U.S. patent application number 13/390900 was filed with the patent office on 2012-07-05 for articles including a porous substrate having a conformal layer thereon.
Invention is credited to Bill H. Dodge.
Application Number | 20120171403 13/390900 |
Document ID | / |
Family ID | 43796159 |
Filed Date | 2012-07-05 |
United States Patent
Application |
20120171403 |
Kind Code |
A1 |
Dodge; Bill H. |
July 5, 2012 |
ARTICLES INCLUDING A POROUS SUBSTRATE HAVING A CONFORMAL LAYER
THEREON
Abstract
An article of manufacture includes a body having an inlet and an
outlet, and at least a portion of at least one porous non-ceramic
substrate positioned such that the porous polymeric substrate
separates the inlet from the outlet. The porous non-ceramic
substrate has a conformal coating on at least a portion of its
interior surfaces.
Inventors: |
Dodge; Bill H.; (Finlayson,
MN) |
Family ID: |
43796159 |
Appl. No.: |
13/390900 |
Filed: |
September 17, 2010 |
PCT Filed: |
September 17, 2010 |
PCT NO: |
PCT/US10/49250 |
371 Date: |
February 16, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61244696 |
Sep 22, 2009 |
|
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61244713 |
Sep 22, 2009 |
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Current U.S.
Class: |
428/36.1 ;
428/308.4; 428/36.5; 442/164 |
Current CPC
Class: |
C08J 2201/038 20130101;
C08J 9/365 20130101; C23C 16/45555 20130101; D06M 11/36 20130101;
Y10T 442/2861 20150401; H01L 21/02422 20130101; C23C 16/045
20130101; H01L 21/02428 20130101; C23C 16/403 20130101; Y10T
428/249958 20150401; C23C 16/45546 20130101; C23C 16/45525
20130101; D06M 11/58 20130101; D06M 23/005 20130101; D06M 11/45
20130101; H01L 21/02532 20130101; Y10T 428/1362 20150115; Y10T
428/1376 20150115; D06M 11/53 20130101; D06C 29/00 20130101 |
Class at
Publication: |
428/36.1 ;
428/36.5; 428/308.4; 442/164 |
International
Class: |
B32B 5/18 20060101
B32B005/18; B32B 9/04 20060101 B32B009/04; B01J 19/00 20060101
B01J019/00 |
Claims
1. An article of manufacture comprising: a body having an inlet and
an outlet, and at least a portion of at least one porous
non-ceramic substrate positioned such that the porous non-ceramic
substrate separates the inlet from the outlet, wherein the porous
non-ceramic substrate has a conformal coating on at least a portion
of its interior surfaces, wherein the porous non-ceramic substrate
is a porous polymeric substrate.
2. The article according to claim 1 wherein the conformal coating
has at least 8 molecular layers.
3. The article according to claim 1 wherein the conformal coating
has at least 20 molecular layers.
4. The article according to claim 1 wherein the conformal coating
has a surface energy of greater than 72 dyne/cm.
5. The article according to claim 2 wherein the exterior surface of
the porous non-ceramic substrate nearest the outlet has a surface
energy less than 72 dyne/cm.
6. (canceled)
7. The article according to claim 1 wherein the porous polymeric
substrate is a TIPS substrate.
8. The article according to claim 1 wherein the porous polymeric
substrate is a non-woven substrate.
9. The article according to claim 1 further comprising at least a
second porous non-ceramic substrate positioned such that the second
porous non-ceramic substrate also separates the inlet from the
outlet.
10. (canceled)
11. (canceled)
12. The article according to claim 1 wherein the conformal coating
comprises a metal oxide, metal nitride, metal sulfide, or a
combination thereof.
13. The article according to claim 12 wherein the metal is selected
from the group consisting of silicon, titanium, aluminum,
zirconium, and yttrium.
14. (canceled)
15. (canceled)
16. (canceled)
17. The article according to claim 12 further comprising a fluid
contact layer formed of at least one ligand chemically grafted to
the conformal coating.
18. (canceled)
19. An article of manufacture comprising: a porous non-ceramic
substrate having a conformal coating on all its interior surfaces
through its entire thickness, wherein the porous non-ceramic
substrate is a porous polymeric substrate.
20. The article according to claim 19 wherein the conformal coating
extends to the external surfaces.
21. The article according to claim 1 wherein the conformal coating
has at least 8 molecular layers.
22. (canceled)
23. The article according to claim 1 wherein the conformal coating
has a surface energy of greater than 72 dyne/cm.
24. (canceled)
25. The article according to claim 19 wherein the porous polymeric
substrate is a TIPS substrate.
