JP2003212922A - Method for recovering fluorine-containing emulsifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recovering the fluorine-containing emulsifier from the polymerization wastewater left after the production of a fluoropolymer. <P>SOLUTION: The method for recovering the fluorine-containing emulsifier comprises forming a layered double hydroxide by adding an aqueous mixture of a mixture containing divalent metal ions and trivalent metal ions while keeping an aqueous solution at such a pH that the divalent metal ions and the trivalent metal ions forms a hydroxide to an aqueous solution of sodium hydroxide and/or potassium hydroxide, adjusting the polymerization wastewater left after the removal of the fluoropolymer obtained by polymerizing at least one fluoro monomer in an aqueous medium containing the fluorine-containing emulsifier, containing the fluorine-containing emulsifier, and having a content of an suspended solid component and a substance convertible into a suspended solid component of at most 1 mass% to a pH approximately in the range in which the layered double hydroxide has been formed, adding the layered double hydroxide to the wastewater after the pH adjustment to form a layered double oxide containing the fluorine-containing emulsifier among the layers, separating the layered double hydroxide from the wastewater, and recovering the fluorine- containing emulsifier. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for recovering a fluorine-containing emulsifier using a layered double hydroxide.

[0002]

2. Description of the Related Art Anionic emulsifiers having a perfluoro chain as a main component are used as an essential material for production processes in many fields such as emulsion polymerization process of fluoropolymers such as polytetrafluoroethylene and manufacturing process of electronic parts industry. It is widely used as a material for various paints, coating agents, fire extinguishing agents, etc., but when it is discharged from the production process, it is often a dilute aqueous solution with an emulsifier concentration of several mass% to several hundred mass ppm. , Making efficient recovery on an industrial scale difficult. Further, because of the dilute solution, the problem of fixing and recovering this emulsifier has hardly been recognized in the past. Moreover, the fluorine-based compound such as the anionic emulsifier is a compound which is difficult to be treated by the activated sludge treatment which is generally used as the wastewater treatment. However, in recent years, there has been a strong demand for harmony of chemical substances with respect to the environment and the ecosystem, and with respect to this fluorine compound as well, the need for a technology for closing the system by recovering and regenerating it has been strongly recognized.

Conventionally, a method of using an anion exchange resin (hereinafter referred to as IER) is known as a method of recovering a fluorine-containing emulsifier used for emulsion polymerization of a fluoropolymer. For example, Japanese Examined Patent Publication No. 47-51233 describes a method of aggregating and washing emulsion-polymerized latex, collecting an emulsifier as an aqueous solution, concentrating and collecting the fluorine-containing emulsifier with an organic solvent. Also describes a method for recovering the fluorinated emulsifier using IER. U
For SP4282162, dilute emulsifier aqueous solution to pH 0
A method is described in which the emulsifier is adsorbed in a range of 7 and weakly basic IER is brought into contact therewith, and desorption is carried out with aqueous ammonia. In WO99 / 62830, nonionic or cationic surfactant is added to the aggregated wastewater of the fluoropolymer, and polytetrafluoroethylene (hereinafter referred to as PTF) in the aggregated wastewater is added.
It is called E. ) A method for stabilizing fine particles and preventing clogging of the packed column of the IER is described.

JP-A-55-120630, USP
5312935 and DE 2908001 include PTF
Concentrate the coagulated wastewater of E by the ultrafiltration method as well as PTFE
A method for recovering a part of ammonium perfluorooctanoate (hereinafter referred to as APFO) used for production and then adsorbing and recovering APFO by IER is described. JP-A-55-104651, US Pat. No. 4,282,162 and DE2903981 disclose a method of adsorbing APFO on IER and then desorbing and recovering perfluorooctanoic acid using a mixture of an acid and an organic solvent. In WO 99/62858, lime water is added to the aggregated wastewater of tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer (hereinafter referred to as PFA) in advance to adjust the pH to 6 to 7.5, and then aluminum chloride. ,
After adding a metal salt such as iron chloride to agglomerate unaggregated PFA, and then mechanically separating and removing the agglomerates, the pH of the resulting wastewater is adjusted to 7 or less with sulfuric acid, and strongly basic IE
A method of adsorbing and recovering a fluorine-containing emulsifier using R is described. Japanese Patent Laid-Open No. 2001-62313 discloses that a fluorine-containing emulsifier adsorbed on an ion exchange resin is treated with water, an alkali,
A method of desorption using a mixture of organic solvents is described.

At the 76th Annual Meeting of the Chemical Society of Japan and the 80th Annual Meeting of the Chemical Society of Japan, a technique for inserting and fixing perfluorooctanoic acid and its ammonium salt using a layered double hydroxide of aluminum and zinc is proposed. It has been reported.

However, in the method using IER, IE
Floating solids or substances that can become floating solids, including non-agglomerated fluoropolymers before contact with R (hereinafter SS
Component) will be highly removed, and this removal of the SS component not only has a great influence on the recovery efficiency of the fluorine-containing emulsifier, but also a simple and highly efficient method for highly removing the SS component. Many problems remain in the actual operation, such as the removal method not found.

Further, in the insertion fixing method using the layered double hydroxide reported at the 76th Annual Meeting of the Chemical Society of Japan and the 80th Annual Meeting of the Chemical Society of Japan, only perfluorooctanoic acid and its ammonium salt are dissolved. However, there is no known report showing the actual recovery using the coagulated waste water of the actual fluoropolymer containing other contaminants, although only the technique using the aqueous solution was shown.

