Method for recovering anionic fluorinated emulsifier

Abstract

To provide a method for recovering an acid of an anionic fluorinated emulsifier with a high yield from a basic ion exchange resin having a nonionic surfactant physically adsorbed thereon and having the anionic fluorinated emulsifier adsorbed thereon. A method for eluting and recovering an acid of an anionic fluorinated emulsifier from a basic ion exchange resin having a nonionic surfactant physically adsorbed thereon and having the anionic fluorinated emulsifier adsorbed thereon, which comprises a step (1) of bringing the basic ion exchange resin into contact with a water-soluble organic solvent and a step (2) of recovering the acid of the anionic fluorinated emulsifier from the basic ion exchange resin from which the ionic surfactant is eluted in the step (1).

Claims

1. A method for recovering an anionic fluorinated emulsifier, which comprises eluting an anionic fluorinated emulsifier from a basic ion exchange resin having a nonionic surfactant physically adsorbed thereon and having the anionic fluorinated emulsifier adsorbed thereon and recovering it as an acid of the anionic fluorinated emulsifier, and which is characterized by comprising a step (1) of bringing the basic ion exchange resin into contact with a water-soluble organic solvent, and then a step (2) of recovering the acid of the anionic fluorinated emulsifier from the basic ion exchange resin from which the ionic surfactant is eluted in the step (1) wherein the step (2) comprises a step (2-1) of bringing the basic ion exchange resin into contact with an aqueous inorganic acid solution and a water-soluble organic solvent.

2. The method for recovering an anionic fluorinated emulsifier according to claim 1, wherein the step (2) comprises the above step (2-1), and a step (2-2) of separating the mixture into the basic ion exchange resin and a liquid phase and recovering the liquid phase, and a step (2-3) of recovering the acid of the anionic fluorinated emulsifier from the liquid phase, in this order.

3. The method for recovering an anionic fluorinated emulsifier according to claim 1, wherein the step (2-1) comprises a step (2-1-1) of bringing the basic ion exchange resin into contact with the aqueous inorganic acid solution and then a step (2-1-2) of bringing the basic ion exchange resin into contact with the water-soluble organic solution.

4. The method for recovering an anionic fluorinated emulsifier according to claim 3, which comprises the above step (2-1-1), then a step (2-1-1-2) of separating and recovering the basic ion exchange resin, and then the step (2-1-2).

5. The method for recovering an anionic fluorinated emulsifier according to claim 1, wherein the water-soluble organic solvent is at least one member selected from the group consisting of an organic solvent having a nitrile group, an alcohol, a ketone and an ester.

6. The method for recovering an anionic fluorinated emulsifier according to claim 1, wherein the aqueous inorganic acid solution is at least one member selected from the group consisting of an aqueous hydrochloric acid solution, an aqueous sulfuric acid solution, an aqueous nitric acid solution and an aqueous phosphoric acid solution.

7. The method for recovering an anionic fluorinated emulsifier according to claim 1, wherein the water-soluble organic solvent is an organic solvent having a nitrile group, and the organic solvent having a nitrile group is at least one member selected from the group consisting of acetonitrile, propionitrile, butyronitrile and isobutyronitrile.

8. The method for recovering an anionic fluorinated emulsifier according to claim 1, wherein the acid of the anionic fluorinated emulsifier is a fluorinated carboxylic acid.

9. The method for recovering an anionic fluorinated emulsifier according to claim 8, wherein the acid of the anionic fluorinated emulsifier is a C.sub.5-7 fluorinated carboxylic acid which may have from 1 to 3 etheric oxygen atoms.

10. The method for recovering an anionic fluorinated emulsifier according to claim 1, wherein the basic ion exchange resin is a strongly basic ion exchange resin.

11. The method for recovering an anionic fluorinated emulsifier according to claim 1, wherein the concentration of the aqueous inorganic acid solution is at least 5.0 mass %.

12. The method for recovering an anionic fluorinated emulsifier according to claim 1, wherein the amount of the inorganic acid in the aqueous inorganic acid solution is within such a range that the acid of the anionic fluorinated emulsifier to be eluted/the inorganic acid is from 1/20 to 1.5/1 by the molar ratio.

