Fluorine-containing polyether carboxylic acid, and preparation method and application thereof

Abstract

The application belongs to the field of fluorine-containing compounds, and particularly relates to a fluorine-containing polyether carboxylic acid and a preparation method and application thereof. The preparation method of the fluorine-containing polyether carboxylic acid comprises the following steps: 1) preparing perfluoroisobutyloxy propionyl fluoride by taking perfluoroisobutyryl fluoride as a raw material; 2) preparing perfluoroisobutyl vinyl ether by taking the perfluoroisobutyloxy propionyl fluoride as a raw material; 3) preparing perfluoroisobutyl alkoxy ethyl ether by taking the perfluoroisobutyl vinyl ether as a raw material; 4) preparing a fluorine-containing polyether ester by taking the perfluoroisobutyl alkoxy ethyl ether as a raw material; 5) preparing a fluorine-containing polyether carboxylic acid salt by taking the fluorine-containing polyether ester as a raw material; and 6) preparing the fluorine-containing polyether carboxylic acid by taking the fluorine-containing polyether carboxylic acid salt as a raw material. The technical scheme of the application finally obtains the fluorine-containing polyether carboxylic acid by taking the perfluoroisobutyryl fluoride as a starting raw material, the reaction yield of each step is high, the cost is low, the raw material is easy to obtain, the reaction condition has low requirement on equipment, the product is easy to handle, and the fluorine-containing polyether carboxylic acid product obtained finally has low fluorine ion content.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fluorine-containing compounds, and particularly relates to a fluorine-containing polyether carboxylic acid and a preparation method and application thereof. BACKGROUND

[0002] Fluorine-containing surfactants are often used as emulsifiers for producing fluorine-containing polymers, and are usually prepared from perfluoro or fluorine-containing carboxylic acids further configured into perfluoro or fluorine-containing carboxylic acid salt aqueous solutions. Since perfluorooctanoic acid and its ammonium salt (PFOA) can persist in the natural environment and human body, they will accumulate in the nature and human body over time, and have certain harmfulness to the environment and human health. At present, laws and regulations have been issued in China and many countries abroad to prohibit the production and use of PFOA to different extents.

[0003] In recent years, domestic and foreign enterprises have been committed to the research and application of PFOA substitutes, and the research focus of related substitutes is around two types of short-chain perfluoroalkyl compounds with C4-C6 and perfluoroalkyl ethers containing functional groups. The fluorine-containing surfactants prepared by using short-chain perfluoroalkyl compounds have deficiencies in performance, and are still difficult to degrade in the environment. Perfluoroalkyl ether substances are similar in structure to short-chain perfluoroalkyl substances, but the main chain contains ether bonds, and the oxygen atoms make the original rigid fluorocarbon bond have better flexibility, and the fluorine atoms have strong electron-withdrawing effect. By preparing perfluoroalkyl ether carboxylic acid and its ammonium salt, it can be used as an emulsifier. Such substances neither use PFOA for synthesis nor contain or degrade PFOA, and have good safety, but the rigidity is insufficient compared with PFOA.

[0004] At present, perfluoro polyether carboxylic acid is mainly prepared from K-type or Y-type perfluoro polyether intermediates. The K-type perfluoro polyether adopts hexafluoroepoxy propane as a raw material, and HFPO dimers are prepared by an anionic polymerization method, and further prepared by a multi-step process to obtain HFPO dimer carboxylic acid, which has a high cost. The Y-type perfluoro polyether adopts hexafluoropropylene as a raw material, and polyether acyl fluoride intermediates are obtained by a photo-oxidation polymerization method, and further prepared by a multi-step process to obtain perfluoro polyether carboxylic acid. The product has a wide molecular weight distribution, and it is difficult to stably control the molecular weight to be low, and the polymerization unit is complex. SUMMARY

[0005] The present application aims to overcome the shortcomings in the prior art, and provides a fluorine-containing polyether carboxylic acid and a preparation method and application thereof.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of a fluorine-containing polyether carboxylic acid, comprising the following steps:

[0008] 1) perfluoroisobutyryl fluoride is used as a raw material to prepare perfluoroisobutyryl fluoride as shown in formula (I);

[0009]

[0010] 2) perfluoroisobutyl vinyl ether is prepared from perfluoroisobutyryl fluoride as shown in formula (II);

[0011]

[0012] 3) perfluoroisobutyl alkoxy ethyl ether is prepared from perfluoroisobutyl vinyl ether as shown in formula (III);

[0013]

[0014] wherein R is an alkyl group with carbon number < 6;

[0015] 4) fluorine-containing polyether ester is prepared from perfluoroisobutyl alkoxy ethyl ether as shown in formula (IV);

[0016]

[0017] 5) fluorine-containing polyether carboxylate is prepared from fluorine-containing polyether methyl ester as shown in formula (V);

[0018]

[0019] The carboxylate in formula (V) can be K salt, Na salt, Li salt, ammonium salt, etc.

