U.S. patent application number 11/420377 was filed with the patent office on 2007-01-18 for process for recovery of fluorinated carboxylic acid surfactants from exhaust gas.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Richard M. Flynn, Klaus Hintzer, Michael Jurgens, Harald Kaspar, Herbert Koenigsmann, Kai Helmut Lochhaas, Andreas R. Maurer, George G. I. Moore, Jay F. Schulz, Werner Schwertfeger, Tilman Zipplies.
Application Number | 20070015937 11/420377 |
Document ID | / |
Family ID | 37662436 |
Filed Date | 2007-01-18 |
United States Patent
Application |
20070015937 |
Kind Code |
A1 |
Hintzer; Klaus ; et
al. |
January 18, 2007 |
PROCESS FOR RECOVERY OF FLUORINATED CARBOXYLIC ACID SURFACTANTS
FROM EXHAUST GAS
Abstract
A process for recovering a fluorinated carboxylic acid or salts
thereof from exhaust gas streams. The process includes contacting
the exhaust gas stream with a composition capable of at least
partially removing the fluorinated carboxylic acid or salt thereof
from the exhaust gas stream. The fluorinated carboxylic acid or
salt thereof is selected from the group consisting of fluorinated
carboxylic acids or salts thereof that correspond to the general
formula: [R.sub.f--O-L-COO.sup.-].sub.iX.sup.i+ (I) wherein L
represents a linear partially or fully fluorinated alkylene group
or an aliphatic hydrocarbon group, R.sub.f represents a linear
partially or fully fluorinated aliphatic group or a linear
partially or fully fluorinated aliphatic group interrupted with one
or more oxygen atoms, X.sup.i+ represents a cation having the
valence i and i is 1, 2 or 3.
Inventors: |
Hintzer; Klaus; (Kastl,
DE) ; Jurgens; Michael; (Neuoetting, DE) ;
Kaspar; Harald; (Burgkirchen, DE) ; Koenigsmann;
Herbert; (Burgkirchen, DE) ; Lochhaas; Kai
Helmut; (Neuoetting, DE) ; Maurer; Andreas R.;
(Langenneuanach, DE) ; Schwertfeger; Werner;
(Altoetting, DE) ; Zipplies; Tilman; (Burghausen,
DE) ; Moore; George G. I.; (Afton, MN) ;
Schulz; Jay F.; (Inver Grove Heights, MN) ; Flynn;
Richard M.; (Mahtomedi, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
37662436 |
Appl. No.: |
11/420377 |
Filed: |
May 25, 2006 |
Current U.S.
Class: |
562/586 ;
423/240S; 562/605 |
Current CPC
Class: |
Y02C 20/30 20130101;
C08L 2666/22 20130101; C08L 27/12 20130101; C08L 71/02 20130101;
C08L 27/12 20130101 |
Class at
Publication: |
562/586 ;
423/240.00S; 562/605 |
International
Class: |
B01D 53/70 20060101
B01D053/70; C07C 59/115 20070101 C07C059/115; C07C 53/18 20070101
C07C053/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 2005 |
GB |
0525978.3 |
Nov 24, 2005 |
GB |
0523853.0 |
Jul 15, 2005 |
GB |
0514398.7 |
Jul 15, 2005 |
GB |
0514387.0 |
Claims
1. A process for the recovery of a fluorinated carboxylic acid or
salts thereof from exhaust gas streams, the process comprising
contacting the exhaust gas stream with a composition capable of at
least partially removing the fluorinated carboxylic acid or salt
thereof from said exhaust gas stream, wherein said fluorinated
carboxylic acid or salt thereof is selected from the group
consisting of fluorinated carboxylic acids or salts thereof that
correspond to the general formula:
[R.sub.f--O-L-COO.sup.-].sub.iX.sup.i+ wherein L represents a
linear partially or fully fluorinated alkylene group or an
aliphatic hydrocarbon group, R.sub.f represents a linear partially
or fully fluorinated aliphatic group or a linear partially or fully
fluorinated aliphatic group interrupted with one or more oxygen
atoms, X.sup.i+ represents a cation having the valence i and i is
1, 2 or 3.
2. A process according to claim 1 wherein the anion of said
fluorinated carboxylic acids or salts thereof has a molecular
weight of not more than 1000 g/ mol.
3. A process according to claim 1 wherein the anion of said
fluorinated carboxylic acids or salts thereof has a molecular
weight of not more than 500 g/ mol.
4. A process according to claim 1 wherein the fluorinated
carboxylic acid or salt thereof when administered to rat shows a
renal recovery rate of at least 50% of the administered amount, 96
hours after administration and wherein the renal half-life
(T.sub.1/2) is not more than 30 hours.
5. A process according to claim 1 wherein the fluorinated
carboxylic acid or salts are selected from fluorinated carboxylic
acid or salts of which any fluorinated aliphatic portion has not
more than 3 carbon atoms.
6. A process according to claim 1 wherein L in said formula is
selected from the group consisting of linear perfluorinated
alkylene groups having 1 to 6 carbon atoms, linear partially
fluorinated alkylene groups having 1 to 6 carbon atoms having not
more than 2 hydrogen atoms, aliphatic hydrocarbon groups having 1
to 6 carbon atoms.
7. A process according to claim 1 wherein R.sub.f is selected from
the group consisting of linear perfluorinated aliphatic groups
having 1 to 6 carbon atoms; linear perfluorinated aliphatic groups
interrupted with one or more oxygen atoms of which alkylene groups
between oxygen atoms have not more than 6 carbon atoms and wherein
the terminal alkyl group has not more than 6 carbon atoms; linear
partially fluorinated aliphatic groups having 1 to 6 carbon atoms
and not more than 2 hydrogen atoms and linear partially fluorinated
aliphatic groups interrupted with one or more oxygen atoms and
which have not more than 2 hydrogen atoms.
8. A process according to claim 1 wherein L is selected from the
group consisting of --(CF.sub.2).sub.g-- wherein g is 1, 2, 3, 4, 5
or 6; --CFH--(CF.sub.2).sub.h-- wherein h is 0, 1, 2, 3, 4 or 5;
--CF.sub.2--CFH--(CF.sub.2).sub.d-- wherein d is 0, 1, 2, 3 or 4;
--CH.sub.2--(CF.sub.2).sub.h-- wherein h is 1, 2, 3 or 4; and
--(CH.sub.2).sub.c-- wherein c is 1, 2, 3 or 4.
9. A process according to claim 1 wherein R.sub.f corresponds to
the following formula:
R.sub.f.sup.1--[OR.sub.f.sup.2].sub.p--[OR.sub.f.sup.3].sub.q--
(II) wherein R.sub.f.sup.1 is a perfluorinated linear aliphatic
group of 1 to 6 carbon atoms, R.sub.f.sup.2 and R.sub.f.sup.3 each
independently represents a linear perfluorinated alkylene of 1, 2,
3 or 4 carbon atoms and p and q each independently represent a
value of 0 to 4 and wherein the sum of p and q is at least 1.
10. A process according to claim 1 wherein R.sub.f corresponds to
the following formula: R.sup.7.sub.f--(O).sub.t--CFH--CF.sub.2--
(III) wherein t is 0 or 1 and R.sup.7.sub.f represents a linear
partially or fully fluorinated aliphatic group optionally
interrupted with one or more oxygen atoms.
11. A process according to claim 1 wherein R.sub.f corresponds to
the formula: R.sub.f.sup.8--(OCF.sub.2).sub.a-- (IV) wherein a is
an integer of 1 to 6 and R.sub.f.sup.8 is a linear partially
fluorinated aliphatic group or a linear fully fluorinated aliphatic
group having 1, 2, 3 or 4 carbon atoms.
12. A process according to claim 1 wherein R.sub.f corresponds to
the formula: R.sub.f.sup.9--O--(CF.sub.2).sub.b-- (V) wherein b is
an integer of 1 to 6, preferably 1, 2, 3 or 4 and R.sub.f.sup.9 is
a linear partially fluorinated aliphatic group or a linear fully
fluorinated aliphatic group having 1, 2, 3 or 4 carbon atoms.
13. A process according to claim 1 wherein the fluorinated
carboxylic acid corresponds to the following formula:
[R.sub.f.sup.a--(O).sub.t--CHF--(CF.sub.2).sub.n--COO--].sub.iX.sup.i+
(VI) wherein R.sub.f.sup.a represents a linear partially or fully
fluorinated aliphatic group optionally interrupted with one or more
oxygen atoms, t is 0 or 1 and n is 0 or 1, X.sup.i+ represents a
cation having a valence i and i is 1, 2 or 3, with the proviso that
when t is 0, the R.sub.f.sup.a contains at least one ether oxygen
atom.
14. A process according to claim 1 wherein the fluorinated
carboxylic acid corresponds to the following formula:
R.sub.f.sup.b--(O).sub.t--CFH--CF.sub.2--O--R--G (VII) wherein
R.sub.f.sup.b represents a linear partially or fully fluorinated
aliphatic group optionally interrupted with one or more oxygen
atoms, R is an aliphatic hydrocarbon group, G represents a
carboxylic acid or salt thereof, t is 0 or 1.
15. A process according to claim 1 wherein the fluorinated
carboxylic acid corresponds to one of the following formulas:
R.sub.f.sup.c--(OCF.sub.2).sub.u--O--(CF.sub.2).sub.v-AC (VIII)
wherein u is an integer of 1 to 6, v is an integer of 1 to 6,
R.sub.f.sup.c represents a linear perfluorinated aliphatic group of
1, 2, 3 or 4 carbon atoms and AC represents a carboxylic acid group
or salt thereof; and
R.sub.f.sup.c--O--(CF.sub.2).sub.y--O-L.sup.1-AC (IX) wherein y has
a value of 1, 2, 3, 4, 5 or 6, L.sup.1 represents a linear
perfluorinated alkylene of 1, 2, 3, 4, 5 or 6 carbon atoms or a
linear partially fluorinated alkylene having 1 to 6 carbon atoms
and 1 or 2 hydrogen atoms, R.sub.f.sup.c is as defined in above
formula (VIII) and AC represents a carboxylic acid group or salt
thereof.
