A preparation method of perfluoropolyether acyl fluoride

Abstract

The present application relates to the technical field of fluorine-containing fine chemicals, and specifically discloses a method for preparing perfluoropolyether acyl fluoride, which comprises step one, preparation of an initiating system; step two, adding an initiating system and a diluent, cooling, and then introducing hexafluoropropylene oxide, reacting to obtain the first batch of mixtures, separating and purifying, and obtaining the first batch of perfluoropolyether acyl fluoride products; step three, taking the first batch of mixtures in step two, adding a diluent, cooling, and then introducing hexafluoropropylene oxide, reacting to obtain the second batch of mixtures, separating and purifying, and obtaining the second batch of perfluoropolyether acyl fluoride products; step four, taking the second batch of mixtures in step three, separating and purifying, and then introducing hexafluoropropylene oxide, reacting to obtain the third batch of mixtures, separating and purifying, and obtaining the third batch of perfluoropolyether acyl fluoride products. The method for preparing perfluoropolyether acyl fluoride of the present application has the advantage of providing a more economical, more effective, and more controllable method for synthesizing perfluoropolyether acyl fluoride.

Description

Technical Field

[0001] The invention relates to the technical field of fluorine-containing fine chemicals, in particular to a method for preparing perfluoropolyether acyl fluoride. Background Art

[0002] Perfluoropolyether fluoride is an important precursor for the preparation of perfluoropolyether. As the market performance requirements for perfluoropolyether products continue to increase, the demand for perfluoropolyether fluoride, a precursor for the preparation of perfluoropolyether, and perfluoropolyether fluoride products of different molecular weights are increasing.

[0003] At present, the main production methods of perfluoropolyether acyl fluoride include photo-oxidative polymerization technology with tetrafluoroethylene or hexafluoropropylene. This production technology is relatively cheap, but has low yield, complex process and high risk. Another method is anionic polymerization technology with hexafluoropropylene oxide as raw material. This method has a relatively simple process flow, safe production and is widely used in industrial production.

[0004] In the above-mentioned related technologies, the preparation reaction conditions of perfluoropolyether acyl fluoride are strict, and the purity of the raw materials, reaction temperature and other conditions will have a great impact on the raw material conversion rate in the reaction and the average molecular weight of the product. In addition, the currently prepared perfluoropolyether acyl fluoride has a high molecular weight and a wide molecular weight distribution, and must be cut by molecular distillation before it can be put into use. The yield of the available segment perfluoropolyether acyl fluoride obtained by molecular distillation is less than 50%, and the remaining low molecular weight perfluoropolyether acyl fluoride and high molecular weight perfluoropolyether acyl fluoride are mostly not required by the market, resulting in a low total product yield. Therefore, it is urgent to find a simple, efficient, low-cost, narrow and controllable perfluoropolyether acyl fluoride synthesis scheme, which can synthesize perfluoropolyether acyl fluoride products of the required molecular weight without molecular distillation, greatly improve the product yield, and is of great significance to industrial production. Summary of the invention

[0005] In order to provide a more economical, more effective and more controllable method for synthesizing perfluoropolyether acyl fluoride, the present application provides a method for preparing perfluoropolyether acyl fluoride.

[0006] The present application provides a method for preparing perfluoropolyether acyl fluoride, which adopts the following technical scheme:

[0007] A method for preparing perfluoropolyether acyl fluoride comprises the following preparation steps:

[0008] Step 1, preparation of the initiation system: under nitrogen protection, firstly add a catalyst and a solvent into a reaction kettle, cool it down, then introduce hexafluoropropylene oxide, and react at a constant temperature to obtain an initiation system;

[0009] Step 2, adding the initiator system and diluent prepared in step 1 into the polymerization reaction kettle, cooling down, then introducing hexafluoropropylene oxide, reacting at a constant temperature to obtain the first batch of mixture, distilling under reduced pressure, distilling at a higher temperature, filtering, and obtaining the first batch of perfluoropolyether acyl fluoride products;