26. The article according to claim 19 wherein the porous polymeric
substrate is a non-woven substrate.
27. The article according to claim 19 wherein the conformal coating
comprises a metal oxide, metal nitride, metal sulfide, or a
combination thereof.
28. The article according to claim 27 wherein the metal is selected
from the group consisting of silicon, titanium, aluminum,
zirconium, and yttrium.
29. (canceled)
30. (canceled)
31. (canceled)
32. The article according to claim 19 further comprising a fluid
contact layer formed of at least one ligand chemically grafted to
the conformal coating.
33. (canceled)
34. The article according to claim 19 wherein the conformal coating
reduces the porosity of the porous non-ceramic substrate by a
predetermined amount.
35. (canceled)
36. (canceled)
37. (canceled)
38. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Patent Application Nos. 61/244,696 and 61/244,713, both filed Sep.
22, 2009, the disclosures of which are incorporated by reference
herein in their entirety.
TECHNICAL FIELD
[0002] The present invention is related to articles having a porous
non-ceramic substrate with a conformal coating on its interior
surfaces.
BACKGROUND
[0003] The Atomic Layer Deposition (ALD) process was originally
developed for thin film electroluminescent (TFEL) flat-panel
displays. Interest in ALD has increased significantly over the
years, focusing on silicon-based microelectronics (wafers) due to
its ability to produce very thin, conformable films with control of
the composition and thickness of these films at the atomic level.
ALD is also well known for its ability to coat high aspect ratio
surfaces due to its self-limiting, sequential surface reaction
process. However, the process' ability to coat these high aspect
ratio surfaces is challenged by the time needed for the reactive
gases to diffuse into these areas and be completely purged out
prior to the addition of the next precursor. This diffusion problem
has largely prevented the extension of this technology to porous
materials, and by extension to manufactured articles having porous
substrates with ALD coatings.
SUMMARY
[0004] The present invention enables the use of ALD coatings in
porous substrates which in turn makes possible diverse articles of
manufacture such as filters, extraction columns, catalytic
reactors, and the like having a conformal coating on at least a
portion of its interior surfaces. In one aspect, the present
invention provides an article of manufacture including a body
having an inlet and an outlet, and at least a portion of at least
one porous non-ceramic substrate positioned such that the porous
polymeric substrate separates the inlet from the outlet. The porous
non-ceramic substrate has a conformal coating on at least a portion
of its interior surfaces. In a second aspect, the invention
provides an article of manufacture including a porous non-ceramic
substrate having a conformal coating on all its interior surfaces
through its entire thickness.
DEFINITIONS
[0005] In connection with this disclosure, the word "porous" means
that the substrate contains openings (i.e. "pores") sufficient that
at least a gas can pass through it.
[0006] The word "microporous" means that the substrate contains
pores having a median internal cross-sectional dimension (a "median
pore size," e.g. a diameter for the case of cylindrical pores) of
no greater than 1,000 micrometers such that a gas may pass through
the substrate within the pores. Preferred microporous substrates
include pores having a median pore size of from 0.01 to 1,000
micrometers, inclusive, more preferably from 0.1 to 100
micrometers, inclusive, even more preferably from 0.2 to 20
micrometers, inclusive, and most preferably from 0.3 to 3
micrometers or even 1 micrometer, inclusive. As used throughout
this specification, median pore size was determined using the
bubble point pressure measurement method described in ASTM Standard
F316-03.
[0007] The word "nonporous" means that the substrate is
substantially free of pores.
[0008] The word "non-ceramic" with reference to a substrate prior
to deposition of the conformal coating means that the substrate
does not substantially include inorganic metal oxides, metal
nitrides, metal carbides, or other ceramic materials. Preferred
"non-ceramic" substrates are completely free of ceramic materials,
and more preferably consist essentially of fibrous organic
materials (e.g. polymeric fibers, natural fibers, carbon fibers,
and the like), and even more preferably consist only of organic
materials
[0009] The word "conformal coating" means a relatively thin coating
of material that adheres well to and conforms closely to the shape
of an underlying substrate.
DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows a cross-section view through an article
according to the present invention.
[0011] FIG. 2 shows a graph comparing an increase in pressure drop
across the substrates compared to the number of process iterations
during the experiment of Example 1.
DETAILED DESCRIPTION
[0012] The articles of the invention possess a conformal coating on
at least a portion of the interior surfaces of non-ceramic
substrate. In many convenient embodiments, the conformal coating is
applied to at least a region through the entire thickness of the
substrate. Preferably, the conformal coating is applied to all
interior surfaces of the substrate. In many convenient embodiments,
the conformal coating comprises a metal oxide, a metal nitride, a
metal sulfide, or a combination thereof. The metal in these
instances may be of various sorts, but silicon, titanium, aluminum,
zirconium, and yttrium are considered particularly suitable.