[0008]

DISCLOSURE OF THE INVENTION In order to reduce the load of the fluorine-containing emulsifier on the environment and the ecosystem and to effectively utilize it as a resource, the present invention provides a fluorine-containing emulsifier by stable and easy adsorption and fixation. It is an object of the present invention to provide a technique for recovering the fluorine-containing emulsifier from the contained wastewater easily and in high yield.

[0009]

That is, the gist of the present invention is to provide an aqueous solution of sodium hydroxide and / or potassium hydroxide with a pH of the aqueous solution containing hydroxides of divalent metal ions and trivalent metal ions. A layered double hydroxide is produced by adding a mixed aqueous solution containing a divalent metal ion and a trivalent metal ion while maintaining the formation range, and then at least one kind of the compound is added in an aqueous medium containing a fluorine-containing emulsifier. A wastewater after separating a fluoropolymer obtained by polymerizing a fluorine-containing monomer, containing the fluorine-containing emulsifier, and containing 1 mass% or less of a suspended solid content and a substance that can be a suspended solid content. By adjusting the pH of the wastewater is the same range as when the layered double hydroxide was produced, by adding the layered double hydroxide-containing aqueous solution to the pH-adjusted wastewater, Forming a layered double hydroxide containing containing emulsifier in layers, the layers were separated shaped double hydroxide from exhaust water,
A method for recovering the fluorine-containing emulsifier is characterized by recovering the fluorine-containing emulsifier.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A layered double hydroxide is a double hydroxide obtained by simultaneously precipitating a divalent metal salt and a trivalent metal salt as hydroxides, and is formed between layers formed. The molecule or anion can be immobilized by encapsulating the molecule or anion. Layered double hydroxides are trivalent metals and 2
If the forming pH of the hydroxide is overlapped with the valent metal, or if the pH range of forming the hydroxide is close, it can be formed by simultaneously precipitating as a hydroxide. The divalent metal ions include beryllium, cadmium, cobalt, chromium, copper, iron, magnesium, manganese, nickel,
Examples of the metal ions include lead, platinum, palladium, zinc, tin, calcium, and the like. Examples of the trivalent metal ions include aluminum, bismuth, cerium, chromium, iron, gallium, indium, manganese, titanium, thallium, cobalt, lanthanum, and scandium. Ions of metals such as In the present invention, the metal forming the layered double hydroxide is preferably magnesium and / or zinc ion as the divalent metal ion because it does not adversely affect the environment or ecosystem and is easily available. , And magnesium ion is more preferable. Aluminum ions are preferably used as the trivalent metal ions. Hereinafter, the case of using these preferable divalent metal ions and trivalent metal ions will be described.

Generally, three methods of adsorption of anions by layered double hydroxide are coprecipitation method, ion exchange method and reconstruction method.
Although various types are known, the ion exchange method is used in the present invention. Ion exchange method, for example, chloride ions, hydroxide ions, carbonate ions and the like are preliminarily formed into a layered double hydroxide having a structure in which the layers of the layered double hydroxide are included, and the layered double hydroxide is In this method, the target anion is added to a solution in which the target anion is dissolved, and the target anion is encapsulated between the layers in a form of replacing the anion already encapsulated.

In the present invention, first, an aqueous solution of sodium hydroxide and / or potassium hydroxide is prepared by adjusting the pH of the aqueous solution to a trivalent metal ion such as aluminum ion and a divalent metal ion such as magnesium ion and zinc ion. While maintaining the range of forming a hydroxide, a layered double hydroxide is produced by adding a mixed aqueous solution containing the divalent metal ion and the trivalent metal ion. In the present invention, magnesium ion, zinc ion, and aluminum ion may be used with any raw material, but the following raw materials are preferable from the viewpoint of easy availability. Among the magnesium ion and the zinc ion, the magnesium ion is preferable.

As a raw material of magnesium ion, magnesium chloride, magnesium chloride hexahydrate, magnesium nitrate hexahydrate, magnesium nitrate, magnesium oxide,
It is preferable to use magnesium sulfate, magnesium sulfate heptahydrate and magnesium carbonate, and magnesium chloride and magnesium chloride hexahydrate are particularly preferable. As the zinc ion raw material, zinc chloride, zinc nitrate hexahydrate, zinc oxide, zinc sulfate, zinc sulfate heptahydrate are preferably used, and zinc chloride is particularly preferable. The aluminum ion is preferably aluminum chloride, aluminum chloride hexahydrate, aluminum sulfate or aluminum nitrate, more preferably aluminum chloride or aluminum chloride hexahydrate.

In the present invention, when the layered double hydroxide is formed, the pH of the aqueous solution is changed to aluminum hydroxide and magnesium and / or zinc ion to form a hydroxide in an aqueous solution of sodium hydroxide and / or potassium hydroxide. It is necessary to add a mixed aqueous solution containing magnesium and / or zinc ions and aluminum ions while maintaining the range. The pH range is preferably 9 or more and 11 or less when aluminum and magnesium are used, and 6 or more and 9 or less when aluminum and zinc ions are used. When using three components of aluminum ion, magnesium ion, and zinc ion, the pH range is preferably 6 or more and 11 or less. Molar ratio of aluminum ion and divalent metal ion in a mixed aqueous solution containing magnesium and / or zinc ion and aluminum ion (molar ratio of trivalent ion and divalent ion in layered double hydroxide formed) Is from 3: 1
1: 3 is preferable, and 1: 1 to 1: 2 is more preferable.

