U.S. patent application number 13/865460 was filed with the patent office on 2013-09-05 for metal-neutralized sulfonated block copolymers.
This patent application is currently assigned to KRATON POLYMERS US LLC. The applicant listed for this patent is KRATON POLYMERS US LLC. Invention is credited to Carl L. Willis.
Application Number | 20130231406 13/865460 |
Document ID | / |
Family ID | 43855356 |
Filed Date | 2013-09-05 |
United States Patent
Application |
20130231406 |
Kind Code |
A1 |
Willis; Carl L. |
September 5, 2013 |
METAL-NEUTRALIZED SULFONATED BLOCK COPOLYMERS
Abstract
The present disclosure relates to a process for neutralizing a
sulfonated block copolymer with a metal compound, to
metal-neutralized block copolymers, and to various articles
comprising the metal-neutralized block copolymers, e.g., in form of
a water vapor permeable membrane which comprises the
metal-neutralized block copolymers. The present disclosure further
relates to a means and a method for storing and stabilizing a polar
component such as a metal compound in a non-polar liquid phase by
immuring the polar component in micelles of the sulfonated block
copolymer in the non-polar liquid phase.
Inventors: |
Willis; Carl L.; (Houston,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KRATON POLYMERS US LLC |
Houston |
TX |
US |
|
|
Assignee: |
KRATON POLYMERS US LLC
Houston
TX
|
Family ID: |
43855356 |
Appl. No.: |
13/865460 |
Filed: |
April 18, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12578210 |
Oct 13, 2009 |
8445631 |
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13865460 |
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Current U.S.
Class: |
521/27 ;
521/25 |
Current CPC
Class: |
Y02P 70/50 20151101;
C08F 8/44 20130101; B01D 61/44 20130101; C08F 297/046 20130101;
C08F 36/08 20130101; B01D 71/82 20130101; C08F 2810/50 20130101;
B01D 61/002 20130101; C08F 8/36 20130101; B01D 71/80 20130101; Y02E
60/50 20130101; B01J 47/12 20130101; C08F 297/00 20130101; H01M
8/102 20130101; C08G 85/004 20130101; C08F 8/04 20130101; C08F 8/04
20130101; C08F 297/046 20130101; C08F 8/36 20130101; C08F 8/04
20130101; C08F 297/046 20130101; C08F 8/44 20130101; C08F 8/36
20130101; C08F 8/04 20130101; C08F 297/046 20130101 |
Class at
Publication: |
521/27 ;
521/25 |
International
Class: |
C08F 36/08 20060101
C08F036/08; B01J 47/12 20060101 B01J047/12 |
Claims
1.-11. (canceled)
12. A neutralized sulfonated block copolymer which is solid in
water comprising at least two polymer end blocks A and at least one
polymer interior block B, wherein a. each A block contains
essentially no sulfonic acid or sulfonate functional groups and
each B block is a polymer block containing from about 10 to about
100 mol-% sulfonic acid or sulfonate functional groups based on the
number of monomer units of the B block; and b. from 80% to 100% of
the sulfonic acid or sulfonate functional groups of the sulfonated
B blocks are neutralized with a metal compound, wherein the metal
compound comprises magnesium, calcium, strontium, barium, aluminum,
tin, lead, titanium, zirconium, vanadium, chromium, molybdenum,
manganese, iron, cobalt, nickel, copper, silver, zinc, cadmium, or
mercury.
13. (canceled)
14. The neutralized block copolymer of claim 12 wherein the metal
compound comprises magnesium, calcium, aluminum, lead, titanium,
copper, or zinc.
15. The neutralized block copolymer of claim 12 wherein the metal
is in an oxidation state of +2, +3 or +4.
16. The neutralized block copolymer of claim 12 which meets one or
both of the following provisions: a. the neutralized block
copolymer has a water uptake value which is equal to or less than
the water uptake value of a corresponding, non-neutralized
sulfonated block copolymer; and/or b. the neutralized block
copolymer has a wet tensile modulus which is equal to or greater
than the wet tensile modulus of the corresponding, non-neutralized
sulfonated block copolymer.
17. The neutralized block copolymer of claim 16 having a water
uptake value of less than 80% the water uptake value of the
corresponding, non-neutralized block copolymer.
18. The neutralized block copolymer of claim 12 having a water
uptake value of less than 50%-wt. of its dry weigh.
19. The neutralized block copolymer of claim 16 having a water
uptake value of at least 0.1%-wt. of its dry weight.
20. The neutralized block copolymer of claim 12 which is in
hydrated form.
21. The hydrated, neutralized block copolymer of claim 20 which
comprises at least 0.1% by weight, based on the dry weight of the
neutralized block copolymer, of water in incorporated form.
22. The hydrated, neutralized block copolymer of claim 20 which has
a water vapor transport rate of at least about 15,000
g/m.sup.2/day/mil.
23. The hydrated, neutralized block copolymer of claim 20 which
meets one or both of the following provisions: a. the hydrated,
neutralized block copolymer has a water transport rate of at least
about 50% of the water transport rate of a hydrated form of a
corresponding, non-neutralized sulfonated block copolymer; b. the
hydrated, neutralized block copolymer has a wet tensile modulus
which is equal to or greater than the wet tensile modulus of the
hydrated form of the corresponding, non-neutralized sulfonated
block copolymer.
24. The hydrated, neutralized block copolymer of claim 20 having a
water transport rate of at least about 75% of the water transport
rate of a hydrated form of a corresponding non-neutralized block
copolymer.
25. An apparatus comprising a membrane which apparatus is selected
from the group consisting of: devices for controlling humidity,
devices for forward electrodialysis, devices for reverse
electrodialysis, devices for pressure retarded osmosis, devices for
forward osmosis, devices for reverse osmosis, devices for
selectively adding water, devices for selectively removing water,
and batteries, wherein the membrane comprises the neutralized block
copolymer defined in claim 12.
26.-28. (canceled)
29. The neutralized block copolymer of claim 12 wherein each B
block contains about 65 to 100 mol-% sulfonic acid or sulfonate
functional groups.
30. The neutralized block copolymer of claim 12 wherein each B
block contains about 10 to 70 mol-% sulfonic acid or sulfonate
functional groups and from 90 to 100% of the functional groups are
neutralized.
31. A neutralized sulfonated block copolymer having a general
configuration A-B-D-B-A, A-D-B-D-A, (A-D-B).sub.n(A),
(A-B-D).sub.n(A), (A-B-D).sub.nX, (A-D-B).sub.nX, or mixtures
thereof, which is solid in water, wherein a. each A block contains
essentially no sulfonic acid or sulfonate functional groups and
each B block is a polymer block containing from about 10 to about
100 mol-% sulfonic acid or sulfonate functional groups based on the
number of monomer units of the B block, n is an integer from 2 to
about 30, X is a coupling agent residue, and each D block is an
impact modifier block having a glass transition temperature less
than 20.degree. C.; and b. from 80% to 100% of the sulfonic acid or
sulfonate functional groups of the sulfonated B blocks are
neutralized with a metal compound, wherein the metal is selected
from the metals of periods 3 through 6 and groups 2 through 14 of
the Periodic Table of the Elements.
32. The neutralized block copolymer of claim 31 wherein each B
block contains about 65 to 100 mol-% sulfonic acid or sulfonate
functional groups.
33. The neutralized block copolymer of claim 31 wherein each B
block contains about 10 to 70 mol-% sulfonic acid or sulfonate
functional groups and from 90 to 100% of the functional groups are
neutralized.
34. The neutralized block copolymer of claim 31 wherein the metal
is selected from magnesium, aluminum, calcium, scandium, titanium,
vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc,
gallium, strontium, zirconium, molybdenum, ruthenium, rhodium,
palladium, silver, cadmium, tin, barium, hafnium, platinum, gold,
mercury and lead.
35. An apparatus comprising a membrane which apparatus is selected
from the group consisting of: devices for controlling humidity,
devices for forward electrodialysis, devices for reverse
electrodialysis, devices for pressure retarded osmosis, devices for
forward osmosis, devices for reverse osmosis, devices for
selectively adding water, devices for selectively removing water,
and batteries, wherein the membrane comprises the neutralized block
copolymer defined in claim 31.
Description
FIELD OF THE INVENTION
[0001] The present disclosure relates to a process for neutralizing
a sulfonated block copolymer with a metal compound, to
metal-neutralized block copolymers, and to various articles
comprising the metal-neutralized block copolymers, e.g., in form of
a water vapor permeable membrane which comprises the
metal-neutralized block copolymers. The present disclosure further
relates to a means and a method for storing and stabilizing a polar
component such as a metal compound in a non-polar liquid phase by
immuring the polar component in micelles of the sulfonated block
copolymer in the non-polar liquid phase.
BACKGROUND OF THE INVENTION
[0002] The preparation of styrenic block copolymers is well known
in the art. Generally, styrenic block copolymers ("SBC") can
comprise internal polymer blocks and terminal end polymer blocks
comprising chemically different monomer types thereby providing
particular desirable properties. As an example, in a more common
form, SBC's may have internal blocks of conjugated diene and
external blocks having aromatic alkenyl arenes. The interaction of
the differing properties of the polymer blocks allow for different
polymer characteristics to be obtained. For example, the elastomer
properties of internal conjugated diene blocks along with the
"harder" aromatic alkenyl arenes external blocks together form
polymers which are useful for an enormous variety of applications.
Such SBC's can be prepared through sequential polymerization and/or
through coupling reactions.
[0003] It is known also that SBC's can be functionalized in order
to further modify their characteristics. An example of this is the
addition of sulfonic acid or sulfonate ester functional groups to
the polymer backbone. One of the first such sulfonated block
copolymers is disclosed, for example, in U.S. Pat. No. 3,577,357 to
Winkler. The resulting block copolymer was characterized as having
the general configuration A-B--(B-A).sub.1-5, wherein each A is a
non-elastomeric sulfonated monovinyl arene polymer block and each B
is a substantially saturated elastomeric alpha-olefin polymer
block, said block copolymer being sulfonated to an extent
sufficient to provide at least 1% by weight of sulfur in the total
polymer and up to one sulfonated constituent for each monovinyl
arene unit. The sulfonated polymers could be used as such, or could
be used in the form of their acid, alkali metal salt, ammonium salt
or amine salt. According to Winkler, a polystyrene-hydrogenated
polyisoprene-polystyrene triblock copolymer was treated with a
sulfonating agent comprising sulfur trioxide/triethyl phosphate in
1,2-dichloroethane. The sulfonated block copolymers were described
as having water absorption characteristics that might be useful in
water purification membranes and the like, but were later found not
to be castable into films (U.S. Pat. No. 5,468,574).
[0004] More recently, US 2007/0021569 to Willis et al., disclosed
the preparation of sulfonated polymer and inter alia illustrated a
sulfonated block copolymer that is solid in water comprising at
least two polymer end blocks and at least one saturated polymer
interior block wherein each end block is a polymer block resistant
to sulfonation and at least one interior block is a saturated
polymer block susceptible to sulfonation, and wherein at least one
interior blocks is sulfonated to the extent of 10 to 100 mol
percent of the sulfonation susceptible monomer in the block. The
sulfonated block copolymers are described as being able to
transport high amounts of water vapor while at the same time having
good dimensional stability and strength in the presence of water,
and as being valuable materials for end use applications which call
for a combination of good wet strength, good water and proton
transport characteristics, good methanol resistance, easy film or
membrane formation, barrier properties, control of flexibility and
elasticity, adjustable hardness, and thermal/oxidative
stability.
[0005] Additionally, WO 2008/089332 to Dado et al., discloses a
process for preparing sulfonated block copolymers illustrating,
e.g., the sulfonation of a precursor block polymer having at least
one end block A and at least one interior block B wherein each A
block is a polymer block resistant to sulfonation and each B block
is a polymer block susceptible to sulfonation wherein said A and B
blocks are substantially free of olefinic unsaturation. The
precursor block polymer was reacted with an acyl sulfate in a
reaction mixture further comprising at least one non-halogenated
aliphatic solvent. According to Dado et al., the process results in
a reaction product which comprised micelles of sulfonated polymer
and/or other polymer aggregates of definable size and
distribution.
[0006] It has also been reported that sulfonated polymers may be
neutralized with a variety of compounds. U.S. Pat. No. 5,239,010 to
Pottick et al., and U.S. Pat. No. 5,516,831 to Balas et al., for
example, indicate that styrene blocks with sulfonic acid functional
groups may be neutralized by reacting the sulfonated block
copolymer with an ionizable metal compound to obtain a metal
salt.
[0007] Additionally, US 2007/0021569 to Willis et al., indicated
the at least partial neutralization of sulfonated block copolymers
with a variety of base materials including, for example, ionizable
metal compounds as well as various amines. It was further proposed
that the sulfonated block copolymer may be modified by hydrogen
bonding interaction with a base material which, while not
sufficiently strong to neutralize the acid centers of the
sulfonated block copolymer, is strong enough to achieve a
significant attraction to the block copolymer via a hydrogen
bonding interaction.
SUMMARY OF THE INVENTION
[0008] The present technology generally relates to a process for
neutralizing a non-neutralized sulfonated block copolymer having at
least one end block A and at least one interior block B wherein
each A block contains essentially no sulfonic acid or sulfonate
ester functional groups and each B block is a polymer block
containing from about 10 to about 100 mol % sulfonic acid or
sulfonate ester functional groups based on the number of
sulfonation susceptible monomer units of the B block. Generally,
the process comprises [0009] providing a solution comprising the
non-neutralized sulfonated block copolymer and an organic solvent,
and [0010] adding at least one metal compound to the solution,
wherein the metal has an atom number of at least 11.
[0011] In particular aspects, the process described herein meets
one or more of the following conditions: [0012] the solution
comprises the dissolved, non-neutralized sulfonated block copolymer
in micellar form, and/or [0013] from about 80% to about 100% of the
sulfonic acid or sulfonate ester functional groups are neutralized,
and/or [0014] the metal compound is added in an amount of from
about 0.8 to about 10 metal equivalents per 1 equivalent of
sulfonic acid or sulfonate ester functional group of the
non-neutralized sulfonated block copolymer, and/or [0015] the
organic solvent is a non-halogenated aliphatic solvent, and/or
[0016] the organic solvent comprises at least a first and a second
aliphatic solvent, and wherein the B block is substantially soluble
in the first solvent and the A block is substantially soluble in
the second solvent, and/or [0017] the metal compound is selected
from the group of organometal compounds, metal hydrides, metal
oxides, metal hydroxides, metal alkoxides, metal carbonates, metal
hydrogencarbonates, and metal carboxylates, and/or [0018] the metal
compound comprises sodium, potassium, cesium, magnesium, calcium,
strontium, barium, aluminum, tin, lead, titanium, zirconium,
vanadium, chromium, molybdenum, manganese, iron, cobalt, nickel,
copper, silver, zinc, cadmium, or mercury, and/or [0019] the metal
of the metal compound has an atom number of at least 12, and/or
[0020] the metal compound comprises magnesium, calcium, aluminum,
lead, titanium, copper, or zinc, and/or [0021] the metal is in an
oxidation state of +2, +3 or +4.
[0022] The technology described herein further generally relates to
a neutralized sulfonated block copolymer which is solid in water
and which comprises at least two polymer end blocks A and at least
one polymer interior block B, wherein [0023] a. each A block
contains essentially no sulfonic acid or sulfonate ester functional
groups and each B block is a polymer block containing from about 10
to about 100 mol % sulfonic acid or sulfonate ester functional
groups based on the number of sulfonation susceptible monomer units
of the B block; and [0024] b. from 80% to 100% of the sulfonic acid
or sulfonate ester functional groups of the sulfonated B blocks are
neutralized with a metal compound, wherein the metal has an atom
number of at least 11.
