WO2003082793A1

WO2003082793A1 - Process for the recovery of fluorine-containing emulsifier

Info

Publication number: WO2003082793A1
Application number: PCT/JP2003/003845
Authority: WO
Inventors: Hiroshi Funaki; Masataka Eda; Hiroki Kamiya; Koichi Yanase
Original assignee: Asahi Glass Company, Limited
Priority date: 2002-03-28
Filing date: 2003-03-27
Publication date: 2003-10-09
Also published as: JP2003284921A

Abstract

A process for the recovery of a fluorine-containing emulsifier which comprises bringing an exhaust gas from the step of drying and/or thermal treatment of a fluoropolymer which is produced by emulsion polymerization or aqueous dispersion polymerization in an aqueous medium containing a fluorine -containing emulsifier and contains the fluorine-containing emulsifier into contact with an aqueous solution whose pH is adjusted to 7 or above but below 12 with an alkali to make the fluorine-containing emulsifier absorbed in the aqueous alkaline solution, forming a layer double hydroxide in the aqueous solution containing the fluorine-containing emulsifier, immobilizing the emulsifier among the layers, and recovering the emulsifier. According to this process, a fluorine-containing emulsifier can be withdrawn at high recovery from an exhaust gas from the step of drying and/or heat treatment of a fluoropolymer.

Description

Specification

TECHNICAL FIELD The present invention relates to a method for recovering a fluorinated emulsifier contained in exhaust gas. Background art

Conventionally, as a method for recovering a fluorinated emulsifier used for emulsion polymerization of a fluorinated polymer, a fluorinated emulsifier contained in exhaust gas from a drying step and a heat treatment step of the fluorinated polymer is collected in a gas absorption tower. Methods of contact absorption in a solvent or solution are known.

For example, US Pat. No. 5,990,330, DE 19527276, EP 731081, and JP-A-8-253439 describe that exhaust gas containing a fluorinated emulsifier is contact-absorbed in a high-concentration aqueous solution of PH with a pH of about 14 to form a fluorinated emulsifier. A method for recovering the metal salt by precipitation is described. Further, WO98Z05621, EP0938464, and the like describe a method of adjusting the high-concentration aqueous aluminum solution by using a carbon dioxide realm.

On the other hand, as a method for recovering the fluorinated emulsifier from a low-concentration aqueous solution, a technique using an anion exchange resin (hereinafter referred to as IER) is known.

For example, Japanese Patent Publication No. 47-51233, US Pat. No. 3,882,153, DE 2044986, and the like describe that ammonium perfluorooctanoate (hereinafter referred to as APFO), which is a fluorine-containing emulsifier contained in coagulated wastewater of a fluorine-containing polymer, is adsorbed to the IER. It describes a method of recovering by immersion.

WO 99/62830 discloses that nonionic or ionic surfactants are added to flocculated wastewater of a fluoropolymer to stabilize polytetrafluoroethylene (hereinafter referred to as PTFE) fine particles in the flocculated wastewater, A method for preventing clogging of a packed tower is described.

JP-A-55-120630, US Pat. No. 4,369,266 and DE2908001 describe that PTFE coagulated wastewater is concentrated by ultrafiltration and a part of APFO used for PTFE production is recovered, and then APER is adsorbed and recovered by IER. The method is described. JP-A-55-104651, US4282162 and DE2903981 describe a method in which APFO is adsorbed on ER, and then perfluoractonic acid is desorbed and recovered using a mixture of an acid and an organic solvent.

WO 99Z62858 discloses that lime water is added to the coagulated waste water of a tetrafluoride tyrennoperfluoro (alkylvinyl ether) copolymer (hereinafter referred to as PFA) to adjust the pH to 6 to 7.5. After adjusting to pH, non-agglomerated PFA is aggregated by adding metal salts such as aluminum chloride and iron chloride, and then the aggregates are mechanically separated and removed. The following describes a method for preparing and adsorbing and recovering APFO using a strongly basic IER.

In addition, the 76th Annual Meeting of the Chemical Society of Japan (August 15, 1999, p. 600) and the 80th Autumn Meeting of the Chemical Society of Japan (April 7, 2001) Published in Japan, p. 41), a technique for fixing perfluoroactic acid and its ammonium salt using layered double hydroxides of aluminum and zinc is reported. WO 02/10104 and WO 02/10105 further disclose adding a divalent metal salt and a trivalent metal salt to a solution containing a fluorine-based compound or a solution containing a fluorine-based compound and a fluorine-containing polymer. By precipitating a layered double hydroxide containing a compound between the layers, the fluorine-based compound is fixed at a high ratio, and if necessary, the precipitated layered double hydroxide is recovered, and the fluorine-based compound or the fluorine-containing compound between the layers is recovered. A method for separating salts is described.

In the recovery from exhaust gas using a high-concentration aqueous alkali solution, the bubbling of the fluorinated emulsifier cannot be completely suppressed with the increase in the concentration of the fluorinated emulsifier in the absorbing solution. It was difficult to continuously collect the time.

In addition, in the recovery method from wastewater using IER, it is necessary to remove suspended solid components (hereinafter, referred to as SS components) including non-agglomerated fluoropolymer before contact with IER. The removal of SS not only has a great effect on the recovery efficiency of the fluorinated emulsifier, but there are still many practical problems such as no effective SS removal method found.

In addition, the immobilization technology using layered double hydroxides reported in the above-mentioned lectures of the 76th Annual Meeting of the Chemical Society of Japan and the 80th Annual Meeting of the Chemical Society of Japan, Only the solidification in an aqueous solution in which only the acid and its ammonium salt were dissolved was shown, but the solidification of the actual fluoropolymer containing other contaminants was shown. There are no reports showing collection techniques for collection and drainage. Similarly, WO02 / 10104 and WO02 / 10105 do not recognize other impurities such as SS.

An object of the present invention is to provide a method capable of efficiently recovering a fluorine-containing emulsifier contained in an exhaust gas. Disclosure of the invention

The present inventors have made intensive studies on the recovery of the fluorinated emulsifier from the exhaust gas, and as a result, the exhaust gas from the drying step and the heat treatment step of the fluorinated polymer contains a large amount of carbon dioxide gas together with the fluorinated emulsifier. It has been found that the carbon dioxide gas has various effects on the recovery of the fluorine-containing emulsifier. For example, when the exhaust gas is brought into contact with the aqueous solution of the layered double hydroxide, immobilization of the fluorinated emulsifier between layers due to carbon dioxide gas or the like becomes insufficient, and the recovery cannot be increased. In addition, even when the high-concentration alkaline aqueous solution is used, difficulties such as foaming and the like arise due to contact of a large amount of carbon dioxide and the like with a high-concentration alkaline aqueous solution.

The present inventor has newly found that the above problems can be smoothly and advantageously solved by bringing an exhaust gas containing a fluorinated emulsifier into contact with a specific aqueous liquid to perform an absorption operation.

