Process for separating mono- and dicarboxylate end group perfluoropolyethers by liquid-liquid extraction
The liquid-liquid extraction technique was used to separate monocarboxylate-terminated perfluoropolyethers and dicarboxylate-terminated perfluoropolyethers, solving the problems of cumbersome separation methods and low yields in existing technologies, and realizing the preparation of high-purity, high-yield monofunctional perfluoropolyethers.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2022-06-23
- Publication Date
- 2026-07-03
AI Technical Summary
Existing techniques for separating monocarboxylate-terminated perfluoropolyethers and dicarboxylate-terminated perfluoropolyethers containing mixtures are cumbersome, consume large amounts of solvent, and have low yields, making it impossible to efficiently prepare high-purity monofunctional perfluoropolyether compounds.
Liquid-liquid extraction technology is used, which involves contact mixing of light and heavy phase solvents, followed by separation after extraction equilibrium. The light phase yields high-purity monocarboxylate-terminated perfluoropolyether, while the heavy phase yields dicarboxylate-terminated perfluoropolyether. The solvent consists of a diluent and a polar solvent containing fluorine atoms, and the extraction temperature is between 10 and 70°C.
It achieves the separation of monocarboxylate-terminated perfluoropolyethers that is simple to operate, stable, low in cost, high in capacity, high in purity, and high in yield. The solvent is easy to recover, and the purity of the separated product is not less than 98%, and the yield is not less than 75%.
Abstract
Description
Technical Field
[0001] This invention relates to the field of separation technology for mono / bifunctionalized perfluoropolyether active compounds, specifically to a method for liquid-liquid extraction to separate monocarboxylate-terminated perfluoropolyethers and dicarboxylate-terminated perfluoropolyethers. Background Technology
[0002] Functionalized perfluoropolyether active materials (PFPE-AC) are perfluoropolyether polymers with active functional groups at their ends. The main chain of PFPE-AC contains only C, F, and O elements, thus exhibiting excellent thermal stability, chemical inertness, and low surface energy. Furthermore, the active end groups can be further modified, leading to their widespread use in the automotive industry, aerospace, microelectronics, chemical engineering, textile processing, and protective architectural coatings. However, functionalized perfluoropolyethers (PFPE-AC) are typically mixtures containing monofunctional and difunctional perfluoropolyethers, each with different properties. Therefore, enriching and purifying perfluoropolyethers with target functionalities is crucial for industrial applications. Currently, the most widely used PFPE-AC end groups are carboxylic acid groups. Monofunctional carboxyl perfluoropolyethers can be prepared as precursors for perfluoropolyethers with other end groups, such as alcohols, esters, and amides. These precursors can be further converted into perfluoropolyether derivatives (e.g., polyurethane derivatives, polyacrylate derivatives, silanized derivatives). The manufacturing process of monofunctional carboxyl perfluoropolyethers may result in mixing with non-functional / bifunctional perfluoropolyethers, and the introduction of impurities seriously affects subsequent processing and the performance of end products.
[0003] Currently, methods for separating mixtures mainly rely on physical methods such as physical / chemical adsorption and chromatography, with a few involving molecular distillation and chemical reactions. For example, patents CN104768623A and WO2014067981A1 use intermittent chromatography to separate mixtures containing inert perfluoropolyethers, monocarboxylic acid ester-based perfluoropolyethers, and diacid acid ester-based perfluoropolyethers to improve the average functionality of the PFPE carboxylic acid ester mixture. Silica gel is used as the adsorbent, requiring multiple adsorption and elution cycles. Daikin Industries, Ltd.'s patent application (CN105518054A) uses silica thin-layer chromatography to separate mixtures containing inert perfluoropolyethers, monocarboxylic acid ester-based perfluoropolyethers, and diacid acid ester-based perfluoropolyethers. This method is more complex, requiring multiple adsorption and elution cycles, and studies were conducted on different non-polar and polar mobile phases. Patents JP2015164908A and JP2017222732A report adsorption separation techniques for separating carboxylic acid compounds from a starting mixture containing nonfunctional compounds, monocarboxylic acid compounds, and dicarboxylic acid compounds with perfluoropolyether groups. Similarly, Shin-Etsu Chemical, in patent (EP2905298B1), also uses silica gel as an adsorbent to separate a mixture of inert perfluoropolyethers, monocarboxylic acid perfluoropolyethers, and diacid acid perfluoropolyethers, employing supercritical carbon dioxide as the mobile phase. Patent WO2014067981A1 uses an intermittent chromatographic method for purifying perfluoropolyether carboxylates, which can improve the average functionality of the perfluoropolyether carboxylates. This separation method contacts the perfluoropolyether mixture with a solid phase, obtaining high-functionality perfluoropolyether carboxylates by separating the solid and liquid phases. Patent JP2015164906A employs chromatographic techniques to extract single-terminal carboxyl-containing perfluoropolyether compounds from mixtures of single / double-terminal carboxyl-containing perfluoropolyethers. This method uses supercritical or subcritical carbon dioxide as the mobile phase and silica gel as the solid phase for chromatographic analysis. However, this separation method is cumbersome and cannot prepare large quantities of single-terminal carboxyl-containing perfluoropolyether compounds.
