its preparation method, and a liquid-cooled chassis. Background Technology

[0002] With the continuous improvement of CPU and GPU computing power, the power consumption of mid-to-high-end complete machines generally reaches 600W-1200W. Traditional air cooling is noisy and accumulates a lot of dust, fluorinated liquid is too expensive to be mass-produced, and mineral oil is prone to oxidation and corrosion of components at high temperatures. Existing polyalphaolefin coolants are divided into three types: PAO2, PAO4, and PAO6, each with obvious shortcomings.

[0003] 1. PAO2 low viscosity coolant: The viscosity at 40℃ is only 5-6 cSt, with a small heat capacity. It is only suitable for low power consumption equipment within 300W and cannot withstand the continuous heat generation of medium and high power hardware. It lacks dispersing agents and high temperature oxidation impurities are easy to accumulate and block the circulation pipeline.

[0004] 2. Commercially available PAO4 coolant: The formula is simple, and long-term immersion in FKM fluororubber seals will cause swelling and softening, resulting in leakage and short circuit risks; the single antioxidant has poor high and low temperature stability, and the acid value rises rapidly with long-term operation;

[0005] 3. PAO6 high viscosity products have a viscosity of 31-34.5 cSt, resulting in high fluid circulation resistance. Using them in 600-1200W equipment will increase the power consumption of the pump body, and the heat dissipation cost-effectiveness is relatively low.

[0006] 4. Conventional coolants mostly use silicon-based defoamers. With long-term use, silicon elements will precipitate and adhere to the PCB circuit board, causing insulation attenuation and signal abnormalities. Metal passivators only use ordinary TTA, which is prone to precipitation in low-temperature environments, causing copper foil protection to fail.

[0007] Existing PAO4 immersion coolant cannot simultaneously achieve multiple properties such as high heat capacity, long-lasting oxidation resistance, dual corrosion protection for metals, anti-foaming and scale dispersion, rubber seal compatibility, silicone-free and low foaming, and ultra-high insulation. Summary of the Invention

[0008] The technical problems to be solved by this invention are: insufficient purity of existing ordinary PAO4 base oil, with trace impurities reducing insulation strength; high total amount of additives in conventional coolants reducing the heat capacity of the oil; low-temperature precipitation of traditional TTA metal passivators, failing to provide stable protection for PCB copper foil throughout the year; insufficient long-term stability of single aromatic amine antioxidants; silicone defoamers contaminating circuits; and complex components in conventional formulations leading to poor compatibility of additives and easy stratification during long-term operation. This invention provides an ultrapure PAO4 immersion coolant, a method for preparing the ultrapure PAO4 immersion coolant, and a liquid-cooled chassis, using only low-dosage, high-efficiency antioxidants, copper passivators, and non-silicone defoamers. The total amount of additives is extremely low, achieving the advantages of high heat capacity, ultra-high insulation, long-term antioxidant effect, low-temperature copper protection, and low foaming without silicone, thus overcoming the defects caused by existing technologies.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solutions:

[0010] In a first aspect, a PAO4 ultrapure immersion coolant, comprising the following components by weight percentage:

[0011] It contains 99.82-99.88% ultrapure polyalphaolefin synthetic base oil PAO4, 0.1-0.15% antioxidant, 0.019-0.03% passivator, and 0.001% defoamer, with the sum of the weight percentages of each component being 100%.

[0012] PAO4 is an API IV group fully synthetic hydrocarbon base oil, produced by catalytic oligomerization of high-purity linear 1-decene monomers, high-pressure deep hydrogenation saturation, and precision fractionation. Its chemical name is hydrogenated 1-decene oligomer, CAS: 68037-01-4. The designation "4" indicates a kinematic viscosity of approximately 4 cSt at 100℃, corresponding to a kinematic viscosity of 18-21 cSt at 40℃, with a viscosity index of 120-130. It is a general-purpose low-to-medium viscosity PAO grade for immersion cooling and high-end lubrication. The molecules are primarily composed of C30 / C40 / C50 saturated branched alkanes, free of double bonds, aromatics, and cycloalkanes, exhibiting chemical inertness far superior to mineral oils. It contains ≥99.5% saturated hydrocarbons, with extremely low levels of sulfur, nitrogen, and halogen impurities. It has sufficient heat capacity, moderate circulation resistance, and is suitable for 600-1200W medium-to-high power hardware.

