U.S. patent application number 11/457239 was filed with the patent office on 2008-01-17 for aqueous emulsion polymerization process for producing fluoropolymers.
Invention is credited to Klaus Hintzer, Michael Jurgens, Harald Kaspar, Kai H. Lochhaas, Andreas R. Maurer, Werner Schwertfeger, Tilman C. Zipplies.
Application Number | 20080015304 11/457239 |
Document ID | / |
Family ID | 38950065 |
Filed Date | 2008-01-17 |
United States Patent
Application |
20080015304 |
Kind Code |
A1 |
Hintzer; Klaus ; et
al. |
January 17, 2008 |
AQUEOUS EMULSION POLYMERIZATION PROCESS FOR PRODUCING
FLUOROPOLYMERS
Abstract
The present invention provides a method of making a
fluoropolymer comprising polymerizing one or more fluorinated
monomers in an aqueous emulsion polymerization in the presence of a
fluorinated surfactant selected from fluorinated surfactants of
formula (I): [R.sub.fO-L-CO.sub.2.sup.-].sub.iX.sup.i+ (I) wherein
R.sub.f is selected from a partially fluorinated alkyl group, a
fully fluorinated alkyl group, a partially fluorinated alkyl group
that is interrupted with one or more oxygen atoms, and a fully
fluorinated alkyl group that is interrupted with one or more oxygen
atoms; L is selected from a partially fluorinated alkylene group, a
fully fluorinated alkylene group, a partially fluorinated alkylene
group that is interrupted with one or more oxygen atoms, and a
fully fluorinated alkylene group that is interrupted with one or
more oxygen atoms; X.sup.i+ represents a cation having the valence
i; and i is 1, 2, or 3; further wherein at least part of the
fluorinated surfactant is added to the aqueous phase as an aqueous
mixture with at least one fluorinated liquid, and further wherein
when the fluorinated surfactant is a perfluorinated
polyethercarboxylic acid, the fluorinated liquid is not a
perfluoropolyether.
Inventors: |
Hintzer; Klaus; (Kasti,
DE) ; Jurgens; Michael; (Neuoetting, DE) ;
Kaspar; Harald; (Burgkirchen, DE) ; Lochhaas; Kai
H.; (Neuoetting, DE) ; Maurer; Andreas R.;
(Langenneufnach, DE) ; Schwertfeger; Werner;
(Altoetting, DE) ; Zipplies; Tilman C.;
(Burghausen, DE) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Family ID: |
38950065 |
Appl. No.: |
11/457239 |
Filed: |
July 13, 2006 |
Current U.S.
Class: |
524/544 |
Current CPC
Class: |
C08F 14/18 20130101;
C08F 14/18 20130101; C08F 2/24 20130101; C08F 2/24 20130101 |
Class at
Publication: |
524/544 |
International
Class: |
D06M 15/277 20060101
D06M015/277 |
Claims
1. A method of making a fluoropolymer comprising polymerizing one
or more fluorinated monomers in an aqueous emulsion polymerization
in the presence of a fluorinated surfactant selected from
fluorinated surfactants of formula (I):
[R.sub.fO-L-CO.sub.2.sup.-].sub.iX.sup.i+ (I) wherein R.sub.f is
selected from a partially fluorinated alkyl group, a fully
fluorinated alkyl group, a partially fluorinated alkyl group that
is interrupted with one or more oxygen atoms, and a fully
fluorinated alkyl group that is interrupted with one or more oxygen
atoms; L is selected from a partially fluorinated alkylene group, a
fully fluorinated alkylene group, a partially fluorinated alkylene
group that is interrupted with one or more oxygen atoms, and a
fully fluorinated alkylene group that is interrupted with one or
more oxygen atoms; X.sup.i+ represents a cation having the valence
i; and i is 1, 2, or 3, further wherein at least part of the
fluorinated surfactant is added to the aqueous phase as an aqueous
mixture with at least one fluorinated liquid, and further wherein
when the fluorinated surfactant is a perfluorinated
polyethercarboxylic acid, the fluorinated liquid is not a
perfluoropolyether.
2. The method of claim 1 wherein the fluorinated surfactant is
selected from: i) fluorinated surfactants of formula (II):
CF.sub.3--(OCF.sub.2).sub.m--O--CF.sub.2--X (II) wherein m has a
value of from 1 to 6 and X represents a carboxylic acid or salt
thereof; ii) fluorinated surfactants of formula (III):
CF.sub.3--O--(CF2).sub.3-(OCF(CF.sub.3)CF.sub.2).sub.z--O-L-Y (III)
wherein z has a value of 0, 1, 2, or 3; L represents a divalent
linking group selected from --CF(CF.sub.3)--, --CF.sub.2--, and
--CF.sub.2CF.sub.2--, and Y represents a carboxylic acid group or
salt thereof; iii) fluorinated surfactants of formula (IV):
[R.sub.f.sup.1--(O).sub.t--CQH--(CF.sub.2).sub.p--O].sub.n--R-G
(IV) wherein R.sub.f.sup.1 represents a partially or fully
fluorinated aliphatic group optionally interrupted with one or more
oxygen atoms, Q represents F or CF.sub.3, R is an aliphatic or
aromatic hydrocarbon group, G represents a carboxylic or sulfonic
acid or salt thereof, t is 0 or 1, and n is 1, 2, or 3; iv)
fluorinated surfactants of formula (V)
R.sub.f.sup.2--(O).sub.s--CHF--(CF.sub.2).sub.v--X (V) wherein
R.sub.f.sup.2 represents a partially or fully fluorinated aliphatic
group optionally interrupted with one or more oxygen atoms, s is 0
or 1, v is 0 or 1, and X is a carboxylic acid or salt thereof; v)
fluorinated surfactants of formula (VI)
R.sub.f.sup.3--O--CF.sub.2CF.sub.2--X (VI) wherein R.sub.f.sup.3
represents a linear or branched perfluoroalkyl group having 1, 2,
3, or 4 carbon atoms and X represents a carboxylic acid group or
salt thereof.
3. The method of claim 1 wherein the fluorinated liquid is
perfluorinated.
4. The method of claim 1, wherein the fluorinated liquid is
selected from a perfluoroalkane; a perfluorinated N-alkyl
substituted morpholine; (R.sub.f').sub.3N, wherein each R.sub.f' is
independently selected from a fluorinated alkyl group having from 1
to 10 carbon atoms; and combinations thereof.
5. The method of claim 1 wherein the fluorinated liquid is selected
from perfluoropolyethers of formula (VIII):
R.sub.f''--(--OCF.sub.2).sub.x--(OCF.sub.2CF.sub.2).sub.y--(CF(CF.sub.3)--
-CF.sub.2).sub.z--(OCF(CF.sub.3)).sub.a-Q (VIII) wherein R.sub.f''
is selected from perfluoroalkyl groups having from 1 to 10 carbon
atoms; Q is selected from R.sub.f'' and
R.sub.f''--(OCF.sub.2).sub.x--(OCF.sub.2CF.sub.2).sub.y--(CF(CF.sub.3)--C-
F.sub.2).sub.z--(OCF(CF.sub.3)).sub.a; each x, y, z, and a is
independently selected from 0 to 10 with the proviso that the sum
of x+y+z+a is at least 1.
6. The method of claim 1 wherein the fluorinated liquid is selected
from fluorinated polyethers of formula (X):
R.sub.f'''--O--CFH--CF.sub.2--O--R (X) wherein R.sub.f''' is
selected from a perfluorinated alkyl group having from 1 to 10
carbon atoms and R is selected from CH.sub.3 and R.sub.f''',
wherein when R is R.sub.f''', it may be the same or different than
the other R.sub.f'''.
7. The method of claim 1 wherein the fluorinated liquid is selected
from fluorinated polyethers of the formula (IX):
R.sub.f''''--[OC.sub.3F.sub.6].sub.n--O--CHFCF.sub.3 (IX) wherein
R.sub.f'''' is selected from a perfluorinated alkyl group having
from 1 to 4 carbon atoms, and n is from 1 to 10.
8. The method of claim 1 wherein the fluorinated liquid has a
boiling point of at least 100.degree. C.
9. The method of claim 1 wherein the amount of fluorinated
surfactant not more than 1.0% by weight based on the weight of the
aqueous dispersion.
10. The method of claim 1 wherein the aqueous phase further
comprises a second fluorinated surfactant corresponds to the
following general formula (XI): Y--R.sub.F-Z-M (XI) wherein Y
represents hydrogen, Cl or F; R.sub.F represents a linear or
branched perfluorinated alkylene having 4 to 10 carbon atoms; Z
represents COO-- or SO.sub.3-- and M represents a monovalent
cation.
