Method for preparing perfluoropolyether with different molecular weights by formula type solvent

Abstract

The invention discloses a method for preparing perfluoropolyether with different molecular weights by a formula type solvent, and belongs to the technical field of perfluoropolyether preparation, the method comprises the following steps: mixing one or more hydrofluoroethers, an aprotic polar solvent and a catalyst, adding the mixture into a reaction kettle, introducing hexafluoropropylene oxide for polymerization until the reaction temperature reaches 25 + / -2 DEG C, and stopping the reaction to obtain the perfluoropolyether, the polymerization yield is greater than 95%; and controlling the type and ratio of the added hydrofluoroether to obtain perfluoropolyether with different molecular weights. The perfluoropolyether has the beneficial effects that the perfluoropolyether with specific molecular weight is prepared by combining different types of hydrofluoroethers with different proportions with other system compounds in the formula, and the perfluoropolyether is high in reaction yield, safe, environment-friendly, mild in condition and simple in process and can be widely applied in industry.

Description

Technical Field

[0001] The invention relates to the technical field of perfluoropolyether preparation, and in particular to a method for preparing perfluoropolyethers with different molecular weights using a formulated solvent. Background Art

[0002] The structural formula of K-type perfluoropolyether is: CF3CF2CF2O [CF(CF3)CF2O] n CF (CF3) COF, which contains only three elements, C, F, and O, has the properties of heat resistance, oxidation resistance, radiation resistance, corrosion resistance, and non-flammability. It is used as a lubricant in cutting-edge fields such as military, aerospace, and nuclear industry. Perfluoropolyether, as a high-end lubricant, has a very broad application scenario, including but not limited to high vacuum fluoroether oil, high-performance grease / base oil, perfluoropolyether methanol intermediates and other fields.

[0003] Perfluoropropylene oxide (HFPO) is used as a raw material, and fluoride ions are used as a catalyst in an aprotic solvent to obtain a perfluoropropylene oxide oligomer containing an acyl fluoride end group, and the active acyl fluoride end group is then stabilized to obtain a perfluoropolyether. The molecular weight distribution of the perfluoropolyether synthesized by this route is below 4000. For example, the invention patent application with the publication number CN113321798A discloses a method for preparing a low-molecular-weight saturated perfluoropolyether with high stability, wherein the purified perfluoroepoxy compound is used as a raw material, and an alkali metal oxide is polymerized step by step at -40°C to 10°C in an aprotic solvent to obtain a perfluoropolyether, and then a hydroxide-stabilized catalyst is added to react to obtain a saturated perfluoropolyether containing only C, F, and O. However, the molecular weight of the synthesized perfluoropolyether is 1000-2000, and the gap in the synthesis of high-end perfluoropolyether is large, so it is necessary to prepare a perfluoropolyether with an average molecular weight ranging from 4000 to 15000.

[0004] The invention patent application with publication number CN105273178A discloses a method for preparing a hexafluoropropylene oxide homopolymer, which uses hexafluoropropylene dimer as a fluorine-containing solvent to prepare a perfluoropolyether, which has a large kinematic viscosity at low temperatures, poor dispersion effect, poor polymerization effect, and low conversion rate. Summary of the invention

[0005] In order to solve the problem that the molecular weight distribution of perfluoropolyether synthesized by the existing route is below 4000, the present invention provides a method for preparing perfluoropolyethers with different molecular weights by using a formulated solvent. The perfluoropolyethers with different molecular weights are prepared by developing a formulated solvent so that the average molecular weight thereof varies from 4000 to 5999, 6000 to 7999, 8000 to 9999, 10000 to 11999, and 12000 to 15000. The specific technical scheme is as follows:

[0006] A method for preparing perfluoropolyethers of different molecular weights using a formulated solvent, comprising:

[0007] One or more hydrofluoroethers, aprotic polar solvents and catalysts are mixed and added to a reactor, and hexafluoropropylene oxide is introduced for polymerization until the reaction temperature reaches 25±2° C., and the reaction is stopped to obtain a perfluoropolyether, and the polymerization yield is greater than 95%;

[0008] By controlling the type and ratio of hydrofluoroether added, perfluoropolyethers with different molecular weights can be obtained.