[0013] The aforementioned PAO4 ultrapure immersion coolant comprises an aromatic amine antioxidant, which can capture high-temperature free radicals and is long-lasting and non-volatile; a metal passivator, which forms a surface passivation film to prevent catalytic oxidation of metals, mainly copper, which can effectively protect PCB copper foil and copper pipes; and a non-silicone defoamer, which effectively inhibits circulating foaming and prevents air from reducing dielectric strength.

[0014] The aforementioned PAO4 ultrapure immersion coolant comprises, wherein the aromatic amine antioxidant is dioctyl diphenylamine (DODPA), which captures free radicals at high temperatures for a long time, has low volatility, and can inhibit oil oxidation and acidification with extremely low addition amounts; the metal passivator is alkylated benzotriazole, which does not precipitate at low temperatures compared to ordinary TTA, and forms a dense passivation film on the surface of copper foil and copper pipes throughout the year, blocking the catalytic oxidation of metals; and the non-silicone defoamer is polyacrylate, which does not cause silicon precipitation pollution, inhibits the generation of bubbles in the circulating fluid, and avoids bubbles from reducing dielectric strength.

[0015] The aforementioned PAO4 ultrapure immersion coolant contains an ultrapure polyalphaolefin synthetic base oil (PAO4) with a kinematic viscosity of 18-21 cSt at 40°C and a viscosity index of 120-130, with a viscosity between PAO2 and PAO6, balancing heat dissipation capacity and circulation resistance. Its ultra-high purity base contains very few impurities, naturally possessing high volume resistivity and high breakdown voltage. Its high viscosity index ensures stable fluid flow under high and low temperature conditions in both winter and summer, preventing issues of low-temperature viscosity and high-temperature thinning.

[0016] A PAO4 ultrapure immersion coolant prepared according to the above weight percentages has a density of 819-822 kg / m³ at 20°C. 3 Flash point (closed cup) greater than 218℃, ensuring high safety during use, with no fire hazard even under high temperature and full load; pour point less than -55℃, preventing solidification upon startup in low-temperature environments, exhibiting excellent fluidity, and maintaining good fluidity even in low-temperature environments in northern regions; acid value less than 0.02mgKOH / g, resisting acidification and corrosion over long-term use; moisture content less than 10ppm, effectively preventing insulation degradation caused by moisture; dielectric strength greater than 48kV / 2.5mm, volume resistivity greater than 1×10⁻⁶. 13 Ω·cm, insulation installation meets the immersion requirements of electronic components, dielectric constant (1kHz) is 2.08-2.15, foam is less than 10 / 0mL, and there are no large number of bubbles during circulation.

[0017] Secondly, a method for preparing a PAO4 ultrapure immersion coolant, comprising the following steps:

[0018] By weight percentage, 99.82-99.88% of ultrapure polyalphaolefin synthetic base oil PAO4 is added to the reactor, and the reactor is heated to 55℃-65℃ by water bath heating.

[0019] Add 0.1-0.15% of the antioxidant to the reaction vessel and stir at 400 rpm for 40 minutes until completely dissolved;

[0020] After cooling to 55℃, add 0.019-0.03% passivating agent to the reactor and stir for 20 minutes;

[0021] After cooling to 50℃, 0.001% of defoamer was added to the reactor and stirred for 10 minutes. The mixture was then filtered through a 5μm filter membrane to obtain PAO4 ultrapure immersion coolant. The defoamer needs to be diluted 100 times with PAO4 first.

[0022] The PAO4 ultrapure immersion coolant is prepared by a completely closed stirring process, which prevents moisture and oxygen from the air from mixing into the interior.

[0023] Thirdly, a liquid-cooled chassis, wherein the interior of the liquid-cooled chassis is filled with a PAO4 ultrapure immersion coolant as described in the first aspect, and the CPU, GPU, and motherboard components inside the liquid-cooled chassis are completely immersed in the PAO4 ultrapure immersion coolant; the chassis is a fully enclosed immersion cavity with a built-in circulating pump and an external water-cooled heat exchanger, and the cavity seals are made of FKM fluororubber / PTFE material. The CPU, discrete graphics card, motherboard, and memory are all completely immersed in this PAO4 coolant, which is suitable for 600-1200W high-performance equipment to operate continuously for 24 hours.