[0020] 6) fluorine-containing polyether carboxylic acid is prepared from fluorine-containing polyether carboxylate as shown in formula (VI):

[0021]

[0022] The specific steps of step 1) are: under the condition of inert gas, a solvent and a catalyst are added to the reactor, and the raw material perfluoroisobutyryl fluoride is introduced; after the target amount of perfluoroisobutyryl fluoride is introduced, hexafluoropropylene oxide is continuously introduced, the reaction temperature is controlled, and after the reaction is completed, the target product is separated.

[0023] The solvent is at least one of diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, benzonitrile, tetrahydrofuran, or sulfolane; the catalyst is at least one of lithium fluoride, sodium fluoride, potassium fluoride, or cesium fluoride; and the reaction temperature is -20℃ to 50℃.

[0024] The specific steps of step 2) are: the reactor is filled with carbonate, heated to 200-300℃, and then perfluoroisobutyryl fluoride is introduced, the introduction speed is controlled at 100-500g / h, and after cooling, perfluoroisobutyl vinyl ether is obtained.

[0025] The specific steps of step 3) are: adding sodium alcoholate and a corresponding alcohol solution into a reactor, then adding perfluoroisobutyl vinyl ether into the reactor dropwise, controlling the reaction temperature to be-5 DEG C to 10 DEG C, and continuing to stir for 2-6 hours after the dropwise addition is completed; after the reaction is completed, separating the fluorine phase from the water phase to obtain perfluoroisobutyl alkoxy ethyl ether.

[0026] The specific steps of step 4) are: after adding the raw material perfluoroisobutyl alkoxy ethyl ether into a reactor, adding concentrated sulfuric acid into the reactor dropwise, reacting at room temperature, separating the water phase and the fluorine phase after the reaction is completed, washing the separated fluorine phase with NaHCO3 aqueous solution, then separating the water phase and the fluorine phase, drying the obtained fluorine phase with a desiccant to obtain a crude fluorine-containing polyether ester product, and then obtaining the fluorine-containing polyether ester through rectification.

[0027] The specific steps of step 5) are: adding the fluorine-containing polyether ester into a lye, and obtaining a fluorine-containing polyether carboxylate after reacting at 50-70 DEG C; the lye is an aqueous solution of sodium hydroxide or potassium hydroxide.

[0028] The specific steps of step 6) are: adding the fluorine-containing polyether carboxylate and concentrated sulfuric acid into a reactor, and obtaining a fluorine-containing polyether carboxylic acid after reacting at 40 DEG C-60 DEG C, separating the fluorine phase from the concentrated sulfuric acid, and distilling the fluorine phase under reduced pressure.

[0029] The application further comprises a fluorine-containing polyether carboxylic acid obtained by the preparation method.

[0030] The application further comprises an application of the fluorine-containing polyether carboxylic acid, which is applied to an emulsifier, and is appropriately added in a fluorine-containing polymer production process by being configured as an aqueous solution of the fluorine-containing polyether carboxylate.

[0031] Compared with the prior art, the application has the following beneficial effects:

[0032] The technical scheme of the application uses perfluoroisobutyryl fluoride as a starting material to finally obtain a fluorine-containing polyether carboxylic acid through reactions, each reaction has a high yield, the cost is low, the raw material is easy to obtain, the reaction conditions have low requirements on equipment, the product is easy to handle, the fluorine ion content of the finally obtained fluorine-containing polyether carboxylic acid product is low, the obtained fluorine-containing polyether carboxylic acid has rigidity and hydrophobicity of a fluorine-containing side chain on the basis of retaining an ether bond, therefore, the main chain has hydrogen atoms, and the environmental degradability is improved, and the fluorine-containing polyether carboxylic acid has a good application prospect, and is appropriately added in a fluorine-containing polymer production process by being configured as an aqueous solution of the fluorine-containing polyether carboxylate through a conventional method. DETAILED DESCRIPTION

[0033] In order for those skilled in the art to better understand the technical scheme of the application, the application is further described in detail below with reference to examples.