[0004] In summary, current methods for separating mixtures of perfluoropolyether carboxyl groups with different functionalities mainly rely on adsorption and chromatographic separation. However, these methods are quite cumbersome, requiring multiple adsorption and elution processes, resulting in high solvent consumption and low yields. Summary of the Invention
[0005] To address the aforementioned technical problems and shortcomings in the field, this invention provides a method for liquid-liquid extraction to separate monocarboxylate-terminated perfluoropolyethers and dicarboxylate-terminated perfluoropolyethers. This method is simple to operate, has a stable process, high production capacity, high purity, high yield, and low cost.
[0006] The specific technical solution is as follows:
[0007] A method for separating monocarboxylate-terminated perfluoropolyether and dicarboxylate-terminated perfluoropolyether by liquid-liquid extraction includes: contacting and mixing a mixture containing monocarboxylate-terminated perfluoropolyether and dicarboxylate-terminated perfluoropolyether with a light and heavy phase solvent; after extraction equilibrium, separating the two phases and removing the solvent (which can be done by distillation or other means); obtaining a high-purity monocarboxylate-terminated perfluoropolyether product from the heavy phase and obtaining a product containing dicarboxylate-terminated perfluoropolyether from the light phase.
[0008] The light phase solvent consists of a diluent and a polar solvent containing fluorine atoms; the diluent is one or more of sulfolane, dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, water, ethylene glycol, acetonitrile, acetic acid, ethanol, and methanol;
[0009] Heavy phase solvents consist of nonpolar solvents containing fluorine atoms and polar solvents containing fluorine atoms, or nonpolar solvents containing fluorine atoms and nonpolar solvents without fluorine atoms.
[0010] The boiling range of the light phase solvent described in this invention is 50–150°C, and the boiling range of the heavy phase solvent is 60–180°C.
[0011] In a preferred embodiment, the content of the monocarboxylate-terminated perfluoropolyether and the dicarboxylate-terminated perfluoropolyether in the mixture is 4 wt% to 96 wt%.
[0012] The monocarboxylate-terminated perfluoropolyether may have the structure shown in formula (I):
[0013] AR f1 -B1 (I)
[0014] The dicarboxylate-terminated perfluoropolyether may have the structure shown in formula (II):
[0015] B 21 -R f2 -B 22 (II)
[0016] In equations (I) and (II):
[0017] A is an F atom or a C1-C4 perfluorinated alkyl group (including straight chain and branched chain);
[0018] B1, B 21 B 22 All of them are carboxylate terminal functional groups and each is independently selected;
[0019] R f1 R f2 The perfluoropolyether backbones, with a number average molecular weight of 300–25,000, all satisfy the chemical structure shown in equation (3) below, and are independently selected:
[0020] -O(CF2O) a -(C2F4O) b -(C3F6O) c -(C4F8O) d - (III)
[0021] In equation (III): a, b, c, and d are each independently selected from integers from 0 to 300, and the sum of a, b, c, and d is greater than 3; the order of the above repeating units (CF2O), (C2F4O), (C3F6O), and (C4F8O) is arbitrary, and the repeating unit (C3F6O) includes one or more of the following structures: (CF2CF2CF2O), (CF2CF(CF3)O), and (CF(CF3)CF2O).
[0022] The carboxylate-terminated perfluoropolyether and the dicarboxylate-terminated perfluoropolyether can each have independently selected carboxylate-terminated functional groups, and their expressions all satisfy -CFXCOOM, wherein:
[0023] X is one of F, propenyl, methpropenyl, or a C1-C4 alkyl chain (including straight-chain alkyl and branched-chain alkyl) in which all or part of the hydrogen atoms are replaced by fluorine atoms, and M is Na. + K + 、Rb + or Cs + .
[0024] The preferred polar solvent containing fluorine atoms is one or more of the following: carboxylic acids, ketones, and alcohols containing fluorine atoms.