In the present invention, an exhaust gas (A) containing a fluorinated emulsifier is brought into contact with an aqueous liquid (B1) having a pH of 7 to less than 12, and the fluorinated emulsifier in the exhaust gas is absorbed into the aqueous liquid. (X) to obtain an aqueous liquid (B2) containing a fluorinated emulsifier, a step (Y) of fixing the fluorinated emulsifier in the aqueous liquid (B2) between layers of the layered double hydroxide, and A layered double hydroxide (C) in which the fluorinated emulsifier is fixed between the layers obtained in the step (Y) is separated, and a recovery step (Z) for recovering the fluorinated emulsifier is included. Provided is a method for recovering a fluorine emulsifier.

Further, the present invention provides a method for bringing an exhaust gas (A) containing a fluorinated emulsifier into contact with an aqueous liquid (B1) having a pH of 7 or more and less than 12 to absorb the fluorinated emulsifier in the exhaust gas into the aqueous liquid. At least, a step (X) of obtaining an aqueous liquid (B2) containing a fluorinated emulsifier, the wastewater (B3) after separation of the aqueous liquid (B2) and the fluorinated polymer in the step of producing the fluorinated polymer. Mixing step (XI), obtained in step (XI) (Y) for fixing the fluorinated emulsifier in the mixed aqueous liquid (B 4) between the layers of the layered double hydroxide, and the layered composite having the fluorinated emulsifier fixed between the layers obtained in the step (Y). The present invention provides a method for recovering a fluorinated emulsifier, which comprises a recovery step (Z) for separating a hydroxide (C) and recovering the fluorinated emulsifier. BEST MODE FOR CARRYING OUT THE INVENTION

The exhaust gas (A) in the present invention is not particularly limited as long as it is an exhaust gas containing a fluorinated emulsifier, and is usually a fluorinated polymer obtained by emulsion polymerization or aqueous dispersion polymerization in an aqueous medium containing a fluorinated emulsifier. Exhaust gas from one drying and Z or heat treatment step is preferred. Typically, an aqueous dispersion of a fluorinated polymer obtained by emulsion polymerization or aqueous dispersion polymerization of a fluorinated monomer or a fluorinated monomer and a monomer other than the fluorinated monomer in an aqueous medium containing a fluorinated emulsifier The fluorinated polymer is coagulated and separated by salting out or the like, and the separated fluorinated polymer is discharged from the heat treatment apparatus when drying and / or heat treatment is performed using a heat treatment apparatus such as an oven. Exhaust gas containing a trace amount of solid fine powder. Hereinafter, the case where the exhaust gas is used as the exhaust gas (A) will be described as a representative.

In the present invention, in step (X), the exhaust gas (A) is brought into contact with an aqueous liquid (B 1) having a pH of 7 or more and less than 12 to absorb the fluorinated emulsifier in the exhaust gas into the aqueous liquid. At least, an aqueous liquid (B 2) containing a fluorinated emulsifier is obtained. As a method for absorbing the fluorinated emulsifier into the aqueous liquid (B 2), a generally known gas absorbing device method can be used. As a gas absorption method, a liquid film type, a droplet type, a bubble type, a foam type and the like can be used. Examples of the gas absorbing device include, as a liquid film type, a packed tower, a wet wall tower, a submerged tower, a liquid jet, a ball tower, a disk tower, a toril, a seralysturil, and a Tyler absorbing device. Examples of the droplet type include a spray tower, a disk rotary absorption device, a cyclone scrubber, a venturi scrubber, a packed fluidized bed absorption device, a centrifugal absorption device, and the like.The bubble type includes a bubble column, a bubble stirring tank, and the like. A column can be exemplified. Further, examples of the foam type include foam separation.

In the present invention, in the step (X), when the fluorinated emulsifier in the exhaust gas (A) is absorbed into the aqueous liquid (B 1), a droplet type absorption device Z or a liquid film type absorption agent is used. It is preferable to use the device for reasons such as absorption efficiency and maintenance and inspection of the device. The exhaust gas (A) may be used in a gas absorption device such as an absorption tower (hereinafter, may be represented by an absorption tower). The linear velocity is not particularly limited, but is preferably from 0.01 m / sec to 10 m / sec, more preferably from 0.01 lm / sec to 5 mZ seconds, and particularly preferably from 0.01 mZ seconds to 3 mZ seconds. If the linear velocity is too high, the hold-up in the absorption tower (instantaneous water volume in the absorption tower) will be too large, and if the linear velocity is too low, it will take time to process, and it is not efficient. In the step (X), it is also preferable to equip a gas absorption tower with a droplet separation device (demister) to prevent the droplets from being entrained in the next step.

The amount of the aqueous liquid (B1) used in the step (X) is not particularly limited, but when the concentration of the fluorinated emulsifier in the obtained aqueous liquid (B2) is high, the processing speed is rapidly reduced due to foaming. Therefore, control the flow rate of the exhaust gas (A) and the amount of the aqueous liquid (B1) so that the concentration of the fluorinated emulsifier in the aqueous liquid (B2) is 10% by mass or more and 1% by mass or less. Is preferred.

Water is usually used as a raw material of the aqueous liquid (B1) in the step (X). The type of the water is not particularly limited, but adverse effects such as foaming of the aqueous liquid (B 1) or the aqueous liquid (B 2) due to the fluorinated emulsifier and contaminants contained in the exhaust gas (A), scaling to the absorption device, and the like. It is preferable to use ion-exchanged water from the viewpoint of preventing water leakage. Further, in the present invention, the wastewater (B3) after separating the fluorine-containing polymer in the production process of the fluorine-containing polymer can be used as the aqueous liquid (B1).

The aqueous liquid (B1) is preferably an aqueous liquid whose pH has been adjusted to 7 or more and less than 12 using an alkali. The temperature at the time of contact between the exhaust gas (A) and the aqueous liquid (B1) in the step (X) is not particularly limited, but is usually preferably 10 to 60 ° C. The temperature can be controlled by the temperature of the exhaust gas (A) and / or the aqueous liquid (B1), but it is usually practical and preferable to adjust the temperature by the temperature of the aqueous liquid (B1). The temperature of the aqueous liquid (B 1) is preferably from 10 ° C. to 60 ° C. in consideration of the solubility of the alkali and the fluorinated emulsifier. The alkali used for the aqueous liquid (B1) is not particularly limited, but may be sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, calcium hydrogen carbonate, An example is an ammonia monitor. Of these, calcium salts tend to cause scaling in the absorption tower over a long period of operation, so sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, or ammonia are more likely to occur. preferable.