[0034] Example 1

[0035] A method for preparing a fluorine-containing polyether carboxylic acid, comprising the following steps:

[0036] 1) Preparation of perfluoroisobutyloxypropionyl fluoride intermediate: (1) A 5-liter reaction kettle was heated and vacuumed, the temperature was controlled below 100 degrees, the heating time was 8 hours, then the system was naturally cooled to room temperature after purging with nitrogen. (2) The solvent was diethylene glycol dimethyl ether, the catalyst was cesium fluoride, the raw material perfluoroisobutyryl fluoride gas was introduced, the gas flow rate was controlled at 1000-1500 g / h, the reaction temperature in the reaction system was controlled at -20-0°C, and the reaction pressure was normal pressure. (3) After 2 kg of gas was introduced, the introduction of perfluoroisobutyryl fluoride gas was stopped, and the introduction of raw material hexafluoropropylene oxide gas was started, the gas flow rate was controlled at 5-20 g / h, the reaction temperature in the reaction system was controlled at -20-50°C, the reaction pressure was normal pressure, and the reaction was continuously carried out. (4) After 1.5 kg of gas was introduced, the introduction of raw material hexafluoropropylene oxide gas was stopped, and the system was naturally restored to room temperature. The crude product of acyl fluoride was separated, and the yield was 95.6%.

[0037] It should be noted that the solvent in step 1) can be replaced with tetraethylene glycol dimethyl ether, benzonitrile, tetrahydrofuran, or sulfolane, and the catalyst can be replaced with lithium fluoride, sodium fluoride, or potassium fluoride. By adjusting different solvents and catalysts, the yield varies slightly, all within 92-96%.

[0038] 2) Preparation of perfluoroisobutyl vinyl ether: (1) A tubular reactor was filled with sodium carbonate solid and heated to 200°C. (2) 1 kg of acyl fluoride intermediate was introduced into the tubular reactor, the introduction speed was controlled at 100-500 g / h, and the reaction temperature was 200-300°C. Perfluoroisobutyl vinyl ether product was collected after cooling, and the yield was 95%.

[0039] 3) Preparation of perfluoroisobutyl methoxyethyl ether: (1) In a 1L flask, 27g of sodium methoxide and 240g of methanol were added. (2) Perfluoroisobutyl vinyl ether 362g was added through a constant pressure dropping funnel at a speed of 90g / h, and the reaction temperature was 0°C. After the addition was completed, stirring was carried out for 4h. (3) The fluorine phase and the methanol phase were separated, the fluorine phase was washed with two volumes of water, the fluorine phase and the water phase were separated, and the alkali metal sulfate was dried to obtain perfluoroisobutyl methoxyethyl ether product, and the yield was 95%.

[0040] 4) Preparation of fluorine-containing polyether methyl ester: (1) In a 250mL flask, 50g of hydrofluoroether was added, 70mL of concentrated sulfuric acid was added through a constant pressure dropping funnel in 15 minutes, and stirring was carried out at room temperature for 2h. (2) The fluorine phase and the concentrated sulfuric acid were separated, the fluorine phase was washed with two volumes of 5% NaHCO3 aqueous solution, the fluorine phase and the water phase were separated, and the alkali metal sulfate was dried to obtain crude fluorine-containing polyether methyl ester product, and the yield was 92%. (3) Fluorine-containing polyether methyl ester product was obtained by rectification.

[0041] 5) Preparation of fluorine-containing polyether carboxylate: (1) In a 250 mL flask, 17 grams of potassium hydroxide, 100 grams of deionized water, stirring until the solid is dissolved. (2) Add 100 grams of fluorine-containing polyether methyl ester to the flask, stir at 50-70°C for 2 hours. (3) Remove the solvent and unreacted fluorine-containing polyether methyl ester by distillation under reduced pressure to obtain fluorine-containing polyether carboxylate with a yield of 98%.

[0042] 6) Preparation of fluorine-containing polyether carboxylic acid: In a 250 mL flask, add 100 grams of fluorine-containing polyether carboxylate and 100 grams of concentrated sulfuric acid, stir at 40-60°C for 2 hours, then separate the fluorine phase and concentrated sulfuric acid, and distill under reduced pressure to obtain fluorine-containing polyether carboxylic acid with a yield of 95%, the product contains 0.02% water and no HF.

