U.S. patent application number 12/525658 was filed with the patent office on 2010-02-11 for membrane vapour concentrator.
This patent application is currently assigned to SABAN VENTURES PTY LIMITED. Invention is credited to Michael Potas, Ron Weinberger.
Application Number | 20100034697 12/525658 |
Document ID | / |
Family ID | 39673570 |
Filed Date | 2010-02-11 |
United States Patent
Application |
20100034697 |
Kind Code |
A1 |
Weinberger; Ron ; et
al. |
February 11, 2010 |
MEMBRANE VAPOUR CONCENTRATOR
Abstract
Apparatus for concentrating a vapor including an optional
vaporizer, a vapor flow conduit; a counter flow conduit; and an
optional humidity controller; wherein at least a portion of the
vapor flow conduit and counter-flow conduit define respective
opposed sides of a membrane. Also, a method of producing a
concentrated active from a solution including an active in a
solvent and having a first active-to-solvent ratio, the method
comprising the steps of: (1) vaporizing the solution to form a
vapor wherein the concentration of active is at about said first
ratio, (2) providing a flow of the vapor to a first side of a
membrane; and (3) providing an alternate flow of a gas to a second
side of the membrane whereby to increase said first
active-to-solvent ratio on the first side to a second
active-to-solvent ratio greater than the first active-to-solvent
ratio.
Inventors: |
Weinberger; Ron;
(Alexandria, AU) ; Potas; Michael; (Alexandria,
AU) |
Correspondence
Address: |
SENNIGER POWERS LLP
100 NORTH BROADWAY, 17TH FLOOR
ST LOUIS
MO
63102
US
|
Assignee: |
SABAN VENTURES PTY LIMITED
Alexandria
AU
|
Family ID: |
39673570 |
Appl. No.: |
12/525658 |
Filed: |
January 31, 2008 |
PCT Filed: |
January 31, 2008 |
PCT NO: |
PCT/AU08/00108 |
371 Date: |
August 3, 2009 |
Current U.S.
Class: |
422/28 ; 159/31;
159/48.2 |
Current CPC
Class: |
C01B 15/013 20130101;
B01D 2311/13 20130101; A61L 2202/15 20130101; A61L 2202/24
20130101; A61L 2/20 20130101; A61L 2/28 20130101; A61L 2/208
20130101; B01D 61/36 20130101; B01D 61/362 20130101 |
Class at
Publication: |
422/28 ; 159/31;
159/48.2 |
International
Class: |
A61L 2/16 20060101
A61L002/16; B01D 61/36 20060101 B01D061/36 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 2, 2007 |
AU |
2007900503 |
Claims
1. Apparatus for concentrating a vapour comprising: a vapour flow
conduit; a counter-flow conduit; and wherein at least a portion of
said vapour flow conduit and said counter-flow conduit define
respective opposed sides of a membrane, wherein said apparatus
operates such that said membrane can be selected from a group
consisting of selective or non-selective membranes.
2. Apparatus according to claim 1 further comprising a vaporizer in
communication with the vapour flow conduit.
3. Apparatus according to claim 1 or 2 further comprising humidity
control means for controlling the humidity of a counter flow
entering the counter-flow conduit.
4. Apparatus according to any one of claims 1 to 3 comprising: a
plurality of alternating vapour flow conduits and corresponding
counter-flow conduits; and wherein at least a portion of said each
vapour flow conduit and an adjacent counter-flow conduit define
respective opposed sides of a membrane.
5. Apparatus according to any one of claims 1 to 4 wherein
alternating vapour flow conduits and counter-flow conduits are in a
layered configuration.
6. Apparatus according to any one of claims 1 to 4 wherein
alternating vapour flow conduits are in a concentric, coaxial
tubular arrangement.
7. Apparatus according any one of claims 1 to 3 for concentrating a
vapour comprising: a vapour flow conduit; at least two counter-flow
conduits; and wherein at least a portion of said vapour flow
conduit and said counter-flow conduits define respective opposed
sides of membranes, wherein said apparatus operates such that said
membrane can be selected from a group consisting of selective or
non-selective membranes.
8. Apparatus according to any one of claims 1-3 for concentrating a
vapour comprising at least two vapour flow conduits; an alternate
flow conduit; and wherein at least a portion of said counter-flow
conduit and said vapour flow conduits define respective opposed
sides of membranes, wherein said apparatus operates such that said
membrane can be selected from a group consisting of selective, or
non-selective membranes.
9. Apparatus according to any one of the preceding claims wherein
each vapour flow conduit comprises an inlet and an outlet, each
counter-flow conduit comprises an inlet and an outlet, and the
vapour flow and counter-flow are in the same or opposite
directions.
10. Apparatus according to any one of claims 1 to 7 wherein each
vapour flow conduit comprises an inlet and an outlet, and the
counter-flow conduit directs a counter flow in a direction at an
angle to the vapour flow direction.