16. A process according to claim 1 wherein the fluorinated
carboxylic acid or salt thereof is selected from the group
consisting of C.sub.3F.sub.7--O--CHF--COOH
CF.sub.3--O--CF.sub.2CF.sub.2--CF.sub.2--O--CHF--COOH
CF.sub.3CF.sub.2CF.sub.2--O--CF.sub.2CF.sub.2--CF.sub.2--O--CHF--COOH
CF.sub.3--O--CF.sub.2--CF.sub.2--O--CHF--COOH
CF.sub.3--O--CF.sub.2--O--CF.sub.2--CF.sub.2--O--CHF--COOH
CF.sub.3--(O--CF.sub.2).sub.2--O--CF.sub.2--CF.sub.2--O--CHF--COOH
CF.sub.3--(O--CF.sub.2).sub.3--O--CF.sub.2--CF.sub.2--O--CHF--COOH
CF.sub.3--O--CHF--CF.sub.2--COOH
CF.sub.3--O--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--COOH
CF.sub.3--CF.sub.2--O--CHF--CF.sub.2--COOH
CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--COOH
CF.sub.3--O--CF.sub.2--O--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--COOH
CF.sub.3--(O--CF.sub.2).sub.2--O--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--C-
OOH
CF.sub.3--(O--CF.sub.2).sub.3--O--CF.sub.2--CF.sub.2--O--CHF--CF.sub.-
2--COOH CF.sub.3--O--CF.sub.2--CHF--COOH
C.sub.3F.sub.7--O--CF.sub.2--CHF--COOH
CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--COOH
CF.sub.3--O--CF.sub.2--O--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--COOH
CF.sub.3--(O--CF.sub.2).sub.2--O--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--C-
OOH
CF.sub.3--(O--CF.sub.2).sub.3--O--CF.sub.2--CF.sub.2--O--CF.sub.2--CH-
F--COOH CF.sub.3--O--CF.sub.2--CHF--CF.sub.2--COOH
C.sub.2F.sub.5--O--CF.sub.2--CHF--CF.sub.2--COOH
C.sub.3F.sub.7--O--CF.sub.2--CHF--CF.sub.2--COOH
CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--CF.sub.2--CO-
OH
CF.sub.3--O--CF.sub.2--O--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--CF.sub-
.2--COOH
CF.sub.3--(O--CF.sub.2).sub.2--O--CF.sub.2--CF.sub.2--O--CF.sub.-
2--CHF--CF.sub.2--COOH
CF.sub.3--(O--CF.sub.2).sub.3--O--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--C-
F.sub.2--COOH CF.sub.3--O--CHF--CF.sub.2--O--CH.sub.2--COOH
CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--O--CH.sub.2--
-COOH C.sub.3F.sub.7--O--CHF--CF.sub.2--O--CH.sub.2--COOH
C.sub.3F.sub.7--O--CHF--CF.sub.2--O--CH.sub.2--CH.sub.2--COOH
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--OCH.sub.2COOH
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--OCH.su-
b.2COOH C.sub.3F.sub.7--O--CF.sub.2--CHF--CF.sub.2--OCH.sub.2COOH
CF.sub.3--CHF--CF.sub.2--O--CH.sub.2COOH
C.sub.3F.sub.7--CF.sub.2--CHF--CF.sub.2--OCH.sub.2--COOH
CF.sub.3--O--CF.sub.2--CF.sub.2--O--CH.sub.2--COOH
CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CF.sub.2--CF.sub.2--O--CH.s-
ub.2--COOH C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--O--CH.sub.2--COOH
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--O--CH.sub.2--CH.sub.2--COOH
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--O--CF.sub.2--CF.sub.2--OCH.sub.2CO-
OH
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CF.sub.2--CF.sub.2-
--OCH.sub.2COOH
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--CF.sub.2--OCH.sub.2COOH
C.sub.4F.sub.9--O--CH.sub.2--COOH
C.sub.4F.sub.9--O--CH.sub.2--CH.sub.2--COOH
C.sub.3F.sub.7--O--CH.sub.2COOH C.sub.6F.sub.13--OCH.sub.2--COOH
CF.sub.3--O--CF.sub.2--CF.sub.2--COOH
C.sub.2F.sub.5--O--CF.sub.2--CF.sub.2--COOH
C.sub.3F.sub.7--O--CF.sub.2 --CF.sub.2--COOH
C.sub.4F.sub.9--O--CF.sub.2--CF.sub.2--COOH
CF.sub.3--(O--CF.sub.2).sub.3--O--CF.sub.2--COOH
CF.sub.3--(O--CF.sub.2).sub.2--O--CF.sub.2--COOH
CF.sub.3--(O--CF.sub.2).sub.1--O--CF.sub.2--COOH
CF.sub.3--(O--CF.sub.2--CF.sub.2).sub.1--O--CF.sub.2--COOH
C.sub.2F.sub.5--(O--CF.sub.2--CF.sub.2).sub.1--O--CF.sub.2--COOH
C.sub.2F.sub.5--(O--CF.sub.2--CF.sub.2).sub.2--O--CF.sub.2--COOH
CF.sub.3--(O--CF.sub.2--CF.sub.2).sub.2--O--CF.sub.2--COOH
C.sub.3F.sub.7--O--CF.sub.2--COOH
CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CF.sub.2--COOH
CF.sub.3CFH--O--(CF.sub.2).sub.3--COOH
CF.sub.3CFH--O--(CF.sub.2).sub.5--COOH
CF.sub.3--CF.sub.2--O--(CF.sub.2).sub.3COOH
CF.sub.3--CF.sub.2--O--(CF.sub.2).sub.5COOH and salts of any of
these fluorinated carboxylic acids.
17. A process according to claim 1 wherein said composition
comprises an adsorbent particle capable of adsorbing said
fluorinated carboxylic acid or salt thereof.
18. A process according to claim 5 wherein said adsorbent is
selected from the group consisting of an anion exchange resins and
active carbon.
19. A process according to claim 1 wherein said composition
comprises a scrubber liquid.
20. A process according to claim 7 wherein said scrubber liquid is
selected from demineralized water and aqueous alkaline
solutions.
21. A process according to claim 7 wherein said scrubber liquid is
subsequently contacted with an adsorbent particle capable of
adsorbing said fluorinated carboxylic acid or salt thereof.
22. A process according to claim 1 wherein said composition
comprises an aqueous alkaline solution causing said fluorinated
carboxylic acid or salt thereof to separate out as a separate
phase.
23. A process according to claim 1 wherein said composition
comprises an aqueous potassium carbonate solution.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims priority to Great Britain
Application No. 0525978.3, filed on Dec. 21, 2005; Great Britain
Application No. 0523853.0, filed on Nov. 24, 2005; Great Britain
Application No. 0514398.7, filed on Jul. 15, 2005; and Great
Britain Application No. 0514387.0 filed on Jul. 15, 2005, all of
which are herein incorporated by reference in their entirety.
[0002] The present invention relates to a process for recovering
fluorinated carboxylic acids or salts thereof from an exhaust gas
stream.
[0003] Polymerization of fluoroolefins to manufacture
fluoropolymers is often performed in aqueous media. In one such
process referred to as emulsion polymerization, fluorinated
carboxylic acids are typically used as surfactants in the aqueous
media at concentrations on the order of 0.1% by weight of water in
the recipe. Examples of these fluorosurfactants include the
perfluorinated alkane carboxylic acids having 7 to 10 carbon atoms,
in particular perfluorooctanoic acid (PFOA). These acids are
generally used in the salt form, preferably as ammonium salts.
Fluoropolymerizations to make "granular fluoropolymer" are also
done in aqueous media in a process sometimes referred to as
suspension polymerization, though with less fluorosurfactant (or
none) than is used in dispersion polymerization. For a discussion
of the processes, see "Tetrafluoroethylene Polymers" in the
Encyclopedia of Polymer Science and Engineering, John Wiley &
Sons, New York, 1989, Vol. 16, p. 580.
[0004] When, after polymerization, the fluoropolymer is isolated
from the aqueous medium, i.e., by coagulation in emulsion
polymerization, a substantial portion of the perfluorooctanoic acid
typically remains on the fluoropolymer. When the fluoropolymer is
heated for the purpose of drying, the PFOA is volatilized and
carried away in the dryer or oven exhaust gas. To avoid release of
the PFOA into the environment, it is known to contact the exhaust
gas with for example a scrubber solution or liquid to recover the
PFOA from the exhaust gas stream, also called off-gas stream.
[0005] Methods of treating an off-gas stream with a scrubber
solution are disclosed in for example U.S. Pat. No. 5,990,330, U.S.
Pat. No. 6,245,923 and U.S. Pat. No. 6,720,437. Depending on the
scrubber solution used, the PFOA may separate as a separate phase,
thus allowing easy recovery or re-use.
[0006] Although the recovery of the perfluorinated alkanoic acids
and salts thereof, which are typically used in emulsion
polymerization, from exhaust gas streams according to the above
method represents an economical and environmental advantage through
the re-use of these compounds as surfactants in the emulsion
polymerization of fluorinated monomers, the process still suffers
from the disadvantage that some amount of perfluorinated carboxylic
acid or salt thereof may nevertheless be lost and/or released in
the environment. This is particularly disadvantageous because
perfluorinated alkanoic acids having 8 or more carbons are known to
be bio-accumulating.
[0007] It would thus be desirable to find alternative fluorinated
carboxylic acids that can be used in the emulsion polymerization of
fluorinated monomers and that can be recovered from off-gas streams
using a convenient and cost effective method. Desirably, the
alternative fluorinated carboxylic acids show lower
bio-accumulation profile than perfluoro alkanoic acids having 8 or
more carbon atoms, such that any losses of the fluorinated
carboxylic acid provide a lower environmental health and safety
concern.
[0008] In one aspect, the present invention provides a process for
the recovery of a fluorinated carboxylic acid or salts thereof from
exhaust gas streams, the process comprising contacting the exhaust
gas stream with a composition capable of at least partially
removing the fluorinated carboxylic acid or salt thereof from said
exhaust gas stream, wherein said fluorinated carboxylic acid or
salt thereof is selected from the group consisting of fluorinated
carboxylic acids or salts thereof that correspond to the general
formula: [R.sub.f--O-L-COO.sup.-].sub.iX.sup.i+ (I) wherein L
represents a linear partially or fully fluorinated alkylene group
or an aliphatic hydrocarbon group, R.sub.f represents a linear
partially or fully fluorinated aliphatic group or a linear
partially or fully fluorinated aliphatic group interrupted with one
or more oxygen atoms, X.sup.i+ represents a cation having the
valence i and i is 1, 2 or 3. Examples of cations include H.sup.+,
ammonium, monovalent metal cations, divalent metal cations and
trivalent cations. Typical cations are H.sup.+ and
NH.sub.4.sup.+.
[0009] It has been found that fluorinated carboxylic acids and
salts according to the above general formula (I) eliminate more
quickly from a living organism, as demonstrated on rat screening
studies, than perfluoro alkanoic acids having 8 or more carbon
atoms. Additionally, it has been found that these surfactants can
be used in the emulsion polymerization of fluorinated monomers to
produce fluoropolymers and can be recovered from off-gas streams in
an easy and convenient way by contacting the exhaust gas with a
composition capable of at least partially removing the fluorinated
carboxylic acid or salt thereof from said exhaust gas stream. In
particular, the volatile fluorinated carboxylic acids and salts as
well as other fluorinated carboxylic acids and salts which may be
carried as aerosols with the exhaust gas stream, can be readily
recovered from such exhaust gas stream. Because of their lower
bio-accumulation, the fluorinated carboxylic acids, salts and
derivatives (such as ester derivatives) should provide less of an
environmental impact in case of small losses of these compounds.
Also, the process should be more beneficial for operators of the
process that may be exposed, for example accidentally, to the
fluorinated carboxylic acids, their salts or derivatives used in
work-up procedures following the recovery from the exhaust gas
stream.
Fluorinated Carboxylic Acid
[0010] For the sake of convenience, the term `fluorinated
carboxylic acid` is hereinafter used to indicate the free acid as
well as salts thereof. The fluorinated carboxylic acid used in the
process of the invention corresponds to formula (I) above.
Generally, the fluorinated carboxylic acid will be a low molecular
weight compound, for example a compound having a molecular weight
for the anion part of the compound of not more than 1000 g/mol,
typically not more than 600 g/mol and in particular embodiments,
the anion of the fluorinated carboxylic acid may have a molecular
weight of not more than 500 g/mol.
[0011] Particularly preferred fluorinated carboxylic acids are
those that when administered to rats show a recovery of at least
45%, for example at least 50% of the administered amount after 96
hours via renal elimination and that have a renal elimination
half-life of not more than 35 hours, for example of not more than
30 hours in rats as tested according to the method set forth in the
examples. Generally, fluorinated carboxylic acids in which each of
the fluorinated aliphatic moieties in the compound have not more
than 3 carbon atoms fulfill the aforementioned conditions of renal
recovery and half-life. Thus, preferred compounds are those in
which any fluorinated alkylene groups have not more than 3 carbon
atoms and in which a fluorinated alkyl group of the compound has
not more than 3 carbon atoms.
[0012] In the above formula (I), L represents a linking group. In
one embodiment, the linking group can be a linear partially or
fully fluorinated alkylene. Fully fluorinated alkylene groups
include alkylene groups that consist of only carbon and fluorine
atoms whereas partially fluorinated alkylene groups may
additionally contain hydrogen. Generally, a partially fluorinated
alkylene group should not contain more than 2 hydrogen atoms so as
to be highly fluorinated and be non-telogenic or at least have
minimal telogenic effects. Examples of fully fluorinated alkylene
groups include linear perfluorinated alkylenes that have from 1 to
6 carbon atoms, for example linear perfluorinated alkylene groups
of 1, 2, 3, 4 or 5 carbon atoms.
[0013] Examples of linear partially fluorinated alkylene groups
include those that have from 1 to 6 carbon atoms. In a particular
embodiment the linear partially fluorinated alkylene linking group
has 1, 2, 3, 4, 5 or 6 carbon atoms and has only 1 or 2 hydrogen
atoms. When the partially fluorinated alkylene group has 2 hydrogen
atoms, they may be attached to the same carbon atom or they can be
attached to different carbon atoms. When they are attached to
different carbon atoms, such carbon atoms can be adjacent to each
other or not. Also, in a particular embodiment, a carbon atom
having 1 or 2 hydrogen atoms may be adjacent the ether oxygen atom
to which the linking group is attached or adjacent the carboxylic
group to which the linking group is attached at its other end.
[0014] In a further embodiment, the linking group L is an aliphatic
hydrocarbon group. Examples of aliphatic hydrocarbon groups include
linear, branched or cyclic aliphatic groups. Particular examples of
aliphatic groups include linear or branched alkylene groups of 1 to
4 carbon atoms such as for example methylene or ethylene.
[0015] Particular examples of linking groups L may be selected from
the following: [0016] --(CF.sub.2).sub.g-- wherein g is 1, 2, 3, 4,
5 or 6; [0017] --CFH--(CF.sub.2).sub.h-- wherein h is 0, 1, 2, 3, 4
or 5; [0018] --CF.sub.2--CFH--(CF.sub.2).sub.d-- wherein d is 0, 1,
2, 3 or 4; [0019] --CH.sub.2--(CF.sub.2).sub.h-- wherein h is 1, 2,
3 or 4; [0020] --(CH.sub.2).sub.c-- wherein c is 1, 2, 3 or 4; In
the above examples, the left side of the formula of the linking
group is the site where the linking group is connected to the ether
oxygen in formula (I).