[0025] The nonpolar solvent containing fluorine atoms is preferably one or more of hydrofluoroalkanes, unsaturated halogenated hydrocarbons, perfluoroalkanes, perfluorinated or partially fluorinated aromatic solvents, fluorinated ethers, fluorinated esters, and perfluorinated amines.
[0026] The nonpolar solvent that does not contain fluorine atoms is preferably one or more of hydrocarbon solvents, hydrocarbon monoethers, and aromatic solvents.
[0027] The nonpolar solvent that does not contain fluorine atoms is preferably a solvent that is compatible with nonpolar solvents containing fluorine atoms.
[0028] In the light phase solvent, the content of the diluent is preferably 5 wt% to 45 wt%, more preferably 6 wt% to 40 wt%, and the content of the polar solvent containing fluorine atoms is preferably 55 wt% to 95 wt%, more preferably 60 wt% to 94 wt%.
[0029] In a preferred embodiment, the heavy phase solvent is composed of a nonpolar solvent containing fluorine atoms and a polar solvent containing fluorine atoms.
[0030] More preferably, in the heavy phase solvent, the content of the nonpolar solvent containing fluorine atoms is 60wt% to 95wt%, and the content of the polar solvent containing fluorine atoms is 5wt% to 40wt%.
[0031] The method for separating monocarboxylate-terminated perfluoropolyethers and dicarboxylate-terminated perfluoropolyethers by liquid-liquid extraction can be one or a combination of batch extraction, cross-flow extraction, countercurrent extraction, and fractional distillation extraction.
[0032] During extraction, the light and heavy phase solvents separate into upper and lower phases. If the ratio of the light to heavy phase solvent is too low or too high, it will lead to increased solvent consumption or poor extraction efficiency. Therefore, the ratio needs to be determined based on the partition coefficients of the monofunctional (perfluoro)polyether carboxylic acid compound and the difunctional (perfluoro)polyether carboxylic acid compound in each phase solvent system. The preferred volume ratio of the light to heavy phase solvent is 0.2 to 6:1.
[0033] Temperature affects the phase equilibrium of monofunctional (per)fluoropolyether carboxylic acid compounds and difunctional (per)fluoropolyether carboxylic acid compounds in a two-phase solvent. Appropriately increasing the extraction operating temperature can accelerate the mass transfer rate between the two phases, while the operating temperature should be lower than the boiling point of the selected solvent. The preferred extraction temperature is 10–70°C, more preferably 15–65°C.
[0034] The method for separating monocarboxylate-terminated perfluoropolyether and dicarboxylate-terminated perfluoropolyether by liquid-liquid extraction according to the present invention, wherein the purity of the monocarboxylate-terminated perfluoropolyether in the high-purity monocarboxylate-terminated perfluoropolyether product is not less than 98% and the yield is not less than 75%.
[0035] The beneficial effects of this invention are:
[0036] 1. This invention is the first to use liquid-liquid extraction technology for the separation of mono / bifunctional perfluoropolyethers with carboxylate end groups. The extraction operation is simple, the process is simple, the operation is stable, the production capacity is high, and the cost is low.
[0037] 2. The solvent used in this invention is easy to recover.
[0038] 3. The present invention separates products with high purity, and can separate monofunctional (per)fluoropolyether carboxylates with a purity of not less than 98% from mixtures of (per)fluoropolyether carboxylates, while having a high yield. Detailed Implementation
[0039] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.
[0040] In the following embodiments, unless otherwise specified, "%" is based on molar reference.
[0041] Example 1
[0042] 3 grams of a Z-type perfluoropolyether mixture containing 60% mono- and 40% di-carboxylate sodium salts, mixed with 120 ml of pentafluoroacetone, 12 ml of N,N-dimethylformamide, and 100 ml of... The mixture was mixed with HFE7200 and extracted at 30°C. After phase separation, the extract and raffinate were collected and concentrated to remove the solvent, yielding a monofunctional perfluoropolyether carboxylate sodium salt with a purity of 98.5% and a yield of 85%.
[0043] Example 2
[0044] Three grams of a Z-type perfluoropolyether mixture containing 45% mono-terminated sodium carboxylate and 55% di-terminated sodium carboxylate were mixed with 130 mL of trifluoroacetic acid, 40 mL of N,N-dimethylformamide, 10 mL of ethanol, and 110 mL of perfluorohexane. The mixture was extracted at 25 °C, allowed to separate into two phases, and the extract and raffinate were collected. The solvent was removed by concentration to obtain a monofunctional perfluoropolyether sodium carboxylate with a purity of 98.3% and a yield of 80%.
