U.S. patent application number 14/316116 was filed with the patent office on 2015-12-31 for rotary enthalpy exchange wheel having sulfonated block copolymer.
This patent application is currently assigned to KRATON POLYMERS U.S. LLC. The applicant listed for this patent is KRATON POLYMERS U.S. LLC. Invention is credited to Steven Huynh, Kuitian Tan.
Application Number | 20150375199 14/316116 |
Document ID | / |
Family ID | 54847862 |
Filed Date | 2015-12-31 |
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United States Patent
Application |
20150375199 |
Kind Code |
A1 |
Tan; Kuitian ; et
al. |
December 31, 2015 |
Rotary Enthalpy Exchange Wheel Having Sulfonated Block
Copolymer
Abstract
A rotary enthalpy exchange wheel having a rotatable wheel with
air passageways extending from a front side to a back side for
passing air streams therethrough. The wheel has a rigid substrate
which is coated or laminated with a desiccant composition having a
sulfonated block copolymer. The sulfonated block copolymer has 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 percent sulfonic acid or
sulfonate ester functional groups based on the number of monomer
units.
Inventors: |
Tan; Kuitian; (Katy, TX)
; Huynh; Steven; (Katy, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KRATON POLYMERS U.S. LLC |
Houston |
TX |
US |
|
|
Assignee: |
KRATON POLYMERS U.S. LLC
Houston
TX
|
Family ID: |
54847862 |
Appl. No.: |
14/316116 |
Filed: |
June 26, 2014 |
Current U.S.
Class: |
96/11 ;
502/402 |
Current CPC
Class: |
B01D 53/261 20130101;
B01J 20/28035 20130101; B01D 53/0407 20130101; B01D 2253/108
20130101; B01D 53/02 20130101; B01D 2253/25 20130101; B01J 20/264
20130101; B01D 2253/202 20130101; B01J 20/103 20130101; B01D
2259/40088 20130101 |
International
Class: |
B01J 20/26 20060101
B01J020/26; B01D 71/80 20060101 B01D071/80; B01J 20/28 20060101
B01J020/28; B01D 53/22 20060101 B01D053/22; B01D 53/02 20060101
B01D053/02; B01J 20/10 20060101 B01J020/10; B01D 69/10 20060101
B01D069/10; B01D 71/66 20060101 B01D071/66 |
Claims
1. A rotary enthalpy exchange wheel comprising: a rotatable wheel
having air passageways extending from a front side to a back side
for passing air streams therethrough, said wheel comprising a rigid
plastic substrate, the rigid plastic substrate coated or laminated
with a desiccant composition comprising a sulfonated block
copolymer, wherein the sulfonated block copolymer has 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 percent sulfonic acid or sulfonate ester
functional groups based on the number of monomer units.
2. The rotary enthalpy exchange wheel of claim 1, wherein the
desiccant composition is laminated on the substrate.
3. The rotary enthalpy exchange wheel of claim 1, wherein the
desiccant composition is adhesively laminated on the substrate.
4. The rotary enthalpy exchange wheel of claim 3, wherein the water
uptake of the desiccant composition increases at least 20% when the
relative humidity is changed from 20% and 80%.
5. The rotary enthalpy exchange wheel of claim 3, wherein the water
uptake of the desiccant composition as a result of water sorption
is at least 30% when the relative humidity of an air stream has a
relative humidity above 80%.
6. The rotary enthalpy exchange wheel of claim 1, wherein the wheel
is substantially circular having a plurality of separated sections,
wherein the passageways are oriented to permit air stream flow in
opposite directions between at least two of the sections without
substantial intermixture.
7. The rotary enthalpy exchange wheel of claim 1, wherein the rigid
plastic forms a matrix within the rotatable wheel.
8. The rotary enthalpy exchange wheel of claim 1, wherein the wheel
rotates about a hub.
9. The rotary enthalpy exchange wheel of claim 1, wherein the
plastic substrate is made up of polystyrene, polyethylene,
polypropylene, polyester, nylon, or a mixture thereof.
10. The rotary enthalpy exchange wheel of claim 1, where the
desiccant composition further comprises a desiccant other than a
sulfonated block copolymer.
11. The rotary enthalpy exchange wheel of claim 1, where the
sulfonated block copolymer is the sole desiccant in the desiccant
composition.
12. A rotary enthalpy exchange wheel comprising: a rotatable wheel
having air passageways extending from a front side to a back side
for passing air streams therethrough, said wheel comprising a rigid
substrate, the rigid substrate coated or laminated with a desiccant
composition comprising a sulfonated block copolymer and a second
desiccant other than a sulfonated block copolymer, wherein the
sulfonated block copolymer has 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 percent sulfonic acid or sulfonate ester functional
groups based on the number of monomer units.
13. The rotary enthalpy exchange wheel of claim 12, wherein the
second desiccant is selected from zeolites, molecular sieves,
silica gel, lithium chloride, or a mixture thereof.
14. The rotary enthalpy exchange wheel of claim 13, wherein the
second desiccant is silica gel.
15. The rotary enthalpy exchange wheel of claim 12, wherein the
second desiccant is an inorganic desiccant.
16. The rotary enthalpy exchange wheel of claim 12, wherein the
rigid substrate comprises a metal, a plastic, or a composite
material.
17. The rotary enthalpy exchange wheel of claim 12, wherein the
rigid substrate is aluminum.
18. The rotary enthalpy exchange wheel of claim 12, wherein the
desiccant composition is laminated on the substrate.
19. The rotary enthalpy exchange wheel of claim 12, wherein the
desiccant composition is adhesively laminated on the substrate.
20. The rotary enthalpy exchange wheel of claim 12, wherein the
water uptake of the desiccant composition increases at least 10%
when the relative humidity is changed from 20% and 80%.
21. The rotary enthalpy exchange wheel of claim 12, wherein the
water uptake of the desiccant composition is at least 19% when the
relative humidity of an air stream has a relative humidity at 80%
and above.
22. The rotary enthalpy exchange wheel of claim 12, wherein the
wheel is substantially circular having a plurality of separated
sections, wherein the passageways are oriented to permit air stream
flow in opposite directions between at least two of the sections
without substantial intermixture.
23. The rotary enthalpy exchange wheel of claim 12, wherein the
rigid substrate is plastic.
24. The rotary enthalpy exchange wheel of claim 12, wherein the
wheel rotates about a hub.
25. The rotary enthalpy exchange wheel of claim 12, wherein the
plastic substrate is made up of polystyrene, polyethylene,
polypropylene, polyester, nylon, or a mixture thereof.
26. A desiccant composition for a rotary enthalpy exchange wheel
exchanger comprising: a sulfonated block copolymer comprising 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 percent sulfonic acid or
sulfonate ester functional groups based on the number of monomer
units, the sulfonated block copolymer mixed with a second desiccant
different from said sulfonated block copolymer.
27. The desiccant composition of claim 26, wherein the second
desiccant is selected from zeolites, molecular sieves, silica gel,
lithium chloride, or a mixture of such.
28. The desiccant composition of claim 27, wherein the second
desiccant is silica gel.
29. The desiccant composition of claim 26, wherein the second
desiccant is an inorganic desiccant.
30. The desiccant composition of claim 26, wherein the second
desiccant is an organic desiccant.