[0021] The R.sub.f group in formula (I) represents a linear
partially or fully fluorinated aliphatic group or a linear
partially or fully fluorinated aliphatic group interrupted with one
or more oxygen atoms. In one embodiment, R.sub.f is a linear
perfluorinated aliphatic group having 1 to 6 carbon atoms,
preferably having 1, 2, 3 or 4 carbon atoms. According to another
embodiment R.sub.f is a linear perfluorinated aliphatic group
interrupted with one or more oxygen atoms of which the alkylene
groups between oxygen atoms have not more than 4 or 6 carbon atoms,
for example 3 or less carbon atoms and wherein the terminal alkyl
group has not more than 4 or 6 carbon atoms, for example 3 or less
carbon atoms. According to a still further embodiment, R.sub.f is a
linear partially fluorinated aliphatic group having 1 to 6 carbon
atoms and not more than 2 hydrogen atoms or a linear partially
fluorinated aliphatic group interrupted with one or more oxygen
atoms and which has not more than 2 hydrogen atoms. In the latter
embodiment, it will generally be preferred that any perfluorinated
alkylene moiety has not more than 4 or 6 carbon atoms and any
terminal perfluorinated alkyl group, likewise preferably should not
have more than 6 carbon atoms, for example not more than 4 carbon
atoms. A particular example of a partially fluorinated aliphatic
group R.sub.f is CF.sub.3CFH--.
[0022] In a particular embodiment, R.sub.f may correspond to the
following formula:
R.sub.f.sup.1--[OR.sub.f.sup.2].sub.p--[OR.sub.f.sup.3].sub.q--
(II) wherein R.sub.f.sup.1 is a perfluorinated linear aliphatic
group of 1 to 6 carbon atoms (for example 3 or less), R.sub.f.sup.2
and R.sub.f.sup.3 each independently represents a linear
perfluorinated alkylene of 1, 2, 3 or 4 carbon atoms and p and q
each independently represent a value of 0 to 4 and wherein the sum
of p and q is at least 1.
[0023] In another embodiment, R.sub.f may correspond to the
following formula: R.sup.7.sub.f--(O).sub.t--CFH--CF.sub.2-- (III)
wherein t is 0 or 1 and R.sup.7.sub.f represents a linear partially
or fully fluorinated aliphatic group optionally interrupted with
one or more oxygen atoms. Typically R.sup.7.sub.f does not contain
perfluorinated aliphatic moieties of more than 4 or 6 carbon atoms.
For example, in one embodiment, R.sup.7.sub.f is a perfluorinated
linear aliphatic group of 1 to 6 carbon atoms. In another
embodiment, R.sup.7.sub.f is a group corresponding to above formula
(II).
[0024] In yet a further embodiment, R.sub.f may correspond to the
following formula: R.sub.f.sup.8--(OCF.sub.2).sub.a-- (IV) wherein
a is an integer of 1 to 6 and R.sub.f.sup.8 is a linear partially
fluorinated aliphatic group or a linear fully fluorinated aliphatic
group having 1, 2, 3 or 4 carbon atoms. When R.sub.f.sup.8 is a
partially fluorinated aliphatic group, the number of carbon atoms
preferably is between 1 and 6 and the number of hydrogen atoms in
the partially fluorinated aliphatic groups is preferably 1 or
2.
[0025] In a still further embodiment, R.sub.f may correspond to the
following formula: R.sub.f.sup.9--O--(CF.sub.2).sub.b-- (V) wherein
b is an integer of 1 to 6, preferably 1, 2, 3 or 4 and
R.sub.f.sup.9 is a linear partially fluorinated aliphatic group or
a linear fully fluorinated aliphatic group having 1, 2, 3 or 4
carbon atoms. When R.sub.f.sup.9 is a partially fluorinated
aliphatic group, the number of carbon atoms preferably is between 1
and 6 and the number of hydrogen atoms in the partially fluorinated
groups is preferably 1 or 2.
[0026] In a particular embodiment of the present invention, the
fluorinated carboxylic acid corresponds to the following formula:
[R.sub.f.sup.a--(O).sub.t--CHF--(CF.sub.2).sub.n--COO.sup.-].sub.iX.sup.i-
+ (VI) wherein R.sub.f.sup.a represents a linear partially or fully
fluorinated aliphatic group optionally interrupted with one or more
oxygen atoms, t is 0 or 1 and n is 0 or 1, X.sup.i+ represents a
cation having a valence i and i is 1, 2 or 3, with the proviso that
when t is 0, the R.sub.f.sup.a contains at least one ether oxygen
atom.
[0027] In a particular aspect of this embodiment, the R.sub.f.sup.a
is selected from the group consisting of linear perfluorinated
aliphatic groups of 1 to 6 carbon atoms, preferably having 1 to 4
carbon atoms, perfluorinated groups of the formula
R.sub.f.sup.1--[OR.sub.f.sup.2].sub.p--[OR.sub.f.sup.3].sub.q--
wherein R.sub.f.sup.1 is a linear perfluorinated aliphatic group of
1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, R.sub.f.sup.2
and R.sub.f.sup.3 each independently represents a linear
perfluorinated alkylene of 1, 2, 3 or 4 carbon atoms and p and q
each independently represent a value of 0 to 4 and wherein the sum
of p and q is at least 1 and perfluorinated groups of the formula
R.sub.f.sup.4--[OR.sub.f.sup.5].sub.k--[OR.sub.f.sup.6].sub.m--O--CF.sub.-
2-- wherein R.sub.f.sup.4 is a linear perfluorinated aliphatic
group of 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms,
R.sub.f.sup.5 and R.sub.f.sup.6 each independently represents a
linear perfluorinated alkylene of 1, 2, 3 or 4 carbon atoms and k
and m each independently represent a value of 0 to 4.
[0028] Fluorinated carboxylic acid of formula (VI) can be derived
from fluorinated olefins of the general formula:
R.sup.a.sub.f--(O).sub.t--CF.dbd.CF.sub.2 (VIa) wherein
R.sup.a.sub.f and t are as defined above. Compounds according to
formula (VIa) are well known in the art and include fluorinated
olefins such as perfluorinated alkyl vinyl compounds, vinyl ethers
in particular perfluorovinyl ethers and allyl ethers, in particular
perfluorinated allyl ethers.
[0029] Fluorinated carboxylic acids according to formula (VI)
wherein n is 0 can be prepared by reacting a fluorinated olefin of
formula (VIa) with a base. The reaction is generally carried out in
aqueous media. An organic solvent may be added to improve the
solubility of the fluorinated olefin. Examples of organic solvents
include glyme, tetrahydrofuran (THF) and acetonitrile. Additionally
or alternatively a phase transfer catalyst may be used. As a base,
use can be made of for example ammonia, alkali and earth alkali
hydroxides. Without intending to be bound by any theory, it is
believed, that the reaction proceeds according to the following
sequence when ammonia is used as a base:
R.sub.f--(O).sub.t--CF.dbd.CF.sub.2+NH.sub.3+H.sub.2O.fwdarw.R.sub.f--(O)-
.sub.t--CHF--COONH.sub.4+NH.sub.4F
[0030] The reaction is generally carried out between 0 and
200.degree. C., for example between 20-150.degree. C. and at a
pressure between about 1 bar up to about 20 bar. For further
purification, the obtained salts can be distilled via the free acid
or by first converting the acid into an ester derivative and then
distilling the ester derivative followed by hydolysis of the ester
to obtain the purified acid or salt thereof.
[0031] Fluorinated carboxylic acids of formula (VI) wherein n is 0
can also be prepared by reacting a fluorinated olefin of formula
(VIa) with a hydrocarbon alcohol in an alkaline medium and then
decomposing the resulting ether in acidic conditions thereby
forming the corresponding carboxylic acid. Suitable hydrocarbon
alcohols include aliphatic alcohols such as lower alkanols having 1
to 4 carbon atoms. Specific examples include methanol, ethanol and
butanol including t-butanol. The reaction of the fluorinated olefin
with the alcohol in an alkaline medium may be carried out as
described in "Furin et al., Bull Korean Chem. Soc. 20, 220 [1999]".
The reaction product of this reaction is an ether derivative of the
fluorinated olefin. This resulting ether can be decomposed under
acidic conditions as described in "D. C. England, J. Org. Chem. 49,
4007 (1984)" to yield the corresponding carboxylic acid or salt
thereof.
[0032] To prepare fluorinated carboxylic acids of formula (VI)
wherein n is 1, a free radical reaction of the fluorinated olefin
of formula (VIa) with methanol may be carried out followed by an
oxidation of the resulting reaction product. The free radical
reaction is typically carried out using a free radical initiator as
is typically used in a free radical polymerization reaction.
Examples of suitable free radical initiators include persulfates
such as for example ammonium persulfate. Detailed conditions of the
free radical reaction of the fluorinated carboxylic acid with an
alcohol can be found in "S. V. Sokolov et al., Zh. Vses. Khim Obsh
24, 656 (1979)". The resulting alcohol derivative of the
fluorinated olefin can be chemically oxidized with an oxidizing
agent to the corresponding carboxylic acid. Examples of oxidizing
agents include for example potassium permanganate, chromium (VI)
oxide, RuO.sub.4 or OSO.sub.4 optionally in the presence of NaOCl,
nitric acid/iron catalyst, dinitrogen tetroxide. Typically the
oxidation is carried out in acidic or basic conditions at a
temperature between 10 and 100.degree. C. In addition to chemical
oxidation, electrochemical oxidation may be used as well.
[0033] In another embodiment, the fluorinated carboxylic acid
corresponds to the following formula:
R.sub.f.sup.b--(O).sub.t--CFH--CF.sub.2--O--R--G (VII) wherein
R.sub.f.sup.b represents a linear partially or fully fluorinated
aliphatic group optionally interrupted with one or more oxygen
atoms, R is an aliphatic hydrocarbon group, G represents a
carboxylic acid or salt thereof, t is 0 or 1. Particular examples
for R include a methylene group or an ethylene group.
[0034] In a particular aspect of this embodiment, the R.sub.f.sup.b
is selected from the group consisting of linear perfluorinated
aliphatic groups of 1 to 6 carbon atoms, preferably having 1 to 4
carbon atoms, perfluorinated groups of the formula
R.sub.f.sup.1--[OR.sub.f.sup.2].sub.p--[OR.sub.f.sup.3].sub.q--
wherein R.sub.f.sup.1 is a linear perfluorinated aliphatic group of
1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, R.sub.f.sup.2
and R.sub.f.sup.3 each independently represents a linear
perfluorinated alkylene of 1, 2, 3 or 4 carbon atoms and p and q
each independently represent a value of 0 to 4 and wherein the sum
of p and q is at least 1 and perfluorinated groups of the formula
R.sub.f.sup.4--[OR.sub.f.sup.5].sub.k--[OR.sub.f.sup.6].sub.m--O--CF.sub.-
2-- wherein R.sub.f.sup.4 is a linear perfluorinated aliphatic
group of 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms,
R.sub.f.sup.5 and R.sub.f.sup.6 each independently represents a
linear perfluorinated alkylene of 1, 2, 3 or 4 carbon atoms and k
and m each independently represent a value of 0 to 4.
[0035] Fluorinated carboxylic acids according to formula (VII) may
be prepared through the preparation of an intermediate of formula
(VIIa): R.sub.f.sup.b--(O).sub.t--CFH--CF.sub.2--O--R--Z wherein
R.sub.f.sup.b, t and R have the same meaning as defined above. Z
represents a carboxylic acid ester or a carboxylamide.
[0036] The intermediate compound according to formula (VIa) can be
prepared by reacting a fluorinated olefin of the general formula
(VIa) with an organic compound of the formula HO--R--Z (VIIb)
wherein Z and R are as defined above. Compounds according to
formula (VIIb) are well known in the art and/or are commercially
available. The reaction of compound (VIa) with compound (VIIb) is
typically carried out in the presence of a base although it is also
possible to carry out the reaction under acidic or neutral
conditions. Suitable bases include carbonates such as potassium
carbonate, sodium carbonate and lithium carbonate, hydroxides,
alkoholates etc. The amount of base used may vary widely. For
example a catalytic amount may be used. Generally the amount of
base used will be about at least 1 or 2% by weight based on the
amount of reactant of formula (VIIb). In a particular embodiment,
the amount of base can be up to 2 times the molar amount of the
reactant of formula (VIIb). The reaction is typically carried out
in an aprotic solvent such as for example, tetrahydrofuran,
acetonitrile, glyme, diglyme etc. Further suitable aprotic solvents
are disclosed in DE 3828063. The reaction is typically carried out
a temperature between 0 and 200.degree. C., for example between 10
and 150.degree. C. The reaction is generally carried out at an
ambient pressure (1 bar) or up to 20 bar. Following the reaction,
the resulting compound may be isolated and purified by
distillation.