[0045] Example 3
[0046] Three grams of a Z-type perfluoropolyether mixture containing 80% mono-terminated potassium carboxylate and 20% di-terminated potassium carboxylate were mixed with 130 mL of hexafluoroisopropanol, 35 mL of sulfolane, and 110 mL of heptafluorocyclopentane. The mixture was extracted at 20 °C, allowed to separate into two phases, and the extract and raffinate were collected. The solvent was removed by concentration to obtain a monofunctional perfluoropolyether potassium carboxylate with a purity of 98.7% and a yield of 83%.
[0047] Example 4
[0048] 3 grams of a Y-type perfluoropolyether mixture containing 75% single-terminated potassium carboxylate and 25% double-terminated potassium carboxylate, mixed with 150 ml of trifluoroethanol, 55 ml of dimethyl sulfoxide, and 100 ml of... The mixture was mixed with HFE 7300 and extracted at 35°C. After phase separation, the extract and raffinate were collected and concentrated to remove the solvent, yielding a monofunctional perfluoropolyether carboxylate potassium salt with a purity of 98.9% and a yield of 87%.
[0049] Example 5
[0050] Three grams of a Z-type perfluoropolyether mixture containing 70% mono-terminated sodium carboxylate and 30% di-terminated sodium carboxylate were mixed with 150 mL of pentafluoropropanol, 40 mL of dimethyl sulfoxide, and 100 mL of AE-3000 (CF3CH2OCF2CHF2). The mixture was extracted at 30 °C, allowed to separate into two phases, and the extract and raffinate were collected. The solvent was removed by concentration to obtain monofunctional perfluoropolyether sodium carboxylate with a purity of 98% and a yield of 93%.
[0051] Example 6
[0052] Three grams of a Y-type perfluoropolyether mixture containing 50% mono-terminated potassium carboxylate and 50% di-terminated potassium carboxylate were mixed with 50 mL of trifluoroacetic acid, 30 mL of dimethyl sulfoxide, 100 mL of pentafluoropropanol, and 130 mL of methylpentadecafluoroheptyl ketone. The mixture was extracted at 20 °C, allowed to separate into two phases, and the extract and raffinate were collected. The solvent was removed by concentration to obtain a monofunctional perfluoropolyether potassium carboxylate with a purity of 98.2% and a yield of 90%.
[0053] Example 7
[0054] Three grams of a Y-type perfluoropolyether mixture containing 80% mono-terminated potassium carboxylate and 20% di-terminated potassium carboxylate were mixed with 150 mL of pentafluoropropanol, 20 mL of N,N-dimethylformamide, 20 mL of water, and 150 mL of m-xylene hexafluoride. The mixture was extracted at 30 °C, allowed to separate into two phases, and the extract and raffinate were collected. The solvent was removed by concentration to obtain a monofunctional perfluoropolyether potassium carboxylate with a purity of 99% and a yield of 89%.
[0055] Example 8
[0056] Three grams of a Y-type perfluoropolyether mixture containing 30% mono-terminated potassium carboxylate and 70% di-terminated potassium carboxylate were mixed with 150 mL of pentafluoropropanol, 40 mL of dimethyl sulfoxide, 20 mL of methanol, and 150 mL of CF3CHFCHFC2F5. The mixture was extracted at 50 °C, allowed to separate into two phases, and the extract and raffinate were collected. The solvent was removed by concentration to obtain a monofunctional perfluoropolyether potassium carboxylate with a purity of 98.2% and a yield of 92%.
[0057] Example 9
[0058] 3 grams of a K-type perfluoropolyether mixture containing 50% mono- and 50% di-terminated potassium carboxylates, mixed with 100 ml of pentafluoropropanol, 30 ml of N,N-dimethylformamide, 10 ml of water, and 150 ml of... The mixture of HFE 7100 was extracted at 40°C, allowed to separate into two phases, and the extract and raffinate were collected. The solvent was removed by concentration to obtain a monofunctional perfluoropolyether carboxylate potassium salt with a purity of 98.8% and a yield of 75%.
[0059] Example 10
[0060] 2 grams of a D-type perfluoropolyether mixture containing 50% mono- and 50% di-terminated sodium carboxylate, mixed with 120 ml of trifluoroethanol, 40 ml of N,N-dimethylformamide, and 150 ml of... The mixture of HFE7100 was extracted at 40°C, allowed to separate into two phases, and the extract and raffinate were collected. The solvent was removed by concentration to obtain a monofunctional perfluoropolyether carboxylate sodium salt with a purity of 98.2% and a yield of 90%.
[0061] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.
