U.S. patent application number 10/797516 was filed with the patent office on 2004-09-02 for cleaning system utilizing an organic cleaning solvent and a pressurized fluid solvent.
Invention is credited to Damaso, Gene R., Racette, Timothy L., Schulte, James E..
Application Number | 20040168262 10/797516 |
Document ID | / |
Family ID | 23661856 |
Filed Date | 2004-09-02 |
United States Patent
Application |
20040168262 |
Kind Code |
A1 |
Racette, Timothy L. ; et
al. |
September 2, 2004 |
Cleaning system utilizing an organic cleaning solvent and a
pressurized fluid solvent
Abstract
A cleaning system that utilizes an organic cleaning solvent and
pressurized fluid solvent is disclosed. The system has no
conventional evaporative hot air drying cycle. Instead, the system
utilizes the solubility of the organic solvent in pressurized fluid
solvent as well as the physical properties of pressurized fluid
solvent. After an organic solvent cleaning cycle, the solvent is
extracted from the textiles at high speed in a rotating drum in the
same way conventional solvents are extracted from textiles in
conventional evaporative hot air dry cleaning machines. Instead of
proceeding to a conventional drying cycle, the extracted textiles
are then immersed in pressurized fluid solvent to extract the
residual organic solvent from the textiles. This is possible
because the organic solvent is soluble in pressurized fluid
solvent. After the textiles are immersed in pressurized fluid
solvent, pressurized fluid solvent is pumped from the drum.
Finally, the drum is de-pressurized to atmospheric pressure to
evaporate any remaining pressurized fluid solvent, yielding clean,
solvent free textiles. The organic solvent is preferably
dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether
or tripropylene glycol methyl ether, a mixture thereof, or a
similar solvent and the pressurized fluid solvent is preferably
densified carbon dioxide.
Inventors: |
Racette, Timothy L.;
(Plainfield, IL) ; Damaso, Gene R.; (Northlake,
IL) ; Schulte, James E.; (Cicero, IL) |
Correspondence
Address: |
MAYER, BROWN, ROWE & MAW LLP
190 SOUTH LASALLE ST
CHICAGO
IL
60603-3441
US
|
Family ID: |
23661856 |
Appl. No.: |
10/797516 |
Filed: |
March 10, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10797516 |
Mar 10, 2004 |
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10057068 |
Jan 25, 2002 |
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6736859 |
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10057068 |
Jan 25, 2002 |
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09419345 |
Oct 15, 1999 |
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6355072 |
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Current U.S.
Class: |
8/159 ; 68/17R;
68/207 |
Current CPC
Class: |
C11D 11/0064 20130101;
C11D 7/5022 20130101; C11D 7/264 20130101; C11D 7/263 20130101;
B08B 7/0021 20130101; D06L 1/02 20130101; B08B 3/12 20130101; C11D
7/266 20130101; C11D 7/5004 20130101; D06F 43/007 20130101; D06L
1/08 20130101; C11D 7/262 20130101; C11D 7/261 20130101 |
Class at
Publication: |
008/159 ;
068/207; 068/017.00R |
International
Class: |
D06B 009/04 |
Claims
What is claimed is:
1. A process for cleaning substrates comprising: placing the
substrates to be cleaned in a cleaning vessel; adding organic
solvent to the cleaning vessel; cleaning the substrates with the
organic solvent; removing a portion of the organic solvent from the
cleaning vessel; placing the substrates in a drying vessel; adding
pressurized fluid solvent to the drying vessel; removing the
pressurized fluid solvent from the drying vessel; and removing the
substrates from the drying vessel.
2. The process of claim 1 wherein the substrates being cleaned
comprise textiles.
3. The process of claim 2 wherein the cleaning vessel further
contains a rotatable drum within the cleaning vessel into which the
textiles are placed.
4. The process of claim 3 wherein removing a portion of the organic
solvent from the cleaning vessel further comprises rotating the
drum at sufficient speed to extract the portion of the organic
solvent from the textiles.
5. The process of claim 2 wherein removing the pressurized fluid
solvent from the drying vessel further comprises the step of
depressurizing the drying vessel to vaporize at least a portion of
the pressurized fluid solvent.
6. The process of claim 5 wherein the drying vessel further
comprises a rotatable drum within the drying vessel into which the
textiles are placed.
7. The process of claim 6 wherein removing the pressurized fluid
solvent from the drying vessel further comprises the step of
rotating the drum at sufficient speed to extract a portion of the
pressurized fluid solvent from the textiles before the drying
vessel is depressurized.
8. The process of claim 1 wherein the organic solvent: is soluble
in carbon dioxide between 600 and 1050 pounds per square inch and
between 5 and 30 degrees Celsius; has an evaporation rate of lower
than 30 (based on n-butyl acetate=100); has a dispersion Hansen
solubility parameter of between 7.2 (cal/cm.sup.3).sup.1/2 and 8.1
(cal/cm.sup.3).sup.1/2; has a polar Hansen solubility parameter of
between 2.0 (cal/cm.sup.3).sup.1/2 and 4.8 (cal/cm.sup.3).sup.1/2;
and has a hydrogen bonding Hansen solubility parameter of between
4.0 (cal/cm.sup.3).sup.1/2 and 7.3 (cal/cm.sup.3).sup.1/2.
9. The process of claim 8 wherein the organic solvent further: has
a specific gravity of greater than 0.7; and has a flash point
greater than 200 degrees Fahrenheit.
10. The process of claim 9 wherein the pressurized fluid solvent is
densified carbon dioxide.
11. The process of claim 1 wherein the organic solvent is a glycol
ether.
12. The process of claim 1 wherein the organic solvent is a poly
glycol ether.
13. The process of claim 1 wherein the organic solvent is selected
from a group including dipropylene glycol n-butyl ether,
tripropylene glycol n-butyl ether, tripropylene glycol methyl
ether, and mixtures thereof.
14. The process of claim 1 wherein the organic solvent comprises a
combination of organic solvent and pressurized fluid solvent.
15. A process for cleaning substrates comprising: placing the
substrates to be cleaned in a vessel; adding organic solvent to the
vessel; cleaning the substrates with the organic solvent; removing
a portion of the organic solvent from the vessel; adding
pressurized-fluid solvent to the vessel; removing the pressurized
fluid solvent from the vessel; and removing the substrates from the
vessel.
16. The process of claim 15 wherein the substrates being cleaned
comprise textiles.
17. The process of claim 15 wherein the vessel further contains a
rotatable drum within the vessel into which the textiles are
placed.
18. The process of claim 17 wherein removing a portion of the
organic solvent from the vessel further comprises rotating the drum
at sufficient speed to extract the portion of the organic solvent
from the textiles.
19. The process of claim 17 wherein removing a portion of the
pressurized fluid solvent from the vessel further comprises the
step of depressurizing the vessel to vaporize the remaining
pressurized fluid solvent.
20. The process of claim 19 wherein removing a portion of the
pressurized fluid solvent from the vessel further comprises the
step of rotating the drum at sufficient speed to extract a portion
of the pressurized fluid solvent from the textiles before the
vessel is depressurized.
21. The process of claim 15 wherein the organic solvent: is soluble
in carbon dioxide between 600 and 1050 pounds per square inch and
between 5 and 30 degrees Celsius; has an evaporation rate of lower
than 30 (based on n-butyl acetate=100); has a dispersion Hansen
solubility parameter of between 7.2 (cal/cm.sup.3).sup.1/2 and 8.1
(cal/cm.sup.3).sup.1/2; has a polar Hansen solubility parameter of
between 2.0 (cal/cm.sup.3).sup.1/2 and 4.8 (cal/cm.sup.3).sup.1/2;
and has a hydrogen bonding Hansen solubility parameter of between
4.0 (cal/cm.sup.3).sup.1/2 and 7.3 (cal/cm.sup.3).sup.1/2.
22. The process of claim 21 wherein the organic solvent further:
has a specific gravity of greater than 0.7; and has a flash point
greater than 200 degrees Fahrenheit.
23. The process of claim 22 wherein the pressurized fluid solvent
is densified carbon dioxide.
24. The process of claim 15 wherein the organic solvent is a glycol
ether.
25. The process of claim 15 wherein the organic solvent is a poly
glycol ether.