[0025] In particular aspects, the neutralized sulfonated block
copolymer described herein meets one or more of the following
conditions: [0026] the metal compound comprises sodium, potassium,
cesium, magnesium, calcium, strontium, barium, aluminum, tin, lead,
titanium, zirconium, vanadium, chromium, molybdenum, manganese,
iron, cobalt, nickel, copper, silver, zinc, cadmium, or mercury,
and/or [0027] the metal compound comprises magnesium, calcium,
aluminum, lead, titanium, copper, or zinc, and/or [0028] the metal
is in an oxidation state of +2, +3 or +4, and/or [0029] the
neutralized sulfonated block copolymer has a water uptake value
which is equal to or less than the water uptake value of a
corresponding, non-neutralized sulfonated block copolymer; and/or
[0030] the neutralized sulfonated block copolymer has a wet tensile
modulus which is equal to or greater than the wet tensile modulus
of the corresponding, non-neutralized sulfonated block copolymer,
and/or [0031] the neutralized sulfonated block copolymer has a
water uptake value of less than 80% the water uptake value of the
corresponding, non-neutralized sulfonated block copolymer, and/or
[0032] the neutralized sulfonated block copolymer has a water
uptake value of less than 50%-wt. of its dry weigh, and/or [0033]
the neutralized sulfonated block copolymer has a water uptake value
of at least 0.1%-wt. of its dry weight, and/or [0034] the
neutralized sulfonated block copolymer is in hydrated form.
[0035] The technology described herein also generally relates to a
hydrated, neutralized sulfonated block copolymer which comprises at
least 0.1% by weight, based on the dry weight of the neutralized
block copolymer, of water in incorporated form. In particular
aspects, the hydrated, neutralized sulfonated block copolymer
described herein, meets one or more of the following conditions:
[0036] the hydrated, neutralized sulfonated block copolymer has a
water vapor transport rate of at least about 15,000
g/m.sup.2/day/mil, and/or [0037] the hydrated, neutralized
sulfonated block copolymer has a water transport rate of at least
about 50% of the water transport rate of a hydrated form of a
corresponding, non-neutralized sulfonated block copolymer, and/or
[0038] the hydrated, neutralized sulfonated block copolymer has a
wet tensile modulus which is equal to or greater than the wet
tensile modulus of the hydrated form of the corresponding,
non-neutralized sulfonated block copolymer, and/or [0039] the
hydrated, neutralized sulfonated block copolymer has a water
transport rate of at least about 75% of the water transport rate of
a hydrated form of a corresponding non-neutralized sulfonated block
copolymer.
[0040] The technology described herein further relates to an
apparatus or device which comprises a membrane such as a device for
controlling humidity, a device for forward electrodialysis, a
device for reverse electrodialysis, a device for pressure retarded
osmosis, a device for forward osmosis, a device for reverse
osmosis, a device for selectively adding water, a device for
selectively removing water, and a battery. The respective apparatus
or device, in each case, includes a membrane which comprises the
aforementioned neutralized sulfonated block copolymer.
[0041] Moreover, the technology described herein generally relates
to a means for storing a polar component comprising a non-polar,
liquid phase and a sulfonated block copolymer having at least one
end block A and at least one interior block B wherein each A block
contains essentially no sulfonic acid or sulfonate ester functional
groups and each B block is a polymer block containing from about 10
to about 100 mol % sulfonic acid or sulfonate ester functional
groups based on the number of sulfonation susceptible monomer units
of the B block, in which the non-polar, liquid phase comprises the
aforementioned sulfonated block copolymer in micellar form adapted
to immure the polar component.
[0042] The technology described herein additionally generally
relates to a process for stabilizing or storing a polar component
in a non-polar liquid phase. Generally, the process comprises
[0043] a. providing solution comprising a non-polar, liquid phase
and a sulfonated block copolymer having at least one end block A
and at least one interior block B wherein each A block contains
essentially no sulfonic acid or sulfonate ester functional groups
and each B block is a polymer block containing from about 10 to
about 100 mol % sulfonic acid or sulfonate ester functional groups
based on the number of sulfonation susceptible monomer units of the
B block wherein the solution comprises the sulfonated block
copolymer in micellar form, and [0044] b. adding at least one polar
component to the solution (a) whereby the polar component is
immured in the micelles.
[0045] In particular aspects of the process the polar component is
a metal compound.
DETAILED DESCRIPTION OF THE INVENTION
[0046] A detailed description of embodiments of the present
invention is disclosed herein; however, it is to be understood that
the disclosed embodiments are merely exemplary of the invention and
that the invention may be embodied in various and alternative forms
of the disclosed embodiments. Therefore, specific structural and
functional details which are addressed in describing the
embodiments herein are not to be interpreted as limiting, but
merely as a basis for the claims and as a representative basis for
teaching one skilled in the art to variously employ the present
invention.
[0047] Unless specifically stated otherwise, all technical terms
used herein have the meaning as commonly understood by those
skilled in the art.
[0048] Moreover, unless specifically stated otherwise, the
following expressions as used herein are understood to have the
following meanings.
[0049] The expressions "non-neutralized sulfonated block copolymer"
and "precursor sulfonated block copolyner" as used herein refer to
a sulfonated block copolymer that essentially has not been
neutralized by an amine, metal or other polar compound and contains
sulfonic acid and/or sulfonate ester functionality.
[0050] The expression "neutralized block copolymer" as used herein
refers to a sulfonated block copolymer which has been neutralized
at least partially.
[0051] The expression "engineering thermoplastic resin" as used
herein encompasses the various polymers such as for example
thermoplastic polyester, thermoplastic polyurethane, poly(aryl
ether) and poly(aryl sulfone), polycarbonate, acetal resin,
polyamide, halogenated thermoplastic, nitrile barrier resin,
poly(methyl methacrylate) and cyclic olefin copolymers, and further
defined in U.S. Pat. No. 4,107,131, the disclosure of which is
hereby incorporated by reference.
[0052] The expression "equilibrium" as used herein in the context
of water absorption refers to the state in which the rate of water
absorption by a block copolymer is in balance with the rate of
water loss by the block copolymer. The state of equilibrium can
generally be reached by immersing a sulfonated block copolymer or a
neutralized block copolymer of the present invention in water for a
24 hour period (one day). The equilibrium state may be reached also
in other wet environments, however the period of time to reach
equilibrium may differ.
[0053] The expression "hydrated" block copolymer as used herein
refers to a block copolymer which has absorbed a significant amount
of water.
[0054] The expression "wet state" as used herein refers to the
state at which a block copolymer has reached equilibrium or has
been immersed in water for a period of 24 hours.
[0055] The expression "dry state" as used herein refers to the
state of a block copolymer which has absorbed essentially no or
only insignificant amounts of water. For example, a sulfonated or
neutralized block copolymer which is merely in contact with the
atmosphere will generally remain in the dry state.
[0056] The expression "water uptake value" as used herein refers to
the weight of water which is absorbed by a block copolymer in
equilibrium as compared to the original weight of the dry material,
and is calculated as a percentage. A lower water uptake value
indicates that less water has been absorbed and therefore
corresponds to a better dimensional stability.
[0057] All publications, patent applications, and patents mentioned
herein are incorporated by reference in their entirety. In the
event of conflict, the present specification, including
definitions, is intended to control.
[0058] Further, all ranges disclosed herein are intended to include
any combination of the mentioned upper and lower limits even if the
particular combination and range is not specifically listed.
[0059] According to several embodiments of the present disclosure,
it has been surprisingly found that neutralized sulfonated polymers
may be obtained by directly contacting a micellar solution of the
sulfonated block copolymer with a metal compound. By this process,
a broad variety of metal compounds may be employed for neutralizing
the sulfonated block copolymer and the subsequent formation of
membranes and articles from this neutralized block copolymer.
Furthermore, the process according to several embodiments allows
for an intimate contact of the metal compound and the sulfonated
block copolymer, and yields neutralized block copolymers suited as
membrane materials which exhibit an unexpectedly superior balance
of properties when compared with the properties of the
non-neutralized sulfonated block copolymers. The particular
properties include, but are not limited to: [0060] (1) An
exceptionally high water vapor transport rate; [0061] (2)
Dimensional stability under wet conditions, as evidenced by low
water uptake values and low swelling; [0062] (3) An increased wet
tensile modulus as compared to that of the corresponding
non-neutralized sulfonated block copolymer. [0063] (4) Consistent
tensile strengths in both wet and dry states.
[0064] Accordingly, the metal neutralized sulfonated block
copolymers presented herein are broadly suited for a wide variety
of applications in praxis, and are especially useful for
applications which involve water or which take place in wet
environments.
[0065] In some embodiments, the precursor sulfonated block polymers
which may be neutralized according to embodiments of the present
disclosure include the non-neutralized sulfonated block copolymers
as described in US 2007/021569 to Willis et al., the entire
disclosure of which is incorporated herein by reference. The
precursor sulfonated block polymers, including the non-neutralized
sulfonated block copolymers as described in US 2007/021569, may be
prepared according to the process of WO 2008/089332 to Dado et al.,
the entire disclosure of which is hereby incorporated by
reference.
[0066] The block copolymers needed to prepare the sulfonated block
copolymers of the present invention may be made by a number of
different processes, including anionic polymerization, moderated
anionic polymerization, cationic polymerization, Ziegler-Natta
polymerization, and living chain or stable free radical
polymerization. Anionic polymerization is described below in more
detail, and in the referenced documents. Moderated anionic
polymerization processes for making styrenic block copolymers are
disclosed, for example, in U.S. Pat. No. 6,391,981, U.S. Pat. No.
6,455,651 and U.S. Pat. No. 6,492,469, each of which is
incorporated herein by reference. Cationic polymerization processes
for preparing block copolymers are disclosed, for example, in U.S.
Pat. No. 6,515,083 and U.S. Pat. No. 4,946,899, each of which is
incorporated herein by reference.
[0067] Living Ziegler-Natta polymerization processes that can be
used to make block copolymers were recently reviewed by G. W.
Coates, P. D. Hustad, and S. Reinartz in Angew. Chem. Int. Ed., 41,
2236-2257 (2002); a subsequent publication by H. Zhang and K.
Nomura (J. Am. Chem. Soc., Comm., 2005) describe living
Ziegler-Natta techniques for making styrenic block copolymers
specifically. The extensive work in the field of nitroxide mediated
living radical polymerization chemistry has been reviewed; see C.
J. Hawker, A. W. Bosman, and E. Harth, Chem. Rev., 101(12),
3661-3688 (2001). As outlined in this review, styrenic block
copolymers can be synthesized by living or stable free radical
techniques. Nitroxide mediated polymerization methods are preferred
living chain or stable free radical polymerization processes when
preparing the precursor polymers.
1. POLYMER STRUCTURE
[0068] One aspect of the invention disclosed herein relates to the
polymer structure of the neutralized sulfonated block copolymers.
In one embodiment, the neutralized block copolymers made by the
present invention will have at least two polymer end or outer
blocks A and at least one saturated polymer interior block B
wherein each A block is a polymer block which is resistant to
sulfonation and each B block is a polymer block which is
susceptible to sulfonation.
[0069] Preferred block copolymer structures have the general
configuration A-B-A, (A-B).sub.n(A), (A-B-A).sub.n, (A-B-A).sub.nX,
(A-B).sub.nX, A-B-D-B-A, A-D-B-D-A, (A-D-B).sub.n(A),
(A-B-D).sub.n(A), (A-B-D).sub.nX, (A-D-B).sub.nX or mixtures
thereof, where n is an integer from 2 to about 30, X is coupling
agent residue and A, B and D are as defined hereinafter.
[0070] Most preferred structures are linear structures such as
A-B-A, (A-B).sub.2X, A-B-D-B-A, (A-B-D).sub.2X, A-D-B-D-A, and
(A-D-B).sub.2X and radial structures such as (A-B).sub.nX and
(A-D-B).sub.nX where n is 3 to 6. Such block copolymers are
typically made via anionic polymerization, stable free radical
polymerization, cationic polymerization or Ziegler-Natta
polymerization. Preferably, the block copolymers are made via
anionic polymerization. It will be understood by those skilled in
the art that in any polymerization, the polymer mixture will
include a certain amount of A-B diblock copolymer, in addition to
any linear and/or radial polymers. The respective amounts have not
been found to be detrimental to the practice of the invention.
[0071] The A blocks are one or more segments selected from
polymerized (i) para-substituted styrene monomers, (ii) ethylene,
(iii) alpha olefins of 3 to 18 carbon atoms; (iv) 1,3-cyclodiene
monomers, (v) monomers of conjugated dienes having a vinyl content
less than 35 mol percent prior to hydrogenation, (vi) acrylic
esters, (vii) methacrylic esters, and (viii) mixtures thereof. If
the A segments are polymers of 1,3-cyclodiene or conjugated dienes,
the segments will be hydrogenated subsequent to polymerization of
the block copolymer and before sulfonation of the block
copolymer.
[0072] The para-substituted styrene monomers are selected from
para-methylstyrene, para-ethylstyrene, para-n-propylstyrene,
para-iso-propylstyrene, para-n-butylstyrene, para-sec-butylstyrene,
para-iso-butylstyrene, para-t-butylstyrene, isomers of
para-decylstyrene, isomers of para-dodecylstyrene and mixtures of
the above monomers. Preferred para-substituted styrene monomers are
para-t-butylstyrene and para-methylstyrene, with
para-t-butylstyrene being most preferred. Monomers may be mixtures
of monomers, depending on the particular source. It is desired that
the overall purity of the para-substituted styrene monomers be at
least 90%-wt., preferably at least 95%-wt., and even more
preferably at least 98%-wt. of the desired para-substituted styrene
monomer.
[0073] When the A blocks are polymer segments of ethylene, it may
be useful to polymerize ethylene via a Ziegler-Natta process, as
taught in the references in the review article by G. W. Coates et
al, as cited above, which disclosure is herein incorporated by
reference. It is preferred to make the ethylene blocks using
anionic polymerization techniques as taught in U.S. Pat. No.
3,450,795, which disclosure is herein incorporated by reference.
The block molecular weight for such ethylene blocks will typically
be between about 1,000 and about 60,000.
[0074] When the A blocks are polymers of alpha olefins of 3 to 18
carbon atoms, such polymers are prepared by via a Ziegler-Natta
process, as taught in the references in the above-cited review
article by G. W. Coates et al. Preferably, the alpha-olefins are
propylene, butylene, hexane or octane, with propylene being most
preferred. The block molecular weight for each of such alpha-olefin
blocks typically is between about 1,000 and about 60,000.
[0075] When the A blocks are hydrogenated polymers of
1,3-cyclodiene monomers, such monomers are selected from the group
consisting of 1,3-cyclohexadiene, 1,3-cycloheptadiene and
1,3-cyclooctadiene. Preferably, the cyclodiene monomer is
1,3-cyclohexadiene. Polymerization of such cyclodiene monomers is
disclosed in U.S. Pat. No. 6,699,941, which disclosure is herein
incorporated by reference. It will be necessary to hydrogenate the
A blocks when using cyclodiene monomers since non-hydrogenated
polymerized cyclodiene blocks are susceptible to sulfonation.
Accordingly, after synthesis of the A block with 1,3-cyclodiene
monomers, the block copolymer will be hydrogenated.
[0076] When the A blocks are hydrogenated polymers of conjugated
acyclic dienes having a vinyl content less than 35 mol percent
prior to hydrogenation, it is preferred that the conjugated diene
is 1,3-butadiene. It is necessary that the vinyl content of the
polymer prior to hydrogenation be less than 35 mol percent,
preferably less than 30 mol percent. In certain embodiments, the
vinyl content of the polymer prior to hydrogenation will be less
than 25 mol percent, even more preferably less than 20 mol percent,
and even less than 15 mol percent with one of the more advantageous
vinyl contents of the polymer prior to hydrogenation being less
than 10 mol percent. In this way, the A blocks will have a
crystalline structure, similar to that of polyethylene. Such A
block structures are disclosed in U.S. Pat. No. 3,670,054 and in
U.S. Pat. No. 4,107,236, each of which disclosures is herein
incorporated by reference.