[0024] The above-mentioned technical solution of the PAO4 ultrapure immersion coolant and its preparation method, as well as the liquid cooling chassis provided by the present invention, has the following technical effects:

[0025] The ultra-pure polyalphaolefin (PAO4) synthetic base oil contains over 99.82% PAO4, with extremely low total additive content, maximizing the oil's heat capacity and preventing localized high temperatures under full load at 600-1200W. PAO4 has extremely low base impurities, naturally exhibiting ultra-high insulation, and excellent breakdown voltage and volume resistivity. Low-addition DODPA provides long-lasting antioxidant protection, with slow acid value increase during long-term high-temperature operation, extending the oil replacement cycle. Alkylated benzotriazole replaces ordinary TTA, preventing precipitation at low temperatures and providing stable protection against catalytic oxidation of PCB copper foil throughout the year. Only 0.001% trace amounts of non-silicone defoaming ensure no continuous bubbles during circulation, eliminating the problem of silicon precipitation contaminating the circuit board. The entire preparation process is carried out under low-temperature nitrogen-sealed conditions, with no high-temperature reactions. Raw materials are readily available commercially, resulting in low production costs suitable for mass production. With a viscosity of 18-21 cSt, it balances heat dissipation and circulation energy consumption, offering lower pump consumption compared to PAO6 and greater heat dissipation margin compared to PAO2. Detailed Implementation

[0026] In order to make the technical means, inventive features, objectives and effects of the invention easy to understand, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0027] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0029] Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0030] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be combined arbitrarily, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when describing a parameter as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 for that parameter. For instance, when describing a parameter as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0031] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0032] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0033] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0034] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if a method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0035] In this application, open-ended technical features or solutions described using terms such as "containing," "including," or "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may also include other members or exclude additional members unless otherwise specified. This can be considered as providing both the feature or solution that "A consists of a1, a2, and a3" and the feature or solution that "A includes not only a1, a2, and a3, but also other members." In this application, unless otherwise specified, A (e.g., B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0036] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0037] Currently, computer cases often overheat during use, and there is no good solution for managing the heat inside the case. Immersion coolant can transfer heat without corroding various materials. This solution uses a PAO4 ultrapure immersion coolant, which is compounded with diarylamine composite antioxidants, passivators, and defoamers, and is suitable for long-term stable immersion cooling of medium and high power hardware of 600-1200W.

[0038] To solve the above-mentioned technical problems, the present invention provides the following technical solutions:

[0039] One embodiment of this application provides a PAO4 ultrapure immersion coolant, wherein it comprises the following components by weight percentage:

[0040] The product contains 99.82-99.88% ultrapure polyalphaolefin synthetic base oil PAO4, 0.1-0.15% antioxidant, 0.019-0.03% passivator, and 0.001% defoamer, with the total weight percentage of each component being 100%. The antioxidant is an aromatic amine antioxidant, which can capture high-temperature free radicals and is long-lasting and non-volatile. The passivator is a metal passivator that forms a surface passivation film to prevent catalytic oxidation of metals, mainly copper, effectively protecting PCB copper foil and copper pipes. The defoamer is a non-silicone defoamer that effectively inhibits circulating foaming and prevents air from reducing dielectric strength.

[0041] The aromatic amine antioxidant is dioctyl diphenylamine (DODPA), which can capture free radicals at high temperatures for a long time, has low volatility, and can inhibit the oxidation and acidification of oils with very low addition amount;

[0042] In specific implementation, the antioxidant can be any one of diphenyldiphenylamine, butyloctyldiphenylamine, phenyl-α-naphthylamine, or hexyldiphenylamine;

[0043] Dinonyldiphenylamine (DNDA) is the preferred alternative. CAS: 68411-47-4; Structure: C9H19 group x2-substituted diphenylamine; Advantages: Larger molecular weight than DODPA, lower volatility, and better retention in PAO4; Long-chain alkyl groups enhance solubility in nonpolar solvents; Slightly better high-temperature oxidation resistance than DODPA.

[0044] Butyloctyldiphenylamine (BODA) is a cost-effective choice. CAS: 68921-74-2; Structure: asymmetric substitution, C4H9+C8H17; Advantages: lower molecular weight, faster dissolution in PAO4, 20% shorter stirring time, 17% lower cost than DODPA, and about 85% of the antioxidant properties of DODPA.

