Title of Invention

A PROCESS FOR THE RECOVERY OF FLUORINATED EMULSIFIER ACIDS FROM WASTEWATER

Abstract The invention relates to a process for the recovery of fluorinated emulsifier acids from wastewater, which comprises stabilizing finely dispersed solids characterized in that the finely dispersed solids are stabilized by means of a non-ionic or cationic surfactant or a surface-active substance, and subsequently binding the fluorinated emulsifier acids to an anion-exchange resin and eluting the fluorinated emulsifier acids from this.
Full Text

In the polymerization of fluorinated monomers in aqueous dispersion, use is made of fluorinated alkanoic acids as emulsifiers since they have no telegenic properties. In particular, use is made of the salts, preferably the alkali metal or ammonium salts, of perfluorinated or partially fluorinated alkane-carboxylic acids or alkanesulfonic acids. These compounds are prepared by electrofluorination or by telomerization of fluorinated monomers, which is costly. There have therefore been many attempts to recover these valuable materials from wastewater.
US-A-5 442 097 discloses a process for the recovery of fluorinated carboxylic acids in usable forTTi from contaminated starting materials. In this process, the fluorinated carboxylic acid is, if necessary, liberated from these materials in an aqueous medium using a sufficiently strong acid, the fluorinated carboxylic acid is reacted with a suitable alcohol and the ester formed is distilled off. The starting material can here be a polymerization liquor, in particular from an emulsion polymerization .in which the fluoropolymer is prepared in the form of colloidal particles with the aid of relatively high amounts of emulsif ier. This process has proven very useful, but requires a certain concentration of fluorinated * carboxylic acid in the starting material.
DE-A-20 44 986 discloses a process for the recovery of perfluorocarboxylic acids' from dilute solution, in which the dilute solution of the perfluorocarboxylic acids is brought into adsorption contact with a weak base ani on--exchange resin and the perf luorocarboxylic acid present in the solution is thereby adsorbed on the

anion-exchange resin, the anion-exchange resin is eluted with an aqueous ammonia solution and the adsorbed perfluorocarboxylic acid is thus transferred into the eluant and the acid is finally isolated from the eluate. However, complete elution requires relatively large amounts of dilute ammonia solution and this process is also very time-consuming. These disadvantages are overcome by the process known from US-A-4 2 82 162 for the elution of fluorinated emulsifier acids adsorbed on basic anion exchangers, in which the elution of the adsorbed fluorinated emulsifier acid from the anion exchanger is carried out using a mixture of dilute mineral acid and an organic solvent. In this process, the ion-exchange resin is regenerated at the same time by use of the acid.
It has been found that this last-named process presents problems in industrial practice when, in particular, the wastewater processed contains very fine solids which in the past were often not recognized or at least not recognized as causing a problem. In this case, the apparatuses containing the anion-exchange resin become clogged with these solids more or less quickly, which becomes noticeable as a result of increased flow resistance and reduced performance. The upstream filters or frits customarily used are ineffective here.
It has also been found that these difficulties are caused by the fine solids being trapped in relatively stable colloidal suspension by the emulsifier acids. When these acids are then removed from the system by means of the anion-exchange resin, this relatively stable dispersion is destroyed and the solid is precipitated and clogs the ion-exchange resin. It was thus also found that the performance of the process known from US-A-4 282 162 can be considerably improved and also made suitable for wastewater containing fine solids if the dispersion of the solids in the wastewater is stabilized by addition of a nonionic or

cationic surface-active additive (surfactant) before the wastewater is brought into contact with the anion exchanger. The nonionic or cationic surfactants are not bound by the anion exchanger.
The invention accordingly ■provides a process for the recovery of fluorinated emulsifier acids from wastewater, which comprises stabilizing the solids which are finely dispersed in the wastewater by means of a nonionic or cationic surfactant or a surface-active substance having an analogous effect and subsequently binding the fluorinated emulsifier acids to an anion-exchange resin and eluting the fluorinated emulsifier acids from this.
Wastewater suitable for treatment is waste w&tex* of proC€^^ in which surface-active fluorinated alkanoic acids are present. The process is particularly suitable for wastewater from the polymerization of fluorinated monomers by the emulsion method, in which the fluorinated monomer is converted in the presence of a relatively high concentration of fluorinated emulsifier acid and with mild stirring into a finely divided polymer which is in finely dispersed, colloidal form and in which the latex obtained is coagulated, for example by intensive stirring, after the desired solids concentration has been reached, so that the polymer precipitates as a fine powder.
It has been found that in the known work-up it is especially relatively low molecular weight polymer material which causes difficulties; the adverse effect of these low molecular weight polymers becomes particularly noticeable when the polymerization process leads to a broad molecular weight distribution. In the case of such "difficult" wastewater too, the process of the invention displays its capabilities.