[0010] Step 3, taking the first batch of perfluoropolyether acyl fluoride products in step 2, adding a diluent, cooling, then introducing hexafluoropropylene oxide, reacting at a constant temperature to obtain a second batch of mixture, distilling under reduced pressure, distilling at a higher temperature, filtering, and obtaining a second batch of perfluoropolyether acyl fluoride products;

[0011] Step 4, taking the second batch of perfluoropolyether acyl fluoride products in step 3, adding a diluent, cooling, then introducing hexafluoropropylene oxide, reacting at a constant temperature to obtain a third batch of mixture, distilling under reduced pressure, distilling at a higher temperature, filtering, and obtaining a third batch of perfluoropolyether acyl fluoride products.

[0012] By adopting the above technical scheme, due to the use of multiple batches of polymerization reactions, compared with the traditional one-pot polymerization, perfluoropolyether acyl fluoride intermediates with different molecular weights can be better controlled, the molecular weight distribution range of the product perfluoropolyether acyl fluoride is narrow and has a certain degree of controllability, and the molecular weight distribution of the perfluoropolyether acyl fluoride obtained by the one-pot method is relatively wide. After the product is obtained, it needs to be further vacuum distilled or molecularly distilled to obtain the desired product.

[0013] The homemade initiation system has a better initiation effect than the traditional acyl fluoride initiation system, and after the initiation system is prepared, the polymerization reaction is carried out in batches without the need to add catalysts, solvents, etc. It has been verified through multiple comparative experiments that there is a possibility of experimental failure during the experiment of the traditional acyl fluoride initiation system, while the homemade initiation system of the present application will not have experimental failure and cause cost losses.

[0014] The product perfluoropolyether acyl fluoride prepared in the present application has a narrow and controllable molecular weight distribution, simple reaction operation, high success rate and safety, is suitable for industrial production, has important significance for industrial production, and increases the application field of perfluoropolyether acyl fluoride products with different molecular weights.

[0015] Optionally, the diluent in step 2, step 3 and step 4 is one or more of Noah7000A, Noah7100, Noah7200, Noah7300, perfluoro-4-methyl-2-pentene, and perfluorononene.

[0016] By adopting the above technical scheme, the use of hydrofluoroether compounds and perfluoro-4-methyl-2-pentene and other fluorine-containing high-boiling point compounds as diluents has a better polymerization effect than traditional diluents at the same temperature, and the experiment can be repeated continuously. Traditional diluents are difficult to recycle and will affect the polymerization reaction to a certain extent, resulting in a low molecular weight of the final product. The use of fluorine-containing high-boiling point diluents greatly saves industrial production costs and reduces energy consumption in industrial production compared to traditional diluents.

[0017] Optionally, in the step 2, the weight ratio of the initiator system, the diluent and the hexafluoropropylene oxide is 3-8:6-10:9-15.

[0018] By adopting the above technical scheme, the prepared initiation system contains a catalyst and a solvent. In the subsequent batch polymerization process, a diluent and hexafluoropropylene oxide are directly added, and hexafluoropropylene oxide and hexafluoropropylene oxide oligomers are further polymerized to obtain perfluoropolyether acyl fluoride with a lower molecular weight.

[0019] Optionally, in step 3, the weight ratio of the first batch of perfluoropolyether acyl fluoride product, diluent and hexafluoropropylene oxide is 5-12:2-8:10-20.

[0020] By adopting the above technical scheme and the raw materials with the above ratio, the first batch of perfluoropolyether acyl fluoride products continue to be used as reaction raw materials to polymerize with hexafluoropropylene oxide, and on the basis of low molecular weight, higher molecular weight perfluoropolyether acyl fluoride is obtained by reaction.

[0021] Optionally, in step 4, the weight ratio of the second batch of perfluoropolyether acyl fluoride product, the diluent and hexafluoropropylene oxide is 5-12:7-15:11-22.

[0022] By adopting the above technical solution and using the raw materials in the above ratio, the second batch of perfluoropolyether acyl fluoride products continue to be used as reaction raw materials to polymerize with hexafluoropropylene oxide to react and generate perfluoropolyether acyl fluoride with a higher molecular weight.