In forming the layered double hydroxide, aluminum ions and divalent metal ions in an aqueous solution of sodium hydroxide and / or potassium hydroxide after addition of a mixed aqueous solution containing magnesium and / or zinc ions and aluminum ions. The concentration of each is 0.01m
It is preferably not less than ol / L and not more than 2 mol / L.
Here, the concentration of the divalent metal ion is the concentration when magnesium or zinc ions are added, and the total concentration when both are added. When the concentration of aluminum ions and divalent metal ions is less than 0.01 mol / L, the amount of water increases when the layered double hydroxide is formed, and as a result, when added to the wastewater containing the fluorine-containing emulsifier, The concentration of the fluorine-containing emulsifier tends to decrease, and the recovery efficiency tends to decrease. The concentration of the above ions is 2mo
When it exceeds 1 / L, the metal ion aqueous solution is acidic, and therefore when the layered double hydroxide is formed, a part of the layered double hydroxide-containing aqueous solution is locally added by adding the metal ion aqueous solution. When the pH is out of the optimum range for forming the layered double hydroxide, it becomes difficult for the metal ions to be effectively used for forming the layered double hydroxide. However, even if a metal ion aqueous solution having a concentration outside the above-mentioned concentration range is temporarily added, if a metal ion aqueous solution having an appropriate concentration range is added again, then the layered double hydroxide can be synthesized thereafter.

In the present invention, the fluorine-containing emulsifier contained in the wastewater to be treated has 5 to 13 carbon atoms.
Are preferable salts of perfluoroalkanoic acid, ω-hydroperfluoroalkanoic acid, ω-chloroperfluoroalkanoic acid, perfluoroalkanesulfonic acid and the like, and these may have a linear structure, a branched structure or a mixture thereof. Further, an etheric oxygen atom may be contained in the molecule. Within the range of this number of carbon atoms, the action and effect as an emulsifier is excellent. As the acid salt, a lithium salt,
Alkali metal salts or ammonium salts such as sodium salts and potassium salts are preferred, ammonium salts or sodium salts are more preferred, and ammonium salts are most preferred.

Specific examples of the acid include perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid (hereinafter referred to as PFOA), perfluorononanoic acid, perfluorodecanoic acid, perfluorododecanoic acid and ω-hydroperfluoro. Heptanoic acid, ω-hydroperfluorooctanoic acid, ω-
Hydroperfluorononanoic acid, ω-chloroperfluoroheptanoic acid, ω-chloroperfluorooctanoic acid, ω-
Chloroperfluorononanoic acid, etc. CF ₃ CF ₂ CF ₂ OC
F (CF ₃ ) COOH, CF ₃ CF ₂ CF ₂ OCF (C
F ₃ ) CF ₂ OCF (CF ₃ ) COOH, CF ₃ CF ₂ CF _{2
O [CF (CF 3) CF} 2 O] 2 CF (CF 3) COOH,
CF ₃ CF ₂ CF ₂ O [CF (CF ₃ ) CF ₂ O] ₃ CF (C
F ₃ ) COOH, CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ OCF (C
F ₃ ) COOH, perfluorohexanesulfonic acid,
Perfluoroheptanesulfonic acid, perfluorooctanesulfonic acid, perfluorononanesulfonic acid, perfluorodecanesulfonic acid and the like can be mentioned.

Specific examples of ammonium salts include perf
Ammonium uropentanoate, perfluorohexane
Ammonium acid, Ammonium perfluoroheptanoate
System, APFO, ammonium perfluorononanoate,
Ammonium lufluorodecanoate, perfluorododeca
Ammonium acid, ω-hydroperfluoroheptanoic acid
Ammonium, ω-hydroperfluorooctanoic acid
Monium, ω-hydroperfluorononanoic acid ammoniu
Ammonium, ω-chloroperfluoroheptanoate ammonium,
ω-ammonium chloroperfluorooctanoate, ω-
CF such as ammonium chloroperfluorononanoate₃C
F₂CF₂OCF (CF₃) COONH_Four, CF₃CF₂CF
₂OCF (CF ₃) CF₂OCF (CF₃) COONH_Four,
CF₃CF₂CF₂O [CF (CF₃) CF ₂O]₂CF (C
F₃) COONH_Four, CF₃CF₂CF₂O [CF (CF₃)
CF₂O]₃CF (CF₃) COONH_Four, CF₃CF₂CF
₂CF₂CF₂OCF (CF₃) COONH_FourEtc., Perfuru
Ammonium orohexanesulfonate, perfluoro
Ammonium butane sulfonate, perfluorooctane
Ammonium sulfonate, perfluorononane sulfone
Ammonium acid, perfluorodecane sulfonic acid ammo
And the like.