13. The method for recovering an anionic fluorinated emulsifier according to claim 1, wherein the ratio of the basic ion exchange resin to the aqueous inorganic acid solution is from 90/10 to 10/90 by the mass ratio.

14. The method for recovering an anionic fluorinated emulsifier according to claim 1, wherein the ratio of the basic ion exchange resin to the water-soluble organic solvent is from 10/90 to 70/30 by the mass ratio.

Description

EXAMPLES

(1) Now, the present invention will be described in further detail with reference to Examples and Comparative Examples. However, it should be understood that the present invention is by no means restricted thereto. Ex. 1 to 10 and 13 are Examples of the present invention, and Ex. 11, 12 and 14 are Comparative Examples. The NSAA removal rate was calculated by the following method.

(2) [Measurement of NSAA Removal Rate (%) and AFE Recovery Rate (%)]

(3) The NSAA was eluted from the basic IER having the NSAA physically adsorbed thereon into acetonitrile, and the content (g) of the NSAA in acetonitrile was measured.

(4) Then, the acid of the AFE was eluted from the basic IER, and the content (g) of the NSAA in the obtained liquid phase having the acid of the AFE recovered therein was measured.

(5) The NSAA content in each liquid phase was determined by quantitative analysis by .sup.1H-NMR and .sup.19F-NMR using a nuclear magnetic resonator JNM-ECP400 manufactured by JEOL Ltd. The NSAA removal rate and the AFE recovery rate were calculated based on the following formula.
NSAA removal rate (%)=[NSAA content (g) in acetonitrile/(NSAA content (g) in acetonitrile+NSAA content (g) in liquid phase having acid of AFE recovered therein]×100

(6) The AFE recovery rate (%) was calculated in accordance with the following formula by obtaining the amount of the AFE by quantitative analysis by .sup.19F-NMR.
AFE recovery rate (%)=[AFE (g) in liquid phase having acid of AFE recovered therein/amount (g) of AFE adsorbed on basic IER]×100  [Ex. 1]

(7) 2,370 g of water containing 60 g of a NSAA (Newcol 1308-FA(90), nonionic surfactant manufactured by Nippon Nyukazai Co., Ltd.) and 70 g of AFE (CF.sub.3CF.sub.2OCF.sub.2CF.sub.2OCF.sub.2COONH.sub.4) and 100 g of a basic IER (Lewatit MonoPlus MP62WS, weakly basic IER manufactured by Lanxess, average particle size: 470 μm, ion exchange capacity: 1.7 meq/ml) were stirred at 25° C. for 8 hours to obtain 156 g of a basic IER having 2.5 mass % of the NSAA and 24 mass % of the AFE adsorbed thereon.

(8) Here, the amount of the NASS adsorbed on the basic IER was obtained from the concentration in the residue. Into a glass bottle, 5 mL of a cobalt thiocycanate solution (obtained by dissolving 87 g of thiocyanic acid and 14 g of cobalt sulfate in about 500 mL of water) and 5 mL of chloroform were put, and further from 1 to 10 mL of a measurement sample was added, followed by vigorous stirring, the mixture was left at rest, and the lower chloroform phase was collected. The absorbance of the collected chloroform phase was measured at 630 nm by a spectrophotometer. Depending upon the amount of the NASS, the chloroform phase turns blue. A calibration curve was prepared by measuring the absorbance in the same method using an aqueous NASS solution having a known concentration, and using the calibration curve, the concentration was obtained.

(9) The AFE amount was obtained from the concentration in the residue. In a glass bottle, 4 mL of a methylene blue solution (obtained by gradually adding 12 g of sulfuric acid to about 500 mL of water, followed by cooling, dissolving 0.03 g of methylene blue and 50 g of anhydrous sodium sulfate, and adding water to adjust the amount to 1 L) and 5 mL of chloroform were put, and further 0.1 g of a measurement sample diluted 1,000 to 3,000-hold was added, followed by vigorous stirring, the mixture was left at rest, and the lower chloroform phase was collected. The collected chloroform phase was subjected to filtration through a filter having pore sizes of 0.2 μm, and the absorbance at 630 nm was measured by a spectrophotometer. Depending upon the amount of the anionic fluorinated emulsifier, the chloroform phase turns blue. A calibration curve was prepared by measuring the absorbance in the same method using 0.1 g of an anionic fluorinated emulsifier solution having a known concentration, and using the calibration curve, the concentration of the anionic fluorinated emulsifier in the measurement sample was determined.