[0009] Preferably, the hydrofluoroether is selected from perfluoro-3,5-dioxahexyl methyl ether, or a mixture of perfluoro-3,5-dioxahexyl methyl ether and one or more of perfluoro-3-oxabutyl methyl ether, nonafluoroisobutyl methyl ether, and 3-methoxy-2-trifluoromethylperfluorobutane.

[0010] Preferably, the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to aprotic polar solvent and catalyst is 1.0:(0.1-3.0):(0.1-1.5).

[0011] The added hydrofluoroether is single perfluoro-3,5-dioxahexyl methyl ether, and a perfluoropolyether with a molecular weight of 4000-5999 is prepared;

[0012] Or controlling the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to nonafluoroisobutyl methyl ether to be (2.0-3.0):1.0 to prepare a perfluoropolyether with a molecular weight of 6000-7999;

[0013] Or controlling the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to nonafluoroisobutyl methyl ether and 3-methoxy-2-trifluoromethyl perfluorobutane to be (3.5-4.5):(4.5-5.5):1.0 to prepare a perfluoropolyether with a molecular weight of 8000-9999;

[0014] Or controlling the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to perfluoro-3-oxabutyl methyl ether and nonafluoroisobutyl methyl ether to be (1.5-2.5):(2.0-3.0):1.0 to prepare a perfluoropolyether with a molecular weight of 10000-11999;

[0015] Or the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to perfluoro-3-oxabutyl methyl ether and nonafluoroisobutyl methyl ether is controlled to be (2.5-3.5):(3.0-4.0):1.0 to prepare a perfluoropolyether with a molecular weight of 12000-15000.

[0016] Preferably, the type and ratio of hydrofluoroether added are controlled as follows:

[0017] The added hydrofluoroether is single perfluoro-3,5-dioxahexyl methyl ether, and a perfluoropolyether with a molecular weight of 4000-5999 is prepared;

[0018] Or controlling the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to nonafluoroisobutyl methyl ether to be (2.3-2.8):1.0 to prepare a perfluoropolyether with a molecular weight of 6000-7999;

[0019] Or controlling the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to nonafluoroisobutyl methyl ether and 3-methoxy-2-trifluoromethyl perfluorobutane to be (3.8-4.2):(4.6-4.8):1.0 to prepare a perfluoropolyether with a molecular weight of 8000-9999;

[0020] Or controlling the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to perfluoro-3-oxabutyl methyl ether and nonafluoroisobutyl methyl ether to be (1.6-1.8):(2.2-2.8):1.0 to prepare a perfluoropolyether with a molecular weight of 10000-11999;

[0021] Or the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to perfluoro-3-oxabutyl methyl ether and nonafluoroisobutyl methyl ether is controlled to be (2.5-2.8):(3.2-3.5):1.0 to prepare a perfluoropolyether with a molecular weight of 12000-15000.

[0022] Preferably, the catalyst is potassium fluoride or cesium fluoride.

[0023] Preferably, the aprotic polar solvent is tetraethylene glycol dimethyl ether.

[0024] Preferably, when hexafluoropropylene oxide is introduced for polymerization, the reactor is controlled at a specific temperature;

[0025] When preparing perfluoropolyether with a molecular weight of 4000-5999, the temperature of the reactor during the polymerization of hexafluoropropylene oxide is controlled to be -15°C ± 3°C;

[0026] Or when preparing perfluoropolyether with a molecular weight of 6000-7999, the temperature of the reactor during the polymerization of hexafluoropropylene oxide is controlled to be -20°C ± 3°C;

[0027] Or when preparing perfluoropolyether with a molecular weight of 8000-9999, the temperature of the reactor during the polymerization of hexafluoropropylene oxide is controlled to be -25°C ± 3°C;

[0028] Or when preparing perfluoropolyether with a molecular weight of 10000-11999, the temperature of the reactor during the polymerization of hexafluoropropylene oxide is controlled to be -27°C ± 3°C;

[0029] Or when preparing perfluoropolyether with a molecular weight of 12000-15000, the temperature of the reactor is controlled to be -30°C ± 3°C when hexafluoropropylene oxide is introduced for polymerization.