[0043] The application of fluorine-containing polyether carboxylic acid specifically includes the following steps: saltification of fluorine-containing polyether carboxylic acid, addition of fluorine-containing polyether carboxylic acid to various ammonia or alkali solutions for neutralization, saltification, and preparation of fluorine-containing polyether carboxylate solutions with different concentrations, i.e. fluorine-containing polyether carboxylic acid emulsifiers;

[0044] In this application, ammonium salt is used as an example for illustrative purposes.

[0045] The obtained fluorine-containing polyether carboxylic acid emulsifier is subjected to performance testing, and the surface tension and critical micelle concentration are measured by a full-automatic surface tension meter. The test results are shown in Table 1.

[0046] Table 1

[0047]

[0048] The obtained fluorine-containing polyether carboxylic acid is used as an emulsifier for the polymerization of fluorine-containing polymers. The specific process is as follows: 3 liters of deionized water are injected into a 5-liter pressure-resistant reaction kettle, and the obtained fluorine-containing polyether carboxylic acid ammonium salt CF3CF(CF3)CF2OCFHCOONH4 + 1 gram, the reaction kettle is repeatedly purged with high-purity nitrogen gas until the oxygen content in the reaction kettle is less than 30 ppm, the oxygen content is qualified, the reaction kettle is heated to 20°C, 4 grams of perfluoropropyl vinyl ether are vacuumed in, 1 mL of an oxidation-reduction initiation system composed of ammonia, potassium persulfate and sodium sulfite is added, four fluorine ethylene is introduced into the kettle until the pressure of the reaction kettle is 0.8 MPa, and the stirring is started to begin the reaction. During the reaction, the reaction temperature is maintained at -5°C to 5°C, and when the reaction kettle pressure is constant, the stirring is continued for 2 hours, and the reaction is stopped. After the reaction is completed, the unreacted tetrafluoroethylene monomer is recovered, the pressure in the reaction kettle is removed, and a modified polytetrafluoroethylene emulsion with a solid content of 61% is obtained, with a molecular weight of 15000. After treatment, coagulation, washing and drying, a modified polytetrafluoroethylene dispersion resin is obtained.

[0049] Comparative Example 1

[0050] The obtained perfluoropolyether carboxylic acid is used as an emulsifier in the polymerization of a fluorine-containing polymer. Specifically, 3 liters of deionized water is injected into a 5-liter pressure-resistant reaction kettle, and the perfluoropolyether carboxylic acid ammonium salt of Comparative Example 1, CF3CF2CF2OCF(CF3)COONH4 + 1 gram, the reaction kettle is repeatedly purged with high-purity nitrogen until the oxygen content in the reaction kettle is less than 30 ppm, and after the oxygen content is qualified, the reaction kettle is warmed to 20℃, 4 grams of perfluoropropyl vinyl ether is vacuum-sucked in, and an oxidation-reduction initiation system composed of 1 mL of ammonia water, potassium persulfate and sodium sulfite is added, and tetrafluoroethylene is introduced into the kettle until the pressure in the reaction kettle is 0.8 MPa, and the stirring is started to begin the reaction. During the reaction, the reaction temperature is maintained at -5℃ to 5℃, and when the pressure in the reaction kettle is constant, the stirring is continued for 2 hours, and the reaction is stopped. After the reaction is completed, the unreacted tetrafluoroethylene monomer is recovered, the pressure in the reaction kettle is removed, and a modified polytetrafluoroethylene emulsion with a solid content of 60% is obtained, and the molecular weight is 8500. After treatment, coagulation, washing and drying, a modified polytetrafluoroethylene dispersion resin is obtained.

[0051] As can be seen from the above, the technical scheme of the present application uses perfluoroisobutyryl fluoride as a starting material to ultimately obtain a fluorine-containing polyether carboxylic acid, each step has a high reaction yield, the cost is low, the raw material is easy to obtain, the reaction conditions have low requirements on the equipment, the product is easy to handle, and the fluorine ion content of the final fluorine-containing polyether carboxylic acid product is low; the obtained fluorine-containing polyether carboxylic acid has good application prospects due to the increase in the rigidity and hydrophobicity of the fluorine-containing side chain and the increase in the hydrogen atoms in the main chain, which can improve environmental degradability. The fluorine-containing polyether carboxylic acid is configured into an aqueous fluorine-containing polyether carboxylic acid salt solution by using a conventional method, and can be appropriately added during the production of a fluorine-containing polymer. The production process of the fluorine-containing polymer is a free radical polymerization of perfluoro or fluorine-containing monomers in an aqueous emulsion in the presence of an emulsifier, and the initiator of the polymerization process is usually a water-soluble peroxide. The fluorine-containing polyether carboxylic acid prepared based on the technical scheme of the present application is used to configure an aqueous fluorine-containing polyether carboxylic acid salt solution, which provides a hydrophobic unit from the fluorine-containing polyether structure and a hydrophilic unit from the carboxylic acid salt. Compared with ammonium perfluorooctanoate, the environmental degradability is increased, the environmental and health hazards are reduced, and compared with K-type or Y-type perfluoropolyether, the perfluoroisobutyl unit is increased, the hydrophobicity is improved, and the emulsifying effect is better.