31. A rotary enthalpy exchange wheel comprising: a rotatable wheel
having air passageways extending from a front side to a back side
for passing air streams therethrough, said wheel comprising a metal
substrate, the metal substrate coated or laminated with a
sulfonated block copolymer and a desiccant other than a sulfonated
block copolymer, wherein the sulfonated block copolymer has 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 percent sulfonic acid or
sulfonate ester functional groups based on the number of monomer
units.
32. The rotary enthalpy exchange wheel of claim 31, wherein the
metal substrate is aluminum.
Description
FIELD OF THE INVENTION
[0001] The present disclosure relates to rotary enthalpy exchange
wheels. In particular, the present disclosure is directed to rotary
exchange wheels having a plastic or aluminum substrate bonded with
a desiccant or desiccants mixture which comprises or consists of a
sulfonated block copolymer. The sulfonated block copolymer has at
least two polymer end blocks that contain little or no sulfonic
acid or sulfonate functionality and at least one polymer interior
block which contains an effective amount of sulfonic acid or
sulfonate functionality. The sulfonated block copolymer can be
admixed with other desiccants.
BACKGROUND OF THE INVENTION
[0002] Heating, ventilating, and air conditioning (HVAC) systems
have been employed in residential, commercial, and industrial
building and structures to help control the indoor environment,
conserve energy and to maintain healthy and comfortable conditions.
One system that has been employed is rotary enthalpy exchange
wheels. In such a system, indoor and outdoor air streams are fed to
an enthalpy wheel to exchange heat and/or moisture between such air
streams without substantial intermixture. Rotary enthalpy wheels
exchange both sensible and/or latent heat between air streams in an
effort to conserve energy. The transmission of sensible energy
involves a change in temperature, whereas latent energy involves
the change in energy during a phase transition of a substance. In
the context of rotary exchange wheels, latent heat exchange is
represented by a change in moisture content between air
streams.
[0003] A significant portion of energy cost savings can involve the
conservation of latent energy. Accordingly, improving the
efficiency and effectiveness of latent energy exchange can have a
significant impact on improving energy conservation. Rotary
enthalpy exchange wheels have generally been employed in large
industrial settings due to their ability to handle large airflows.
Such systems generally involve a central rotatable wheel having a
core capable of receiving cross flowing air streams.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Implementations of the present technology will now be
described, by way of example only, with reference to the attached
figures, wherein:
[0005] FIG. 1 is a perspective view of one embodiment of a rotary
enthalpy exchange wheel;
[0006] FIG. 2 is a side view illustration of air streams passing
through rotary enthalpy exchange wheel;
[0007] FIG. 3A is a sectional view of one embodiment of a moisture
adsorbing matrix for a rotary enthalpy exchange wheel;
[0008] FIG. 3B is a sectional view of one embodiment of a moisture
adsorbing matrix for a rotary enthalpy exchange wheel;
[0009] FIG. 4 is an isotherm graph illustrating water uptake as a
function of relative humidity samples bonded to an aluminum
substrate;
[0010] FIG. 5 is an isotherm graph illustrating water uptake as a
function of relative humidity samples bonded to a plastic
substrate;
[0011] FIG. 6A is an scanning electron microscope (SEM) image of a
desiccant silica gel, SG-1 (defined further below), coated on
oriented polystyrene substrate;
[0012] FIG. 6B is an scanning electron microscope (SEM) image of a
desiccant silica gel, SG-2 (defined further below), coated on an
aluminum substrate;
[0013] FIG. 6C is an scanning electron microscope (SEM) image of a
molecular sieve desiccant coated on an aluminum substrate;
[0014] FIG. 6D is an scanning electron microscope (SEM) image of a
desiccant mixture made up of a sulfonated block copolymer and
silica gel, SBC-1/SG-1 (defined further below) coated on oriented
polystyrene.
DETAILED DESCRIPTION OF THE INVENTION
[0015] A detailed description of embodiments of the present
disclosure is provided herein; however, it is to be understood that
the disclosed embodiments are merely exemplary, and that the
disclosure may be embodied in various and alternative forms.
Therefore, specific structural and functional details which are
addressed in the embodiments disclosed 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
employ the present disclosure.
[0016] 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.
[0017] Unless specifically stated otherwise, all technical terms
used herein have the meaning as commonly understood by those
skilled in the art.
[0018] Moreover, unless specifically stated otherwise, the
following expressions as used herein are understood to have the
following meanings.
[0019] Unless specifically stated otherwise, the expression
"coated" or "coating" means the application or bonding of a
polymer, in solution or liquid form, to a substrate or other
material.
[0020] In contrast to "coated," unless specifically stated
otherwise, the expression "lamination" means the application or
bonding of a cast polymer membrane or polymer film to a substrate
or other material.
[0021] The term "bonded," or "bonding" encompasses attachment of a
polymer to a substrate or other material either by coating or
lamination or other means, whereby a bond is formed between a
polymer membrane and the substrate or other material.
[0022] The expression "water uptake" as used herein refers to the
weight of water which is adsorbed by a desiccant, membrane or block
copolymer as compared to the original weight of the dry material
and is calculated as a percentage.
[0023] It will be understood by those skilled in the art that the
term "film" herein may also be referred to as a membrane which may
be moisture permeable but air impermeable.
[0024] The present disclosure relates to a rotary enthalpy exchange
wheel which includes a rotatable wheel having air passageways
extending from a front side to a back side for passing air streams
therethrough. The wheel has a rigid plastic, metal, composite
substrate or other substrate material. The rigid substrate is
coated or laminated with a desiccant composition comprising a
sulfonated block copolymer. The sulfonated block copolymer has 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 percent sulfonic acid or
sulfonate ester functional groups based on the number of monomer
units.
[0025] In some embodiments, the desiccant composition is made up
solely of the sulfonated block copolymer, or alternatively includes
the sulfonated block copolymer as the sole desiccant. In other
embodiments, the desiccant composition is a mixture of the
sulfonated block copolymer and an additional desiccant, for example
desiccants other than the sulfonated block copolymer such as other
polymeric desiccants, organic desiccants, inorganic desiccants,
zeolites, molecular sieves, or silica gel. When the composition is
a mixture of more than one desiccant, the composition can be mixed
in solution form prior to coating or lamination or otherwise formed
into a membrane.
[0026] The rotary enthalpy wheel disclosed herein, employing the
desiccant composition comprising the sulfonated block copolymer,
demonstrates unexpected and advantageous results for enthalpy
exchange between air streams in an enthalpy wheel exchange system.
In particular, the desiccant composition comprising the sulfonated
block copolymer is capable of rapidly adsorbing and desorbing
moisture or water vapor from air.
[0027] For example, the desiccant composition disclosed herein can
adsorb a larger amount of water in a shorter amount of time than
conventional desiccants. This permits greater exchange of moisture
between air streams passing through a rotary enthalpy exchange
wheel. The desiccant composition can be bonded, via coating or
lamination, to a variety of substrates including metal, aluminum,
plastic, or a composite plastic material such as fiberglass.
[0028] Exemplary Rotary Exchange Wheel Structure.