Preferably, the metal is silicon, titanium, or aluminum; more
preferably, the metal is aluminum. In some preferred embodiments,
the conformal coating comprises aluminum oxide.
[0013] Coatings that can be applied via atomic layer controlled
growth techniques are preferred. Among coatings that are readily
applied in such a manner are binary materials, i.e., materials of
the form Q.sub.x R.sub.y, where Q and R represent different atoms
and x and y are numbers that reflect an electrostatically neutral
material. Among the suitable binary materials are various inorganic
oxides (such as silicon dioxide and metal oxides such as zirconia,
alumina, silica, boron oxide, yttria, zinc oxide, magnesium oxide,
TiO.sub.2 and the like), inorganic nitrides (such as silicon
nitride, AlN and BN), inorganic sulfides (such as gallium sulfide,
tungsten sulfide and molybdenum sulfide), as well as inorganic
phosphides. In addition, various metal coatings are useful,
including cobalt, palladium, platinum, zinc, rhenium, molybdenum,
antimony, selenium, thallium, chromium, platinum, ruthenium,
iridium, germanium and tungsten.
[0014] Useful discussions of the application of self-limiting
sequential coatings can be found, for example, in U.S. Pat. Nos.
6,713,177; 6,913,827; and 6,613,383.
[0015] Those familiar with the field of ALD reactions can readily
determine which first and second reactive gases are appropriate
choices for the self-limiting reactions in order to create the
conformal coatings discussed above. For example, if an aluminum
containing compound is desired, trimethylaluminum or
triisobutylaluminum gases may be used as one of the two reactive
gases. When the desired aluminum containing compound is aluminum
oxide, the other reactive gas in the iterations can be water vapor
or ozone. When the desired aluminum containing compound is aluminum
nitride, the other reactive gas in the iterations can be ammonia or
a nitrogen/hydrogen plasma. When the desired aluminum containing
compound is aluminum sulfide, the other reactive gas in the
iterations can be hydrogen sulfide.
[0016] Likewise, if instead of aluminum compounds, silicon
compounds are wanted in the conformal coating, one of the two
reactive gases can be, e.g., tetramethylsilane or silicon
tetrachloride. The references incorporated above give further
guidance about suitable reactive gases depending on the end result
desired.
[0017] While a single iteration with the discussed reactive gases
can lay down a molecular layer that may be suitable for some
purposes, many useful embodiments of the method will iterate the
performing step for at least 8, 10, 20 or more iterations. Each
iteration adds thickness to the conformal coating. Therefore, in
some embodiments, the number of iterations is selected to achieve a
predetermined porosity or average internal pore diameter in the
porous non-ceramic substrate. In some embodiments, by controlling
the number of iterations performed, the conformal coating can be
used to controllably reduce the porosity of the porous non-ceramic
substrate (e.g., to control the apparent pore size of the
substrate) to achieve a desired porosity (e.g., a desired average
internal pore diameter). For example, the conformal coating may
reduce the porosity of the porous non-ceramic substrate by 5% or
more, 25% or more, or even 50% or more. Similarly, if the substrate
comprises pores, the conformal coating may reduce the average
internal pore diameter by 5 nm or more.
[0018] In some applications, the purpose of applying the method is
to achieve hydrophilicity on the interior surfaces of the
substrate. In these applications, the step is iterated until a
target surface energy such as, e.g., 72 dyne/cm (one commonly used
definition of hydrophilic nature) is achieved. Further, it may also
be desirable for the exterior surface of the porous non-ceramic
substrate nearest the outlet to have a surface energy greater than
72 dyne/cm as well, and in these circumstances the performing step
should be iterated until that target is achieved. Contrariwise, in
some specialized embodiments it may be desirable to have the
interior surfaces hydrophilic while the exterior surface of the
porous non-ceramic substrate nearest the outlet is left hydrophobic
(e.g., less than 72 dyne/cm).
[0019] The application of the conformal coating to the articles of
the invention can be carried out at any useful temperature that
does not damage the substrate. In some embodiments, the method is
carried out, e.g., at a temperature of about 300.degree. C. or
less, about 200.degree. C. or less, about 70.degree. C. or less, or
even about 60.degree. C. or less.