In the step (X), the pH of the aqueous liquid used for gas absorption is basically preferable from the viewpoint of the properties of the fluorinated emulsifier to be absorbed. Is 7 or more and less than 12. The pH of the aqueous liquid (B1) is preferably 8 to 11. Further, in the present invention, the step (Y), that is, the step (Y) of fixing the fluorine-containing emulsifier between the layers of the layered double hydroxide to the aqueous liquid (B2) after gas absorption obtained in the step (X) is performed. Therefore, it is also preferable to previously adjust the H of the aqueous liquid (B1) to a pH suitable for the layered double hydroxide. In the present invention, as described above, the wastewater (B3) after separating the fluoropolymer in the production process of the fluoropolymer may be used as the aqueous liquid (B1) in the step (X). Further, after passing through the step (XI) of mixing the aqueous liquid (B2) obtained in the step (X) with the waste water (B3), the mixed aqueous liquid (B4) is obtained.

(Y) may also apply. Hereinafter, the description will be made using the aqueous liquid (B2) containing the fluorinated emulsifier, including the case where the wastewater (B3) is used and the case where the mixed aqueous liquid (B4) is used.

In the step (Y), the fluorinated emulsifier is fixed between the layers of the layered double hydroxide, and the fixation is performed by adsorbing the anion of the fluorinated emulsifier on the layered double hydroxide.

In general, three types of anion adsorption by layered double hydroxide are known: coprecipitation, ion exchange, and reconstruction. '' In the coprecipitation method, metal ions are added to the solution in which the recovery anion is dissolved to form a layered double hydroxide, and at the same time, the recovery anion is included between the layers of the layered double hydroxide. It is a way to make it. The replacement method is to prepare in advance a layered double hydroxide having a structure in which anions other than the target anion (eg, chloride ion, hydroxide ion, carbonate ion, etc.) are included between the layered double hydroxide layers. In this method, the layered double hydroxide is added to a solution in which the recovery anion is dissolved, and the recovery objective anion is included between the layers so as to replace the already encapsulated anion.

In the reconstruction method, a layered double hydroxide containing carbonate ions between the layers is synthesized, and calcined at a high temperature of 400 to 500 ° C to remove the carbonate ions inside. This is a method in which the anion to be recovered is included in the layered double hydroxide by adding it to a liquid in which the anion to be recovered is dissolved.

In the present invention, any of the above-mentioned methods can be employed in the step (Y), however, because the fluorine-containing emulsifier in the aqueous liquid (B 2) can be efficiently fixed between the layers of the layered double hydroxide. Preferably, a coprecipitation method is employed.

In the present invention, as the fluorinated emulsifier, a salt such as perfluoroalkanoic acid, ω-hydroperfluoroalkanoic acid, ω-chloroperfluoroalkanoic acid, or perfluoroalkanesulfonic acid having 5 to 13 carbon atoms is used. Is preferred. These may have a linear structure or a branched structure, or a mixture thereof. Further, the molecule may contain an etheric oxygen atom. When the number of carbon atoms is in this range, the effect as an emulsifier is excellent. The acid salt is preferably an alkali metal salt such as a lithium salt, a sodium salt or a potassium salt, or an ammonium salt, more preferably an ammonium salt or a sodium salt, and most preferably an ammonium salt.

Specific examples of the acid include perfluoropentanoic acid and perfluorohexanoic acid.

Perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorododecanoic acid, ω-hydroperfluoroheptanoic acid, ω-hydro Perfluorooctanoic acid, ω-hydroperfluorononanoic acid, ω-chloroperfluoroheptanoic acid, ω-chloroperfluorooctanoic acid, ω monochloroperfluorononanoic acid, etc. Is mentioned.

CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) COOH, CF ₃ CF ₂ CF ₂ O CF (CF ₃ ) CF ₂ OCF (CF ₃ ) CO〇H, CF ₃ CF ₂ CF ₂ O [CF (CF ₃ ) CF ₂ O] a CF (CF ₃ ) C〇OH, CF ₃ CF ₂ CF ₂ O [CF (CF ₃ ) CF ₂ O] 3 CF (CF ₃ ) CO〇H, CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ OCF (CF ₃ ) COOH, and perfluorohexane sulfonic acid, perfluoro Loheptanesulfonic acid, perfluorooctanesulfonic acid, perfluorononanesulfonic acid, perfluorodecanesulfonic acid and the like are also included.

Specific examples of the ammonium salt include ammonium perfluoropentanoate, ammonium perfluorohexanoate, ammonium perfluoroheptanoate, ammonium perfluorooctanoate (APFO), and perfluorononanoic acid. Ammonium, perfluorodecanoic acid ammonium, perfluorododecanoic acid ammonium, ω-hydroperfluoroheptanoic acid ammonium, ω-hydroperfluorooctanoic acid ammonium, ω-hydroperfluorononanoic acid ammonium, ω— Ammonium perfluoroheptanoate, ω-perfluorofluorobutanoic acid ammonium, and ω-perfluorofluorononanoic acid ammonium.

CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) COONH ₄ , CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COONH ₄ , CF ₃ CF ₂ CF ₂ 〇 [CF (CF ₃ ) CF ₂ 〇] 2 CF (CF ₃ ) COONH ₄ , CF ₃ CF ₂ CF ₂ 0 [CF (CF ₃ ) CF ₂ O] 3 CF (CF ₃ ) COONH ₄ , CF ₃ CF 2 CF ₂ CF ₂ CF ₂ OCF (CF ₃ ) COONH _{4 and the} like, ammonium perfluorohexane sulfonate, ammonium perfluoroheptane sulfonate, ammonium perfluorooctane sulfonate, ammonium perfluoro nonane sulfonate, perfluorodecane sulfone Acid ammonium is also included.

Specific examples of the lithium salt include lithium perfluoropentanoate, lithium perfluorohexanoate, lithium perfluoroheptanoate, lithium perfluorosiloxane, lithium perfluorononanoate, and lithium perfluoronate. Lithium perfluorodecanoate, lithium perfluorododecanoate, lithium ω-hydroperfluorohepnoate, lithium ω-hydroperfluorooctanoate, ω-hydroperfluorononanoic acid Lithium, ω-chromium Lithium perfluoroheptanoate, ω-chloro ぺ Lithium fluorooctanoate, monoperfluorolithium perfluorononanoate and the like.

CF ₃ CF ₂ CF ₂ 〇CF (CF ₃ ) COOL i, CF ₃ CF ₂ CF ₂ 〇CF (CF ₃ ) CF ₂ OCF (CF ₃ ) COOL i ゝ CF ₃ CF ₂ CF ₂ O [CF (CF ₃ ) CF ₂ O] ₂ CF (CF ₃ ) COOL i, CF ₃ CF ₂ CF ₂ 〇

[CF (CF ₃ ) CF ₂ 〇] 3 CF (CF ₃ ) COOL i, CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ OCF (CF ₃ ) COOL i, and the like. Lithium perfluoroheptanesulfonate, lithium perfluorooctanesulfonate, lithium perfluorononanesulfonate, lithium perfluorodecanesulfonate and the like are also included.