(10) Then, in a beaker having an internal capacity of 50 ml with a cover, 4 g of the basic IER having the AFE adsorbed thereon, 4 g of acetonitrile and 16 g of 1,3-dichloro-1,1,2,2,3-pentafluoropropane (hereinafter referred to as R-225) were charged, and the content was stirred by a magnetic stirrer for 60 minutes while the temperature was kept at 50° C. in a constant temperature bath, followed by cooling to room temperature. Then, the basic IER was separated and removed to obtain a liquid phase containing the NSAA (hereinafter referred to as a NSAA eluate). Then, in a beaker having an internal capacity of 50 ml with a cover, the separated basic IER and 4 g of a 17.5 mass % aqueous hydrochloric acid solution were charged, and the content was stirred by a magnetic stirrer for 60 minutes while room temperature at about 20° C. was maintained. Then, only the aqueous hydrochloric acid solution was withdrawn from the beaker. Then, in the beaker in which the basic IER treated with the aqueous hydrochloric acid solution was contained, 2 g of acetonitrile and 8 g of R-225 were charged, and the content was stirred by a magnetic stirrer for 60 minutes while the temperature was kept at 50° C. in a constant temperature bath, to extract the acid of the AFE. After completion of stirring, the basic IER was separated and removed to obtain a liquid phase (hereinafter referred to as an AFE eluate).

(11) Both the NSAA eluate and the AFE eluate were separated into two phases after left at rest, and only the lower layers were recovered and respectively taken as a NSAA eluate 1 and an AFE eluate 1.

(12) The NSAA contents in the NSAA eluate 1 and the AFE eluate 1 were determined and as a result, the NSAA eluate 1 contained 88 mg of the NSAA and the AFE eluate 1 contained 8 mg of the NSAA. From the results, the NSAA removal rate was calculated to be 92% in accordance with the above formula.

(13) The AFE eluate 1 contained 0.89 g of the acid of the AFE, and the AFE recovery rate was 93%.

(14) [Ex. 2 to 9]

(15) A NSAA eluate 1 and an AFE eluate 1 were obtained in the same manner as in Ex. 1 except that the amounts of the basic IER having the AFE adsorbed thereon obtained in Ex. 1, acetonitrile and R-225 were changed as identified in Table 1. The NSAA contents were measured, and the NSAA removal rate was calculated. The results are shown in Table 1 together with the AFE recovery rate.

(16) [Ex. 10]

(17) In a beaker having an internal capacity of 50 ml with a cover, 4 g of the basic IER having the AFE adsorbed thereon obtained in Ex. 1, 1.5 g of acetonitrile and 6 g of R-225 were charged, and the content was stirred by a magnetic stirred for 60 minutes while the temperature was kept at 40° C. in a constant temperature bath, followed by cooling to room temperature. Then, the basic IER was separated and removed to obtain a liquid phase containing the NSAA (hereinafter referred to as a NSAA eluate). Such an operation was repeated twice. Further, a NSAA eluate 1 and an AFE eluate 1 were obtained in the same manner as in Ex. 1 except that the amounts of acetonitrile and R-225 were changed as identified in Table 1. The NSAA contents were measured, and the NSAA removal rate was calculated in accordance with the above formula. The results are shown in Table 1 together with the AFE recovery rate.

(18) [Ex. 11]

(19) A NSAA eluate 1 and an AFE eluate 1 were obtained in the same manner as in Ex. 7 except that the NSAA eluate 1 was obtained without using acetonitrile. The NSAA contents were measured, and the NSAA removal rate was calculated in the same manner as in Ex. 1. The results are shown in Table 1 together with the AFE recovery rate.

(20) [Ex. 12]

(21) A NSAA eluate 1 and an AFE eluate 1 were obtained in the same manner as in Ex. 7 except that the NSAA eluate 1 was obtained by using a 2 mass % aqueous salt solution instead of acetonitrile. The NSAA contents were measured, and the NSAA removal rate was calculated in the same manner as in Ex. 1. The results are shown in Table 1 together with the AFE recovery rate.