[0077] The A blocks may also be polymer segments of acrylic esters
or methacrylic esters. Such polymer blocks may be made according to
the methods disclosed in U.S. Pat. No. 6,767,976, which disclosure
is herein incorporated by reference. Specific examples of the
methacrylic ester include esters of a primary alcohol and
methacrylic acid, such as methyl methacrylate, ethyl methacrylate,
propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate,
hexyl methacrylate, 2-ethylhexyl methacrylate, dodecyl
methacrylate, lauryl methacrylate, methoxyethyl methacrylate,
dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate,
glycidyl methacrylate, trimethoxysilylpropyl methacrylate,
trifluoromethyl methacrylate, trifluoroethyl methacrylate; esters
of a secondary alcohol and methacrylic acid, such as isopropyl
methacrylate, cyclohexyl methacrylate and isobornyl methacrylate;
and esters of a tertiary alcohol and methacrylic acid, such as
tert-butyl methacrylate. Specific examples of the acrylic ester
include esters of a primary alcohol and acrylic acid, such as
methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate,
isobutyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, dodecyl
acrylate, lauryl acrylate, methoxyethyl acrylate,
dimethylaminoethyl acrylate, diethylaminoethyl acrylate, glycidyl
acrylate, trimethoxysilylpropyl acrylate, trifluoromethyl acrylate,
trifluoroethyl acrylate; esters of a secondary alcohol and acrylic
acid, such as isopropyl acrylate, cyclohexyl acrylate and isobornyl
acrylate; and esters of a tertiary alcohol and acrylic acid, such
as tert-butyl acrylate. If necessary, as raw material or raw
materials, one or more of other anionic polymerizable monomers may
be used together with the (meth)acrylic ester in the present
invention. Examples of the anionic polymerizable monomer that can
be optionally used include methacrylic or acrylic monomers such as
trimethylsilyl methacrylate, N--,N-dimethylmethacrylamide,
N,N-diisopropylmethacrylamide, N,N-diethylmethacrylamide,
N,N-methylethylmethacrylamide, N,N-di-tert-butylmethacrylamide,
trimethylsilyl acrylate, N,N-dimethylacrylamide,
N,N-di-isopropylacrylamide, N,N-methylethylacrylamide and
N,N-di-tert-butylacrylamide. Moreover, there may be used a
multifunctional anionic polymerizable monomer having in the
molecule thereof two or more methacrylic or acrylic structures,
such as methacrylic ester structures or acrylic ester structures
(for example, ethylene glycol diacrylate, ethylene glycol
dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol
dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol
dimethacrylate, trimethylolpropane triacrylate and
trimethylolpropane trimethacrylate).
[0078] In the polymerization processes used to make the acrylic or
methacrylic ester polymer blocks, only one of the monomers, for
example, the (meth)acrylic ester may be used, or two or more
thereof may be used in combination. When two or more of the
monomers are used in combination, any copolymerization form
selected from random, block, tapered block and the like
copolymerization forms may be effected by selecting conditions such
as a combination of the monomers and the timing of adding the
monomers to the polymerization system (for example, simultaneous
addition of two or more monomers, or separate additions at
intervals of a given time).
[0079] The A blocks may also contain up to 15 mol percent of the
vinyl aromatic monomers such as those present in the B blocks which
are addressed in more detail in the following. In some embodiments,
the A blocks may contain up to 10 mol percent, preferably they will
contain only up to 5 mol percent, and particularly preferably only
up to 2 mol percent of the vinyl aromatic monomers as mentioned for
the B blocks. However, in the most preferred embodiments, the A
blocks will contain no vinyl monomers as present in the B blocks.
The sulfonation level in the A blocks may be from 0 up to 15 mol
percent of the total monomers in the A block. It will be understood
by those skilled in the art that suitable ranges include any
combination of the specified mol percents even if the specific
combination and range is not listed herewith.
[0080] The saturated B blocks, in each case, comprises segments of
one or more polymerized vinyl aromatic monomers selected from
unsubstituted styrene monomer, ortho-substituted styrene monomers,
meta-substituted styrene monomers, alpha-methylstyrene monomer,
1,1-diphenylethylene monomer, 1,2-diphenylethylene monomer, and
mixtures thereof. In addition to the monomers and polymers
mentioned above, the B blocks may also comprise a hydrogenated
copolymer of such monomer(s) with a conjugated diene selected from
1,3-butadiene, isoprene and mixtures thereof, having a vinyl
content of between 20 and 80 mol percent. These copolymers with
hydrogenated dienes may be random copolymers, tapered copolymers,
block copolymers or controlled distribution copolymers. In one
preferred embodiment, the B blocks are hydrogenated and comprise a
copolymer of conjugated dienes and the vinyl aromatic monomers
noted in this paragraph. In another preferred embodiment, the B
blocks are unsubstituted styrene monomer blocks which are saturated
by virtue of the nature of the monomer and do not require the added
process step of hydrogenation. The B blocks having a controlled
distribution structure are disclosed in US 2003/0176582, which
disclosure is herein incorporated by reference. US 2003/0176582
also discloses the preparation of sulfonated block copolymers,
albeit not the block copolymer structures of the present invention.
The B blocks comprising a styrene block are described herein. In a
preferred embodiment, the B blocks are made up of unsubstituted
styrene and will not require a separate hydrogenation step.
[0081] In another aspect of the present invention, the block
copolymer includes at least one impact modifier block D having a
glass transition temperature less than 20.degree. C. In one
embodiment, the impact modifier block D comprises a hydrogenated
polymer or copolymer of a conjugated diene selected from isoprene,
1,3-butadiene and mixtures thereof the butadiene portion of the
polymer block having a vinyl content prior to hydrogenation of
between 20 and 80 mol percent and the polymer block having a number
average molecular weight of between 1,000 and 50,000. In another
embodiment, the impact modifier block D comprises an acrylate or
silicone polymer having a number average molecular weight of 1,000
to 50,000. In still another embodiment, the impact modifier block D
block is a polymer block of isobutylene having a number average
molecular weight of 1,000 to 50,000.
[0082] Each A block independently has a number average molecular
weight between about 1,000 and about 60,000 and each B block
independently has a number average molecular weight between about
10,000 and about 300,000. Preferably each A block has a number
average molecular weight of between 2,000 and 50,000, more
preferably between 3,000 and 40,000 and even more preferably
between 3,000 and 30,000. Preferably each B block has a number
average molecular weight of between 15,000 and 250,000, more
preferably between 20,000 and 200,000, and even more preferably
between 30,000 and 100,000. It will be understood by those skilled
in the art that suitable ranges include any combination of the
specified number average molecular weights even if the specific
combination and range is not listed herewith. These molecular
weights are most accurately determined by light scattering
measurements, and are expressed as number average molecular weight.
Preferably, the sulfonated polymers have from about 8 mol percent
to about 80 mol percent, preferably from about 10 to about 60 mol
percent A blocks, more preferably more than 15 mol percent A blocks
and even more preferably from about 20 to about 50 mol percent A
blocks.
[0083] The relative amount of vinyl aromatic monomers which are
unsubstituted styrene monomer, ortho-substituted styrene monomer,
meta-substituted styrene monomer, alpha-methylstyrene monomer,
1,1-diphenylethylene monomer, and 1,2-diphenylethylene monomer in
the sulfonated block copolymer is from about 5 to about 90 mol
percent, preferably from about 5 to about 85 mol percent. In
alternative embodiments, the amount is from about 10 to about 80
mol percent, preferably from about 10 to about 75 mol percent, more
preferably from about 15 to about 75 mol percent, with the most
preferred being from about 25 to about 70 mol percent. It will be
understood by those skilled in the art that suitable ranges include
any combination of the specified mol percents even if the specific
combination is not listed herewith.
[0084] In a preferred embodiment, the mol percent of vinyl aromatic
monomers which are unsubstituted styrene monomer, ortho-substituted
styrene monomer, meta-substituted styrene monomer,
alpha-methylstyrene monomer, 1,1-diphenylethylene monomer, and
1,2-diphenylethylene monomer in each B block is from about 10 to
about 100 mol percent, preferably from about 25 to about 100 mol
percent, more preferably from about 50 to about 100 mol percent,
even more preferably from about 75 to about 100 mol percent and
most preferably 100 mol percent. It will be understood by those
skilled in the art that suitable ranges include any combination of
the specified mol percents even if the specific combination and
range is not listed herewith.
[0085] Typical levels of sulfonation are such that each B block
contains one or more sulfonic functional groups. Preferred levels
of sulfonation are 10 to 100 mol percent based on the mol percent
of vinyl aromatic monomers which are unsubstituted styrene monomer,
ortho-substituted styrene monomer, meta-substituted styrene
monomer, alpha-methylstyrene monomer, 1,1-diphenylethylene monomer,
and 1,2-diphenylethylene monomer in each B block, more preferably
about 20 to 95 mol percent and even more preferably about 30 to 90
mol percent. It will be understood by those skilled in the art that
suitable ranges of sulfonation include any combination of the
specified mol percents even if the specific combination and range
is not listed herewith. The level of sulfonation is determined by
titration of a dry polymer sample, which has been re-dissolved in
tetrahydrofuran with a standardized solution of NaOH in a mixed
alcohol and water solvent.
2. OVERALL ANIONIC PROCESS TO PREPARE POLYMERS
[0086] The anionic polymerization process comprises polymerizing
the suitable monomers in solution with a lithium initiator. The
solvent used as the polymerization vehicle may be any hydrocarbon
that does not react with the living anionic chain end of the
forming polymer, is easily handled in commercial polymerization
units, and offers the appropriate solubility characteristics for
the product polymer. For example, non-polar aliphatic hydrocarbons,
which are generally lacking in ionizable hydrogen atoms make
particularly suitable solvents. Frequently used are cyclic alkanes,
such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane,
all of which are relatively non-polar. Other suitable solvents will
be known to those skilled in the art and can be selected to perform
effectively in a given set of process conditions, with
polymerization temperature being one of the major factors taken
into consideration.
[0087] Starting materials for preparing the block copolymers of the
present invention include the initial monomers noted above. Other
important starting materials for anionic copolymerizations include
one or more polymerization initiators. In the present invention
such include, for example, alkyl lithium compounds such as
s-butyllithium, n-butyllithium, t-butyllithium, amyllithium and the
like and other organo lithium compounds including di-initiators
such as the di-sec-butyl lithium adduct of m-diisopropenyl benzene.
Other such di-initiators are disclosed in U.S. Pat. No. 6,492,469,
the disclosure of which is incorporated herein by reference. Of the
various polymerization initiators, s-butyllithium is preferred. The
initiator can be used in the polymerization mixture (including
monomers and solvent) in an amount calculated on the basis of one
initiator molecule per desired polymer chain. The lithium initiator
process is well known and is described in, for example, U.S. Pat.
No. 4,039,593 and US Re. 27,145, the disclosure of each of which is
incorporated herein by reference.
[0088] Polymerization conditions to prepare the block copolymers of
the present invention are typically similar to those used for
anionic polymerizations in general. The polymerization is
preferably carried out at a temperature of from about -30.degree.
C. to about 150.degree. C., more preferably about 10.degree. C. to
about 100.degree. C., and most preferably, in view of industrial
limitations, from about 30.degree. C. to about 90.degree. C. The
polymerization is carried out in an inert atmosphere, preferably
under nitrogen, and may also be accomplished under pressure within
the range of from about 0.5 to about 10 bars. This copolymerization
generally requires less than about 12 hours, and can be
accomplished in from about 5 minutes to about 5 hours, depending
upon the temperature, the concentration of the monomer components,
and the molecular weight of the polymer that is desired. When two
or more of the monomers are used in combination, any
copolymerization form selected from random, block, tapered block,
controlled distribution block, and the like copolymerization forms
may be utilized.
[0089] It will be understood by those skilled in the art that the
anionic polymerization process may be moderated by the addition of
a Lewis acid, such as an aluminum alkyl, a magnesium alkyl, a zinc
alkyl or combinations thereof. The effects of the added Lewis acid
on the polymerization process are [0090] 1) to lower the viscosity
of the living polymer solution allowing for a process that operates
at higher polymer concentrations and thus uses less solvent, [0091]
2) to enhance the thermal stability of the living polymer chain end
which permits polymerization at higher temperatures and again,
reduces the viscosity of the polymer solution allowing for the use
of less solvent, and [0092] 3) to slow the rate of reaction which
permits polymerization at higher temperatures while using the same
technology for removing the heat of reaction as had been used in
the standard anionic polymerization process.
[0093] The processing benefits of using Lewis acids to moderate
anionic polymerization techniques have been disclosed in U.S. Pat.
No. 6,391,981, U.S. Pat. No. 6,455,651 and U.S. Pat. No. 6,492,469,
the disclosure of each of which is herein incorporated by
reference. Related information is disclosed in U.S. Pat. No.
6,444,767 and U.S. Pat. No. 6,686,423, the disclosure of each of
which is incorporated herein by reference. The polymer made by such
a moderated, anionic polymerization process can have the same
structure as one prepared using the conventional anionic
polymerization process and as such, this process can be useful in
making the polymers of the present invention. For Lewis acid
moderated, anionic polymerization processes, reaction temperatures
between 100.degree. C. and 150.degree. C. are preferred as at these
temperatures it is possible to take advantage of conducting the
reaction at very high polymer concentrations. While a
stoichiometric excess of the Lewis acid may be used, in most
instances there is not sufficient benefit in improved processing to
justify the additional cost of the excess Lewis acid. It is
preferred to use from about 0.1 to about 1 mole of Lewis acid per
mole of living, anionic chain ends to achieve an improvement in
process performance with the moderated, anionic polymerization
technique.
[0094] Preparation of radial (branched) polymers requires a
post-polymerization step called "coupling". In the above radial
formulas n is an integer of from 3 to about 30, preferably from
about 3 to about 15, and more preferably from 3 to 6, and X is the
remnant or residue of a coupling agent. A variety of coupling
agents is known in the art and can be used in preparing the block
copolymers. These include, for example, dihaloalkanes, silicon
halides, siloxanes, multifunctional epoxides, silica compounds,
esters of monohydric alcohols with carboxylic acids, (e.g.
methylbenzoate and dimethyl adipate) and epoxidized oils.
Star-shaped polymers are prepared with polyalkenyl coupling agents
as disclosed in, for example, U.S. Pat. No. 3,985,830, U.S. Pat.
No. 4,391,949 and U.S. Pat. No. 4,444,953; as well as CA 716,645,
the disclosure of each of which is incorporated herein by
reference. Suitable polyalkenyl coupling agents include
divinylbenzene, and preferably m-divinylbenzene. Preferred are
tetra-alkoxysilanes such as tetra-methoxysilane (TMOS) and
tetra-ethoxysilane (TEOS), tri-alkoxysilanes such as
methyltrimethoxysilane (MTMS), aliphatic diesters such as dimethyl
adipate and diethyl adipate, and diglycidyl aromatic epoxy
compounds such as diglycidyl ethers deriving from the reaction of
bis-phenol A and epichlorohydrin.
[0095] Linear polymers may also be prepared by a
post-polymerization "coupling" step. However, unlike radial
polymers, "n" in the above formulas is the integer 2, and X is the
remnant or residue of a coupling agent.
3. PROCESS TO PREPARE HYDROGENATED BLOCK COPOLYMERS
[0096] As noted, in some cases--i.e., (1) when there is a diene in
the B interior blocks, (2) when the A block is a polymer of a
1,3-cyclodiene, (3) when there is an impact modifier block D and
(4) when the A block is a polymer of a conjugated diene having a
vinyl content of less than 35 mol percent--it is necessary to
selectively hydrogenate the block copolymer to remove any ethylenic
unsaturation prior to sulfonation. Hydrogenation generally improves
thermal stability, ultraviolet light stability, oxidative
stability, and, therefore, weatherability of the final polymer, and
reduces the risk of sulfonating the A block or the D block.
[0097] Hydrogenation can be carried out via any of the several
hydrogenation or selective hydrogenation processes known in the
prior art. Such hydrogenation has been accomplished using methods
such as those taught in, for example, U.S. Pat. No. 3,595,942, U.S.
Pat. No. 3,634,549, U.S. Pat. No. 3,670,054, U.S. Pat. No.
3,700,633, and US Re. 27,145, the disclosure of each of which is
incorporated herein by reference. These methods operate to
hydrogenate polymers containing ethylenic unsaturation and are
based upon operation of a suitable catalyst. Such a catalyst, or
catalyst precursor, preferably comprises a Group 8 to 10 metal such
as nickel or cobalt which is combined with a suitable reducing
agent such as an aluminum alkyl or hydride of a metal selected from
Groups 1, 2 and 13 of the Periodic Table of the Elements,
particularly lithium, magnesium or aluminum. This preparation can
be accomplished in a suitable solvent or diluent at a temperature
from about 20.degree. C. to about 80.degree. C. Other catalysts
that are useful include titanium based catalyst systems.