Specific examples of the sodium salt include sodium perfluoropentanoate, sodium perfluorohexanoate, sodium perfluoroheptanoate, sodium perfluorooctanoate, sodium perfluorononanoate, sodium perfluorodecanoate Sodium perfluorododecanoate, sodium ω-hydroperfluoroheptanoate, sodium ω-hydroperfluorooctanoate, sodium ω-hydroperfluorononanoate, ω-sodium perfluoroheptanoate, ω-clo mouth sodium perfluorooctanoate, ω-clo mouth sodium perfluorononanoate and the like.

CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) C) ONa, CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COON a, CF ₃ CF ₂ CF ₂ 〇 [CF (CF ₃ ) CF ₂ O] ₂ CF (CF ₃ ) COONa, CF ₃ CF ₂ CF ₂ O

[CF (CF ₃ ) CF ₂ O] 3 CF (CF ₃ ) COONa, CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ OCF (CF ₃ ) COON a, etc., and perfluoro sodium hexanesulfonate, perfluorohepta Sodium sulfonate sodium, perfluorodecane sodium sulfonate and the like can also be mentioned.

Specific examples of the potassium salt include potassium perfluoropentanoate, potassium perfluorohexanoate, potassium perfluoroheptanoate, potassium perfluorooctanoate, potassium perfluorononanoate, and perfluorophosphate Potassium decanoate Pum, potassium perfluorododecanoate, potassium ω-hydroperfluoroheptanoate, potassium ω-hydroperfluorooctanoate, potassium ω-hydroperfluorononanoate, ω-cloper per Potassium fluoroheptanoate, ω-chlorofluorofluorooctanoic acid rim, and ω-chloroperfluorononanoic acid rim.

Also, CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) COOK, CF ₃ CF ₂ CF ₂ O CF (CF ₃ ) CF ₂ OCF (CF ₃ ) COOK, CF ₃ CF ₂ CF ₂ O (CF (CF ₃ ) CF ₂ O] ₂ CF (CF ₃ ) COOK, CF ₃ CF ₂ CF ₂ O [CF (CF ₃ ) CF ₂ O] 3 CF (CF ₃ ) COOK, CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ OCF (CF ₃ ) COOK, etc., as well as potassium perfluorohexane sulfonate, potassium perfluoroheptane sulfonate, potassium perfluorooctane sulfonate, potassium perfluorononane sulfonate, potassium perfluorodecane sulfonate, etc. Can be

As the fluorinated emulsifier in the present invention, in particular, an ammonium salt of a perfluoroalkanoic acid having 6 to 12 carbon atoms is preferable, and ammonium perfluoroheptanoate, APFO, ammonium perfluorononanoate or perfluorodenoic acid is preferable. Ammonium acid is more preferred, and APFO is most preferred.

In the present invention, the waste water (B3) after separating the fluoropolymer in the production process of the fluoropolymer is defined as the copolymer of the fluoromonomer or the fluoromonomer and the monomer other than the fluoromonomer. This means wastewater from the polymer production process, and usually coagulated wastewater is preferred. Hereinafter, the coagulated wastewater will be described as a typical example. Here, the coagulated waste water from the above-mentioned manufacturing process refers to an emulsion polymerization or an aqueous dispersion polymerization of a fluorine-containing monomer or a fluorine-containing monomer and a monomer other than the fluorine-containing monomer in an aqueous medium containing a fluorine-containing emulsifier. This refers to waste water after the fluoropolymer is aggregated and separated by salting out or the like from the aqueous dispersion of the fluoropolymer obtained as above. The flocculated wastewater contains the fluorinated emulsifier used during the polymerization of the fluorinated monomer. Further, as described above, the exhaust gas (A) in the present invention is an exhaust gas from the process of producing a fluoropolymer, and the exhaust gas (A) contains the fluorinated emulsifier used during the polymerization of the fluorinated monomer. It is. Including a fluorine-containing emulsifier in the exhaust gas (A) Although the amount is not particularly limited, in the case of exhaust gas from a typical fluorine-containing polymer drying step and / or heat treatment step, the concentration of the fluorine-containing emulsifier in the exhaust gas is usually 0.001 g / Nm ³ or more and 10 gZNm ³ or less, preferably 0.01 gZNm ³ or more and 1 g / Nm ³ or less.

As the fluorinated monomer, tetrafluoroethylene modified styrene (hereinafter, TFE _{called.), CF 2 = CFC 1} , CFH = CF 2, CFH = CH 2, CF 2 = CH 2 ( hereinafter. Referred VdF) Furuoroechiren such s, the hexa full O b propylene (hereinafter. referred HEP), full O b propylene such as CF _₂ = CHCF _3, CF ₂ two CFOCF _3, CF ₂ two _{_{_{CFO (CF 2) 2 CF 3}}} ( hereinafter, PPVE Perfluoropinyl ethers having 3 to 10 carbon atoms such as CF ₂ = CFO (CF ₂ ) ₄ CF _{3, and} _{4 to} 10 carbon atoms such as CH ₂ = CH (CF ₂ ) 3 CF ₃ Fluoroalkyl) ethylenes and the like. These fluorinated monomers may be used alone or in combination of two or more.

Monomers other than the fluorinated monomer include pinyl esters such as vinyl acetate, vinyl ethers such as ethylvinyl ether, cyclohexyl vinyl ether and hydroxybutyl vinyl ether, and monomers having a cyclic structure such as norpolenene and norponadiene. And aryls such as methylaryl ether, ethylene (hereinafter referred to as E), propylene (hereinafter referred to as P), and olefins such as isobutylene. Monomers other than the fluorinated monomer may be used alone or in combination of two or more.

In the present invention, examples of the fluorine-containing polymer include PTFE, TFEZP copolymer, TFEZPZVdF copolymer, TFEZHFP copolymer, TFEZPPVE copolymer, E / TFE copolymer, polyvinylidene fluoride and the like. More preferably, it is PTFE, TFEZP copolymer, exactly £ 7? / ¥ 01 copolymer or just FEZPPVE copolymer, most preferably PTFE.

In the present invention, the fluorinated emulsifier contained in the exhaust gas (A) can be recovered, but when the waste water (B 3) is used as the aqueous liquid (B 1) or mixed through the step (X 1) When the aqueous liquid (B4) is used, the fluorinated emulsifier contained in the wastewater (B3) such as coagulated wastewater (hereinafter sometimes referred to as coagulated wastewater (B3)) is also processed. With (Y), the layered double hydroxide can be fixed between layers, and the fluorinated emulsifier contained in both the exhaust gas (排ガス) and the coagulated wastewater (Β3) can be recovered together.

In the step (Υ) of the present invention, when the coagulated waste water (Β 3) is alkaline, the pH of the waste water (Β 3) is reduced by hydrochloric acid and / or sulfuric acid and / or nitric acid.