26. The process of claim 15 wherein the organic solvent is selected
from a group including dipropylene glycol n-butyl ether,
tripropylene glycol n-butyl ether, tripropylene glycol methyl
ether, and mixtures thereof.
27. The process of claim 13 wherein the organic solvent comprises a
combination of organic solvent and pressurized fluid solvent.
28. A process for cleaning textiles comprising: placing the
textiles to be cleaned into a cleaning drum within a cleaning
vessel; adding organic solvent to the cleaning vessel; cleaning the
textiles with the organic solvent; removing a portion of the
organic solvent from the cleaning vessel; rotating the cleaning
drum to extract a portion of the organic solvent from the textiles;
placing the textiles into a drying drum within a pressurizable
drying vessel; adding pressurized fluid solvent to the drying
vessel; removing a portion of the pressurized fluid solvent from
the drying vessel; rotating the drying drum to extract a portion of
the pressurized fluid solvent from the textiles; depressurizing the
drying vessel to remove the remainder of the carbon dioxide by
evaporation; and removing the textiles from the drying drum.
29. A system for cleaning substrates comprising: a cleaning vessel
adapted to hold contaminated substrates and organic solvent; an
organic solvent tank operatively connected to the cleaning vessel;
a pump for pumping organic solvent from the organic solvent tank to
the cleaning vessel; a drying vessel adapted to hold cleaned
substrates and pressurized fluid solvent; a carbon dioxide tank
operatively connected to the drying vessel; and a pump for pumping
pressurized fluid solvent from the carbon dioxide tank to the
drying vessel.
30. The system of claim 29 wherein the substrates comprise
textiles.
31. The system of claim 30 wherein the cleaning vessel further
comprises a rotatable drum within the cleaning vessel adapted to
hold textiles.
32. The system of claim 31 wherein the rotatable drum is adapted to
rotate at sufficient speed to extract a portion of the organic
solvent from the textiles.
33. The system of claim 30 wherein the drying vessel further
comprises a rotatable drum within the drying vessel adapted to hold
textiles.
34. The system of claim 33 wherein the rotatable drum is adapted to
rotate at sufficient speed to extract a portion of the pressurized
fluid solvent from the textiles.
35. The system of claim 29 wherein the organic solvent: is soluble
in carbon dioxide between 600 and 1050 pounds per square inch and
between 5 and 30 degrees Celsius; has an evaporation rate of lower
than 30 (based-on n-butyl acetate=100); has a dispersion Hansen
solubility parameter of between 7.2 (cal/cm.sup.3).sup.1/2 and 8.1
(cal/cm.sup.3).sup.1/2; has a polar Hansen solubility parameter of
between 2.0 (cal/cm.sup.3).sup.1/2 and 4.8 (cal/cm.sup.3).sup.1/2;
and has a hydrogen bonding Hansen solubility parameter of between
4.0 (cal/cm.sup.3).sup.1/2 and 7.3 (cal/cm.sup.3).sup.1/2.
36. The system of claim 35 wherein the organic solvent further: has
a specific gravity of greater than 0.7; and has a flash point
greater than 200 degrees Fahrenheit.
37. The system of claim 36 wherein the pressurized fluid solvent is
densified carbon dioxide.
38. The system of claim 29 wherein the organic solvent is a glycol
ether.
39. The system of claim 29 wherein the organic solvent is a poly
glycol ether.
40. The system of claim 29 wherein the organic solvent is selected
from a group including dipropylene glycol n-butyl ether,
tripropylene glycol n-butyl ether, tripropylene glycol methyl
ether, and mixtures thereof.
41. A system for cleaning substrates comprising: a vessel adapted
to hold substrates, organic solvent, and pressurized fluid solvent;
an organic solvent tank operatively connected to the vessel; a pump
for pumping organic solvent from the organic solvent tank to the
vessel; a pressurized fluid solvent tank operatively connected to
the vessel; and a pump for pumping pressurized fluid solvent from
the pressurized fluid solvent tank to the vessel.
42. The system of claim 41 wherein the substrates comprise
textiles.
43. The system of claim 42 wherein the vessel further comprises a
rotatable drum within the vessel adapted to hold textiles.
44. The system of claim 43 wherein the rotatable drum is adapted to
rotate at sufficient speed to extract a portion of the organic
solvent and a portion of the pressurized fluid solvent from the
textiles.
45. The system of claim 41 wherein the organic solvent: is soluble
in carbon dioxide between 600 and 1050 pounds per square inch and
between 5 and 30 degrees Celsius; has an evaporation rate of lower
than 30 (based on n-butyl acetate=100); has a dispersion Hansen
solubility parameter of between 7.2 (cal/cm.sup.3).sup.1/2 and 8.1
(cal/cm.sup.3).sup.1/2; has a polar Hansen solubility parameter of
between 2.0 (cal/cm.sup.3).sup.1/2 and 4.8 (cal/cm.sup.3).sup.1/2;
and has a hydrogen bonding Hansen solubility parameter of between
4.0 (cal/cm.sup.3).sup.1/2 and 7.3 (cal/cm.sup.3).sup.1/2.
46. The system of claim 45 wherein the organic solvent further: has
a specific gravity of greater than 0.7; and has a flash point
greater than 200 degrees Fahrenheit.
47. The system of claim 46 wherein the pressurized fluid solvent is
densified carbon dioxide.
48. The system of claim 41 wherein the organic solvent is a glycol
ether.
49. The system of claim 41 wherein the organic solvent is a poly
glycol ether.
50. The system of claim 41 wherein the organic solvent is selected
from a group including dipropylene glycol n-butyl ether,
tripropylene glycol n-butyl ether, tripropylene glycol methyl ether
and mixtures thereof.
51. A system for cleaning textiles comprising: a cleaning vessel
adapted to retain textiles and organic solvent and able to agitate
the textiles and the organic solvent; an organic solvent tank
operatively connected to the cleaning vessel; a drying vessel
adapted to retain textiles and pressurized fluid solvent and able
to agitate the textiles and the pressurized fluid solvent; and a
pressurized fluid solvent tank operatively connected to the drying
vessel.
52. A system for cleaning textiles comprising: a pressurizable
vessel adapted to retain textiles and organic solvent and
pressurized fluid solvent and able to agitate the textiles and the
organic solvent and the pressurized fluid solvent; an organic
solvent tank operatively connected to the pressurizable vessel; and
a pressurized fluid solvent tank operatively connected to the
pressurizable vessel.
53. A system for cleaning substrates comprising a cleaning vessel
adapted to hold contaminated substrates and organic solvent; an
organic solvent tank operatively connected to the cleaning vessel
and containing organic solvent; means for moving organic solvent
from the organic solvent tank to the cleaning vessel; a drying
vessel adapted to hold cleaned substrates and pressurized fluid
solvent; a pressurized fluid solvent tank operatively connected to
the drying vessel and containing pressurized fluid solvent; and
means for moving pressurized fluid solvent from the pressurized
fluid solvent tank to the drying vessel.
54. The system of claim 53 wherein the substrates comprise
textiles.
55. The system of claim 54 wherein the cleaning vessel further
comprises an agitation means for agitating the cleaning vessel
adapted to hold textiles and the organic solvent.
56. The system of claim 55 wherein the agitation means is adapted
to agitate the cleaning vessel to extract a portion of the organic
solvent from the textiles.
57. The system of claim 54 wherein the cleaning vessel is adapted
to depressurize so as to vaporize at least a portion of the
pressurized fluid solvent.
58. The system of claim 53 wherein the organic solvent: is soluble
in carbon dioxide between 600 and 1050 pounds per square inch and
between 5 and 30 degrees Celsius;. has an evaporation rate of lower
than 30 (based on n-butyl acetate=100); has a dispersion Hansen
solubility parameter of between 7.2 (cal/cm.sup.3).sup.1/2 and 8.1
(cal/cm.sup.3).sup.1/2; has a polar Hansen solubility parameter of
between 2.0 (cal/cm.sup.3).sup.1/2 and 4.8 (cal/cm.sup.3).sup.1/2;
and has a hydrogen bonding Hansen solubility parameter of between
4.0 (cal/cm.sup.3).sup.1/2 and 7.3 (cal/cm.sup.3).sup.1/2.
59. The system of claim 58 wherein the organic solvent further: has
a specific gravity of greater than 0.7; and has a flash point
greater than 200 degrees Fahrenheit.