[0030] Preferably, the reaction time is 5-15 hours.

[0031] Beneficial effects:

[0032] The beneficial effects produced by the technical solution of the present invention are as follows:

[0033] (1) Different hydrofluoroethers have different kinematic viscosities at different temperatures. The lower the temperature, the greater the viscosity and the less likely it is for the addition reaction to occur. Hydrofluoroethers are added to adjust the viscosity of the intermediate product and promote continuous addition of the system.

[0034] (2) By combining different types and proportions of hydrofluoroether with other system compounds in the formula, perfluoropolyether with a specific molecular weight is prepared. The reaction has high yield, is safe and environmentally friendly, has mild conditions, and a simple process, and can be widely used in industry. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Embodiment 1:

[0037] 200g perfluoro-3,5-dioxahexyl methyl ether (0.71mol), 300g tetraethylene glycol dimethyl ether (1.35mol) and 40g dry potassium fluoride (0.69mol) were added to a 2L reactor, and the reaction temperature was adjusted to -15℃±3℃. After the temperature stabilized, hexafluoropropylene oxide was added to the polymerization reactor at a rate of 3g / min. After adding 800g, the addition of hexafluoropropylene oxide was stopped, and the mixture was stirred for 2h. Then the reactor temperature was raised to 25℃, and the reaction was completed. After the reaction product was filtered, the reaction product was separated, and the lower layer was the final product, and the upper layer was the reaction system. Finally, 782g of the target product was obtained, and the yield was 97.8%. The average molecular weight of the product was 4690g / mol according to GC chromatography and nuclear magnetic analysis.

[0038] Embodiment 2:

[0039] 230g of perfluoro-3,5-dioxahexyl methyl ether (0.82mol), 320g of tetraethylene glycol dimethyl ether (1.44mol) and 40g of dry potassium fluoride (0.69mol) were added to a 2L reactor, and the reaction temperature was adjusted to -15°C ± 3°C. After the temperature stabilized, hexafluoropropylene oxide was added to the polymerization reactor at a rate of 3g / min. After adding 800g, the addition of hexafluoropropylene oxide was stopped, and the mixture was stirred for 2h. Then the reactor temperature was raised to 25°C, and the reaction was completed. After the reaction product was filtered, the reaction product was separated, and the lower layer was the final product, and the upper layer was the reaction system. Finally, 782g of the target product was obtained, and the yield was 97.8%. The average molecular weight of the product was 4720g / mol according to GC chromatography and nuclear magnetic resonance analysis.

[0040] Embodiment 3:

[0041] 300g perfluoro-3,5-dioxahexyl methyl ether (1.06mol), 100g nonafluoroisobutyl methyl ether (0.40mol), 100g tetraethylene glycol dimethyl ether (0.45mol) and 40g dry potassium fluoride (0.69mol) were added to a 2L reactor, and the reaction temperature was adjusted to -20℃±3℃. After the temperature stabilized, hexafluoropropylene oxide was added to the polymerization reactor at a rate of 2.5g / min. After adding 800g, the addition of hexafluoropropylene oxide was stopped, and the mixture was stirred for another 2h. Then the reactor temperature was raised to 25℃, and the reaction was completed. After the reaction product was filtered, the reaction product was separated, and the lower layer was the final product, and the upper layer was the reaction system. Finally, 775g of the target product was obtained, and the yield was 96.9%. The average molecular weight of the product was 6600g / mol according to GC chromatography and nuclear magnetic resonance analysis.

[0042] Embodiment 4:

[0043] 320g perfluoro-3,5-dioxahexyl methyl ether (1.13mol), 108g nonafluoroisobutyl methyl ether (0.43mol), 110g tetraethylene glycol dimethyl ether (0.50mol) and 40g dry potassium fluoride (0.69mol) were added to a 2L reactor, and the reaction temperature was adjusted to -20℃±3℃. After the temperature stabilized, hexafluoropropylene oxide was added to the polymerization reactor at a rate of 2.5g / min. After adding 800g, the addition of hexafluoropropylene oxide was stopped, and the mixture was stirred for another 2h. Then the reactor temperature was raised to 25℃, and the reaction was completed. After the reaction product was filtered, the reaction product was separated, and the lower layer was the final product, and the upper layer was the reaction system. Finally, 775g of the target product was obtained, and the yield was 96.9%. The average molecular weight of the product was 6680g / mol according to GC chromatography and nuclear magnetic resonance analysis.