It is preferable to adjust appropriately according to the layered double hydroxide used in (II). For example, when aluminum and zinc are used, it is preferably adjusted to 6 or more and less than 8, and when aluminum and magnesium are used, it is preferably adjusted to 9 or more and less than 11. If the coagulated wastewater (Β3) is acidic, use potassium hydroxide and / or sodium hydroxide to adjust the pH of the wastewater (Β3). As described above, when aluminum and zinc are used, 6 or more and less than 8 When using aluminum and magnesium, it is preferable to adjust the value to 9 or more and less than 11. If the pH is outside the above range, aluminum and zinc, or aluminum and magnesium each independently form a hydroxide, and form aluminum hydroxide, zinc hydroxide, and magnesium hydroxide. Is difficult to form, and as a result, the recovery efficiency of the fluorine-containing emulsifier is significantly reduced.

In the step (II), a layered double hydroxide can be formed if the formation of hydroxides of the trivalent metal and the divalent metal overlaps or the range of formation of both hydroxides is close. Examples of the trivalent metal include aluminum, bismuth, cerium, and chromium.

Examples thereof include (III), iron (III), gallium, indium, manganese (III), titanium, and titanium. However, aluminum is preferable because of a small load on the environment and the like and availability. On the other hand, examples of the divalent metal include beryllium, cadmium, cobalt, chromium (11), copper (II), iron (II), magnesium, manganese (11), nickel, lead (11), platinum, and palladium. Although zinc, tin, calcium and the like can be exemplified, zinc or magnesium is preferable, and magnesium is particularly preferable because of a small load on the environment and the like and availability.

In the present invention, the concentration of the fluorinated emulsifier in the coagulated wastewater (Β3) and the concentration of the fluorinated emulsifier in the aqueous liquid (Β2) are preferably 1% by mass or more and 10% by mass or less, and 10% by mass or less. The content is more preferably not less than ppm and not more than 1 mass%, particularly preferably not less than 50 mass ppm and not more than 0.5 mass%.

If the concentration of the fluorinated emulsifier is lower than this, the layered double hydroxide in step (Y) may cause The efficiency of capturing the fluorinated emulsifier decreases. If the concentration is higher than this, a simpler and more efficient method such as precipitation of the fluorinated emulsifier by changing pH can be used.

In the present invention, suspended solids such as non-agglomerated fluoropolymer fine particles and the like that can be suspended solids (hereinafter, these are collectively referred to as SS components) contained in the aggregated wastewater (B 3) are: It does not adversely affect the fixation and the fixation ratio of the fluorinated emulsifier in the step (Y). However, in the recovery step (Z), the fluorinated emulsifier may be hindered from being regenerated from the above-mentioned layered double hydroxide (C) force. It is preferable to remove to less than mass%. The SS component is more preferably removed to 0.3% by mass or less, particularly preferably to 0.05% by mass or less. Substances that can become suspended solids include metal salts used for salting-out and coagulation of fluoropolymers, Z and substances precipitated by changes in pH of coagulated wastewater (B3) and Z or coagulated wastewater (B 3) Substances that precipitate when the temperature drops or rises.

As a method for removing the SS component such as the non-aggregated fluorine-containing polymer, salting-out aggregation with a metal salt containing a polyvalent metal cation is effective. Specific examples of the metal salt (coagulant) include aluminum chloride, aluminum chloride hexahydrate, polychlorinated aluminum, ferrous chloride, and ferric chloride. Agglomerates may precipitate in a state in which a fluorinated emulsifier such as APFO is contained. Therefore, the pH is adjusted to 7 or more by adding sodium hydroxide and / or a hydration-powered rim to adjust the pH to 7 or more. It is preferred to redissolve the emulsifier from the aggregates in water.

In the present invention, a general solid-liquid separation method can be employed as a method for removing the aggregates of the SS component that is aggregated by adding the metal salt to the aggregated wastewater (B 3). It is preferable to use at least one method selected from the group consisting of a station, centrifugation, and gravity sedimentation. The filtration is also preferably performed under pressure. Further, it is preferable that the wastewater containing the aggregates is allowed to stand, the aggregates are settled, and the supernatant is filtered to remove the aggregates. From the viewpoint of facility maintenance and the like, a solid-liquid separation method using a thickener or a screw decanter is most preferable. In the step (Y) in the present invention, the pH at the time of mixing with the aqueous liquid (B2) or the mixed aqueous liquid (B4) is preferably adjusted to 9 or more and less than 11 when aluminum and magnesium are used. Normally, the molar ratio of aluminum ion: magnesium ion is 1: 2, and the concentration of aluminum ion and magnesium ion is each 0.

Using an aqueous solution of not less than 211101 / L and mixing with the aqueous liquid (B2) or the mixed aqueous liquid (B4) with stirring, the fluorinated emulsifier is fixed between the layers of the layered double hydroxide to be formed. . There is no problem with using any of the raw materials for aluminum ion and magnesium ion. Aluminum chloride, aluminum chloride hexahydrate, aluminum sulfate, and aluminum nitrate are preferred as aluminum ion raw materials because of availability, and aluminum chloride and aluminum chloride hexahydrate are particularly preferred. As a raw material of magnesium ion, magnesium chloride, magnesium chloride hexahydrate, magnesium nitrate hexahydrate, magnesium nitrate, magnesium sulfate, magnesium sulfate heptahydrate, and magnesium carbonate are preferable, and magnesium chloride is particularly preferable. Magnesium chloride hexahydrate is preferred.

When aluminum and zinc are used, the pH at the time of mixing with the aqueous liquid (B2) or the mixed aqueous liquid (B4) is preferably adjusted to 6 or more and less than 8. Usually, an aqueous solution in which the molar ratio of aluminum ion: zinc ion is 1: 2, and the concentrations of aluminum ion and zinc ion are respectively 0.0 lmo 11 or more and 211101 ZL or less is used while stirring. Mix with the aqueous liquid (B2) or mixed aqueous liquid (B4) to fix the fluorinated emulsifier between the layers of the layered double hydroxide to be formed. Aluminum and zinc ions can be used in any source. From the standpoint of availability, aluminum chloride, aluminum chloride hexahydrate, aluminum sulfate, and aluminum nitrate are preferable as aluminum ion raw materials, and aluminum chloride and aluminum chloride hexahydrate are particularly preferable. As a raw material for zinc ions, zinc chloride, zinc nitrate hexahydrate, zinc sulfate, and zinc sulfate heptahydrate are preferable, and zinc chloride is particularly preferable.

In the step (Y) of the present invention, the metal ion aqueous solution is preferably added at a metal ion concentration of 0.01 mol / L or more and 2 mol 1 / L or less. Metal ion concentration If the degree is lower than this, the amount of water will increase when the required metal is added, and as a result, the concentration of the fluorinated emulsifier will decrease, and the recovery efficiency will decrease. If the metal ion concentration is higher than this range, the metal ion aqueous solution is acidic. Therefore, by adding the aqueous solution, the optimum pH range for locally forming a layered double hydroxide in the step (Y) is obtained. Therefore, the metal ion is not effectively used for forming the layered double hydroxide. However, even when a metal ion aqueous solution having a concentration outside the above-described concentration range is once added, the fluorine-containing emulsifier can be efficiently recovered by adding a metal ion aqueous solution having an appropriate concentration range again.