11. The method of claim 1 wherein the amount of the fluorinated
liquid in the aqueous mixture is between 0.1 and 70% by weight
relative to the total weight of the aqueous mixture.
12. The method of claim 1 wherein the anion of the fluorinated
surfactant has a molecular weight of not more than 1000 grams per
mole.
13. The method of claim 1 wherein the fluorinated surfactant, when
administered to a rat, has a renal recovery rate of at least 50% of
the administered amount 96 hours after administration and further
wherein the renal half-life is not more than 30 hours.
14. The method of claim 1 wherein each aliphatic portion of the
fluorinated surfactant has not more than three carbon atoms.
15. The method of claim 1 wherein the amount of fluorinated
surfactant is from 1 to 40% by weight based on the weight of the
aqueous mixture.
16. The method of claim 1 wherein the fluorinated surfactant forms
a microemulsion.
17. The method of claim 1 wherein the aqueous mixture comprises
droplets having an average particle size of from 5 to 2000 nm.
18. The method of claim 1 wherein the amount of fluorinated
surfactant is less than 1% by weight based on the weight of the
aqueous dispersion.
19. An aqueous mixture comprising a fluorinated surfactant selected
from: i) fluorinated surfactants of formula (II):
CF.sub.3--(OCF.sub.2).sub.m--O--CF.sub.2--X (II) wherein m has a
value of from 1 to 6 and X represents a carboxylic acid or salt
thereof; ii) fluorinated surfactants of formula (III):
CF.sub.3--O--(CF2).sub.3-(OCF(CF.sub.3)CF.sub.2).sub.z--O-L-Y (III)
wherein z has a value of 0, 1, 2, or 3; L represents a divalent
linking group selected from --CF(CF.sub.3)--, --CF.sub.2--, and
--CF.sub.2CF.sub.2--, and Y represents a carboxylic acid group or
salt thereof; iii) fluorinated surfactants of formula (IV):
[R.sub.f.sup.1--(O).sub.t--CQH--(CF.sub.2).sub.p--O].sub.n--R-G
(IV) wherein R.sub.f.sup.1 represents a partially or fully
fluorinated aliphatic group optionally interrupted with one or more
oxygen atoms, Q represents F or CF.sub.3, R is an aliphatic or
aromatic hydrocarbon group, G represents a carboxylic or sulfonic
acid or salt thereof, t is 0 or 1, and n is 1, 2, or 3; iv)
fluorinated surfactants of formula (V)
R.sub.f.sup.2--(O).sub.s--CHF--(CF.sub.2).sub.v--X (V) wherein
R.sub.f.sup.2 represents a partially or fully fluorinated aliphatic
group optionally interrupted with one or more oxygen atoms, s is 0
or 1, v is 0 or 1, and X is a carboxylic acid or salt thereof; v)
fluorinated surfactants of formula (VI)
R.sub.f.sup.3--O--CF.sub.2CF.sub.2--X (VI) wherein R.sub.f.sup.3
represents a linear or branched perfluoroalkyl group having 1, 2,
3, or 4 carbon atoms and X represents a carboxylic acid group or
salt thereof, the aqueous mixture further comprising at least one
fluorinated liquid.
20. An aqueous mixture comprising a fluorinated surfactant selected
from fluorinated surfactants of formula (I):
[R.sub.fO-L-CO.sub.2.sup.-].sub.iX.sup.i+ (I) wherein R.sub.f is
selected from a partially fluorinated alkyl group, a fully
fluorinated alkyl group, a partially fluorinated alkyl group that
is interrupted with one or more oxygen atoms, and a fully
fluorinated alkyl group that is interrupted with one or more oxygen
atoms; L is selected from a partially fluorinated alkylene group, a
fully fluorinated alkylene group, a partially fluorinated alkylene
group that is interrupted with one or more oxygen atoms, and a
fully fluorinated alkylene group that is interrupted with one or
more oxygen atoms; X.sup.i+ represents a cation having the valence
i; and i is 1, 2, or 3; further comprising at least one fluorinated
liquid, and further wherein when the fluorinated surfactant is a
perfluorinated polyethercarboxylic acid, the fluorinated liquid is
not a perfluoropolyether.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[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.
BACKGROUND
[0002] Commonly known or commercially employed fluoropolymers
include polytetrafluoroethylene (PTFE), copolymers of
tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) (FEP
polymers), copolymers of TFE and perfluoroalkoxy copolymers (PFA
polymers), copolymers of TFE and ethylene (ETFE polymers),
terpolymers of TFE, HFP, and vinylidene fluoride (VDF) (THV
polymers) and polymers of VDF (PVDF polymers). Commercially
employed fluoropolymers also include fluoroelastomers and
thermoplastic fluoropolymers. Fluoropolymers and their applications
are further described, for instance, in "Modern Fluoropolymers",
edited by John Scheirs, John Wiley & Sons Ltd., 1997. The
making of such fluoropolymers generally involves the polymerization
of gaseous monomers, i.e. monomers that under ambient conditions of
temperature and pressure exist as a gas. Several polymerization
methods are known to produce fluoropolymers. Such methods include
suspension polymerization as described in e.g. U.S. Pat. No.
3,855,191, U.S. Pat. No. 4,439,385 and EP 649,863; aqueous emulsion
polymerization as described in e.g. U.S. Pat. No. 3,635,926 and
U.S. Pat. No. 4,262,101; solution polymerization as described in
U.S. Pat. No. 3,642,742, U.S. Pat. No. 4,588,796 and U.S. Pat. No.
5,663,255; polymerization using supercritical CO.sub.2 as described
in JP 46011031 and EP 964,009 and polymerization in the gas phase
as disclosed in U.S. Pat. No. 4,861,845.
[0003] Currently, the most commonly employed polymerization methods
include suspension polymerization and aqueous emulsion
polymerization. Aqueous emulsion polymerization often involves
polymerization in the presence of a fluorinated surfactant, which
is generally used to ensure the stabilization of the polymer
particles formed. Accordingly, the emulsion polymerization process
differs from suspension polymerization in which generally no
surfactant is used and which generally results in substantially
larger polymer particles than are formed in aqueous emulsion
polymerization.
[0004] In aqueous emulsion polymerization, the polymerization
speed, yield of polymer, comonomer incorporation, particle size and
particle number are dependent on each other as well as on the level
of emulsifier content. In order to optimize polymer yield,
polymerization time and particle size, one can modify the pressure
of gaseous monomer(s), the temperature, and the type and amount of
fluorinated surfactant. For example, EP 612,770 describes the use
of high amounts of fluorinated surfactant to increase the
polymerization speed. Increasing the amount of fluorinated
surfactant, however, has the disadvantage of increasing the cost of
polymerization and may also be environmentally undesirable.
[0005] U.S. Pat. No. 4,864,006 describes an aqueous emulsion
polymerization process wherein an aqueous micro-emulsion of a
perfluoropolyether is added to a polymerization reaction. The
micro-emulsion is characterized as a mono-phase solution that is
stable in the long run without providing "dispersion energy". It
thus seems that the micro-emulsion discussed forms upon simple
mixing of the components without the need to apply "dispersion
energy" through the use of special emulsifying equipment.
Accordingly, the type of surfactants that can be used are limited,
as not all surfactants are able to form such a micro-emulsion. The
limitations on the useful surfactants may further complicate the
polymerization process. For example, as shown in the examples of
U.S. Pat. No. 4,864,006, the micro-emulsion of the
perfluoropolyether is formed using a perfluoropolyether that has a
carboxylic acid group as a surfactant. Such surfactants may be
expensive. Further, as shown in the examples of U.S. Pat. No.
4,864,006, the micro-emulsion forms at elevated temperatures.
[0006] EP 969,027 describes a process for making PTFE dispersions.
In this patent application, a micro-emulsion of a
perfluoropolyether obtained through emulsification with a
perfluoropolyether surfactant is used to prepare the PTFE
dispersion. Although small polymer particles are achieved in this
process, it appears that large amounts of surfactant are used. The
use of large amounts of surfactants is disadvantageous in that it
makes the process more costly and may put environmental burdens on
the process.