[0044] Embodiment 5:

[0045] 200g perfluoro-3,5-dioxahexyl methyl ether (0.71mol), 200g nonafluoroisobutyl methyl ether (0.80mol), 50g 3-methoxy-2-trifluoromethyl perfluorobutane (0.17mol), 100g tetraethylene glycol dimethyl ether (0.45mol) and 40g dry potassium fluoride (0.69mol) were added to a 2L reactor, and the reaction temperature was adjusted to -25°C ± 3°C. After the temperature stabilized, hexafluoropropylene oxide was added to the polymerization reactor at a rate of 1.5g / min. After adding 800g, the addition of hexafluoropropylene oxide was stopped and stirred for another 2h. Then the reactor temperature was raised to 25°C and the reaction was completed. After the reaction product was filtered, the reaction product was separated and the lower layer was the final product and the upper layer was the reaction system. Finally, 768g of the target product was obtained with a yield of 96%. The average molecular weight of the product was 8970g / mol according to GC chromatography and nuclear magnetic analysis.

[0046] Embodiment 6:

[0047] 210g perfluoro-3,5-dioxahexyl methyl ether (0.74mol), 210g nonafluoroisobutyl methyl ether (0.84mol), 55g 3-methoxy-2-trifluoromethyl perfluorobutane (0.18mol), 108g tetraethylene glycol dimethyl ether (0.49mol) and 40g dry potassium fluoride (0.69mol) were added to a 2L reactor, and the reaction temperature was adjusted to -25°C ± 3°C. After the temperature stabilized, hexafluoropropylene oxide was added to the polymerization reactor at a rate of 1.5g / min. After adding 800g, the addition of hexafluoropropylene oxide was stopped and stirred for another 2h. Then the reactor temperature was raised to 25°C and the reaction was completed. After the reaction product was filtered, the reaction product was separated and the lower layer was the final product and the upper layer was the reaction system. Finally, 768g of the target product was obtained with a yield of 96%. The average molecular weight of the product was 9210g / mol according to GC chromatography and nuclear magnetic analysis.

[0048] Embodiment 7:

[0049] 200g perfluoro-3,5-dioxahexyl methyl ether (0.71mol), 200g perfluoro-3-oxabutyl methyl ether (0.93mol), 100g nonafluoroisobutyl methyl ether (0.40mol), 80g tetraethylene glycol dimethyl ether (0.36mol) and 20g dry potassium fluoride (0.345mol) were added to a 2L reactor, and the reaction temperature was adjusted to -27℃±3℃. After the temperature stabilized, hexafluoropropylene oxide was added to the polymerization reactor at a rate of 1.5g / min. After adding 800g, the addition of hexafluoropropylene oxide was stopped and stirred for another 2h; then the reactor temperature was raised to 25℃, and the reaction was completed. After the reaction product was filtered, the reaction product was separated, the lower layer was the final product, and the upper layer was the reaction system. Finally, 780g of the target product was obtained, and the yield was 97.5%. The average molecular weight of the product was 10090g / mol according to GC chromatography and nuclear magnetic resonance analysis.

[0050] Embodiment 8:

[0051] 210g perfluoro-3,5-dioxahexyl methyl ether (0.74mol), 210g perfluoro-3-oxabutyl methyl ether (0.97mol), 108g nonafluoroisobutyl methyl ether (0.432mol), 85g tetraethylene glycol dimethyl ether (0.382mol) and 20g dry potassium fluoride (0.345mol) were added to a 2L reactor, and the reaction temperature was adjusted to -27℃±3℃. After the temperature stabilized, hexafluoropropylene oxide was added to the polymerization reactor at a rate of 1.5g / min. After adding 800g, the addition of hexafluoropropylene oxide was stopped and stirred for another 2h; then the reactor temperature was raised to 25℃, and the reaction was completed. After the reaction product was filtered, the reaction product was separated, the lower layer was the final product, and the upper layer was the reaction system. Finally, 780g of the target product was obtained with a yield of 97.5%. The average molecular weight of the product was 10080 g / mol as determined by GC chromatography and NMR analysis.