[0098] Hydrogenation can be carried out under such conditions that
at least about 90 percent of the conjugated diene double bonds are
reduced, and between zero and 10 percent of the arene double bonds
are reduced. Preferred ranges are at least about 95 percent of the
conjugated diene double bonds reduced, and more preferably about 98
percent of the conjugated diene double bonds are reduced.
[0099] Once the hydrogenation is complete, it is preferable to
oxidize and extract the catalyst by stirring the polymer solution
with a relatively large amount of aqueous acid (preferably 1 to 30
percent by weight acid), at a volume ratio of about 0.5 parts
aqueous acid to 1 part polymer solution. The nature of the acid is
not critical. Suitable acids include phosphoric acid, sulfuric acid
and organic acids. This stirring is continued at about 50.degree.
C. for from about 30 to about 60 minutes while sparging with a
mixture of oxygen and nitrogen. Care must be exercised in this step
to avoid that an explosive mixture of oxygen and hydrocarbons is
formed.
4. PROCESS TO MAKE SULFONATED POLYMERS
[0100] According to the multiple embodiments disclosed herein, the
above prepared block copolymers are sulfonated to obtain a
sulfonated polymer product that is in solution and in micellar
form. In this micellar form, the sulfonated block copolymer can be
neutralized prior to casting a membrane, and at the same time, the
risk of gelling and/or precipitation of the sulfonated block
copolymer while in solution is reduced.
[0101] Without being bound by any particular theory, it is the
present belief that the micelle structure of the sulfonated block
copolymer can be described as having a core comprising the
sulfonated block or blocks having a substantial amount of spent
sulfonating agent residues which is surrounded by the sulfonation
resistant block or blocks which, in turn, are swollen by an organic
non-halogenated aliphatic solvent. As will be further described in
more detail below, the sulfonated blocks are highly polar due to
the presence of sulfonic acid and/or sulfonate ester functional
groups. Accordingly, such sulfonated blocks are sequestered into a
core, while the outer sulfonation resistant blocks form a shell
which is solvated by a non-halogenated aliphatic solvent. In
addition to forming discrete micelles, there may also be formation
of polymer aggregates. Without being bound by any particular
theory, polymer aggregates can be described as discrete or
non-discrete structures resulting from association of polymer
chains in ways other than the description provided for micelles,
and/or loosely aggregated groups of two or more discrete micelles.
Accordingly, the solvated sulfonated block copolymer in micellar
form may include discrete micelles and/or aggregates of micelles,
with such solution optionally including aggregated polymer chains
having structures other than the micelle structure.
[0102] Micelles can be formed as a result of the sulfonation
process, or alternatively, the block copolymer may arrange in a
micelle structure prior to sulfonation.
[0103] In some embodiments, for the formation of micelles, the
sulfonation processes as described in WO 2008/089332 may be
employed. The methods are useful for preparing sulfonated styrenic
block copolymers as described in US 2007/021569.
[0104] After polymerization, the polymer can be sulfonated using a
sulfonation reagent such as an acyl sulfate in at least one
non-halogenated aliphatic solvent. In some embodiments, the
precursor polymer can be sulfonated after being isolated, washed,
and dried from the reaction mixture resulting from the production
of the precursor polymer. In some other embodiments, the precursor
polymer can be sulfonated without being isolated from the reaction
mixture resulting from the production of the precursor polymer.
a) Solvent
[0105] The organic solvent is preferably a non-halogenated
aliphatic solvent and contains a first non-halogenated aliphatic
solvent which serves to solvate one or more of the sulfonation
resistant blocks or non-sulfonated blocks of the copolymer. The
first non-halogenated aliphatic solvent may include substituted or
unsubstituted cyclic aliphatic hydrocarbons having from about 5 to
10 carbons. Non-limiting examples include cyclohexane,
methylcyclohexane, cyclopentane, cycloheptane, cyclooctane and
mixtures thereof. The most preferable solvents are cyclohexane,
cyclopentane and methylcyclohexane. The first solvent may also be
the same solvent used as the polymerization vehicle for anionic
polymerization of the polymer blocks.
[0106] In some embodiments, the block copolymer may be in micellar
form prior to sulfonation even in the case of using only a first
solvent. The addition of a second non-halogenated aliphatic solvent
to a solution of the precursor polymer in the first non-halogenated
aliphatic solvent can result in or assist the "pre-formation" of
polymer micelles and/or other polymer aggregates. The second
non-halogenated solvent, on the other hand, is preferably chosen
such that it is miscible with the first solvent, but is a poor
solvent for the sulfonation susceptible block of the precursor
polymer in the process temperature range and also does not impede
the sulfonation reaction. In other words, preferably, the
sulfonation susceptible block of the precursor polymer is
substantially insoluble in the second non-halogenated solvent in
the process temperature range. In the case where the sulfonation
susceptible block of the precursor polymer is polystyrene, suitable
solvents which are poor solvents for polystyrene and can be used as
the second non-halogenated solvent include linear and branched
aliphatic hydrocarbons of up to about 12 carbons, for example,
hexane, heptane, octane, 2-ethyl hexane, isooctane, nonane, decane,
paraffinic oils, mixed paraffinic solvents, and the like. One
preferred example of the second non-halogenated aliphatic solvent
is n-heptane.
[0107] The pre-formed polymer micelles and/or other polymer
aggregates allow that the sulfonation of the polymer proceeds
essentially without disabling gelling at considerably higher
concentration than can be achieved without the addition of the
second solvent. In addition, this approach can substantially
improve the utility of more polar acyl sulfates, such as C.sub.3
acyl sulfate (propionyl sulfate), in terms of polymer sulfonation
conversion rate and minimization of by-products. In other words,
this approach may improve the utility of more polar sulfonation
reagents. Such acyl sulfates are further described below.
b) Polymer Concentration
[0108] In accordance with some embodiments, high levels of styrene
sulfonation can be achieved in a manner that is substantially free
of polymer precipitation and free of disabling gelling in the
reaction mixture, the reaction product, or both, by maintaining the
precursor polymer concentration below a limiting concentration of
the precursor polymer, at least during the early stages of
sulfonation. It will be understood by those skilled in the art that
minor amounts of polymers may deposit on surfaces as a result of
localized solvent evaporation in the course of processing in a
mixture that is substantially free of polymer precipitation. For
example, in accordance with some embodiments, a mixture is
considered to be substantially free of polymer precipitation when
no more than 5% of the polymer in the mixture has precipitated.
[0109] The polymer concentration at which the sulfonation can be
conducted depends upon the composition of the starting polymer,
since the limiting concentration below which polymer gelling is
non-disabling or negligible depends upon the polymer composition.
As stated above, the limiting concentration may also be dependent
on other factors such as the identity of the solvent or the solvent
mixture used and the desired degree of sulfonation. Generally, the
polymer concentration falls within the range of from about 1%-wt.
to about 30%-wt., alternatively from about 1%-wt. to about 20%-wt.,
alternatively from about 1%-wt. to about 15%-wt., alternatively
from about 1%-wt. to about 12%-wt., or alternatively from about
1%-wt. to about 10%-wt., based on the total weight of a reaction
mixture that is preferably substantially free of halogenated
solvents. It will be understood by those skilled in the art that
suitable ranges include any combination of the specified mol
percents even if the specific combination and range is not listed
herewith.
[0110] In accordance with some embodiments of the presently
described technology, the initial concentration of the precursor
block polymer or mixture of precursor block polymers should be
maintained below the limiting concentration of the precursor
polymer(s), alternatively in the range of from about 0.1%-wt. to a
concentration that is below the limiting concentration of the
precursor polymer(s), alternatively from about 0.5%-wt. to a
concentration that is below the limiting concentration of the
precursor polymer(s), alternatively from about 1.0%-wt. to a
concentration that is about 0.1%-wt. below the limiting
concentration of the precursor polymer(s), alternatively from about
2.0%-wt. to a concentration that is about 0.1%-wt. below the
limiting concentration of the precursor polymer(s), alternatively
from about 3.0%-wt. to a concentration that is about 0.1%-wt. below
the limiting concentration of the precursor polymer(s),
alternatively from about 5.0%-wt. to a concentration that is about
0.1%-wt. below the limiting concentration of the precursor
polymer(s), based on the total weight of the reaction mixture. It
will be understood by those skilled in the art that suitable ranges
include any combination of the specified mol percents even if the
specific combination and range is not listed herewith.
[0111] At least in some embodiments, maintaining the polymer
concentration below the limiting concentration can result in
reaction mixtures with reduced concentrations of by-product
carboxylic acid relative to the higher concentration conditions
that lead to gelling.
[0112] It will be understood by those skilled in the art, however,
that during the production of the sulfonated polymer in some
embodiments of the present technology, especially in a semi-batch
or continuous production process, the total concentration of the
polymer(s) in the reaction mixture may be above the limiting
concentration of the precursor polymer.
c) Sulfonation Agent
[0113] According to multiple embodiments, acyl sulfate may be used
for sulfonating the polymerized block copolymer. The acyl group
preferably is derived from a C.sub.2 to C.sub.8, alternatively
C.sub.3 to C.sub.8, alternatively C.sub.3 to C.sub.5, linear,
branched, or cyclic carboxylic acid, anhydride, or acid chloride,
or mixtures thereof. Preferably, these compounds do not contain
non-aromatic carbon-carbon double bonds, hydroxyl groups, or any
other functionality that is reactive with acyl sulfate or
decomposes readily under sulfonation reaction conditions. For
example, acyl groups that have aliphatic quaternary carbons in the
alpha-position from the carbonyl functionality (e.g., acyl sulfate
derived from trimethylacetic anhydride) appear to decompose readily
during polymer sulfonation reaction, and preferably should be
avoided in the presently described technology. Also included in the
scope of useful acyl groups for the generation of acyl sulfate in
the present technology are those derived from aromatic carboxylic
acids, anhydrides, and acid chlorides such as benzoic and phthalic
anhydride. More preferably, the acyl group is selected from the
group of acetyl, propionyl, n-butyryl, and isobutyryl. Even more
preferably, the acyl group is isobutyryl. It has been discovered
that isobutyryl sulfate can afford high degrees of polymer
sulfonation and relatively minimal by-product formation.
[0114] The formation of acyl sulfate from a carboxylic anhydride
and sulfuric acid can be represented by the following reaction:
##STR00001##
[0115] Acyl sulfates are subject to slow decomposition during the
course of sulfonation reactions forming alpha-sulfonated carboxylic
acids of the following formula:
##STR00002##
[0116] In one embodiment of the presently described technology, the
acyl sulfate reagent is obtained from a carboxylic anhydride and
sulfuric acid in a reaction that is conducted in a separate
"pre-generation" reaction prior to addition to a solution of
polymer in a non-halogenated aliphatic solvent. The pre-generation
reaction can be conducted with or without a solvent. When a solvent
is used to pre-generate the acyl sulfate, the solvent is preferably
non-halogenated. Alternatively, the acyl sulfate reagent can be
obtained in an in-situ reaction within a solution of the polymer in
a non-halogenated aliphatic solvent. In accordance with this
embodiment of the present technology, the molar ratio of anhydride
to sulfuric acid can be from about 0.8 to about 2, and preferably
from about 1.0 to about 1.4. The sulfuric acid used in this
preferred method preferably has a concentration of about 93% to
about 100% and more preferably has a concentration of about 95% to
about 100%, by weight. It will be understood by those skilled in
the art that oleum may be used as an alternative to sulfuric acid
in an in-situ reaction to generate acyl sulfate, provided that the
oleum strength is sufficiently low so as to avoid or minimize
unintended charring of the reaction mixture.
[0117] In another embodiment of the present technology, the acyl
sulfate reagent can be obtained from a carboxylic anhydride and
oleum in a reaction that is conducted in a separate
"pre-generation" reaction prior to addition to a solution of
polymer in aliphatic solvent, wherein the oleum strength is in the
range of from about 1% to about 60% free sulfur trioxide,
alternatively from about 1% to about 46% free sulfur trioxide,
alternatively from about 10% to about 46% free sulfur trioxide, and
wherein the molar ratio of anhydride to sulfuric acid present in
the oleum is from about 0.9 to about 1.2.
[0118] Additionally, the acyl sulfate reagent can be prepared from
a carboxylic anhydride via reaction with any combination of
sulfuric acid, oleum, or sulfur trioxide. Further, the acyl sulfate
reagent can be prepared from a carboxylic acid via reaction with
chlorosulfonic acid, oleum, sulfur trioxide, or any combination
thereof. Moreover, the acyl sulfate reagent can also be prepared
from a carboxylic acid chloride via reaction with sulfuric acid.
Alternatively, the acyl sulfate may be prepared from any
combination of carboxylic acid, anhydride, and/or acid
chloride.
[0119] The sulfonation of polymer styrenic repeat units with the
acyl sulfate can be represented by the following reaction:
##STR00003##
[0120] The acyl sulfate reagent that may be used relative to the
moles of sulfonation susceptible monomer repeat units present in
the polymer solution in amounts ranging from very low levels for
lightly sulfonated polymer products to high levels for heavily
sulfonated polymer products. The molar amount of the acyl sulfate
can be defined as the theoretical amount of the acyl sulfate that
can be generated from a given method, the amount being dictated by
the limiting reagent in the reaction. The molar ratio of acyl
sulfate to styrene repeat units (i.e., sulfonation susceptible
units) in accordance with some embodiments of the present
technology may range from about 0.1 to about 2.0, alternatively
from about 0.2 to about 1.3, alternatively from about 0.3 to about
1.0.
[0121] In accordance with at least some embodiments of the
presently described technology, the degree of sulfonation of the
vinyl aromatic monomers susceptible to sulfonation in the block
polymers is greater than about 0.4 milliequivalents (meq) sulfonic
acid per gram sulfonated polymer (0.4 meq/g), alternatively greater
than about 0.6 meq sulfonic acid per gram sulfonated polymer (0.6
meq/g), alternatively greater than about 0.8 meq sulfonic acid per
gram sulfonated polymer (0.8 meq/g), alternatively greater than
about 1.0 meq sulfonic acid per gram sulfonated polymer (1.0
meq/g), alternatively greater than about 1.4 meq sulfonic acid per
gram sulfonated polymer (1.4 meq/g). For example, after the
precursor polymers described above are sulfonated in accordance
with the methods of the presently described technology, the typical
levels of sulfonation are where each B block contains one or more
sulfonic functional groups. Preferred levels of sulfonation are
from about 10 to about 100 mol percent, alternatively from about 20
to 95 mol percent, alternatively from about 30 to 90 mol percent,
and alternatively from about 40 to about 70 mol percent, based on
the mol percent of sulfonation susceptible vinyl aromatic monomers
in each B block, which can be, for example, unsubstituted styrene
monomer, ortho-substituted styrene monomer, meta-substituted
styrene monomer, alpha-methylstyrene monomer, 1,1-diphenyl ethylene
monomer, 1,2-diphenyl ethylene monomer, a derivative thereof, or a
mixture thereof. It will be understood by those skilled in the art
that suitable ranges of sulfonation level include any combination
of the specified mol percents even if the specific combination and
range is not listed herewith.
[0122] The level or degree of sulfonation of a sulfonated polymer
can be measured by NMR and/or titration methods as known to people
skilled in the art, and/or a method using two separate titrations
as described in the Examples below and may be appreciated by people
skilled in the art. For example, a resulting solution from the
methods of the present technology can be analyzed by .sup.1H-NMR at
about 60.degree. C. (.+-.20.degree. C.). The percentage styrene
sulfonation can be calculated from the integration of aromatic
signals in the .sup.1H-NMR spectrum. For another example, the
reaction product can be analyzed by two separate titrations (the
"two-titration method") to determine the levels of styrenic polymer
sulfonic acid, sulfuric acid, and non-polymeric by-product sulfonic
acid (e.g. 2-sulfo-alkylcarboxylic acid), and then to calculate the
degree of styrene sulfonation based on mass balance. Alternatively,
the level of sulfonation can be determined by titration of a dry
polymer sample, which has been re-dissolved in tetrahydrofuran with
a standardized solution of NaOH in a mixture of alcohol and water.
