U.S. patent application number 09/579676 was filed with the patent office on 2002-04-25 for carbon dioxide cleaning and separation systems.
Invention is credited to Givens, Ramone D., McClain, James B., Romack, Timothy J., Stewart, Gina M..
Application Number | 20020048629 09/579676 |
Document ID | / |
Family ID | 22093759 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020048629 |
Kind Code |
A1 |
Romack, Timothy J. ; et
al. |
April 25, 2002 |
CARBON DIOXIDE CLEANING AND SEPARATION SYSTEMS
Abstract
A separation method includes (a) providing a heterogeneous
separation system, the heterogeneous cleaning system comprising
CO.sub.2 in a first phase and an oil in a separate second phase;
(b) entraining a material to be separated in the second phase; (c)
wholly or partially solubilizing the second phase in the first
phase to produce a separation system in which said material to be
separated is insoluble; and then (d) separating the material from
the system. The separating step is preferably followed by the step
of (e) recovering at least a portion of the oil. The system is
useful in a variety of applications, including cleaning
(particularly metal cleaning), polymerization, extraction, coating,
and particle formation and treatment.
Inventors: |
Romack, Timothy J.; (Durham,
NC) ; McClain, James B.; (Carrboro, NC) ;
Stewart, Gina M.; (Durham, NC) ; Givens, Ramone
D.; (Durham, NC) |
Correspondence
Address: |
MYERS BIGEL SIBLEY & SAJOVEC
PO BOX 37428
RALEIGH
NC
27627
US
|
Family ID: |
22093759 |
Appl. No.: |
09/579676 |
Filed: |
May 26, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09579676 |
May 26, 2000 |
|
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09070196 |
Apr 30, 1998 |
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Current U.S.
Class: |
427/2.14 |
Current CPC
Class: |
B08B 7/0021 20130101;
C11D 7/50 20130101; C11D 7/44 20130101 |
Class at
Publication: |
427/2.14 |
International
Class: |
A61J 001/00 |
Claims
That which is claimed is:
1. A method of cleaning a contaminant from a substrate, comprising:
contacting a substrate with a heterogeneous cleaning system, the
heterogeneous cleaning system comprising CO.sub.2 in a first phase
and a cleaner in a separate second phase, so that contaminant
carried by said substrate is entrained in said cleaner; then
solubilizing said cleaner in said first phase to produce a cleaning
system in which said contaminant is immiscible and said contaminant
is separated from said substrate; and separating said substrate
from said cleaning system before or after said solubilizing step;
and separating said contaminant from said cleaner.
2. A method according to claim 1, wherein said step of separating
said substrate from said cleaning system is carried out prior to
said solubilizing step.
3. A method according to claim 1, wherein said step of separating
said substrate from said cleaning system is carried out after said
solubilizing step.
4. A method according to claim 1, further comprising the step of
rinsing said substrate with CO.sub.2 after said contacting
step.
5. A method according to claim 1, further comprising the steps of
rinsing said substrate in said homogeneous cleaning system after
said solubilizing step; and then separating said substrate from
said homogeneous cleaning system.
6. A method according to claim 1, further comprising the step of:
separating said cleaner from said CO.sub.2 following said step of
separating said homogeneous cleaning system from said
contaminant.
7. A method according to claim 1, wherein said contaminant is
insoluble in said CO.sub.2 during said contacting step.
8. A method according to claim 1, wherein said contaminant is a
hydrocarbon.
9. A method according to claim 1, wherein said cleaner is an
oil.
10. A method according to claim 1, wherein said cleaner is a
vegetable oil.
11. A method according to claim 1, wherein said first phase is the
continuous phase and said second phase is a disperse phase.
12. A method according to claim 1, wherein said first phase and
said second separate phase are both liquid phases.
13. A method according to claim 1, wherein said cleaning system is
a non-aqueous cleaning system.
14. A method according to claim 1, wherein said substrate is a
metal substrate.
15. A method according to claim 1, wherein said solubilizing step
is carried out by solubilizing substantially all of said cleaner in
said first phase to produce a substantially homogeneous cleaning
system in which said contaminant is insoluble.
16. A separation method, comprising: providing a heterogeneous
separation system, the heterogeneous separation system comprising
CO.sub.2 in a first phase and an oil in a separate second phase;
then entraining a material to be separated in said second phase;
and then solubilizing said second phase in said first phase to
produce a separation system in which said material to be separated
is insoluble; and then separating said material from said
system.
17. A method according to claim 16, wherein said separating step is
followed by the step of: recovering at least a portion of said
oil.
18. A method according to claim 16, wherein said material to be
separated is a polymer and said entraining step is carried out by:
adding a monomer to said system; and polymerizing said monomer in
said second phase.
19. A method according to claim 16, wherein said entraining step is
carried out by: extracting said material to be separated into said
second phase.