[0029] An exemplary rotary enthalpy exchange wheel 100 is
illustrated for example in FIG. 1. As shown therein is a support
frame 110 which contains and provides support for wheel 120
therein. The frame 110 can be made up of any strong rigid material
such as aluminum or steel, or a strong plastic. The frame 110
supports the wheel 120 without interfering with the rotation
therein. The wheel 120 can also be supported on a hub 130. The hub
130 can provide a point around which the wheel 120 rotates. The hub
130 can include a rod extending through the center of the wheel 120
to support and rotate the wheel 120. The hub 130 can be powered to
rotate the wheel 120 with any type of motor for providing torque,
for example electric motors.
[0030] The wheel 120 is made up of or contains a moisture adsorbing
matrix 140. The illustrated wheel 120 can have a circular shape,
but additionally, can take any other shape as well, for example,
square or rectangular, pentagonal, hexagonal, heptagonal,
octagonal, or any other number of sides in a polygon, or take any
other shape. The wheel 120 can itself have an outer rim 150 to
provide support frame portion on its outer circumferential surface
and can be made up of the same material as frame 110. In other
embodiments no outer rim 150 is present. When present however,
wheel frame members 160 can extend from the center to the outer rim
150 of the wheel or to frame 110.
[0031] The wheel 120 moisture adsorbing/desorbing matrix 140 has a
front side face 170 and a back side face 180 opposite front face
170. The moisture adsorbing matrix 140 has passageways extending
from the front side face 170 to the back side face. The passageways
permit air streams to pass through the wheel 120 from one face to
the other. For example, exiting air stream 190 can be passed
through the top portion of the wheel 120 while the entering air
stream 195 can pass through the bottom portion. For example, as
shown in FIG. 2, there can be an exit vent system 210 providing the
exiting air stream 190 and an entrance vent system 220 for
providing the entering air stream 195. As rotary exchange units can
be employed with buildings or enclosures, generally, the exiting
air stream will be warmer and have higher moisture content, while
the entering air stream will be cooler and at lower moisture
content. With rotation of the wheel 120, the moisture adsorbing
matrix 140 can, for example, sorb moisture from the exiting air
stream 190, and release such moisture in the entering air stream
195. By exchanging moisture and heat between air streams, energy
can be conserved by increasing the temperature and moisture of the
incoming airstream. In other embodiments, the reverse can be true,
the entering air stream is warmer with higher moisture content, and
the exiting air is cooler with lower moisture content.
[0032] In FIG. 1, the moisture adsorbing matrix 140 is made up of a
substrate with a desiccant composition made up solely of a
sulfonated block copolymer, or sulfonated block copolymer as the
sole desiccant, or a mixture of the sulfonated block copolymer and
another desiccant other than the sulfonated block copolymer.
Accordingly, the substrate provides the mechanical strength as well
as the surface for bonding of the desiccant composition
thereon.
[0033] A shown in FIGS. 3A and 3B, the moisture adsorbing matrix
140 can have a corrugated shape. For example, in FIG. 3A, there can
be horizontal layers 310 with wave layers 320. Air streams can pass
through the air passages 330 of wheel 120, passing from the front
face and out the back face. By corrugating the layers greater
surface area of the moisture adsorbing matrix 140 can be exposed to
the air streams and therefore provide greater area for adsorption
and desorption. Another triangular configuration is shown for
example in FIG. 3B.
[0034] The moisture adsorbing material of wheel 120 can be made up
of a substrate 340 which provides mechanical strength and rigidity.
A desiccant composition 350 is bonded to the substrate 340 for
example by coating or lamination. The desiccant composition 350 can
be layered across the entire exposed substrate 340 surface, on both
sides of the wave layers 320 or horizontal layers 310.
[0035] As will be further described below, the substrate can be
made up of a variety of materials, including metal and or plastic.
The substrate is predominantly rigid and maintains shape in a
variety of temperatures and humidities. In some embodiments, the
substrate is made up of metal such as aluminum, or a metal alloy
having aluminum. In other embodiments, other metals can be used
such as steel, stainless steel, copper, tin, and gold.
[0036] The substrate can also be made up of a plastic such as
polystyrene (PS), polyethylene (PE), polypropylene (PP), polyvinyl
chloride (PVC), carbon, fiberglass, cellulose, cellulose nitrate,
cellulose acetate, nylon, polytetrafluoroethylene, Nomex.RTM.,
Kevlar.RTM. or a mixture or composite of such materials.
[0037] Desiccants
[0038] The desiccant composition can be made up solely of a
sulfonated block copolymer, or alternatively with the sulfonated
block copolymer as the sole desiccant, or a mixture of the
sulfonated block copolymer and desiccants other than the sulfonated
block copolymer. The sulfonated block copolymers have advantageous
properties such as rapid adsorption and de-sorption of moisture
from air streams. The sulfonated block copolymer can also have
higher water uptake values than conventional rotary wheel moisture
adsorbent materials. Generally, with higher water uptake values,
dimensional stability can be impaired. However, by providing the
sulfonated block copolymer on a substrate, mechanical strength is
provided by the substrate thus resolving problems related to
dimensional stability. As a result, higher sulfonation levels can
be employed with less concern for dimensional stability, thereby
providing higher water uptake values. As a consequence, rapid
transfer of high amounts of moisture between air streams achieved
relative conventional materials.
[0039] In some embodiments, the compositions of the present
disclosure include the sulfonated block copolymers described in
U.S. Pat. No. 7,737,224 to Willis et al. Furthermore, the
sulfonated block copolymers, including those described in U.S. Pat.
No. 7,737,224, may be prepared according to the process of WO
2008/089332 to Dado et al. or the process of U.S. Pat. No.
8,012,539 to Handlin, Jr. et al.
[0040] In preparation of the sulfonated block copolymers herein,
initially the block copolymer is formed, then subjected to
sulfonation. The sulfonated block copolymers can then be coated
onto the substrate for the rotary wheel, or cast to membrane and
laminated to a substrate.
[0041] Sulfonated Block Copolymers
[0042] The block copolymers needed to prepare the sulfonated block
copolymers 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.
[0043] 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.
[0044] 1. Polymer Structure
[0045] In one embodiment, the block copolymers have at least two
polymer ends 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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, hexene or octene, 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.
[0052] 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.
[0053] 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.
[0054] 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. 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).
[0055] 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).
[0056] 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 mole percentages even if the specific
combination and range is not listed herewith.
[0057] The B blocks, in each case, comprise 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 partially or
completely 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 partially or completely hydrogenated dienes
may be random copolymers, tapered copolymers, block copolymers or
controlled distribution copolymers. In one preferred embodiment,
the B blocks are selectively partially or completely 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 U.S.
Pat. No. 7,169,848, which disclosure is herein incorporated by
reference. U.S. Pat. No. 7,169,848 also discloses the preparation
of sulfonated block copolymers. 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.
[0058] In another aspect of the present disclosure, the block
copolymer includes at least one impact modifier block D having a
glass transition temperature less than 20.degree. C. The D block is
not crystalline, but is instead semi-crystalline or amorphous.
Accordingly, while the A block provides a "hard" phase, the D block
provides a "softer" block thereby adding a more elastomeric
segment. Accordingly, 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 is a polymer block of isobutylene
having a number average molecular weight of 1,000 to 50,000.
[0059] 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.