[0007] U.S. Pat. No. 5,895,799 describes a micro-emulsion
polymerization of TFE to produce very small particle dispersions of
PTFE in water. The polymerization of TFE itself proceeds in a
micro-emulsion of liquid perfluorinated hydrocarbons. This
micro-emulsion is formed by adding the perfluorinated hydrocarbon
liquid and a fluorinated surfactant to water at a temperature and
in proportions that result in a micro-emulsion. As is well known,
micro-emulsions only form when the surfactant is used above its
critical micelle concentration (CMC). See P. Lovell, "Emulsion
Polymerization and Emulsion Polymers", J. Wiley, 1997, pages
700-739. As a result, the process taught in U.S. Pat. No. 5,895,799
will generally require large amounts of surfactant, typically much
higher than the amounts employed in conventional aqueous emulsion
polymerization processes that use surfactants in amounts below the
CMC.
SUMMARY
[0008] The present invention recognizes that it is now desirable to
improve the aqueous emulsion polymerization of fluorinated monomers
to produce fluoropolymers. It is in particular desirable to reduce
the polymerization time, improve the yield of polymer solids
obtained and/or to obtain fluoropolymer dispersions having a small
particle size. It is further desirable to simultaneously use a
surfactant that has a low toxicity and/or shows little or no
bioaccumulation. Further, the surfactant should have good chemical
and thermal stability enabling polymerization over a wide range of
conditions of temperature and pressure.
[0009] In one aspect of the present invention, there is provided a
method of making a fluoropolymer comprising polymerizing one or
more fluorinated monomers in an aqueous emulsion polymerization in
the presence of a fluorinated surfactant selected from fluorinated
surfactants of formula (I):
[R.sub.fO-L-CO.sub.2.sup.-].sub.iX.sup.i+ (I)
wherein R.sub.f is selected from a partially fluorinated alkyl
group, a fully fluorinated alkyl group, a partially fluorinated
alkyl group that is interrupted with one or more oxygen atoms, and
a fully fluorinated alkyl group that is interrupted with one or
more oxygen atoms; L is selected from a partially fluorinated
alkylene group, a fully fluorinated alkylene group, a partially
fluorinated alkylene group that is interrupted with one or more
oxygen atoms, and a fully fluorinated alkylene group that is
interrupted with one or more oxygen atoms; X.sup.i+ represents a
cation having the valence i; and i is 1, 2, or 3; further wherein
at least part of the fluorinated surfactant is added to the aqueous
phase as an aqueous mixture with at least one fluorinated liquid,
and further wherein when the fluorinated surfactant is a
perfluorinated polyethercarboxylic acid, the fluorinated liquid is
not a perfluoropolyether.
[0010] In a further aspect of the present invention, there is
provided a method of making a fluoropolymer comprising polymerizing
one or more fluorinated monomers in an aqueous emulsion
polymerization to give an aqueous dispersion, wherein polymerizing
is in the presence of a fluorinated surfactant selected from:
[0011] i) fluorinated surfactants of formula (II):
CF.sub.3--(OCF.sub.2).sub.m--O--CF.sub.2--X (II)
wherein m has a value of from 1 to 6 and X represents a carboxylic
acid or salt thereof;
[0012] ii) fluorinated surfactants of formula (III):
CF.sub.3--O--(CF2).sub.3-(OCF(CF.sub.3)CF.sub.2).sub.z--O-L-Y
(III)
wherein z has a value of 0, 1, 2, or 3; L represents a divalent
linking group selected from --CF(CF.sub.3)--, --CF.sub.2--, and
--CF.sub.2CF.sub.2--, and Y represents a carboxylic acid group or
salt thereof;
[0013] iii) fluorinated surfactants of formula (IV):
[R.sub.f.sup.1--(O).sub.t--CQH--(CF.sub.2).sub.p--O].sub.n--R-G
(IV)
wherein R.sub.f.sup.1 represents a partially or fully fluorinated
aliphatic group optionally interrupted with one or more oxygen
atoms, Q represents F or CF.sub.3, R is an aliphatic or aromatic
hydrocarbon group, G represents a carboxylic or sulfonic acid or
salt thereof, t is 0 or 1, and n is 1, 2, or 3;
[0014] iv) fluorinated surfactants of formula (V)
R.sub.f.sup.2--(O).sub.s--CHF--(CF.sub.2).sub.v--X (V)
wherein R.sub.f.sup.2 represents a partially or fully fluorinated
aliphatic group optionally interrupted with one or more oxygen
atoms, s is 0 or 1, v is 0 or 1, and X is a carboxylic acid or salt
thereof;
[0015] v) fluorinated surfactants of formula (VI)
R.sub.f.sup.3--O--CF.sub.2CF.sub.2--X (VI)
wherein R.sub.f.sup.3 represents a linear or branched
perfluoroalkyl group having 1, 2, 3, or 4 carbon atoms and X
represents a carboxylic acid group or salt thereof; further wherein
at least part of the fluorinated surfactant is added to the aqueous
phase as an aqueous mixture with at least one fluorinated liquid,
the aqueous mixture comprising droplets having an average droplet
diameter of not more than 2000 nm.
[0016] At least part of the fluorinated surfactant is added to the
aqueous phase as an aqueous mixture with at least one fluorinated
liquid. The fluorinated liquid may be polymerizable or
non-polymerizable.
[0017] In a further aspect, the present invention relates to an
aqueous mixture comprising a fluorinated surfactant selected
from:
[0018] i) fluorinated surfactants of formula (II):
CF.sub.3--(OCF.sub.2).sub.m--O--CF.sub.2--X (II)
wherein m has a value of from 1 to 6 and X represents a carboxylic
acid or salt thereof;
[0019] ii) fluorinated surfactants of formula (III):
CF.sub.3--O--(CF2).sub.3-(OCF(CF.sub.3)CF.sub.2).sub.z--O-L-Y
(III)
wherein z has a value of 0, 1, 2, or 3; L represents a divalent
linking group selected from --CF(CF.sub.3)--, --CF.sub.2--, and
--CF.sub.2CF.sub.2--, and Y represents a carboxylic acid group or
salt thereof;
[0020] iii) fluorinated surfactants of formula (IV):
[R.sub.f.sup.1--(O).sub.t--CQH--(CF.sub.2).sub.p--O].sub.n--R-G
(IV)
wherein R.sub.f.sup.1 represents a partially or fully fluorinated
aliphatic group optionally interrupted with one or more oxygen
atoms, Q represents F or CF.sub.3, R is an aliphatic or aromatic
hydrocarbon group, G represents a carboxylic or sulfonic acid or
salt thereof, t is 0 or 1, and n is 1, 2, or 3;
[0021] iv) fluorinated surfactants of formula (V)
R.sub.f.sup.2--(O).sub.s--CHF--(CF.sub.2).sub.v--X (V)
wherein R.sub.f.sup.2 represents a partially or fully fluorinated
aliphatic group optionally interrupted with one or more oxygen
atoms, s is 0 or 1, v is 0 or 1, and X is a carboxylic acid or salt
thereof;
[0022] v) fluorinated surfactants of formula (VI)
R.sub.f.sup.3--O--CF.sub.2CF.sub.2--X (VI)
wherein R.sub.f.sup.3 represents a linear or branched
perfluoroalkyl group having 1, 2, 3, or 4 carbon atoms and X
represents a carboxylic acid group or salt thereof; the aqueous
mixture further comprising at least one fluorinated liquid and,
wherein the surfactant and the fluorinated liquid form emulsified
droplets, further wherein the droplets have an average droplet
diameter of from 20 nm to 2000 nm.
[0023] In a further aspect, the present invention relates to an
aqueous mixture comprising a fluorinated surfactant selected from
fluorinated surfactants of formula (I):
[R.sub.fO-L-CO.sub.2.sup.-].sub.iX.sup.i+ (I)
wherein R.sub.f is selected from a partially fluorinated alkyl
group, a fully fluorinated alkyl group, a partially fluorinated
alkyl group that is interrupted with one or more oxygen atoms, and
a fully fluorinated alkyl group that is interrupted with one or
more oxygen atoms; L is selected from a partially fluorinated
alkylene group, a fully fluorinated alkylene group, a partially
fluorinated alkylene group that is interrupted with one or more
oxygen atoms, and a fully fluorinated alkylene group that is
interrupted with one or more oxygen atoms; X.sup.i+ represents a
cation having the valence i; and i is 1, 2, or 3; further
comprising at least one fluorinated liquid, and further wherein
when the fluorinated surfactant is a perfluorinated
polyethercarboxylic acid, the fluorinated liquid is not a
perfluoropolyether.
[0024] By the term "liquid" or "fluid" in connection with the
present invention are included compounds that are liquid at a
temperature of 20.degree. C. and a pressure of 1 atm as well as
compounds that are liquid under the polymerization conditions.