60. The system of claim 59 wherein the pressurized fluid solvent is
densified carbon dioxide.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] The present invention relates generally to cleaning systems,
and more specifically to substrate cleaning systems, such as
textile cleaning systems, utilizing an organic cleaning solvent and
a pressurized fluid solvent.
[0003] 2. Related Art
[0004] A variety of methods and systems are known for cleaning
substrates such as textiles, as well as other flexible, precision,
delicate, or porous structures that are sensitive to soluble and
insoluble contaminants. These known methods and systems typically
use water, perchloroethylene, petroleum, and other solvents that
are liquid at or substantially near atmospheric pressure and room
temperature for cleaning the substrate.
[0005] Such conventional methods and systems generally have been
considered satisfactory for their intended purpose. Recently,
however, the desirability of employing these conventional methods
and systems has been questioned due to environmental, hygienic,
occupational hazard, and waste disposal concerns, among other
things. For example, perchloroethylene frequently is used as a
solvent to clean delicate substrates, such as textiles, in a
process referred to as "dry cleaning." Some locales require that
the use and disposal of this solvent be regulated by environmental
agencies, even when only trace amounts of this solvent are to be
introduced into waste streams.
[0006] Furthermore, there are significant regulatory burdens placed
on solvents such as perchloroethylene by agencies such as the EPA,
OSHA and DOT. Such regulation results in increased costs to the
user, which, in turn, are passed to the ultimate consumer. For
example, filters that have been used in conventional
perchloroethylene dry cleaning systems must be disposed of in
accordance with hazardous waste or other environmental regulations.
Certain other solvents used in dry cleaning, such as hydrocarbon
solvents, are extremely flammable, resulting in greater
occupational hazards to the user and increased costs to control
their use.
[0007] In addition, textiles that have been cleaned using
conventional cleaning methods are typically dried by circulating
hot air through the textiles as they are tumbled in a drum. The
solvent must have a relatively high vapor pressure and low boiling
point to be used effectively in a system utilizing hot air drying.
The heat used in drying may permanently set some stains in the
textiles. Furthermore, the drying cycle adds significant time to
the overall processing time. During the conventional drying
process, moisture adsorbed on the textile fibers is often removed
in addition to the solvent. This often results in the development
of undesirable static electricity and shrinkage in the garments.
Also, the textiles are subject to greater wear due to the need to
tumble the textiles in hot air for a relatively long time.
Conventional drying methods are inefficient and often leave excess
residual solvent in the textiles, particularly in heavy textiles,
components constructed of multiple fabric layers, and structural
components of garments such as shoulder pads. This may result in
unpleasant odors and, in extreme cases, may cause irritation to the
skin of the wearer. In addition to being time consuming and of
limited efficiency, conventional drying results in significant loss
of cleaning solvent in the form of fugitive solvent vapor. Finally,
conventional hot air drying is an energy intensive process that
results in relatively high utility costs and accelerated equipment
wear.
[0008] Traditional cleaning systems may utilize distillation in
conjunction with filtration and adsorption to remove soils
dissolved and suspended in the cleaning solvent. The filters and
adsorptive materials become saturated with solvent, therefore,
disposal of some filter waste is regulated by state or federal
laws. Solvent evaporation especially during the drying cycle is one
of the main sources of solvent loss in conventional systems.
Reducing solvent loss improves the environmental and economic
aspects of cleaning substrates using cleaning solvents. It is
therefore advantageous to provide a method and system for cleaning
substrates that utilize a solvent having less adverse attributes
than those solvents currently used and reduces solvent losses.
[0009] As an alternative to conventional cleaning solvents,
pressurized fluid solvents or densified fluid solvents have been
used for cleaning various substrates, wherein densified fluids are
widely understood to encompass gases that are pressurized to either
subcritical or supercritical conditions so as to achieve a liquid
or a supercritical fluid having a density approaching that of a
liquid. In particular, some patents have disclosed the use of a
solvent such as carbon dioxide that is maintained in a liquid state
or either a subcritical or supercritical condition for cleaning
such substrates as textiles, as well as other flexible, precision,
delicate, or porous structures that are sensitive to soluble and
insoluble contaminants.
[0010] For example, U.S. Pat. No. 5,279,615 discloses a process for
cleaning textiles using densified carbon dioxide in combination
with a non-polar cleaning adjunct. The preferred adjuncts are
paraffin oils such as mineral oil or petrolatum. These substances
are a mixture of alkanes including a portion of which are C.sub.16
or higher hydrocarbons. The process uses a heterogeneous cleaning
system formed by the combination of the adjunct which is applied to
the textile prior to or substantially at the same time as the
application of the densified fluid. According to the data disclosed
in U.S. Pat. No. 5,279,615, the cleaning adjunct is not as
effective at removing soil from fabric as conventional cleaning
solvents or as the solvents described for use in the present
invention as disclosed below.
[0011] U.S. Pat. No. 5,316,591 discloses a process for cleaning
substrates using liquid carbon dioxide or other liquefied gases
below their critical temperature. The focus of this patent is on
the use of any one of a number of means to effect cavitation to
enhance the cleaning performance of the liquid carbon dioxide. In
all of the disclosed embodiments, densified carbon dioxide is the
cleaning medium. This patent does not describe the use of a solvent
other than the liquefied gas for cleaning substrates. While the
combination of ultrasonic cavitation and liquid carbon dioxide may
be well suited to processing complex hardware and substrates
containing extremely hazardous contaminants, this process is too
costly for the regular cleaning of textile substrates. Furthermore,
the use of ultrasonic cavitation is less effective for removing
contaminants from textiles than it is for removing contaminants
from hard surfaces.
[0012] U.S. Pat. No. 5,377,705 discloses a process for cleaning
precision parts utilizing a liquefied pressurized gas in the
supercritical state and an environmentally acceptable co-solvent.
During this process, the parts to be cleaned are pre-treated with
the co-solvent and then placed in the cleaning vessel. Afterwards,
the contaminants and co-solvent are removed from the parts by
circulating a pressurized gas in its supercritical state through
the vessel. Redeposition of co-solvent and contaminants is
controlled by the amount of pressurized gas that is pumped through
the vessel. Co-solvents specified for use in conjunction with the
cleaning solvent include aliphatics, terpenes, acetone, laminines,
isopropyl alcohol, Axarel (DuPont), Petroferm (Petroferm, Inc.),
kerosene, and Isopar-m (Exxon). During the cleaning process, the
cleaning solvent (supercritical carbon dioxide) flows through a
vessel containing the parts to be treated, through a filter or
filters and directly to a separator in which the solvent is
evaporated and recondensed. The disclosed co-solvents for use in
this patent have high evaporation rates and low flash points. The
use of such co-solvents results in high solvent losses, and high
fire risks. Furthermore, many of the co-solvents are not compatible
with common dyes and fibers used in textile manufacture. Also, the
use of supercritical carbon dioxide necessitates the use of more
expensive equipment.
[0013] U.S. Pat. No. 5,417,768 discloses a process for precision
parts cleaning using a two-solvent system. One solvent can be
liquid at room temperature and pressure while the second solvent
can be supercritical carbon dioxide. The objectives of this
invention include using two or more solvents with minimal mixing of
the solvents and to incorporate ultrasonic cavitation in such a way
as to prevent the ultrasonic transducers from coming in contact
with the first-mentioned solvent. An apparatus is described which
consists of an open top vessel within a covered pressurized vessel.
The primary fluid is pumped into the open top vessel. After
cleaning with the primary fluid, it is pumped from the open top
vessel. Pressurized carbon dioxide is then pumped into the open top
vessel and flushed through the vessel until the level of
contaminants within the vessel are reduced to the desired level.
The co-solvents disclosed in this patent are the same solvents
specified in U.S. Pat. No. 5,377,705. Use of these solvents would
introduce a high risk of fire, high levels of solvent loss and
potential damage to a wide range of textiles.
[0014] U.S. Pat. No. 5,888,250 discloses the use of a binary
azeotrope comprised of propylene glycol tertiary butyl ether and
water as an environmentally attractive replacement for
perchlorethylene in dry cleaning and degreasing processes. While
the use of propylene glycol tertiary butyl ether is attractive from
an environmental regulatory point of view, its use as disclosed in
this invention is in a conventional dry cleaning process using
conventional dry cleaning equipment and a conventional evaporative
hot air drying cycle. As a result, it has many of the same
disadvantages as conventional dry cleaning processes described
above.