11. A method of producing a concentrated active from a solution
comprising an active in a solvent and having a first active:solvent
ratio, said method comprising the steps of: (1) vaporizing the
solution to form a vapour wherein the concentration of active is at
about said first ratio, (2) providing a flow of the vapour to a
first side of a membrane; and (3) providing an alternate flow of a
gas to a second side of the membrane whereby to increase said first
active:solvent ratio on the first side to a second active:solvent
ratio greater than the first active:solvent ratio, wherein said
membrane is selected from a group consisting of selective or
non-selective membranes.
12. A method for concentrating a vapour comprising the steps of (1)
providing a flow of a vapour consisting of an active in a solvent
and having a first active:solvent ratio to a first side of a
membrane; and (2) providing an alternate flow of a gas to a second
side of the membrane whereby to increase said first active:solvent
ratio on the first side to a second active:solvent ratio greater
than the first active:solvent ratio, wherein said membrane is
selected from a group consisting of selective or non-selective
membranes.
13. A method according to claim 11 or 12 wherein the active is a
biocide and the concentrated vapour is used to disinfect and/or
sterilize an article.
14. A method according to any one of claims 11 to 13 wherein the
solvent is water.
15. A method according to any one of claims 11 to 14 wherein the
active is hydrogen peroxide or a peroxy compound.
16. A method according to according to any one of claims 11 to 15
wherein the first active to solvent ratio is below 35 wt %.
17. A method according to any one of claims 11 to 16 wherein the
second active:solvent ratio is above 60 wt %.
18. A method according to any one of claims 11 to 17 wherein the
counter-flow of gas is provided at a rate and for a time such that
the second ratio reaches an equilibrium ratio beyond which it will
not increase.
19. A method according to any one of claims 11 to 18 wherein the
gas is air or humidity conditioned air.
20. A method according to any one of claims 11 to 19 wherein the
fabric or membrane is a woven, or non-woven fabric, or a sheet or
film or a combination thereof and of a single layer or multilayer
construction.
21. A method according to any one of claims 11 to 20 wherein the
membrane is hydrophobic.
22. A method according to any one of claims 1 to 21 wherein the
membrane is Kimguard.
23. A method according to any one of claims 11 to 22 wherein the
membrane is suitable for pervaporation.
24. A method according to any one of claims 11 to 23 wherein the
vapour is an aqueous peroxide vapour having an initial
concentration of from 6%-35 wt % of peroxide.
25. A method according to according to any one of claims 11 to 24
wherein the membrane is selected to remove one or more vapours by a
process of pervaporation.
26. A method for disinfecting or sterilizing an article comprising
bringing a suitable biocidal solution concentrated by a method
according to any one of claims 9 to 25 into contact with the
article as a vapour.
27. A method for disinfecting or sterilizing an article comprising
the steps (1) vaporizing a solution consisting of an active in a
solvent and having a first active:solvent ratio, (2) providing a
flow of the vapour to a first side of a membrane; and (3) providing
an alternate flow of a gas to a second side of the membrane whereby
to increase said first active:solvent ratio on the first side to a
second active:solvent ratio greater than the first activer solvent
ratio, and (4) contacting the vapour from step 2 with the article
for a time sufficient to disinfect or sterilize it, wherein said
membrane is selected from a group consisting of selective or
non-selective membranes.
28. A method according to claim 27 when conducted at atmospheric
pressure or above.
29. A method according to claim 27 when conducted at below
atmospheric pressure.
30. A method according to according to any one of claims 27 to 29
wherein the counter-flow of gas is provided at a rate and for a
time such that the second ratio reaches an equilibrium ratio beyond
which it will not increase.
31. A method for disinfecting or sterilizing an article comprising
the steps of (1) enclosing the article inside a container having a
wall of which at least a part is a membrane; (2) providing a vapour
of an active in a solvent and having a first active:solvent ratio,
(3) providing, an alternate flow of a gas to a side of the membrane
external to the container whereby to increase the first
active:solvent ratio to a second active:solvent ratio greater than
the first active:solvent ratio, and produce a concentrated vapour;
and (4) allowing the article to remain in contact with the
concentrated vapour for a time sufficient to permit sterilization,
wherein said membrane is selected from a group consisting of
selective or non-selective membranes.
32. A method according to claim 31 wherein the membrane is
impenetrable by microorganisms and the article is sterilized and
stored sterile in the container.
Description
[0001] The present application claims priority to Australian Patent
Application No. 200700504, filed Feb. 2, 2007, and Patent
Cooperation Treaty International Application No. PCT/AU2008/000108
filed Jan. 31, 2008, which are incorporated by reference.
FIELD OF THE INVENTION
[0002] This invention relates to a method and apparatus for
concentrating vapor, such as may be used for example in
disinfecting or sterilizing a surface. The method and apparatus are
particularly suited for disinfecting or sterilizing medical
instruments but are not limited to that use.
BACKGROUND OF THE INVENTION
[0003] It is highly desirable to have sterilization processes and
apparatus that avoid the need for temperatures above 60.degree. C.
while achieving the highest possible efficacy in pathogen
destruction, especially when treating occluded, mated and lumen
surfaces.