Specific examples of the lithium salt include lithium perfluoropentanoate, lithium perfluorohexanoate, lithium perfluoroheptanoate, lithium perfluorooctanoate, lithium perfluorononanoate, lithium perfluorodecanoate, lithium perfluorododecanoate, and ω-hydroperfluoro. Lithium heptanoate, ω-lithium hydroperfluorooctanoate, ω-
Lithium hydroperfluorononanoate, lithium ω-chloroperfluoroheptanoate, lithium ω-chloroperfluorooctanoate, lithium ω-chloroperfluorononanoate, etc. CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) COOL
i, CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF (C
F ₃ ) COOLi, CF ₃ CF ₂ CF ₂ O [CF (CF ₃ )
CF ₂ O] ₂ CF (CF ₃ ) COOLi, CF ₃ CF ₂ CF _{2
O [CF (CF 3) CF} 2 O] 3 CF (CF 3) COOL
_{i, CF 3 CF 2 CF 2} CF 2 CF 2 OCF (CF 3) COO
Examples thereof include Li, lithium perfluorohexane sulfonate, lithium perfluoroheptane sulfonate, lithium perfluorooctane sulfonate, lithium perfluorononane sulfonate, lithium perfluorodecane sulfonate, and the like.

Specific examples of the sodium salt include sodium perfluoropentanoate, sodium perfluorohexanoate, sodium perfluoroheptanate, sodium perfluorooctanoate, sodium perfluorononanoate, sodium perfluorodecanoate, sodium perfluorododecanoate, and ω-hydroperfluoro. Sodium heptanoate, sodium ω-hydroperfluorooctanoate, sodium ω-hydroperfluorononanoate, sodium ω-chloroperfluoroheptanoate,
Sodium ω-chloroperfluorooctanoate, sodium ω-chloroperfluorononanoate, etc., CF ₃ CF ₂ C
_{F 2 OCF (CF 3) COONa} , CF 3 CF 2 CF 2 OC
F (CF ₃ ) CF ₂ OCF (CF ₃ ) COONa, CF ₃ C
F ₂ CF ₂ O [CF (CF ₃ ) CF ₂ O] ₂ CF (CF ₃ ) C
_{OONa, 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 ) COONa and the like, sodium perfluorohexane sulfonate, sodium perfluoroheptane sulfonate, sodium perfluorooctane sulfonate, sodium perfluorononane sulfonate, sodium perfluorodecane sulfonate and the like can be mentioned.

Specific examples of the potassium salt include potassium perfluoropentanoate, potassium perfluorohexanoate, potassium perfluoroheptanate, potassium perfluorooctanoate, potassium perfluorononanoate, potassium perfluorodecanoate, potassium perfluorododecanoate, and ω-hydroperfluoro. Potassium heptanoate, ω-potassium hydroperfluorooctanoate, ω-
Potassium hydroperfluorononanoate, potassium ω-chloroperfluoroheptanoate, potassium ω-chloroperfluorooctanoate, potassium ω-chloroperfluorononanoate, etc. CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) COO
K, CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF (C
F ₃ ) COOK, CF ₃ CF ₂ CF ₂ O [CF (CF ₃ ) C
F 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, C
_{F 3 CF 2 CF 2 CF 2} CF 2 OCF (CF 3) COOK , etc.,
Examples thereof include potassium perfluorohexanesulfonate, potassium perfluoroheptanesulfonate, potassium perfluorooctanesulfonate, potassium perfluorononanesulfonate, potassium perfluorodecanesulfonate, and the like.

As the fluorine-containing emulsifier in the present invention, an ammonium salt of perfluoroalkanoic acid having 6 to 12 carbon atoms is particularly preferable, and ammonium perfluoroheptanoate, APFO, ammonium perfluorononanoate or ammonium perfluorodecanoate is more preferable, APFO is most preferred.

In the present invention, the wastewater after polymerization of the fluoropolymer means the wastewater after separating the fluoropolymer obtained by polymerizing at least one fluoromonomer in an aqueous medium containing a fluorine-containing emulsifier. In general, the coagulation drainage of the fluoropolymer after the emulsion polymerization is preferable, and the coagulation drainage from the manufacturing process of the (co) polymer of the fluoromonomer or the copolymer of the fluoromonomer and the monomer other than the fluoromonomer. Is particularly preferable. Specifically,
The coagulated wastewater from the production process is a fluorine-containing polymer obtained by emulsion-polymerizing or aqueous-dispersion-polymerizing a fluorine-containing monomer or a monomer other than the fluorine-containing monomer and a monomer other than the fluorine-containing monomer in an aqueous medium containing a fluorine-containing emulsifier. It refers to the waste water after the fluoropolymer is aggregated from the aqueous dispersion by salting out and the fluoropolymer is separated and removed. The waste water contains the fluorine-containing emulsifier used at the time of polymerization of the fluorine-containing monomer, and also contains SS components such as unaggregated fluorine-containing polymer. Hereinafter, the coagulated waste water will be described as a typical example.

As the fluorine-containing monomer, tetrafluoroethylene (hereinafter referred to as TFE), CF ₂ ═CFCl, C
FH = CF ₂ , CFH = CH ₂ , fluoroethylene such as vinylidene fluoride (hereinafter referred to as VdF); hexafluoropropylene (hereinafter referred to as HEP), CF ₂ =
Fluoropropylene such as CHCF ₃ ; CF ₂ = CFOCF
₃ , CF ₂ ═CFO (CF ₂ ) ₂ CF ₃ (hereinafter referred to as PPVE), CF ₂ ═CFO (CF ₂ ) ₄ CF _{3 and} other perfluorovinyl ethers having 3 to 10 carbon atoms; CH ₂ ═C
Examples thereof include (perfluoroalkyl) ethylene having 4 to 10 carbon atoms such as H (CF ₂ ) ₃ CF ₃ . These fluorine-containing monomers may be used alone or in combination of two or more. Of these, those containing TFE are preferable, and TFE alone and TFE / propylene are particularly preferable.