[0020] In many useful embodiments of the invention, the porous
non-ceramic substrate is a porous polymeric substrate. In such
embodiments, it is often convenient that the introducing of the
first and the second reactive gases be done at a temperature below
the melting temperature of the porous polymeric substrate so as not
to cause thermal distortion of the substrate or pores. For example,
the method of the present invention can be operated at, e.g., below
300.degree. C. if that is desirable for the structural integrity of
the substrate.
[0021] When a porous polymeric substrate is employed, it may be
convenient to use a substrate that has been rendered porous using
an induced phase separation technique such as thermally induced
phase separation (TIPS), vapor induced phase separation (VIPS), or
the co-casting method of inducing phase separation discussed in
U.S. Patent Application Publication No. US 2008/0241503.
[0022] Other ways of forming porous substrates from polymeric
materials will commend themselves to the ordinary artisan for use
with the present invention. For example, staple non-wovens such as
stitchbonded or hydro-entangled webs may be used, as well as
spunlaid non-wovens such as melt-blown or spun-bonded webs. For
other applications, non-polymeric non-ceramic materials such
natural fabrics, carbon fibers, fritted metal, or glass can be
suitable.
[0023] In connection with the present invention, the physical
topology of the porous non-ceramic substrate is not critical.
Depending on end use, the porous non-ceramic substrate may be flat,
pleated, tubular, in the form of a thin hollow fiber, either
singular or as a potted fiber cartridge, or any other useful
configuration.
[0024] When making articles according to the present invention in
reactors having an inlet and an outlet, it is possible, and
sometimes convenient, to position at least a portion of at least a
second porous non-ceramic substrate such that the second porous
non-ceramic substrate also separates the inlet from the outlet. It
has been demonstrated that three or more porous non-ceramic
substrates can be successfully treated simultaneously using the
method.
[0025] The porous non-ceramic substrate can be treated in a batch
process, or the porous non-ceramic substrate may by in the form of
a web of material of indefinite length and the positioning means
can be of a type that permits a roll-to-roll process. Such a
roll-to-roll process may be of the step-and-repeat sort, or it can
be a continuous motion process.
[0026] One convenient variant of the method is to perform the
process in a batch reactor such that the reactor itself is
incorporated into the product intended for the end consumer. For
example, the reactor may be in the form of a filter body, and both
the filter body and the porous non-ceramic with its conformal
coatings applied in situ can be part of a filter to be sold to the
end user. In some embodiments, multiple filters can be
simultaneously treated in series or parallel connected flow
paths.
[0027] In many convenient embodiments, the porous non-ceramic
substrate is suited to its end use once the conformal coating has
been applied on the interior surfaces. However, it is sometimes
useful to perform a secondary operation on the conformal coating.
This can be done either within the reactor or in another convenient
apparatus. For example, even in cases where the internal surfaces
of the porous non-ceramic substrate have been rendered hydrophilic,
one or both of the external surfaces of the porous non-ceramic
substrate can be treated with a final size coating to render them
hydrophobic. This technique could be used to prepare, e.g., a vent
filter for an endotracheal tube that should pass only gas and water
vapor, not liquid water.
[0028] Another secondary operation that can be performed is to
graft chemical moieties to the conformal coating. For example, a
discussion of a technique which can be extrapolated to provide a
porous non-ceramic substrate with its conformal coating according
to the present invention with grafted ligand groups, e.g., selected
from polyethyleneimine ligand groups and biguanide ligand groups,
can be found in U.S. Patent Application Publication Nos. US
2010/0075131 and US 2010/0075560. Grafting by radiant or particle
energy can also be used to attach other useful ligands such as
silanes, biologically active moieties such as antibodies, chelating
agents, and catalytic coatings.
[0029] Porous non-ceramic substrates provided with conformal
coatings according to the method of the present invention lend
themselves to numerous uses. For example, the filtration of both
liquids and gases may be enhanced by the use of the treated
substrates. With regard to, e.g., water filtration, conformal
coatings that provide hydrophilicity to a porous filter element can
act to reduce resistance and enhance flow through a filter. This is
especially useful when the filter is to be used under gravity flow
conditions and low pressure applications. The physical size and
spacing of the pores can be selected as well as the conformal
coating to achieve particular effects. For example, the porous
non-ceramic substrate can be fine fiber meltblown or nanofiber webs
that have fiber-to-fiber spacings that can prevent the liquid from
passing through the openings below a certain pressure, i.e.,
"liquid hold out".