[0045] Phenylacetyl-α-naphthylamine (PANA), an alternative for extreme operating conditions, CAS: 90-30-2; Structure: naphthalene ring + aniline, a biaromatic ring system; Advantages: strongest antioxidant properties, biaromatic ring provides additional free radical scavenging sites, excellent solubility in PAO4, low cost, and excellent performance under high temperature and extreme operating conditions.

[0046] Hexyl diphenylamine (HDA), a lightweight alternative, CAS: 68411-46-3; structure: C6H13 substituted diphenylamine; advantages: low molecular weight, best solubility among PAO4, completely soluble in cold state, and moderate cost.

[0047] The metal passivating agent is alkylated benzotriazole, which does not precipitate at low temperatures compared to ordinary TTA. It forms a dense passivation film on the surface of copper foil and copper tube throughout the year, blocking the catalytic oxidation of metal.

[0048] The defoamer is a non-silicone defoamer, made of polyacrylate, which does not cause silicone precipitation pollution, inhibits the generation of bubbles in the circulating fluid, and prevents air from reducing the dielectric strength.

[0049] In specific implementation, low molecular weight polyisobutylene (PIB) can be used as a defoamer. CAS: 9003-27-4. PIB with a molecular weight of 300-1000 is completely miscible with PAO4 (both are hydrocarbons). The defoaming mechanism is to reduce the interfacial tension between oil and gas. Advantages: It has the best solubility in PAO4 (100% miscible), will not precipitate or separate, has low cost, and does not interact with any other additives.

[0050] The kinematic viscosity of ultrapure polyalphaolefin synthetic base oil PAO4 at 40℃ is 18-21 cSt. PAO4 high viscosity base oil has a large heat capacity and sufficient heat exchange capacity, making it suitable for 600-1200W servers and high-performance mainframes, with no localized high temperature points under full load.

[0051] Specifically, the following are absolutely prohibited: silicon-containing compounds, which will cause silicon deposition and contamination; halogen-containing compounds, which will cause corrosion; zinc / phosphorus extreme voltage agents, which will cause electrical interference and PCB contamination; metal sulfonates, which will cause precipitation; and sulfur-containing compounds, which will cause copper corrosion.

[0052] A PAO4 ultrapure immersion coolant prepared according to the above weight percentages has a density of 818-825 kg / m³ at 20°C. 3 Flash point (closed cup) greater than 208℃, ensuring high safety during use, with no fire hazard even under high temperature and full load; pour point less than -55℃, preventing solidification upon startup in low-temperature environments, exhibiting excellent fluidity, and maintaining good fluidity even in low-temperature environments in northern regions; acid value less than 0.05mgKOH / g, resisting acidification and corrosion over long-term use; moisture content less than 30ppm, effectively preventing insulation degradation caused by moisture; dielectric strength greater than 48kV / 2.5mm, volume resistivity greater than 1×10⁻⁶. 13Ω·cm, insulation installation meets the immersion requirements of electronic components, dielectric constant (1kHz) is 2.08-2.15, foam is less than 10 / 0mL, and there are no large number of bubbles during circulation.

[0053] Kinematic viscosity refers to the time it takes for a given volume of liquid to flow through a calibrated glass capillary viscometer under gravity at a constant temperature. Kinematic viscosity is an important indicator of liquid flowability, reflecting the magnitude of internal friction generated by the relative motion between molecules within the base oil under gravity. Viscosity index is a conventional value representing the viscosity of a base oil as a function of temperature; generally, a higher viscosity index indicates a smaller change in viscosity with temperature, meaning the base oil maintains a more stable viscosity at different temperatures.

[0054] One embodiment of this application provides a method for preparing PAO4 ultrapure immersion coolant, comprising the following steps:

[0055] By weight percentage, 99.82-99.88% of ultrapure polyalphaolefin synthetic base oil PAO4 was added to the reactor, and the reactor was heated to 55℃-65℃ by water bath heating.

[0056] Add 0.1-0.15% of the antioxidant to the reaction vessel and stir at 400 rpm for 40 minutes until completely dissolved;

[0057] After cooling to 55℃, add 0.019-0.03% passivating agent to the reactor and stir for 20 minutes;

[0058] After cooling to 50℃, 0.001% of defoamer was added to the reactor and stirred for 10 minutes. The mixture was then filtered through a 5μm filter membrane to obtain PAO4 ultrapure immersion coolant. The defoamer needs to be diluted 100 times with PAO4 first.