[0025] By the term "not miscible with water" is meant a liquid that
forms a separate phase absent surfactant when mixed with water in
the amounts in which liquid is employed in the polymerization
described.
[0026] By the term "non-polymerizable" is meant a compound that,
even though present in a reaction medium, is not incorporated into
a polymer formed in an amount that can be measured. For instance, a
compound that has no olefinic groups may be non-polymerizable in
the presence of a radical polymerization. Some compounds having
olefinic groups may also be non-polymerizable when in the presence
of a radical polymerization of tetrafluoroethylene, despite the
presence of a double bond. For instance, compounds containing
double bonds that are sterically hindered, such as
1,2-(perfluoro-n-butyl)ethylene are known to be non-polymerizable.
See, U.S. Pat. No. 5,182,342.
[0027] In the present application, when the term is used
"interrupted with one or more oxygen atoms", it is meant that one
or more ether groups may be present in the aliphatic group. That
is, for instance, where two oxygen atoms are present, they are
separated by at least one carbon atom, so as to form a di-ether.
Peroxide structures are not contemplated by the term "interrupted
by one or more oxygen atoms".
DETAILED DESCRIPTION
[0028] For the sake of convenience, the term "fluorinated
carboxylic acid" is hereinafter used to indicate a free acid as
well as salts thereof.
[0029] The advantages of the process of the present invention are
conveniently achieved by adding to the aqueous phase of an emulsion
polymerization system at least part of the fluorinated surfactant
selected from formula (I) as an aqueous mixture with a fluorinated
liquid. It has been found that the fluorinated surfactants of
formula (I) eliminate more quickly from a living organism, as
demonstrated by 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 fluoropolymer
dispersions, wherein the surfactants can be recovered from the
dispersions in an easy and convenient way.
[0030] Because of their lower bio-accumulation, the fluorinated
surfactants, salts, and derivatives thereof (such as ester
derivatives) should provide less of an environmental burden where
100% recovery of these surfactants from the dispersions is not
achieved. Further, the process of reducing the amount of these
surfactants in the dispersions should be more beneficial for
operators of the removal processes, wherein the operators may be
exposed, for example accidentally, to fluorinated carboxylic acids,
their salts, or derivatives used in work-up procedures following
the recovery of surfactants from the fluoropolymer dispersions.
[0031] In particular embodiments, fluorinated surfactants that
contain no branched alkyl groups and no branched alkylene groups
exhibit a more favorable bio-accumulation profile. That is, linear
fluorinated surfactants tend to show a shorter renal elimination
half-life and a higher rate of recovery than the corresponding
branched fluorinated surfactants.
[0032] In some embodiments, the fluorinated surfactants 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 surfactants 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, some embodiments include those fluorinated
surfactants 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.
[0033] Generally, the fluorinated surfactant 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 surfactant
(that is, the anion of the carboxylic acid) may have a molecular
weight of not more than 500 g/mol.
[0034] In the above formula (I), L represents a linking group. The
linking group may be an alkylene group, and can be a linear or
branched and may be partially or fully fluorinated. 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.
[0035] 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, the hydrogen atoms 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.
[0036] Particular examples of linking groups L may be selected from
the following:
--(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;
--(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 an ether
oxygen in formula (I).
[0037] The R.sub.f group in formula (I) represents a partially
fluorinated alkyl group, a fully fluorinated alkyl group, a
partially fluorinated alkyl group that is interrupted with one or
more oxygen atoms, and a fully fluorinated alkyl group that is
interrupted with one or more oxygen atoms.
[0038] 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.
[0039] 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--.
[0040] Specific examples of compounds according to formula (I)
include the following:
R.sub.f--O--CHF--COOH
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.3
CF.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--(OCF.sub.2).sub.2--O--CF.sub.2--CF.sub.2--O--CHF--COOH
CF.sub.3--(OCF.sub.2).sub.3--O--CF.sub.2--CF.sub.2--O--CHF--COOH
R.sub.f--O--CHF--CF.sub.2--COOH
CF.sub.3--O--CHF--CF.sub.2--COOH
CF.sub.3--O--CF.sub.2CF.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.2CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--COOH
CF.sub.3--O--CF.sub.2--O--CF.sub.2CF.sub.2--O--CHF--CF.sub.2--COOH
CF.sub.3--(OCF.sub.2).sub.2--O--CF.sub.2CF.sub.2--O--CHF--CF.sub.2--COOH
CF.sub.3--(OCF.sub.2).sub.3--O--CF.sub.2CF.sub.2--O--CHF--CF.sub.2--COOH
R.sub.f--O--CF.sub.2--CHFCOOH
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.2CF.sub.2CF.sub.2--O--CF.sub.2--CHF--COOH
CF.sub.3--O--CF.sub.2--O--CF.sub.2CF.sub.2--O--CF.sub.2--CHF--COOH
CF.sub.3--(OCF.sub.2).sub.2--O--CF.sub.2CF.sub.2--O--CF.sub.2--CHF--COOH
CF.sub.3--(OCF.sub.2).sub.3--O--CF.sub.2CF.sub.2--O--CF.sub.2--CHF--COOH
R.sub.f--O--CF.sub.2--CHF--CF.sub.2COOH
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.2CF.sub.2CF.sub.2--O--CF.sub.2--CHF--CF.sub.2--COOH
CF.sub.3--O--CF.sub.2--O--CF.sub.2CF.sub.2--O--CF.sub.2--CHF--CF.sub.2---
COOH
CF.sub.3--(OCF.sub.2).sub.2--O--CF.sub.2CF.sub.2--O--CF.sub.2--CHF--CF.s-
ub.2--COOH
CF.sub.3--(OCF.sub.2).sub.3--O--CF.sub.2CF.sub.2--O--CF.sub.2--CHF--CF.s-
ub.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
CF.sub.3--O--CHF--CF.sub.2--O--CH.sub.2--COOH
CF.sub.3--O--CF.sub.2CF.sub.2CF.sub.2--O--CHF--CF.sub.2--O--CH.sub.2--CO-
OH
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.2CH.sub.2--COOH
C.sub.3F.sub.7--O--CF.sub.2CF.sub.2--O--CHF--CF.sub.2--OCH.sub.2--COOH
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2-CF.sub.2--O--CHF--CF.sub.2--OCH.su-
b.2--COOH
C.sub.3F.sub.7--O--CF.sub.2--CHF--CF.sub.2--OCH.sub.2--COOH
CF.sub.3--CHF--CF.sub.2--O--CH.sub.2--COOH
C.sub.3F.sub.7--CF.sub.2--CHF--CF.sub.2--OCH.sub.2--COOH
R.sub.f--O--((CF.sub.2).sub.n--O).sub.m--CH.sub.2--COOH n=1, 2, or
3; m=0, 1, 2
CF.sub.3--O--CF.sub.2CF.sub.2--O--CH.sub.2--COOH
CF.sub.3--O--CF.sub.2CF.sub.2CF.sub.2--O--CF.sub.2CF.sub.2--O--CH.sub.2--
-COOH
C.sub.3F.sub.7--O--CF.sub.2CF.sub.2--O--CH.sub.2--COOH
C.sub.3F.sub.7--O--CF.sub.2CF.sub.2--O--CF.sub.2CF.sub.2--OCH.sub.2--COO-
H
C.sub.3F.sub.7--O--CF.sub.2CF.sub.2CF.sub.2--O--CF.sub.2CF.sub.2--OCH.su-
b.2--COOH
C.sub.3F.sub.7--O--CF.sub.2CF.sub.2CF.sub.2--OCH.sub.2--COOH
C.sub.4F.sub.9--O--CH.sub.2--COOH
C.sub.3F.sub.7--O--CH.sub.2--COOH
C.sub.6F.sub.13--OCH.sub.2--COOH
R.sub.f--O--CF.sub.2CF.sub.2--COOH
CF.sub.3--O--CF.sub.2CF.sub.2--COOH
C.sub.2F.sub.5--O--CF.sub.2CF.sub.2--COOH
C.sub.3F.sub.7--O--CF.sub.2CF.sub.2--COOH
C.sub.4F.sub.9--O--CF.sub.2CF.sub.2--COOH
R.sub.f--(OCF.sub.2).sub.u--O--CF.sub.2--COOH where u is 1, 2, or
3
CF.sub.3--(OCF.sub.2).sub.3--O--CF.sub.2--COOH
CF.sub.3--(OCF.sub.2).sub.2--O--CF.sub.2--COOH
CF.sub.3--(OCF.sub.2)--O--CF.sub.2--COOH
R.sub.f--(OCF.sub.2CF.sub.2).sub.k--O--CF.sub.2--COOH with k being
1, 2 or 3
CF.sub.3--(OCF.sub.2CF.sub.2).sub.1--O--CF.sub.2--COOH
C.sub.2F.sub.5--(OCF.sub.2CF.sub.2).sub.1--O--CF.sub.2--COOH
C.sub.3F.sub.7--(OCF.sub.2CF.sub.2).sub.1--O--CF.sub.2--COOH
C.sub.4F.sub.9--(OCF.sub.2CF.sub.2).sub.1--O--CF.sub.2--COOH
C.sub.2F.sub.5--(OCF.sub.2CF.sub.2).sub.2--O--CF.sub.2--COOH
CF.sub.3--(OCF.sub.2CF.sub.2).sub.2--O--CF.sub.2--COOH
C.sub.3F.sub.7--(OCF.sub.2CF.sub.2).sub.2--O--CF.sub.2--COOH
C.sub.4F.sub.9--(OCF.sub.2CF.sub.2).sub.2--O--CF.sub.2--COOH
R.sub.f--O--CF.sub.2--COOH
C.sub.3F.sub.7--O--CF.sub.2--COOH
CF.sub.3--O--CF.sub.2CF.sub.2CF.sub.2--O--CF.sub.2--COOH
CF.sub.3CHF--O--(CF.sub.2).sub.O--COOH with o being an integer of
1, 2, 3, 4, 5 or 6
CF.sub.3 CFH--O--(CF.sub.2).sub.3--COOH
CF.sub.3 CFH--O--(CF.sub.2).sub.5--COOH
CF.sub.3CF.sub.2--O--(CF.sub.2).sub.O--COOH with o being as
above
CF.sub.3 CF.sub.2--O--(CF.sub.2).sub.3--COOH
CF.sub.3 CF.sub.2--O--(CF.sub.2).sub.5--COOH
[0041] Surfactants of formula (II) 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 perfluoropolyethers
typically form as byproducts in the manufacturing of
hexafluoropropylene oxide by direct oxidation of
hexafluoropropylene.