[0030] Certain conformal coatings as described above can be used to
reduce scale deposits from forming in filter elements made
according to the present invention. This can be accomplished by
applying, in a secondary operation, coating designed to reduce
compatibility with the scale materials. Silver or other
antimicrobial materials can also be bound to some of the described
coatings to help prevent the formation and growth of bio-film on
the surfaces of the porous non-ceramic substrate or to treat the
liquid being filtered. Further, it is believed that, e.g., metal
oxide coatings themselves, without secondary treatment, could allow
such filters to operate at higher service temperatures, potentially
enabling applications involving hot water or water/steam.
[0031] The filtration of other liquids besides water and its
solutions can benefit from treated substrates according to the
present invention as well. For example, conformal coatings that
enable higher service temperatures could allow filtration of heated
oils. Some conformal coatings could provide chemical resistance in
acidic or high pH environments. A filter can be provided having
several filter elements, each provided with variations of the
present invention adapting them to restrict or adsorb different
chemical contaminants, providing "depth filtration."
[0032] The treatments discussed above also lend themselves to
applications in air filtration. As discussed above, conformal
coatings could enable higher service temperatures in air filtration
applications as well. It is contemplated that with sufficient
iterations, air filters could be provided according to the present
invention with sufficient heat resistance for, e.g., the filtration
of diesel exhaust. Secondary antimicrobial, adsorptive, or
catalytic coatings could adapt, e.g., melt-blown substrates for use
as masks for biomedical use or as personal protective gear. For
example, nano-gold catalysts could be bound to the conformal
coating to allow it to act as a carbon monoxide remover in a
protective mask.
[0033] Beyond filtration, the method of the present invention lends
itself to the treatment of porous insulation. Anti-microbial
materials applied in a secondary operation could reduce the
potential for biological contamination in, e.g., moist
environments. It is contemplated that with sufficient iterations,
insulation with flame retardant properties could be provided.
[0034] Further, it is contemplated that porous non-ceramic
substrates according to the present invention, especially with a
biocompatiblizing layer added in a secondary operation, could be
used a tissue scaffolds for diverse medical applications.
[0035] Certain porous non-ceramic substrates according to the
present invention may be particularly suitable for some
applications. For example, polyvinylidene fluoride (PVDF) made
hydrophilic can be particularly suitable for applications in
filtration, substrates for anion exchange membranes, vent filters
for endotracheal tubes, and sample preparation devices for food
safety; nylon made hydrophilic can be particularly suitable for
applications in protein purification and water purification (e.g.,
through attachment of quat silane); and non-woven made hydrophilic
can be particularly suitable for applications such as cleaning
wipes for infection prevention, depth filtration, and ample
preparation devices for food safety.
[0036] Referring now to FIG. 1, a cross-section view through an
article 20 of the present invention is illustrated. The depicted
article 20 is suited to batch processes in connection with the
invention, and has a body 22 including an inlet 24 and an outlet
26. The inlet 24 and the outlet 26 are on opposite sides of three
separate portions of porous non-ceramic substrate 30a, 30b, and 30c
such that reactive gasses introduced at inlet 24 in direction D1
must pass through all of portions of porous non-ceramic substrate
30a, 30b, and 30c to make their way to the outlet 26 in direction
D2. In the depicted embodiment, portions of substrate 30a, 30b, and
30c are conveniently gripped at their edges by double-sided flanges
32a, 32b, 32c, and 32d, although skilled artisans will recognize
that other expedients can be used for this purpose.
EXAMPLES
[0037] Objects and advantages of this invention are further
illustrated by the following examples, but the particular materials
and amounts thereof recited in these examples, as well as other
conditions and details, should not be construed to unduly limit
this invention.
Method of Testing the Surface Energies of Samples
[0038] Several samples of porous substrates having a conformal
layer or coating thereon are described below in connection with the
Examples. Where the surface energy of the sample is discussed, that
reading was obtained in the following way: Dyne test solutions were
obtained in various levels. Solutions according to ASTM Standard
D-2578 ranging in level from 30 to 70 dynes/cm were purchased from
Jemmco, LLC of Mequon, Wis. Solutions ranging in level from 72 to
86 dynes/cm were prepared by mixing the amount of
MgCl.sub.2.6H.sub.2O shown on Table 1 with sufficient deionized
water to make a total of 25 grams of solution.
TABLE-US-00001 TABLE 1 Grams of MgCl.sub.2.cndot.6H.sub.2O Level of
dyne test solution being added to DI water to make a total made
(dyne/cm) of 25 grams of solution 72 0.00 74 2.26 76 4.93 78 7.39
80 9.56 82 11.40 84 12.94 86 14.24
[0039] Using these dyne test solutions, the substrate needing
testing as discussed below was subjected to the Drop Test discussed
in section 12 of ASTM Standard ASTM D7541-09.