[0023] Optionally, in step 1, under nitrogen protection, firstly, a catalyst and a solvent are added to a reaction kettle, the temperature is lowered to -10°C to 0°C, and then hexafluoropropylene oxide is introduced to react at a constant temperature to obtain an initiation system.

[0024] By adopting the above technical scheme, the molecular weight of perfluoropolyether acyl fluoride can be adjusted by changing the reaction temperature, and a perfluoropolyether acyl fluoride product with a narrower molecular weight distribution can be obtained, thereby expanding the application field of the perfluoropolyether acyl fluoride product.

[0025] Optionally, in step 2, step 3 and step 4, the temperature is lowered to -10°C to 5°C, and the reduced pressure distillation temperature is 40°C to 80°C.

[0026] By adopting the above technical scheme, the molecular weight of perfluoropolyether acyl fluoride can be controlled by adjusting the reaction temperature and the reduced pressure distillation temperature, and a perfluoropolyether acyl fluoride product with high yield and purity can be obtained.

[0027] In a second aspect, the present application provides a perfluoropolyether acyl fluoride product, which is prepared by any of the above-mentioned methods for preparing perfluoropolyether acyl fluoride:

[0028] By adopting the above technical scheme, the perfluoropolyether acyl fluoride product prepared in the present application has a narrow and controllable molecular weight distribution, simple reaction operation, high success rate and safety, and is suitable for industrial production.

[0029] In summary, this application has the following beneficial effects:

[0030] 1. Since the present application adopts a multi-batch polymerization reaction, compared with the traditional one-pot polymerization, the molecular weight distribution range of the product perfluoropolyether acyl fluoride is narrow and has a certain controllability, and the perfluoropolyether product with the required molecular weight can be obtained without molecular distillation, and the yield is greater than 90%, which greatly reduces the waste of useless perfluoropolyether acyl fluoride caused by molecular distillation. The reaction operation is simple, the success rate is high and safe, and it is suitable for industrial production.

[0031] 2. The present application adopts a combination of alkali metal fluoride and crown ether as a catalyst system to replace expensive traditional catalysts. Under the premise of ensuring the catalytic effect, it reduces the disadvantages of high toxicity and high cost of the catalyst and is suitable for industrial production.

[0032] 3. The self-made initiation system of the present application has a better initiation effect than the traditional initiation system, and no catalyst, solvent, etc. are required to be added in the batch polymerization reaction after the initiation system is prepared. After multiple comparative experiments, it has been verified that the self-made initiation system of the present application has a high reaction success rate and a high product yield.

[0033] 4. This application adopts a stable fluorine-containing high-boiling-point diluent to replace the traditional diluent hexafluoropropylene or a polymerization method without a diluent, which solves the disadvantages of the traditional diluent hexafluoropropylene being difficult to recover and separate due to easy polymerization to generate other low-boiling impurities; and the disadvantages of not using a diluent resulting in high product viscosity and high molecular weight that are difficult to stir and control. After the fluorine-containing high-boiling-point diluent is recovered, the test can be repeated more than 50 times with good results; the reaction temperature is higher than that of hexafluoropropylene during the reaction, which reduces the reaction energy consumption and the reaction process is mild. DETAILED DESCRIPTION

[0034] The present application is further described in detail below in conjunction with embodiments and comparative examples.

[0035] The sources of raw materials for the following embodiments and comparative examples are provided: the raw materials for the embodiments and comparative examples can all be purchased commercially.