[0037] The fluorinated carboxylic acids of formula (VII) can be
readily prepared by hydrolyzing the intermediate compound of
formula (VIIa) above. In formula (VIa) above, Z represents a
carboxylic acid ester or a carboxylamide. Typically a carboxylic
acid ester is used. In one embodiment, the ester can be an
aliphatic ester, e.g. an alkyl ester in which the number of carbon
atoms in the alkyl group are from 1 to 4. Hydrolysis of the
intermediate compound may be carried out under acidic or basic
conditions and is generally carried out in an alcoholic acidic or
basic solution of the intermediate compound. Alternatively the
intermediate compound may be hydrolysed in an acidic or basic
solution of other water miscible organic solvents such as ketones,
ethers etc. Typically, a basic alcoholic solution is used such as
for example a methanol or ethanol solution containing an alkali
metal hydroxide as the base. Typically the hydrolysis is carried
out at room temperature but it is also possible to use elevated
temperatures of for example up to the boiling point of the
solution.
[0038] Alternatively, the fluorinated surfactant may be prepared by
reacting the fluorinated olefin of formula (VIa) above with a
hydroxy substituted carboxylic acid or salt thereof. Thus, in
accordance with this embodiment the fluorinated olefin of formula
(VIa) is reacted with a compound of the formula: HO--R-G (VIIc)
wherein G is a carboxylic acid group or salt thereof and R is as
defined above. The reaction of a fluorinated olefin of formula
(VIa) with a hydroxy compound or formula (VIIc) can be carried out
under the same conditions described above for the reaction with
compounds of formula (VIIb).
[0039] In a still further embodiment, the fluorinated carboxylic
acid corresponds to one of the following formulas:
R.sub.f.sup.c--(OCF.sub.2).sub.u--O--(CF.sub.2).sub.v-AC (VIII)
wherein u is an integer of 1 to 6, v is an integer of 1 to 6,
R.sub.f.sup.c represents a linear perfluorinated aliphatic group of
1, 2, 3 or 4 carbon atoms and AC represents a carboxylic acid group
or salt thereof, and
R.sub.f.sup.c--O--(CF.sub.2).sub.y--O-L.sup.1-AC (IX) wherein y has
a value of 1, 2, 3, 4, 5 or 6, L.sup.1 represents a linear
perfluorinated alkylene of 1, 2, 3, 4, 5 or 6 carbon atoms or a
linear partially fluorinated alkylene having 1 to 6 carbon atoms
and 1 or 2 hydrogen atoms, R.sub.f.sup.c is as defined in above
formula (VIII) and AC represents a carboxylic acid group or salt
thereof. A particular example for L.sup.1 includes a group of the
formula --CFH--. Particular compounds according to formula (IX)
include those wherein R.sub.f.sup.c represents CF.sub.3CFH--. Such
groups can be obtained from decarboxylation of --CF(CF.sub.3)COOX
groups (X is a cation) in the presence of a protic substance as
described in JOC 34, 1841 (1969).
[0040] Fluorinated carboxylic acids of formula (VIII) are
commercially available from Anles Ltd., St. Petersburg, Russia.
These compounds may be prepared for example as described by Ershov
and Popova in Fluorine Notes 4(11), 2002. Also, these fluorinated
carboxylic acids typically form as byproducts in the manufacturing
of hexafluoropropylene oxide by direct oxidation of
hexafluoropropylene.
[0041] Fluorinated carboxylic acids according to formula (IX) can
be derived from reactants that are also used in the manufacturing
of fluorinated vinyl ethers as described in U.S. Pat. No.
6,255,536.
[0042] In another embodiment acid fluorides of formula (X) are
reacted with a metal fluoride like KF or CsF: R.sub.f.sup.g--COF
(X) wherein R.sub.f.sup.g is a partially or perfluorinated linear
aliphatic chain optionally interrupted with one or more oxygen
atoms. This reaction results in an alkoxylate that can be further
reacted with a carboxylic acid derivative of formula (XI)
Y--(CH.sub.2).sub.n--Q (XI) wherein Y represents a leaving group
like iodide, bromide, chloride, mesylate, tosylate and the like, n
is an integer from 1 to 3, and Q represents a carboxyl acid group
or a lower alkyl ester. The reaction results in fluorinated
carboxylic acid derivatives of formula (XII)
R.sub.f.sup.g--CF.sub.2--O--(CH.sub.2).sub.nQ (XII) with
R.sub.f.sup.g n, and Q having the same meaning as above. The
corresponding salts can be obtained by saponification.
[0043] In yet a further embodiment the fluorinated carboxylic acids
correspond to formula (XIII)
CF.sub.3--CF.sub.2--O--R.sub.f.sup.h--COOX (XIII) with
R.sub.f.sup.h representing a linear partially or fully fluorinated
linear carbon chain of 1 to 8 carbon atoms optionally interrupted
with one or more oxygen atoms, for example a perfluorinated linear
aliphatic group of 1 to 6 carbon atoms, for example 1, 2, 3 or 4
carbon atoms and X is a monovalent cation. Compounds of this
formula can be made by conversion of diacid difluorides of formula
(XIV) in the presence of e.g. antimony pentafluoride.
FOC--CF(CF.sub.3)--O--R.sub.f.sup.h--COF (XIV)
[0044] This conversion may be carried out at elevated temperature
according to the method described in U.S. Pat. No. 3,555,100
resulting preferably in the decarbonylation of the secondary COF
group. The resulting mono acid fluoride can be converted to the
corresponding salt using well known methods.
[0045] Fluorinated carboxylic acids having a --O--CF.sub.2--COOX
group can be obtained from the corresponding vinyl ethers
--O--CF.dbd.CF.sub.2. Reaction of the vinyl ether with oxygen
according to U.S. Pat. No. 4,987,254 results in acid fluorides
carrying a --O--CF.sub.2COF group which can be readily converted to
the corresponding acid or salt.
[0046] Specific examples of compounds according to formula (I)
include the following:
R.sub.fO--CHF--COOH
[0047] C.sub.3F.sub.7--O--CHF--COOH [0048]
CF.sub.3--O--CF.sub.2CF.sub.2--CF.sub.2--O--CHF--COOH [0049]
CF.sub.3CF.sub.2CF.sub.2--O--CF.sub.2CF.sub.2--CF.sub.2--O--CHF--COOH
[0050] CF.sub.3--O--CF.sub.2--CF.sub.2--O--CHF13 COOH [0051]
CF.sub.3--O--CF.sub.2--O--CF.sub.2--CF.sub.2--O--CHF--COOH [0052]
CF.sub.3--(O--CF.sub.2).sub.2--O--CF.sub.2--CF.sub.2--O--CHF--COOH
[0053]
CF.sub.3--(O--CF.sub.2).sub.3--O--CF.sub.2--CF.sub.2--O--CHF--COO-
H R.sub.f--O--CHF--CF.sub.2--COOH [0054]
CF.sub.3--O--CHF--CF.sub.2--COOH [0055]
CF.sub.3--O--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--COOH [0056]
CF.sub.3--CF.sub.2--O--CHF--CF.sub.2--COOH [0057]
CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--COOH
[0058]
CF.sub.3--O--CF.sub.2--O--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--COOH
[0059]
CF.sub.3--(O--CF.sub.2).sub.2--O--CF.sub.2--CF.sub.2--O--CHF--CF.-
sub.2--COOH [0060]
CF.sub.3--(O--CF.sub.2).sub.3--O--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--C-
OOH R.sub.f--O--CF.sub.2--CHFCOOH [0061]
CF.sub.3--O--CF.sub.2--CHF--COOH [0062]
C.sub.3F.sub.7--O--CF.sub.2--CHF--COOH [0063]
CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--COOH
[0064]
CF.sub.3--O--CF.sub.2--O--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--COOH
[0065]
CF.sub.3--(O--CF.sub.2).sub.2--O--CF.sub.2--CF.sub.2--O--CF.sub.2-
--CHF--COOH [0066]
CF.sub.3--(O--CF.sub.2).sub.3--O--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--C-
OOH R.sub.f--O--CF.sub.2--CHF--CF.sub.2COOH [0067]
CF.sub.3--O--CF.sub.2--CHF--CF.sub.2--COOH [0068]
C.sub.2F.sub.5--O--CF.sub.2--CHF--CF.sub.2--COOH [0069]
C.sub.3F.sub.7--O--CF.sub.2--CHF--CF.sub.2--COOH [0070]
CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--CF.sub.2--CO-
OH [0071]
CF.sub.3--O--CF.sub.2--O--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--CF.sub.2--
-COOH [0072]
CF.sub.3--(O--CF.sub.2).sub.2--O--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--C-
F.sub.2--COOH [0073]
CF.sub.3--(O--CF.sub.2).sub.3--O--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--C-
F.sub.2--COOH
R.sub.f--(O).sub.m--CHF--CF.sub.2--O--(CH.sub.2).sub.n--COOH n=1,2
or 3; m=0 or 1 [0074] CF.sub.3--O--CHF--CF.sub.2--O--CH.sub.2--COOH
[0075]
CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--O--CH.sub.2--
-COOH [0076] C.sub.3F.sub.7--O--CHF--CF.sub.2--O--CH.sub.2--COOH
[0077]
C.sub.3F.sub.7--O--CHF--CF.sub.2--O--CH.sub.2--CH.sub.2--COOH
[0078]
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--OCH.sub.2COOH
[0079]
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2-
--OCH.sub.2COOH [0080]
C.sub.3F.sub.7--O--CF.sub.2--CHF--CF.sub.2--OCH.sub.2COOH [0081]
CF.sub.3--CHF--CF.sub.2--O--CH.sub.2COOH [0082]
C.sub.3F.sub.7--CF.sub.2--CHF--CF.sub.2--OCH.sub.2--COOH [0083]
CF.sub.3--O--CF.sub.2--CF.sub.2--O--CH.sub.2--COOH [0084]
CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CF.sub.2--CF.sub.2--O--CH.s-
ub.2--COOH [0085]
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--O--CH.sub.2--COOH [0086]
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--O--CH.sub.2--CH.sub.2--COOH
[0087]
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--O--CF.sub.2--CF.sub.2--OCH-
.sub.2COOH [0088]
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CF.sub.2--CF.sub.2--O-
CH.sub.2COOH [0089]
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--CF.sub.2--OCH.sub.2COOH
[0090] C.sub.4F.sub.9--O--CH.sub.2--COOH [0091]
C.sub.4F.sub.9--O--CH.sub.2--CH.sub.2--COOH [0092]
C.sub.3F.sub.7--O--CH.sub.2COOH [0093]
C.sub.6F.sub.13--OCH.sub.2--COOH
R.sub.f--O--CF.sub.2--CF.sub.2--COOH [0094]
CF.sub.3--O--CF.sub.2--CF.sub.2--COOH [0095]
C.sub.2F.sub.5--O--CF.sub.2--CF.sub.2--COOH [0096]
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--COOH [0097]
C.sub.4F.sub.9--O--CF.sub.2--CF.sub.2--COOH
R.sub.f--(O--CF.sub.2).sub.u--O--CF.sub.2--COOH with u being as
defined above [0098]
CF.sub.3--(O--CF.sub.2).sub.3--O--CF.sub.2--COOH [0099]
CF.sub.3--(O--CF.sub.2).sub.2--O--CF.sub.2--COOH [0100]
CF.sub.3--(O--CF.sub.2).sub.1--O--CF.sub.2--COOH
R.sub.f--(O--CF.sub.2--CF.sub.2).sub.k--O--CF.sub.2--COOH with k
being 1, 2 or 3 [0101]
CF.sub.3--(O--CF.sub.2--CF.sub.2).sub.1--O--CF.sub.2--COOH [0102]
C.sub.2F.sub.5--(O--CF.sub.2--CF.sub.2).sub.1--O--CF.sub.2--COOH
[0103]
C.sub.3F.sub.7--(O--CF.sub.2--CF.sub.2).sub.1--O--CF.sub.2--COOH
[0104]
C.sub.4F.sub.9--(O--CF.sub.2--CF.sub.2).sub.1--O--CF.sub.2--COOH
[0105]
C.sub.2F.sub.5--(O--CF.sub.2--CF.sub.2).sub.2--O--CF.sub.2--COOH
[0106] CF.sub.3--(O--CF.sub.2--CF.sub.2).sub.2--O--CF.sub.2--COOH
[0107]
C.sub.3F.sub.7--(O--CF.sub.2--CF.sub.2).sub.2--O--CF.sub.2--COOH
[0108]
C.sub.4F.sub.9--(O--CF.sub.2--CF.sub.2).sub.2--O--CF.sub.2--COOH
R.sub.f--O--CF.sub.2--COOH [0109] C.sub.3F.sub.7--O--CF.sub.2--COOH
[0110] CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CF.sub.2--COOH
CF.sub.3--CHF--O--(CF.sub.2).sub.o--COOH with o being an integer of
1, 2, 3, 4, 5 or 6 [0111] CF.sub.3CFH--O--(CF.sub.2).sub.3--COOH
[0112] CF.sub.3CFH--O--(CF.sub.2).sub.5--COOH
CF.sub.3--CF.sub.2--O--(CF.sub.2).sub.o--COOH with o being as above
[0113] CF.sub.3--CF.sub.2--O--(CF.sub.2).sub.3COOH [0114]
CF.sub.3--CF.sub.2--O--(CF.sub.2).sub.5COOH
[0115] In the above generic formulas, R.sub.f has the meaning as
defined above in respect of generic formula (I). It is understood
that while the above list of compounds only lists the acids, the
corresponding salts, in particular the NH.sub.4.sup.+, potassium,
sodium or lithium salts can equally be used.