[0015] Several of the pressurized fluid solvent cleaning methods
described in the above patents may lead to recontamination of the
substrate and degradation of efficiency because the contaminated
solvent is not continuously purified or removed from the system.
Furthermore, pressurized fluid solvent alone is not as effective at
removing some types of soil as are conventional cleaning solvents.
Consequently, pressurized fluid solvent cleaning methods require
individual treatment of stains and heavily soiled areas of
textiles, which is a labor-intensive process. Furthermore, systems
that utilize pressurized fluid solvents for cleaning are more
expensive and complex to manufacture and maintain than conventional
cleaning systems. Finally, few if any conventional surfactants can
be used effectively in pressurized fluid solvents. The surfactants
and additives that can be used in pressurized fluid solvent
cleaning systems are much more expensive than those used in
conventional cleaning systems.
[0016] There thus remains a need for an efficient and economic
method and system for cleaning substrates that incorporates the
benefits of prior systems, and minimizes the difficulties
encountered with each. There also remains a need for a method and
system in which the hot air drying time is eliminated, or at least
reduced, thereby reducing the wear on the substrate and preventing
stains from being permanently set on the substrate.
SUMMARY
[0017] In the present invention, certain types of organic solvents,
such as glycol ethers and, specifically, poly glycol ethers
including dipropylene glycol n-butyl ether, tripropylene glycol
n-butyl ether or tripropylene glycol methyl ether, or similar
solvents or mixtures of such solvents are used. Any type of organic
solvent that falls within the range of properties disclosed
hereinafter may be used. However, unlike conventional cleaning
systems, in the present invention, a conventional drying cycle is
not necessary. Instead, the system utilizes the solubility of the
organic solvent in pressurized fluid solvents, as well as the
physical properties of pressurized fluid solvents, to dry the
substrate being cleaned.
[0018] As used herein, the term "pressurized fluid solvent" refers
to both pressurized liquid solvents and densified fluid solvents.
The term "pressurized liquid solvent" as used herein refers to
solvents that are liquid at between approximately 600 and 1050
pounds per square inch and between approximately 5 and 30 degrees
Celsius, but are gas at atmospheric pressure and room temperature.
The term "densified fluid solvent" as used herein refers to a gas
or gas mixture that is compressed to either subcritical or
supercritical conditions so as to achieve either a liquid or a
supercritical fluid having density approaching that of a liquid.
Preferably, the pressurized fluid solvent used in the present
invention is an inorganic substance such as carbon dioxide, xenon,
nitrous oxide, or sulfur hexafluoride. Most preferably, the
pressurized fluid solvent is densified carbon dioxide.
[0019] The substrates are cleaned in a perforated drum within a
vessel in a cleaning cycle using an organic solvent. A perforated
drum is preferred to allow for free interchange of solvent between
the drum and vessel as well as to transport soil from the
substrates to the filter. After substrates have been cleaned in the
perforated drum, the organic solvent is extracted from the
substrates by rotating the cleaning drum at high speed within the
cleaning vessel in the same way conventional solvents are extracted
from substrates in conventional cleaning machines. However, instead
of proceeding to a conventional evaporative hot air drying cycle,
the substrates are immersed in pressurized fluid solvent to extract
the residual organic solvent from the substrates. This is possible
because the organic solvent is soluble in the pressurized fluid
solvent. After the substrates are immersed in pressurized fluid
solvent, which may also serve as a cleaning solvent, the
pressurized fluid solvent is transferred from the drum. Finally,
the vessel is de-pressurized to atmospheric pressure to evaporate
any remaining pressurized fluid solvent, yielding clean,
solvent-free substrates.
[0020] Glycol ethers, specifically poly glycol ethers, used in the
present invention tend to be soluble in pressurized fluid solvents
such as supercritical or subcritical carbon dioxide so that a
conventional hot air drying cycle is not necessary. The types of
poly glycol ethers used in conventional cleaning systems must have
a reasonably high vapor pressure and a low boiling point because
they must be removed from the substrates by evaporation in a stream
of hot air. However, solvents, particularly non-halogenated
solvents, that have a high vapor pressure and a low boiling point
generally also have a low flash point. From a safety standpoint,
organic solvents used in cleaning substrates should have a flash
point that is as high as possible, or preferably, it should have no
flash point. By eliminating the conventional hot air evaporative
drying process, a wide range of solvents can be used in the present
invention that have much lower evaporation rates, higher boiling
points and higher flash points than those used in conventional
cleaning systems.
[0021] Thus, the cleaning system described herein utilizes solvents
that are less regulated and less combustible, and that efficiently
remove different soil types typically deposited on textiles through
normal use. The cleaning system reduces solvent consumption and
waste generation as compared to conventional dry cleaning systems.
Machine and operating costs are reduced as compared to currently
used pressurized fluid solvent systems, and conventional additives
may be used in the cleaning system.
[0022] Furthermore, one of the main sources of solvent loss from
conventional dry cleaning systems, which occurs in the evaporative
hot air drying step, is substantially reduced or eliminated
altogether. Because the conventional evaporative hot air drying
process is eliminated, there are no heat set stains on the
substrates, risk of fire and/or explosion is reduced, the cleaning
cycle time is reduced, and residual solvent in the substrates is
substantially reduced or eliminated. Substrates are also subject to
less wear, less static electricity build-up and less shrinkage
because there is no need to tumble the substrates in a stream of
hot air to dry them.
[0023] While systems according to the present invention utilizing
pressurized fluid solvent to remove organic solvent can be
constructed as wholly new systems, existing conventional solvent
systems can also be converted to utilize the present invention. An
existing conventional solvent system can be used to clean
substrates with organic solvent, and an additional pressurized
chamber for drying substrates with pressurized fluid solvent can be
added to the existing system.
[0024] Therefore, according to the present invention, textiles are
cleaned by placing the textiles to be cleaned into a cleaning drum
within a cleaning vessel, adding an organic solvent to the cleaning
vessel, cleaning the textiles with the organic solvent, removing a
portion of the organic solvent from the cleaning vessel, rotating
the cleaning drum to extract a portion of the organic solvent from
the textiles, placing the textiles into a drying drum within a
pressurizable drying vessel, adding a pressurized fluid solvent to
the drying vessel, removing a portion of the pressurized fluid
solvent from the drying vessel, rotating the drying drum to extract
a portion of the pressurized fluid solvent from the textiles,
depressurizing the drying vessel to remove the remainder of the
pressurized fluid solvent by evaporation, and removing the textiles
from the depressurized vessel.
[0025] These and other features and advantages of the invention
will be apparent upon consideration of the following detailed
description of the presently preferred embodiment of the invention,
taken in conjunction with the claims and appended drawings, as well
as will be learned by practice of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a block diagram of a cleaning system utilizing
separate vessels for cleaning and drying.
[0027] FIG. 2 is a block diagram of a cleaning system utilizing a
single vessel for cleaning and drying.
DETAILED DESCRIPTION
[0028] Reference will now be made in detail to embodiments of the
invention, examples of which are illustrated in the accompanying
drawings. The steps of each method for cleaning and drying a
substrate will be described in conjunction with the detailed
description of the system.
[0029] The methods and systems presented herein may be used for
cleaning a variety of substrates. The present invention is
particularly suited for cleaning substrates such as textiles, as
well as other flexible, precision, delicate, or porous structures
that are sensitive soluble an insoluble contaminants. The term
"textile" is inclusive of, but not limited to, woven or non-woven
materials, as well as articles therefrom. Textiles include, but are
not limited to, fabrics, articles of clothing, protective covers,
carpets, upholstery, furniture and window treatments. For purposes
of explanation and illustration, and not limitation, exemplary
embodiments of a system for cleaning textiles in accordance with
the invention are shown in FIGS. 1 and 2.
[0030] As noted above, the pressurized fluid solvent used in the
present invention is either a pressurized liquid solvent or a
densified fluid solvent. Although a variety of solvents may be
used, it is preferred that an inorganic substance such as carbon
dioxide, xenon, nitrous oxide, or sulfur hexafluoride, be used as
the pressurized fluid solvent. For cost and environmental reasons,
liquid, supercritical, or subcritical carbon dioxide is the
preferred pressurized fluid solvent.