[0004] The use of high temperatures leads to complex and costly
sterilization instruments, and more importantly, can damage many
materials. This is a problem both in terms of patient safety and
apparatus cost.
[0005] It is desirable that the disinfecting methods use hydrogen
peroxide. Hydrogen peroxide at low concentrations is safe to
transport, sell, and handle and is extremely well known, with
little or no regulatory barriers to its use. However, there are
problems with those methods requiring high concentration hydrogen
peroxide as a starting material. For example, commercial vapor and
plasma processes use as a starting material corrosive and
irritating 60% peroxide solutions requiring special packaging and
handling precautions.
[0006] Any discussion of the prior art throughout the specification
should in no way be considered as an admission that such prior art
is widely known or forms part of common general knowledge in the
field.
[0007] Unless the context clearly requires otherwise, throughout
the description and the claims, the words `comprise`, `comprising`,
and the like are to be construed in an inclusive sense as opposed
to an exclusive or exhaustive sense; that is to say, in the sense
of "including, but not limited to".
BRIEF STATEMENT OF INVENTION
[0008] According to a first aspect, the present invention provides
apparatus for concentrating a first vapor in a mixture of a first
vapor and at least a second vapor, the method comprising: a vapor
flow conduit; a counter-flow conduit; wherein at least a portion of
said vapor flow conduit and said counter-flow conduit define
respective opposed sides of a membrane; and wherein: i) the
membrane is selected to favor diffusion of the first vapor over at
least the second vapor; and/or ii) the operating conditions of the
apparatus can be selected to favor diffusion of the first vapor
over at least the second vapor.
[0009] The vapor flow and counter-flow may be in opposite
directions, the same direction, or any other direction, e.g.,
perpendicular flows.
[0010] Preferably, the operating conditions, which can be selected
to favor diffusion of one vapor over one or more other vapors in
the mixture of vapors, include temperature or pressure control on
either side of the membrane, or humidity or gas flow on an opposite
side of the membrane to the mixture of vapors.
[0011] According to a second aspect, the present invention provides
apparatus for concentrating a first vapor in a mixture of a first
vapor and at least a second vapor, the method comprising: a
plurality of alternating vapor flow conduits and corresponding
counter-flow conduits; and wherein at least a portion of each vapor
flow conduit and an adjacent counter-flow conduit define respective
opposed sides of a membrane; and wherein: i) the membrane is
selected to favor diffusion of the first vapor over at least the
second vapor; and/or ii) the operating conditions of the apparatus
can be selected to favor diffusion of the first vapor over at least
the second vapor.
[0012] The alternating vapor flow conduits and counter-flow
conduits may be in a layered configuration. Alternatively, they
maybe in a concentric, coaxial tubular arrangement.
[0013] Each vapor flow conduit comprises an inlet and an outlet.
Each counter-flow conduit comprises an inlet and an outlet.
Preferably, the vapor flow and counter-flow are in opposite
directions. However, they may in the same direction, or any other
direction, e.g., perpendicular flow.
[0014] Preferably the apparatus further comprises a vaporizer in
communication with the vapor flow conduit.
[0015] Also preferably the apparatus further comprises a humidity
control means for controlling the humidity of a counter-flow
entering the counter-flow conduit.
[0016] According to a third aspect, the present invention provides
apparatus for concentrating a first vapor in a mixture of a first
vapor and at least a second vapor, the method comprising: a vapor
flow conduit; at least two counter-flow conduits; and wherein at
least a portion of said vapor flow conduit and said counter-flow
conduits define respective opposed sides of membranes; and wherein:
i) the membranes are selected to favor diffusion of the first vapor
over at least the second vapor; and/or ii) the operating conditions
of the apparatus can be selected to favor diffusion of the first
vapor over at least the second vapor.
[0017] According to a fourth aspect, the present invention provides
apparatus for concentrating a first vapor in a mixture of a first
vapor and at least a second vapor, the method comprising: at least
two vapor flow conduits; a counter-flow conduit; and wherein at
least a portion of said vapor flow conduit and said counter-flow
conduits define respective opposed sides of membranes; and wherein:
i) the membranes are selected to favor diffusion of the first vapor
over at least the second vapor; and/or ii) the operating conditions
of the apparatus can be selected to favor diffusion of the first
vapor over at least the second vapor.
[0018] In one preferred embodiment, each vapor flow conduit
comprises an inlet and an outlet, each counter-flow conduit
comprises an inlet and an outlet, and the vapor flow and
counter-flow are in the same or opposite directions.
[0019] In another preferred embodiment each vapor flow conduit
comprises an inlet and an outlet, and the counter-flow conduit
directs a counter flow in a direction at an angle to the vapor flow
direction.