20. A method according to claim 16, wherein said separating step is
carried out by: depositing said material on a substrate; and then
separating said substrate from said system.
21. A method according to claim 20, wherein said substrate is a
particle.
22. A method according to claim 20, wherein said depositing step is
carried out on the surface of said substrate to form a coating on
said substrate.
23. A method according to claim 16, wherein said separating step is
carried out by: forming particles comprising said material during
said solubilizing step; and then collecting said particles from
said system.
24. A method according to claim 16, wherein said oil is a vegetable
oil.
25. A method according to claim 16, wherein said first phase is the
continuous phase and said second phase is a disperse phase.
26. A method according to claim 16, wherein said first phase and
said second separate phase are both liquid phases.
27. A method according to claim 16, wherein said system is a
non-aqueous system.
28. A method according to claim 16, wherein said recovering step is
carried out by: separating said oil from said carbon dioxide to
provide a heterogeneous separation system; and then recycling said
heterogeneous separation system to said providing step.
29. A method according to claim 16, wherein said recovering step is
carried out by: physically separating said oil from said carbon
dioxide.
30. A method according to claim 16, wherein said solubilizing step
is carried out by solubilizing substantially all of said second
phase in said first phase to produce a substantially homogeneous
separating system in which said material to be separated is
insoluble.
31. A method of depositing a material on a substrate, comprising:
providing a heterogeneous separation system, the heterogeneous
separation system comprising CO.sub.2 in a first phase and an oil
in a separate second phase; then entraining a material to be
separated in said second phase; and then solubilizing said second
phase in said first phase to produce a separation system in which
said material to be separated is insoluble; and then depositing
said material on said substrate; and then separating said substrate
from said system.
32. A method according to claim 31, wherein said separating step is
followed by the step of: recovering at least a portion of said
oil.
33. A method according to claim 31, wherein said material is a
polymer.
34. A method according to claim 31, wherein said substrate is a
drug particle.
35. A method according to claim 31, wherein said substrate is a
fiber.
36. A method according to claim 31, wherein said depositing step is
carried out on the surface of said substrate to form a coating on
said substrate.
37. A method according to claim 31, wherein said oil is a vegetable
oil.
38. A method according to claim 31, wherein said solubilizing step
is carried out by solubilizing substantially all of said second
phase in said first phase to produce a substantially homogeneous
separating system in which said material to be separated is
insoluble.
Description
FIELD OF THE INVENTION
[0001] This invention relates to cleaning and separation methods
useful in cleaning substrates, particularly metal substrates, and
useful for polymerization processes, coatings, extractions, and the
manufacture and treatment of particles.
BACKGROUND OF THE INVENTION
[0002] The cleaning of contaminants from workpieces is an important
step in many manufacturing processes. Unfortunately, many processes
employ environmentally undesirable solvents, or are high
temperature processes that are energy intensive. For example, vapor
degreasing techniques employ both volatile organic solvents and
high temperatures. Efforts to replace such processes with aqueous
systems are not entirely satisfactory because of the problem of
contacting water to substrates that may be oxidized thereby, and by
the problem of cleaning the contaminated water. In addition, the
drying of aqueous systems is very energy intensive.
[0003] Vegetable oils such as soybean oil and modified soybean oil
have been suggested for cleaning, but have not received significant
use because of either their high cost or the difficulty in removing
or extracting residual components of the oil.
[0004] CO.sub.2-based cleaning methods have been suggested. Some
employ supercritical CO.sub.2, which (due to the need to handle
higher temperatures and/or pressures) increases the cost of the
apparatus used to carry out the processes. U.S. Pat. No. 5,377,705
to Smith et al. describes a precision cleaning system in which a
variety of different co-solvents may be included (see column 8,
lines 19-24 therein), with the mixture of the carbon dioxide and
the co-solvent being either homogenous or heterogenous (see column
6, lines 4-11 therein). A problem with this system that it still
does not provide a means to separate the contaminant from the
co-solvent (see column 7, lines 24-32).
[0005] Accordingly, an object of the present invention is to
provide a carbon-dioxide based cleaning system incorporating a
separate cleaner, in which the contaminants may be separated from
the cleaner to facilitate subsequent re-use or disposal of the
cleaner.
[0006] A second object of the invention is to provide oil-based
separation systems in which the oil, such as a vegetable oil, may
be recovered for subsequent reuse.
SUMMARY OF THE INVENTION
[0007] A separation method comprises (a) providing a heterogeneous
separation system, the heterogeneous cleaning system comprising
CO.sub.2 in a first phase and an oil in a separate second phase;
(b) entraining a material to be separated in the second phase; (c)
solubilizing the second phase, in whole or in part, in the first
phase to produce a separation system in which said material to be
separated is insoluble; and then (d) separating the material from
the system. The separating step is preferably followed by the step
of (e) recovering the oil (i.e., some or all of the oil), so that
it may be re-used in or recycled to step (a) above. Each of the
steps may be carried out with or without agitation.