In the latter case, rigorous removal of by-product acids are
preferably ensured.
[0123] Although embodiments for sulfonating polymers are described
above in the context of acyl sulfate reagents, the utility of other
sulfonation reagents are also contemplated. For example, the use of
those sulfonation reagents derived from the complexation/reaction
of sulfur trioxides with phosphate esters such as triethylphosphate
has been demonstrated in the present technology. The chemistry of
such sulfonation reagents is known in the art to afford aromatic
sulfonation with significant degrees of sulfonic acid alkyl ester
incorporation. As such, the resultant sulfonated polymers likely
contain both sulfonic acid and sulfonic acid alkyl ester groups.
Other contemplated sulfonation reagents include, but are not
limited to, those derived from the reaction or complexation of
sulfur trioxide with phosphous pentoxide, polyphosphoric acid,
1,4-dioxane, triethylamine, etc.
d) Reaction Conditions
[0124] The sulfonation reaction between the acyl sulfates and
sulfonation susceptible block copolymers such as
aromatic-containing polymers (e.g., styrenic block copolymers) can
be conducted at a reaction temperature in the range of from about
20.degree. C. to about 150.degree. C., alternatively from about
20.degree. C. to about 100.degree. C., alternatively from about
20.degree. C. to about 80.degree. C., alternatively from about
30.degree. C. to about 70.degree. C., alternatively from about
40.degree. C. to about 60.degree. C. (e.g., at about 50.degree.
C.). The reaction time can be in the range of from approximately
less than 1 minute to approximately 24 hours or longer, dependent
on the temperature of the reaction. In some preferred acyl sulfate
embodiments that utilize in-situ reaction of carboxylic anhydride
and sulfuric acid, the initial temperature of the reaction mixture
can be about the same as the intended sulfonation reaction
temperature. Alternatively, the initial temperature may be lower
than the intended subsequent sulfonation reaction temperature. In a
preferred embodiment, the acyl sulfate can be generated in-situ at
about 20.degree. C. to about 40.degree. C. (e.g., at about
30.degree. C.) for about 0.5 to about 2 hours, alternatively about
1 to about 1.5 hours, and then the reaction mixture can be heated
to about 40.degree. C. to about 60.degree. C. to expedite the
completion of the reaction.
[0125] Although not required, an optional reaction quenching step
can be conducted through the addition of a quenching agent, which
can be, for example, water or hydroxyl-containing compounds such as
methanol, ethanol, or isopropanol. Typically in such a step, an
amount of the quenching agent at least sufficient to react with
residual unreacted acyl sulfate may be added.
[0126] In some embodiments of the presently described technology,
the sulfonation of the aromatic-containing polymer in a
non-halogenated aliphatic solvent can be carried out by contacting
the aromatic-containing polymer with a sulfonation reagent in a
batch reaction or a semi-batch reaction. In some other embodiments
of the present technology, the sulfonation can be carried out in a
continuous reaction, which can be enabled, for example, through the
use of a continuous stirred tank reactor or a series of two or more
continuous stirred tank reactors.
[0127] As a result of sulfonation, the micelle cores contain
sulfonation susceptible blocks having sulfonic acid and/or
sulfonate ester functionality which are surrounded by an outer
shell containing sulfonation resistant blocks of the block
copolymer. The driving force for this phase segregation (causing
the micelle formation) in solution has been attributed to the
considerable difference in polarity between the sulfonated block(s)
and the non-sulfonated blocks of the sulfonated block copolymer.
The latter blocks are freely solvable by a non-halogenated
aliphatic solvent, for example the first solvent disclosed above.
On the other hand, the sulfonated polymer block(s) may arrange to
concentrate in the core of micelle.
e. Storage and Stabilization of Polar Components
[0128] The micellar solution of the sulfonated block copolymer
having at least one end block A and at least one interior block B
wherein each block A contains essentially no sulfonic acid or
sulfonate ester functional groups and each block B is a polymer
block containing from about 10 to about 100 mol % sulfonic acid or
sulfonate ester functional groups based on the number of monomer
units present in the block B in a one non-polar liquid phase has
surprisingly been found to be stable in the presence of a polar
component. In fact, the micellar solution of the sulfonated block
copolymer has been found to "react" with the polar component
without collapsing the micellar structure. Instead, the polar
component has been found to be immured by the micelles of the
sulfonated block copolymer in the non-polar liquid phase, thereby
storing and/or stabilizing the polar compound in the non-polar
liquid phase.
[0129] In one embodiment, a micellar solution of the sulfonated
block copolymer and a non-polar, liquid phase which is adapted for
storing and/or stabilizing a polar component is obtained by
dissolving a sulfonated block copolymer having at least one end
block A and at least one interior block B wherein each block A
contains essentially no sulfonic acid or sulfonate ester functional
groups and each block B is a polymer block containing from about 10
to about 100 mol % sulfonic acid or sulfonate ester functional
groups based on the number of monomer units present in the block B
in a one non-polar liquid phase.
[0130] In some embodiments, the non-polar, liquid phase is formed
by one or more aprotic apolar solvents which are preferably
non-halogenated. Illustrative examples include hydrocarbons having
from 4 to 12 carbon atoms. The hydrocarbons may be straight-chain,
branched or mono- or polycyclic and may comprise straight-chain,
branched as well as mono- or polycyclic hydrocarbon groups such as,
e.g., straight-chain, branched or cyclic pentane, (mono-, di- or
tri-) methylcyclopentane, (mono-, di- or tri-) ethylcyclopentane,
straight-chain, branched or cyclic hexane, (mono-, di- or tri-)
methylcyclohexane, (mono-, di- or tri-) ethylcyclohexane,
straight-chain, branched or cyclic heptane, straight-chain,
branched or (mono- or bi-) cyclic octane, 2-ethyl hexane,
isooctane, nonane, decane, paraffinic oils, mixed paraffinic
solvents, and the like.
[0131] In particular embodiments, the non-polar liquid phase
comprises at least one solvent selected from cyclohexane,
methylcyclohexane, cyclopentane, cycloheptane, cyclooctane and
mixtures thereof, with cyclohexane, and/or cyclopentane, and/or
methylcyclohexane.
[0132] In further embodiments, the non-polar liquid phase is formed
by at least two aprotic solvents each of which is preferably
non-halogenated. In further particular embodiments, the non-polar
liquid phase comprises at least one solvent selected from hexanes,
heptanes and octanes and mixtures thereof, with cyclohexane and/or
methylcyclohexane.
[0133] The concentration of the sulfonated block copolymer in the
non-polar liquid phase depends upon the composition of the
sulfonated block polymer, since the limiting concentration below
which polymer gelling is non-disabling or negligible depends upon
the polymer composition. As stated above, the limiting
concentration may also be dependent on other factors such as the
identity of the solvent or the solvent mixture. Generally, the
polymer concentration falls within the range of from about 1%-wt.
to about 30%-wt., alternatively from about 1%-wt. to about 20%-wt.,
alternatively from about 1%-wt. to about 15%-wt., alternatively
from about 1%-wt. to about 12%-wt., or alternatively from about
1%-wt. to about 10%-wt., based on the total weight of a reaction
mixture that is preferably substantially free of halogenated
solvents. It will be understood by those skilled in the art that
suitable ranges include any combination of the specified mol
percents even if the specific combination and range is not listed
herewith.
[0134] The dissolution of the sulfonated block copolymer in the
non-polar, liquid phase to obtain the micellar solution is
achieved, for example, by combining requisite amounts of the
sulfonated block copolymer and the solvent or solvents at a
temperature of from about 20.degree. C. to the boiling point of the
employed solvent or solvents. In general, the dissolution
temperature is in a range of from about 20.degree. C. to about
150.degree. C., alternatively from about 20.degree. C. to about
100.degree. C., alternatively from about 20.degree. C. to about
80.degree. C., alternatively from about 30.degree. C. to about
70.degree. C., alternatively from about 40.degree. C. to about
60.degree. C. (e.g., at about 50.degree. C.). The dissolution time
can be in the range of from approximately less than 1 minute to
approximately 24 hours or longer, dependent on the temperature of
the mixture.
[0135] Alternatively, the micellar solution of the sulfonated block
copolymer may be prepared by sulfonating a corresponding block
copolymer precursor in the manner described in the foregoing.
[0136] Suitable polar components for inclusion in the sulfonated
polymer core of the micelle include, for example, metal compounds
and/or metal salts, in particular compounds and/or salts of metals
of groups 1 to 14 of the Periodic Table of the Elements.
Illustrative metal compounds and/or salts include, for example, the
compounds and/or salts of lithium(I), sodium(I), gold(I), and
cobalt(II), rhodium(II), iridium(II), nickel(II), palladium(II),
platinum(II), zinc(II), iron(II), magnesium(II), calcium(II) and
copper(II) as well as aluminum(III), iron(III), lead(IV) and
titanium(IV).
[0137] Other suitable polar components that may be usefully immured
in the core of the sulfonated polymer micelle include, for example,
active compounds such as pharmaceutically active agents, agents
employed in agriculture, dyes, ignition and flame retardant
compounds, materials having conducting properties, and agents
having specific optical properties. Polar materials having
absorptive properties might be contained in the core of the
sulfonated polymer micelles, as well. Optionally, these materials
may be present in a salt form.
[0138] The polar component may be added to the micellar solution of
the sulfonated block copolymer "in substance" or may be added in
form of a mixture, dispersion or solution with a solvent. The
solvent which may be employed to mix, disperse or dissolve the
polar component is generally not critical. In some embodiments, the
solvent may be water or may be an organic solvent. Organic solvents
in this context may be protic or aprotic, including aprotic-polar
solvents and aprotic apolar solvents and mixtures of two or more
solvents of the same or different nature.
[0139] The amount of polar component which may be added to the
micellar solution of the sulfonated block copolymer depends on the
nature of the polar compound, on the nature and composition of the
solvent or solvents, and on the nature and degree of sulfonation of
the sulfonated block copolymer. In some embodiments, the polar
component may be added to the micellar solution of the sulfonated
block copolymer in amounts of from 0.01 to 100%-wt. based on the
amount of the sulfonated block copolymer. In further embodiments,
the polar component may be added to the micellar solution of the
sulfonated block copolymer in amounts of at least 0.05, preferably
at least 0.1, and more preferably at least 1%-wt. of the sulfonated
block copolymer. In still further embodiments, the polar component
may be added to the micellar solution of the sulfonated block
copolymer in amounts of at most 80, preferably at most 65, and more
preferably at most 50%-wt. of the sulfonated block copolymer. It
will be understood by those skilled in the art that suitable ranges
of amounts include any combination of the specified limit values
even if the combination and range is not specifically listed
herewith.
5. PROCESS TO NEUTRALIZE SULFONATED POLYMERS
[0140] In general, the sulfonated block copolymers are neutralized
by providing a solution of the non-neutralized block copolymer and
an organic solvent and adding at least one compound of a metal
having an atom number of at least 11 to the solution with the metal
compound acting as a base relative to the acidic functionality of
the block copolymer.
[0141] In accordance with some embodiments, the solution of the
non-neutralized block copolymer may be the reaction mixture which
is obtained after sulfonating the block copolymer in the
afore-described manner. In other embodiments, the solution of the
non-neutralized block copolymer can be provided by dissolving a
sulfonated block copolymer in an organic solvent. When a sulfonated
block copolymer is dissolved in a solvent, it is possible to
utilize a raw sulfonation product solution as it is generated in
the sulfonation reactor. It will be understood by those skilled in
the art that it is equally possible to employ a sulfonated block
copolymer which has been isolated from the sulfonation reaction
mixture, and has been washed or otherwise purified, and/or has been
dried. However, such measures generally have not been found to be
necessary and considerations such as process economy may render
such measures undesirable.
[0142] The organic solvent or solvents suitable for providing the
solution of the non-neutralized block copolymer generally include
all solvent and solvent mixtures which are suited to substantially
dissolve the non-sulfonated polymer blocks or to disperse them into
solvated micelles. As such, the solvents may be selected from
aprotic polar or apolar organic solvents such as optionally
partially or fully halogenated (hydro)cabons, optionally
halogenated esters, optionally halogenated ethers and the like. In
particular embodiments with a view to environmental considerations,
the organic solvent or solvents are non-halogenated aprotic polar
or apolar solvents. In some of the preferred embodiments, the
solvent or solvents are aprotic and apolar, for example,
straight-chain, branched and cyclic hydrocarbons having from 5 to
15, or from 5 to 12, or from 6 to 12, carbon atoms such as
n-pentane, iso-pentane, cyclopentane, methyl-cyclopentane,
n-hexane, iso-hexane, cyclohexane, methyl-cyclohexane, n-heptane,
iso-heptane, and the like.
[0143] The concentration of the sulfonated block copolymer in the
organic solvent or solvents is generally adjusted so that gelling
of the provided solution is avoided. Normally, the concentration at
which gelling may occur will depend upon the nature of the
sulfonated block copolymer, including the degree of sulfonation
thereof, and upon the selected solvent or solvent mixture.
Generally, the polymer concentration may be within the range of
from about 1%-wt. to about 30%-wt., alternatively from about 1%-wt.
to about 20%-wt., alternatively from about 1%-wt. to about 15%-wt.,
alternatively from about 1%-wt. to about 12%-wt., or alternatively
from about 1%-wt. to about 10%-wt., based on the total weight of a
reaction mixture that is preferably substantially free of
halogenated solvents. It will be understood by those skilled in the
art that suitable ranges include any combination of the specified
mol percents even if the specific combination and range is not
listed herewith.
[0144] In particular embodiments of the neutralization process, the
solution of the sulfonated block copolymer in the organic solvent
comprises the non-neutralized block copolymer in a micellar form as
addressed in the foregoing sections.
[0145] The sulfonated block copolymer is neutralized by adding at
least one compound of a metal having an atom number of at least 11
to the optionally micellar solution of the sulfonated block
copolymer. The expression "metal" as used in this context is meant
to refer to an element which is understood in the art as a metal,
and is meant to specifically exclude those elements which are
understood in the art as semi-metallic elements. Semi-metallic
elements are in their elemental state not malleable or ductile and
are neither good conductors nor good insulators such as boron,
silicon, germanium antimony, tellurium, polonium and astatine, all
of which are understood by those skilled in the art to be
semimetals. As such, the expression "metal" as used in the context
of this aspect essentially encompasses all elements having an atom
number of at least 11 and being listed in the Periodic Table of the
Elements to the left of, or below, the afore-mentioned
semi-metallic elements.
[0146] In some embodiments, the metal is selected from the metals
of periods 3, 4, 5 or 6 of the Periodic Table of the Elements. In
other embodiments, the metal is selected from groups 2 to 14 of the
Periodic Table of the Elements. In particular embodiments, the
metal is selected from among the metals of periods 3 through 6 and
groups 2 to 14. Representative metals of period 3 are sodium,
magnesium and aluminum. Representative metals of period 4 are
potassium, calcium, scandium, titanium, vanadium, chromium,
manganese, iron, cobalt, nickel, copper, zinc and gallium.
Representative metals of period 5 are strontium, zirconium,
molybdenum, ruthenium, rhodium, palladium, silver, cadmium and tin.
Representative metals of period 6 are barium, hafnium, platinum,
gold, mercury and lead.
[0147] In further embodiments, the metal is selected from the
metals of groups 2, 4, 6, 11, 12, 13 and 14. Representative metals
of group 2 are magnesium, calcium, strontium and barium.
Representative metals of group 4 are titanium, zirconium and
hafnium. Representative metals of group 6 are chromium, molybdenum
and tungsten. Representative metals of group 11 are copper, silver
and gold. Representative metals of group 12 are zinc, cadmium and
mercury. Representative metals of group 13 are aluminum, gallium,
indium and thallium. Representative metals of group 14 are tin and
lead. In particular embodiments the metal is selected from among
the metals of periods 3 to 6 and groups 2, 4, 6, 11, 12, 13 and
14.