Scrubber Composition
[0116] In accordance with the present invention, the exhaust gas
stream is contacted with a composition capable of at least
partially removing the fluorinated carboxylic acid from the exhaust
gas stream. For convenience, this composition will be referred to
hereinafter as "scrubber composition".
[0117] In accordance with one embodiment, the scrubber composition
is a scrubber liquid. The exhaust gas is typically contacted with
the scrubber liquid at a temperature so as to maximize solubility
of the fluorinated carboxylic acid in the scrubber liquid. A
typical temperature range may be from 10.degree. C. to 80.degree.
C. Scrubber liquids include aqueous liquids such as demineralized
water, aqueous alkaline solutions and organic solvents such as for
example glycol ether solvents. Suitable aqueous alkaline solutions
include diluted alkali solution and high-density alkali solutions.
The latter may cause the fluorinated carboxylic acid to separate
out as a separate phase, thus allowing easy recovery and recycling
of the fluorinated carboxylic acid.
[0118] In a particular embodiment, the density of the alkaline
scrubbing solution is set to a value which is higher than the
density of the precipitating salts of fluorocarboxylic acids, so
that these separate out as an upper phase on the high-density
scrubbing solution in a settling tank and are ejected. The
scrubbing solution may be taken off at the bottom and returned
directly to the scrubbing process. The density of the alkaline
scrubbing solution should generally be above 1.15 g/cm.sup.3,
preferably above 1.3 g/cm.sup.3, depending on the temperature in
the scrubber.
[0119] Typically, the alkaline compound selected is typically an
alkali metal hydroxide, preferably potassium hydroxide solution and
in particular sodium hydroxide solution, the concentration being
such that the density is above 1.15 g/cm.sup.3. With potassium
hydroxide solution, this is generally the case at a concentration
of above 16% and with sodium hydroxide solution this is generally
the case at a concentration of above 14%. Mixtures of different
alkalis are also possible.
[0120] If lower concentrations of alkali metal hydroxide are
desired, the scrubbing solution density of at least 1.15 g/cm.sup.3
can also be achieved by addition of a salt. Salts which may be used
are quite generally inorganic compounds which do not form sparingly
soluble hydroxides in the alkaline environment. These are, in
particular, alkali metal salts such as sodium or potassium
chloride, bromide or sulfate. However, since chloride ions can
cause corrosion when metals are used as material for the work-up
equipment, other salts, such as sulfates, are generally preferred
to set the density of the scrubbing solution. Advantageously, a
salt is selected having the same cation as the alkaline compound,
when sodium hydroxide solution is used, therefore, preferably
sodium sulfate. Mixtures of salts are also possible. The lighter,
upper phase containing the salts of the highly fluorinated
carboxylic acids occurs in the form of a salt paste to which
alkaline aqueous medium, that is alkali metal hydroxide and, if
appropriate, also the added salt, still adheres.
[0121] In a particular embodiment, a potassium carbonate solution
having a density of at least 1.15 g/cm.sup.3 is used as a scrubbing
composition. The density may e.g. be from 1.2 to 1.4
g/cm.sup.3.
[0122] If the upper phase which has separated out is collected, for
example in a tank, it may be observed, that after standing for
several hours, further enrichment of the salts of the highly
fluorinated carboxylic acids occurs, by at least two phases forming
again. By analysis, it is established in which phase the salts of
the highly fluorinated carboxylic acids are contained and the other
phases are preferably returned to the process.
[0123] In a particular embodiment, an aqueous solution of alkali
hydroxide having a concentration of the alkali hydroxide between
0.01 and 10% by weight, is used such as for example sodium or
potassium hydroxide solutions.
[0124] In another embodiment, demineralised water is used as the
scrubber liquid. In this case, the scrubber solution is preferably
recirculated until the fluorinated carboxylic acid concentration
reaches about 500 to about 5000 parts per million by weight (ppm),
more preferably about 1000 to about 4000 ppm, and most preferably
about 2000 to about 3000 ppm. Foaming in the scrubber system
typically provides a practical limit for the concentration of
fluorinated carboxylic acid in the scrubber solution.
[0125] The scrubber solution may then be concentrated. Preferably
this is accomplished by passing the scrubber solution through one
or more reverse-osmosis (RO) units to increase the concentration of
fluorinated carboxylic acid to about 1 to about 35 wt. %, more
preferably about 5 to about 30 wt. %, even more preferably about 10
to about 25 wt. %, and most preferably about 20.+-.5 wt. %. The
nature of the membrane in the RO units may require adjustment of
the pH of the scrubber solution to operate efficiently. The
resulting concentrated scrubber solution typically also contains
several hundred ppm fluoride ion, and frequently has a colour that
varies from light tan to brown, indicative of other impurities,
including organic impurities.
[0126] Therefore the recovered concentrated scrubber solution
should preferably be contacted with alumina to reduce fluoride
concentration. This may be done, for example, by passing the
concentrated scrubber solution through a bed packed with alumina,
the preferred method, or by slurrying the fluorinated carboxylic
acid solution with alumina and then separating the solution from
the alumina. This solution is referred to herein as recovered
fluorinated carboxylic acid solution. The temperature of
concentrated scrubber solution during the alumina treatment may be
from about 5.degree. C. to about 90.degree. C., preferably about
10.degree. C. to about 50.degree. C., and more preferably about
15.degree. C. to about 30.degree. C. Contact time if the alumina
bed method is used is somewhat dependent upon temperature but is in
the range of about 5 to about 60 minutes. The concentrated scrubber
solution feed to the alumina preferably has a pH of about 4 to
about 7, more preferably at about 5 to about 6.
[0127] The so obtained recovered fluorinated carboxylic acid may be
re-used in the polymerization of fluorinated monomers.
[0128] Alternatively, the scrubber solution, which may or may not
have been concentrated, may be contacted with adsorbent particles
to adsorb the fluorinated carboxylic acid from the scrubber
solution. By the term `adsorbent particles` in connection with the
present invention is meant particles that are capable of physically
adsorbing the fluorinated surfactant by whatever mechanism of
physical adsorption including but not limited to ionic interactions
causing physical adsorption. Accordingly, the term `adsorbent
particles` include ion exchange resins, which typically bind
fluorinated surfactants having ionic groups as a result of an ion
exchange process although the adsorption to the exchange resin may
also occur by a physical adsorption process other than the ion
exchange process.
[0129] Suitable adsorbent particles further include activated
carbon, silica gel, clays and zeolites. Conveniently used are
activated carbon particles. The shape of the adsorbent particles is
not particularly critical. For example, the adsorbent particles may
have a plate shape, can be spherical, cylindrical or they can be
rods. Also, adsorbent particles having a variety of different
shapes may be used as a mixture. The size of the adsorbent
particles is typically between 0.05 mm and 20 mm, generally between
0.1 and 10 mm. A practical range is between 0.5 and 5 mm. The
adsorbent particles typically adsorb the fluorinated acid
surfactant on their surface and it will thus generally be preferred
to optimize the specific surface area of the particles, i.e. the
amount of surface per unit of weight. Typically, the specific
surface area of the adsorbent particles will be between 10 and 5000
m.sup.2/g, generally between 100 and 3000 m.sup.2/g with a
practical range being from 300 to 2000 m.sup.2/g.
[0130] Additionally, anion exchange resin particles can be used as
adsorbent particles. Examples of anion exchange resin that can be
used to adsorb a fluorinated carboxylic acid include strong, medium
strong as well as weak basic anion exchange resins. The terms
strong, medium strong and weak basic anion exchange resin are
defined in "Encyclopedia of Polymer Science and Engineering", John
Wiley & Sons, 1985, Volume 8, page 347 and "Kirk-Othmer", John
Wiley & Sons, 3.sup.d edition, Volume 13, page 687. Strong
basic anion exchange resin typically contain quaternary ammonium
groups, medium strong resins usually have tertiary amine groups and
weak basic resins usually have secondary amines as the anion
exchange functions. Examples of anion exchange resins that are
commercially available for use in this invention include
AMBERLITE.RTM. IRA-402, AMBERJET.RTM. 4200, AMBERLITE.RTM. IRA-67
and AMBERLITE.RTM. IRA-92 all available from Rohm & Haas,
PUROLITE.RTM. A845 (Purolite GmbH) and LEWATIT.RTM. MP-500 (Bayer
AG).
[0131] According to a further embodiment, an aqueous scrubber
liquid may be used that includes a quaternary ammonium salt of the
general formula: R.sub.4N.sup.+A.sup.- wherein each R-group
independently represents a aliphatic or aromatic hydrocarbon group
and wherein A.sup.- represents an anion. Typical R-groups include
alkyl groups of 1 to 16 carbon atoms, aryl of 6-10 carbon atoms or
aralkyl of 7-11 carbon atoms. Typically, the sum of the carbon
atoms in the R-groups equals at least 15. Typically, the anion is a
halide anion such as chloride or bromide but any other anion may be
useful as well.
[0132] Typical examples of quaternary ammonium compounds according
to the above formula are di-n-decyldimethylammonium chloride,
hexadecyltrimethylammonium chloride,
n-tetradecylbenzyldimethylammonium chloride,
n-octyldodecyldimethylammonium chloride, and the like.
Hexadecyltrimethylammonium chloride is preferred. The analogous
bromides may also be used. Typically, the ammonium compound will
form the corresponding ammonium salt of the fluorinated carboxylic
acid when the exhaust gas stream is contacted with a scrubber
liquid containing the ammonium compound. The so formed ammonium
salt of the fluorinated carboxylic acid may then be recovered from
the scrubber solution by extraction with an organic solvent,
typically a chlorinated solvent. In one embodiment, the extraction
step is carried out simply by adding a chlorinated hydrocarbon
liquid (liquid at ordinary room temperature, i.e., about 22.degree.
C.), e.g., di- or tri- chloromethane, and agitating at room
temperature for a short time. The bulk of the quaternary ammonium
salt transfers then into the chlorinated hydrocarbon organic
layer.
[0133] In a still further embodiment, the scrubber composition may
comprise adsorbent particles such as disclosed above. In this
embodiment, the exhaust gas stream is thus contacted with adsorbent
particles to which the fluorinated carboxylic acid gets adsorbed.
In a practical embodiment, the adsorbent particles include
activated carbon particles, polyphenylenoxide (e.g. Tenax.RTM.),
silica, clays and zeolites. In another embodiment, the adsorbent
particles comprise an anion exchange resin. In the latter case, it
will generally be preferred that the anion exchange resin be held
in a wet state such that the fluorinated carboxylic acid can adsorb
effectively on the anion exchange resin.
[0134] Depending on the particular scrubber composition used, the
fluorinated carboxylic acid may be recovered therefrom in a variety
of ways and subsequently be purified by distillation and/or
esterification to recycle the fluorinated carboxylic acid or salt
thereof in a sufficiently pure form such that it can be re-used in
the polymerization of fluorinated monomers. In one embodiment, the
fluorinated carboxylic acid may be recovered from a scrubber
solution by contacting the latter with adsorbent particles capable
of adsorbing the fluorinated carboxylic acid. Suitable adsorbent
particles include those mentioned above.
[0135] The fluorinated carboxylic acids that are adsorbed on an
adsorbent particle may be recovered therefrom by eluting the loaded
adsorbent particles with an eluting liquid capable of desorbing
and/or dissolving the fluorinated carboxylic acid or a derivative
thereof. The nature and composition of the eluting liquid typically
depends on the nature of the adsorbent particles to which the
fluorinated carboxylic acid is adsorbed and typically includes an
organic solvent.
[0136] In one embodiment, the fluorinated carboxylic acid may be
recovered from strongly, medium strong or weak basic anion exchange
resin particles. The terms strong, medium strong and weak basic
anion exchange resin are defined in "Encyclopedia of Polymer
Science and Engineering", John Wiley & Sons, 1985, volume 8,
page 347 and "Kirk-Othmer", John Wiley & Sons, 3.sup.rd
edition, Volume 13, page 687. Strong basic anion exchange resins
typically contain quaternary ammonium groups, medium strong resins
usually have tertiary amine groups and weak basic resins usually
have secondary amines as the anion exchange functions.