In the step (Y) of the present invention, the amount of the metal ion used is such that the trivalent ion is 1 to 10 times the molar amount of the fluorinated emulsifier, and the divalent ion is the fluorinated emulsifier. It is preferable that the molar ratio of the trivalent ion to the divalent ion is 3: 1 to 1: 3 with respect to the molar ratio. The molar ratio of the trivalent ion to the divalent ion is more preferably 1: 1 to 1: 2. If the amount of the metal ion used is less than the above, the recovery of the fluorinated emulsifier is insufficient. Does not increase. Further, excessive use of the metal ions is not preferable from the viewpoint of increasing the load in the final wastewater treatment process.

In the step (Y), when the aqueous liquid (B 2) containing the fluorinated emulsifier is mixed with the metal ion aqueous solution, it is preferable to perform stirring. The stirring method is not particularly limited, but a stirring method that does not mechanically destroy the formed layered double hydroxide (C) is preferable. As the stirring blade of such a stirring device, a stirring blade capable of uniformly mixing the whole liquid mixture at a low speed is preferable, and one selected from the group consisting of a full zone blade, a max blend blade and an anchor blade is preferable. G value during stirring at the stirring blade is preferably from ¹ ~ 3 0 0 s 1, more preferably ^{5~2 5 0 s _ 1, 1} 0~2 0 0 s _ 1 is most preferred. Here, the G value refers to a value derived from the following equation.

P

G =

V-μ In the above formula, Ρ is the stirring power (W), V is the liquid volume (m ³ ), and X is the liquid viscosity coefficient (P a-s).

In the step (Y), during the mixing with the aqueous metal ion solution, bubbling with an inert gas such as nitrogen gas or argon gas or the like is performed to remove carbon dioxide and / or carbon dioxide present in the system. After expelling the carbonate ions and / or carbon dioxide gas with the gas, it is preferable to seal the reaction vessel. This is because the layered double hydroxide reacts with the carbonate ion and hinders the recovery of the fluorinated emulsifier. Flow rate of the inert gas when carrying out the bubbling ^{^{0. I Nm 3 / m 3}} · h~l O Nm 3 Zm 3 · h ^{preferably, 0. 1 Nm 3 / m} 3 · h~5 Nm 3 / m ³ · h is more preferred. If the gas flow rate is lower than this, the removal of carbonate ions and Z or carbon dioxide gas in the system will not be performed sufficiently.If the flow rate is higher than this, not only will the water evaporate with the gas, but also the heat of vaporization As a result, the temperature of the aqueous solution decreases.

The step (Y) is preferably performed at a temperature of 10 to 50 ° C. If the temperature is too high or too low, the fixing rate of the fluorine-containing emulsifier by the layered double hydroxide decreases. In particular, if the temperature is too low, the fixation rate is significantly reduced. Therefore, it is preferable to equip the immobilization reactor with a heating device.

In the step (Z) in the present invention, the layered double hydroxide (C) having the fluorinated emulsifier fixed between the layers obtained in the step (Y) is first separated. The separation method is not particularly limited, and a general solid-liquid separation method can be employed. In particular, it is preferable to use one or more methods selected from the group consisting of filtration, decantation, gravity sedimentation, and centrifugation. The filtration is also preferably performed under pressure. From the viewpoint of facility maintenance and the like, a solid-liquid separation method using a thickener or a screw decanter is most preferable.

Further, in the step (Z) in the present invention, the separated layered double hydroxide (C) and the fluorine-containing emulsifier are regenerated and recovered. As a method of this regeneration, for example, the layered double hydroxide (C) is redissolved with a strong acid such as hydrochloric acid, sulfuric acid, or nitric acid or a mixture of two or more kinds of the strong acids, and contains a precipitate precipitated from the solution. For example, the free acid of the fluorine emulsifier may be extracted with a water-insoluble organic solvent such as a fluorine-based solvent.

In addition, the method for recovering the fluorinated emulsifier of the present invention, not only the fluorinated emulsifier, Also, the present invention can be applied to low molecular weight fluorinated carboxylic acids such as trifluoroacetic acid and pentafluoropropanoic acid and / or salts thereof, trifluoromethanesulfonic acid and Z or salts thereof.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto. The concentration of APFO, perfluorooctanoic acid (hereinafter referred to as PFOA) or sodium perfluorooctanoate is determined by using a high-speed night-time chromatographic gel mass spectrum using a mixed solution of methanol and water as a solvent. It was measured using the method. Species to be detected by this method is per full O Roo Kuta hexanoate (C ₇ F _{1 5} COO I).

The SS component in the coagulated effluent was measured (unit: mass%) by measuring 10 g of the coagulated effluent after coagulating and separating PTFE from the aqueous dispersion of PTFE, using a METTLER TOLEDO Haguchi Gen-type moisture meter HR. — Put in 73, dried at 200 ° C until the mass became constant, and the evaporation residue was used as the SS component.

[Example 1]

PTFE powder was agglomerated from an aqueous PTFE dispersion produced by emulsion polymerization using APFO as an emulsifier. 10.0 kg of this PTFE powder (moisture content: 48% by mass) was placed in a hot-air circulation oven, and the temperature was gradually increased from 100 ° C to 5 ° C. Heat treated for hours. The displacement of the exhaust gas from the hot-air circulation oven was 4.5 Nm ³ . The entire amount of this exhaust gas was introduced into a spray tower having a diameter of 50 cm and a height of 500 cm. The linear velocity of the gas at this time was about 0.5 mZ seconds. In this spray tower, 35 kg of ion-exchanged water whose pH was adjusted to 10 using sodium hydroxide was circulated and sprayed. After the drying and heat treatment of the PTFE powder, the APFO concentration in the aqueous alkali solution in the spray tower was analyzed and found to be 498 mass ppm.

To this APFO-containing aqueous solution, a 0.2 N aqueous solution of sodium hydroxide was added to adjust the pH to 10.0. The liquid temperature was 26 ° C. Then the glass beaker one 2 L, the solution 1 L (AP FO content 0. 49 8 g, 1. 1 6mmo 1) were charged, mixed aqueous solution [A 1 ³ + ions magnesium chloride salt aluminum Concentration 0.0 7 51110 1/1 ^ ^{2 +} ion 0.15mol ZL] about 77.3mL [A1 ³ + Ion total amount 5.8 Ommo and Mg ² + ion total amount 11.6 mmol] were added dropwise over 2 hours. During the dropping, stirring was continued using an anchor blade so that the G value became 100 s- ¹ . During the dropwise addition, a 0.2 N aqueous sodium hydroxide solution was appropriately added dropwise to adjust the pH to 9.8 or more and 10.2 or less.