[0042] Surfactants according to formula (III) 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. Accordingly,
these perfluoropolyethers can be obtained in an economically
attractive way as they can be derived from other starting materials
that may be used as needed in the manufacturing of fluoromonomers
and fluoropolymers.
[0043] Examples of compounds according to formula (II) or formula
(III) include:
CF.sub.3--(OCF.sub.2).sub.3--O--CF.sub.2COOH
CF.sub.3--(OCF.sub.2).sub.2--O--CF.sub.2COOH
CF.sub.3--(OCF.sub.2)--O--CF.sub.2COOH
CF.sub.3--O--C.sub.3F.sub.6--O--CF.sub.2COOH
CF.sub.3--O--C.sub.3F.sub.6--O--CF(CF.sub.3)COOH
[0044] The surfactants of formula (IV) can be prepared by a number
of routes including, for instance, reacting, generally in the
presence of a base, (a) a fluorinated olefin of the general
formula:
R.sub.f.sup.1--(O).sub.t--CF.dbd.CF.sub.2
[0045] wherein R.sub.f.sup.1 and t are as defined above
with (b) an organic compound of the formula:
(HO).sub.n--R-G
wherein n is 1, 2 or 3, G and R are as defined above.
[0046] Other synthetic routes include those discussed, for
instance, in co-pending application GB 0523853.0 of Koenigsmann et
al.
[0047] Specific examples of surfactants according to formula (IV)
include:
C.sub.3F.sub.7--O--CHF--CF.sub.2--OC.sub.6H.sub.4COO.sup.-Li.sup.+
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--OC.sub.6H.sub.4-
COO.sup.-Na.sup.+
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--OC.su-
b.6H.sub.4COOH
C.sub.3F.sub.7--O--CF.sub.2--CHF--CF.sub.2--OC.sub.6H.sub.4COO.sup.-NH.s-
ub.4.sup.+
C.sub.3F.sub.7--CF.sub.2--CHF--CF.sub.2--OC.sub.6H.sub.4COO.sup.-NH.sub.-
4.sup.+
C.sub.3F.sub.7--O--CHF--CF.sub.2--OCH.sub.2COO.sup.-Li.sup.+
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--OCH.sub.2COO.su-
p.-Na.sup.+
C.sub.3F.sub.7--O--CF.sub.2--CF.sub.2--CF.sub.2--O--CHF--CF.sub.2--OCH.s-
ub.2COOH
C.sub.3F.sub.7--O--CF.sub.2--CHF--CF.sub.2--OCH.sub.2COO.sup.-NH.sub.4.s-
up.+
C.sub.3F.sub.7--CF.sub.2--CHF--CF.sub.2--OCH.sub.2COO.sup.-NH.sub.4.sup.-
+
CF.sub.3--CH(CF.sub.3)--CF.sub.2--O--CH.sub.2--COOH
C.sub.3F.sub.7--O--C(CF.sub.3)F--CF.sub.2--O--CFH--CF.sub.2--O--CH.sub.2-
--COOH
CF.sub.3--CFH--CF.sub.2--O--C.sub.6H.sub.4--COOH
[0048] Fluorinated surfactants of formula (V) can be derived from a
fluorinated olefin of formula (VII).
R.sub.f.sup.2--(O).sub.s--CF.dbd.CF.sub.2 (VII)
[0049] Fluorinated olefins according to formula (VII) that can be
used to prepare the fluorinated surfactants of formula (V) include
perfluorinated alkyl vinyl compounds, vinyl ethers in particular
perfluorovinyl ethers and allyl ethers, in particular
perfluorinated allyl ethers. Particular examples of fluorinated
olefins include those that are used in the preparation of
fluoropolymers and that are described below.
[0050] According to one embodiment, surfactants according to
formula (V) wherein n is 0 can be prepared by reacting a
fluorinated olefin of formula (VII) 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.sup.2--(O).sub.s--CF.dbd.CF.sub.2+NH.sub.3+H.sub.2O.fwdarw.R.sub-
.f.sup.2--(O).sub.s--CHF--COONH.sub.4+NH.sub.4F
[0051] 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.
[0052] In an alternative embodiment to prepare the fluorinated
surfactants of formula (V) wherein n is 0 can be prepared by
reacting a fluorinated olefin of formula (VII) 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 those 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.
[0053] To prepare fluorinated surfactants of formula (V) wherein n
is 1, a free radical reaction of the fluorinated olefin of formula
(VII) with a hydrocarbon alcohol may be carried out followed by an
oxidation of the resulting reaction product. Suitable hydrocarbon
alcohols that can be used include aliphatic alcohols such as lower
alkanols having 1 to 4 carbon atoms. Specific examples include
methanol, ethanol and propanol. 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 surfactant 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 (VII) 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.
[0054] Specific examples of fluorinated surfactants according to
formula (V) include:
CF.sub.3--O--CF(CF.sub.3)--CF.sub.2--O--CHF--COOH
C.sub.3F.sub.7--O--CHF--COOH
C.sub.3F.sub.7--O--CF(CF.sub.3)--CF.sub.2--O--CHF--COOH
CF.sub.3--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--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--CHF--CF.sub.2--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--CF.sub.2--CF.sub.2--O--CF.sub.2--CHF--CF.sub.2--C-
OOH
[0055] The surfactants according to formula (VI) can be synthesized
starting from the corresponding perfluorinated acid fluorides, the
preparation of which is described e.g. in WO 01/46116. To prepare a
surfactant of formula (VI) in which X is a carboxylic acid, the
corresponding perfluorinated acid fluorides are hydrolyzed with
water. Conversion of the acid to any salt may be accomplished by
neutralization with an appropriate base. Alternatively, the
perfluorinated acid fluoride may be reacted with an alcohol (e.g.
methanol or ethanol) so as to result in the corresponding ester.
This ester can then be distilled for further purification and
finally be saponified to the desired salt.
[0056] Specific examples of surfactants according to formula (VI)
include:
CF.sub.3--O--CF.sub.2CF.sub.2--COOM
CF.sub.3CF.sub.2--O--CF.sub.2CF.sub.2COOM
CF.sub.3CF.sub.2CF.sub.2--O--CF.sub.2CF.sub.2COOM
(CF.sub.3).sub.2CF--O--CF.sub.2CF.sub.2COOM
(CF.sub.3).sub.3C--O--CF.sub.2CF.sub.2COOM
CF.sub.3--(CF.sub.2).sub.3--O--CF.sub.2CF.sub.2--COOM
wherein M represents H, Na, K or NH.sub.4.