[0031] Furthermore, to maintain the pressurized fluid solvent in
the appropriate fluid state, the internal temperature and pressure
of the system must be appropriately controlled relative to the
critical temperature and pressure of the pressurized fluid solvent.
For example, the critical temperature and pressure of carbon
dioxide is approximately 31 degrees Celsius and approximately 73
atmospheres, respectively. The temperature may be established and
regulated in a conventional manner, such as by using a heat
exchanger in combination with a thermocouple or similar regulator
to control temperature. Likewise, pressurization of the system may
be performed using a pressure regulator and a pump and/or
compressor in combination with a pressure gauge. These components
are conventional and are not shown in FIGS. 1 and 2 as placement
and operation of these components are known in the art.
[0032] The system temperature and pressure may be monitored and
controlled either manually, or by a conventional automated
controller (which may include, for example, an appropriately
programmed computer or appropriately constructed microchip) that
receives signals from the thermocouple and pressure gauge, and then
sends corresponding signals to the heat exchanger and pump and/or
compressor, respectively. Unless otherwise noted, the temperature
and pressure is appropriately maintained throughout the system
during operation. As such, elements contained within the system are
constructed of sufficient size and material to withstand the
temperature, pressure, and flow parameters required for operation,
and may be selected from, or designed using, any of a variety of
presently available high pressure hardware.
[0033] In the present invention, the preferred organic solvent
should have a flash point of greater than 200.degree. F. to allow
for increased safety and less governmental regulation, have a low
evaporation rate to minimize fugitive emissions, be able to remove
soils consisting of insoluble particulate soils and solvent soluble
oils and greases, and prevent or reduce redeposition of soil onto
the textiles being cleaned.
[0034] Preferably, the organic solvent in the present invention is
a glycol ether, and specifically a poly glycol ether such as
dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether
or tripropylene glycol methyl ether, or any combination of one or
more of these. Additionally, any organic solvent or mixture of
organic solvents exhibiting the following physical properties is
suitable for use in the present invention: (1) soluble in carbon
dioxide at a pressure of between about 600 and about 1050 pounds
per square inch and at a temperature of between about 5 and about
30 degrees Celsius; (2) specific gravity of greater than about 0.7
(the higher the density, the better the organic solvent); and (3)
Hansen solubility parameters of about 7.2-8.1
(cal/cm.sup.3).sup.1/2 for dispersion, about 2.0-4.8
(cal/cm.sup.3).sup.1/2 for polar, and about 4.0-7.3
(cal/cm.sup.3).sup.1/2 for hydrogen bonding (based on values cited
in Publication No. M-167P from Eastman Chemical Products).
Preferably, in addition to the above three physical properties, the
organic solvent used in the present invention should also exhibit
one or more of the following physical properties: (4) flash point
greater than about 200 degrees Fahrenheit; and (5) evaporation rate
of lower than about 30 (where n-butyl acetate=100). Most
preferably, the organic solvent used in the present invention
exhibits each of the foregoing characteristics (i.e., those
identified as (1) through (5)).
[0035] The Hansen solubility parameters were developed to
characterize solvents for the purpose of comparison. Each of the
three parameters (i.e., dispersion, polar and hydrogen bonding)
represents a different characteristic of solvency. In combination,
the three parameter are a measure of the overall strength and
selectivity of a solvent. The above Hansen solubility parameter
ranges identify solvents that are good solvents for a wide range of
substances and also exhibit a degree of solubility in liquid carbon
dioxide. The Total Hansen solubility parameter, which is the square
root of the sum of the squares of the three parameters mentioned
previously, provides a more general description of the solvency of
the organic solvents.
[0036] Dipropylene glycol n-butyl ether, tripropylene glycol
n-butyl ether and tripropylene glycol methyl ether all fall within
all of the above parameters; however, any organic solvent or
mixture of organic solvents that meet at least properties 1 through
3, and preferably all 5 properties, is suitable for use in the
present invention. Furthermore, the organic solvent should also
have a low toxicity and a low environmental impact. Table 1 below
shows the physical properties of a number of organic solvents that
may be suitable for use in the present invention.
1TABLE 1 Soluble Evaporation Hansen Solubility Parameters in
Specific Flash Rate Hydrogen carbon Gravity Point (n-butyl
Dispersion Polar Bonding Total Solvent dioxide (20.degree.
C./20.degree. C.) (.degree. F.) acetate = 100)
(cal/cm.sup.3).sup.1/2 (cal/cm.sup.3).sup.1/2
(cal/cm.sup.3).sup.1/2 (cal/cm.sup.3).sup.1/2 Ethylene Yes 0.931
110 30 7.9 4.5 7.0 11.5 Glycol Ethyl Ether Ethylene Yes 0.973 130
20 7.8 2.3 5.2 9.7 Glycol Ethyl Ether Acetate Diethylene Yes 0.956
222 0.3 7.8 3.4 5.2 10.0 Glycol Butyl Ether Propylene Yes 0.872 113
25 7.5 3.0 5.3 9.6 Glycol t-butyl (25.degree. C./25.degree. C.)
Ether Dipropylene Yes 0.951 167 2 7.6 2.8 5.5 9.8 Glycol Methyl
Ether Tripropylene Yes 0.962 232 0.2 7.4 3.0 5.7 9.8 Glycol Methyl
Ether Dipropylene Yes 0.912 214 0.4 7.4 2.2 5.5 9.5 Glycol n-Butyl
Ether Dipropylene Yes 0.922 190 1.3 7.4 2.4 5.7 9.6 Glycol n-
Propyl Ether Tripropylene Yes 0.934 255 0.029 7.4 2.4 5.1 9.3
Glycol n-Butyl Ether
[0037] In Table 1, the solvents are soluble in carbon dioxide
between 570 psig/5.degree. C. and 830 psig/20.degree. C. The flash
point was measured using Tag Closed Cup for ethylene glycol ethyl
ether and ethylene glycol ethyl ether acetate; using SETA Flash for
diethylene glycol butyl ether, propylene glycol t-butyl ether,
dipropylene glycol methyl ether, tripropylene glycol methyl, ether,
dipropylene glycol n-butyl ether, and dipropylene glycol n-propyl
ether; and using Pensky Martens Closed Cup for tripropylene glycol
n-butyl ether. The values for the evaporation rate are based on
n-butyl acetate=100. Finally, the specific gravity, flash point,
evaporation rate and Hansen solubility parameters were obtained
from Publication No. M-167P from Eastman Chemical Products for
ethylene glycol ethyl ether, ethylene glycol ethyl ether acetate,
diethylene glycol butyl ether, and propyleneglycol t-butyl ether;
from "Products for Cleaners and the Personal Care Industry," Arco
Chemicals (1997), for dipropylene glycol methyl ether, tripropylene
glycol methyl ether, dipropylene glycol n-butyl ether, and
dipropylene glycol n-propyl ether; and from Lyondell Chemical
Company for tripropylene glycol n-butyl ether.
[0038] Referring now to FIG. 1, a block diagram of a cleaning
system having separate vessels for cleaning and drying textiles is
shown. The cleaning system 100 generally comprises a cleaning
machine 102 having a cleaning vessel 110 operatively connected to,
via one or more motor activated shafts (not shown), a perforated
rotatable cleaning drum or wheel 112 within the cleaning vessel 110
with an inlet 114 to the cleaning vessel 110 and an outlet 116 from
the cleaning vessel 110 through which cleaning fluids can pass. A
drying machine 104 has a drying vessel 120 capable of being
pressurized. The pressurizable drying vessel 120 is operatively
connected to, via one or more motor activated shafts (not shown), a
perforated rotatable drying drum or wheel 122 within the drying
vessel 120 with an inlet 124 to the drying vessel 120 and an outlet
126 from the drying vessel 120 through which pressurized fluid
solvent can pass. The cleaning vessel 110 and the drying vessel 120
can either be parts of the same machine, or they can comprise
separate machines. Furthermore, both the cleaning and drying steps
of this invention can be performed in the same vessel, as is
described with respect to FIG. 2 below.
[0039] An organic solvent tank 130 holds any suitable organic
solvent, as previously described, to be introduced to the cleaning
vessel 110 through the inlet 114. A pressurized fluid solvent tank
132 holds pressurized fluid solvent to be added to the
pressurizable drying vessel 120 through the inlet 124. Filtration
assembly 140 contains one or more filters that continuously remove
contaminants from the organic solvent from the cleaning vessel 110
as cleaning occurs.