Claims
1. A method for separating monocarboxylate-terminated perfluoropolyethers and dicarboxylate-terminated perfluoropolyethers by liquid-liquid extraction, characterized in that, include: A mixture of monocarboxylate-terminated perfluoropolyether and dicarboxylate-terminated perfluoropolyether is contacted and mixed with a light and heavy phase solvent. After extraction equilibrium, the two phases are separated and the solvent is removed. The heavy phase yields a high-purity monocarboxylate-terminated perfluoropolyether product with a purity of not less than 98%, while the light phase yields a product containing dicarboxylate-terminated perfluoropolyether. The light phase solvent is composed of a diluent and a polar solvent containing fluorine atoms; the diluent is one or more selected from sulfolane, dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, water, ethylene glycol, acetonitrile, acetic acid, ethanol, and methanol; in the light phase solvent, the content of the diluent is 5wt%~45wt%, and the content of the polar solvent containing fluorine atoms is 55wt%~95wt%. The heavy-phase solvent is composed of a nonpolar solvent containing fluorine atoms and a polar solvent containing fluorine atoms, wherein the content of the nonpolar solvent containing fluorine atoms is 60wt%~95wt% and the content of the polar solvent containing fluorine atoms is 5wt%~40wt%. The ratio of the light phase solvent to the heavy phase solvent is 0.2 to 6:1; The polar solvent containing fluorine atoms is one or more of the following: fluorine-containing carboxylic acids, fluorine-containing ketones, and fluorine-containing alcohols. The nonpolar solvent containing fluorine atoms is one or more of hydrofluoroalkanes, perfluoroalkanes, perfluorinated or partially fluorinated aromatic solvents, fluorinated ethers, fluorinated esters, and perfluorinated amines.
2. The method for liquid-liquid extraction separation of monocarboxylate-terminated perfluoropolyethers and dicarboxylate-terminated perfluoropolyethers according to claim 1, characterized in that, In the mixture containing monocarboxylate-terminated perfluoropolyether and dicarboxylate-terminated perfluoropolyether, the content of the monocarboxylate-terminated perfluoropolyether is 4wt%~96wt%; The monocarboxylate-terminated perfluoropolyether has the structure shown in formula (I): A-R f1 -B1(I) The dicarboxylate-terminated perfluoropolyether has the structure shown in formula (II): B 21 -R f2 -B 22 (II) In equations (I) and (II): A is an F atom or a C1-C4 perfluorinated alkyl chain; B1, B 21 B 22 All are carboxylate terminal functional groups, each independently chosen, and all satisfy the expression -CFXCOOM, where: X is F, or a C1-C4 alkyl group with all or part of its hydrogen atoms replaced by fluorine atoms, and M is Na. + K + 、Rb + or Cs + ; R f1 R f2 The perfluoropolyether backbones, with a number average molecular weight of 300-25000, all satisfy the chemical structure shown in formula (III) below, and are independently selected: -O(CF2O) a -(C2F4O) b -(C3F6O) c -(C4F8O) d -(III) In equation (III): a, b, c, and d are each independently selected from integers from 0 to 300, and the sum of a, b, c, and d is greater than 3; the order of the above repeating units (CF2O), (C2F4O), (C3F6O), and (C4F8O) is arbitrary, and the repeating unit (C3F6O) includes one or more of the following structures: (CF2CF2CF2O), (CF2CF(CF3)O), and (CF(CF3)CF2O).
3. The method for liquid-liquid extraction separation of monocarboxylate-terminated perfluoropolyethers and dicarboxylate-terminated perfluoropolyethers according to claim 1, characterized in that, In the light phase solvent, the content of the diluent is 6wt%~40wt%, and the content of the polar solvent containing fluorine atoms is 60wt%~94wt%.
4. The method for liquid-liquid extraction separation of monocarboxylate-terminated perfluoropolyethers and dicarboxylate-terminated perfluoropolyethers according to claim 1, characterized in that, Liquid-liquid extraction is one or more of the following: batch extraction, cross-flow extraction, countercurrent extraction, and fractional distillation extraction.
5. The method for liquid-liquid extraction separation of monocarboxylate-terminated perfluoropolyethers and dicarboxylate-terminated perfluoropolyethers according to claim 1, characterized in that, The extraction temperature is 10~70℃.
6. The method for liquid-liquid extraction separation of monocarboxylate-terminated perfluoropolyethers and dicarboxylate-terminated perfluoropolyethers according to claim 5, characterized in that, The extraction temperature is 15~65℃.
7. The method for liquid-liquid extraction separation of monocarboxylate-terminated perfluoropolyethers and dicarboxylate-terminated perfluoropolyethers according to claim 1, characterized in that, The yield of monocarboxylate-terminated perfluoropolyether in the high-purity monocarboxylate-terminated perfluoropolyether product is not less than 75%.