[0137] Suitable eluting liquids for eluting the fluorinated
carboxylic acids from basic anion exchange resin particles include
a mixture of a mineral acid and a water miscible organic solvent.
Suitable mineral acids are all those the anions of which confer a
salt form upon the anion exchanger (anion form) which is
appropriate to the further adsorption of fluorinated emulsifying
acids. Under the conditions of elution their oxidation strength
should generally be so low that the anion exchanger will not be
damaged oxidatively. Mineral acids that can be used include, for
example ortho-, meta-, and diphosphoric acid, nitric acid,
hydrofluoric acid and preferably hydrochloric acid and sulfuric
acid.
[0138] Suitable organic solvents include polar organic solvents
such as alcohols, aliphatic or aromatic ethers, nitriles, amides,
sulfoxides, ketones and carboxylic acid esters. Preferred solvents
include those that are substantially miscible with water, i.e.
miscible to at least 40% by volume when mixing equal volumes, or
solvents that are completely miscible with water. Solvents of this
type are especially aliphatic alcohols having from 1 to 4 carbon
atoms, preferably methanol and ethanol, as well as mono- and
dimethyl ethers and mono- and diethyl ethers of ethylene glycol or
of the corresponding monoethers of polyglycols having a chain
length up to that of decaethylene glycol. It is likewise possible
to use mixtures of the aforesaid solvents.
[0139] A typical eluting liquid may be prepared from the mineral
acid and the organic solvent to be used, the acid concentration of
which, calculated on the total mixture, is adjusted in the range of
from 0.5 to 10 N, preferably 0.5 to 2 N. In said mixture the
proportion of mineral acid (including the water portion) to solvent
ranges from 1:0.25 to 1:20, preferably 1:3 to 1:10 parts by
volume.
[0140] For a quantitative elution of the adsorbed fluorinated
carboxylic acids 50 to 500 and preferably 100 to 225 parts by
volume, calculated on 100 parts of anion exchanger matrix, of the
mixture of mineral acid and organic solvent is typically used.
[0141] When the elution is terminated the eluate may separate into
two layers of which the lower layer having the higher specific
gravity contains practically the entire amount of fluorinated
carboxylic acid. The lower layer may neutralized with dilute,
usually 2 N sodium hydroxide solution and the fluorinated
carboxylic acid is typically precipitated in compact form and easy
to separate by adding the neutralized phase while stirring to
dilute hydrochloric acid.
[0142] In another embodiment the eluting mixture for the elution of
fluorinated carboxylic acid adsorbed to an anion exchange resin
comprises a) water, b) a compound of the formula M-X in which M is
an alkali metal or alkyl ammonium ion, and X is hydroxyl, fluoride
or chloride, and c) at least one organic solvent capable of
dissolving the other components a) and b) and thus provides a
sufficient quantity of anions X for the elution of the fluorinated
carboxylic acid from the anion exchanger resin.
[0143] In a particular aspect of this embodiment, the eluting
liquid has the following composition: [0144] a) from 15 to 40% of
water, [0145] b) from 1 to 10 of the compound M-A, and [0146] c)
from 60 to 70% of the solvent.
[0147] In another aspect, the eluting mixture has the following
composition:
[0148] a) from 18 to 35% of water,
[0149] b) from 2 to 8% of M-A, and
[0150] c) from 60 to 70% of solvent.
[0151] Useful solvents include those mentioned above. Suitable
cations M include lithium, sodium, potassium, tetramethylammonium
and tetraethylammonium, and the preferred anion A is hydroxyl.
[0152] In yet a further embodiment, the fluorinated carboxylic acid
may be recovered from a strongly basic anion exchange resin using
an eluting liquid comprising an ammonium salt and a water miscible
organic solvent. The ammonium salt is typically one that
corresponds to the general formula: (NH.sub.4).sub.nA wherein A
represents an anion other than OH.sup.- and n equals the valence of
A. Examples of anions A include inorganic as well as organic
anions. Particular examples of inorganic anions include halogen or
halogen containing inorganic anions such as for example F.sup.-,
Cl.sup.-, Br.sup.-, I.sup.-, ClO.sub.4.sup.-, phosphates, sulfates,
sulphonates, carbonates including HCO.sub.3.sup.- and
CO.sub.3.sup.2-. Examples of organic anions include in particular
carboxylic anions such as for example HCOO.sup.- and
CH.sub.3COO.sup.-.
[0153] The amount of ammonium salt in the eluting liquid will
generally depend on the nature of the anion exchange resin and the
amount of fluorinated carboxylic acid adsorbed on the anion
exchange resin and/or the percentage of recovery that is desired. A
suitable amount of ammonium salt is generally at least 0.1% by
weight. According to a particular embodiment, the amount of
ammonium salt is between 0.1 and 5% by weight based on the total
weight of the composition used for eluting the exchange resin.
[0154] The eluting composition further includes a water-miscible
solvent. By `water miscible solvent` is generally meant an organic
solvent that has solubility in water of at least 5% by weight, for
example at least 10% by weight or at least 20% by weight. Suitable
water-miscible solvents are typically polar solvents including for
example alcohols, ketones, ethers and mixtures thereof. Particular
examples of solvents include lower alkanols having between 1 and 6
carbon atoms such as for example methanol, ethanol and propanol;
glycols, mono- and dialkyl ethers or monoglycol and diglycol
wherein the alkyl groups have between 1 and 4 carbon atoms; ketones
such as acetone and methyl ethyl ketone. The amount of water
miscible organic may vary widely but should generally be enough to
dissolve the ammonium salt. The amount of water-miscible organic
solvent is generally at least 50% by weight of the total weight of
the eluting composition. Exemplary ranges are 50 to 99.9% by
weight, or between 60 and 90% by weight or between 90 and 98% by
weight.
[0155] The eluting liquid comprising the ammonium salt and a
water-miscible solvent may contain further components that may aid
in the recovery of the fluorinated carboxylic acid from the anion
exchange resin. In one particular embodiment, the eluting
composition further comprises water. Water may for example be used
in the eluting composition in an amount of up to 45% by weight, for
example in an amount of 0.1 to 40% by weight or in amount between 1
and 15% by weight or in an amount between 4 and 10% by weight.
[0156] A further component that may be present in the eluting
liquid is a base. Suitable bases that may be used are alkali metal
hydroxides such as for example sodium hydroxide and potassium
hydroxide. Other bases that may be used include earth alkali metal
hydroxides, aluminium hydroxide or alcolates such as for example
sodium methylate. When present, the amount of base included in the
composition is generally up to about 5% by weight. An exemplary
range is from 0.1 to 5% or from 0.5 to 2% by weight.
[0157] Further eluting liquids include those disclosed in U.S. Pat.
No. 6,642,415 and EP 1,323,677. The latter discloses eluting
liquids comprising an alkaline mixture of water and an organic
solvent. An aqueous ammonia solution as disclosed in U.S. Pat. No.
3,882,153 may also be used.
[0158] According to a further embodiment, the fluorinated
carboxylic acid may be recovered by mixing the adsorbent particles
with an alcohol and optionally an acid. The mixture is then
generally heated to cause esterification of the fluorinated
carboxylic acid with the alcohol so as to form an ester derivative
of the fluorinated carboxylic acid. The so obtained mixture may
then be distilled to form a distillate comprising the ester
derivative followed by separation of the ester derivative from the
distillate. Generally, the eluting liquid will also comprise
water.
[0159] Suitable alcohols that may be used include in particular
lower aliphatic alcohols having 1 to 5 carbon atoms such as
methanol, ethanol and propanol. However aromatic alcohols may be
used as well. Additionally, the alcohol may be added under the form
of a precursor of the alcohol. Such a precursor should however form
an alcohol under the conditions used to cause the esterification.
Suitable precursors of the alcohol may include compounds such as
ketals that readily form a corresponding alcohol under the acidic
conditions existing in the eluting liquid or mixture thereof with
the adsorbent particles. The acid used with the eluting fluid is
preferably an inorganic acid but the use of organic acids is not
excluded. Also, the acid is preferably a strong acid such as for
example sulphuric acid, hydrochloric acid, phosphoric acid or
nitric acid. The amount and nature of the acid used is typically
such that a pH of less than 4, preferably not more than 3 and more
preferably not more than 2 is attained in the mixture of eluting
liquid and adsorbent particles.
[0160] Depending on the amount of water present in the distillate
the ester derivative may separate out as a separate phase,
typically the lower phase, from the remainder of the distillate.
Thus the ester derivative can be easily separated from the
distillate and the remainder of the distillate can be re-introduced
into the mixture being distilled. Such a circulating regeneration
process thus allows a convenient regeneration of the adsorbent
particles with a minimal amount of eluting fluid being needed. The
received ester can be further purified by distilllation and is than
converted to the fluorinated acid salt by saponification typically
with ammonia. The eluated purified fluorinated carboxylic acid salt
will typically have a purity sufficient to allow use of the
compound in emulsion polymerization of fluorinated monomers. The
adsorbent particles can be regenerated several times before their
efficiency drops below an uneconomical level at which point the
adsorbent particles need to be disposed of.
[0161] The aforementioned elution methods may of course also be
used in cases where the scrubber composition itself comprises
adsorbent particles.
[0162] Following their recovery, the fluorinated carboxylic acids
can be purified to the desired high purity enabling re-use of the
fluorinated carboxylic acid in an aqueous emulsion polymerization.
A suitable purification method is disclosed in U.S. Pat. No.
5,312,935. Herein the liberated and dewatered carboxylic acids are
treated with oxidants like dichromates, peroxodisulfates or
permanganates at a temperature of about 60.degree. C. to the
boiling point of the mixture. The pure product is then isolated by
crystallization e.g. at low temperature or preferably by
distillation if desired under reduced pressure. Alternatively, the
method of WO2004/031141 may be used.
EXAMPLES
[0163] Test Method:
Content of Fluorinated Carboxylic Acid
[0164] The amount of fluorinated carboxylic acid in aqueous
solution was determined by conversion of the fluorinated emulsifier
into the methyl ester followed by an analysis with gas
chromatography (head space) using methyl ester of perfluorodecanoic
acid as an internal standard. The detection limit was about 10
ppm.
[0165] Particle Size
[0166] The latex particle size determination was conducted by means
of dynamic light scattering with a Malvern Zetazizer 1000 HAS in
accordance to ISO/DIS 13321. Prior to the measurements, the polymer
latexes as yielded from the polymerizations were diluted with 0.001
mol/L KCl-solution, the measurement temperature was 25.degree. C.
in all cases. The reported average is the Z-average particle
diameter. [0167] SSG: Standard specific gravity was measured
according ASTM 4894-04 [0168] Solid Content: Determination of solid
content was done by subjecting the latex sample to a temperature up
to 250.degree. C. for 30 min. Polymerization of Fluorinated
Monomers (Fluoroolefin) using a Fluorinated Carboxylic Acid
[0169] The polymerization experiments were performed in a 40 l
kettle equipped with an impeller agitator and a baffle. The kettle
was charged with 30 l of deionized water and set to 35.degree. C.;
the kettle was evacuated repeatedly to remove oxygen; Agitation
speed was set to 165 rpm. The oxygen free kettle was charged with
70 mmol fluorinated emulsifier (unless specified differently) as
listed in table 3 and the following materials were added: 0.5 ml of
a solution containing 40 mg of copper sulphate penta hydrate and 1
mg of conc. sulphuric acid; 15 g of a 25 w-% of aqueous ammonia
solution and 5.6 g of
CF.sub.3CF.sub.2CF.sub.2--O--CF(CF.sub.3)--CF2--O--CF.dbd.CF.sub.2
(PPVE-2). Finally the reactor was pressurized with
tetrafluoroethylene (TFE) to 0.2 MPa and 47 g of
hexafluoropropylene (HFP) were added. The kettle was then set to
1.5 MPa using TFE and 100 ml of an aqueous initiator solution
containing 140 mg of sodium disulfite followed by 100 ml of a
solution containing 340 mg of ammonium peroxodisulfate was pumped
into the reactor. The beginning of the polymerization is indicated
by a pressure drop. During polymerization the pressure was
maintained at 1.5 MPa by feeding TFE continuously. After 3.2 kg of
TFE had been added, the monomer valve was closed and the pressure
was released. The characteristics of the obtained polymer latices
are summarized in table 3.