[0020] According to a fifth aspect, the invention provides a method
of producing a concentrated active from a solution comprising an
active in a solvent and having a first active-to-solvent ratio,
said method comprising the steps of: (1) vaporizing the solution to
form a vapor wherein the concentration of active is at about said
first ratio; (2) providing a flow of the vapor to a first side of a
membrane; and (3) providing an alternate flow of a gas to a second
side of the membrane whereby to increase said first
active-to-solvent ratio on the first side to a second
active-to-solvent ratio greater than the first active-to-solvent
ratio.
[0021] According to a sixth aspect, the present invention provides
a method for concentrating a vapor comprising the steps of: (1)
providing a flow of a vapor of an active in a solvent and having a
first active-to-solvent ratio to a first side of a membrane; and
(2) providing an alternate flow of a gas to a second side of the
membrane whereby to increase said first active-to-solvent ratio on
the first side to a second active-to-solvent ratio greater than the
first active-to-solvent ratio.
[0022] The concentrated vapor is preferably used to disinfect
and/or sterilize an article.
[0023] The vapor is preferably a vapor of water and a biocide,
i.e., the solvent is preferably water. Most preferably, the biocide
or active is a peroxy compound, most preferably hydrogen peroxide.
The present invention encompasses any situation where the
active-to-solvent ratio is increased. The active may be present in
very small quantities, such as 0.1% (or less) of the total active
plus solvent and concentrated up to the point where all or
substantially all of the solvent is removed, i.e., 100% active.
Hydrogen peroxide is typically sold as a 30 wt % to 35 wt %
solution in water, so in one embodiment the first active to solvent
ratio is preferably below 35 wt %, and more preferably about 30 wt
%.
[0024] The second active-to-solvent ratio may be any level up to
and including 100%. In some cases, it is preferably above 60 wt %,
and more preferably about 70 wt %, and in some preferred
embodiments, even above 80 wt % or 90 wt %. The counter-flow of gas
is preferably provided at a rate and for a time such that the
second ratio is not capable of further increase.
[0025] For preference the gas is air, more preferably humidity
conditioned air.
[0026] The semi-permeable fabric or membrane may be a woven, or
non-woven fabric, or it may be a sheet or film or a combination
thereof and may be of a single layer or multilayer
construction.
[0027] The term "membrane" is used herein where the context permits
to include all such fabrics and membranes having the selected
properties. The membrane may be hydrophobic or hydrophilic in
nature.
[0028] In this specification where the context permits references
to a fabric or membrane include fabrics or membranes suitable for
pervaporation as well those only suitable for simple permeation,
and references to permeation include references to pervaporation.
Other membranes than those described and membranes may be used and
may include membranes suitable for pervaporation, or other
permeable or semi-permeable membranes. A highly preferred membrane
is Kimguard.TM. sheet.
[0029] In a highly preferred embodiment a peroxide solution having
an initial concentration of at least 3% to 6%, preferably 20% to
35%, and more preferably 30% to 35%, is vaporized.
[0030] Water vapor permeates through the membrane, leaving peroxide
vapor behind. The peroxide in the vapor becomes more
concentrated.
[0031] The more concentrated peroxide vapor is significantly more
effective as a sterilant than prior art hydrogen peroxide vapor
possibly because a much higher concentration of sterilant is
obtainable per unit volume.
[0032] Air permeating into the vapor flow conduit is sterile
because the membrane is not penetrable by micro-organisms.
[0033] According to a seventh aspect, the invention provides a
process according to any one of the preceding aspects wherein the
membrane is selected to remove one or more vapors by a process of
pervaporation.
[0034] Although the invention is herein described with reference to
hydrogen peroxide as the biocide, the invention is equally
applicable when the biocide was another peroxide or peroxy
compound, or could be used with other known vaporizable biocides or
biocides when dissolved in suitable solvents (which need not be
aqueous). Preferably the vapor is subsequently removed by an
exterior current of air (or other fluid) adjacent the membrane
exterior.
[0035] According to an eighth aspect, the invention provides a
method for disinfecting or sterilizing an article comprising the
steps of: (1) vaporizing a solution consisting of an active in a
solvent and having a first active-to-solvent ratio: (2) providing a
flow of the vapor to a first side of a membrane; and (3) providing
an alternate flow of a gas to a second side of the membrane whereby
to increase said first active-to-solvent ratio on the first side to
a second active-to-solvent ratio greater than the first
active-to-solvent ratio; and (4) contacting the vapor from step 2
with the article for a time sufficient to disinfect or sterilize
it.
[0036] In one preferred embodiment the method is conducted at
atmospheric pressure or above.
[0037] In another preferred embodiment the method is conducted
below atmospheric pressure.
[0038] Preferably the counter-flow of gas is provided at a rate and
for a time such that the second ratio reaches an equilibrium ratio
beyond which it will not increase.
[0039] According to a ninth aspect, the invention provides a method
for disinfecting or sterilizing an article comprising the steps of:
(1) enclosing the article inside a container having a wall of which
at least a part is a membrane; (2) providing a vapor of an active
in a solvent and having a first active-to-solvent ratio; (3)
providing an alternate flow of a gas to a side of the membrane
external to the container whereby to increase the first
active-to-solvent ratio to a second active-to-solvent ratio greater
than the first active-to-solvent ratio, and produce a concentrated
vapor; and (4) allowing the article to remain in contact with the
concentrated vapor for a time sufficient to permit
sterilization.