[0008] An advantage of the invention is that the separation system
is phase-tunable, in that the material of the second phase can
alternately be rendered soluble, in whole or in part, or insoluble
in the first phase, alternately rendering the material to be
separated soluble or insoluble in the system in a controllable
manner. Thus the system is a homogeneous system in one embodiment,
when the second phase is wholly solubilized in the first phase to
render the material to be separated insoluble therein.
[0009] The system is useful in a variety of applications, including
cleaning, polymerization, extraction, coating, and particle
formation and treatment. The system is particularly advantageous
where the oil employed is of a relatively high cost. Since
environmentally acceptable solvents such as organic or vegetable
oils (including synthetic oils) can be relatively expensive, this
system enables the use of such products in a broader variety of
applications, in a cost-effective manner.
[0010] As noted above, one particular aspect of the invention is a
method of cleaning a contaminant from a substrate. The method
comprises contacting a substrate with a heterogeneous cleaning
system. The heterogeneous cleaning system comprising CO.sub.2 in a
first phase and a cleaner (preferably an oil such as an organic, or
vegetable, oil) in a separate second phase, so that contaminant
carried by said substrate is entrained in the cleaner. The cleaner
is then wholly or partially solubilized in the first phase (e.g.,
by increasing the pressure of the system) to produce a cleaning
system in which the contaminant is immiscible (e.g., a homogeneous
cleaning system), and that contaminant is separated from the
substrate. The substrate is separated from the cleaning system,
either before or after the solubilizing step, and the contaminant
(which has been rendered immiscible in the cleaning system) is
separated from the cleaner. The cleaning system advantageously can
be implemented as a non-aqueous system, thereby reducing drying
times and problems with oxidation.
[0011] The foregoing and other objects and aspects of the present
invention are explained in detail below.
BRIEF DESCRIPTION OF THE DRAWING
[0012] FIG. 1 is a schematic diagram of a process of the invention,
in which the phase-tunable system is represented by boxes 2, 3, 4
and 5 at different steps in the process.
DETAILED DESCRIPTION OF THE INVENTION
[0013] A CO.sub.2-based cleaning and separation system is disclosed
herein. The system includes a material that may be alternately
rendered miscible or immiscible in the carbon dioxide. Hence, the
system is referred to as a "phase-tunable" system in that one phase
may alternately be rendered soluble or insoluble in the other,
carbon dioxide-containing, phase.
[0014] Suitable materials that may alternately be rendered soluble
or insoluble in the carbon dioxide-containing phase are, in
general, oils such as esters of fatty acids (including methyl,
ethyl, propyl, and butyl esters, etc.) mineral oils (including
paraffinic and/or naphthenic petroleum distillates), aliphatic
hydrocarbons, polyethyleneglycols, polypropylene glycols,
polyisobutylenes, poly alpha olefins, saturated and unsaturated
carboxylic (fatty) acids, lard, tallow, triglycerides, vegetable
oils (including soy, corn, sunflower, safflower, olive, canola
corn, almond, and walnut oils, and modified derivatives thereof,
particularly SOYSOLV.RTM., etc.), and fatty acids, fatty alcohols,
fatty amines, and modifications thereof including fatty esters,
fatty ethers, and fatty amides.
[0015] In general, the first phase comprises carbon dioxide, and
the second phase comprises a material that may alternately be
rendered soluble or insoluble in carbon dioxide as described above.
Typically, the first phase is the continuous phase and the second
phase is the dispersed phase, and both phases are liquid phases.
Additional phases or materials can be added where desired or
permitted. For example, a substrate to be cleaned or a substrate on
which material is to be deposited can be added to the system, an
aqueous phase could be incorporated itself into the second oil
phase (e.g., the oil phase itself could be an emulsion or
microemulsion), etc.
[0016] A schematic overview of the method of the invention is shown
in FIG. 1, which shows a separation method, comprising providing a
heterogeneous separation system 2, the heterogeneous cleaning
system comprising CO.sub.2 in a first phase 12 and a separate
second phase 13. In the next step 15, a material to be separated 14
is entrained in the second phase. In the next step 16, the second
phase is solubilized in the CO.sub.2 to produce a homogeneous
separation system 19 in which said material 14 to be separated is
insoluble or immiscible (note that some material may remain soluble
or slightly soluble in the separation system, as long as a
sufficient portion of the material to be separated is rendered
insoluble, to achieve the desired separation). In step 17, the
insoluble material is then separated from the system, and in step
18 the system is recycled to re-form the heterogeneous system
(e.g., by decreasing pressure) to thereby recover the oil. The
method is typically carried out in a closed vessel to permit
maintenance and control of the pressure in a suitable manner. While
step 16 of FIG. 1 illustrates a homogeneous system, note that not
all of the second phase must be solubilized into the first phase,
so long as a sufficient amount is solubilized into the first phase
to render an effective portion of material to be separated
insoluble in, and separable from, the system.