[0148] In still further embodiments, the metal is sodium,
potassium, cesium, magnesium, calcium, strontium, barium, aluminum,
tin, lead, titanium, zirconium, vanadium, chromium, molybdenum,
manganese, iron, cobalt, nickel, copper, silver, zinc, cadmium, or
mercury, in particular magnesium, aluminum, calcium, titanium,
chromium, copper or zinc.
[0149] The metal is employed in the neutralization process in form
of a compound with the metal being present in the compound in an
oxidation state of at least +1. In some embodiments, the metal is
present in the metal compound in an oxidation state of at most +4.
In particular embodiments the metal is present in the compound in
an oxidation state of +1, +2 or +3, or in an oxidation state of +2,
+3 or +4. It will be understood by those skilled in the art that
the metal compound may comprise a single metal in one or more
oxidation states, and may comprise a combination of one or more
metals having the same or different oxidation states.
[0150] A broad variety of metal compounds may be used according to
the method so long as the metal compound is sufficiently soluble or
dispersible in the solution of the non-neutralized block copolymer
to ensure contact between the metal compound and the
non-neutralized block copolymer and the metal compound reacts as a
base in the presence of the acidic sites in the block copolymer.
Suitable compounds include, for example, inorganic compounds such
as halogenides, oxides, hydroxides, sulfides, sulfites, sulfates,
nitrates, phosphates, carbonates, hydrogencarbonates, borates,
hydrides and the like; organic compounds such as formates,
carboxylates, alcoholates, and so called "organometal compounds,"
i.e., metal compounds which comprise hydrocarbyl groups, and the
like; as well as compounds comprising inorganic as well as organic
moieties such as, for example, organometal halogenides.
[0151] Suitable compounds include in particular those compounds in
which the metal is present in combination with at least one group
which forms a weaker coordination with the metal than the
coordination between the metal and the sulfonic acid or sulfonate
ester group of the sulfonated block copolymer. It will be
understood by those skilled in the art that the nature of the metal
may determine whether the coordination of the metal to the group in
question is weaker than the coordination of the metal to the
sulfonic acid or sulfonate ester group of the sulfonated block
copolymer.
[0152] Suitable compounds also include in particular those
compounds in which the metal is present in combination with at
least one group capable of reacting with a proton of the sulfonic
acid or with the sulfonate ester group of the sulfonated block
copolymer to form a more stable coordination or bond than with the
metal. For example, a hydride or an organyl group may react with a
proton to form hydrogen or an organic compound. Similarly, a
carbonate or hydrogencarbonate may form carbon dioxide and water
under the influence of protons, and an oxide or hydroxide may form
water under the influence of protons.
[0153] In some embodiments the metal compound comprises at least
one group such as oxide, hydroxide, alcoholate, formate, carbonate,
hydrogencarbonate or carboxylate. Alcoholate groups generally have
at least one and may have up to eight carbon atoms with the
hydrocarbon moiety being straight-chain, branched, cyclic or a
combination thereof. Illustrative examples of such alcoholate
groups include methoxylate, ethoxylate, n-propoxylate,
iso-propoxylate, ethylhexyloxylate, cyclohexyloxylate,
methylcyclohexyloxylates and the like. Carboxylate groups generally
have at least two and may have up to eight carbon atoms with the
hydrocarbon moiety being straight-chain, branched, cyclic or a
combination thereof. Illustrative examples of such carboxylate
groups include acetate, n-propionate, iso-propionate,
ethylhexanoate, stearate, cyclohexylcarboxylate,
methylcyclohexylcarboxylates, and the like.
[0154] In other embodiments the metal compound comprises at least
one hydride or hydrocarbyl group. Hydrocarbyl groups of such
compounds generally have at least one and up to ten, or up to
eight, or up to six, carbon atoms and may be straight-chain,
branched, cyclic or a combination thereof. Illustrative examples
include methyl, ethyl, n- and iso-propyl, n-, iso- and tert-butyl,
n-, iso-, neo- and cyclopentyl, n-, iso-, neo- and cyclohexyl,
phenyl, tolyl, and the like.
[0155] Ease of handling of the metal compound as well as economic
considerations may govern the choice of the metal compound.
Accordingly, metal compound such as oxides, hydroxides,
alcoholates, formates, carbonates, hydrogencarbonates, carboxylates
and the like may be preferred.
[0156] Additionally and with a view to an economic purification of
the neutralized sulfonylated block copolymer as a material for
membranes, for example, it may be preferred to employ a metal
compound which comprises groups that allow an easy purification of
the product, i.e., groups which react to form compounds that are
easily separated such as hydrogen, carbon dioxide, hydrocarbons,
alcohols, carboxylic acids, etc. It will be understood by those
skilled in the art how to balance any draw-backs and benefits in
handling of the metal compound and in process economy.
[0157] The amount of the metal compound which is employed for
neutralizing the sulfonated block copolymer depends upon the moles
of sulfonic acid or sulfonate ester groups present in the
sulfonated block copolymer and on the desired level of
neutralization. When the amount of metal compound is less than
about 80% of the stoichiometric amount with respect to the sulfonic
acid or sulfonate ester groups present in the sulfonated block
copolymer, the metal compound will normally react quantitatively.
For levels of neutralization above about 80%, it has been found to
be advantageous to employ the metal compound in excess. Normally,
the amount of metal compound may be employed in amounts ranging
from about 50% to about 2000% of the stoichiometric amount with
respect to the sulfonic acid or sulfonate ester functionalities of
the sulfonated block copolymer.
[0158] In some embodiments the metal compound may be added in at
least about 60%, particularly at least about 70%, more particularly
at least about 80%, or at least about 100% of the stoichiometric
amount with respect to the sulfonic acid or sulfonate ester groups
present in the sulfonated block copolymer. Further, the metal
compound may be added in at most about 1500%, particularly at most
about 750%, more particularly at most about 500%, or at most about
250% or at most about 200%, of the stoichiometric amount with
respect to the sulfonic acid or sulfonate groups present in the
sulfonated block copolymer. It will be understood by those skilled
in the art that suitable ranges include any combination of the
specified stoichiometric amounts even if the specific combination
and range is not listed herewith.
[0159] The amount of the metal compound which is employed for
neutralizing the sulfonated block copolymer further depends upon
the oxidation state of the metal. Without wanting to be bound by
any particular theory, it is believed that one sulfonic acid or
sulfonate ester group may be neutralized by one charge equivalent
of the metal in the metal compound. Accordingly, a metal in an
oxidation state of +1 may neutralize one sulfonic acid or sulfonate
group, a metal in an oxidation state of +2 may neutralize two
sulfonic acid or sulfonate ester groups, etc. Therefore, the
aforementioned stoichiometric amounts of the metal compound are
based on the charge equivalent of the metal in the metal
compound.
[0160] The level of neutralization may be adjusted within broad
ranges, e.g., from about 70% to about 100% of the sulfonic acid or
sulfonate ester groups being neutralized by at least one charge
equivalent to one mole of the metal compound per equivalent of
sulfonic acid functionality in the block copolymer. In other
embodiments the level of neutralization is at least about 80%,
particularly at least about 85%, more particularly at least about
90% of the sulfonic acid or sulfonate ester groups being
neutralized by at least one charge equivalent and up to one mole of
the metal compound per equivalent of sulfonic acid functionality in
the block copolymer. In some embodiments, at most about 95%,
preferably at most about 98%, more particularly 100%, of the
sulfonic acid or sulfonate ester groups are neutralized by at least
one charge equivalent and up to one mole of the metal compound per
equivalent of sulfonic acid functionality in the block
copolymer.
[0161] In some of the embodiments, the level of neutralization may
be higher where the non-neutralized block copolymer has a lower
degree of sulfonation, e.g., where the degree of sulfonation of the
non-neutralized block copolymer is in a range of from about 10 to
about 70 mol %, the level of neutralization may be in a range of
from 90 to 100%. In other embodiments, the level of neutralization
may be lower where the non-neutralized block copolymer has a higher
degree of sulfonation, e.g., where the degree of sulfonation of the
non-neutralized block copolymer is in a range of about 65 to 100
mol %, the level of neutralization may be in a range of from about
75% to 100%. Higher levels of neutralization have surprisingly been
found to reduce the tendency of the neutralized sulfonated block
copolymer to swell when employed in an aqueous environment.
[0162] Generally, the metal compound may be added to the solution
of the sulfonated block copolymer "in substance," or it may be
added as a mixture, dispersion or solution with a solvent. The
solvent which may be employed to mix, disperse or dissolve the
metal compound is generally not critical. In some embodiments, the
solvent may be water or may be an organic solvent. Organic solvents
in this context may be protic or aprotic, including aprotic-polar
solvents and aprotic apolar solvents and mixtures of two or more
solvents of the same or different nature. It will be understood by
those skilled in the art that some metal compound such as metal
hydrides, organometal compounds and organometal halogenides may be
hazardous in substance and may necessitate that the metal compound
be handled in dispersed form, or as a solution, in an inert solvent
or diluent. It is important that these metal compounds do not react
with protic species in the solvent. In addition, it is important to
note that many of these metal hydrides, organometal compounds and
organometal halogenides react vigorously with oxygen and must be
handled in the absence of oxygen. Under those circumstances it is
therefore preferred that all due care be taken.
[0163] In one aspect of the neutralization process, and apart from
restrictions due to otherwise hazardous conditions, the metal
compound is added to the solution of the sulfonated block copolymer
in substance.
[0164] In another aspect of the neutralization process, again apart
from restrictions due to otherwise hazardous conditions, the metal
compound is added to the solution of the sulfonated block copolymer
as a mixture, dispersion or solution with water or with an organic
solvent. In some embodiments of this aspect, the solvent is water
or is a protic or aprotic-polar solvent such as an alcohol, e.g.,
methanol, ethanol, and the like; a carboxylic acid, e.g., formic
acid, acetic acid, propionic acid, and the like, an ether, e.g.,
methyl-tert-butyl ether, tetrahydrofuran (THF), dioxan and the
like, an ester, e.g., ethyl acetate and the like, a ketone, e.g.,
methyl-iso-butylketone (MIBK) and the like, a formamide, e.g.,
dimethylformamide (DMF) and the like, a sulfoxide, e.g.,
dimethylsulfoxide (DMSO) and the like. It will be understood by
those skilled in the art that the solvent employed for mixing,
dispersing or dissolving the metal compound may be a single
solvent, i.e., water or one of the aforementioned organic protic or
aprotic polar solvents or may be a combination of water and one or
more organic solvents, or may be a combination of one or more
organic solvents.
[0165] In still another aspect of the neutralization process, the
solvent or solvents employed for mixing, dispersing or dissolving
the metal compound(s) is(are) selected from the group of water,
alcohols having from 1 to 4 carbon atoms, carboxylic acids having
from 1 to 5 carbon atoms, and aprotic-polar and aprotic-apolar
solvents. In some embodiments of this aspect, the solvent(s)
is(are) selected from water, C.sub.1-C.sub.4-alcohols and
C.sub.1-C.sub.5-carboxylic acids. In other embodiments of this
aspect, the solvent(s) is(are) selected from aprotic-polar an
aprotic-apolar solvents. In particular embodiments, the solvent(s)
is(are) selected from aprotic-apolar non-halogenated solvents.
[0166] The neutralization reaction may normally be conducted at a
temperature in the range of from -40.degree. C. to the boiling
point of the solvent or solvent mixture. The reaction may be
exothermic, i.e., may increase the temperature of the reaction
medium by about 10 to 20.degree. C., depending on the nature of the
metal compound, the amount per time in which the metal compound is
added, and on the degree to which the block copolymer is
sulfonated. In some of the embodiments, the temperature may be in
the range of from about -40.degree. C. to about +100.degree. C., or
from about 20.degree. C. to about +60.degree. C.
[0167] The metal compound, "in substance" or in mixture, dispersion
or solution, and the solution of the sulfonated block copolymer may
be combined by metering the metal compound into the solution of the
sulfonated block copolymer, by metering the sulfonated block
copolymer into the metal compound, with the metal compound being
present in "in substance" or in mixture, dispersion or solution,
preferably in mixture, dispersion or solution, or by metering the
metal compound and the solution of the sulfonated block copolymer,
simultaneously but separately, into a reaction medium. In some
embodiments it is preferred to meter the metal compound, "in
substance" or in mixture, dispersion or solution, and the solution
of the sulfonated block copolymer may be combined by metering the
metal compound into the solution of the sulfonated block
copolymer.
[0168] It will be understood by those skilled in the art that the
reaction time may be dependent upon the reaction temperature and
the reactivity of the metal compound. The expression "reaction
time" in this context is understood to be the interval of time
starting when all of the reactants have been combined and ending
when the neutralization reaction has reached completion. Generally,
the reaction time may range from approximately less than 1 minute
to approximately 24 hours or longer. Preferably, completion is
reached within about 1 hour, or within 30 minutes.
[0169] The neutralized sulfonated block copolymer may be separated
from the reaction mixture by evaporating the reaction solvent(s)
optionally at a reduced pressure and optionally at an elevated
temperature. In some embodiments, the reaction mixture comprising
the neutralized sulfonated block copolymers may be used without
further processing to cast films or membranes.
6. PROPERTIES OF NEUTRALIZED BLOCK POLYMERS
[0170] The metal neutralized sulfonated block copolymers as
described herein possess unexpected and superior performance
properties. On the one hand, it has been found that neutralizing
the sulfonated block copolymers with the aforementioned metal
compounds provides a reinforcing effect on the sulfonated block
copolymers in the wet state. In other words, when immersed in
water, the metal neutralized block copolymer exhibits a higher
tensile modulus than a corresponding, non-neutralized sulfonated
block copolymer in the wet state. On the other hand, when not
immersed in water, the metal neutralized sulfonated block
copolymers exhibit a dry tensile modulus which is essentially the
same or is lower than the modulus of a corresponding,
non-neutralized sulfonated block copolymer in the dry state.
Therefore, according to some embodiments, the difference between
the modulus of the metal neutralized block copolymer in the wet and
the dry state is less than the difference between the modulus of
the corresponding, non-neutralized block copolymer in the wet and
the dry state. This has the advantage that the metal neutralized
block copolymer is less likely to soften when introduced into, or
when employed in, an aqueous environment than is the case with the
corresponding, non-neutralized sulfonated block copolymer,
rendering the metal neutralized sulfonated block copolymer
significantly better suited for applications which require
dimensional stability under wet conditions. A film or membrane cast
from the metal neutralized sulfonated block copolymer will exhibit
improved rigidity in a wet environment over its non-neutralized
analog.
[0171] In some embodiments the metal neutralized sulfonated block
copolymers have a wet tensile modulus which is equal to or less
than that of the corresponding, non-neutralized sulfonated block
copolymer. In other embodiments the wet tensile modulus is
increased to a range of from 100% to over 500% of the tensile
modulus of the corresponding, non-neutralized sulfonated block
copolymer. In other embodiments, the wet tensile modulus is
increased to the range of from 100% to over 1000% of the tensile
modulus of the corresponding, non-neutralized sulfonated block
copolymer. In further embodiments, the wet tensile modulus is
increased to the range of from 100% to over 3000% of the tensile
modulus of the corresponding, non-neutralized sulfonated block
copolymer. In even further embodiments, the wet tensile modulus is
increased to the range of from 200% to over 3000% of the tensile
modulus of the corresponding, non-neutralized sulfonated block
copolymer. It will be understood by those skilled in the art that
suitable ranges include any combination of the specified percents
even if the specific combination and range is not listed
herewith.
[0172] In another aspect, the tensile modulus of the metal
neutralized block copolymer may be the same or similar in both the
wet and the dry state. Accordingly, in some embodiments, the metal
neutralized block copolymer disclosed herein has a wet tensile
modulus that is not less than 10% of the dry tensile modulus. In
other embodiments, the wet tensile modulus is not less than 20% of
the dry tensile modulus. In additional embodiments, the wet tensile
modulus is not less than 40% of the dry tensile modulus. In other
embodiments, the wet tensile modulus is not less than 100% of the
dry tensile modulus. In other embodiments, the wet tensile modulus
exceeds the dry tensile modulus of the metal neutralized sulfonated
block copolymer. It will be understood by those skilled in the art
that suitable ranges include any combination of the specified
percents even if the specific combination and range is not listed
herewith.