Preparation of Substrate A
[0040] A microporous polypropylene substrate was prepared using a
Thermally Induced Phase Separation (TIPS) process generally as
described in U.S. Pat. Nos. 5,120,594 (Mrozinski) and 4,726,989
(Mrozinski). More specifically, a nucleated polypropylene/mineral
oil blend was prepared and extruded into a smooth, chilled casting
wheel where the material underwent solid-liquid phase separation. A
continuous substrate of this material was collected and passed
through a 1,1,1-trichloroethane bath to remove the mineral oil. The
microporous polypropylene substrate thus formed had a thickness of
244 .mu.m (9.6 mil). The microporous polypropylene substrate was
then tested according to ASTM Standard F316-03 and found to have an
isopropanol alcohol bubble point pressure of 69.7 kPa (10.11 psi)
corresponding to a bubble point pore size of 0.90 .mu.m. Further,
it had a porosity of 83.3%, and a pure water permeability of 477
L/(m.sup.2-h-kPa). The substrate was strongly hydrophobic, having a
surface energy of 29 dyne/cm.
Preparation of Substrate B
[0041] Another microporous substrate was prepared from an
ethyelene-chlorotrifluoroethylene copolymer (ECTFE), commercially
available under the trade name and grade designation HALAR 902 by
Solvay Advanced Polymers, L.L.C., of Alpharetta, Ga. This was
accomplished by a TIPS process generally as described in U.S.
Patent Application Publication No. US 2009/0067807. More
specifically, microporous ECTFE substrate was made using a twin
screw extruder equipped with a melt pump, neck tube, and sheeting
die positioned above a patterned casting wheel positioned above a
water-filled quench bath. Using this set-up, the microporous ECTFE
substrate was made by melt extruding a casting dope comprising
ECTFE a diluent, and a solvent; casting and then quenching the
dope; solvent washing to remove the diluent; drying to remove the
solvent; and stretching the resulting substrate to a finished
thickness of 48 .mu.m (1.9 mil). The microporous ECTFE substrate
was then tested according to ASTM Standard F316-03. It was found to
have an isopropyl alcohol bubble point pressure of 186.1 kPa (26.99
psi) corresponding to a bubble point pore size of 0.34 .mu.m, a
porosity of 65.3%, and a pure water permeability of 48
L/(m.sup.2-h-kPa). The membrane was hydrophobic, having a surface
energy of 37 dyne/cm.
Preparation of Substrate C
[0042] Another microporous substrate, a nonwoven (meltblown)
polypropylene web, was prepared as follows. Polypropylene pellets
commercially available as Total 3960 from Total Petrochemical of
Houston, TX were used to form meltblown web using conventional
techniques, specifically extrusion of the molten polypropylene at a
rate of 7.6 lb/hr and a melt temperature of 285.degree. C.
(nominal) through a 10 inch wide meltblowing die of the Naval
Research Lab (NRL) type towards a collecting drum set a distance of
12 inches (30.5 cm) from the die. The resulting web was collected
at 10 ft/min (305 cm/min). The observed basis weight was 67
g/m.sup.2. The air temperature and velocity were adjusted to
achieve an effective fiber diameter (EFD) of 7.9 microns. This EFD
was calculated according to the method set forth in Davies, C. N.,
"The Separation of Airborne Dust and Particles," Institution of
Mechanical Engineers, London Proceedings 1B, 1952.
Preparation of Substrate D
[0043] Another microporous substrate in the form of a graphite felt
with a nominal thickness of 0.25 inch (6.35 mm), commercially
available as "GRADE GH" from Fiber Materials, Inc., of Biddeford,
Me., was obtained.
Preparation of Substrate E
[0044] Another microporous substrate in the form of a fiberglass
mat, commercially available as "1210NC" from 3M Company of St.
Paul, Minn., was obtained.
Reactor
[0045] A reactor generally as depicted in FIG. 1 was constructed
using three 6 inch (15.24 cm) diameter double side flanges
commercially available as ConFlat Double Side Flanges (600-400-D
CF) from Kimball Physics Inc. of Wilton, N.H.. To this stack of
flanges on what was to be the upstream side was attached one 6 inch
(15.24 cm) diameter ConFlat Double Side Flange (600DXSP12) from
Kimball Physics Inc., which has one 1/8'' (0.32 cm) NPT side hole.
This side hole was used to attach a Baratron (10 ton) pressure
gauge, commercially available from MKS Instruments of Andover,
Mass., so that the pressure during the process could be monitored.