[0060] 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 mole percentages even if the
specific combination is not listed herewith.
[0061] 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 mole percentages even if the specific combination and
range is not listed herewith.
[0062] 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 mole percentages 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.
[0063] 2. Overall Anionic Process to Prepare Polymers
[0064] 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.
[0065] Starting materials for preparing the block copolymers of the
present disclosure include the initial monomers noted above. Other
important starting materials for anionic copolymerizations include
one or more polymerization initiators. In the present disclosure
suitable initiators 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 U.S.
Re. 27,145, the disclosure of each of which is incorporated herein
by reference.
[0066] Polymerization conditions to prepare the block copolymers of
the present disclosure 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 or argon, 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.
[0067] 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
[0068] 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.
[0069] 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.
[0070] 3. Process to Prepare Hydrogenated Block Copolymers
[0071] 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.
[0072] 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 U.S. 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.
[0073] Hydrogenation can be carried out under such conditions that
at least about 90% of the conjugated diene double bonds are
reduced, and between zero and 10% of the arene double bonds are
reduced. Preferred ranges are at least about 95% of the conjugated
diene double bonds reduced, and more preferably about 98% of the
conjugated diene double bonds are reduced.
[0074] 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 formation of an explosive mixture of oxygen and
hydrocarbons.
[0075] 4. Process to Make Sulfonated Polymers
[0076] According to the multiple embodiments disclosed herein, the
above prepared block copolymers are sulfonated to obtain a
sulfonated polymer product that is in solution. The block
copolymers can be provided in particular organic solvents so as to
form micelles prior or subsequent sulfonation.
[0077] 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.
[0078] 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.
[0079] 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 U.S. Pat. No. 7,737,224.
[0080] 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.
[0081] (i) Solvent
[0082] 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.
[0083] 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.
[0084] The pre-formed polymer micelles and/or other polymer
aggregates allow the sulfonation of the polymer to proceed
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.
[0085] (ii) Polymer Concentration
[0086] 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.
[0087] 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 mole
percentages even if the specific combination and range is not
listed herewith.
[0088] 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 %-wt. even if the specific
combination and range is not listed herewith.
[0089] 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.
[0090] 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.
[0091] (iii) Sulfonation Agent
[0092] 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.
[0093] The formation of acyl sulfate from a carboxylic anhydride
and sulfuric acid can be represented by the following reaction:
##STR00001##
Acyl sulfates are subject to slow decomposition during the course
of sulfonation reactions forming alpha-sulfonated carboxylic acids
of the following formula:
##STR00002##
[0094] 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.
[0095] 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.
[0096] 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.
[0097] The sulfonation of polymer styrenic repeat units with the
acyl sulfate can be represented by the following reaction:
##STR00003##
[0098] 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.
[0099] 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 mole percentage 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 mole percentages even if
the specific combination and range is not listed herewith.
[0100] 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 acid by-products are
preferably ensured.
[0101] 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 complexing/reacting sulfur
trioxides and 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 phosphorous pentoxide, polyphosphoric acid,
1,4-dioxane, triethylamine, etc.
[0102] (iv) Reaction Conditions
[0103] 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 hour to about 2 hours, alternatively
about 1 hour 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.
[0104] 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.
[0105] 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.
[0106] 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.
[0107] (v) Film or Membrane Casting
[0108] Once the sulfonation reaction is completed, the block
copolymers can be cast directly into a membrane without the
necessity of isolating the block copolymer.
[0109] Conventional methods may be used for casting the polymer to
form a film. One method used may be referred to as solution
casting. According to this procedure, the sulfonated copolymer
solution obtained from the sulfonation reaction as described above
may be poured onto an inert substrate such as a siliconized glass
plate. Excess solution can be removed with a glass rod. The
remaining solution is then allowed to dry completely until the
solvent has been evaporated thereby leaving a cast film of the
sulfonated copolymer.
[0110] Alternatively to casting, the sulfonated block copolymer can
be worked up to separate the sulfonated block copolymer from the
reaction mixture and formed into particles or pellets. Such a
process for separating the sulfonated block copolymer from the
reaction solvent and other impurities is disclosed for example in
U.S. application Ser. No. 14/048,522, filed Oct. 8, 2013, to Kraton
Polymers U.S. LLC, which is incorporated herein by reference.
[0111] Desiccants Other than the Sulfonated Block Copolymer
[0112] Desiccants other than the sulfonated block copolymer can be
employed and admixed with the sulfonated block copolymer to form a
desiccant composition. Desiccants include hygroscopic materials
capable of adsorbing water from the air either by absorption,
adsorption or other mechanisms. Desiccants include for example
inorganic desiccants, organic, polymeric, molecular sieves,
zeolites, as well as other materials including, silica gel,
activated alumina, activated carbon, calcium chloride, zinc
chloride, and lithium chloride.
[0113] Molecular sieves are microporous crystalline materials
interlaced with regularly spaced channels of molecular dimensions.
The pore channels permit adsorption or entrance of molecules
smaller than the pore sizes. In some examples, molecular sieves can
have pore sizes from 1 to 50 angstrom (.ANG.), or from 3 to 10
.ANG. (or, 13X). Molecular sieves are capable of capturing water
molecules into its pores and thereby acting as a desiccant for use
in a rotary enthalpy exchange wheel.
[0114] One type of molecular sieve includes zeolites. Zeolites are
hydrated silicates of aluminum and sodium, potassium, and/or
calcium forming three dimensional structures. Such zeolites can
have, for example, the formula
Na.sub.2--Al.sub.2O.sub.3.xSiO.sub.2.yH.sub.2O, where x and y are
any number value. Zeolites can be natural or synthetic. Naturally
occurring zeolites include chabazite, clinoptilolite, thomosonite,
heulandite, faujasite, permutite, analcite, erionite, natrolite,
stilbite, phillipsite and mordenite. Natural zeolites which have a
sufficiently narrow pore size distribution to act as a molecular
sieve can be employed. Synthetic zeolites known in the art can be
employed herein, as well as newly developed zeolites. Synthetic
zeolites can include zeolites A, D, L, R, S, T, X and Y for
example, with types A and X being commonly commercially available.
The zeolites can have a majority of the pore sizes of about 2 to 10
.ANG., or 3 to 8 .ANG., 4 to 5 .ANG., or different combinations of
such pore sizes can employed. The zeolite pore size is sized to
receive water molecules therein. Additionally, the zeolite can have
greater capacity to preferentially adsorb polar molecules.
[0115] Silica gel can also be used as a desiccant for adsorbing
moisture from air streams. Silica gel has a high surface area and
can have pore sizes from 5 to 3000 .ANG.. In some embodiments, the
silica gel can have a narrower pore size distribution, for example
from 5 to 60 .ANG., alternatively, 5 to 30 .ANG., alternatively 5
to 20 .ANG., or different combinations of such pore sizes can be
employed. Silica gel can be provided as a pellet, powder or
granulized form, and can be natural or synthetically produced.
[0116] Other adsorbing materials can also be employed. For example
as mentioned, carbon or alumina can be employed, including
activated carbon and activated alumina. These are not particularly
limited except that they are capable of sorbing and desorbing water
from air streams.