[0173] Furthermore, in some embodiments, the wet tensile strength
at break of the metal neutralized block copolymer is at least about
40% of the dry tensile strength at break. In other embodiments, the
wet tensile strength at break of the neutralized block copolymer is
at least about 50% of the dry tensile strength at break. In further
embodiments, the wet tensile strength at break of the neutralized
block copolymer is at least about 75% of the dry tensile strength
at break. In further embodiments, the wet tensile strength at break
of the neutralized block copolymer is at about the same as the dry
tensile strength at break. It will be understood by those skilled
in the art that suitable ranges include any combination of the
specified percents even if the specific combination and range is
not listed herewith. It will be understood by those skilled in the
art that the foregoing reference to minimum percents, in each case,
includes embodiments in which the wet tensile strength exceeds the
dry tensile strength.
[0174] Additionally and surprisingly it has been found that the
metal neutralized sulfonated block copolymer described herein has
advantageous water uptake properties. In some embodiments, the
water uptake value of the metal neutralized sulfonated block
copolymer is equal to or less than the water uptake value of a
corresponding, non-neutralized block copolymer. In other
embodiments the metal neutralized sulfonated block copolymer has a
water uptake value of less than 80%, preferably less than 50%,
still more preferably less than 20%, of the water uptake value of a
corresponding, non-neutralized sulfonated block copolymer. In some
embodiments, the metal neutralized sulfonated block copolymer has a
water uptake value of about or less than 50%-wt., preferably about
or less than 40%-wt., still more preferably about or less than
25%-wt., of its dry weight. The water uptake properties of the
metal neutralized sulfonated block copolymers, also, render the
neutralized block copolymer significantly improved with respect to
dimensional stability in the wet state as compared with the
corresponding non-neutralized sulfonated block copolymer.
[0175] Furthermore, in some embodiments, the water uptake value of
the metal neutralized block copolymer may range from 5%-wt. to
100%-wt. In other embodiments, the water uptake value of the
neutralized block copolymer may range from 20%-wt. to 75%-wt. In
additional embodiments, the water uptake value of the neutralized
block copolymer is from 20%-wt. to 50%-wt. In further embodiments,
the water uptake value of the neutralized block copolymer is from
20%-wt. to 40%-wt. In still further embodiments, the water uptake
value of the neutralized block copolymer is from 20%-wt. to 35%-wt.
It will be understood by those skilled in the art that suitable
ranges include any combination of the specified percents even if
the specific combination and range is not listed herewith.
[0176] While the metal neutralized sulfonated block copolymers
described herein take up some water in an aqueous environment,
e.g., at least 0.1%-wt. based on the dry weight, it has
surprisingly been found that the water uptake generally does not
result in a noteworthy change in volume on wet/dry cycling. The
surprising and advantageous dimensional stability is desirable in
water management membranes, i.e., in applications where a membrane
is constrained in a mounting device and small changes in the
dimensions of the membrane may cause buckling and tearing, thereby
inevitably causing the performance of the device to degrade or even
fail. The surprising and advantageous dimensional stability is also
desirable, for example, for desalination applications, humidity
regulation devices, battery separators, fuel cell exchange
membranes, medical tubing applications and the like.
[0177] Additionally and surprisingly, it has been found that the
metal neutralized block copolymers disclosed herein have high water
vapor transport rates while at the same time having very good
dimensional stability. It was surprisingly found that the water
vapor transport rate (WVTR) of the metal neutralized sulfonated
block copolymers is the same or similar to the WVTR of a
corresponding non-neutralized block copolymer, and in some
embodiments may even exceed the WVTR of the corresponding,
non-neutralized block copolymer. Accordingly, in some embodiments
the WVTR of the metal neutralized sulfonated block copolymer is at
least about 50% of the WVTR of a corresponding non-neutralized
sulfonated block copolymer. In other embodiments, the WVTR is at
least about 65% of the WVTR of a corresponding non-neutralized
sulfonated block copolymer. In further embodiments, the WVTR is at
least about 75% of the WVTR of a corresponding non-neutralized
sulfonated block copolymer. In still further embodiments, the WVTR
is at least about 85% of the WVTR of a corresponding
non-neutralized sulfonated block copolymer. In even further
embodiments, the WVTR is at least about 90% of the WVTR of a
corresponding non-neutralized sulfonated block copolymer. In
additional embodiments, the WVTR is at least about 95% of the WVTR
of a corresponding non-neutralized sulfonated block copolymer. In
further embodiments, the WVTR is at least about 99% of the WVTR of
a corresponding non-neutralized sulfonated block copolymer. It will
be understood by those skilled in the art that suitable ranges
include any combination of the specified percents even if the
specific combination and range is not listed herewith.
[0178] The WVTR of the metal neutralized sulfonated block
copolymers may be quantified in terms of grams of water which are
transported through a membrane, which is 1 mil thick and has an
exposed surface area of 1 m.sup.2, in a day (g/m.sup.2/day/mil). In
some embodiments, the metal neutralized sulfonated block copolymers
as disclosed herein have a WVTR of at least about 15,000
g/m.sup.2/day/mil. In other embodiments, the WVTR is at least about
18,000 g/m.sup.2/day/mil. In further embodiments, the WVTR is at
least about 20,000 g/m.sup.2/day/mil. In even further embodiments,
the WVTR is at least about 22,000 g/m.sup.2/day/mil. In still
further embodiments, the WVTR is at least about 23,000
g/m.sup.2/day/mil. It will be understood by those skilled in the
art that suitable ranges include any combination of the specified
rates even if the specific combination and range is not listed
herewith.
7. APPLICATIONS OF THE NEUTRALIZED BLOCK COPOLYMERS
[0179] The neutralized sulfonated block copolymers may be
compounded with other components not adversely affecting the
copolymer properties. The neutralized block copolymers may be
blended with a large variety of other polymers, including olefin
polymers, styrene polymers, hydrophilic polymers and engineering
thermoplastic resins, with polymer liquids and other fluids such as
ionic liquids, natural oils, fragrances, and with fillers such as
nanoclays, carbon nanotubes, fullerenes, and traditional fillers
such as talcs, silica and the like.
[0180] Additionally, the neutralized sulfonated block copolymers
may be blended with conventional styrene/diene and hydrogenated
styrene/diene block copolymers, such as the styrene block
copolymers available from Kraton Polymers LLC. Illustrative styrene
block copolymers include linear S--B--S, S--I--S, S-EB--S, S-EP--S
block copolymers. Also included are radial block copolymers based
on styrene along with isoprene and/or butadiene and selectively
hydrogenated radial block copolymers. Particularly useful are
blends with the block copolymer precursor, the block copolymer
prior to sulfonation.
[0181] Olefin polymers include, for example, ethylene homopolymers,
ethylene/alpha-olefin copolymers, propylene homopolymers,
propylene/alpha-olefin copolymers, high impact polypropylene,
butylene homopolymers, butylene/alpha olefin copolymers, and other
alpha olefin copolymers or interpolymers. Representative
polyolefins include, for example, but are not limited to,
substantially linear ethylene polymers, homogeneously branched
linear ethylene polymers, heterogeneously branched linear ethylene
polymers, including linear low density polyethylene (LLDPE), ultra
or very low density polyethylene (ULDPE or VLDPE), medium density
polyethylene (MDPE), high density polyethylene (HDPE) and high
pressure low density polyethylene (LDPE). Other polymers included
hereunder are ethylene/acrylic acid (EEA) copolymers,
ethylene/methacrylic acid (EMAA) ionomers, ethylene/vinyl acetate
(EVA) copolymers, ethylene/vinyl alcohol (EVOH) copolymers,
ethylene/cyclic olefin copolymers, polypropylene homopolymers and
copolymers, propylene/styrene copolymers, ethylene/propylene
copolymers, polybutylene, ethylene carbon monoxide interpolymers
(for example, ethylene/carbon monoxide (ECO) copolymer,
ethylene/acrylic acid/carbon monoxide terpolymer and the like).
Still other polymers included hereunder are polyvinyl chloride
(PVC) and blends of PVC with other materials.
[0182] Styrene polymers include, for example, crystal polystyrene,
high impact polystyrene, medium impact polystyrene,
styrene/acrylonitrile copolymers, styrene/acrylonitrile/butadiene
(ABS) polymers, syndiotactic polystyrene, sulfonated polystyrene
and styrene/olefin copolymers. Representative styrene/olefin
copolymers are substantially random ethylene/styrene copolymers,
preferably containing at least 20, more preferably equal to or
greater than 25%-wt. copolymerized styrene monomer.
[0183] Hydrophilic polymers include polymeric bases which are
characterized as having an available pair of electrons for
interaction with acids. Examples of such bases include polymeric
amines such as polyethyleneamine, polyvinylamine, polyallylamine,
polyvinylpyridene, and the like; polymeric analogs of nitrogen
containing materials such as polyacrylamide, polyacrylonitrile,
nylons, ABS, polyurethanes and the like; polymeric analogs of
oxygen containing compounds such as polymeric ethers, esters, and
alcohols; and acid-base hydrogen bonding interactions when combined
with glycols such as polyethylene glycol, and polypropylene glycol,
and the like, polytetrahydrofuran, esters (including polyethylene
terephthalate, polybutyleneterephthalate, aliphatic polyesters, and
the like), and alcohols (including polyvinylalcohol), poly
saccharides, and starches. Other hydrophilic polymers that may be
utilized include sulfonated polystyrene. Hydrophilic liquids such
as ionic liquids may be combined with the polymers of the present
invention to form swollen conductive films or gels. Ionic liquids
such as those described in U.S. Pat. No. 5,827,602 and U.S. Pat.
No. 6,531,241 (which disclosures are herein incorporated by
reference) may be introduced into the neutralized sulfonated
polymers either by swelling a previously cast membrane, or by
adding to the solvent system before casting a membrane, coating a
film or forming a fiber.
[0184] Illustrative materials that may be used as additional
components include, without limitation: (1) pigments, antioxidants,
stabilizers, surfactants, waxes, and flow promoters; (2)
particulates, fillers and oils; and (3) solvents and other
materials added to enhance processability and handling of the
composition.
[0185] Pigments, antioxidants, stabilizers, surfactants, waxes and
flow promoters, when utilized in combination with the neutralized
sulfonated block copolymers may be included in amounts up to and
including 10%-wt., i.e., from 0 to 10%, based on the total weight
of the composition. When any one or more of these components are
present, they may be present in an amount from about 0.001 to about
5%-wt., and more preferably from about 0.001 to about 1%-wt.
[0186] Particulates, fillers and oils may be present in an amount
up to and including 50%-wt., from 0 to 50% based on the total
weight of the composition. When any one or more of these components
are present, they may be present in an amount from about 5 to about
50%-wt., preferably from about 7 to about 50%-wt.
[0187] It will be understood by those having ordinary skill in the
art that the amount of solvents and other materials added to
enhance processability and handling of the composition will in many
cases depend upon the particular composition formulated as well as
the solvent and/or other material added. Typically such amount will
not exceed 50%, based on the total weight of the composition
[0188] The metal neutralized sulfonated block copolymers described
herein can be employed in a variety of applications and end uses,
and their property profile renders them particularly suited as
materials in applications which require high modulus when immersed
in water, good wet strength, good dimensional stability, good water
and proton transport characteristics, good methanol resistance,
easy film or membrane formation, good barrier properties,
controlled flexibility and elasticity, adjustable hardness, and
thermal/oxidative stability.
[0189] In one embodiment of the present invention, the metal
neutralized sulfonated block copolymers may be used in
electrochemical applications, such as in fuel cells (separator
phase), proton exchange membranes for fuel cells, dispersions of
metal impregnated carbon particles in sulfonated polymer cement for
use in electrode assemblies, including those for fuel cells, water
electrolyzers (electrolyte), acid batteries (electrolyte
separator), super capacitors (electrolyte), separation cell
(electrolyte barrier) for metal recovery processes, sensors
(particularly for sensing humidity) and the like. The metal
neutralized sulfonated block copolymers are also used as
desalination membranes, and in coatings on porous membranes. Their
selectivity in transporting gases makes them useful for gas
separation applications. Additionally, the metal neutralized
sulfonated block copolymers are used in protective clothing and
breathable fabric applications where the membranes, coated fabrics,
and fabric laminates could provide a barrier of protection from
various environmental elements (wind, rain, snow, chemical agents,
biological agents) while offering a level of comfort as a result of
their ability to rapidly transfer water from one side of the
membrane or fabric to the other, e.g., allowing moisture from
perspiration to escape from the surface of the skin of the wearer
to the outside of the membrane or fabric and vice versa. Full
enclosure suits made from such membranes and fabrics may protect
first responders at the scene of an emergency where exposure to
smoke, a chemical spill, or various chemical or biological agents
are a possibility. Similar needs arise in medical applications,
particularly surgery, where exposure to biological hazards is a
risk. Surgical gloves and drapes fabricated from these types of
membranes are other applications that could be useful in a medical
environment. Articles fabricated from these types of membranes
could have antibacterial and/or antiviral and/or antimicrobial
properties as reported in U.S. Pat. No. 6,537,538, U.S. Pat. No.
6,239,182, U.S. Pat. No. 6,028,115, U.S. Pat. No. 6,932,619 and
U.S. Pat. No. 5,925,621 where it is noted that polystyrene
sulfonates act as inhibitory agents against HIV (human
immunodeficiency virus) and HSV (herpes simplex virus. In personal
hygiene applications, a membrane or fabric of the present invention
that would transport water vapor from perspiration while providing
a barrier to the escape of other bodily fluids and still retain its
strength properties in the wet environment would be advantageous.
The use of these types of materials in diapers and adult
incontinence constructions would be improvements over existing
technologies.
[0190] Accordingly, in some embodiments, the metal neutralized
sulfonated block copolymers described herein are particularly
employed as materials for water vapor transporting membranes which
are employed in wet or aqueous environments. Such membranes are,
for example useful in devices for controlling humidity, devices for
forward electrodialysis, devices for reverse electrodialysis,
devices for pressure retarded osmosis, devices for forward osmosis,
devices for reverse osmosis, devices for selectively adding water,
devices for selectively removing water, and batteries.
8. EXAMPLES
[0191] The following examples are intended to be illustrative only,
and are not intended to be, nor should they be construed as,
limiting the scope of the present invention in any way.
a. Materials and Methods
[0192] The tensile modulus in the dry state as described herein was
measured according to ASTM D412.
[0193] The tensile modulus in the wet state as described herein was
measured similar to the method according ASTM D412 using samples
that had been equilibrated under water for a period of 24 hours
prior to testing, and that were fully submerged under water for
testing.
[0194] All tensile data were collected in a climate controlled room
at 74.degree. F. (23.3.degree. C.) and 50% relative humidity.
[0195] The WVTR as described herein was measured similar to ASTM E
96/E96M. The ASTM method was modified by using a smaller vial,
employing 10 ml of water, and having an area of exposed membrane of
160 mm.sup.2 (as opposed to 1000 mm.sup.2 according to the ASTM
method). After adding the water and sealing the vial with the
membrane test specie, the vial was inverted, and air having a
temperature of 25.degree. C. and a relative humidity of 50% was
blown across the membrane. Weight loss was measured versus time,
and the water transport rate was calculated on the basis of the
measurements as g/m.sup.2, or as g mil/m.sup.2 when normalized for
thickness of the tested membrane.
[0196] The degree of sulfonation as described herein and as
determined by titration was measured by the following
potentiometric titration procedure. The non-neutralized sulfonation
reaction product solution was analyzed by two separate titrations
(the "two-titration method") to determine the levels of styrenic
polymer sulfonic acid, sulfuric acid, and non-polymeric by-product
sulfonic acid (2-sulfoisobutyric acid). For each titration, an
aliquot of about five (5) grams of the reaction product solution
was dissolved in about 100 mL of tetrahydrofuran and about 2 mL of
water and about 2 mL of methanol were added. In the first
titration, the solution was titrated potentiometrically with 0.1N
cyclohexylamine in methanol to afford two endpoints; the first
endpoint corresponded to all sulfonic acid groups in the sample
plus the first acidic proton of sulfuric acid, and the second
endpoint corresponded to the second acidic proton of sulfuric acid.