[0036] Example

[0037] Example 1

[0038] A method for preparing perfluoropolyether acyl fluoride comprises the following preparation steps:

[0039] Step 1, preparation of the initiation system: under nitrogen protection, add 14 g of catalyst KF, 2 g of 18-crown ether-6 and 32 g of solvent tetraethylene glycol dimethyl ether to a reaction kettle that has been dehydrated and dried, cool to -5°C, slowly introduce 220 g of hexafluoropropylene oxide, and keep the temperature to react for 3 hours to obtain an initiation system;

[0040] Step 2: Add 200 g of the initiator system prepared in step 1 and 320 g of the diluent Noah 7100 to the polymerization reactor from which water has been removed, slowly introduce 520 g of hexafluoropropylene oxide after cooling to -3°C, and keep the temperature for 4 hours to obtain the first batch of the mixture, heat the mixture to 70°C and distill under reduced pressure to remove the diluent Noah 7100, then heat the mixture to 110°C and distill to remove the solvent tetraethylene glycol dimethyl ether and low-boiling substances, and filter to obtain the first batch of perfluoropolyether acyl fluoride products;

[0041] Step 3, in a polymerization reaction kettle from which water has been removed, take 280 g of the first batch of perfluoropolyether acyl fluoride product in step 2, add 240 g of diluent Noah 7100, cool to -3°C and slowly introduce 680 g of hexafluoropropylene oxide, keep warm and react for 4 hours to obtain a second batch of mixture, heat to 70°C and distill under reduced pressure to remove the diluent, then heat to 110°C and distill to remove the solvent and low-boiling substances, filter to obtain a second batch of perfluoropolyether acyl fluoride product;

[0042] Step 4: In a polymerization reactor from which water has been removed, take 280 g of the second batch of perfluoropolyether acyl fluoride product in step 3, add 520 g of diluent Noah 7100, cool to -3 ° C and slowly introduce 760 g of hexafluoropropylene oxide, keep warm and react for 4 hours to obtain the third batch of mixture, heat to 70 ° C and distill under reduced pressure to evaporate the diluent, then heat to 110 ° C and distill to evaporate the solvent and low-boiling substances, filter to obtain the third batch of perfluoropolyether acyl fluoride product.

[0043] Example 2

[0044] A method for preparing perfluoropolyether acyl fluoride comprises the following preparation steps:

[0045] Step 1, preparation of the initiation system: under nitrogen protection, add 9g of catalyst KF, 1g of crown ether 15-crown-5 and 1g of solvent triethylene glycol dimethyl ether to a reaction kettle that has been dehydrated and dried, cool to -10°C, slowly introduce 1500g of hexafluoropropylene oxide, and keep the temperature for reaction for 3h to obtain the initiation system;

[0046] Step 2: Add 120 g of the initiator system prepared in step 1 and 240 g of diluent perfluoro-4-methyl-2-pentene into the polymerization reactor from which water has been removed, slowly introduce 360 ​​g of hexafluoropropylene oxide after cooling to 5° C., and keep the mixture warm for 4 hours to obtain the first batch of mixture, heat it to 40° C. and distill under reduced pressure, then heat it to 110° C. and distill, filter, and obtain the first batch of perfluoropolyether acyl fluoride products;

[0047] Step 3, in a polymerization reaction kettle from which water has been removed, take 200 g of the first batch of perfluoropolyether acyl fluoride product in step 2, add 80 g of diluent perfluoro-4-methyl-2-pentene, cool to 5°C and slowly introduce 400 g of hexafluoropropylene oxide, keep warm and react for 4 hours to obtain a second batch of mixture, heat to 40°C and distill under reduced pressure, then heat to 110°C and distill, filter to obtain a second batch of perfluoropolyether acyl fluoride product;

[0048] Step 4, in a polymerization reaction kettle from which water has been removed, take 200 g of the second batch of perfluoropolyether fluoride product in step 3, add 280 g of diluent perfluoro-4-methyl-2-pentene, cool to 5°C and slowly introduce 440 g of hexafluoropropylene oxide, keep the temperature for 4 hours to obtain the third batch of mixture, heat to 40°C and distill under reduced pressure, then heat to 110°C and distill, filter to obtain the third batch of perfluoropolyether fluoride product.