The removal of solids before the wastewater is brought into contact with the ion-exchange resin is also known (German patent application 198 24 614.5 of June 2, 1998 with the title "Verfahren zur Riickgewinnung von fluorierten Alkansauren aus Abwassern"). However, this has the disadvantage of a high outlay in terms of apparatus for the solids removal and the amount of auxiliary chemicals to be added {for example milk of lime, aluminum salts, flocculants). Particularly at low solids concentrations, complete removal of the colloidal material requires relatively large amounts of chemicals which are removed again to only a limited extent in the solids removal.
In the process of the invention, the outlay in terms of apparatuses and chemicals is considerably reduced since the addition of small amounts of a preferably readily biodegradable surfactant is sufficient for stabilizing the colloids and ensures trouble-free operation of the ion exchanger.
The adsorption of the emulsifier acids onto ion-exchange resins can be carried out in a manner known per se. Suitable resins are, in particular, strong base anion-exchange resins as are obtainable, for example, under the trade names ®AMBERLITE IRA-402, ®AMBERJET 4200 (both Rohm & Haas), ®PUROLITE A845 (Purolite GmbH) or ®LEWATIT MP-500 (Bayer AG).
The adsorption can be carried out in a manner knqwn per se, with the ion-exchange resins being located in customary apparatuses such as tubes or columns through which the wastewater flows.
The elution of the bound emulsifier acids is likewise carried out in a manner known per se, with preference being given to the method described in US-A-4 282 162,

Methods suitable for isolating the emulsifier acids in the high purity required for use in polymerization are^ for example, those described in the abovementioned US-A-5 442 097 or that described in US-A-5 312 935 in which the eluate is firstly substantially freed of water and then treated with oxidizing agents.
The wastewater remaining after adsorption of the emulsifier acids is treated in a known manner, depending on the content of other materials.
The invention is illustrated by the following examples.
Examples 1 to 4 and comparative example
The starting material used is wastewater from the copolymerization of ' tetrafluoroethylene and perfluoro(n-propyl vinyl ether) in which the ammonium salt of n- and' iso-perfluorooctanoic acid (PFOA) is used as emulsifier. The PFOA concentration is 750 mg/1.
In a stirred vessel, 1000 g of this liquor are admixed with 0.1 g of the nonionic surfactant ®TRITON X-100 (Rohm Sc Haas, p-octylphenol ethoxylate, CAS No. 9002-93-1) or ®GENAPOL UD 088 (Hoechst AG, fatty alcohol polyglycol ether) and stirred.
About 50 ml of a commercial strong base ion-exchange resin (®AMBERLITE IRA-402, Rohm & Haas; styrene-divinylbenzene type, anion: chloride, gel, total capacity: 1.3 eq/1, bulk density: 710 g/l) are placed in a cylindrical glass column (length: 25 cm, diameter: 16 mm) provided with a glass frit and rinsed with water. To load the ion exchanger, the solution is pumped upward through the bed by means of a pump. The water leaving the column is collected as a plurality of samples and the PFOA concentration is determined. The pressure drop over the ion exchanger bed is measured by means of a manometer. The water leaving the column is

collected as a plurality of samples and the PFOA concentration is determined.
The loading experiment without addition of surfactant (comparative example) had to be stopped since the pressure drop increased to above 1 bar/m as a result of precipitated polymer and the resin displayed significant conglutination.

Example 5
150 ml of an elution solution are mixed from methanol, concentrated sulfuric acid (96%) and water (proportions by mass: 89%, 7%, 4%), The ion exchanger column is, after loading, firstly rinsed with 100 ml of water in order to remove remaining wastewater from the column. The ^elution solution is then passed through the column at a linear velocity of 0.5 m/h and is collected. The column is finally rinsed with a further 50 ml of water. The elution solution contains about 95% of the emulsifier solution in the wastewater used.





WE CLAIM:
1. A process for the recovery of fluorinated emulsifier acids from wastewater, which comprises stabilizing finely dispersed sohds characterized in that the finely dispersed solids are stabilized by means of a non-ionic or cationic surfactant or a surface-active substance, and subsequently binding the fluorinated emulsifier acids to an anion-exchange resin and eluting the fluorinated emulsifier acids from this.
2. The process as claimed in claim 1, wherein the wastewater from the polymerization of fluorinated monomers is used.
3. The process as claimed in claim 1 or 2, wherein the material capable of being converted into solids is precipitated.
4. The process as claimed in any one the preceding claims, wherein the anion-exchange resin used is a strong base anion-exchange resin.
5. The process as claimed in any one of the preceding claims, wherein elution is carried out using a mixture of dilute mineral acid and an organic solvent.


Documents:

in-pct-2000-897-che-abstract.pdf

in-pct-2000-897-che-claims.pdf

in-pct-2000-897-che-correspondence others.pdf

in-pct-2000-897-che-correspondence po.pdf

in-pct-2000-897-che-description complete.pdf

in-pct-2000-897-che-form 1.pdf

in-pct-2000-897-che-form 19.pdf

in-pct-2000-897-che-form 26.pdf

in-pct-2000-897-che-form 3.pdf

in-pct-2000-897-che-form 5.pdf

in-pct-2000-897-che-pct.pdf


Patent Number 211150
Indian Patent Application Number IN/PCT/2000/897/CHE
PG Journal Number 26/2007
Publication Date 29-Jun-2007
Grant Date 17-Oct-2007
Date of Filing 29-Dec-2000
Name of Patentee M/S. DYNEON GMBH & CO. KG
Applicant Address D-84504 Burgkirchen
Inventors:
# Inventor's Name Inventor's Address
1 FELIX, Bernd Rehdorf 1 D-84508 Burgkirchen
2 ZIPPLIES, Tilman Robert-Koch-Strasse 142 D-84489 Burghausen
3 FÜHRER, Stephan Ludwigshafener Strasse 1 D-84508 Burgkirchen
4 KAISER, Thomas Frankfurter Strasse 193a D-65779 Kelkheim
5 BUDESHEIM, Armin Sonnenhöhe 20 D-65207 Wiesbaden- Naurod
PCT International Classification Number C02F 1/58
PCT International Application Number PCT/EP99/03673
PCT International Filing date 1999-05-27
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 19824615.3 1998-06-02 Germany