In the second titration, the solution was titrated
potentiometrically with 0.14N sodium hydroxide in about 3.5:1
methanol:water to afford three endpoints: The first endpoint
corresponded to all sulfonic acid groups in the sample plus the
first and second acidic proton of sulfuric acid; the second
endpoint corresponded to the carboxylic acid of 2-sulfoisobutyric
acid; and the third endpoint corresponded to isobutyric acid.
[0197] The selective detection the of the second acidic proton of
sulfuric acid in the first titration, together with the selective
detection of the carboxylic acid of 2-sulfoisobutyric acid in the
second titration, allowed for the calculation of acid component
concentrations.
[0198] The degree of sulfonation as described herein and as
determined by .sup.1H-NMR was measured using the following
procedure. About two (2) grams of non-neutralized sulfonated
polymer product solution was treated with several drops of methanol
and the solvent was stripped off by drying in a 50.degree. C.
vacuum oven for approximately 0.5 hours. A 30 mg sample of the
dried polymer was dissolved in about 0.75 mL of
tetrahydrofuran-d.sub.8 (THF-d.sub.8), to which was then added with
a partial drop of concentrated H.sub.2SO.sub.4 to shift interfering
labile proton signals downfield away from aromatic proton signals
in subsequent NMR analysis. The resulting solution was analyzed by
.sup.1H-NMR at about 60.degree. C. The percentage styrene
sulfonation was calculated from the integration of .sup.1H-NMR
signal at about 7.6 part per million (ppm), which corresponded to
one-half of the aromatic protons on sulfonated styrene units; the
signals corresponding to the other half of such aromatic protons
were overlapped with the signals corresponding to non-sulfonated
styrene aromatic protons and tert-butyl styrene aromatic
protons.
[0199] The ion exchange capacity as described herein was determined
by the potentiometric titration method described above and was
reported as milliequivalents of sulfonic acid functionality per
gram of sulfonated block copolymer.
[0200] The formation of micelles was confirmed by particle size
analysis on a Malvern Zetasizer Nano Series dynamic light
scattering instrument, model number ZEN3600, available from Malvern
Instruments Limited, UK, using polymer sample solutions diluted to
a concentration of about 0.5 to 0.6%-wt. with cyclohexane. The
diluted polymer solution samples were placed in a 1 cm acrylic
cuvette and subjected to the instrument's general purpose algorithm
for determination of size distribution as a function of intensity
(see A. S. Yeung and C. W. Frank, Polymer, 31, pages 2089-2100 and
2101-2111 (1990)).
b. Experiments
(I) Preparation of Non-Neutralized Sulfonated Block Copolymer
SBC-1
[0201] A pentablock copolymer having the configuration A-D-B-D-A
was prepared by sequential anionic polymerization where the A
blocks are polymer block of para-tert-butylstyrene (ptBS), the D
blocks were comprised of polymer blocks of hydrogenated isoprene
(Ip), and the B blocks were comprised of polymer blocks of
unsubstituted styrene (S). Anionic polymerization of the
t-butylstyrene in cyclohexane was inititated using sec-butyllithium
affording an A block having a molecular weight of 15,000 g/mol.
Isoprene monomers were then added to afford a second block with a
molecular weight of 9,000 g/mol (ptBS-Ip-Li). Subsequently, styrene
monomer was added to the living (ptBS-Ip-Li) diblock copolymer
solution and was polymerized to obtain a living triblock copolymer
(ptBS-Ip-S-Li). The polymer styrene block was comprised only of
polystyrene and had a molecular weight of 28,000 g/mol. To this
solution was added another aliquot of isoprene monomer to obtain an
isoprene block having a molecular weight of 11,000 g/mol.
Accordingly, this afforded a living tetrablock copolymer structure
(ptBS-Ip-S-Ip-Li). A second aliquot of para-tert butyl styrene
monomer was added, and polymerization thereof was terminated by
adding methanol to obtain a ptBS block having a molecular weight of
about 14,000 g/mol. The ptBS-Ip-S-Ip-ptBS was then hydrogenated
using a standard Co.sup.2+/triethylaluminum method to remove the
C.dbd.C unsaturation in the isoprene portion of the pentablock. The
block polymer was then sulfonated directly (without further
treatment, not oxidizing, washing, nor "finishing") using an
i-butyric anhydride/sulfuric acid reagent. The hydrogenated block
copolymer solution was diluted to about 10% solids by the addition
of heptane (roughly an equal volume of heptane per volume of block
copolymer solution). Sufficient i-butyric anhydride and sulfuric
acid (1/1 (mol/mol)) were added to afford 2.0 meq of sulfonated
polystyrene functionality per g of block copolymer. The sulfonation
reaction was terminated by the addition of ethanol (2 mol
ethanol/mol of i-butyric anhydride). The resulting polymer was
found, by potentiometric titration, to have an "Ion Exchange
Capacity (IEC)" of 2.0 meq of --SO.sub.3H/g of polymer. The
solution of sulfonated polymer had a solids level of about 10%
wt/wt in a mixture of heptane, cyclohexane, and ethyl
i-butyrate.
(II) Neutralization of Micellar Solution with Triethylaluminum
[0202] A 100 g aliquot of the solution obtained in (I) (10 g
polymer, 20 meq of --SO.sub.3H) was diluted with an additional 40 g
of cyclohexane. In an inert atmosphere, triethylaluminum (13.84 g,
20 mmol) was added dropwise to the stirred sulfonated copolymer
solution. An exotherm of 20.degree. C. was observed. The resulting
solution was exposed to the atmosphere.
(III) Neutralization of Micellar Solution with Metal Compounds
[0203] The procedure in (II) was repeated using the following metal
compounds in the following amounts instead of triethylaluminum:
TABLE-US-00001 Metal Solution Polymer Solution Metal Compound
SO.sub.3H/Metal (g) (g) a Triethylaluminum 1 eq./1 eq. 4.19 100 1.0
M in hexanes b sec-Butyllithium 1 eq./1 eq. 11.1 100 1.4 M in
cyclohexane c Diethylzinc 1 mole/1 eq. 14.5 100 1.0 M in hexanes d
Diethylzinc 1 eq./1 eq. 7.26 100 1.0 M in hexanes
(IV) Casting of Membranes
[0204] A 20 mil thick casting of each of the neutralized polymer
solutions obtained in (II), (III.a), (III.b), (III.c), (III.d), and
of the solution obtained in (I) was drawn onto a 16''.times.16''
silicanized glass plate. Each plate was allowed to dry overnight in
a casting chamber at 1 atmosphere, relative humidity of 50%, and
room temperature (about 23.degree. C.) affording membranes that
were a little over one mil thick.
(V) Neutralization of Membranes Made from Sulfonated Block
Copolymer
[0205] The non-neutralized sulfonated block copolymer solution
obtained in (I) was cast into a membrane as described in (IV). This
membrane was cut up into several strips. These strips of film were
separately placed into plastic bags containing an excess of the
following solutions of sodium hydroxide in deionized (D.I.)
water:
TABLE-US-00002 Experiment Concentration of NaOH Identity Solution
(mol/l) a 1.0 b 0.1 c 0.01 d 0.001
[0206] The samples were stored in contact with the NaOH solutions
for a week in the dark. The resulting neutralized membranes were
evaluated using the wet tensile test procedure described above. The
performance properties of these materials are reported below in
Table 2. A control sample was prepared by soaking a sample of the
starting membrane in deionized water for a week. "Dry Tensile"
analyses used samples which had been soaked for a week, rinsed with
deionized water, and dried under vacuum at 50 C.
c) Results and Discussion
[0207] Aluminum neutralized polymer solutions (II and III.a) and
zinc neutralized polymer solutions (III.c and III.d) could be
readily cast into uniform membranes using the same techniques as
for casting a membrane from the solution of the non-neutralized
sulfonated block copolymer (I). The lithium neutralized polymer
solution (III.b) could not readily be cast into uniform membranes
under these conditions. The membranes obtained by casting the
lithium neutralized block copolymer were mottled in appearance and
afforded a bumpy surface.
[0208] The data pertaining to the mechanical properties of
representative membranes are compiled in the following Tables 1
(samples neutralized in micellar solution and then cast into
membranes) and 2 (samples neutralized after membrane
formation):
TABLE-US-00003 TABLE 1 Wet and Dry Tensile Performance for
Membranes Prepared From Neutralization of Micellar Solutions Which
Were Subsequently Cast Into Membranes. Membrane as Stress at Strain
at Strain Stress Identified in Sample Break Break at Yield at Yield
Modulus Sect. I to V Condition.sup.a (psi) (%) (%) (psi) (psi) (I)
Dry 2,400 270 45 1,800 66,000 Control Wet 1,200 260 no yield no
yield 3,100 (II) Dry 1,400 4 3.2 1,200 53,000 1 mol Al Wet 1,200 2
1.5 1,200 94,000 (III.a) Dry 1,700 39 5.9 1,900 46,000 1 eq. Al Wet
830 230 11 480 13,000 (III.b).sup.1 Dry 580 74 4.9 600 20,000 1 eq.
Li Wet 230 60 8.4 170 4,300 (III.b).sup.2 Dry 850 82 5 1,100 37,000
1 eq. Li Wet 600 250 56 260 2,100 (III.c) Dry 1,900 59 4.1 2,500
11,000 1 mol Zn Wet 1,100 260 6 560 25,000 (III.d) Dry 1,200 48 6.1
1,500 48,000 1 eq. Zn Wet 860 250 19.8 440 6,500 (V.a) Dry 1,700 11
10 1,700 36,000 1M NaOH Wet 780 160 35 480 7,500 .sup.aSample
Condition at Time of Tensile Test
TABLE-US-00004 TABLE 2 Wet and Dry Tensile Performance for
Membranes Prepared by Contacting an Already Cast Membrane of
Non-neutralized Sulfonated Block Copolymer With a Solution (0.001
to 1M) of NaOH in Water. Membrane as Identified in Sample Stress at
Strain at Strain at Stress at Sect. I and V Condition.sup.a Break
(psi) Break (%) Yield (%) Yield (psi) Modulus (psi) (I) Dry 1,300
130 7.2 1,400 36,000 Control Wet 560 160 20 230 2,300 D.I. Water
(V.a) Dry 1,700 11 10 1,700 36,000 1M NaOH Wet 780 160 35 480 7,500
(V.b) Dry 1,700 79 11 1,700 34,000 0.1M NaOH Wet 800 160 31 480
7,500 (V.c) Dry 1,700 26 10 1,700 36,000 0.01M NaOH Wet 780 170 78
580 5,400 (V.d) Dry 1,800 24 10 1,800 33,000 0.001M NaOH Wet 580 95
17 400 8,000 .sup.aSample Condition at Time of Tensile Test
[0209] The data compiled in Tables 1 and 2 illustrate the effect of
neutralization on the mechanical properties of the membranes. The
effect was most notable after the membranes had been equilibrated
in water (wet condition). Notably, membrane (II) which was obtained
using 1 mole of aluminum reagent per equivalent of sulfonic acid
functionality in the polymer did not soften on contact with water
(see Table 1). A similar improvement of the mechanical properties,
albeit less pronounced, was observed when the amounts of aluminum
were reduced (III.a) or when zinc was employed instead of aluminum
(III.c and III.d).
[0210] Neutralization of the sulfonated block copolymer with the
monovalent ions Li.sup.+ and Na.sup.+ also had a reinforcing effect
on the membranes in the presence of water; albeit to a lesser
extent. Unlike the control membrane (I), the membranes cast from
solutions that had been neutralized with Li.sup.+ had a well
defined yield event at low elongation in the wet tensile test.
These materials were higher in modulus when wet than was the
control membrane. However, the membranes modified with Li.sup.+ and
Na.sup.+ ions were less resistant to water than the membranes which
had been obtained from sulfonated block copolymers that had been
neutralized with the multivalent ions. Nonetheless, the monovalent
ion neutralized materials gave better mechanical performance in
water than did the control membrane (I).
[0211] It was found that membranes cast from the sulfonated block
copolymer in the non-neutralized sulfonic acid form increased
significantly in weight when immersed in water; this increase in
weight was taken as a measure of swelling in the presence of water.
Moreover, the increase in weight was found to be directly related
to an increase in the dimension of the membrane, i.e., membranes
obtained from the non-neutralized sulfonated block copolymers
exhibit a tendency to swell under the influence of water. In
contrast thereto and surprisingly, the membranes obtained from the
sulfonated block copolymers which had been neutralized with a metal
compound wherein the metal has an atom number of at least 11
exhibited considerably less swelling when equilibrated with water
and, based upon that result, had improved dimensional stability, as
well.
[0212] The aluminum and zinc neutralized membranes (II, III.a,
III.c and III.d) surprisingly exhibited superior dimensional
stability. These membranes took up about 30% of their weight in
water at equilibrium when immersed in water. However, within the
errors of the measurement, the dimensions of these membranes were
the same under both wet and dry conditions, i.e., the respective
membranes did not undergo a change in volume upon repeated wet/dry
cycling.
[0213] The lithium neutralized membranes (III.b) were clearly
inferior in this test. Also, as noted above, the lithium
neutralized sulfonated block copolymers did not afford membranes
that were uniform in appearance, and the membranes were weak in the
tensile test.
[0214] The data pertaining to the water uptake and water vapor
transport properties of representative membranes are compiled in
the following Tables 3 and 4:
TABLE-US-00005 TABLE 3 Water Vapor Transport Rates and Swelling
Data for Membranes Prepared From Neutralization of Micellar
Solutions Which Were Subsequently Cast Into Membranes. Membrane as
Identified in WVTR Swelling Sect. I to V (g/m.sup.2/day/mil) (%
uptake) (I) Control 24,000 140 (II) 1 mol Al 22,000 29 (III.a) 1
eq. Al 22,000 32 (III.b).sup.1 1 eq. Li 28,000 190 (III.b).sup.2 1
eq. Li 22,500 230 (III.c) 1 mol Zn n.d. 8 (III.d) 1 eq. Zn n.d. 30
n.d. = not determined
TABLE-US-00006 TABLE 4 Water Vapor Transport Rates and Swelling
Data for Membranes Prepared by Contacting an Already Cast Membrane
of Non-neutralized Sulfonated Block Copolymer With a Solution
(0.001 to 1M) of NaOH in Water Membrane as Identified WVTR Swelling
in Sect. I and V (g/m.sup.2/day/mil) (% uptake) (I) Control 24,000
140 (V.a) 1M NaOH 25,000 23 (V.b) 0.1M NaOH 22,000 42 (V.c) 0.01M
NaOH 27,000 49 (V.d) 0.001M NaOH 30,000 52
[0215] A particularly useful property of the sulfonated block
copolymers which serve as the starting material for the
neutralization reaction is that they may be cast into membranes
which are capable of transporting water at a high rate while
rejecting the transport of other chemicals. Transport rates in
excess of 20 liters of water per m.sup.2 of surface area per day
have been observed for membranes of about 1 mil thickness. This is
one of the desirable performance characteristics for these
materials.
[0216] Surprisingly, it has been found that the metal neutralized
sulfonated block copolymers afforded membranes which were equally
effective in transporting water (see Table 3). The high rate at
which water is transported through the membranes requires that the
membranes possess a continuous phase allowing for water transport.
As the membranes were cast from a solution in which the ion
containing phase was not continuous but was of a spherical micellar
structure and therefore, if necessity dispersed, it was surprising
that membranes were formed which allowed for the water to move from
one surface of the membrane to the other.
[0217] Additionally and also surprisingly, the membranes cast from
solutions that had been neutralized with multivalent ions were
capable of transporting high amounts of water without exhibiting
significant swelling of the ion containing phase (see Table 3). In
the case of the control polymer (I), high water flow rates through
the membrane were accompanied by substantial swelling on contact
with water.
[0218] As shown by the data set forth in Table 3, the membranes
cast from sulfonated block copolymers which had been neutralized by
Li.sup.+ ions exhibited excessive swelling. Neutralizing the
already cast membrane with an aqueous solution of sodium hydroxide
yielded improved dimensional stability as compared with the control
membrane (I).
* * * * *