[0170] 1000 ml of this polymer dispersion were coagulated by adding
20 ml hydrochloric acid under agitation. The coagulated material
was agglomerated with gasoline and washed repeatedly. The
agglomerated polymer was dried overnight at 200.degree. C. in a
vacuum oven; test data are given in table 3. TABLE-US-00001 TABLE 1
Emulsifiers used: C.sub.7F.sub.15COONH.sub.4 Comparative example
C-1 ##STR1## Comparative example C-2 ##STR2## Comparative example
C-3 CF.sub.3--O--(CF.sub.2).sub.3--O--CF.sub.2--COONH.sub.4
Compound 1 CF.sub.3--OCF.sub.2--O--CF.sub.2--COONH.sub.4 Compound 2
CF.sub.3--OCF.sub.2--OCF.sub.2--OCF.sub.2--COONH.sub.4 Compound 3
CF.sub.3--(OCF.sub.2).sub.3--OCF.sub.2--COONH.sub.4 Compound 4
C.sub.3F.sub.7--O--CF.sub.2--COONH.sub.4 Compound 5
CF.sub.3--O--CF.sub.2--CF.sub.2--COONH.sub.4 Compound 6
C.sub.2F.sub.5--O--CF.sub.2--CF.sub.2--COONH.sub.4 Compound 7
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--COONH.sub.4 Compound 8
C.sub.4F.sub.9--O--CF.sub.2--CF.sub.2--COONH.sub.4 Compound 9
C.sub.2F.sub.5--O--CF.sub.2--CF.sub.2--O--CF.sub.2--COONH.sub.4
Compound 10
CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--COONH.sub.4
Compound 11
CF.sub.3--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CHF--COONH.sub.4
Compound 12 C.sub.3F.sub.7--O--CFH--CF.sub.2COONH.sub.4 Compound 13
CF.sub.3--CFH--O--(CF.sub.2).sub.5--COONH.sub.4 Compound 14
CF.sub.3--CFH--O--(CF.sub.2).sub.3--COONH.sub.4 Compound 15
C.sub.3F.sub.7--O--CFH--CF.sub.2--O--CH.sub.2--COONH.sub.4 Compound
16 C.sub.3F.sub.7--O--CFH--COONH.sub.4 Compound 17
Preparation of Compound 1:
CF.sub.3OCF.sub.2CF.sub.2CF.sub.2OCF.sub.2COONH.sub.4
[0171] Oxidation of perfluorinated vinyl ethers with oxygen in the
presence of SbF.sub.5 was carried out as described in U.S. Pat. No.
4,987,254. The initially formed acid fluorides were esterified with
methanol and purified by distillation. The distilled esters were
converted to the corresponding ammonium salts by saponification
with aqueous ammonia. A dry flask equipped with a magnetic stirrer
bar, thermometer, dry ice reflux condenser, dropping funnel, and
gas inlet tube was charged with 5 g of graphite. The flask was
flushed with nitrogen and 332 g of
CF.sub.3OCF.sub.2CF.sub.2CF.sub.2OCF.dbd.CF.sub.2 were added at
room temperature. 2.6 g of SbF.sub.5 was added via the dropping
funnel and oxygen was charged to the flask at ambient pressure. An
exothermic reaction indicated the oxidation. Total reaction time
was 14 h. After the first hour 2.6 g and after 7 hours 3.5 g of
SbF.sub.5 were added. Esterification was achieved by slow addition
of 50 g of methanol to the reaction mixture. The resulting ester
was isolated from the batch by flash distillation after addition of
300 g water and 50 g methanol. The distillate formed two phases.
The lower phase was separated and the upper phase retuned to the
flask. 310 g of lower phase were collected. GC analysis showed a
content of 52% of
CF.sub.3OCF.sub.2CF.sub.2CF.sub.2OCF.sub.2COOCH.sub.3. Purification
via fractionated distillation resulted in 144 g pure ester with a
boiling point of 51.degree. C. at 52 mbar.
CF.sub.3OCF.sub.2CF.sub.2COOCH.sub.3 was isolated as by product.
Saponification of the ester with aqueous ammonia at 60-80.degree.
C. and removal of methanol by distillation resulted in an aqueous
solution of CF.sub.3OCF.sub.2CF.sub.2CF.sub.2OCF.sub.2COONH.sub.4.
All structures were confirmed by F-NMR spectra.
Preparation of Compound 5:
CF.sub.3CF.sub.2CF.sub.2OCF.sub.2COONH.sub.4
[0172] Using the procedures described in U.S. Pat. No. 4,987,254,
CF.sub.3CF.sub.2CF.sub.2OCF.dbd.CF.sub.2 was converted to
CF.sub.3CF.sub.2CF.sub.2OCF.sub.2COOCH.sub.3 (bp 102-104.degree.
C.). Saponification with aqueous ammonia and removal of methanol by
distillation resulted in an aqueous solution of
CF.sub.3CF.sub.2CF.sub.2OCF.sub.2COONH.sub.4. Structures were
confirmed by F-NMR spectra.
Preparation of Compound 17:
CF.sub.3CF.sub.2CF.sub.2OCHFCOONH.sub.4
[0173] A 2 liter glass flask equipped with a mechanical stirrer,
thermometer and reflux condenser (-80.degree. C.) is used. Heating
of the flask is provided by an electric heating mantle. The
conversion is carried out as a one pot reaction. 275 g
perfluoropropyl vinyl ether (PPVE), 280 g KOH, 602 g water, 151 g
t-butanol, and 10 g methyl trioctyl ammonium chloride are placed in
the flask. The three phase mixture is subjected to vigorous
stirring. After initial heating a moderate exothermic reaction
occours. Mixing is continued for nine hours. During this time the
internal temperature adjusts to 27-33.degree. C. Mixing is stopped
when the exothermic reaction ceases. The reaction mixture forms two
layers. The low temperature reflux condenser is replaced by a
standard reflux condenser. Sulfuric acid (392 g) is slowly added
without external cooling. The batch is heated to reflux. Unreacted
PPVE is vented. At about 80.degree. C. internal temperature gas
begins to evolve. Heating is continued until the gas evolution has
ceased. At this time the internal temperature reaches 101.degree.
C. The batch is cooled to RT and the reflux condenser is replaced
by a distillation device. No column is used. 110 g methanol is
added to the batch and distillation is started. The condensed
vapors form two layers. The lower layer is separated and the upper
layer is returned to the flask. Distillation is stopped when no
more lower phase is formed. In total, 234 g of lower phase are
collected. Fractionation of the lower phase yields 167 g of
C.sub.3F.sub.70CHFCOOCH.sub.3 with a boiling point of
120-122.degree. C. at ambient pressure.
[0174] Calculated yield: 59% based on total PPVE used; 70% based on
converted PPVE.
[0175] The ester is converted to the ammonium salt by reaction with
aqueous ammonia. Methanol is removed by fractionated distillation.
The resulting aqueous solution is used as an emulsifier in the
polymerization of fluorinated olefins.
Preparation of Compound 12:
CF.sub.3OCF.sub.2CF.sub.2CF.sub.2OCHFCOONH.sub.4
[0176] A glass flask equipped with a reflux condenser, thermometer,
and magnetic stirrer was used. Perfluoromethoxy propyl vinyl ether
(498 g), t-butanol (149 g), water (1007 g), potassium hydroxide
(280 g), and methyl trioctyl ammonium chloride (10 g) were added to
the flask. The resulting two phase mixture was heated to reflux for
16 hours under vigorous stirring. The mixture was cooled to room
temperature and sulphuric acid (588 g) was added. The two phase
mixture was heated again under vigorous stirring. At about
70.degree. C. gas began to evolve. Heating was continued until the
gas evolution ceased. The reflux condenser was replaced by a
distillation device which allowed the separation of a lower phase
while returning the upper phase to the flask. Methanol (150 g) was
added and the mixture was heated for distillation. Distillation was
carried out at ambient pressure without any intent for
rectification. The condensed vapors separated into two phases. The
lower phase was collected and the upper phase was returned to the
flask. Distillation was continued until no more lower phase
separated from the condensate. The combined crude ester (493 g) was
purified by fractionated distillation, resulting in 401 g
CF.sub.3O(CF.sub.2).sub.3OCHFCOOCH.sub.3 with a boiling point of 51
to 52.degree. C./22 mbar. This corresponds to a yield of 78%, based
on vinyl ether used. The ester was converted to the ammonium salt
by heating with aqueous ammonia and removal of methanol by
fractionated distillation.
[0177] Alternatively, the previous reaction was repeated but 36 g
of an aqueous solution containing 11 g of
CF.sub.3O(CF.sub.2).sub.3OCHFCOONH.sub.4 was used as phase transfer
catalyst instead of methyl trioctyl ammonium chloride. The mixture
was slowly heated to 70.degree. C. internal temperature. Total
reaction time was 26 hours. Work up was carried out as described
above. 438 g of distilled CF.sub.3O(CF.sub.2).sub.3OCHFCOOCH.sub.3
was received. This corresponds to a yield of 83% (calculation
includes the amount of phase transfer catalyst).
[0178] The conversion to the ammonium salt was carried out as
above.
Preparation of Compound 13:
C.sub.3F.sub.7OCHFCF.sub.2COONH.sub.4
[0179] a. Preparation of
CF.sub.3CF.sub.2CF.sub.2OCHFCF.sub.2CH.sub.2OH
[0180] In a 2 liter glass flask equipped with a stirrer,
thermometer, reflux condenser, and dropping funnel were placed 1008
g methanol, 266 g perfluoropropyl vinyl ether, and 9,2 g of
Rongalit.RTM. (sodium hydroxymethyl sulfinate). The reaction
mixture was heated to reflux, resulting in an internal temperature
of 29.degree. C. 7,1 g t-butyl hydroperoxide (70% in water) is
added in aliquots during a 9 h time frame. The internal temperature
reached 52.degree. C. at the end. The reaction mixture showed a
single liquid phase and some solids. The liquid was analyzed by GC
and indicated a content of 223 g of
C.sub.3F.sub.7OCHFCF.sub.2CH.sub.2OH which corresponded to a yield
of 75%.
[0181] Distillation of the reaction mixture resulted in 171 g of
product (bp 54.degree. C./23 mbar) corresponding to an isolated
yield of 57%.
[0182] b. Preparation of C.sub.3F.sub.7OCHFCF.sub.2COONH.sub.4
[0183] A 2 liter glass flask equipped with a thermometer, reflux
condenser, dropping funnel and stirrer was used. 674 g water, 136 g
KMnO4, and 38 g NaOH are placed in the flask. 169 g
C.sub.3F.sub.7OCHFCF.sub.2CH.sub.2OH were added to the well stirred
mixture via the dropping funnel. The temperature is held below
50.degree. C. Residual permanganate was destroyed by addition of a
small amount of methanol. The resulting slurry was filtered to
remove the MnO.sub.2. After washing the filter cake with water, the
combined filtrate was transferred to a distillation apparatus and
acidified with 65 g of sulfuric acid. 100 g methanol was added and
a flash distillation was started. The distillate formed two layers.
The lower layer was separated and the upper layer returned to the
distillation pot. In total 182 g lower layer were collected.
Fractionation of the crude ester resulted in 137 g of
C.sub.3F.sub.7OCHFCF.sub.2COOCH.sub.3 with a boiling point of
55-56.degree. C./52 mbar. This corresponds to a yield of 77%.
[0184] The ester was converted to the ammonium salt by
saponification with aqueous ammonia and subsequent removal of
methanol by distillation.
Preparation of Compound 11:
CF.sub.3O(CF.sub.2).sub.3OCHFCF.sub.2COONH.sub.4
[0185] a. Preparation of
CF.sub.3O(CF.sub.2).sub.3OCHFCF.sub.2CH.sub.2OH
[0186] Using equipment similar to the described above, 255 g of
perfluoromethoxypropyl vinyl ether and 730 g methanol were
converted with Rongalit and t-butylhydroperoxide as radical source.
Reaction temperature started at 47.degree. C. and reached
64.degree. C. at the end. Work up by distillation yielded 166 g of
pure CF.sub.3O(CF.sub.2).sub.3OCHFCF.sub.2CH.sub.2OH with a boiling
point of 60-61.degree. C./20 mbar. This corresponds to a yield of
59%.
[0187] b. Preparation of
CF.sub.3O(CF.sub.2).sub.3OCHFCF.sub.2COONH.sub.4
[0188] A 2 liter glass flask equipped with a thermometer, reflux
condenser, dropping funnel and stirrer was used. 159 g of
CF.sub.3O(CF.sub.2).sub.3OCHFCF.sub.2CH.sub.2OH, 520 g water, and
100 g sulfuric acid were added to the flask. 190 g KMnO4 were added
manually to the liquid over a period of 2 hours while stirring. The
reaction temperature increased to 95.degree. C. over time. After a
post reaction time of two hours, an aqueous solution of sodium
bisulfite was added until a clear solution was formed. 100 g of
methanol and in total 400 g of 50% aqueous sulphuric acid were
added. Flash distillation of the reaction mixture resulted in a two
phase distillate. Fractionation of the lower phase (120 g) gave
85.5 g of CF.sub.3O(CF.sub.2).sub.3OCHFCF.sub.2COOCH.sub.3 (bp
34-35.degree. C./6 mbar; yield 50%).