[0059] The PAO4 ultrapure immersion coolant is prepared by a completely closed stirring process, which prevents moisture and oxygen from the air from mixing into the interior.

[0060] According to one embodiment of this application, a liquid-cooled chassis is provided, wherein the interior of the liquid-cooled chassis is filled with a PAO4 ultrapure immersion coolant of the first aspect, and the CPU, GPU, and motherboard components inside the liquid-cooled chassis are completely immersed in the PAO4 ultrapure immersion coolant.

[0061] First embodiment:

[0062] By weight percentage, 998.2g of ultrapure polyalphaolefin synthetic base oil PAO4 was added to the reactor, and the reactor was heated to 55°C by water bath heating.

[0063] Add 1.5g of dioctyldiphenylamine to the reaction vessel and stir at 400rpm for 40min until completely dissolved;

[0064] After cooling to 55℃, 0.29g of alkylated benzotriazole was added to the reactor and stirred for 20min.

[0065] After cooling to 50℃, 0.01g of polyacrylate was added to the reactor and stirred for 10min. After filtration through a 5μm filter membrane, PAO4 ultrapure immersion coolant was obtained. The defoamer needs to be diluted 100 times with PAO4 first.

[0066] The PAO4 ultrapure immersion coolant is prepared by a completely closed stirring process, which prevents moisture and oxygen from the air from mixing into the interior.

[0067] Second embodiment:

[0068] By weight percentage, 998.5g of ultrapure polyalphaolefin synthetic base oil PAO4 was added to the reactor, and the reactor was heated to 55°C by water bath heating.

[0069] Add 1.25g of dioctyldiphenylamine to the reaction vessel and stir at 400rpm for 40min until completely dissolved;

[0070] After cooling to 55℃, 0.24g of alkylated benzotriazole was added to the reactor and stirred for 20min.

[0071] After cooling to 50℃, 0.01g of polyacrylate was added to the reactor and stirred for 10min. After filtration through a 5μm filter membrane, PAO4 ultrapure immersion coolant was obtained. The defoamer needs to be diluted 100 times with PAO4 first.

[0072] The PAO4 ultrapure immersion coolant is prepared by a completely closed stirring process, which prevents moisture and oxygen from the air from mixing into the interior.

[0073] Third embodiment:

[0074] By weight percentage, 998.8g of ultrapure polyalphaolefin synthetic base oil PAO4 was added to the reactor, and the reactor was heated to 55°C by water bath heating.

[0075] Add 1g of dioctyldiphenylamine to the reaction vessel and stir at 400rpm for 40min until completely dissolved;

[0076] After cooling to 55℃, 0.19g of alkylated benzotriazole was added to the reactor and stirred for 20min.

[0077] After cooling to 50℃, 0.01g of polyacrylate was added to the reactor and stirred for 10min. After filtration through a 5μm filter membrane, PAO4 ultrapure immersion coolant was obtained. The defoamer needs to be diluted 100 times with PAO4 first.

[0078] The PAO4 ultrapure immersion coolant is prepared by a completely closed stirring process, which prevents moisture and oxygen from the air from mixing into the interior.

[0079] Comparative Example:

[0080] 1000g of ultrapure polyalphaolefin synthetic base oil PAO4 was added to the reactor by weight percentage. The reactor was heated to 55°C by water bath heating, stirred for 10 minutes, cooled, and filtered through a 5μm filter membrane to obtain ultrapure PAO4 immersion coolant.

[0081] The preparation parameters of the immersion coolant in Examples 1-3 and the comparative examples are shown in Table 1.

[0082] Ultra-pure polyalphaolefin synthetic base oil PAO4 998.2g 998.5g 998.8g 1000g dioctyldiphenylamine 1.5g 1.25g 1g 0g Alkylated benzotriazole 0.29g 0.24g 0.19g 0g Polyacrylate 0.01g 0.01g 0.01g 0g

[0083] Table 1

[0084] The QC test results for Examples 1-3 and the comparative examples are shown in Table 2:

[0085] Kinematic viscosity at 40℃ (cSt) D445 19.52 19.51 19.50 19.50 Kinematic viscosity at 100℃ (cSt) D445 5.63 5.62 5.61 5.61 Acid value (mgKOH / g) ASTM D664 0.014 0.012 0.010 0.007 Moisture content (ppm) —— 9 8 8 7 Flash point (°C) —— 219 220 220 220 Pour point (°C) —— <-55 <-55 <-55 <-60 <![CDATA[Density (kg / m 3 )]]> —— 821 820 820 820 Dielectric strength (kV / 2.5mm) D1816 52 53 53 54 Volume resistivity (Ω·cm) D1169 <![CDATA[8×10 13 ]]> <![CDATA[1×10 14 ]]> <![CDATA[1×10 14 ]]> <![CDATA[1.5×10 14 ]]> Dielectric constant (1kHz) D924 2.09 2.08 2.08 2.08 Copper sheet corrosion (100℃, 3h) D130 1a 1a 1a 3a Foam sequence I (mL) D892 0 / 0 0 / 0 3 / 0 18 / 5 Liquid phase corrosion (distilled water) D665 pass pass pass Not approved

[0086] Table 2

[0087] According to Tables 1 and 2, the basic physical properties of the PAO4 ultrapure immersion coolant in Examples 1-3 all meet the technical requirements. The kinematic viscosity at 40℃ is all within the range of 18-21 cSt (19.50-19.52 cSt), the acid value is all <0.02 mg KOH / g (0.010-0.014), the water content is all <10 ppm (8-9 ppm), the flash point is all >208℃ (219-220℃), the pour point is all <-55℃, and the density is all between 818-825 kg / m³. 3 Within the range (820-821 kg / m³) 3 The dielectric strength is all >48kV / 2.5mm (52-53kV), and the volume resistivity is all >1x10. 13 Ω·cm (8x10 13 Ω·cm -1x10 14 The dielectric constants are all in the range of 2.08-2.15, and the foam content is <10 / 0 mL.

[0088] Examples 1-3 cover the lower, median, and upper limits of the formulation range, respectively, and all meet the requirements, proving that the dosage range of 99.82-99.88% ultrapure PAO4 is reasonable and feasible. Due to the extremely low total amount of additives (0.12-0.18%), the differences in physical properties among the three examples are minimal (viscosity change of only 0.02 cSt, density change of only 1 kg / m³). 3 This fully embodies the "ultra-pure" design concept, replacing a large number of functional additives with the natural high quality of the base.

[0089] The comparative example (pure ultrapure PAO4 base oil) showed the best electrical properties, but the copper foil corrosion was severely degraded to grade 3a and the foam exceeded the standard by 18 / 5mL. This proves that even under extremely low addition conditions (only three additives, total addition <0.18%), ABTA copper passivator and polyacrylate defoamer are still indispensable for protecting PCB copper foil and suppressing circulating bubbles.

[0090] Ultra-pure PAO4 base oil (saturated hydrocarbon content ≥99.5%, hydrosaturation >99.5%) naturally possesses ultra-high electrical properties due to its extremely low impurity content, with a baseline volume resistivity of 1.5×10⁻⁶. 14 Ω·cm (comparative example), still maintained at 8 × 10 even in the presence of additives. 13 Ω·cm⁻¹×10 14 Ω·cm; is the technical requirement (>1×10⁻⁶). 13 This allows the formula to achieve multiple objectives simultaneously, including high heat capacity, ultra-high insulation, long-lasting oxidation resistance, and low-temperature copper protection, with only a very small amount of additives (0.12-0.18%).

[0091] PAO4 ultrapure immersion coolant is precisely suited for medium-to-high power equipment ranging from 600-1200W. Its extremely low total additive content maximizes the oil's heat capacity, preventing localized high temperatures under full load. The ultrapure base provides naturally high insulation, exhibiting excellent breakdown voltage and volume resistivity. Extremely low DODPA dosage provides long-lasting antioxidant protection, with slow acid value increases and extended replacement cycles. ABTA replaces ordinary TTA without precipitation at low temperatures, providing stable protection for PCB copper foil year-round. Only 0.001% trace amounts of non-silicone defoaming ensure no continuous bubbles during circulation and no silicon precipitation contamination. The entire preparation process is low-temperature and closed-loop, using readily available commercial raw materials, resulting in low production costs and suitability for mass production. With a viscosity of 18-21 cSt, it balances heat dissipation and circulation energy consumption, offering lower pump consumption compared to PAO6 and greater heat dissipation margin compared to PAO2.