[0040] The components of the cleaning system 100 are connected with
lines 150-156, which transfer organic solvents and vaporized and
pressurized fluid solvents between components of the system. The
term "line" as used herein is understood to refer to a piping
network or similar conduit capable of conveying fluid and, for
certain purposes, is capable of being pressurized. The transfer of
the organic solvents and vaporized and pressurized fluid solvents
through the lines 150-156 is directed by valves 170-176 and pumps
190-193. While pumps 190-193 are shown in the described embodiment,
any method of transferring liquid and/or vapor between components
can be used, such as adding pressure to the component using a
compressor to force the liquid and/or vapor from the component.
[0041] The textiles are cleaned with an organic solvent such as
those previously described or mixtures thereof. The textiles may
also be cleaned with a combination of organic solvent and
pressurized fluid solvent, and this combination may be in varying
proportions from about 50% by weight to 100% by weight of organic
solvent and 0% by weight to 50% by weight of pressurized fluid
solvent. In the cleaning process, the textiles are first sorted as
necessary to place the textiles into groups suitable to be cleaned
together. The textiles may then be spot treated as necessary to
remove any stains that may not be removed during the cleaning
process. The textiles are then placed into the cleaning drum 112 of
the cleaning system 100. It is preferred that the cleaning drum 112
be perforated to allow for free interchange of solvent between the
cleaning drum 112 and the cleaning vessel 110 as well as to
transport soil from the textiles to the filtration assembly
140.
[0042] After the textiles are placed in the cleaning drum 112, an
organic solvent contained in the organic solvent tank 130 is added
to the cleaning vessel 110 via line 152 by opening valve 171,
closing valves 170, 172, 173 and 174, and activating pump 190 to
pump organic solvent through the inlet 114 of the cleaning vessel
110. The organic solvent may contain one or more co-solvents,
water, detergents, or other additives to enhance the cleaning
capability of the cleaning system 100. Alternatively, one or more
additives may be added directly to the cleaning vessel 110.
Pressurized fluid solvent may also be added to the cleaning vessel
10 along with the organic solvent to enhance cleaning. Pressurized
fluid solvent can be added to the cleaning vessel 110 via line 154
by opening valve 174, closing valves 170, 171, 172, 173, and 175,
and activating pump 192 to pump pressurized fluid solvent through
the inlet 114 of the cleaning vessel 110. Of course, if pressurized
fluid solvent is included in the cleaning cycle, the cleaning
vessel 110 will need to be pressurized in the same manner as the
drying vessel 120, as discussed below.
[0043] When a sufficient amount of the organic solvent, or
combination of organic solvent and pressurized fluid solvent, is
added to the cleaning vessel 110, the motor (not shown) is
activated and the perforated cleaning drum 112 is agitated and/or
rotated within cleaning vessel 110. During this phase, the organic
solvent is continuously cycled through the filtration assembly 140
by opening valves 170 and 172, closing valves 171, 173 and 174, and
activating pump 191. Filtration assembly 140 may include one or
more fine mesh filters to remove particulate contaminants from the
organic solvent passing therethrough and may alternatively or in
addition include one or more absorptive or adsorptive filters to
remove water, dyes and other dissolved contaminants from the
organic solvent. Exemplary configurations for filter assemblies
that can be used to remove contaminants from either the organic
solvent or the pressurized fluid solvent are described more fully
in U.S. application Ser. No. 08/994,583 incorporated herein by
reference. As a result, the organic solvent is pumped through
outlet 116, valve 172, line 151, filter assembly 140, line 150,
valve 170 and re-enters the cleaning vessel 110 via inlet 114. This
cycling advantageously removes contaminants, including particulate
contaminants and/or soluble contaminants, from the organic solvent
and reintroduces filtered organic solvent to the cleaning vessel
110 and agitating or rotating cleaning drum 112. Through this
process, contaminants are removed from the textiles. Of course, in
the event the cleaning vessel 110 is pressurized, this
recirculation system will be maintained at the same
pressure/temperature levels as those in cleaning vessel 110.
[0044] After sufficient time has passed so that the desired level
of contaminants is removed from the textiles and organic solvent,
the organic solvent is removed from the cleaning drum 112 and
cleaning vessel 110 by opening valve 173, closing valves 170, 171,
172 and 174, and activating pump 191 to pump the organic solvent
through outlet 116 via line 153. The cleaning drum 112 is then
rotated at a high speed, such as 400-800 rpm, to further remove
organic solvent from the textiles. The cleaning drum 112 is
preferably perforated so that, when the textiles are rotated in the
cleaning drum 112 at a high speed, the organic solvent can drain
from the cleaning drum 112. Any organic solvent removed from the
textiles by rotating the cleaning drum 112 at high speed is also
removed from the cleaning drum 112 in the manner described above.
After the organic solvent is removed from the cleaning drum 112, it
can either be discarded or recovered and decontaminated for reuse
using solvent recovery systems known in the art. Furthermore,
multiple cleaning cycles can be used if desired, with each cleaning
cycle using the same organic solvent or different organic solvents.
If multiple cleaning cycles are used, each cleaning cycle can occur
in the same cleaning vessel, or a separate cleaning vessel can be
used for each cleaning cycle.
[0045] After a desired amount of the organic solvent is removed
from the textiles by rotating the cleaning drum 112 at high speed,
the textiles are moved from the cleaning drum 112 to the drying
drum 122 within the drying vessel 120 in the same manner textiles
are moved between machines in conventional cleaning systems. In an
alternate embodiment, a single drum can be used in both the
cleaning cycle and the drying cycle, so that, rather than
transferring the textiles between the cleaning drum 112 and the
drying drum 122, a single drum containing the textiles is
transferred between the cleaning vessel 110 and the drying vessel
120. If the cleaning vessel 110 is pressurized during the cleaning
cycle, it must be depressurized before the textiles are removed.
Once the textiles have been placed in the drying drum 122,
pressurized fluid solvent, such as that contained in the carbon
dioxide tank 132, is added to the drying vessel 120 via lines 154
and 155 by opening valve 175, closing valves 174 and 176, and
activating pump 192 to pump pressurized fluid solvent through the
inlet 124 of the drying vessel 120 via lines 154 and 155. When
pressurized fluid solvent is added to the drying vessel 120, the
organic solvent remaining on the textiles dissolves in the
pressurized fluid solvent.
[0046] After a sufficient amount of pressurized fluid solvent is
added so that the desired level of organic solvent has been
dissolved, the pressurized fluid solvent and organic solvent
combination is removed from the drying vessel 120, and therefore
also from the drying drum 122, by opening valve 176, closing valve
175 and activating pump 193 to pump the pressurized fluid solvent
and organic solvent combination through outlet 126 via line 156. If
desired, this process may be repeated to remove additional organic
solvent. The drying drum 122 is then rotated at a high speed, such
as 150-350 rpm, to further remove the pressurized fluid solvent and
organic solvent combination from the textiles. The drying drum 122
is preferably perforated so that, when the textiles are rotated in
the drying drum 122 at a high speed, the pressurized fluid solvent
and organic solvent combination can drain from the drying drum 122.
Any pressurized fluid solvent and organic solvent combination
removed from the textiles by spinning the drying drum 122 at high
speed is also pumped from the drying vessel 120 in the manner
described above. After the pressurized fluid solvent and organic
solvent combination is removed from the drying vessel 120, it can
either be discarded or separated and recovered for reuse with
solvent recovery systems known in the art. Note that, while
preferred, it is not necessary to include a high speed spin cycle
remove pressurized fluid solvent from the textiles.
[0047] After a desired amount of the pressurized fluid solvent is
removed from the textiles by rotating the drying drum 122, the
drying vessel 120 is depressurized over a period of about 5-15
minutes. The depressurization of the drying vessel 120 vaporizes
any remaining pressurized fluid solvent, leaving dry, solvent-free
textiles in the drying drum 122. The pressurized fluid solvent that
has been vaporized is then removed from the drying vessel 120 by
opening valve 176, closing valve 175, and activating pump 193. As a
result, the vaporized pressurized fluid solvent is pumped through
the outlet 126, line 156 and valve 176, where it can then either be
vented to the atmosphere or recovered and recompressed for
reuse.