Immediately after the dropwise addition of the mixed aqueous solution of aluminum chloride and magnesium salt, the extremely thin milky white liquid began to aggregate and began to form a white precipitate. Two hours after the start of the dropwise addition of the mixed aqueous solution, the formation of the precipitate was completed. When the stirring was stopped, the generated precipitate immediately settled out, and almost settled out in about 5 minutes. The precipitate was filtered through a 3 xm membrane filter. The precipitate was dried with filter paper at 70 ° C for 15 hours. The dry mass of the precipitate was 1.05. When the dried precipitate was analyzed by differential thermal mass spectrometry (DTA), infrared absorption spectrum (IR), and XRD, a peak belonging to PFOA and a peak belonging to layered double hydroxide were detected. From this, it was confirmed that this precipitate was PFOA precipitated together with the layered double hydroxide. When the supernatant was analyzed, the concentration of APFO was 2 mass ppm, and therefore, the fixing rate of PFOA from the gas recovered water contained in the layered double hydroxide was 99.6 mass%.

[Example 2]

In Example 1, the aqueous solution in which APTFE was recovered from exhaust gas during drying and heat treatment of the PPTFE powder was 5001111 ^. 500 mL of waste water (containing 2300 mass ppm of SS component, APFO concentration of 148 mass ppm) after coagulation after the emulsion polymerization was mixed. When the APFO concentration in this mixed aqueous solution was analyzed, it was 323 ppm by mass. To this mixed aqueous solution, a 0.2 N aqueous sodium hydroxide solution was added to adjust the pH to 10.0. The liquid temperature was 26 ° C.

Then glass beaker 2 L, the aqueous solution 1L (eight? 0 content 0. 323 g, 0. 749 mm o 1) were charged, mixed aqueous solution of aluminum chloride and magnesium chloride [A 1 ³ + ion concentration 0 . 075mo 1 / L, dropwise over Mg ^{2 +} ions 0. 15m o 1 ZL] of 50. OmL [a 1 ³ + ion amount 3. 75mmo 1, Mg ² + I on total 7. 49mmo 1] for 2 hours did. During the dropwise addition the G value have use an anchor blade was continued stirring such that the 100 s_ ^1. 0.2N hydroxide during dropping An aqueous solution of thorium was added dropwise as appropriate: H was adjusted to 9.8 or more and 10.2 or less. Two hours after the start of the dropwise addition of the mixed aqueous solution, the formation of the precipitate was completed. When the stirring was stopped, the generated precipitate immediately settled, and almost settled in about 5 minutes. The precipitate was filtered through a 3 tm membrane filter. The precipitate was dried with filter paper at 70 ° C for 15 hours. The dry weight of the precipitate was 0.65 g. When the supernatant was analyzed, the concentration of APF〇 was 2 mass ppm, and therefore, the fixing rate of PFO A contained in the layered double hydroxide was 99.4 mass%.

[Example 3]

PTFE powder was agglomerated from an aqueous PTFE dispersion produced by emulsion polymerization using APFO as an emulsifier. This PTFE powder (10.0 kg, water content: 48% by mass) was placed in a hot air circulation oven, heated at a rate of 100 ° C to 5 ° CZ over time, and then heat-treated at 200 for 1 hour. The displacement of the exhaust gas from the hot-air circulation oven was 4.5 Nm ³ / h. The entire amount of the exhaust gas was introduced into a spray tower having a diameter of 50 cm and a height of 500 cm. The linear velocity of the gas at this time was about 0.5 m / sec. In this spray tower, 35 kg of coagulated waste water (SS content: 2300 mass ppm, AP FO concentration: 148 mass ppm) of the PTFE whose pH was adjusted to 10 using sodium hydroxide was circulated and sprayed. APFO was absorbed. Drying of PTFE • After the heat treatment, the concentration of APFO in the aqueous solution in the spray tower was analyzed and found to be 640 mass ppm.

A 0.2 N aqueous sodium hydroxide solution was added to the coagulated wastewater in which the APFO was absorbed to adjust the pH to 10.0. The liquid temperature was 26 ° C. Then the glass-bi one car 2L, the aqueous solution 1L (APFO content 0. 640 g, 1. 48 mm o 1) were charged, mixed aqueous solution of magnesium chloride and aluminum chloride [A 1 ³ + ion concentration 0. 075Mo 1 Bruno, dropwise over Mg ² + ions 0. 15mo l / L] of ^{99. 3 m L [a 1 3} + ion amount 7. 4 Ommo 1, Mg ² + ions total 14. 8mmo 1] for 2 hours did.

During the dropping, stirring was continued using an anchor blade so that the G value became 100 s- ¹ . During the dropwise addition, a 0.2N aqueous sodium hydroxide solution was appropriately added dropwise to adjust the pH to 9.8 or more and 10.2 or less. Dropping of mixed aqueous solution of aluminum chloride and magnesium chloride Immediately after that, a very pale milky liquid began to aggregate and started to form a white precipitate. Two hours after the start of the dropwise addition of the mixed aqueous solution, the formation of the precipitate was completed. When the stirring was stopped, the generated sediment rapidly settled, and almost settled in about 5 minutes. The precipitate was filtered through a 3 zm membrane filter. The precipitate was dried at 70 ° C for 15 hours together with the filter. The dry weight of the precipitate was 1.42 g.

When the dried precipitate was analyzed by differential thermal mass spectrometry (DTA), infrared absorption spectrum (IR), and XRD, peaks belonging to PFOA and peaks belonging to layered double hydroxide were detected. From this, it was confirmed that this precipitate was PFOA precipitated together with the layered double hydroxide. When the supernatant was analyzed, the concentration of AP FO was 2 mass ppm, and therefore, the fixing rate of PFOA from the gas recovery water contained in the layered double hydroxide was 99.7 mass%.

[Example 4]

PTFE powder was agglomerated from a PTFE aqueous dispersion produced by emulsion polymerization using APFO as an emulsifier. 20 kg of this PTFE powder (moisture content: 48% by mass) was placed in a hot air circulation oven, and the temperature was gradually increased from 100 ° C to 5 ° C over time.

Heat treatment was performed at 200 ° C for 1 hour. The displacement of the exhaust gas from the hot-air circulation oven was 1 ONm ³ . The entire amount of this exhaust gas was introduced into a packed column having a diameter of 10 cm and a height of 200 cm. The packed tower was filled with 5/8 inch stainless steel pole rings. The linear velocity of the gas at this time was about 0.3 mZ seconds. In this absorption tower, 70 kg of ion-exchanged water whose pH was adjusted to 10 using potassium hydroxide was circulated at a flow rate of 500 L Zh. Drying of the PTFE powder * After the heat treatment, the APFO concentration in the alkaline water in the packed tower was analyzed and found to be 495 mass ppm.