As the monomers other than the fluorine-containing monomer, vinyl acetate such as vinyl acetate; vinyl ether such as ethyl vinyl ether, cyclohexyl vinyl ether and hydroxybutyl vinyl ether; norbornene,
Examples thereof include monomers having a cyclic structure such as norbornadiene; allyl ethers such as methyl allyl ether; olefins such as ethylene, propylene and isobutylene. Monomers other than the fluorine-containing monomer may be used alone or in combination of two or more kinds.

In the present invention, as the fluorine-containing polymer, PTFE, TFE / propylene copolymer (hereinafter referred to as T
It is called FE / P copolymer. ), TFE / propylene / V
Examples thereof include dF copolymer (hereinafter referred to as TFE / P / VdF copolymer), TFE / HFP copolymer, TFE / PPVE copolymer, TFE / ethylene copolymer, and polyvinylidene fluoride. More preferably, PTFE and TF
E / P copolymer, TFE / P / VdF copolymer or TF
E / PPVE copolymer, most preferably PTF
E, a TFE / P copolymer.

In the present invention, the coagulated wastewater of the fluoropolymer has a pH of the wastewater in the pH range at the time of forming the layered double hydroxide, that is, 6 or more and 9 or less when aluminum ion and zinc ion are used. , 9 or more when using aluminum ion and magnesium ion 1
1 or less, and in the case of a double hydroxide using three ions of aluminum, magnesium and zinc, it is adjusted to 6 or more and 11 or less. If the coagulated wastewater is alkaline, it may be adjusted by adding hydrochloric acid and / or sulfuric acid and / or nitric acid,
If it is acidic, it may be adjusted by adding potassium hydroxide and / or sodium hydroxide. When the pH is out of the above range, aluminum ions and zinc ions, or aluminum ions and magnesium ions independently form hydroxides to form aluminum hydroxide, zinc hydroxide and magnesium hydroxide. It becomes difficult to form a hydroxide, and as a result, the recovery efficiency of the fluorine-containing emulsifier tends to decrease.

In the present invention, the concentration of the fluorine-containing emulsifier, which is the object of recovery, is preferably 1 mass ppm or more and 10 mass% or less, more preferably 10 mass ppm or more and 1 mass% or less, and particularly 50 mass ppm or more and 0.5 mass%. % Or less is preferable. If the concentration of the fluorine-containing emulsifier is lower than this, the efficiency of capturing the fluorine-containing emulsifier by the layered double hydroxide in the recovery liquid is likely to decrease. When the concentration is higher than this, a simpler and more efficient method such as precipitating the fluorine-containing emulsifier by changing pH can be used.

The suspended solids such as the non-agglomerated fluoropolymer fine particles contained in the coagulated waste water or the substance (SS component) capable of becoming the suspended solids does not adversely affect the recovery and recovery rate of the fluorine-containing emulsifier, but is generated. Since it may interfere with the regeneration of the fluorine-containing emulsifier from the prepared layered double hydroxide, 1% by mass before the formation of the layered double hydroxide
It is necessary to be below, preferably 0.3% by mass or less,
In particular, it is preferable to remove up to 0.05 mass% or less. In addition, as a substance which can be a floating solid content, a metal salt used for salting-out and aggregation of the fluoropolymer and / or
Alternatively, a substance that precipitates when the pH of the aggregated wastewater changes and / or a substance that deposits when the temperature of the aggregated wastewater decreases or rises can be used. The explanation below is S
The S component is used as a typical example. Salting out with a metal salt containing a polyvalent metal cation is effective as a method for removing the non-aggregated polymer. Specific examples of the metal salt used for salting out include aluminum chloride, polyaluminum chloride, ferrous chloride, and ferric chloride. Aggregates resulting from salting out may precipitate in a state containing APFO.
It is preferable to redissolve APFO from the aggregate in water by adding sodium hydroxide and / or potassium hydroxide to adjust the pH of the wastewater containing the aggregate to 7 or more.

In the present invention, a general solid-liquid separation method can be adopted as a method for removing the aggregate of the SS component aggregated by adding the above-mentioned metal salt to the aggregated wastewater, in particular, filtration, decantation, It is more preferable to use at least one method selected from the group consisting of centrifugation and thickener. Filtration is also preferably carried out under pressure. It is preferable to remove the aggregates by allowing the waste water containing the aggregates to stand, allowing the aggregates to settle, and filtering the supernatant. In addition, a thickener or a screw decanter is most preferable from the viewpoint of facility maintenance and the like.

The amount of the layered double hydroxide added to the coagulated waste water is such that the trivalent ions in the layered double hydroxide are 1 mole times or more and 30 mole times or less, and divalent, with respect to the fluorine-containing emulsifier. Ions are 1 mole times or more with respect to the fluorine-containing emulsifier 60
It is preferably not more than the molar amount. If the addition amount of the layered double hydroxide is less than the above, the recovery rate of the fluorine-containing emulsifier is insufficient, and if it is more than the above, the concentration of the fluorine-containing emulsifier is relatively lowered due to the addition of a large amount of aqueous solution, and the recovery is performed. It is difficult for the rate to be high enough. Further, the excessive use of the layered double hydroxide,
Because of the metal components contained, it is not preferable from the viewpoint of increasing the load of the final wastewater treatment process.