[0048] While the cleaning system 100 has been described as a
complete system, an existing conventional dry cleaning system may
be converted for use in accordance with the present invention. To
convert a conventional dry cleaning system, the organic solvent
described above is used to clean textiles in the conventional
system. A separate pressurized vessel is added to the conventional
system for drying the textiles with pressurized fluid solvent.
Thus, the conventional system is converted for use with a
pressurized fluid solvent. For example, the system in FIG. 1 could
represent such a converted system, wherein the components of the
cleaning machine 102 are conventional, and the pressurized fluid
solvent tank 132 is not in communication with the cleaning vessel
100. In such a situation, the drying machine 104 is the add-on part
of the conventional cleaning machine.
[0049] Furthermore, while the system shown in FIG. 1 comprises a
single cleaning vessel, multiple cleaning vessels could be used, so
that the textiles are subjected to multiple cleaning steps, with
each cleaning step carried out in a different cleaning vessel using
the same or different organic solvents in each step. The
description of the single cleaning vessel is merely for purposes of
description and should not be construed as limiting the scope of
the invention.
[0050] Referring now to FIG. 2, a block diagram of an alternate
embodiment of the present invention, a cleaning system having a
single chamber for cleaning and drying the textiles, is shown. The
cleaning system 200 generally comprises a cleaning machine having a
pressurizable vessel 210. The vessel 210 is operatively connected
to, via one or more motor activated shafts (not shown), a
perforated rotatable drum or wheel 212 within the vessel 210 with
an inlet 214 to the vessel 210 and an outlet 216 from the vessel
210 through which dry cleaning fluids can pass.
[0051] An organic solvent tank 220 holds any suitable organic
solvent, such as those described above, to be introduced to the
vessel 210 through the inlet 214. A pressurized fluid solvent tank
222 holds pressurized fluid solvent to be added to the vessel 210
through the inlet 214. Filtration assembly 224 contains one or more
filters that continuously remove contaminants from the organic
solvent from the vessel 210 and drum 212 as cleaning occurs.
[0052] The components of the cleaning system 200 are connected with
lines 230-234 that transfer organic solvents and vaporized and
pressurized fluid solvent between components of the system. The
term "line" as used herein is understood to refer to a piping
network or similar conduit capable of conveying fluid and, for
certain purposes, is capable of being pressurized. The transfer of
the organic solvents and vaporized and pressurized fluid solvent
through the lines 230-234 is directed by valves 250-254 and pumps
240-242. While pumps 240-242 are shown in the described embodiment,
any method of transferring liquid and/or vapor between components
can be used, such as adding pressure to the component using a
compressor to force the liquid and/or vapor from the component.
[0053] The textiles are cleaned with an organic solvent such as
those previously described. The textiles may also be cleaned with a
combination of organic solvent and pressurized fluid solvent, and
this combination may be in varying proportions of 50-100% by weight
organic solvent and 0-50% by weight pressurized fluid solvent. In
the cleaning process, the textiles are first sorted as necessary to
place the textiles into groups suitable to be cleaned together. The
textiles may then be spot treated as necessary to remove any stains
that may not be removed during the cleaning process. The textiles
are then placed into the drum 212 within the vessel 210 of the
cleaning system 200. It is preferred that the drum 212 be
perforated to allow for free interchange of solvent between the
drum 212 and the vessel 210 as well as to transport soil from the
textiles to the filtration assembly 224.
[0054] After the textiles are placed in the drum 212, an organic
solvent contained in the organic solvent tank 220 is added to, the
vessel 210 via line 231 by opening valve 251, closing valves 250,
252, 253 and 254, and activating pump 242 to pump organic solvent
through the inlet 214 of the vessel 210. The organic solvent may
contain one or more co-solvents, detergents, water, or other
additives to enhance the cleaning capability of the cleaning system
200. Alternatively, one or more additives may be added directly to
the vessel. Pressurized fluid solvent may also be added to the
vessel 210 along with the organic solvent to enhance cleaning. The
pressurized fluid solvent is added to the vessel 210 via line 230
by opening valve 250, closing valves 251, 252, 253 and 254, and
activating pump 240 to pump the pressurized fluid solvent through
the inlet 214 of the vessel 210.
[0055] When the desired amount of the organic solvent, or
combination of organic solvent and pressurized fluid solvent as
described above, is added to the vessel 210, the motor (not shown)
is activated and the drum 212 is agitated and/or rotated. During
this phase, the organic solvent, as well as pressurized fluid
solvent if used in combination, is continuously cycled through the
filtration assembly 224 by opening valves 252 and 253, closing
valves 250, 251 and 254, and activating pump 241. Filtration
assembly 224 may include one or more fine mesh filters to remove
particulate contaminants from the organic solvent and pressurized
fluid solvent passing therethrough and may alternatively or in
addition include one or more absorptive or adsorptive filters to
remove water, dyes, and other dissolved contaminants from the
organic solvent. Exemplary configurations for filter assemblies
that can be used to remove contaminants from either the organic
solvent or the pressurized fluid solvent are described more fully
in U.S. application Ser. No. 08/994,583 incorporated herein by
reference. As a result, the organic solvent is pumped through
outlet 216, valve 253, line 233, filter assembly 224, line 232,
valve 252 and reenters the vessel 210 via inlet 214. This cycling
advantageously removes contaminants, including particulate
contaminants and/or soluble contaminants, from the organic solvent
and pressurized fluid solvent and reintroduces filtered solvent to
the vessel 210. Through this process, contaminants are removed from
the textiles.
[0056] After sufficient time has passed so that the desired level
of contaminants is removed from the textiles and solvents, the
organic solvent is removed from the vessel 210 and drum 212 by
opening valve 254, closing valves 250, 251, 252 and 253, and
activating pump 241 to pump the organic solvent through outlet 216
and line 234. If pressurized fluid solvent is used in combination
with organic solvent, it may be necessary to first separate the
pressurized fluid solvent from the organic solvent. The organic
solvent can then either be discarded or, preferably, contaminants
may be removed from the organic solvent and the organic solvent
recovered for further use. Contaminants may be removed from the
organic solvent with solvent recovery systems known in the art. The
drum 212 is then rotated at a high speed, such as 400-800 rpm, to
further remove organic solvent from the textiles. The drum 212 is
preferably perforated so that, when the textiles are rotated in the
drum 212 at a high speed, the organic solvent can drain from the
cleaning drum 212. Any organic solvent removed from the textiles by
rotating the drum 212 at high speed can also either be discarded or
recovered for further use.
[0057] After a desired amount of organic solvent is removed from
the textiles by rotating the drum 212, pressurized fluid solvent
contained in the pressurized fluid tank 222 is added to the vessel
210 by opening valve 250, closing valves 251, 252, 253 and 254, and
activating pump 240 to pump pressurized fluid solvent through the
inlet 214 of the pressurizable vessel 210 via line 230. When
pressurized fluid solvent is added to the vessel 210, organic
solvent remaining on the textiles dissolves in the pressurized
fluid solvent.
[0058] After a sufficient amount of pressurized fluid solvent is
added so that the desired level of organic solvent has been
dissolved, the pressurized fluid solvent and organic solvent
combination is removed from the vessel 210 by opening valve 254,
closing valves 250, 251, 252 and 253, and activating pump 241 to
pump the pressurized fluid solvent and organic solvent combination
through outlet 216 and line 234. Note that pump 241 may actually
require two pumps, one for pumping the low pressure organic solvent
in the cleaning cycle and one for pumping the pressurized fluid
solvent in the drying cycle.
[0059] The pressurized fluid solvent and organic solvent
combination can then either be discarded or the combination may be
separated and the organic solvent and pressurized fluid solvent
separately recovered for further use. The drum 212 is then rotated
at a high speed, such as 150-350 rpm to further remove pressurized
fluid solvent and organic solvent combination from the textiles.
Any pressurized fluid solvent and organic solvent combination
removed from the textiles by spinning the drum 212 at high speed
can also either be discarded or retained for further use. Note
that, while preferred, it is not necessary to include a high speed
spin cycle to remove pressurized fluid solvent from the
textiles.