Ρ H was adjusted to 10.0 by adding a 0.2 N aqueous sodium hydroxide solution to the APFO-containing aqueous solution. The liquid temperature was 26. Then the glass beaker one 2 L, the aqueous solution 1L (APFO content 0. 495 g, 1. 16 mm o 1) were charged, mixed aqueous solution of magnesium chloride and aluminum chloride [A1 ³ + ion concentration 0.0 75mo 1 / L, Mg ² + ions 0. 15mo 1 ZL] of about 76. 8 mL [a 1

³ + ion total amount 5.78 mmo 1, Mg ² + ion total amount 11.55 mmol] were dropped over 2 hours. During the dropping, stirring was continued using an anchor blade so that the G value became 100 s- ¹ . During the dropwise addition, a 0.2 N aqueous sodium hydroxide solution was appropriately added dropwise to adjust the pH to 9.8 or more and 10.2 or less. Immediately after the dropwise addition of the mixed aqueous solution of Shiridani aluminum and Shiridani magnesium, the extremely thin milky white liquid began to aggregate and began to form a white precipitate. Two hours after the start of the dropwise addition of the mixed aqueous solution, the formation of the precipitate was completed. When the stirring was stopped, the generated sediment rapidly settled, and almost settled in about 5 minutes. The precipitate was filtered through a 3 / zm membrane filter. The precipitate was dried with filter paper at 70 ° C for 15 hours. The dry weight of the precipitate was 1.03 g. When the dried precipitate was analyzed by differential thermal mass analysis (DTA), infrared absorption spectrum (IR), and XRD, a peak belonging to PFO A and a peak belonging to layered double hydroxide were detected. From this, it was confirmed that this precipitate was PFOA precipitated together with the layered double hydroxide. When the supernatant was analyzed, the concentration of APFO was 2 mass ppm, and therefore, the fixing rate of PFOA from the gas-recovered water contained in the layered double hydroxide was 99.6 mass%.

According to the method for recovering a fluorinated emulsifier of the present invention, the fluorinated polymer is obtained by emulsion polymerization or aqueous dispersion polymerization in an aqueous medium containing the fluorinated emulsifier. The contained fluorine-containing emulsifier can be efficiently recovered. Further, according to the recovery method of the present invention, together with the fluorinated emulsifier contained in the exhaust gas, a fluorinated monomer or a fluorinated monomer and a monomer other than the fluorinated monomer are added to an aqueous medium containing a fluorinated emulsifier. From the aqueous dispersion of a fluoropolymer obtained by emulsion polymerization or aqueous dispersion polymerization in step (1), which is contained in the wastewater (usually flocculated wastewater) after coagulation and separation of the fluoropolymer by salting out, etc. The emulsifier can also be recovered efficiently.

Claims

The scope of the claims

1. Contacting an exhaust gas (A) containing a fluorinated emulsifier with an aqueous liquid (B1) having a pH of 7 or more and less than 12 to absorb the fluorinated emulsifier in the exhaust gas into the aqueous liquid, A step (X) of obtaining an aqueous liquid (B 2) containing a fluorine emulsifier, a step (Y) of fixing the fluorine-containing emulsifier in the aqueous liquid (B 2) between layers of the layered double hydroxide, and the step (Y) Layered double hydroxide having a fluorine-containing emulsifier fixed between layers obtained in (Y)

A method for recovering a fluorinated emulsifier, comprising: a recovery step (Z) of separating (C) and recovering the fluorinated emulsifier.

2. The method for recovering a fluorinated emulsifier according to claim 1, wherein the aqueous liquid (B1) is wastewater (B3) after separating the fluorinated polymer in the step of producing the fluorinated polymer.

3. Contacting the flue gas (A) containing a fluorinated emulsifier with an aqueous liquid (B1) having a pH of 7 or more and less than 12 to absorb the fluorinated emulsifier in the exhaust gas into the aqueous liquid, A step (X) of obtaining an aqueous liquid (B 2) containing a fluorine emulsifier, mixing the aqueous liquid (B 2) with the waste water (B 3) after separating the fluorine-containing polymer in the step of producing the fluorine-containing polymer (XI), the step (Y) of fixing the fluorinated emulsifier in the mixed aqueous liquid (B4) obtained in the step (XI) between the layers of the layered double hydroxide, and the step (Y). A method for recovering a fluorinated emulsifier, comprising the step of separating a layered double hydroxide (C) having a fluorinated emulsifier fixed between layers and recovering the fluorinated emulsifier.

4. The exhaust gas (A) is an exhaust gas obtained by emulsion polymerization or aqueous dispersion polymerization in an aqueous medium containing a fluorine-containing emulsifier, which is obtained in a drying step of the fluorine-containing polymer, Z or a heat treatment step. 4. The method for recovering a fluorinated emulsifier according to 1, 2, or 3.

5. The method for recovering a fluorinated emulsifier according to claim 1, 2, 3 or 4, wherein the aqueous liquid (B1) is an aqueous liquid whose pH has been adjusted to 7 or more and less than 12 using an alkali.

6. The alkali is sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, sodium hydrogen carbonate, carbonated water 6. The method for recovering a fluorinated emulsifier according to claim 5, which is at least one member selected from the group consisting of raw lime, calcium bicarbonate, and ammonia.

7. The fluoropolymer is a polytetrafluoroethylene, a tetrafluoroethylene / ethylene copolymer, a tetrafluoroethylene propylene copolymer, a tetrafluoroethylene Z-propylene a Z-vinylidene fluoride copolymer And at least one member selected from the group consisting of tetrafluoroethylene / propylene hexafluoride copolymer, tetrafluoroethylene / tetrafluoroethylene ZCF ₂ = CFO (CF ₂ ) 2 CF ₃ copolymer and polyvinylidene fluoride 7. The method for recovering a fluorinated emulsifier according to any one of the ranges 2 to 6.

8. Recovery of the fluorine-containing emulsifier according to any one of claims 2 to 7, wherein the wastewater (B3) is a wastewater in which the content of suspended solids and substances that can be suspended solids is 10% by mass or less. Method.

9. The fluorinated emulsifier has 5 to 13 carbon atoms and may contain an etheric oxygen atom in the molecule. Perfluoroalkanoic acid, ω-hydroperfluoroalkanoic acid, ω-chloroper The method for recovering a fluorinated emulsifier according to any one of claims 1 to 8, wherein the method is at least one kind of a salt of an acid selected from the group consisting of fluoroalkanoic acid and perfluoroalkanesulfonic acid.

10. In the step (X), when the fluorinated emulsifier in the exhaust gas (Α) is absorbed into the aqueous liquid (Β1), a droplet type absorption device and a Ζ or liquid film type absorption device are used. The method for recovering a fluorinated emulsifier according to any one of ranges 1 to 9.