[0052] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. A method for preparing a fluorinated polyether carboxylic acid, characterized in that: The steps include: 1) Using perfluoroisobutyryl fluoride as a raw material, perfluoroisobutoxypropionyl fluoride is prepared as shown in formula (I); （I）； 2) Perfluoroisobutyl vinyl ether is prepared using perfluoroisobutoxypropionyl fluoride as a raw material as shown in formula (II); (II) 3) using perfluoroisobutyl vinyl ether as a raw material to prepare perfluoroisobutyl alkoxyethyl ether as shown in formula (III); (III); Wherein, R is an alkyl group having less than 6 carbon atoms; 4) using perfluoroisobutyl alkoxyethyl ether as a raw material to prepare a fluorinated polyether ester as shown in formula (IV); (IV); 5) preparing a fluorinated polyether carboxylate using a fluorinated polyether ester as a raw material as shown in formula (V); （V）； 6) Using fluorinated polyether carboxylate as raw material, a fluorinated polyether carboxylic acid is prepared as shown in formula (VI): (WE).

2. The method for preparing fluorinated polyether carboxylic acid according to claim 1, wherein The specific steps of step 1) are: under inert gas conditions, adding a solvent and a catalyst into a reactor, and introducing the raw material perfluoroisobutyryl fluoride; after the target amount of perfluoroisobutyryl fluoride is introduced, hexafluoropropylene oxide is continued to be introduced, the reaction temperature is controlled, and after the reaction is completed, the target product is separated.

3. The method for preparing fluorinated polyether carboxylic acid according to claim 2, wherein: The solvent is at least one of diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, benzonitrile, tetrahydrofuran, or sulfolane; the catalyst is at least one of lithium fluoride, sodium fluoride, potassium fluoride, or cesium fluoride; and the reaction temperature is between -20°C and 50°C.

4. The method for preparing fluorinated polyether carboxylic acid according to claim 1, wherein The specific steps of step 2) are as follows: filling the reactor with carbonate, heating it to 200-300° C., introducing perfluoroisobutoxypropionyl fluoride at a rate of 100-500 g / h, and cooling it to obtain perfluoroisobutyl vinyl ether.

5. The method for preparing fluorinated polyether carboxylic acid according to claim 1, wherein The specific steps of step 3) are as follows: sodium alcoholate and the corresponding alcohol solution are added to the reactor, and then perfluoroisobutyl vinyl ether is added dropwise to the reactor, the reaction temperature is controlled to be between -5°C and 10°C, and stirring is continued for 2-6 hours after the addition is completed; after the reaction is completed, the fluorine phase and the aqueous phase are separated to obtain perfluoroisobutyl alkoxyethyl ether.

6. The method for preparing fluorinated polyether carboxylic acid according to claim 1, wherein: The specific steps of step 4) are as follows: after adding the raw material perfluoroisobutyl alkoxyethyl ether into the reactor, concentrated sulfuric acid is added dropwise into the reactor, reacting at room temperature, separating the aqueous phase and the fluorine phase after the reaction is completed, adding NaHCO3 aqueous solution to the separated fluorine phase for washing, and then separating the aqueous phase and the fluorine phase; drying the obtained fluorine phase with a desiccant to obtain a crude fluorine-containing polyether ester product; and then distilling to obtain a fluorine-containing polyether ester.

7. The method for preparing fluorinated polyether carboxylic acid according to claim 1, wherein: The specific steps of step 5) are: adding fluorinated polyether ester to alkaline solution, reacting at 50-70° C. to obtain fluorinated polyether carboxylate; the alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide.

8. The method for preparing fluorinated polyether carboxylic acid according to claim 1, wherein The specific steps of step 6) are: adding fluorinated polyether carboxylate and concentrated sulfuric acid into a reactor, reacting at 40°C-60°C, separating the fluorinated phase and the concentrated sulfuric acid, and distilling the fluorinated phase under reduced pressure to obtain the fluorinated polyether carboxylic acid.

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