[0040] Preferably the membrane is impenetrable by microorganisms
and the article is sterilized and stored sterile in the
container.
[0041] In preferred embodiments a hydrogen peroxide solution in
water of for example 35% concentration is firstly vaporized and
then the vapor is concentrated in one chamber by removal of water
through a membrane. The concentrated vapor is then admitted to
another chamber which is desirably a bag or other container having
a membrane as defined as a wall or part thereof which is then
sealed. This allows the article to be sterilized and stored sterile
in the second container and permits removal of residual hydrogen
peroxide and water. Preferably the invention provides in
particular, a vapor having a peroxide concentration greater than 70
wt % and a water concentration less than 30 wt %.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] FIG. 1 is a reproduction of a figure from U.S. Pat. No.
4,797,255 which shows (curve A) how the boiling point of a
water/peroxide mixture changes with concentration at atmospheric
pressure and (curve B) how the gas composition changes.
[0043] FIG. 2 is diagram of a first simple embodiment of the
present invention.
[0044] FIG. 3 is a diagram of a sterilizing apparatus showing the
pre-concentrator of the present invention.
[0045] FIG. 4 is a more detailed schematic diagram of a sterilizing
apparatus showing the pre-concentrator of the present
invention.
[0046] FIG. 5 shows a further embodiment of the present
invention.
[0047] FIG. 6 shows flow patterns of vapor and counter flow in an
embodiment of the present invention.
[0048] FIG. 7 shows the plates that may be used to separate
membranes in those embodiments of the present invention that use
stacked arrays.
[0049] FIG. 8 shows results from a membrane concentrator of the
present invention.
[0050] FIG. 9 shows an ultrasonic probe in disinfecting arrangement
with an apparatus of the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0051] The invention will now be described in the context of
sterilization and disinfection, but it will be appreciated that the
pre-concentrators and pre-concentration methods of the present
invention can be used in a variety of fields where concentrated
vapors are desired, e.g., drug delivery, painting/printing, food
preparation, materials fabrication, and the like. For example, a
number of such processes have been described (U.S. Pat. No.
6,451,254, U.S. Pat. No. 6,673,313 and U.S. Pat. No. 6,655,426) all
of which require or involve concentrating a hydrogen peroxide
solution by lowering the pressure to preferentially evaporate water
and removing the water through a vacuum pump prior to vaporizing
the solution.
[0052] The general pre-concentration process of the present
invention takes place in the context of the following, and can be
seen with reference to FIG. 3. An article to be sterilized 1 is
placed into a sterilization chamber 2. The sterilization chamber 2
may be any suitable container, but advantageously is a bag made
from a membrane, or a sealed container having a window of a
membrane 3.
[0053] A pre-concentrator chamber of the present invention 4 is
connected upstream from the sterilization chamber 2. The
sterilization chamber 2 and pre-concentrator 4 are connected such
that flow between the pre-concentrator and sterilizing chamber can
be opened or closed by way of a valve 5.
[0054] A vaporizer 6 is connected upstream from the
pre-concentrator chamber. A hydrogen peroxide solution having a
starting concentration preferably of around 30% to 35% is
vaporized.
[0055] In the vaporizer, the aqueous hydrogen peroxide is heated,
for example, by way of an electrically heated surface, such as a
hot plate, and is then moved away from the vaporization area, for
example, by an impeller, blower, or the like. Alternatively, if the
aqueous hydrogen peroxide is applied by a jet directed onto the hot
plate, the jet may move the vapor. Alternatively, the vapor may be
drawn from the vaporizer by a vacuum.
[0056] The vaporizer 6 may be fed with sterilant solution on a
continuous or intermittent basis from a bulk supply 7, or may be
provided with a single shot dosing system for example a cartridge
providing sufficient solution for one or a plurality of
sterilization cycles. Alternatively, a sterilant solution may be
provided pre-packed in a capsule which may be placed in an adapted
vaporizer so the capsule is in contact with the heating element of
the vaporizer. In this case means are provided for piercing the
capsule so that it is able to release the solution as a vapor.
[0057] The unconcentrated hydrogen peroxide vapor is then propelled
into the pre-concentrator 4 by means of a fan 8 upstream from the
vaporizer 6. The vapor formed by the vaporizer 6 is entrained in a
gas stream which in the preferred embodiment is air. It is a
significant advantage of preferred embodiments of the invention
over prior art that they do not require a source of filtered
sterile air. Instead the invention is able to draw non-sterile air
from the sterilization chamber, and sterilize it while
recirculating it in use. However, if preferred, aseptic filtered
air could be employed. The gas stream is not necessarily air, and
could for example be an inert gas such as nitrogen, or argon, or
could be oxygen or ozone.