(22) TABLE-US-00001 TABLE 1 Ex. 1 2 3 4 5 6 7 8 9 10 11 12 Amount of basic IER (g) 4 4 4 4 4 4 4 4 4 4 4 4 NSAA Amount of 4 3 2.7 2 3 3 16 8 16 1.5 — — eluate acetonitrile (g) Amount of salt — — — — — — — — — — — 4 solution (g) Amount of 16 12 10.8 8 12 12 16 16 0 6 16 16 R-225 (g) AFE Amount 4 4 4 4 4 4 4 4 4 4 4 4 eluate of 17.5% aqueous hydrochloric acid solution (g) Amount of 2 2 2 2 3 1.5 3 3 3 2 3 3 acetonitrile (g) Amount of 8 8 8 8 12 6 12 12 12 8 12 12 R-225 (g) NSAA in NSAA 88 88 86 84 88 95 87 93 89 90 81 82 eluate 1 (mg) NSAA in AFE 8 8 14 13 6 8 3 4 6 2 16 16 eluate 1 (mg) NSAA removal 92 92 86 87 93 92 96 95 93 98 84 84 rate (%) AFE recovery rate 93 93 91 92 90 84 88 91 91 96 89 90 (%)

(23) It was confirmed that the AFE recovery rate decreased if the NSAA was contained in the post-step of recovering the acid of the AFE from the basic IER having the AFE adsorbed thereon into the AFE eluate 1 and then recovering the acid of the AFE by separation and purification from the AFE eluate 1 by distillation.

(24) That is, in Examples of the present invention (Ex. 1 to 10), the NSAA recovery rate was high as compared with Comparative Examples (Ex. 11 and 12) in which no water-soluble organic solvent was used. Particularly in Examples of the present invention, the NSAA content in the AFE eluate 1 was low, and the recovery of the acid of the AFE in the post-step was not impaired, and thus the recovery rate of the acid of the AFE was high.

(25) When the NSAA recovery rate is at least 85%, when the acid of the AFE was separated and purified by distillation, the recovery rate of the acid of the AFE contained in the AFE eluate 1 is 90% or higher while the amount of impurities is suppressed to 0.2% or lower. Whereas when the NSAA removal rate is lower than 85% as in Comparative Examples, it is not possible to satisfy both an amount of impurities of 0.2% or lower and a recovery rate of the acid of the AFE contained in the AFE eluate 1 of 90% or higher. In fact, in Comparative Examples, the recovery rate of the acid of the AFE was so low as 70% even though the AFE recovery rate was somewhat high.

(26) [Ex. 13]

(27) The acid of the AFE recovered in Ex. 5 was purified by distillation, whereupon the acid of the AFE with a purity of at least 99.8% was obtained with a yield of 90%. Accordingly, the recovery rate of the acid of the AFE with a purity of 99.8% from the IER was 81%.

(28) [Ex. 14]

(29) The acid of the AFE was purified by distillation in the same manner as in Ex. 13 except that the acid of the AFE used for distillation was changed to the acid of the AFE obtained in Ex. 12. As a result, the yield of the acid of the AFE with a purity of at least 99.8% was 70%, and the recovery rate of the acid of the AFE with a purity of at least 99.8% from the IER was 63%.

(30) As described above, in a case where the acid of the AFE was distilled in a state where removal of the NSAA is insufficient, impurities resulting from decomposition of the NSAA are hardly separated by distillation, and a high purity AFE can hardly be obtained by distillation.

INDUSTRIAL APPLICABILITY

(31) The method for recovering an AFE of the present invention, by which an AFE can be recovered with a high yield from a basic IER having a NSAA as an impurity adsorbed thereon, is applicable to recovery of an AFE contained in industrial effluents and in products such as a fluorinated polymer aqueous dispersion. Further, it is applicable to recovery of not only an AFE but also a low molecular weight perfluoroalkanoic acid such as trifluoroacetic acid or perfluorobutanoic acid.

(32) This application is a continuation of PCT Application No. PCT/JP2015/059986, filed on Mar. 30, 2015, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-072947 filed on Mar. 31, 2014. The contents of those applications are incorporated herein by reference in their entireties.