[0017] In a cleaning process, the material to be separated is
carried into the system on a substrate, and that material is then
entrained or solubilized into the second phase.
[0018] In a polymerization process, the material to be separated is
a polymer. The entraining step is carried out by adding a monomer
to the system; and then polymerizing the monomer in the second
phase. The polymer may be either soluble or insoluble in the second
phase.
[0019] In an extraction process, the process is simply carried out
by extracting the material to be separated into the second phase as
the separation step.
[0020] In a coating or treatment process, the separating step is
carried out by depositing the material on a substrate and then
separating the substrate from the system. The depositing step can
be carried out in a manner that forms a coating on the surface of
the substrate (e.g., with a solid substrate such as a metal or
glass), or can be carried out in a manner so that the material
impregnates the substrate (e.g. polymer particles or beads).
[0021] In a particle manufacture process, the separating step is
carried out by forming particles comprising said material during
said solubilizing step, and then collecting the particles from the
system. This process may advantageously be combined with the
polymerization process discussed above.
[0022] The recovering step is carried out by any suitable means.
For example, the recovering step may be carried out by separating
the oil from the carbon dioxide to provide a heterogeneous
separation system; and then recycling the heterogeneous separation
system to the initial "providing" step as illustrated by line 18 in
FIG. 1. Alternatively, the recovering step may be carried out by
physically separating the oil from the carbon dioxide (e.g., by
venting the carbon dioxide from the vessel in which the system is
contained, and then optionally draining the oil, or a concentrated
oil and carbon dioxide mixture, from the vessel).
[0023] Where the instant invention is carried out to apply or
incorporate a material or other additive to a substrate from the
second phase (see coating and treatment methods below), after the
recovery step a portion of the additive is regained. Make-up and
maintenance of a desired charge of ingredient can occur by several
routes:
[0024] 1.) Metering of the make-up fluid into a low pressure area
of the system. The low pressure area is the Cleaning/Treatment
Chamber (where materials and substrates must be put in and out of
the system. This can be affected by many means: (a) A blocked off
segment of pipe that is isolated from the chamber and substrate but
will be flushed by the incoming process fluid (process fluid could
also be circulated during the cycle, then the additional ingredient
could be brought into the system at any time during the cycle--this
is important if one desires to incorporate any kind of
pre-treatment at a lower concentration) (b) Placed directly into
the chamber before, during of after the addition of a substrate.
(c) Metering pump pulling from a low pressure reservoir to the high
pressure point in the system. The high presssure point can be
anywhere.
[0025] 2.) By fractionation of the contaminant/extract. For example
in a metal cleaning application, little or no oil need to be added
over. Loses would be recovered by using the fraction of the
contaminant with the same solubility characteristics as the
original active ingredient. Note that the composition of the oil
could change over time without adversely affecting the operation of
the system.
[0026] Specific embodiments of the invention are discussed in
greater detail below.
[0027] 1. Cleaning Methods.
[0028] Contaminants to be cleaned are miscible in the cleaner when
the cleaner is immiscible in carbon dioxide but immiscible in the
cleaner when the cleaner is miscible in carbon dioxide. The
solvating characteristics of the cleaner makes possible both the
cleaning of the contaminant from the substrate and the separation
of the contaminant from the cleaner. The cleaner may then be
re-used, either in combination with the CO.sub.2 in the original
cleaning system or by separating the cleaner from the CO.sub.2.
Alternatively, the cleaner may be disposed of without the problem
of substantial amounts of contaminants entrained therein.
[0029] CO.sub.2 used to carry out the present invention is
preferably liquid CO.sub.2, particularly during the step of
contacting the cleaning system to the substrate.
[0030] Cleaners that may be used in the present invention are, in
general, cleaners that are immiscible in CO.sub.2, at the
temperature, pressure and concentrations, in which the cleaning
step is carried out. The cleaner is, however, selected so that it
may be rendered soluble in CO.sub.2 by manipulating the
temperature, pressure, and/or concentration thereof (i.e., by
raising one, or both, of temperature and pressure; by increasing
CO.sub.2 volume, etc.). The cleaner is typically an oil as
described above.
[0031] Cleaning systems of the present invention (that is, systems
used during the cleaning step) are mixtures of CO.sub.2, typically
liquid CO.sub.2, and the second phase (the CO.sub.2-immiscible
cleaner). The mixture may be in any suitable form, including
suspensions, dispersions, and emulsions (including microemulsions).