[0058] In general terms, the pre-concentrator 4 works by exposing
the vapor to one face 10 of a membrane 9 while an air current moves
across the other face 11 of this membrane. This leads to
preferential evaporation of the water from the vapor, causing it to
become more concentrated with respect to hydrogen peroxide. As a
result of the preferential evaporation of water, the vapor inside
the pre-concentrator 4 become more concentrated with respect to
hydrogen peroxide with the concentrations approaching 60% or
upwards.
[0059] Once formed, the highly concentrated vapor then makes
contact with the article to be sterilized.
[0060] There are two possible preferred modes of operation of the
pre-concentrator.
[0061] In the first operating mode, which is a batch-wise
concentration process, the pathway between the pre-concentrator 4
and sterilizing chamber 2 is shut and a vapor of 35% hydrogen
peroxide in water is driven into the pre-concentrator chamber 4.
The pre-concentrator chamber is then isolated (by shutting both
valves 5 and 12) and the vapor in the pre-concentrator 4 is then
concentrated. Concentration in the pre-concentrator takes place
until the maximum concentration of peroxide is achieved. Once this
maximum concentration is achieved, the pathway between the
pre-concentrator and sterilizing chamber is opened by opening valve
5 and the concentrated vapor is introduced into the sterilization
chamber 2.
[0062] In the second alternative operating mode, which is a
continuous concentration process, the pathway between the
pre-concentrator 4 and the sterilization chamber 2 is left open. A
vapor of a solution of 35% hydrogen peroxide in water enters the
pre-concentrator chamber 4 and passes continuously through the
pre-concentrator with fan 8 propulsion. As the vapor passes through
the pre-concentrator 4, water is preferentially removed. Residence
time of the vapor in the pre-concentrator is preferably such that
the maximum possible concentration of peroxide is achieved by the
time it exits the pre-concentrator.
[0063] The vapor may be introduced into the pre-concentrator 4
continuously or intermittently, for example, 2 seconds on/18
seconds off; or 5 seconds on/15 seconds off; over a period of, for
example, 2 minutes.
[0064] However, regardless of whether batch-wise mode a) or
continuous mode b) is employed, or even should some combination of
continuous or batch wise modes be used, the vapor that exits the
pre-concentrator 4 and enters the sterilization chamber 2 is
preferably at its maximum achievable hydrogen peroxide
concentration.
[0065] Once the concentrated vapor is introduced to the
sterilization chamber 2, it contacts the article to be sterilized 1
and acts upon the pathogens at the surface. The sterilizing chamber
2 may then be sealed from the pre-concentrator 4. The concentrated
vapor is then allowed to contact the article to be sterilized. The
article to be sterilized can be stored in the sterilization chamber
until needed. This also permits removal of residual hydrogen
peroxide and water.
[0066] To expand on each of the steps, and shown in FIG. 14, the
cycle commences with vaporization of 27% to 35% hydrogen peroxide
inside a vaporization chamber 6. The vaporizer may function
continuously or according to an appropriate duty cycle such that
vaporization is intermittent. The vapor has the same composition as
the bulk solution from which it was derived.
[0067] Once produced, the vapor is transported by a blower fan 8
into the membrane concentrator system 4 where it is concentrated by
means of evaporation.
[0068] The membrane concentrator 4 is preferably a multi-layered
device where vapor flows over membrane layers which have an
alternate airflow on the other side. Selective removal of a portion
of the water vapor occurs in the membrane concentrator due to the
differential partial pressures of water and hydrogen peroxide. The
vapor exits the concentrator either at a predetermined
concentration or "terminally" concentrated such that no further
concentration of hydrogen peroxide will occur.
[0069] In one simple embodiment, shown in FIG. 2, the membrane
concentrator is a modular, stackable assembly consisting of 4 main
components--flow layer, end plate, tie-rod, and membrane sheet.
FIG. 5 shows a preferred stack of concentrator modules.
[0070] The flow layers 10 and 11 are defined by thin, square or
rectangular plates 12 with a large open area inside and four slots
(galleries) running parallel to the outer edges, two of which are
connected to the inner space via slots. The orientation of the flow
layers (when using square sections), determines the number of
layers common to any particular gallery. Hence two distinct flow
lines may operate a single assembly through the method of
assembly.
[0071] The end plates 13 allow connection of external tubing or
devices to the membrane assembly and each end plate has two
connection points which correspond to two gallery slots. The slots
on these end plates form a manifold which directs flow up one
particular gallery per connection and the connections are offset 90
degrees from one another to ensure they access different
galleries.
[0072] When five flow layers, for example are stacked atop one
another with alternate orientations, i.e., 90 degrees to each
other, and separated by sheets of membrane material, they form two
groups of flow layers, one having two flow layers 15 and the other
having three separate flow layers 16 within the block. These flow
layers are assigned to either vapor (15 in the present case) or
crossflow/counterflow (16 in the present case) connections and
through regulation of their flow rates, controlled diffusion is
possible.