In the present invention, when the layered double hydroxide-containing aqueous solution is added to the fluorine-containing emulsifier-containing aggregated wastewater, the fluorine-containing emulsifier-containing aggregated wastewater is preferably stirred. The stirring method is not particularly limited, but it is preferable that the generated aggregate particles are not mechanically broken by stirring. The stirring blade of such a stirring device is preferably a stirring blade capable of uniformly mixing the entire drainage at low speed rotation,
One selected from the group consisting of full-zone blades, Maxblend blades or anchor blades is preferable. The G value at the time of stirring by the stirring blade is preferably 1 to 300, more preferably 5 to 250, and most preferably 10 to 200. here,
The G value is a value derived by the following formula.

[0033]

[Equation 1]

Here, P is the stirring power (W), V is the liquid volume (m ³ ), η is the liquid viscosity coefficient (Pa · S), and g _c is the conversion coefficient (kgm / kg sec ³ ).

During the dropping of the metal ion aqueous solution, in order to remove carbonate ions and / or carbon dioxide gas present in the system,
It is preferable to perform bubbling with an inert gas such as nitrogen gas or argon gas, or to expel carbonate ions and / or carbon dioxide gas with an inert gas and then seal the reaction vessel. This is because the layered double hydroxide reacts with carbonate ions, and the binding force between carbonate ions and the layered double hydroxide is high, which hinders the recovery of the fluorine-containing emulsifier. Flow rate of the inert gas is preferably ^{0.1Nm 3 / m 3 · h~10Nm 3} / m 3 · h in the case of performing the ^{bubbling, 0.1Nm 3 / m 3 · h~5Nm} 3 / m 3 · h is More preferable. If the gas flow rate is lower than this, the carbonate ions and / or carbon dioxide gas in the system will not be removed sufficiently. This is not preferable because the temperature of is lowered. The water temperature during the reaction is preferably 10 ° C. or higher and 50 ° C. or lower. If the water temperature is below or above the above range, the formation of layered double hydroxide will be reduced. In particular, the recovery rate at water temperature below the above range is significantly reduced,
The reactor is preferably equipped with a heating device.

Thus, in the coagulated waste water, a layered double hydroxide containing a fluorine-containing emulsifier between the layers is produced. Therefore, the generated layered double hydroxide is separated from the coagulated waste water to recover the fluorine-containing emulsifier. can do.
As a method for separating the layered double hydroxide from the aggregated wastewater,
Well-known solid-liquid separation methods can be appropriately used, and it is particularly preferable to use at least one method selected from the group consisting of filtration, decantation, centrifugation and thickener. Filtration is also preferably carried out under pressure.
Recovery of the fluorine-containing emulsifier from the layered double hydroxide containing a fluorine-containing emulsifier between layers, for example, a method of dissolving this layered double hydroxide in mineral acid, and extracting the fluorine-containing emulsifier using a fluorine-containing hydrocarbon. Can be adopted. Examples of the mineral acid used for dissolving the layered double hydroxide include hydrochloric acid, sulfuric acid, and nitric acid. As the fluorine-containing hydrocarbon used for extracting the fluorine-containing emulsifier, those having 2 or 3 carbon atoms and containing at least one hydrogen atom and at least one fluorine atom are preferable, and trifluorodichloroethane, fluoro Examples thereof include dichloroethane, pentafluoropropane, pentafluorodichloropropane and the like.

The method for recovering the fluorine-containing emulsifier of the present invention comprises:
Not only the fluorine-containing emulsifier, but also trifluoroacetic acid,
It is also applicable to low molecular weight fluorine-containing carboxylic acids such as pentafluoropropanoic acid and / or salts thereof, trifluoromethanesulfonic acid and / or salts thereof, and the like.

[0038]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited thereto. In addition, APF
The concentration of O, PFOA or sodium perfluorooctanoate was measured by a high performance liquid chromatography-mass spectrometry method using a mixed solution of methanol and water as a solvent. The species detected by this method is perfluorooctanoate (C ₇ F ₁₅ COO ⁻ ).

[Measurement of SS component in waste water (unit: mass%)] 10 g of the coagulated waste water after coagulating and separating PTFE from the aqueous dispersion of PTFE was used as a halogen-type moisture meter HR.
-73 (trade name, manufactured by METTLER TOLEDO), 200
The evaporation residue after drying at ℃ until the mass becomes constant is S
S component.

[Example 1] (without Al / Mg and PTFE removed) A glass beaker having an internal volume of 500 mL was charged with ion-exchanged water 1
Add 00mL and p with 0.2N sodium hydroxide solution.
The H was adjusted to 10. Aqueous solution of aluminum chloride and magnesium chloride [Al ³⁺ ion concentration 0.075
mol / L, Mg ²⁺ ion 0.15 mol / L] about 2
2.9 mL [Al ³⁺ ion total amount 1.72 mmol, Mg
²⁺ ion total amount 3.43 mmol] was added dropwise over 2 hours. During the dropwise addition of the mixed aqueous solution, nitrogen gas of 1 Nm ³ / m ³ /
The diluted sodium carbonate aqueous solution was bubbled at a constant flow rate of h to remove dissolved carbonate ions and carbon dioxide gas in the aqueous solution. During the dropping, stirring was continued using an anchor blade so that the G value became 100. In addition, nitrogen gas of 1 Nm ³ / m ³ · h
Bubbling from the bottom of the beaker at a speed of. During the dropping, a 0.2N sodium hydroxide aqueous solution was appropriately dropped to adjust the pH to 9.8 or more and 10.2 or less. Immediately after the addition of the mixed aqueous solution of aluminum chloride and magnesium chloride, a white precipitate started to form. The generation of the precipitate was completed 2 hours after the start of the dropwise addition of the mixed aqueous solution. When the stirring was stopped, the generated precipitate slowly settled.