Preferably the CO.sub.2 is the continuous phase and the immiscible
cleaner is the disperse phase in the system, but in an alternate
embodiment the CO.sub.2 may be the disperse phase and the
immiscible cleaner may be the continuous phase. In either case, the
two phases are rendered miscible during the separation step, as
discussed in greater detail below. The cleaning systems are
preferably non-aqueous. The second phase comprises from about 1, 2
or 3 percent to about 40, 50, or 60 percent by volume of the
cleaning system.
[0032] The CO.sub.2-containing phase may optionally include a
co-solvent. Any co-solvent may be employed that is miscible in
CO.sub.2 under the conditions of the process. Examples of suitable
co-solvents include, but are not limited to, methanol, ethanol,
methyl ethyl ketone, acetone, and alcohols. Where a co-solvent is
included, it may be included in any suitable amount, typically from
about 1, 2 or 3 to about 20, 30, or 40 percent by volume of the
first phase.
[0033] Contaminants that may be cleaned by the present invention
include hydrocarbons, particularly hydrocarbons that are insoluble
in liquid CO.sub.2. Examples of such contaminants are quench oils
such as FERROCOTE.TM., honey oils, cutting oils, heat transfer
oils, etc. Such hyrocarbons may or may not be halogenated, and
include numerous paraffins. Other contaminants include
fingerprints, dust, residuals, grit, grime, adhesives, coatings
such as paint, varnish, films, rust, scale and corrosion, etc.
[0034] Substrates that may be cleaned by the method of the present
invention include metals such as steel, copper, and aluminum. The
substrate may be in any form, including small parts such as screws,
nuts, aircraft components, radiator channels and elbows, etc.
[0035] Additional substrates to be cleaned include plastics,
ceramics, wood, glass and fiberglass and combinations thereof, such
as textiles (e.g., gloves and rags for decontamination). The
substrate may be an item to be restored or recycled such as an item
having a painted surface, etc.
[0036] In general, the instant method initially involves contacting
a substrate with a heterogeneous cleaning system. The contacting
step is typically carried out in an enclosed pressure vessel (a
cleaning vessel), and is carried out at a pressure and temperature
and concentrations of CO.sub.2 and cleaner such that the
heterogeneous cleaning system comprises CO.sub.2 in a first phase
and the cleaner in a separate second phase. The contacting step is
carried out for a time sufficient for contaminant carried by said
substrate to be entrained, in whole or in part, in the cleaner.
[0037] Liquid conditions are preferred because of the ease of
separating the contacting fluid from the substrate. This is a
function of temperature and pressure as described in the literature
(e.g. A New Equation of State for Carbon Dioxide Covering the Fluid
Region from the Triple-Point Temperature to 1100 Kelvin at
Pressures up to 800 Mpa, R. Span, W Wagner; J. Phys. Chem. Ref.
Data Vol 25, No. 6, 1996 and references therein).
[0038] Also useful in carrying out the invention are "denisfied
phases" of CO.sub.2. These are: (1) any state of `compressed
liquid`, typically at a pressure above the saturation pressure and
all temperatures below the critical point, Pmax=500 bar, (2)
supercritical, or near-critical state which are temperatures above
the critical point, Tmax=150.degree. C. and pressures such that the
density of the fluid is greater than the critical density, rmin=0.4
g/cc, Pmax=500 bar.
[0039] In general, all densities above 0.4 g/cc and pressures less
than 500 bar in the fluid regions (fluid=supercritical,
near-critical and liquid), are useful in carrying out the present
invention.
[0040] The step of solubilizing the cleaner in the CO.sub.2 to
produce a homogeneous cleaning system in which the contaminant is
immiscible may be carried out in the same vessel or a different
vessel from the contacting step, depending on the particular form
of the apparatus used to carry out the method. Solubilizing of the
cleaner in the CO.sub.2 may be carried out by any suitable means,
including manipulating temperature, pressure, concentration of
CO.sub.2, and combinations thereof. For example, the pressure of
the system could be increased, the temperature could be increased,
or the concentration of CO.sub.2 could be decreased (e.g., by
partial venting of the CO.sub.2). As with the contacting step, the
system is preferably a liquid system during the solubilizing step.
Whether carried out in the same vessel as the contacting step or a
separate vessel, the contaminant is separated from the substrate
(e.g., by proper positioning of the substrates within a basket in
the contacting vessel so that the contaminant rises or settles to a
different location therein).
[0041] After the contacting step, the substrate is preferably
rinsed with CO.sub.2 before it is removed from the vessel. Rinsing
may be accomplished by any means. The vessel may be drained of the
cleaning system and a separate CO.sub.2 rinse solution (which may
or may not contain co-solvents) passed into the vessel.
Alternatively, the rinsing may be carried out with the cleaning
solution itself after it has been rendered homogeneous. In the
latter case, the cleaning solution may again be rendered
homogeneous in either the same or a different pressure vessel in
which the contacting step is carried out, depending on the
particular form of the apparatus employed.