[0117] Mixture of Sulfonated Block Copolymer with Other
Desiccants
[0118] The sulfonated block copolymer described herein can be
blended with the other desiccants noted above to form a desiccant
composition. The desiccants can be added to the sulfonated block
copolymer prior to casting. For example, the desiccants can be
added to the sulfonated block copolymer in its original sulfonation
reaction solution. Alternatively, the sulfonated block copolymer if
in solid form can be re-dissolved by applying the same solvents as
those used in the sulfonated reaction solution. These include for
example cyclohexane, methylcyclohexane, and heptane. Additional
suitable additives known to those skilled in the art can be
included in the desiccants composition which include but are not
limited to, pore clearing agents, pH adjusting agents, surfactants,
antifungal and/or antibacterial agents, hydrothermal stabilizers,
flame retardants, smoke suppressants.
[0119] For example, the sulfonated block copolymer after
sulfonation can be kept in the sulfonation reaction solution, and
stored or shipped until admixed with other desiccants.
Alternatively, the sulfonated block copolymer can be cast, or
separated from its reaction solvent and formed into particle or
pellets and re-dissolved in one or more of the aforementioned
reaction solvents. The desiccants can be added to the sulfonated
block copolymer solution to form a dispersion or colloid. The
desiccants can be added in the form of a powder, granule, particle,
or other solid form.
[0120] The desiccants can be added to the solution measured
relative to the weight of the solution, for example, in some
aspects, the desiccants can be added from at least 10%-wt.,
alternatively at least 25%-wt., alternatively at least 50%-wt.,
alternatively at least 100%-wt., alternatively at least 150%-wt.,
alternatively at least 200%-wt., alternatively at least 250%-wt.,
alternatively at least 300%-wt., alternatively at least 350%-wt.,
alternatively at least 400%-wt., alternatively at least 450%-wt.,
alternatively at least 460%-wt., alternatively at least 500%-wt.,
alternatively at least 550%-wt., or alternatively at least
600%-wt.
[0121] In other examples, the other desiccants can be added to the
sulfonated block copolymer solution from 1%-wt. to 600%-wt.,
alternatively from 1%-wt. to 500%-wt., or alternatively from 1%-wt.
to 460%-wt. or alternatively from 1%-wt. to 450%-wt., alternatively
from 1%-wt. to 450%-wt., alternatively from 1%-wt. to 400%-wt. In
other embodiments, the desiccants can be added from 5%-wt. to
600%-wt., alternatively from 10%-wt. to 600%-wt., alternatively,
alternatively from 50%-wt. to 600%-wt., alternatively from 100%-wt.
to 600%-wt., alternatively from 150%-wt. to 600%-wt., alternatively
from 200%-wt. to 600%-wt. alternatively from 250%-wt. to 600%-wt.,
alternatively from 300%-wt. to 600%-wt., alternatively from
350%-wt. to 600%-wt., alternatively from 400%-wt. to 600%-wt.,
alternatively from 450%-wt. to 600%-wt., alternatively from
500%-wt. to 600%-wt., alternatively from 550%-wt. to 600%-wt. In
other examples, the desiccants can be added to the sulfonated block
copolymer solution from 1%-wt. to 600%-wt., alternatively from
50%-wt. to 550%-wt., alternatively from 100%-wt. to 500%-wt.,
alternatively from 150%-wt. to 450%-wt., alternatively from
200%-wt. to 400%-wt. It will be understood that any combination of
the aforementioned ranges can be employed. The desiccant can be
added in a low enough amount as to permit formation of a film or
membrane upon casting.
[0122] The desiccants can be stirred in until evenly dispersed
throughout the media. The mixing can be conducted at room
temperature and atmosphere. A fraction of the desiccants may
dissolve or a substantial portion or all may dissolve depending on
the type of desiccant and solvent. For example, if solvent is one
which solvates the desiccant then the desiccant may dissolve
therein.
[0123] In one example silica gel can be added to a sulfonated block
copolymer solution. The solution can comprise cyclohexane and
sulfonated block copolymer up from 1%-wt. to about 30%-wt. The
silica gel can be added up to from 200%-wt. to 500%-wt. of the
solution for example.
[0124] The drawbacks of desiccants other than sulfonated block
copolymers have been the presence of odor, or the occurrence of
dust. The production of dust can result in health issues and
furthermore odor can affect the commercial viability. However,
surprisingly, when these desiccants are added to the sulfonated
block copolymer, odor and dust is reduced or removed, thereby
resulting in an advantageous desiccant composition.
[0125] After addition of the desiccant to the sulfonated block
copolymer solution, the solution can be cast to a membrane or
coated onto a substrate.
[0126] Bonding to Substrate
[0127] The manner in which the desiccant composition disclosed
herein is bonded to the substrate depends on the composition and
nature of the substrate. In some examples, the desiccant
composition disclosed herein can be bonded to plastics and
non-metal materials as substrates. With such materials, bonding can
be carried out by coating or laminating the substrate with the
desiccant composition. Lamination can be carried out by a variety
of methods including, thermal, adhesive, solvent, or water
lamination. Coating can be carried out optionally with the addition
of binders or adhesives to assist bonding. The substrates can be
porous or non-porous.
[0128] Lamination can be conducted with such plastic and non-metal
substrates, however the effectiveness of water lamination can be
affected by the polarity of the material. Accordingly, with respect
to plastics or other non-metal materials, these can be divided into
polar and non-polar plastics or other materials. Employing water
lamination with such materials, the polar materials can generally
form a strong bond, however, non-polar bonds may form weaker bonds
or can delaminate.
[0129] Non-polar substrates can include for example, polyethylene
(PE) and polypropylene (PP) for instance, or plastics formed from
monomers which are not functionalized with a heteroatom or other
group causing polarity. Additionally, some polar substrates may
have a protective non-polar or hydrophobic coating thereon from a
vendor due to manufacturing process.
[0130] Polar groups include oxygen containing groups such as
hydroxyl groups, carboxyl groups, carbonyl groups, or ether groups.
Additionally, polar groups include nitrogen containing groups such
as amine, nitrile, sulfonamide or amide groups as well as halogens,
including chlorine, fluorine, bromine and iodine. For polymeric
substrates, the polar groups or atoms may be part of the main chain
or extend therefrom.
[0131] Further substrates include polymeric substrates having polar
linkages in the main chain and/or polar substituents extending from
the main chain, such as acrylates, methacrylates,
polymethylmethacrylate (PMMA), polyacrylonitriles, polyacrylamides,
polyethers, polyesters, polyethylene terephthalate (PET), polyvinyl
acetate (PVA), polyvinyl chloride (PVC), polyamines, polyamides,
nylon, styrene acrylonitrile polymer (SAN), epoxides,
acrylonitrile-butadiene-styrene (ABS), polycarbonates, and the
like.
[0132] Polystyrene can be considered a polar substrate, however,
water lamination can lead to poor bonding. Accordingly, in order to
provide a strong bond, polystyrene can be laminated by heat or
adhesives, or alternatively can be coated by the desiccant
composition.
[0133] Fiberglass can also serve as a plastic substrate. Fiberglass
is a plastic reinforced with glass fibers, and thus for purposes of
the present disclosure can be considered a plastic or a composite
substrate. The plastic used can be those mentioned herein, with
exemplary plastics including epoxy, polyester, vinylester or a
thermoplastic.