[0052] Embodiment 9:

[0053] 300g perfluoro-3,5-dioxahexyl methyl ether (1.06mol), 300g perfluoro-3-oxabutyl methyl ether (1.39mol), 100g nonafluoroisobutyl methyl ether (0.40mol), 80g tetraethylene glycol dimethyl ether (0.36mol) and 20g dry potassium fluoride (0.345mol) were added to a 2L reactor, and the reaction temperature was adjusted to -30℃±3℃. After the temperature stabilized, hexafluoropropylene oxide was added to the polymerization reactor at a rate of 1.0g / min. After adding 800g, the addition of hexafluoropropylene oxide was stopped and stirred for another 2h; then the reactor temperature was raised to 25℃, and the reaction was completed. After the reaction product was filtered, the reaction product was separated, the lower layer was the final product, and the upper layer was the reaction system. Finally, 770g of the target product was obtained, with a yield of 96.2%. The average molecular weight of the product was 13400g / mol according to GC chromatography and nuclear magnetic resonance analysis.

[0054] Embodiment 10:

[0055] 310g perfluoro-3,5-dioxahexyl methyl ether (1.10mol), 310g perfluoro-3-oxabutyl methyl ether (1.435mol), 108g nonafluoroisobutyl methyl ether (0.432mol), 88g tetraethylene glycol dimethyl ether (0.396mol) and 20g dry potassium fluoride (0.345mol) were added to a 2L reactor, and the reaction temperature was adjusted to -30℃±3℃. After the temperature stabilized, hexafluoropropylene oxide was added to the polymerization reactor at a rate of 1.0g / min. After adding 800g, the addition of hexafluoropropylene oxide was stopped and stirred for another 2h; then the reactor temperature was raised to 25℃, and the reaction was completed. After the reaction product was filtered, the reaction product was separated, the lower layer was the final product, and the upper layer was the reaction system. Finally, 770g of the target product was obtained with a yield of 96.2%. The average molecular weight of the product was 13450 g / mol as determined by GC chromatography and NMR analysis.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing perfluoropolyethers of different molecular weights using a formulated solvent, characterized in that: include: One or more hydrofluoroethers, aprotic polar solvents and catalysts are mixed and added to a reactor, and hexafluoropropylene oxide is introduced for polymerization until the reaction temperature reaches 25±2° C., and the reaction is stopped to obtain a perfluoropolyether, and the polymerization yield is greater than 95%; By controlling the type and ratio of hydrofluoroether added, perfluoropolyethers with different molecular weights can be obtained.

2. The method for preparing perfluoropolyethers of different molecular weights using a formulated solvent according to claim 1, characterized in that: The hydrofluoroether is selected from perfluoro-3,5-dioxahexyl methyl ether, or a mixture of perfluoro-3,5-dioxahexyl methyl ether and one or more of perfluoro-3-oxabutyl methyl ether, nonafluoroisobutyl methyl ether, and 3-methoxy-2-trifluoromethylperfluorobutane.

3. The method for preparing perfluoropolyethers of different molecular weights using a formulated solvent according to claim 2, characterized in that: The molar ratio of perfluoro-3,5-dioxahexyl methyl ether to the aprotic polar solvent and the catalyst is 1.0:(0.1-3.0):(0.1-1.5).

4. The method for preparing perfluoropolyethers of different molecular weights using a formulated solvent according to claim 3, characterized in that: The molar ratio of perfluoro-3,5-dioxahexyl methyl ether to the aprotic polar solvent and the catalyst is 1.0:(0.1-2.0):(0.1-1.0).