Aggregated waste water after the emulsion polymerization of PTFE whose pH was adjusted to 10.0 by adding a 0.2 N sodium hydroxide aqueous solution (SS component: 2300 ppm, APFO concentration: 1
(48 ppm), an aqueous solution containing this precipitate was added over 30 minutes. During addition, G value is 100 using anchor blades
Stirring was continued. After the addition is complete, stop stirring,
The precipitate was filtered with a 3 μm membrane filter. This precipitate was dried together with filter paper at 70 ° C. for 15 hours. The dry weight of the precipitate was 2.40 g. The dried precipitate was subjected to differential thermogravimetric analysis (DTA), infrared absorption spectrum (IR),
When analyzed by XRD, peaks attributed to PTFE and peaks attributed to layered double hydroxide, and further to PFOA
A weak peak attributed to was detected. From this, it was confirmed that this precipitate was a precipitate of PTFE and PFOA together with the layered double hydroxide. Analysis of the supernatant revealed a concentration of APFO of 65 ppm,
The fixing rate of PFOA contained in the layered double hydroxide is 56.1.
%Met.

[Example 2] (Al-Mg system, removal of PTFE) 0.130 g in 2 L of PTFE coagulated waste water similar to Example 1
Of aluminum chloride hexahydrate was added, and the mixture was allowed to stand for 30 minutes and only the supernatant of the aggregated wastewater was used to remove unaggregated PTFE particles in the wastewater. After standing for 30 minutes,
The SS component of the supernatant of the coagulated waste water was 20 ppm. The APFO concentration in the supernatant was 141 ppm. 100 mL of ion-exchanged water was placed in another glass beaker having an inner volume of 500 mL, and the pH was adjusted to 10.0 with a 0.2N sodium hydroxide aqueous solution. A mixed aqueous solution of aluminum chloride and magnesium chloride was added thereto [Al ³⁺ ion concentration 0.075 mol / L, Mg ²⁺ ion 0.15 mol
/ L] Approximately 21.8 mL [Al ³⁺ ion total amount 1.64 mm
ol, total amount of Mg ²⁺ ions 3.27 mmol] was added dropwise over 2 hours. While dropping, the G value is 10 using the anchor blade.
Stirring was continued until it reached 0. In addition, nitrogen gas is 1 Nm
Bubbling was performed from the bottom of the beaker at a speed of ³ / m ³ · h. During the dropping, a 0.2N sodium hydroxide aqueous solution was appropriately dropped to adjust the pH to 9.8 or more and 10.2 or less. Immediately after the addition of the mixed aqueous solution of aluminum chloride and magnesium chloride, white precipitates, which were layered double hydroxides of aluminum and magnesium, began to form. The generation of the precipitate was completed 2 hours after the start of the dropwise addition of the mixed aqueous solution. When the stirring was stopped, the generated precipitate slowly settled.

This layered double hydroxide-containing aqueous solution was added to the above S
The SFO-removed APFO-containing PTFE coagulated waste water was added over 10 minutes. G value is 1 using the anchor wing during addition
Stirring was continued until it became 00. After the addition was completed, the stirring was stopped, and the precipitate was collected by filtration with a 3 μm membrane filter. This precipitate was dried together with filter paper at 70 ° C. for 15 hours.
The dry weight of the precipitate was 2.40 g. The dried precipitate was subjected to differential thermogravimetric analysis (DTA), infrared absorption spectrum (I
R) and XRD, the peaks attributed to PTFE and the layered double hydroxide, and P
A weak peak attributed to FOA was detected. From this, it was confirmed that this precipitate was a precipitate of PTFE and PFOA together with the layered double hydroxide. When the supernatant was analyzed, the concentration of APFO was 65 ppm. Therefore, the fixing ratio of PFOA contained in the layered double hydroxide was 5 ppm.
It was 3.9%.

[Example 3] Instead of coagulated waste water after PTFE polymerization, coagulated waste water of TFE / HFP / VdF ₂ copolymer (SS component 530 ppm, APFO content 580 pp)
The same operation as in Example 1 was performed except that m) was used. APF from 1 L of this aggregated wastewater (APFO 0.580 g)
The mixed aqueous solution of aluminum chloride and magnesium chloride [Al ³⁺ ion concentration 0.075 mol / L, Mg ²⁺ ion 0.15 mol / L] used for forming the layered double hydroxide used for O 2 recovery was 89. It was 7 mL. AP
The APFO concentration in the aqueous solution after removing the precipitate of the FO-containing layered double hydroxide was 68 ppm, and the APFO recovery rate was 88.3%.