[0073] The tie-rods are used to compress the layers between the end
plates and create a vapor seal, although any design allowing the
blocks to fit together in suitable sealed arrangement may be used.
The membrane material 9 also acts as a gasket between the
layers.
[0074] The vapor pressure of hydrogen peroxide at ambient
temperatures is negligible, and water preferentially evaporates in
the membrane concentrator. However, as a precaution against any
hydrogen peroxide flow exiting the system, the counter flow is
taken directly into the catalytic destructor module where it is
safely treated.
[0075] The membrane 9 in the present example is preferably made of
Kimguard.TM. sheet, a three layer, non-limiting laminate fabric
using polypropylene and having an inner layer which is hydrophobic
and resistant to bacterial penetration. The two outer layers
provide abrasion resistance and strength. As a multi layered fabric
it has no actual pore size, but the fabric is permeable by virtue
of microscopic channels which provide a tortuous path limiting
passage of particles to those of less than 0.2 micron, i.e., it is
impermeable to micro-organisms below 0.2 microns. This fabric
allows hydrogen peroxide vapor or water vapor to permeate through
the channels of the fabric. The channels do not permit passage of
bacteria into the chamber. Kimguard sheet has a hydrostatic
repellency of 3.8 kPa (measure of hydrophobicity) and a cross
dimensional tensile load of 70 Newtons and a machine directional
tensile load of 130 Newtons.
[0076] The membrane 9 may be any other suitable membrane which
facilitates the removal of water while being impermeable by
micro-organisms. Other fabrics and membranes which are permeable by
water vapor and hydrogen peroxide vapors and impenetrable by
bacteria may be used, for example Tyvek.TM. sheet and Spunguard.TM.
sheet (However, Kimguard.TM. sheet has been found to be 2-3 times
more permeable to hydrogen peroxide vapor than Tyvek.TM. under the
conditions in which it is used here. As will be discussed
hereinafter other membrane materials such as Nafion.TM. sheet
(which is hydrophilic) and the like may also be employed.
[0077] Nafion.TM. is a copolymer of tetrafluoroethylene and
perfluoro 3,6, dioxa-4-methyl-octene-sulphonic acid. Such materials
are hydrophilic and have a very high water of hydration. Nafion.TM.
sheet is able to absorb 22% by weight of water. In this variation
the absorption proceeds as a first order kinetic reaction. Water
molecules pass through the membrane and then evaporate into the
surrounding air until equilibrium with the external humidity is
reached in a continuous process called pervaporation. An exterior
current flow of air over the external side of the membrane provides
rapid removal of the moisture from the outside surface and speeds
the pervaporation process. Unlike simple permeation wherein the
molecules merely diffuse through the open pores, in pervaporation
the membrane is active in selectively drawing molecules from one
side of the membrane to the other, and may do so at differential
rates for differing types of chemical molecule.
[0078] In the embodiments described above the sterilizing agent is
a solution of hydrogen peroxide as a 35 wt % solution in water
which acted as the solvent. Water is the preferred solvent for use
with peroxide. Water boils at 100.degree. C. while hydrogen
peroxide boils at above 151.degree. C. at atmospheric pressure.
Hydrogen peroxide boils at 151.4.degree. C. at 760 mm. FIG. 1 taken
from U.S. Pat. No. 4,797,255 shows (curve A) how the boiling point
at atmospheric pressure of a water/peroxide mixture changes with
concentration and (curve B) how the gas composition changes. As is
shown, pure water boils at 100.degree. C. at atmospheric pressure.
It is evident from FIG. 1 that the concentration of hydrogen
peroxide in the vapor at below 100.degree. C. is negligible at
atmospheric pressure.
[0079] Besides water, the solvent could for example be an aqueous
or non-aqueous alcohol chosen in combination with the sterilizing
agent to be used. The addition to water of ethyl alcohol results in
an azeotropic mixture which lowers the boiling point of the solvent
and this enables the water to be "flashed" off at lower
temperatures than would otherwise be possible. The addition of
other azeotropic agents would be equally beneficial. The use of
azeotropes to facilitate the removal of a solvent such as water
from the vapor is within the scope of the invention. It is
envisioned that for some biocides non-aqueous solvents or a
combination of suitable solvents could be employed.
[0080] In the case of hydrogen peroxide, as the water flashes off,
the concentration of the sterilizing agent increases. If a 35%
peroxide solution is used in the invention as the starting
material, the resultant vapor will have a concentration of for
example 60% to 80% peroxide. This has the advantage that the
starting material can be handled relatively safely, that
concentration occurs during the process and that thereafter there
is no further need to handle the peroxide.
[0081] Solutions of a lower or greater concentration than 35% can
be used as a starting material and excellent results have been
obtained with hydrogen peroxide solutions of 1% or 3% as well as
with solutions of 40%. While preferred embodiments described have
employed aqueous solutions of hydrogen peroxide as the sterilizing
agent, solutions of other peroxides and peroxy compounds can be
employed as well as solutions of peroxy complexes (including non
water soluble complexes in organic solvents). Sterilizing agents
other than peroxides may also be used in the invention, including
without limitation halo compounds, phenolic compounds, halogen
phenolic compounds and other known biocides, with appropriate
choice of solvent.