[0134] Additional materials which can serve as a substrate include
glass, silica, concrete, ceramics, paper and other cellulosic
materials, various metal oxides, oxidized carbon, genuine and
synthetic leather, animal skins, and the like.
[0135] The surface of the substrates can affect the ability of the
water lamination to produce a strong bond. For example, a roughened
surface may interfere with water lamination bond. Additionally, and
as mentioned, a treated surface can affect the polarity. For
example, a non-polar or hydrophobic coating, such as a wax may
affect lamination.
[0136] In addition to plastics, substrates can include metals.
These can include alkali metals, alkaline earth metals transition
metals or metals in the periodic table. The metals employed can be
employed alone or as an alloy or as a composite with non-metal
materials. For example, metals in groups 2 through 13 of the
periodic table including metals those in rows 2-4 of the periodic
table can be used as a substrate. In particular, metals Al, Cu, Ti,
and Zn can be used, and in particular Al.
[0137] In some embodiments, the metals to be employed include those
which have a tendency to interact directly with the sulfonic
functional groups of the sulfonated block copolymer membrane. In
such embodiments, the preferred metals are those which are highly
active, are strong reducing agents and which are more likely to
react with acids. Accordingly such metals are high in the so called
Activity Series of elements. Specifically such metals include Li,
K, Ba, Ca, Na, Mg, Al, Zn, Cr, Fe, Cd, Co, Ni, Sn, and Pb with the
first mentioned metals being the highest in activity and each
succeeding metal being less active. Care must be exercised in
handling metallic Li, K, Ba, Ca, Na, and Mg as these metals can
spontaneously ignite in the presence of air. The activate metals
can be used alone or in combination with metals such as alloys or
in composites containing non-metals. The most preferred metal for
use in accordance with the present disclosure being Al due not only
to its high activity but also its broad use across many
applications.
[0138] The desiccant composition disclosed herein can be laminated
or coated on metal substrates. Notably however, metal substrates
employing lamination can result in the strongest bonds, including
thermal, adhesive, solvent, or water lamination. In particular,
water lamination can be employed, resulting in an easy application
of a desiccant composition film. With respect to coating metal
substrates, bonding may not occur, or if bonding does occur weaker
bonds may result. Accordingly, when coating metal substrates,
additional components must be added, for example binders, adhesives
or other components for causing bonding to the surface of the metal
substrate.
[0139] Regarding lamination, with whatever substrate, the desiccant
composition is first formed into a membrane or film, for example
via methods disclosed herein and then joined with the substrate to
form a laminated substrate. There are a number of methods for
laminating the desiccant composition. For example, lamination can
be conducted by heat (thermal) lamination, adhesive, solvent, or
water lamination. Additionally, sonic bonding may be employed for
lamination.
[0140] Heat lamination is carried out by contacting the polymeric
film with the porous substrate under temperature and pressure
thereby forming a bond between the two. The lamination can take
place in a vessel such as an oven or other machine or apparatus
which enables pressing of the polymeric film and porous substrate
together. Generally the temperature ranges from 95.degree. to
450.degree. F., and the pressure can have a range from 100 to 7,000
psi. Residence time, or time subjected to the increased temperature
and pressure can be from 30 seconds to 10 minutes. Thereafter, the
membrane can be cooled at room temperature at atmospheric pressure
to produce the finalized membrane. Various types of laminating
assemblies known in the art can be employed to contact the
polymeric film and substrate under heat and pressure. Adhesives may
also be used in heat lamination processes. Further, heat activated
adhesives may be employed. Thermal lamination can be carried out by
use of a press, which has two flat metal platens which can be drawn
together. Alternatively, a more commercially viable method is via
the use of roller assemblies. The roller assemblies can provide the
desiccant composition film and substrate into rollers which join
the two materials together to laminate the film onto the substrate.
The roller assemblies can be heated for thermal lamination.
[0141] Another method for lamination is adhesive lamination, which
generally utilizes wet or dry adhesives. Adhesive lamination is
carried out by applying adhesive to one side of the desiccant
composition film and then contacting it with a substrate. For
example, the adhesive can be applied across the surface of either
the desiccant film or the substrate or in particular areas.
Commercially available double sided tapes can be employed as well.
The adhesive employed can be for example acrylic, urethane or latex
based. Exemplary tapes can have a service temperature of about
-40.about.70.degree. C. Furthermore, exemplary tapes include those
that conform to UL standards for example, UL 723. Additionally,
exemplary tapes include those that produce low amounts of volatile
organic compounds (VOCs).
[0142] An additional method of lamination is termed solvent
lamination. In this type of lamination, an organic solvent is
applied to the sulfonated block copolymer film. The portion of the
sulfonated polymer film contacted with the solvent accordingly
softens. The film is then pressed onto the substrate thereby
forming a bond between the portions softened by the organic solvent
and the substrate. Organic solvents may be used which have the
effect of solvating portions of the polymeric film. Such organic
solvents include alcohols, alkyls, ketones, acetates, ethers, and
aromatic solvents, such as toluene and benzene. This can be done
under heat or at room temperature.
[0143] "Water lamination" as used herein is where water is employed
as the solvent or as softening liquid. Water as the preferred
solvent can be employed alone or in combination with minor amounts
of other solvents added thereto. Water for use as a solvent may
include minor amounts of impurities and accordingly typical tap
water is sufficient. However, the water source includes spring,
distilled, purified, filtered or deionized or other forms of
treated or untreated water. Even with minor amounts of other
impurities as those typically found in natural water such as salts,
sodium or potassium salts, chlorine or various metal ions water can
be successfully employed for lamination as disclosed herein. The
water should be sufficiently clean such that any impurities do not
interfere with the interaction with the film or sulfonic
functionalities.
[0144] Additionally, the water may have other polar solvents added
thereto. Additional polar solvents include those which do not
degrade the membrane or substantially interfere with the intrinsic
properties of the membrane upon drying (such as moisture vapor
transmission rate "MVTR"). Polar solvents include alcohols, diols,
esters, ethers, ketones, aldehydes, esters of carboxylic acids,
acrylates and contain from 1 to 20 carbon atoms, preferably from 1
to 8 carbon atoms, preferably from 1 to 4 carbon atoms, and can be
linear, branched, cyclic, aliphatic or aromatic. Preferably, any
additional solvents are miscible with water. It will be understood
that high levels of water concentration should be used to avoid
wrinkled or hazy film and potential delamination in the presence of
water.
[0145] The film may be exposed to the solvent by conventional
methods known in the art. One method includes a bath, where the
solvent is poured into a container and the film is soaked in the
solvent. The film can be soaked in the bath for from a few seconds
to 100 hours until the film is sufficiently hydrated. At the least,
the film can be fully hydrated after 24 hours of soaking in a water
bath. The time period to reach full hydration depends on factors
such as the thickness of the film. Furthermore, the point at which
the film is fully hydrated is also the point at which equilibrium
is reached.
[0146] Other methods may include spraying the film with water or
subjecting the film to water vapor by means of jets or mists.
Further methods may also be providing the film in moist or humid
air for sufficient periods to partially or fully hydrate the film,
or use of a squeegee. In these ways water may be adsorbed into the
film.