5. The method for preparing perfluoropolyethers of different molecular weights using a formulated solvent according to claim 2, characterized in that: The type and ratio of hydrofluoroether added are controlled as follows: The added hydrofluoroether is single perfluoro-3,5-dioxahexyl methyl ether, and a perfluoropolyether with a molecular weight of 4000-5999 is prepared; Or controlling the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to nonafluoroisobutyl methyl ether to be (2.0-3.0):1.0 to prepare a perfluoropolyether with a molecular weight of 6000-7999; Or controlling the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to nonafluoroisobutyl methyl ether and 3-methoxy-2-trifluoromethyl perfluorobutane to be (3.5-4.5):(4.5-5.5):1.0 to prepare a perfluoropolyether with a molecular weight of 8000-9999; Or controlling the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to perfluoro-3-oxabutyl methyl ether and nonafluoroisobutyl methyl ether to be (1.5-2.5):(2.0-3.0):1.0 to prepare a perfluoropolyether with a molecular weight of 10000-11999; Or the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to perfluoro-3-oxabutyl methyl ether and nonafluoroisobutyl methyl ether is controlled to be (2.5-3.5):(3.0-4.0):1.0 to prepare a perfluoropolyether with a molecular weight of 12000-15000.

6. The method for preparing perfluoropolyethers of different molecular weights using a formulated solvent according to claim 5, characterized in that: The type and ratio of hydrofluoroether added are controlled as follows: The added hydrofluoroether is single perfluoro-3,5-dioxahexyl methyl ether, and a perfluoropolyether with a molecular weight of 4000-5999 is prepared; Or controlling the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to nonafluoroisobutyl methyl ether to be (2.3-2.8):1.0 to prepare a perfluoropolyether with a molecular weight of 6000-7999; Or controlling the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to nonafluoroisobutyl methyl ether and 3-methoxy-2-trifluoromethyl perfluorobutane to be (3.8-4.2):(4.6-4.8):1.0 to prepare a perfluoropolyether with a molecular weight of 8000-9999; Or controlling the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to perfluoro-3-oxabutyl methyl ether and nonafluoroisobutyl methyl ether to be (1.6-1.8):(2.2-2.8):1.0 to prepare a perfluoropolyether with a molecular weight of 10000-11999; Or the molar ratio of perfluoro-3,5-dioxahexyl methyl ether to perfluoro-3-oxabutyl methyl ether and nonafluoroisobutyl methyl ether is controlled to be (2.5-2.8):(3.2-3.5):1.0 to prepare a perfluoropolyether with a molecular weight of 12000-15000.

7. The method for preparing perfluoropolyethers of different molecular weights using a formulated solvent according to claim 1, characterized in that: The catalyst is potassium fluoride or cesium fluoride.

8. The method for preparing perfluoropolyethers of different molecular weights using a formulated solvent according to claim 1, characterized in that: The aprotic polar solvent is tetraethylene glycol dimethyl ether.

9. A method for preparing perfluoropolyethers of different molecular weights using a formulated solvent according to any one of claims 1 to 8, characterized in that: When hexafluoropropylene oxide is introduced for polymerization, the reactor is controlled at a specific temperature; When preparing perfluoropolyether with a molecular weight of 4000-5999, the temperature of the reactor during the polymerization of hexafluoropropylene oxide is controlled to be -15°C ± 3°C; Or when preparing perfluoropolyether with a molecular weight of 6000-7999, the temperature of the reactor during the polymerization of hexafluoropropylene oxide is controlled to be -20°C ± 3°C; Or when preparing perfluoropolyether with a molecular weight of 8000-9999, the temperature of the reactor during the polymerization of hexafluoropropylene oxide is controlled to be -25°C ± 3°C; Or when preparing perfluoropolyether with a molecular weight of 10000-11999, the temperature of the reactor during the polymerization of hexafluoropropylene oxide is controlled to be -27°C ± 3°C; Or when preparing perfluoropolyether with a molecular weight of 12000-15000, the temperature of the reactor is controlled to be -30°C ± 3°C when hexafluoropropylene oxide is introduced for polymerization.

10. The method for preparing perfluoropolyethers of different molecular weights using a formulated solvent according to claim 1, characterized in that: The reaction time is 5-15 hours.