[0082] In an example in which the article to be disinfected is the
part of an ultrasonic probe 20, for example a probe of a type
insertable into a body cavity for diagnostic purposes, the part of
the probe 20 to be treated is enclosed in a chamber 2 (as
exemplified in FIG. 9). In this case the chamber is a specially
shaped chamber designed so that the whole article need not be in
the chamber, only that part of the probe which is to be treated
being enclosed. The probe can be suspended inside the chamber by
means of a seal around the gland where the power cord enters the
probe.
[0083] The vapor is then transported into chamber 2 where it is
applied to a target surface. The ultrasound device may be inserted
into the chamber via any of the panels on the device. One possible
entrance is from the top via a screw top lid into which the cord of
the device is damped and held in place on insertion into the
chamber. Passage of the vapor from the concentrator to the chamber
is regulated by a check valve 5. Check valves 5 and 12 can control
whether the device operates batchwise, continuously or by some
combination of both.
[0084] If the device operates batchwise, the valve 5 is opened at
the appropriate time after the concentration has occurred.
[0085] If the device is operated continuously, the valve remains
open, with the flow rates and residence times of the vapor
calibrated beforehand to be at a maximum when exiting the
chamber.
[0086] Typically, the chamber 2 is constructed of a heat conductive
metal such as stainless steel or aluminum. Various coating may be
applied to the interior of the chamber such as Teflon to reduce the
risk of peroxide breakdown. The disinfection chamber is
electrically heated using heater trace wire applied to the
conductive metal surface. Alternatively, or in addition, heated air
can be blown into chamber. Chamber atmosphere to supply the blower
is made-up from another chamber connection which is placed on the
opposite side of the chamber to the inlet. The chamber itself is
isolated from the generation and recirculation circuit by means of
valves which engage once the vaporization cycle is complete (about
1-1.5 min). This isolation from the adjoining circuit is called
"suspended time" or more commonly "hold" time.
[0087] The surface of the object 1 to be treated is exposed to the
vapor for a time sufficient to sterilize the surface. The resulting
concentrated vapor is highly effective at penetrating mated
surfaces, and treating occluded surfaces which are not directly
exposed.
[0088] The chamber 2 may be formed fully of a membrane or fabric or
may have a wall of which at least a part is a membrane or fabric
may be of any suitable shape and design having regard to the
requirements of the process herein described and can be sealed in
any manner impenetrable by micro organisms. Other membranes or
fabrics can be selected based on the teaching herein provided. The
container may be permanently connected to the vaporizer circuit or
may be able to be connected and disconnected by a tube and spigot
connection, by suitable connectors or other means.
[0089] Once the suspended time is complete (approx 1-2 minutes),
the system moves into catalytic destruction mode or simply "empty".
It is in this cycle that a suction fan engages which pilots (opens
under pressure) a check valve that connects to the chamber while
another valve allows fresh air to enter the chamber at a controlled
rate. This cycle moves the vapor into the catalytic destructor
module where a catalyst is used to convert the hydrogen peroxide
into harmless water vapor and oxygen. The catalytic destructor
module is composed of metal oxide baked ceramic honeycomb layers
sandwiching similarly treated ceramic beads packaged in a suitable
container. The amount of catalyst is proportional to the amount of
peroxide extracted from the chamber as well as the flow rate from
the chamber. Completion of this cycle takes approximately 1 minute
and upon completion, the chamber may be accessed to retrieve the
disinfected target device. It is understood that the time to
achieve sterilization is more onerous and may take significantly
longer.
[0090] In some preferred embodiments, the vapor density in the
vapor passing from the pre-concentrator to the sterilization
chamber may be measured by passing an infra red beam across the
connecting conduit to a detector and measuring the beam
attenuation. The infra red is preferably of a frequency which
registers peroxide vapor if any. A knowledge vapor composition,
temperature and residence time allows certification of the result
if desired.
[0091] The pre-concentrator can be operated in such a manner that
it always outputs vapor comprising peroxide at a predetermined
theoretical maximum concentration, thereby avoiding the need to
determine the concentration of peroxide at any point of the
sterilizing process.
[0092] Although the invention has been herein described with
reference to hydrogen peroxide as the sterilizing or disinfection
agent, the invention could use other peroxides, peroxy-compounds,
or complexes of either. Other classes of biocide could be used
including without limitation halogenated biocides, phenolic
biocides and quaternary compound biocides and it may be
advantageous to use solvents other than water. Likewise, although
the invention has been herein exemplified primarily with reference
to starting solutions having 35% peroxide, other starting
concentrations can be employed, although concentrations between
about 20% and 35% are preferred.
[0093] The principles herein taught could be applied to concentrate
the peroxide in such vapor processes by permeation or pervaporation
through a membrane, without the need for pressure reduction.
* * * * *