Comparative Example 1 100 mL of ion-exchanged water was placed in a glass beaker having an internal volume of 500 mL, and the pH was adjusted to 10 with a 0.2N sodium hydroxide aqueous solution. A mixed solution of aluminum chloride and magnesium chloride [A
l ³⁺ ion concentration 0.075 mol / L, Mg ²⁺ ion 0.15 mol / L] about 22.9 mL [Al ³⁺ ion total amount 1.72 mmol, Mg ²⁺ ion total amount 3.43 mmo
1] was added dropwise over 2 hours. During the dropping, stirring was continued using an anchor blade so that the G value became 100. Further, nitrogen gas was bubbled from the bottom of the beaker at a rate of 1 Nm ³ / m ³ · h. During the dropping, a 0.2N sodium hydroxide aqueous solution was appropriately dropped to adjust the pH to 9.8 or more and 10.2 or less. Immediately after the addition of the mixed aqueous solution of aluminum chloride and magnesium chloride, a white precipitate started to form. The generation of the precipitate was completed 2 hours after the start of the dropwise addition of the mixed aqueous solution. When the stirring was stopped, the generated precipitate slowly settled.

The aqueous solution containing this precipitate was added with 0.2N aqueous sodium hydroxide solution to adjust the pH to 12.0, and the coagulated waste water after the emulsion polymerization of PTFE (SS component 230
(0 ppm, APFO concentration 148 ppm) was added over 30 minutes. During the addition, stirring was continued using an anchor blade so that the G value became 100. After the addition was completed, the stirring was stopped, and the precipitate was collected by filtration with a 3 μm membrane filter. This precipitate was dried together with filter paper at 70 ° C. for 15 hours. The dry weight of the precipitate was 2.30 g. The dried precipitate was subjected to differential thermogravimetric analysis (DTA), infrared absorption spectrum (IR), X
When analyzed by RD, the peaks attributed to PTFE and the weak peaks attributed to the layered double hydroxide, and further PFO
A weak peak attributed to A was detected. From this,
It was confirmed that this precipitate was a precipitate of PTFE and PFOA together with the layered double hydroxide. When the supernatant was analyzed, the concentration of APFO was 120 ppm, so that the fixing rate of PFOA contained in the layered double hydroxide was 1.
It was 8.9%.

[0047]

According to the method for recovering a fluorine-containing emulsifier of the present invention, the fluorine-containing emulsifier can be easily recovered from the waste water after separating the fluoropolymer obtained by polymerizing the fluorine-containing monomer.

Continued front page    (72) Inventor Sora Funaki             Asahi Glass Co., Ltd. 10 Goi Coast, Ichihara City, Chiba Prefecture             In the company (72) Inventor Masataka Eda             Asahi Glass Co., Ltd. 10 Goi Coast, Ichihara City, Chiba Prefecture             In the company (72) Inventor Hiroki Kamiya             Asahi Glass Co., Ltd. 10 Goi Coast, Ichihara City, Chiba Prefecture             In the company (72) Inventor Kota Omori             3-1-6 Ibaraki, Akita City, Akita Prefecture             Within Emco (72) Inventor Takeshi Kamiya             3-1-6 Ibaraki, Akita City, Akita Prefecture             Within Emco

Claims (4)

[Claims] 1. A divalent metal ion is added to an aqueous solution of sodium hydroxide and / or potassium hydroxide while maintaining the pH of the aqueous solution within a range in which the divalent metal ion and the trivalent metal ion form a hydroxide. A fluoropolymer obtained by adding a mixed aqueous solution containing a trivalent metal ion to form a layered double hydroxide, and then polymerizing at least one fluorine-containing monomer in an aqueous medium containing a fluorine-containing emulsifier. The pH of the waste water after the separation of the waste water, wherein the content of the suspended solid content and the substance capable of becoming the suspended solid content is 1% by mass or less, the waste water containing the fluorine-containing emulsifier.
Is adjusted to the same range as when the layered double hydroxide was produced, and the layered double hydroxide-containing aqueous solution was added to the pH-adjusted wastewater to form a layered layer containing the emulsifier-containing layer. A method for recovering a fluorine-containing emulsifier, which comprises forming a double hydroxide, separating the layered double hydroxide from the waste water, and recovering the fluorine-containing emulsifier. 2. The method for recovering a fluorine-containing emulsifier according to claim 1, wherein the divalent metal ion is one or two selected from magnesium ion and zinc ion, and the trivalent metal ion is aluminum ion. 3. The fluoropolymer is polytetrafluoroethylene, tetrafluoroethylene / ethylene copolymer, tetrafluoroethylene / propylene copolymer, tetrafluoroethylene /
Propylene / vinylidene fluoride copolymer, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / CF ₂ ═CFO (CF ₂ ) ₂ CF ₃ copolymer, one selected from polyvinylidene fluoride or The method for recovering a fluorine-containing emulsifier according to any one of claims 1 to 3, which comprises two or more kinds. 4. A fluorine-containing emulsifier having 5 to 13 carbon atoms.
Of perfluoroalkanoic acid, ω-hydroperfluoroalkanoic acid, ω-chloroperfluoroalkanoic acid, salt of perfluoroalkanesulfonic acid, and / or at least one etheric oxygen atom in the molecule. 5. One or more selected from the group of salts of perfluoroalkanoic acid, ω-hydroperfluoroalkanoic acid, ω-chloroperfluoroalkanoic acid and perfluoroalkanesulfonic acid, which are contained, according to claim 1. A method for recovering a fluorine-containing emulsifier.