[0092] In summary, the present invention provides a PAO4 ultrapure immersion coolant and its preparation method, as well as a liquid-cooled chassis. The ultrapure polyalphaolefin (PAO4) synthetic base oil accounts for over 99.82%, with extremely low total additive content, maximizing the oil's heat capacity and preventing localized high temperatures under full load (600-1200W). The ultrapure PAO4 synthetic base oil has extremely low base impurities, naturally exhibits ultra-high insulation, and demonstrates excellent breakdown voltage and volume resistivity. Low-addition DODPA provides long-lasting antioxidant protection, and the acid value increases slowly during long-term high-temperature operation. Product replacement cycle extended; alkylated benzotriazole replaces ordinary TTA, with no precipitation at low temperatures, providing stable protection for PCB copper foil against catalytic oxidation throughout the year; only 0.001% trace amount of non-silicone defoaming, no continuous bubbles during circulation, eliminating the problem of silicon precipitation contaminating the circuit board; the entire preparation process is carried out in a low-temperature nitrogen-sealed environment, with no high-temperature reactions, readily available commercial raw materials, low production costs, and suitability for mass production; viscosity 18-21 cSt, balancing heat dissipation capacity and circulation energy consumption, with lower pump consumption compared to PAO6 and greater heat dissipation margin compared to PAO2.

[0093] The specific embodiments of the invention have been described above. It should be understood that the invention is not limited to the specific embodiments described above, and the devices and structures not described in detail should be understood to be implemented in a manner common to the art; those skilled in the art can make various modifications or alterations within the scope of the claims, and make several simple deductions, variations or substitutions, which do not affect the substantive content of the invention.

Claims

1. A PAO4 ultrapure immersion coolant, characterized in that, It contains the following components by weight percentage: It contains 99.82-99.88% ultrapure polyalphaolefin synthetic base oil PAO4, 0.1-0.15% antioxidant, 0.019-0.03% passivator, and 0.001% defoamer, with the sum of the weight percentages of each component being 100%.

2. The PAO4 ultrapure immersion coolant according to claim 1, characterized in that, The antioxidant is an aromatic amine antioxidant; the passivating agent is a metal passivating agent; and the defoamer is a non-silicone defoamer.

3. The PAO4 ultrapure immersion coolant according to claim 2, characterized in that, The aromatic amine antioxidant is dioctyl diphenylamine; the metal passivating agent is alkylated benzotriazole; and the non-silicone defoamer is polyacrylate.

4. The PAO4 ultrapure immersion coolant according to claim 1, characterized in that, The kinematic viscosity of the ultrapure polyalphaolefin synthetic base oil PAO4 at 40°C is 18-21 cSt, and the viscosity index of the ultrapure polyalphaolefin synthetic base oil PAO4 is 120-130.

5. A method for preparing a PAO4 ultrapure immersion coolant, characterized in that, Includes the following steps: By weight percentage, 99.82-99.88% of ultrapure polyalphaolefin synthetic base oil PAO4 was added to the reactor and the temperature was raised to 55℃-65℃. Add 0.1-0.15% of the antioxidant to the reaction vessel and stir until completely dissolved; After cooling to 55℃, add 0.019-0.03% passivating agent to the reactor and stir. After cooling to 50°C, 0.001% of defoamer was added to the reactor, and after stirring and filtration, PAO4 ultrapure immersion coolant was obtained.

6. The method for preparing a PAO4 ultrapure immersion coolant according to claim 5, characterized in that, The reactor was heated to 55℃-65℃ using a water bath. After the antioxidant is added to the reaction vessel, it is stirred at 400 rpm for 40 minutes until it is completely dissolved. After the passivating agent is added to the reaction vessel, it is stirred for 20 minutes. The defoamer was added to the reaction vessel and stirred for 10 minutes; After filtration using a 5μm filter membrane, PAO4 ultrapure immersion coolant was obtained.

7. The method for preparing a PAO4 ultrapure immersion coolant according to claim 6, characterized in that, The preparation process of PAO4 ultrapure immersion coolant involves completely closed stirring. According to claim 5, the method for preparing a PAO4 ultrapure immersion coolant is characterized in that the defoamer added to the reaction vessel needs to be diluted 100 times with PAO4 first.

8. A liquid-cooled chassis, characterized in that, The liquid-cooled chassis is filled with a PAO4 ultrapure immersion coolant as described in any one of claims 1-5.