[0147] In some embodiments, the film will be fully (i.e. 100%)
hydrated with solvent. In order for the film to be successfully
laminated to the polar or active metal substrate it is not required
that the film be fully hydrated. The film should be sufficiently
wetted such that the film interacts with the polar or active metal
substrate to form a bond upon drying. In some embodiments, the film
may be partially hydrated. For example, in some embodiments, the
film may be at least 25% hydrated, alternatively at least 30%
hydrated, alternatively at least 50% hydrated, alternatively at
least 60% hydrated, alternatively at least 75% hydrated,
alternatively at least 90% hydrated.
[0148] After applying the film to the substrate, it is left to dry.
The amount of time for drying is dependent on the type and amount
of solvent, temperature, and humidity of the air and therefore can
be from about 1 minute to 24 hours or more. Warm dry air can used
to speed drying. As discussed above, as the film dries it forms
bonds to the surface of the substrate.
[0149] Alternatively to lamination, the desiccant composition can
be applied via coating process. Similar to solution coating, the
desiccant composition is applied in liquid form onto the substrate,
and then allowed to dry. The desiccant composition can be applied
in the same solution in which the sulfonation reaction occurred.
Alternatively, the sulfonated block copolymer can be cast or
pelletized and re-dissolved in the same solvents noted above with
respect to the sulfonation reaction. In either case, additional
desiccants can be added to the sulfonated block composition as
discussed above and applied to the substrate.
[0150] After applying the desiccant composition to the substrate,
the composition can be left to dry, whereby bonds are formed to the
substrate. Drying can be conducted in room temperature and
atmosphere.
[0151] Application
[0152] The rotary enthalpy exchange wheel having the desiccant
composition as disclosed herein can be employed for improved
exchange of moisture between air streams. The desiccant composition
causes more rapid adsorption and desorption of water from air than
conventional desiccants. In particular, the desiccant composition
has a higher water uptake value in shorter periods of time than
conventional desiccants.
[0153] In one example, the rapid sorption and desorption is a
result of differences in water uptake values depending on relative
humidity of air streams. For example, referring to FIG. 2, the
exiting air stream 190 can be warmer and have higher moisture
content. Whereas entering airstream 195 can be cooler and have
lower moisture content.
[0154] In some examples, the property of moisture exchange can vary
depending on the substrate. Moreover, the relative humidity can
affect the activity of the desiccant composition. For example,
aluminum substrate can demonstrate high water uptake values at high
relative humidity and lower uptake values at lower relative
humidity (RH). This way water can easily be sorbed in high humidity
air streams and then desorbed in low RH air streams releasing
air.
[0155] For example, when the desiccant composition is laminated
onto metal or aluminum substrates, the desiccant composition can
have a change in water uptake during sorption or desorption of at
least about 3% at 10% RH, at least about 7% at 20% RH, at least
about 9% at 30% RH, at least about 11% at 40% RH, at least about
15% at 50% RH, at least about 20% at 60% RH, at least about 20%, or
alternatively, at least about 25% at about 70% RH, at least about
30%, or alternatively, at least about 35% at 80% RH, at least about
40%, or alternatively, at least about 42% at 85% RH, at least about
50%, or alternatively, at least about 52% at 90% RH, at least about
55%, or alternatively, at least about 60% at 95% RH. Additionally,
in some embodiments there is a difference in water uptake of at
least about 40% when RH is changed between 10% and 90% RH after
equilibrium is reached. Such a difference reflects a large degree
of moisture transfer between air streams, for example if an
entering air stream is 10% RH and an exiting air stream is 90% RH,
or vice versa. In other embodiments, there is a difference in water
uptake of at least 20 to 25%, or alternatively 30% to 35% when RH
is changed between 20% and 80% RH after equilibrium is reached.
[0156] When laminated on plastic or non-metal substrates, the
desiccant composition can have a change in water uptake during
sorption or desorption of at least about 2-4% at 10% RH, at least
about 4-7% at 20% RH, at least about 7-9% at 30% RH, at least about
10-12% at 40% RH, at least about 13-15% at 50% RH, at least about
15%, or alternatively at least 19-21% at 60% RH, at least about
20%, or alternatively at least 23-26% at about 70% RH, at least
about 30%, or alternatively at least 34-36% at 80% RH, at least
about 35%, or alternatively at least 41-43% at 85% RH, at least
about 45%, or alternatively at least 50-52% at 90% RH, at least
about 55%, or at least about 60-62% at 95% RH. Additionally, in
some embodiments there is a difference in water uptake of at least
about 40-45% when RH is changed between 10% and 90% RH after
equilibrium is reached. In other embodiments, there is a difference
in water uptake of at least 20%, 25%, 30% or 35% when RH is changed
between 20% and 80% RH after equilibrium is reached.
[0157] For plastic or non-metal substrates where the desiccant
composition is coated thereon, the desiccant composition can have a
change in water uptake during sorption or desorption of at least
about 2-4% at 10% RH, at least about 4-6% at 20% RH, at least about
5-6% at 30% RH, at least about 7-9% at 40% RH, at least about 9-11%
at 50% RH, at least about 12-14% at 60% RH, at least about 16-18%
at about 70% RH, at least about 21-24% at 80% RH, at least about
29-31% at 85% RH, at least about 35-37% at 90% RH, at least about
42-44% at 95% RH. Additionally, in some embodiments there is a
difference in water uptake of at least about 30%, 35%, or 40% when
RH is changed between 10% and 90% RH after equilibrium is reached.
In other embodiments, there is a difference in water uptake of at
least 15%, 20% or 25% when RH is changed between 20% and 80% RH
after equilibrium is reached.
[0158] For plastic or non-metal substrates where the desiccant
composition is a mixture of sulfonated block copolymer and at least
one other desiccant, such as silica gel, and coated on a plastic
such as oriented polystyrene, the desiccant composition can have a
change in water uptake during sorption or desorption of at least
about 2-4% at 10% RH, at least about 4-6% at 20% RH, at least about
5-8% at 30% RH, at least about 10-12% at 40% RH, at least about
13-17% at 50% RH, at least about 16-19% at 60% RH, at least about
18-20% at about 70% RH, at least about 19-22% at 80% RH, at least
about 20-22% at 85% RH, at least about 31-24% at 90% RH, at least
about 24-26% at 95% RH. Additionally, in some embodiments there is
a difference in water uptake of at least about 15%, or 20%, when RH
is changed between 10% and 90% RH after equilibrium is reached. In
other embodiments, there is a difference in water uptake of at
least 10% or 15% when RH is changed between 20% and 80% RH after
equilibrium is reached.
[0159] Accordingly, by having such high sorption in higher humidity
air streams, and the tendency to desorb in lower humidity air
streams, the bonded desiccant compositions as disclosed herein
provide advantageous moisture or enthalpy exchange between air
streams.
ILLUSTRATIVE EMBODIMENTS
[0160] 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 disclosure.
[0161] a. Materials and Methods
[0162] Degree of Sulfonation: The degree of sulfonation as
described herein and as determined by titration was measured by the
following potentiometric titration procedure. The 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 0.1 N
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 0.14 N 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.
[0163] 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.
[0164] 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-d8
(THF-d8), to which was then added with a partial drop of
concentrated sulfuric acid 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.
[0165] 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.