[0049] Example 3

[0050] A method for preparing perfluoropolyether acyl fluoride comprises the following preparation steps:

[0051] Step 1, preparation of the initiation system: under nitrogen protection, add 9g of catalyst KF, 1g of 12-crown-4 and 20g of solvent diethylene glycol diethyl ether into a reaction kettle that has been dehydrated and dried, cool to 0°C, slowly introduce 1g of hexafluoropropylene oxide, and keep the temperature for reaction for 3h to obtain the initiation system;

[0052] Step 2, add 320g of the initiation system prepared in step 1, 400g of diluent perfluoro-4-methyl-2-pentene and perfluorononene in a weight ratio of 1:1 to the polymerization reaction kettle from which water has been removed, slowly introduce 600g of hexafluoropropylene oxide after cooling to -10°C, and keep the mixture for 4h to obtain the first batch of mixture, heat it to 80°C for distillation under reduced pressure, then heat it to 110°C for distillation, filter it, and obtain the first batch of perfluoropolyether acyl fluoride products;

[0053] Step 3, in a polymerization reactor from which water has been removed, take 480 g of the first batch of perfluoropolyether acyl fluoride product in step 2, add 320 g of diluent perfluoro-4-methyl-2-pentene and perfluorononene, the weight ratio of perfluoro-4-methyl-2-pentene to perfluorononene is 1:1, cool to -10°C and slowly introduce 800 g of hexafluoropropylene oxide, keep warm and react for 4 hours to obtain a second batch of mixture, heat to 80°C and distill under reduced pressure, then heat to 110°C and distill, filter to obtain a second batch of perfluoropolyether acyl fluoride product;

[0054] Step 4, in a polymerization reaction kettle from which water has been removed, take 480 g of the second batch of perfluoropolyether fluoride products in step 3, add 600 g of diluent perfluoro-4-methyl-2-pentene and perfluorononene, the weight ratio of perfluoro-4-methyl-2-pentene to perfluorononene is 1:1, cool to -10°C and slowly introduce 880 g of hexafluoropropylene oxide, keep the temperature for 4 hours to obtain the third batch of mixture, heat to 80°C and distill under reduced pressure, then heat to 110°C and distill, filter to obtain the third batch of perfluoropolyether fluoride products.

[0055] Example 4

[0056] A method for preparing perfluoropolyether acyl fluoride, which is different from that in Example 1, the catalyst in step one is 18-crown-6; step one, preparation of an initiation system: under nitrogen protection, 8 g of catalyst 18-crown-6 and 16 g of solvent tetraethylene glycol dimethyl ether are added to a reaction kettle that has been dehydrated and dried, and 110 g of hexafluoropropylene oxide is slowly introduced after the temperature is reduced to -5°C, and the reaction is kept warm for 3 hours to obtain an initiation system.

[0057] Example 5

[0058] A method for preparing perfluoropolyether acyl fluoride, which is different from that in Example 1, the catalyst in step 1 is CsF; step 1, preparation of an initiation system: under nitrogen protection, 8 g of catalyst RbF and 16 g of solvent tetraethylene glycol dimethyl ether are added to a reaction kettle that has been dehydrated and dried, and 110 g of hexafluoropropylene oxide is slowly introduced after the temperature is reduced to -5°C, and the reaction is kept warm for 3 hours to obtain an initiation system.

[0059] Example 6

[0060] A method for preparing perfluoropolyether acyl fluoride, which is different from that in Example 1, the solvent in step 1 is triethylene glycol dimethyl ether and ethylene glycol diethyl ether; step 1, preparation of an initiation system: under nitrogen protection, in a reaction kettle that has been dehydrated and dried, 7g of catalyst KF, 1g of 18-crown ether-6 and 16g of solvent triethylene glycol dimethyl ether and ethylene glycol diethyl ether are added, the weight ratio of triethylene glycol dimethyl ether to ethylene glycol diethyl ether is 1:1, and after cooling to -5°C, 110g of hexafluoropropylene oxide is slowly introduced, and the reaction is kept warm for 3h to obtain an initiation system.

[0061] Example 7

[0062] A method for preparing perfluoropolyether acyl fluoride, which is different from that in Example 1, the solvent in step 1 is tetraethylene glycol dimethyl ether and diethylene glycol diethyl ether; step 1, preparation of an initiation system: under nitrogen protection, a catalyst KF7g, 1g 18-crown ether-6 and a solvent tetraethylene glycol dimethyl ether and diethylene glycol diethyl ether 16g, the weight ratio of tetraethylene glycol dimethyl ether to diethylene glycol diethyl ether being 1:1, are added to a reaction kettle which has been dehydrated and dried, and 110g of hexafluoropropylene oxide is slowly introduced after the temperature is reduced to -5°C, and the reaction is kept warm for 3h to obtain an initiation system.