[0042] As will be apparent from the foregoing, the substrate can be
separated from the cleaning system either before or after the
solubilizing step. For example, if the cleaning system is drained
from the cleaning vessel and the two phases then rendered miscible
in a separate vessel, the substrate is thereby separated from the
cleaning system before the solubilizing step. If the two phases are
rendered miscible within the reaction vessel (and the system then
used as a rinse solution), the substrate will be separated from the
cleaning system after the solubilizing step (e.g., by subsequent
draining of the system or venting of the carbon dioxide).
[0043] Separation of the contaminant from the cleaner may be
carried out in a variety of ways. The cleaning system may be
transferred from the cleaning vessel to a separate vessel, the two
phases rendered miscible, and the immiscible contaminant separated
therein by any suitable means, such as filtering, sedimentation,
distillation, etc.
[0044] Materials and methods employed in carrying out cleaning
methods as described herein may be applied in like manner to the
methods described below.
[0045] 2. Polymerization Methods.
[0046] In a polymerization process, the material to be separated is
a polymer and the entraining step is carried out by adding a
monomer to the system; and then polymerizing the monomer in the
second phase. Any suitable polymerization process may be employed,
and monomers and initiators may be located in any suitable
compartment of the system. The reaction may be carried out with
other polymers dissolved or dispersed in any suitable compartment
of the system.
[0047] Temperatures, pressures, and other processing steps employed
in carrying out these techniques may be essentially the same as
described in conjunction with cleaning methods above, as modified
by the requirements of the specific process.
[0048] 3. Extraction Methods.
[0049] In an extraction process, a single component or multiple
components to be retained or removed are separated from a liquid or
solid mixture. In the present invention, the extraction process is
simply carried out by extracting the material to be separated into
the second phase as the separation step. The invention is
particularly advantageous in extracting material from a mixture
comprising biological materials or biomass (e.g., a microbiological
fermentation broth, vascular plant material such as leaves,
needles, stems, roots, and bark, etc.), or in separating a
constituent from the product mixture of an organic reaction or
biochemical reaction.
[0050] Temperatures, pressures, and other processing steps employed
in carrying out these techniques may be essentially the same as
described in conjunction with cleaning methods above, as modified
by the requirements of the specific process.
[0051] 4. Coating and Treatment Methods.
[0052] As noted above, in a coating or treatment process, the
separating step is carried out by depositing the material on a
substrate and then separating the substrate from the system. The
depositing step can be carried out in a manner that forms a coating
on the surface of the substrate (e.g., with a solid substrate such
as a metal or glass part, or a drug particle), or can be carried
out in a manner so that the material impregnates the substrate
(e.g., polymer, metal, or clay or zeolite particles or beads).
Fibers, including natural fibers (e.g., cotton, wool) and synthetic
or polymer fibers (e.g., poly(ethylene terephthalate)), can be
treated or impregnated with materials by this method.
[0053] Particles and fibers may be coated with materials such as
biopolymers (e.g., polypeptides, oligonucleotides), fluoropolymers,
organic compounds, fire retardants, biocides, plasticizing agents,
colorants or dyes, etc. to impart drugs, pharmaceutical agents,
modify toxicity, add dyes and colorants, modify surfaces (including
modification of hydrophobicity/hydrophilicity, roughness or surface
texture, uniformity, spherocity, packing density, adhesive
properties, etc.
[0054] Drug particles used to carry out the present invention are
typically solid particulate drugs (optionally in combination with a
pharmaceutically acceptable carrier such as lactose). Drug
particles for inhalation use are, in general, respirable particles,
typically from about 0.1 or 0.5 to 5 or 10 microns in size. The
present invention is particularly useful for coating such drug
particles with polymers or other materials that inhibit aggregation
in a propellant so that the particles may subsequently be used in a
metered dose inhaler. Examples of drugs from which respirable
particles may be formed include, but are not limited to, peptides,
oligonucleotides (including natural and synthetic), and organic
compounds such as epinephrine hydrochloride or bitartrate,
ergotamine tartrate, albuterol, metaproterenol sulfate,
beclomethasone dipropionate, flunisolide hemihydrate, cromolyn
sodium, nedocromil sodium, iptropium bromide, salmeterol xinafoate,
triamcinolone acetonide, pirbuterol acetate, bitolterol mesylate,
dexamethasone sodium phosphate, terbutaline sulfate, nitroglycerin,
budesonide, etc.
[0055] Temperatures, pressures, and other processing steps employed
in carrying out these techniques may be essentially the same as
described in conjunction with cleaning methods above, as modified
by the requirements of the specific process.
[0056] 5. Particle Manufacture Methods.