This stack of elements was capped on each end with a 6 inch
diameter (15.24 cm) ConFlat Zero-Length Reducer Flange
(600.times.275-150-0-T1) commercially available from Kimball
Physics Inc. At each of the junctions in the stack, appropriate
sized copper gaskets were used so as to make a good vacuum
seal.
[0046] To this stack of elements, first a 2.75 inch (7 cm) diameter
ConFlat Double Side Flanges (275-150-D CF) was attached to the
inlet side, followed by a 2.75 inch (7cm) diameter ConFlat Double
Side Flanges with two 1/8 '' (0.32 cm) NPT Side Holes (275DXSP12
modified for 2 side holes versus standard 1 side hole), and further
followed by a 2.75 inch (7 cm) diameter ConFlat Solid/Blank Flange.
The two side holes are used for introducing the reactive gases as
will be discussed below.
[0047] To this stack of elements, first a 25 ISO to 275 CF Reducer
(QF25X275) was attached to the outlet side. That element was
connected to the bottom of a 275 ConFlat 4 way Cross (275-150-X),
itself also equipped with a 25 ISO to 275 CF Reducer. This
expedient allowed an easier set up for faster removal of the main
reactor body from the supporting system for sample loading and
removal. The 275 ConFlat 4 way Cross was then connected to a XDS-5
Scroll pump (equipped with purging capability) via flexible
Stainless Steel vacuum hose equipped with a gate valve for the
vacuum source and control, a SRS PPR300 Residual Gas Analyzer with
bypass sampling and a MKS Baratron (10 torr) gauge for post
membrane pressure readout. A valved roughing/bypass line with a
1/16 inch (0.16 cm) drilled orifice was installed around the gate
valve to allow for reduced pumping but was also found to be useful
as a secondary pumping line to allow for greater reactor pressure
during surface treatments.
[0048] Inlets for the first and the second reactive gases were
disposed with the 1/8'' NPT side holes in the 2.75 inch (7 cm)
diameter ConFlat Double Side Flanges as discussed above. By having
each of the first and the second reactive enter at its own port,
any possibility of reaction occurring in the inlet lines is
minimized. Further, the inlet line for the first reactive gas was
equipped with a "T" connection that allowed for the addition of
process nitrogen (N.sub.2) into the line to maintain a continuous
positive flow of gas out of the port to assure that there was no
back streaming of any of the second reactive gas into the supply
line for the first reactive gas.
[0049] As further protection against the inadvertent
cross-contamination of the inlet lines for the first and the second
reactive gases, the line for the first reactive gas was directed
through a normally closed valve, and the line for the second
reactive gas was directed through a normally open valve. These
control ports two valves were set up to be activated in tandem by
the same switch to assure that the two lines could not both be
adding precursor gases to the reactor at the same time.
[0050] Each of the lines was secondarily controlled on and off by a
separate valving system equipped with an in-line needle valve of
the SS Metering Bellows-Sealed Valve type to precisely control the
rate of flow of each of the precursor gases. Upstream of each of
these metering valves was a flow control valve commercially
available as 316 L VIM/VAR UHP Diaphragm-Sealed Valve, commercially
available from Swagelok Company of Solon, Ohio. Upstream of each of
these flow control valves was a reactive gas supply tank in the
form of a 300 mL capacity stainless steel bubbler, commercially
available as catalog no. Z527068 from Sigma-Aldrich, of St. Louis,
Mo.. This reactor/apparatus as described above was equipped with
diverse band heaters, heating tapes and cartridge heaters of
conventional types to control the temperatures of the reactor and
its gas supplies.
Example 1
[0051] Each of the double-sided flanges of the reactor was used to
support a disc cut from the porous polypropylene membrane discussed
above as Substrate A. Each of the three samples of the discs were
placed inside the reactor by attaching the discs to the copper
gaskets with double stick tape and placing the copper gaskets in
the normal sealing locations between the 6 inch (15.24 cm) diameter
ConFlat Double Side Flanges. As the reactor was sealed together and
tightened to form the reactor body, the ConFlat Double Side Flange
seals penetrated the membranes and formed an air tight seal via the
conventional copper gasket sealing mechanism. This sealed reactor
wall also helped to hold the membranes in place, and sealed the
edges of the membranes to prevent any of the reactive gases from
bypassing the membranes.
[0052] The reactor with the membranes in place was then attached to
the vacuum and gas handling systems as previously described above.
The first reactive gas supply tank was filled with
trimethylaluminium (TMA) 97%, commercially available as catalog
number 257222 from Sigma-Aldrich of St. Louis, Mo. The second
reactive gas supply tank was filled with ACS reagent water
commercially available as catalog number 320072 from Sigma-Aldrich.