[0063] Example 8

[0064] A method for preparing perfluoropolyether acyl fluoride, which is different from that of Example 1 in that the diluent in step 2, step 3 and step 4 is Noah 7000A.

[0065] Example 9

[0066] A method for preparing perfluoropolyether acyl fluoride, which is different from that of Example 1 in that the diluent in step 2, step 3 and step 4 is Noah 7200.

[0067] Example 10

[0068] A method for preparing perfluoropolyether acyl fluoride, which is different from that of Example 1 in that the diluent in step 2, step 3 and step 4 is Noah 7300.

[0069] Embodiment 11

[0070] A method for preparing perfluoropolyether acyl fluoride, which is different from that of Example 1 in that the diluent in step 2, step 3 and step 4 is perfluorononene.

[0071] Example 12

[0072] A method for preparing perfluoropolyether acyl fluoride, which is different from Example 2 in that, in step 2, 80 g of the initiator system prepared in step 1 and 200 g of diluent perfluoro-4-methyl-2-pentene are added to a polymerization reaction kettle from which water has been removed, 320 g of hexafluoropropylene oxide is slowly introduced after the temperature is reduced to 5°C, and the mixture is kept warm for 4 hours to obtain the first batch of the mixture, which is then heated to 40°C for reduced pressure distillation, then heated to 110°C for distillation, and filtered to obtain the first batch of perfluoropolyether acyl fluoride products.

[0073] Embodiment 13

[0074] A method for preparing perfluoropolyether acyl fluoride, which is different from Example 3 in that, in step 1, 160 g of the initiator system prepared in step 1, 40 g of diluent perfluoro-4-methyl-2-pentene and perfluorononene, wherein the weight ratio of perfluoro-4-methyl-2-pentene to perfluorononene is 1:1, the temperature is lowered to -10°C and then 360 g of hexafluoropropylene oxide is slowly introduced, the mixture is kept warm for 4 hours to obtain the first batch of the mixture, the mixture is heated to 80°C and distilled under reduced pressure, and then heated to 110°C for distillation, and filtered to obtain the first batch of perfluoropolyether acyl fluoride products.

[0075] Embodiment 14

[0076] A method for preparing perfluoropolyether acyl fluoride, which is different from Example 2 in that, in step 3, in a polymerization reaction kettle from which water has been removed, 160 g of the first batch of perfluoropolyether acyl fluoride products in step 2 are taken, 40 g of diluent perfluoro-4-methyl-2-pentene is added, the mixture is cooled to 5°C and then 360 g of hexafluoropropylene oxide is slowly introduced, and the mixture is kept warm for 4 hours to obtain a second batch of the mixture, the mixture is heated to 40°C and distilled under reduced pressure, and then heated to 110°C for distillation, and filtered to obtain a second batch of perfluoropolyether acyl fluoride products.

[0077] Embodiment 15

[0078] A method for preparing perfluoropolyether acyl fluoride, which is different from Example 3 in that, in step 3, in a polymerization reactor from which water has been removed, 520 g of the first batch of perfluoropolyether acyl fluoride products in step 2 are taken, 360 g of diluent perfluoro-4-methyl-2-pentene and perfluorononene are added, and the weight ratio of perfluoro-4-methyl-2-pentene to perfluorononene is 1:1, and after cooling to -10°C, 840 g of hexafluoropropylene oxide is slowly introduced, and the mixture is kept warm for 4 hours to obtain a second batch of the mixture, which is heated to 80°C for reduced pressure distillation, then heated to 110°C for distillation, and filtered to obtain a second batch of perfluoropolyether acyl fluoride products.