[0057] In a particle manufacture process, the separating step is
carried out by forming particles comprising said material during
said solubilizing step, and then collecting the particles from the
system. This process may advantageously be combined with the
polymerization process discussed above. Thus, particles may be
formed from a polymer (latex, dispersion, emulsion products, drug
delivery particles, particles for use in aerosol formulations or
photocopy toner). In general, as the process progresses, particle
formation occurs as the carbon dioxide solubilizes the oil phase.
Control of the size of the dispersed oil phase advantageously
enables control of the size of the particles formed.
[0058] Temperatures, pressures, and other processing steps employed
in carrying out these techniques may be essentially the same as
described in conjunction with cleaning methods above, as modified
by the requirements of the specific process.
[0059] The present invention is explained in greater detail in the
following non-limiting examples.
EXAMPLE 1
Cleaning of a Screw Machine Part
[0060] Carbon steel machined nuts (200 g) coated with a heat quench
oil (13 g) are added to a 1.6-L pressure-rated vessel at room
temperature. SOYSOLV.RTM. (80 mL), an immiscible soybean oil
obtained from Steyer Farms, Inc. (6154 N. Co. Rd. 33, Tiffin, Ohio,
44883 USA), is added and the vessel is filled with CO.sub.2 to
liquid half full (.about.700 mL at 850-875 psia). The parts are
rotated at 5-10 RPM inside a mesh cage while the wash fluid is
circulating and emulsified by a pump for 5 minutes. The wash fluid
is then drained and the vessel is refilled with CO.sub.2 to
1000-1500 psia. The rinse liquid is circulated for 5 minutes and
then drained. After the residual pressure is vented, the parts are
removed from the vessel. No quench oil remains on the parts by
visual inspection, and wiping the parts on a white sheet of paper
leaves no residue.
[0061] In a separate chamber, the wash fluid is subjected to 1600
psig, solubilizing the SOYSOLV.RTM. oil in the CO.sub.2 phase and
allowing separation of a substantial portion of the heat quench oil
contaminant from the system.
EXAMPLE 2
Cleaning of Screw Machine Part
[0062] Carbon steel machined nuts (2.89 g) coated with a heat
quench oil (0.01-0.05 g) are added to a 10-mL pressure-rated vessel
at room temperature. An immiscible hydrocarbon solvent, 1.0 mL
Isopar V, available from the Exxon Company, is added and the vessel
is filled with CO.sub.2 to liquid half full (.about.5.0 mL at
850-875 psia). The wash fluid is stirred via a magnetically coupled
stir bar for 5 minutes. The wash fluid is then drained and the
vessel is refilled with CO.sub.2 to 1000-1500 psia. The rinse
liquid is circulated for 5 minutes and then drained. After the
residual pressure is vented, the parts are removed from the vessel.
A major portion of the contaminant is removed from the parts as
determined by visual inspection, and wiping the parts on a white
sheet of paper leaves a slight residue.
[0063] In a separate chamber, the wash fluid is subjected to 1600
psig, solubilizing the SOYSOLV.RTM. in the CO.sub.2 phase and
allowing separation of a substantial portion of the heat quench oil
contaminant from the system.
EXAMPLE 3
Demonstration of "Oil" Solubilization Step
[0064] A 50:50 volume mixture of a heat quench oil and SOYSOLV.RTM.
oil (8.5 g) is added to a 160-mL pressure rated vessel at room
temperature. Liquid CO.sub.2 (80 mL) at 850-875 psia is introduced
into the vessel. The vessel contents separate into two liquid
layers, and the bottom layer is drained from the vessel. This 4.70
g fraction is predominantly heat quench oil. The vessel is then
depressurized by distillation of CO.sub.2. The remaining 3.63 g of
oil is predominantly SOYSOLV.RTM. oil.
EXAMPLE 4
Polymerization of Acrylamide and Isolation of Polymer
[0065] A mixture of CO2 (80 vol %) and SOYSOLV.RTM. oil (20 vol %)
is maintained at 50.degree. C. under pressure conditions where two
phases (one primarily soy and the other primarily CO.sub.2) are
present. The soy phase is dispersed in the CO.sub.2 continuous
phase through agitation. A mixture of acrylamide monomer and
2,2-bisazobutyronitiile (AIBN) dissolved in acetone is metered into
the reactor. Acrylamide is largely insoluble in CO.sub.2, and
partitions into the soy phase. Once polymerization is complete, the
pressure is increased until the soy phase becomes soluble in
CO.sub.2. The soy/CO.sub.2 solvent system is then displaced with
CO.sub.2 at sufficient pressure to dissolve the soy product. The
pressure is released and solid polyacrylamide recovered from the
reactor.