[0166] b. Experiments
[0167] Preparation of Sulfonated Block Copolymer SBC-1
[0168] A pentablock copolymer having the configuration A-D-B-D-A
was prepared by sequential anionic polymerization where the A
blocks are polymer blocks 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 initiated 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 having a molecular weight of 28,000 g/mol. To this
solution was added another aliquot of isoprene monomer resulting in
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-butylstyrene
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.sub.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 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. The solution
was then coated onto a PET release liner through the use of a slot
die. In such case, the coating moves through slot die head to a
zoned heating oven where the solvent is removed. The cast film was
then resolvated in toluene/n-propanol mixture solvent (mixing
ratio: 1:1%-wt.) with a resultant solids of 14.about.15%-wt.
[0169] Films of the compositions prepared as described above were
either coated onto a substrate (direct coating) or cast to a film
against siliconized glass plates at room temperature in a box with
a nitrogen purge. Films were allowed to dry in this manner for a
period of at least 16 hours. No further post-treatments of the film
were performed except those specifically required by particular
testing procedures. Typical film thicknesses obtained by this
procedure range from 0.25 to 2.0 mils.
Example 1
[0170] SBC-1 was cast to a film having a thickness of 0.5 mil and
then adhesively laminated to both sides of an aluminum substrate,
entitled "SBC-1/Al" in FIG. 4. As used in the examples herein,
adhesive lamination refers to bonding the film to the substrate
with a double sided tape having an acrylic adhesive. As a
comparison, an aluminum foil substrate was coated on both sides
with silica gel ("SG-1"), entitled "SG-1/Al" in FIG. 4.
[0171] The SBC-1 Al laminate substrate and the SG-1 coated aluminum
substrate were then subject to a sorption and desorption cycle with
results shown in FIG. 4, noted therein as "Sorp" or "Desorp",
respectively. Each cycle consisted of increasing RH by 5%
increments from zero to about 95%. With each increment the two
samples were allowed to equilibrate, and then the change in mass
measured to determine water uptake.
[0172] As shown in FIG. 4, the SBC-1 Al laminate demonstrated much
higher water uptake than the SG-1 coated aluminum substrate across
the entire range of RH. Further, the difference in the amount of
water uptake increased non-linearly as RH increased, with water
uptake increasing at greater rates at higher RH, demonstrating
approximate exponential growth. The SBC-1 samples showed no
occurrence of dusting or the presence of any odor.
[0173] As a result of such advantageous results, when employed in a
rotary enthalpy exchange wheel exchange, the SBC-1 Al laminate
would provide greater exchange of moisture between air streams than
conventional systems. For example, an exiting air stream having
high humidity would sorb a larger degree of moisture, and then
desorb into the entering air stream thereby providing a high degree
of exchange.
Example 2
[0174] For example 2, SBC-1 was cast to a film having a thickness
of 0.5 mil and then adhesively laminated to both sides of an
oriented polystyrene as a substrate, entitled "SBC-1/Plastic
Laminate1" in FIG. 5. A second adhesive laminate of SBC-1 film on a
polystyrene substrate with the same adhesive was made entitled
"SBC-1/Plastic Laminate2" in FIG. 5. Moreover, for "SBC-1 Coated
Plastic" in FIG. 5, the SBC-1, rather than casting to a film, was
direct coated onto both sides of an oriented polystyrene substrate,
entitled "SBC-1 Coated Plastic." As an additional comparison,
SBC-1, after being removed from the reactor and stored, was mixed
with SG-2 to 460%-wt. and then coated on to an oriented
polystyrene. This sample is entitled "SBC-1/SG-2 Coated Plastic" in
FIG. 5. As a comparative example to the SBC-1 containing desiccant
compositions, oriented polystyrene was coated with a SG-2, entitled
"SG-2 Coated Plastic" in FIG. 5. SG-2 is a Type A silica gel having
a nominal 22 .ANG. pore size. Each of the samples were subject to a
sorption and de-sorption cycle with results shown in FIG. 5, noted
therein as "Sorp" or "Desorp", respectively. Each cycle consisted
of increasing RH from zero at about 5% increments of up to a RH of
about 95%. At each increment the samples were allowed to
equilibrate, and then the change in mass measured for water uptake.
Two cycles were conducted to test redundancy of results.
[0175] As shown in FIG. 5, the SBC-1 containing desiccant
compositions outperformed the SG-2 sample. Specifically, the SBC-1
laminates had higher water uptake throughout the range at 50% RH
and above than the SG-2 sample. The coated SBC-1 sample
demonstrated higher water uptake at ranges above approximately 70%
RH. Surprisingly, for each of the samples containing only SBC-1,
namely, the SBC-1 laminate and coated samples, the difference in
the amount of water uptake increased non-linearly as RH increased,
with water uptake increasing at greater rates at higher RH,
demonstrating approximate exponential growth. Therefore, there was
a more than 35-40% difference in water uptake at RH of 90% or more,
and at least 20-25% at RH of 80%. Surprisingly, the mixed
SBC-1/SG-2 composition showed higher water uptake than the SG-2
sample above 60% RH.
[0176] With such great increases in water uptake at the higher RH
values while having low water uptake at low RH values, the SBC-1
containing desiccant compositions would have superior water
transfer between air streams in a rotary enthalpy exchange wheel
over conventional desiccants.
Example 3
[0177] FIGS. 6A through 6D demonstrate the advantages of the
desiccant compositions of the present disclosure over conventional
compositions with respect to microparticle shedding, referred to
herein as dusting. In particular, 1 ft. x 3 inch samples were
prepared made up of (a) SG-1 coated on oriented polystyrene ("PS"),
(b) SG-2 coated Al, (c) molecular sieve coated Al, and (d) a mix of
SBC-1 and SG-1 ("SBC-1/SG-1") coated on PS. These samples were then
placed in controlled atmosphere of 68.degree. F., 50% RH for 24
hours.
[0178] Thereafter, carbon tape was placed on each sample with
minimal pressure. Any dust particles which might have developed on
the surfaces would then be trapped beneath the carbon tape when
applied thereon. The samples (a)-(d) were then viewed with a
scanning electron (SEM) microscope, the results of which are shown
in FIGS. 6A through 6D, respectively.
[0179] As shown in FIG. 6A the SG-1 coated PS produced the largest
spread of dust, whereas in FIG. 6B, SG-2 coated on Al showed large
conglomerations. In FIG. 6C having the molecular sieve coated Al
sample showed the collection of dust across the surface but to a
lesser extent than that in FIG. 6A. However, surprisingly, as can
be seen in the SEM FIG. 6D, the SBC-1/SG-1 coated on PS has very
little particle shedding as compared to the other three
commercially available wheel samples (a)-(c).
[0180] The embodiments shown and described above are only examples.
Therefore, many such details are neither shown nor described. Even
though numerous characteristics and advantages of the present
technology have been set forth in the foregoing description,
together with details of the structure and function of the present
disclosure, the disclosure is illustrative only, and changes may be
made in the detail, especially in matters of shape, size and
arrangement of the parts within the principles of the present
disclosure to the full extent indicated by the broad general
meaning of the terms used in the attached claims. It will therefore
be appreciated that the embodiments described above may be modified
within the scope of the appended claims.
* * * * *