[0060] After a desired amount of the pressurized fluid solvent is
removed from the textiles by rotating the drum 212, the vessel 210
is depressurized over a period of about 5-15 minutes. The
depressurization of the vessel 210 vaporizes the pressurized fluid
solvent, leaving dry, solvent-free textiles in the drum 212. The
pressurized fluid solvent that has been vaporized is then removed
from the vessel 210 by opening valve 254, closing valves 250, 251,
252 and 253, and activating pump 241 to pump the vaporized
pressurized fluid solvent through outlet 216 and line 234. Note
that while a single pump is shown as pump 241, separate pumps may
be necessary to pump organic solvent, pressurized fluid solvent and
pressurized fluid solvent vapors, at pump 241. The remaining
vaporized pressurized fluid solvent can then either be vented into
the atmosphere or compressed back into pressurized fluid solvent
for further use.
[0061] As discussed above, dipropylene glycol n-butyl ether,
tripropylene glycol n-butyl ether and tripropylene glycol methyl
ether are the preferred organic solvents for use in the present
invention, as shown in the test results below. Table 2 shows
results of detergency testing for each of a number of solvents that
may be suitable for use in the present invention. Table 3 shows
results of testing of drying and extraction of those solvents using
densified carbon dioxide.
[0062] Detergency tests were performed using a number of different
solvents without detergents, co-solvents, or other additives. The
solvents selected for testing include organic solvents and liquid
carbon dioxide. Two aspects of detergency were investigated--soil
removal and soil redeposition. The former refers to the ability of
a solvent to remove soil from a substrate while the latter refers
to the ability of a solvent to prevent soil from being redeposited
on a substrate during the cleaning process. Wascherei Forschungs
Institute, Krefeld Germany ("WFK") standard soiled swatches that
have been stained with a range of insoluble materials and WFK white
cotton swatches, both obtained from TESTFABRICS, Inc., were used to
evaluate soil removal and soil redeposition, respectively.
[0063] Soil removal and redeposition for each solvent was
quantified using the Delta Whiteness Index. This method entails
measuring the Whiteness Index of each swatch before and after
processing. The Delta Whiteness Index is calculated by subtracting
the Whiteness Index of the swatch before processing from the
Whiteness Index of the swatch after processing. The Whiteness Index
is a function of the light reflectance of the swatch and in this
application is an indication of the amount of soil on the swatch.
More soil results in a lower light reflectance and Whiteness Index
for the swatch. The Whiteness indices were measured using a
reflectometer manufactured by Hunter Laboratories.
[0064] Organic solvent testing was carried out in a Launder-Ometer
while the densified carbon dioxide testing was carried out in a
Parr Bomb. After measuring their Whiteness Indices, two WFK
standard soil swatches and two WFK white cotton swatches were
placed in a Launder-Ometer cup with 25 stainless steel ball
bearings and 150 mL of the solvent of interest. The cup was then
sealed, placed in the Launder-Ometer and agitated for a specified
length of time. Afterwards, the swatches were removed and placed in
a Parr Bomb equipped with a mesh basket. Approximately 1.5 liters
of liquid carbon dioxide between 5.degree. C. and 25.degree. C. and
570 psig and 830 psig was transferred to the Parr Bomb. After
several minutes the Parr Bomb was vented and the dry swatches
removed and allowed to reach room temperature. Testing of densified
carbon dioxide was carried out by placing the swatches in a Parr
Bomb, transferring liquid carbon dioxide at 20.degree. C. and 830
psig to the Parr Bomb. The swatches were fastened to a, wire frame
attached to a rotatable shaft to enable the swatches to be agitated
while immersed in the liquid carbon dioxide. The Whiteness Index of
the processed swatches was determined using the reflectometer. The
two Delta Whiteness Indices obtained for each pair of swatches were
averaged. The results are presented in Table 2.
[0065] Because the Delta Whiteness Index is calculated by
subtracting the Whiteness Index of a swatch before processing from
the Whiteness Index value after processing, a positive Delta
Whiteness Index indicates that there was an increase in Whiteness
Index as a result of processing. In practical terms, this means
that soil was removed during processing. In fact, the higher the
Delta Whiteness Value, the more soil was removed from the swatch
during processing. Each of the organic solvents tested exhibited
significant soil removal. Densified carbon dioxide alone, on the
other hand, exhibited no soil removal. The WFK white cotton
swatches exhibited a decrease in Delta Whiteness Indices indicating
that the soil was deposited on the swatches during the cleaning
process. Therefore, a "less negative" Delta Whiteness Index
suggests that less soil was redeposited. It should be noted that
the seemingly excellent result obtained for densified carbon
dioxide is an anomaly and resulted from the fact that essentially
no soil removal took place and therefore essentially no soil was
present in the solvent which could be deposited on the swatch. The
organic solvents on the other hand, exhibited good soil
redeposition results.
2 TABLE 2 Delta Whiteness Values Cleaning Insoluble Insoluble Time
Soil Soil Solvent (minutes) Removal Redeposition Densified Carbon
Dioxide 20 0.00 -0.54 (at 20.degree. C. and 830 psig) Ethylene
Glycol Ethyl Ether 12 13.87 -5.10 Ethylene Glycol Ethyl Ether 12
16.10 -11.40 Acetate Diethylene Glycol Butyl Ether 12 12.80 -5.11
Propylene Glycol t-butyl Ether 12 14.35 -13.50 Dipropylene Glycol
Methyl Ether 20 11.84 -5.64 Tripropylene Glycol Methyl Ether 12
13.48 -5.60 Dipropylene Glycol n-Butyl Ether 12 13.97 -6.22
Dipropylene Glycol n-Propyl Ether 12 13.15 -7.50 Tripropylene
Glycol n-Butyl Ether 12 13.24 -4.35
[0066] To evaluate the ability of densified carbon dioxide to
extract organic solvent from a substrate, WFK white cotton swatches
were used. One swatch was weighed dry and then immersed in an
organic solvent sample. Excess solvent was removed from the swatch
using a ringer manufactured by Atlas Electric Devices Company. The
damp swatch was re-weighed to determine the amount of solvent
retained in the fabric. After placing the damp swatch in a Parr
Bomb densified carbon dioxide was transferred to the Parr Bomb. The
temperature and pressure of the densified carbon dioxide for all of
the trials ranged from 5.degree. C. to 20.degree. C. and from 570
psig-830 psig. After five minutes the Parr Bomb was vented and the
swatch removed. The swatch was next subjected to Soxhlet extraction
using methylene chloride for a minimum of two hours. This apparatus
enables the swatch to be continuously extracted to remove the
organic solvent from the swatch. After determining the
concentration of the organic solvent in the extract using gas
chromatography, the amount of organic solvent remaining on the
swatch after exposure to densified carbon dioxide was calculated by
multiplying the concentration of the organic solvent in the extract
by the volume of the extract. A different swatch was used for each
of the tests. The results of these tests are included in Table 3.
As the results indicate, the extraction process using densified
carbon dioxide is extremely effective.
3 TABLE 3 Weight of Percentage Weight of Densified by Weight of
Solvent on Test Carbon Solvent Swatch (grams) Dioxide Removed
Before After Used from Solvent Extraction Extraction (kilograms)
Swatch Ethylene Glycol 1.8718 0.0069 1.35 99.63 Ethyl Ether
Ethylene Glycol 1.9017 0.0002 1.48 99.99 Ethyl Ether Acetate
Diethylene Glycol 1.9548 0.0033 1.72 99.83 Butyl Ether Propylene
Glycol 2.0927 0.0010 1.24 99.95 t-butyl Ether Dipropylene Glycol
2.1209 0.0005 1.31 99.98 Methyl Ether Tripropylene Glycol 1.9910
0.0022 1.71 99.89 Methyl Ether Dipropylene Glycol 1.8005 0.0023
1.77 99.87 n-Butyl Ether Dipropylene Glycol 1.7096 0.0034 1.59
99.80 n-Butyl Ether Dipropylene Glycol 1.7651 0.0018 3.36 99.90
n-Butyl Ether Dipropylene Glycol 1.7958 0.0012 1.48 99.94 n-Propyl
Ether Tripropylene Glycol 1.8670 0.0034 1.30 99.82 n-Butyl
Ether
[0067] It is to be understood that a wide range of changes and
modifications to the embodiments described above will be apparent
to those skilled in the art and are contemplated. It is, therefore,
intended that the foregoing detailed description be regarded as
illustrative rather than limiting, and that it be understood that
it is the following claims, including all equivalents, that are
intended to define the spirit and scope of the invention.
* * * * *