[0057] It is understood that while the description of compounds in
the present application may reference only the acid form or only
the salt form of a certain species, the corresponding acids and
salts, in particular the NH.sub.4.sup.+, potassium, sodium or
lithium salts, can equally be used.
[0058] The fluorinated liquid may, for instance, be selected from
aliphatic and aromatic fluorinated liquids that optionally have
oxygen, sulfur and/or nitrogen atoms. In particular, some
embodiments have up to 2 oxygen, sulfur and/or nitrogen atoms.
[0059] The fluorinated liquid typically will have a boiling point
of at least 30.degree. C., at least 100.degree. C., or even at
least 150.degree. C., for example between 150.degree. C. and
230.degree. C. Fluorinated liquids with boiling points above
230.degree. C. are also contemplated. For instance, fluorinated
liquids may have boiling points up to 250.degree. C., up to
300.degree. C., even up to 350.degree. C.
[0060] In a particular embodiment the fluorinated liquid is capable
of participating in the free radical polymerization reaction such
that the fluorinated liquid is incorporated into the fluoropolymer
structure produced. That is, in some embodiments, the fluorinated
liquid is polymerizable. A polymerizable fluorinated liquid may, in
some embodiments, have the advantage that little if any residual of
the fluorinated liquid will remain in the aqueous dispersion.
Examples of fluorinated liquids capable of participating in the
polymerization (i.e., polymerizable) include, in particular, liquid
monomers such as, for instance, liquid fluorinated monomers.
Examples of liquid fluorinated monomers that can be used include
liquid perfluorovinyl ethers such as perfluoro-2-propoxypropylvinyl
ether, perfluoro-3-methoxy-n-propylvinyl ether and
CF.sub.3--(CF.sub.2).sub.2--O--CF(CF.sub.3)--CF.sub.2--O--CF(CF-
.sub.3)--CF.sub.2--O--CF.dbd.CF.sub.2 (PPVE-3).
[0061] Suitable fluorinated liquids include those selected from
perfluoroalkanes and (R.sub.f').sub.3N, wherein each R.sub.f' is
independently selected from a fluorinated alkyl group having from 1
to 10 carbon atoms.
[0062] In other embodiments, the fluorinated liquid may be selected
from perfluoropolyethers of formula (VIII):
R.sub.f''--(OCF.sub.2).sub.x--(OCF.sub.2CF.sub.2).sub.y--(CF(CF.sub.3)---
CF.sub.2).sub.z--(OCF(CF.sub.3)).sub.a-Q (VIII)
In formula (VIII), R.sub.f'' is selected from perfluoroalkyl groups
having from 1 to 10 carbon atoms; Q is selected from R.sub.f'' and
R.sub.f''--(OCF.sub.2).sub.x--(OCF.sub.2CF.sub.2).sub.y--(CF(CF.sub.3)--C-
F.sub.2).sub.z--(OCF(CF.sub.3)).sub.a; each x, y, z, and a is
independently selected from 0 to 10, with the proviso that the sum
of x+y+z+a is at least 1.
[0063] In yet further embodiments, the fluorinated liquid may be a
partially fluorinated liquid. It is preferred, however, that a
partially fluorinated liquid does not act as a chain transfer agent
in the aqueous phase. Chain transfer agents are non-radical species
that react with a radical species. This may involve, for instance,
a chain transfer agent reacting with an actively polymerizing
chain. The result of this reaction is at least one different
radical species. After this happens, the polymerizing chain is
terminated. A new chain may or may not start, depending on the
reactivity of the new radical species. In many cases, the result is
a diminution of the molecular weight of the resulting polymer
compared with a polymer prepared under the same conditions except
that the chain transfer agent is not present. This diminution of
molecular weight often takes place without a change in the overall
rate of conversion of monomer to polymer. Therefore, it is possible
to determine whether a fluorinated liquid is acting as a chain
transfer agent in the aqueous phase by observing the molecular
weight of the resulting polymer with and without the fluorinated
liquid. If the molecular weight is significantly decreased with the
addition of the fluorinated liquid (e.g., by 10% or more, by 20% or
more, or even by 30% or more), then the fluorinated liquid is
acting as a chain transfer agent in the aqueous phase.
[0064] Particular embodiments of partially fluorinated liquids
include those selected from fluorinated polyethers of the formula
(IX):
R.sub.f''''--[OC.sub.3F.sub.6].sub.n--O--CHFCF.sub.3 (IX)
wherein R.sub.f'''' is selected from a perfluorinated alkyl group
having from 1 to 4 carbon atoms, and n is from 1 to 10.
[0065] Other embodiments of partially fluorinated liquids include
those selected from fluorinated polyethers of formula (X):
R.sub.f'''--O--CFH--CF.sub.2--O--R (X)
In formula (X), R.sub.f''' may be selected from a perfluorinated
alkyl group having from 1 to 10 carbon atoms and R may be selected
from CH.sub.3 and R.sub.f''', wherein when R is R.sub.f''', it may
be the same or different than the other R.sub.f'''.
[0066] In yet other embodiments, fluorinated liquids include
perfluorinated hydrocarbons such as, for instance, perfluorinated
saturated aliphatic compounds such as a perfluorinated alkane; a
perfluorinated aromatic compound such as perfluorinated benzene, or
perfluorinated tetradecahydrophenanthene. Perfluorinated liquids
also include perfluorinated alkyl amines such as a perfluorinated
trialkyl amine. Furthermore, the perfluorinated liquid may be a
perfluorinated cyclic aliphatic, such as decalin; and preferably a
heterocyclic aliphatic compound containing oxygen, nitrogen or
sulfur in the ring, such as perfluorinated N-alkyl substituted
morpholines or perfluoro-2-butyl tetrahydrofuran. Other embodiments
include perfluoropolyethers such as, for instance, those available
under the trade names Galden.TM., Fomblin.TM. (available from
Solvay Solexis); Demnum.TM. SH (available from Daikin); and
Krytox.TM. (available from DuPont).
[0067] Specific examples of perfluorinated hydrocarbons include
perfluoro-2-butyltetrahydrofuran, perfluorodecalin,
perfluoromethyldecalin, perfluoromethyldecalin,
perfluoromethylcyclohexane, perfluoro(1,3-dimethylcyclohexane),
perfluorodimethyldecahydronaphthalene,
perfluoro(tetradecahydrophenanthrene), perfluorotetracosane,
perfluorokerosenes, oligomers of poly(chlorotrifluoroethylene),
perfluoro(trialkylamine) such as perfluoro(tripropylamine),
perfluoro(tributylamine), or perfluoro(tripentylamine), and
octafluorotoluene, hexafluorobenzene, and commercial fluorinated
solvents, such as Fluorinert FC-75, FC-72, FC-84, FC-77, FC-40,
FC-43, FC-70 or FC 5312 all available from 3M Company, Saint Paul,
Minn. The fluorinated alkanes can be linear or branched, with a
carbon atom number between 3 and 20.
[0068] In some embodiments, the polymerization is carried out in
the presence of an aqueous mixture, where the aqueous mixture,
prior to addition to the polymerization medium, is in the form of a
micro-emulsion.
[0069] Micro-emulsions are generally characterized by being
thermodynamically stable and having a particle size of from about 5
to 50 nm. See, for instance, Applied Surfactants, Tadros, Tharwat
F., Chapter 10 (2005). They are obtainable though any technique
known to produce micro-emulsions, such as heating a mixture of
concentrated surfactant solution (e.g., the concentration of
surfactant is greater than the critical micelle concentration for
the surfactant) and a fluorinated liquid until the mixture is
transparent. The mixture is then cooled. This micro-emulsion can
then be added to the polymerization process as described generally
herein. In this embodiment, the fluorinated surfactant-fluorinated
liquid mixture may or may not remain as a micro-emulsion after it
is added to the polymerization reactor.
[0070] In this embodiment, upon addition to the polymerization
reactor, the amount of fluorinated liquid in the aqueous phase of
the emulsion polymerization may be, for instance, not more than 1%
by weight based on the aqueous phase.
[0071] Generally, the amount of fluorinated liquid in such
embodiments will be not more than 0.5% by weight, not more than
0.2% by weight, or even less than 0.1% by weight. Even amounts of
not more than 0.01% by weight have been found to produce
meritorious effects in the aqueous emulsion polymerization.
[0072] The fluorinated surfactant concentration in the aqueous
dispersion may be, for instance, up to 1% by weight, 0.01 to 1% by
weight, or even 0.005% to 0.4% based on the weight of the aqueous
dispersion.