[0079] Example 16

[0080] A method for preparing perfluoropolyether acyl fluoride, which is different from Example 2 in that, in step 4, 160 g of the second batch of perfluoropolyether acyl fluoride products in step 3 are taken into a polymerization reaction kettle from which water has been removed, 240 g of perfluoro-4-methyl-2-pentene as a diluent is added, 400 g of hexafluoropropylene oxide is slowly introduced after the temperature is reduced to 5°C, and the mixture is kept warm for 4 hours to obtain a third batch of the mixture, the mixture is heated to 40°C and distilled under reduced pressure, and then heated to 110°C for distillation, and filtered to obtain a third batch of perfluoropolyether acyl fluoride products.

[0081] Embodiment 17

[0082] A method for preparing perfluoropolyether acyl fluoride, which is different from Example 3 in that, in step 4, 520 g of the second batch of perfluoropolyether acyl fluoride products in step 3 are taken into a polymerization reactor from which water has been removed, 640 g of diluent perfluoro-4-methyl-2-pentene and perfluorononene are added, and the weight ratio of perfluoro-4-methyl-2-pentene to perfluorononene is 1:1, and 920 g of hexafluoropropylene oxide is slowly introduced after cooling to -10°C, and the mixture is kept warm for 4 hours to obtain a third batch of the mixture, which is heated to 80°C for reduced pressure distillation, then heated to 110°C for distillation, and filtered to obtain a third batch of perfluoropolyether acyl fluoride products.

[0083] Comparative Example

[0084] Comparative Example 1

[0085] A method for preparing perfluoropolyether acyl fluoride, which is different from that of Example 1 in that the diluent in step 2, step 3 and step 4 is hexafluoropropylene.

[0086] Comparative Example 2

[0087] A method for preparing perfluoropolyether acyl fluoride, which is different from Example 1 in that the catalyst in step 1 is KF.

[0088] Comparative Example 3

[0089] A method for preparing perfluoropolyether acyl fluoride, which is different from that of Example 1 in that the catalyst in step 1 is CsF.

[0090] Comparative Example 4

[0091] A method for preparing perfluoropolyether acyl fluoride comprises the following preparation steps:

[0092] Step 1, preparation of the initiation system: under nitrogen protection, add 3.1 g of catalyst CsF2 and 36 g of solvent tetraethylene glycol dimethyl ether to a reaction kettle that has been dehydrated and dried, cool to -15°C, slowly introduce 210 g of hexafluoropropylene oxide, and keep the temperature for reaction for 3 hours to obtain an initiation system;

[0093] Step 2: Add 50 g of the initiator system prepared in step 1, 2500 g of hexafluoropropylene diluent, 100 g of tetraethylene glycol dimethyl ether solvent, and 3 g of CsF3 catalyst to the polymerization reactor from which water has been removed; slowly introduce 6000 g of hexafluoropropylene oxide after cooling to -10°C; keep the reaction warm for 4 hours; heat to 70°C and distill under reduced pressure; then heat to 110°C and distill; filter to obtain a perfluoropolyether acyl fluoride product.

[0094] Table 1 Experimental test results

[0095]

[0096]

[0097]

[0098] As can be seen from Table 1, by adjusting the ratio, dosage and reaction temperature of each component in each batch of polymerization, the molecular weight of perfluoropolyether acyl fluoride can be controlled, and a perfluoropolyether acyl fluoride product with a narrower molecular weight distribution can be prepared.

[0099] In conjunction with Example 1 and Comparative Examples 1-4 and in conjunction with Table 1, it can be seen that hexafluoropropylene is not easy to be all liquefied into liquid form, so hexafluoropropylene acts as a diluent, which will affect polymerization to a certain extent, causing the final product average molecular weight to be low. Only KF is used as catalyst, and the polymerization effect is poor, and the hexafluoropropylene oxide that does not participate in the reaction and the oligomer generated are more, further illustrating that KF and crown ether composition performance are more excellent, and crown ether can be complexed with metal cations, so as to promote the release of fluoride ions in fluoride salts, which is conducive to the occurrence of polymerization. Using CsF as catalyst, the polymerization effect is close to the mixture effect of KF and 18-crown ether-6, and because the crown ether usage amount is small, so from the cost point of view, using KF and 18-crown ether-6 as catalyst is more economical than using CsF, and one-pot synthesis mode is difficult to obtain the perfluoropolyether acyl fluoride with narrower molecules.