[0189] The ester was converted to the ammonium salt by
saponification with aqueous ammonia and subsequent removal of
methanol by distillation.
Preparation of Compound 6
[0190] CH.sub.3--O--CF.sub.2--CF.sub.2--COOCH.sub.3 was fluorinated
as described in WO 01/46116; the acid fluoride
CF.sub.3--O--CF.sub.2--CF.sub.2--COF was then converted into the
methylester. The distilled ester was converted into the
ammonia-salt as described above.
Preparation of Compound 14:
CF.sub.3--CFH--O--(CF.sub.2).sub.5COONH.sub.4
[0191] A sample of diacid fluoride,
FCOCF(CF.sub.3)--O--(CF.sub.2).sub.5COF (500 g, 1.1 mol) prepared
from the hexafluoropropylene oxide (HFPO) coupling of
perfluoroadipoyl fluoride as described in U.S. Publ. No.
2004/0116742 and was added over 2 hours to a stirred slurry of
sodium carbonate (500 g, 4.7 mol) in 500 g of diglyme at 85.degree.
C. to make the disalt. The reaction liberated CO.sub.2 gas.
Distilled water (25 g, 1.4 mol) was added at 85.degree. C. The
mixture was heated up to 168.degree. C. with CO.sub.2 off-gassing
and held for 30 minutes. Reaction was cooled down and sulphuric
acid (350 g, 3.6 mol) in 1100 g of water was added to make the
reaction mixture acidic. Bottom phase was washed with 400 g of 50%
sulfuric acid and vacuum distilled to give
CF.sub.3--CFH--O--(CF.sub.2).sub.5COOH 426 g, 1.0 mol for a 95%
yield having a boiling point of 132-135.degree. C./15 mm. This was
followed by the addition of 46 g NaOH in 63 g of water. Dried salts
in vacuum oven at 112.degree. C./15 mm Hg to give 386 g of slight
yellow sticky solids. To the salt was added sulphuric acid and the
lower fluorochemical phase was vacuum distilled. The previous
process was repeated two more times to yield a colorless acid. The
surfactant CF.sub.3--CFH--O--(CF.sub.2).sub.5COONH.sub.4 having a
melting point of 159-165.degree. C. was made quantitatively from
the reaction of 200 g of acid reacted with excess ammonium
hydroxide and dried.
Preparation of Compound 15:
CF.sub.3--CFH--O(CF.sub.2).sub.3COONH.sub.4
[0192] A sample of diacid fluoride,
FCOCF(CF.sub.3)--O--(CF.sub.2).sub.3COF (503 g, 1.4 mol) prepared
from the HFPO coupling of perfluorosuccinyl fluoride as described
in U.S. Publ. No. U.S. Publ. 2004/0116742 and was added over 2
hours to a stirred slurry of sodium carbonate (387 g, 3.7 mol) in
650 g of diglyme at 78.degree. C. to make the disalt. The reaction
liberated CO.sub.2 gas. Distilled water (35 g, 1.9 mol) was added
at 85.degree. C. The mixture was heated up to 165.degree. C. with
CO.sub.2 off-gassing and held for 30 minutes. Reaction was cooled
down and sulphuric acid (250 g, 2.6 mol) in 1250 g of water was
added to make the reaction mixture acidic. To the bottom phase was
added 60 g NaOH in 60 g of water. Dried the salt in vacuum oven at
112.degree. C./15 mm and recovered 450 g. To the salt was added 300
g of 50% sulphuric acid and the lower fluorochemical phase was
washed once with 200 g of 50% sulphuric acid. Vacuum distillation
gave CF.sub.3--CFH--O--(CF.sub.2).sub.3COOH (400 g, 1.3 mol) for a
95% yield having a boiling point of 111.degree. C./15 mm Hg. The
acid was treated with caustic followed by sulphuric acid and vacuum
distilled. This was repeated a second time to yield a colorless
acid. The surfactant
CF.sub.3--CFH--O--(CF.sub.2).sub.3COO--NH.sub.4 having a melting
point of 64-68.degree. C. was made quantitatively from the reaction
of 208 g of acid reacted with excess ammonium hydroxide and
dried.
Preparation of Compound C-3:
[0193] Conversion of
CF.sub.3CF.sub.2CF.sub.2OCF(CF.sub.3)CF.sub.2OCF.dbd.CF.sub.2 to
CF.sub.3CF.sub.2CF.sub.2OCF(CF.sub.3)CF.sub.2OCF.sub.2COOCH.sub.3
(bp 91-92.degree. C. at 133 mbar) was carried out as described in
U.S. Pat. No. 4,987,254. The ester was reacted with aqueous ammonia
and methanol was removed by distillation resulting in
CF.sub.3CF.sub.2CF.sub.2OCF(CF.sub.3)CF.sub.2OCF.sub.2COONH.sub.4.
All structures were confirmed by F-NMR spectra. Due to an isomer
content in the vinyl ether, an isomer with the structure
CF.sub.3CF.sub.2CF.sub.2OCF.sub.2CF(CF.sub.3)OCF.sub.2COOX
(X.dbd.CH.sub.3, NH.sub.4) was found.
Preparation of Compound 16:
C.sub.3F.sub.7--O--C.sub.2HF.sub.3--O--CH.sub.2--COONH.sub.4
[0194] A mixture of 320 ml Tetrahydrofurane, 40 g Hydroxy acetic
methylester and 188 g PPVE is cooled to 0.degree. C., 27 g
KOH-powder are added in small portions--during the addition of KOH,
the reaction mixture heats up to 60.degree. C. After the addition
of KOH, the whole reaction mixture is agitated for 6 h at
25.degree. C. The precipitated salt is separated by filtration,
dissolved in 300 ml water and then treated with 57 g
H.sub.2SO.sub.4 (conc). The resulting mixture separates in two
layers; the lower phase is
C.sub.3F.sub.7--O--C.sub.2HF.sub.3--O--CH.sub.2--COOH, 86 g (56%).
The distilled acid (bp. 125.degree. C., 20 mbar) is neutralized
with 25% aqueous ammonia solution to provide a 30% solution in
water.
[0195] Compounds 2, 3, 4 were prepared from the corresponding
carboxylic acids (purchased from Anles Ltd. St. Petersburg, Russia)
by neutralizing with aqueous ammonia.
[0196] Compounds 7, 8, 10 were prepared from the corresponding
carboxylic acid fluorides (.about.COF) [purchased from Exfluor,
Round Rock, Tex., USA]. The acid fluorides were converted by
addition of methanol to the methylester. The distillated
methylester were saponified with aqueous ammonia at 60-80.degree.
C. and methanol is removed by distillation.
[0197] Compound C-2 was prepared as described in U.S. Pat. No.
6,703,520 (column 7).
Determination of bio-accumulation
[0198] The perfluorinated and partially fluorinated carboxylates
were evaluated for urinary clearance using a pharmacokinetic study
in rats. The goal was to measure the total amount of parent
compound eliminated via urinary output and estimate the rate of
elimination. The study was approved by the IACUC (Institutional
Animal Care and Use Committees) and was performed in 3M Company's
AAALAC (Association for Assessment and Accreditation of Laboratory
Animal Care) accredited facility.
[0199] The study utilized male Sprague Dawley rats, 6 to 8 weeks of
age, and approximately 200 to 250 g body weight at study onset. The
test compounds of table 2 were administered at a dose of 73 micro
Moles per kg body weight in rats (N=3 animals per tested compound).
All test compounds were prepared in sterile deionized water and
given to rats via oral gavage. After test compounds administration,
the rats were housed individually in metabolism cages for urine
collection: 0 to 6 hours, 6 to 24 hours, 24 to 48 hours and 72 to
96 hours. Animals were observed throughout the study for clinical
signs of toxicity. Gross necropsy was performed at the termination
of each study (96 hours post-dose) with sera and liver samples
being retained from each animal.
[0200] The concentration of the parent compound or metabolites
thereof were quantitatively measured via fluorine NMR on each urine
sample for each animal at each time point based on internally added
standards.
[0201] The bioaccumulation data obtained in accordance with the
above test are reported in table 2 below. TABLE-US-00002 TABLE 2 %
Recovery Compound-related T1/2 (h) (96 h) Effects C-1 .about.550 6
Hepatomegaly C-2 29 40 Hepatomegaly C-3 95 5 Hepatomegaly Compound
1 10 73 -- Compound 2 12 96 -- Compound 3 12 100 -- Compound 4 15
50 -- Compound 5 11 97 -- Compound 6 11 100 -- Compound 7 10 100 --
Compound 8 12 82 -- Compound 9 31 42 Hepatomegaly Compound 10 10 99
-- Compound 11 12 84 -- Compound 12 11 95 Compound 13 11 94 --
Compound 14 24 32 Hepatomegaly Compound 15 8 95 -- Compound 16 13*
65* -- No parent compound observed in the urine. T1/2 and %
recovery are based on elimination of the major metabolite -
C.sub.3F.sub.7--O--CHFCOO.sup.-. T.sub.1/2 is the renal half-life
and is the time required for the amount of a particular substance
in a biological system to be reduced to one half of its # value by
biological processes when the rate of removal is approximately
exponential. In these examples the value of T.sub.1/2 is calculated
by exponential least squares curve fitting (y = Ae.sup.Bx and
T.sub.1/2 = 0.693/B) where y represents the concentration of
analyte in urine and x represents time in hours.
[0202] TABLE-US-00003 TABLE 3 2 C-1 C-2 C-3 1 (140 mmol) 3 4 5 6
Polymerization time (min) 101 77 87 74 109 69 82 73 84 Average
Particle Size (nm) 111 118 113 110 129 115 109 122 122 SSG
(g/cm.sup.3) 2.166 2.165 2.149 2.169 2.157 2.165 2.163 2.169 2.175
Solid content (w-%) 9.9 10.0 10.3 10.3 9.7 10.1 10.2 10.0 7.1 7 14
(140 mmol) 8 9 10 11 12 13 (140 mmol) 15 Polymerization time (min)
73 79 72 72 82 82 83 75 78 Average Particle Size (nm) 129 115 113
102 126 108 128 127 105 SSG (g/cm.sup.3) 2.159 2.167 2.165 2.166
2.168 2.167 2.164 2.151 2.154 Solid content (w-%) 10.1 10.0 10.2
10.1 10.2 10.3 10.2 8.1 10.
Recovery from Exhaust Gas
[0203] 1.2 liter of a polytetrafluoroethylene (PTFE) dispersion
with a solid content of 22.3% by weight, a latex particle diameter
(Z-average) of 180 nm according to dynamic light scattering,
containing about 1900 ppm (or 2.3 g) of 2,4,6
trioxa-perfluoro-octanoate
(CF.sub.3--(OCF.sub.2).sub.3--COONH.sub.4), herein called
fluorinated emulsifier, was coagulated by adding 220 ml of water
containing 50 ml of conc. HCl under vigorous stirring. Another 900
ml of water were added after coagulation and the liquid phase was
decantated. The remaining agglomerate was washed again with 900 ml
of water and decantated. GC-analysis of the combined fractions of
washing water showed an emulsifier content of 24 ppm or 1.7% of the
total amount of fluorinated emulsifier present in the raw
dispersion.
[0204] The wet agglomerate containing about 276 g solids and 280 g
water was transferred into a 4 l flask and heated. A slight
nitrogen stream was flushed through the flask in a range of 5 to 15
l/h. The nitrogen stream leaving the flask was conducted through 4
gas wash-bottles in series, each containing a sodium hydroxide
solution (10% by weight). After heating for about one hour the
temperature inside the flask reached 100.degree. C. and the amount
of solution in the first wash bottle increased due to evaporation.
The first wash bottle had to be cooled by ice-water. The
agglomerate was then heated for another 3.5 hours until the product
reached a temperature of 260.degree. C. The drying process was
stopped and the fluorocarboxylic acid content in the wash bottles
was measured (see table 4). The overall recovery of fluorinated
carboxylic acid from off-gas was determined to be higher than 80%.
TABLE-US-00004 TABLE 4 washing washing content of solution solution
fluro- percentage before after drying carboxylic of recovery drying
process emulsifier from off process (ml) (ml) (g) gas (%) First
wash- 70 265 1.59 .about.70 bottle Second wash- 70 135 0.23
.about.10 bottle Third wash- 110 120 0.03 .about.1 bottle Fourth
wash- 170 175 0.01 <1 bottle
[0205] The dissolved fluorinated carboxylic salt could be further
concentrated and recovered from aqueous phase by subjecting the
aqueous liquid to adsorbent particles as disclosed above.
* * * * *