[0073] Part or all of the fluorinated surfactant used in the
aqueous emulsion polymerization may be added as a mixture with
fluorinated liquid. Generally at least 5% by weight, preferably at
least 10% by weight of the total amount of fluorinated surfactant
used will be added in the form of a mixture with the fluorinated
liquid. If only part of the fluorinated surfactant is added under
the form of a mixture with fluorinated liquid, the remainder of the
fluorinated surfactant may be added separately to the aqueous
phase, e.g. prior to the addition of the mixture of fluorinated
surfactant and fluorinated liquid.
[0074] In another embodiment, the aqueous mixture is an emulsion
that contains a polymerizable fluorinated liquid, along with the
fluorinated surfactant. In such embodiments, the amount of
fluorinated liquid in the aqueous mixture is 70% or less by weight
based on the total weight of the aqueous mixture. For instance, 60%
or less, 50% or less, or even 40% or less. The fluorinated liquid
may be present in the aqueous mixture in an amount of 1% or
greater, 5% or greater, 10% or greater, even 20% or greater.
[0075] The fluorinated liquid is mixed with the aqueous solution of
the fluorinated surfactant and is emulsified therein such that
droplets having an average droplet diameter of not more than 2000
nm, preferably from 50 to 1500 nm, more preferably from 100 to 1300
nm are obtained.
[0076] Emulsions containing particles having an average droplet
diameter of from 50 to 500 nm can be obtained by any suitable
emulsifying apparatus such as those available from the company
Microfluidics (Newton, Mass.).
[0077] Emulsions containing particle having an average droplet
diameter of from 500 nm and higher, for instance, from 500 to 2000
nm, can be obtained using an Ultra Turrax.TM. high-shear mixer.
[0078] Aqueous mixtures may be added to an aqueous emulsion
polymerization reaction in any manner that is convenient. For
instance, the entire amount of the aqueous mixture may be added
before the initiation of polymerization, it may be added during
polymerization, or may be added in part before the initiation of
polymerization, with the remainder of the mixture being added
during polymerization.
[0079] The mixture of the fluorinated surfactant and fluorinated
liquid may further be obtained by a predetermined contamination
with the fluorinated liquid of the solid, or liquid fluorinated
surfactant or molded acid or ester derivative of the fluorinated
surfactant. For example, the process of contamination may involve
re-crystallization of the surfactant.
[0080] Still further, a mixture of fluorinated surfactant and
fluorinated liquid can be prepared in the preparation of the
fluorinated surfactant. For example, the corresponding acid of the
fluorinated surfactants according to formulae (II)-(VI) may be
distilled in the presence of the fluorinated liquid. Subsequently
the acid may be converted into its salt form, for example by adding
ammonia if an ammonium salt is desired. The fluorinated liquid may
for example be added to the corresponding acid of the fluorinated
surfactant and the mixture may then be distilled which will result
in the distillate containing a mixture of acid and fluorinated
liquid.
[0081] The aqueous mixture of the fluorinated surfactant and
fluorinated liquid can then be obtained by converting the
contaminated fluorinated surfactants or acid or ester derivatives
to the salts, and adding to water.
[0082] The methods described herein may have aqueous phases that
further comprise a second fluorinated surfactant, which may be any
fluorinated surfactant known for use in aqueous emulsion
polymerization of fluorinated monomers. Particularly, the aqueous
phase may comprise fluorinated surfactants including those
according to formula (XI):
Y--R.sub.f-Z-M (XI)
In formula (XI), Y represents hydrogen, Cl or F; R.sub.f represents
a linear or branched perfluorinated alkylene having 4 to 10 carbon
atoms; Z represents COO-- or SO.sub.3-- and M represents a
monovalent cation such as for example an alkali metal ion or an
ammonium ion. Mixtures of second fluorinated surfactants can also
be used. In one embodiment, the second fluorinated surfactant is an
ammonium or metal salt of perfluorooctanoic acid or
perfluorooctanesulphonic acid. In certain embodiments, when a
second fluorinated surfactant of formula (X) is present, the
fluorinated surfactant may be selected from perfluorinated
mono-ether carboxylic acids and partially fluorinated ether
carboxylic acids (including mono- and poly-ether carboxylic
acids).
[0083] In yet another embodiment, the polymerization itself can be
carried out in a micro-emulsion. That is, when the polymerizing is
carried out in the presence of a fluorinated surfactant and a
fluorinated liquid, the fluorinated surfactant and fluorinated
liquid are in the form of a micro-emulsion.
[0084] The aqueous emulsion polymerization process is generally
conducted under commonly employed conditions. Polymerization
temperatures may range from 0 to 150.degree. C., from 10 to
100.degree. C., or from 30.degree. C. to 80.degree. C. The total
pressure of the headspace in the reactor may be kept at any
pressure, for instance, from 4 to 30 bar, or from 8 to 20 bar.
[0085] The aqueous emulsion polymerization process can be used to
produce any of the known fluoropolymers, i.e. polymers that have a
partially or fully fluorinated backbone. In particular, the aqueous
emulsion polymerization process can be used to produce homo- and
copolymers of gaseous fluorinated olefinic monomers such as
tetrafluoroethylene, vinylidene fluoride and
chlorotrifluoroethylene. Suitable comonomers include fluorinated
monomers such as hexafluoropropene, perfluoro vinyl ethers
including perfluoroalkyl vinyl ethers such as perfluoromethyl vinyl
ether and perfluoro-n-propylvinyl ether and perfluoroalkoxy vinyl
ethers such as those corresponding to formula (XII):
CF.sub.2.dbd.CFO(R.sup.1O).sub.n(R.sup.2O).sub.mR.sup.3 (XII)
wherein R.sup.1 and R.sup.2 are each independently selected from a
linear or branched perfluoroalkylene group having from 2 to 6
carbon atoms, m and n are each independently from 0 to 10, with the
proviso that the sum of n and m is at least 1, and R.sup.3 is a
perfluoroalkyl group of from 1 to 6 carbon atoms. Combinations of
any of the above-named fluorinated monomers are also
contemplated.
[0086] Further particular monomers include, for instance,
CF.sub.2.dbd.CF--O--(CF.sub.2).sub.4--SO.sub.2F (MV4S);
CF.sub.2.dbd.CF--O--(CF.sub.2).sub.5CN (MV5CN);
CF.sub.2.dbd.CFCF.sub.2--O--(CF.sub.2).sub.n--O--CF.sub.3 where n
is 1 to 5 (MA''n''1, for instance, MA31 corresponds to n=3); and
CF.sub.2.dbd.CF--O--(CF.sub.2).sub.n--O--CF.sub.3 where n is 1 to 5
(MV''n''1, for instance, MV31 corresponds to n=3).
[0087] Non-fluorinated monomers that can be used as comonomers
include alpha-olefins, e.g. ethylene and propylene. The process of
the invention can be used to produce fluoroelastomers as well as
fluorothermoplasts.
[0088] The aqueous emulsion polymerization is typically initiated
by an initiator including any of the initiators known for
initiating a free radical polymerization of fluorinated monomers.
Suitable initiators include peroxides and azo compounds and redox
based initiators. Specific examples of peroxide initiators include,
hydrogen peroxide, sodium or barium peroxide, diacylperoxides such
as diacetylperoxide, disuccinoyl peroxide, dipropionylperoxide,
dibutyrylperoxide, diglutaric acid peroxide, and further per-acids
and salts thereof such as e.g. ammonium, sodium or potassium salts.
Examples of per-acids include peracetic acid. Esters of the peracid
can be used as well. Examples of inorganic initiators include for
example ammonium- alkali- or earth alkali salts of persulfates,
permanganic or manganic acid or manganic acids.
[0089] A persulfate initiator, e.g. ammonium persulfate (APS), may
be used alone or may be used in combination with a reducing agent.
Suitable reducing agents include bisulfites such as for example
ammonium bisulfite or sodium metabisulfite, thiosulfates such as
for example ammonium, potassium or sodium thiosulfate, hydrazines,
azodicarboxylates and azodicarboxyldiamide (ADA). Further reducing
agents that may be used include sodium formaldehyde sulfoxylate
(Rongalit.RTM., available from BASF, Germany) or fluoroalkyl
sulfinates. The reducing agent typically reduces the half-life time
of the persulfate initiator. Additionally, a metal salt catalyst
such as for example copper, iron or silver salts may be added.
[0090] The aqueous emulsion polymerization system may further
comprise other materials, such as buffers and, if desired,
complex-formers or chain-transfer agents.
[0091] The achievable solids content of the polymer dispersion is
typically from 5 to 40% without any major coagulum. The resultant
dispersions are highly stable and generally have an number average
particle diameter of not more than 400 nm, typically between 50 and
350 nm average particle sizes can be achieved.