[0100] Table 2 Number of times the diluent Noah 7100 is reused

[0101]

[0102] As can be seen from Table 2, the diluent Noah 7100 evaporated by vacuum distillation in the three batches of polymerization can be uniformly recovered and continued to be used as a diluent for the next cycle polymerization reaction, and the uniformly recovered diluent Noah 7100 can be reused for 50 times in succession, and the yield and molecular weight of each batch of perfluoropolyether acyl fluoride have not changed significantly. Compared with hexafluoropropylene as a diluent, hexafluoropropylene as a diluent requires a sufficiently low temperature to be liquefied to play a role. The use of a fluorine-containing high-boiling point diluent increases the reaction temperature during the reaction, thereby reducing energy consumption and the product polymerization degree does not change significantly; the reaction process is mild, the discharging process is safe, and there is no high pressure in the kettle when the temperature is increased when hexafluoropropylene is used as a diluent, which poses a certain safety hazard.

[0103] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for preparing perfluoropolyether acyl fluoride, characterized in that: The method comprises the following preparation steps: Step 1, preparation of the initiation system: under nitrogen protection, firstly add a catalyst and a solvent into a reaction kettle, cool it down, then introduce hexafluoropropylene oxide, and react at a constant temperature to obtain an initiation system; Step 2, adding the initiator system and diluent prepared in step 1 into the polymerization reaction kettle, cooling down, then introducing hexafluoropropylene oxide, reacting at a constant temperature to obtain the first batch of mixture, distilling under reduced pressure, distilling at a higher temperature, filtering, and obtaining the first batch of perfluoropolyether acyl fluoride products; Step 3, taking the first batch of perfluoropolyether acyl fluoride products in step 2, adding a diluent, cooling, then introducing hexafluoropropylene oxide, reacting at a constant temperature to obtain a second batch of mixture, distilling under reduced pressure, distilling at a higher temperature, filtering, and obtaining a second batch of perfluoropolyether acyl fluoride products; Step 4, taking the second batch of perfluoropolyether acyl fluoride products in step 3, adding a diluent, cooling, then introducing hexafluoropropylene oxide, reacting at a constant temperature to obtain a third batch of mixture, distilling under reduced pressure, distilling at a higher temperature, filtering, and obtaining a third batch of perfluoropolyether acyl fluoride products; The diluent in step 2, step 3 and step 4 is one or more of Noah 7000A, Noah 7100, Noah 7200, Noah 7300, perfluoro-4-methyl-2-pentene and perfluorononene produced by Zhejiang Noah Fluorine Chemical Co., Ltd.; Wherein, in the step 2, the weight ratio of the initiator system, the diluent and the hexafluoropropylene oxide is 3-8:6-10:9-15; In the step 3, the weight ratio of the first batch of perfluoropolyether acyl fluoride product, diluent and hexafluoropropylene oxide is 5-12:2-8:10-20; In the step 4, the weight ratio of the second batch of perfluoropolyether acyl fluoride product, the diluent and hexafluoropropylene oxide is 5-12:7-15:11-22; The catalyst in step 1 is alkali metal fluoride and crown ether.

2. The method for preparing a perfluoropolyether acyl fluoride according to claim 1, characterized in that: In the step 1, under nitrogen protection, firstly, a catalyst and a solvent are added to a reaction kettle, the temperature is lowered to -10°C to 0°C, and then hexafluoropropylene oxide is introduced to react at a constant temperature to obtain an initiation system.

3. The method for preparing perfluoropolyether acyl fluoride according to claim 1, characterized in that: In the steps 2, 3 and 4, the temperature is lowered to -10°C to 5°C, and the vacuum distillation temperature is 40°C to 80°C.

4. A perfluoropolyether acyl fluoride product, prepared by the preparation method of a perfluoropolyether acyl fluoride according to any one of claims 1 to 3.

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