The system was slowly put under vacuum via the vacuum bypass valve
to a pressure of between 1 to 10 ton. Once the vacuum was fully
drawn, and with the vacuum system still operating, the reactor was
flushed with a N.sub.2 purge at a flow rate of 10 to 25 sccm to
remove residual excess water and atmospheric gases and/or
contaminants. While this was occurring, the reactor, first and
second inlet lines, and purge gas lines were heated to 50.degree.
C. with the heaters. The first gas supply tank was similarly heated
to 30.degree. C.
[0053] After the system had been purged and the heaters had
stabilized at their respective set points, the first reactive gas
was released from the first reactive gas supply tank. The needle
valve on the first reactive gas line was adjusted so that the gas
flow, given the influence of the vacuum system, corresponded to an
N.sub.2 equivalent flow rate of 1 to 25 sccm flowing through the
discs to the exit. After the first reactive gas had fully saturated
the surfaces of the three discs (as detected by the RGA with the
presence of the precursors and the reduction of byproduct gases
exiting the final membrane), the flow of that the first reactive
gas was terminated and the system was again flushed with a N.sub.2
purge at a flow rate of 10 to 25 sccm. Once the purge was complete,
the second reactive gas was released from the second supply tank in
a similar manner (albeit a different port) until once again the
three discs were fully saturated. Another flush with a N.sub.2
purge at a flow rate of 10 to 25 sccm was performed. This cycle of
additions, i.e., first reactive gas-purge-second reactive
gas-purge) was continued the discs had undergone 35 iterations.
[0054] At the completion of each iteration, the pressure
differential within the reactor between the inlet and the outlet
sides of the discs were observed at the end of the final purge with
dry nitrogen. This data was recorded to determine the delta
Pressure being caused by the addition of aluminum oxide throughout
the membrane at a consistent gas flow rate. It was discovered that
as the half cycles progressed there was a detectable increase in
pressure across the membranes for the process gas. This increase in
delta pressure is illustrated by the graph shown in FIG. 2.
[0055] After the 35 iterations had been performed, the reactor was
opened and the surface energy of each of the three discs of Sample
A was assessed. Each disc was found to have a surface energy over
86 dyne/cm, indicating a high degree of hydrophilicity.
Example 2
[0056] An experiment was performed generally according to the
procedure of Example 1, except that the substrate used was
Substrate B instead of Substrate A; the reactor, the first and
second inlet lines, and purge gas lines were heated to 60.degree.
C. with the heaters; and the number of iterations was 20 instead of
35. After the 20 iterations had been performed, the reactor was
opened and the surface energy of each of the three discs of Sample
B was assessed. Each disc was found to have a surface energy over
86 dyne/cm, indicating a high degree of hydrophilicity.
Example 3
[0057] An experiment was performed generally according to the
procedure of Example 1, except that the substrate used was
Substrate C instead of Substrate A; the reactor, the first and
second inlet lines, and purge gas lines were heated to 60.degree.
C. with the heaters; and the number of iterations was 17 instead of
35. After the 17 iterations had been performed, the reactor was
opened and the surface energy of each of the three discs of Sample
C was assessed. Each disc was found to have a surface energy over
86 dyne/cm, indicating a high degree of hydrophilicity.
Example 4
[0058] An experiment was performed generally according to the
procedure of Example 1, except that the substrate used was
Substrate D instead of Sample A; the reactor was heated to
60.degree. C. with the heaters; the first and second inlet lines
and purge gas lines were heated to 70.degree. C. with the heaters;
and the number of iterations was 20 instead of 35. After the 20
iterations had been performed, the reactor was opened. An X-ray
analysis was performed to demonstrate that the substrate had been
coated.
Example 5
[0059] An experiment was performed generally according to the
procedure of Example 1, except that the substrate used was
Substrate E instead of Sample A; the reactor was heated to
60.degree. C. with the heaters; the first and second inlet lines
and purge gas lines were heated to 70.degree. C. with the heaters;
and the number of iterations was 20 instead of 35. After the 20
iterations had been performed, the reactor was opened. An X-ray
analysis was performed to demonstrate that the substrate had been
coated.
[0060] The complete disclosures of the publications cited herein
are incorporated by reference in their entirety as if each were
individually incorporated. Various modifications and alterations to
this invention will become apparent to those skilled in the art
without departing from the scope and spirit of this invention. It
should be understood that this invention is not intended to be
unduly limited by the illustrative embodiments and examples set
forth herein and that such examples and embodiments are presented
by way of example only with the scope of the invention intended to
be limited only by the claims set forth herein as follows.
* * * * *