[0092] The fluoropolymer may be isolated from the dispersion by
coagulation if a polymer in solid form is desired. Also, depending
on the requirements of the application in which the fluoropolymer
is to be used, the fluoropolymer may be post-fluorinated so as to
convert any thermally unstable end groups into stable CF.sub.3 end
groups. Generally, when the fluoropolymer is post fluorinated, it
is post fluorinated such that the amount of end groups in the
fluoropolymer other than CF.sub.3 is less than 80 per million
carbon atoms.
[0093] For coating applications, an aqueous dispersion of the
fluoropolymer may be desired and hence the fluoropolymer may not
need to be separated or coagulated from the dispersion. To obtain a
fluoropolymer dispersion for use in coating applications such as,
for example, in the impregnation of fabrics or in the coating of
metal substrates to make for example cookware, further stabilizing
surfactants may be added and/or the level of fluoropolymer solids
may be increased. For example, non-ionic stabilizing surfactants
may be added to the fluoropolymer dispersion. Typically these will
be added to an aqueous fluoropolymer dispersion in an amount of 1
to 12% by weight based on fluoropolymer solids. Examples of
non-ionic surfactants that may be added include:
R.sup.1--O--[CH.sub.2CH.sub.2O].sub.n--[R.sup.2O].sub.m--R.sup.3
(XIII)
wherein R.sup.1 represents an aromatic or aliphatic hydrocarbon
group having at least 8 carbon atoms, R.sup.2 represents an
alkylene having 3 carbon atoms, R.sup.3 represents hydrogen or a
C.sub.1-C.sub.3 alkyl group, n has a value of 0 to 40, m has a
value of 0 to 40 and the sum of n+m being at least 2. It will be
understood that in the above formula (XIII), the units indexed by n
and m may appear as blocks or they may be present in an alternating
or random configuration. Examples of non-ionic surfactants
according to formula (XIII) above include alkylphenol oxy ethylates
such as ethoxylated p-isooctylphenol commercially available under
the brand name TRITON.TM. such as for example TRITON.TM. X 100
wherein the number of ethoxy units is about 10 or TRITON.TM. X 114
(available from Dow Chemical, Midland, Mich.) wherein the number of
ethoxy units is about 7 to 8. Still further examples include those
in which R.sup.1 in the above formula (XII) represents an alkyl
group of 4 to 20 carbon atoms, m is 0 and R.sup.3 is hydrogen. An
example thereof includes isotridecanol ethoxylated with about 8
ethoxy groups and which is commercially available as
GENAPOL.RTM.X080 (available from Clariant GmbH, Germany). Non-ionic
surfactants according to formula (XII) in which the hydrophilic
part comprises a block-copolymer of ethoxy groups and propoxy
groups may be used as well. Such non-ionic surfactants are
commercially available from Clariant GmbH under the trade
designation GENAPOL.RTM. PF 40 and GENAPOL.RTM. PF 80.
[0094] The amount of fluoropolymer solids in the dispersion may be
up-concentrated as needed or desired to an amount between 30 and
70% by weight. Any of the known up-concentration techniques may be
used including ultra-filtration and thermal up-concentration.
[0095] In some embodiments the surfactant may be removed or reduced
from fluoropolymer dispersions described herein. The methods for
removal include those generally known in the art including those
described in U.S. Pat. No. 6,833,403, Bladel, et al.
[0096] Applications for the fluoropolymers and fluoropolymer
dispersions made from the processes described herein include those
commonly known for fluoropolymers. These applications include, for
instance, those described in Fluoroplastics: Vol. 1, Non-Melt
Processible Fluoroplastics, Ebnesajjad, Chapter 17 (2000) and
Fluoroplastics: Vol. 2, Melt Processible Fluoropolymers,
Ebnesajjad, Parts II and III (2003).
[0097] Advantages and embodiments of this invention are further
illustrated by the following examples, but the particular materials
and amounts thereof recited in these examples, as well as other
conditions and details, should not be construed to unduly limit
this invention. All parts and percentages are by weight unless
otherwise indicated.
EXAMPLES
Test Methods:
Particle Size
[0098] The latex particle size determination was conducted by means
of dynamic light scattering with a Malvern Zetasizer 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.
SSG
[0099] Standard specific gravity was measured according ASTM
4895-04
Solid Content
[0100] Determination of solid content was done by subjecting the
latex sample to a temperature up to 250.degree. C. for 30 min.
Hexafluoropropylene (HFP) Content
[0101] The HFP content was measured via FTIR-spectroscopy as
described in U.S. Pat. No. 4,552,925. The absorbances, A, at the
wave-numbers of 980 cm.sup.-1 and 2350 cm.sup.-1 (A.sub.980 and
A.sub.2350 respectively), were measured using a film of 0.05+0.01
mm in thickness with a Nicolet Magna 560 FTIR spectrometer. The HFP
content was calculated according to the following equation:
HFP content (weight percent)=A.sub.980/A.sub.2350*3.2
Example 1
Preparation of Emulsifier
[0102] 800 g of perfluoro-3,5,7,9-tetraoxadecanoic acid
(CF.sub.3--(OCF.sub.2).sub.4--COOH) (hereinafter Compound 1)
available from Anles Trade (Russia) and 1754 g of deionized water
were introduced into a glass vessel equipped with a mechanical
stirrer and a condenser. 150 g of an aqueous ammonia solution (25%
by weight) was added dropwise to the mixture over a period of about
2 hours under stirring. The final clear and colorless solution had
a pH of about 8.
Example 2
Preparation of a Microemulsion
[0103] 392 g of ammonium salt of Example 1 and 8 g of Fluoroinert
FC-70, available from 3M Company, Saint Paul, Minn., was introduced
into a glass vessel equipped with a mechanical stirrer and a reflux
condenser. The resulting dispersion was heated to 83.degree. C.
under mild stirring for about 8 hours and cooled to room
temperature. A perfectly limpid solution containing 2% by weight
(confirmed by gas chromatographic analysis) of the Fluoroinert was
obtained.
Example 3
(Comparative Example)
[0104] The polymerization experiments were performed in a 40 liter
kettle equipped with an impeller agitator and a baffle. The kettle
was charged with 30 liters of deionized water and set to 35.degree.
C. The kettle was evacuated repeatedly and pressurized with
nitrogen to remove oxygen. The agitator speed was set to 165 rpm.
The oxygen-free kettle was charged with 70 mmol of fluorinated
emulsifier from Example 1 and the following materials were added:
1.06 ml of a solution containing 40 mg of copper sulfate
pentahydrate and 1 mg of concentrated sulfuric acid; 15 g of a 25
weight % aqueous ammonia solution and 5.5 g of 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 by pressurizing with TFE. To start the
polymerization, 20 ml of a an aqueous initiator solution containing
140 mg of sodium sulfite followed by 20 ml of a solution containing
340 mg of ammonium peroxodisulfate were pumped into the reactor.
The beginning of the polymerization was indicated by a pressure
drop. During polymerization, the pressure was maintained at 1.5 MPa
by continuously feeding TFE into the kettle. After 3.2 kg of TFE
had been added, the TFE inlet valve was closed and the pressure was
released.
[0105] 1000 ml of this polymer dispersion was coagulated by adding
20 ml of concentrated 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. Polymerization data and product
characteristics are given in table 2.
Example 4
[0106] Example 4 was carried out as in Comparative Example 3,
except that 70 mmol of emulsifier containing 2 weight % of
Fluoroinert FC-70 as described in Example 2 was added to the kettle
instead of the 90 mmol of fluorinated emulsifier described in
Comparative Example 3.
TABLE-US-00001 TABLE 1 Example 3 (Comparative) Example 4
Polymerization time 91 101 (min) Average Particle 110 72 Size (nm)
SSG (g/cm3) 2.171 2.189 Solid Content (wt %) 10.1 10.1 HFP Content
0.28 0.26 (% m/m) pH 9.5 9.6
Determination of Bio-Accumulation
[0107] The fluorinated surfactants 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.
[0108] 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
micromoles 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.
[0109] 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.
[0110] The bioaccumulation data obtained in accordance with the
above test are reported in table 3.
TABLE-US-00002 TABLE 3 % Recovery Compound-related T.sub.1/2 (h)
(96 h) Effects C.sub.7F.sub.15COONH.sub.4 ~550 6 Hepatomegaly
Compound 1 15 50 -- *T.sub.1/2 is the time required for the amount
of a particular substance in a biological system to be reduced by
one half 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.
* * * * *