EXAMPLE 5
Polymerization of Styrene and Isolation of Polymer
[0066] A 25.degree. C. mixture of SOYSOLV.RTM. oil (20%) and
CO.sub.2 (80%) is prepared in a well circulated polymerization
reactor at 850 psig. The heterogeneous mixture consists of small
droplets of soysolv dispersed in a continuous phase of CO.sub.2.
Diisopropyl peroxy dicarbonate, a room temperature free radical
polymerization initiator and styrene monomer are simultaneously
metered into the reactor. As polystyrene, which is insoluble in
CO.sub.2 and soluble in SOYSOLV.RTM. oil, is formed, it is
entrained in the dispersed droplets of the oil. Once the
polymerization reaction is complete, pressure is increased to 2500
psig (by adding additional CO.sub.2), solubilizing the soy and
allowing isolation of polystyrene. The homogeneous mixture of soy
and CO.sub.2 is removed from the reactor, the pressure is vented,
and polystyrene is isolated.
EXAMPLE 6
Natural Product Extraction
[0067] A natural product is extracted from organic matter using a
heterogeneous mixture of SOYSOLV.RTM. OIL and CO.sub.2. The natural
product is soluble in Soysolv.RTM. oil and relatively insoluble in
CO.sub.2. The heterogeneous extraction fluid is then pumped into a
higher pressure zone where the SOYSOLV.RTM. oil is soluble in
CO.sub.2 and the desired natural product is precipitated into the
solution of SOYSOLV.RTM. OIL and CO.sub.2. The fine suspension of
natural product is then isolated in a cyclone separator.
EXAMPLE 7
Coating of a Metal Part
[0068] Metal screw machine parts are placed in a high-pressure
chamber containing polystyrene dissolved in SOYSOLV.RTM. oil. The
parts are rotated at a low speed through the liquid as CO.sub.2 is
added to the vessel. The liquid heterogeneous mixture so formed in
the vessel consists of a predominantely CO.sub.2 continuous phase
and a dispersed phase of SOYSOLV.RTM. oil and polystyrene. As more
CO.sub.2 is added, the SOYSOLV.RTM. oil is extracted into the
continuous phase, leaving the polystyrene coated on the parts. The
CO.sub.2/SOYSOLV.RTM. oil homogeneous liquid is then drained from
the vessel, and the parts are rinsed with fresh CO.sub.2. After the
vessel is vented, the metal parts, coated with polystyrene, are
removed.
EXAMPLE 8
Coating/Impregnation of Preformed Particles
[0069] Preformed particles of respirable drug particles are placed
into a chamber. The chamber is pressurized to the vapor pressure of
CO.sub.2 and a heterogeneous mixture of SOYSOLV.RTM. oil and
CO.sub.2, the soy oil phase containing lecithin, is pumped into the
chamber with mixing. The pressure is raised to ca. 2500 psi,
solubilizing the soy product in the CO.sub.2 and depositing the
lecithin on the drug particles. The soy oil/CO.sub.2 solvent
mixture is then removed by flushing with pure CO.sub.2. The
remaining CO.sub.2 is vented, the chamber opened, and lecithin
coated drug particles recovered for use.
EXAMPLE 9
Fiber Coating
[0070] Poly(ethylene teraphthalate) (or "PET") fiber is processed
in a high pressure chamber containing a heterogeneous liquid
mixture of acrylic copolymer dissolved in SOYSOLV.RTM. soy oil
dispersed phase, suspended in a CO.sub.2 continuous phase. As the
pressure is raised by adding more CO.sub.2, the soy oil dissolves
into the CO.sub.2 phase, precipitating the acrylic copolymer onto
the PET fiber. The solution of CO.sub.2 and soy oil is then
replaced with pure CO.sub.2 which is removed and the acrylic coated
PET fiber is recovered.
EXAMPLE 10
Production of PEEK Particles
[0071] Poly(ether ether ketone) (or "PEEK") and liquid diphenyl
sulphone as the oil are added to a vessel containing CO.sub.2.
Under the conditions employed the mixture forms a heterogeneous
mixture of two liquids: a solution of PEEK dissolved in diphenyl
sulphone, dispersed in a CO.sub.2 continuous phase. The CO.sub.2
pressure and temperature are raised to a point where diphenyl
sulfone is soluble in CO.sub.2 precipitating PEEK as particles.
EXAMPLE 11
Production of Polystyrene Particles
[0072] Polystyrene is dissolved into the oil phase of a pre-made
oil-in-CO.sub.2 suspension. The pressure of the CO.sub.2 is
increased, solubilizing the oil, precipitating polystyrene as
particles. The polystyrene particles are isolated in a cyclone
separator and the solution of oil and CO.sub.2 recycled to a lower
pressure where it again forms two phases and can be used to
dissolve more polystyrene.
[0073] The foregoing is illustrative of the present invention, and
is not to be construed as limiting thereof. The invention is
defined by the following claims, with equivalents of the claims to
be included therein.
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