Cleaning system utilizing an organic cleaning solvent and a pressurized fluid solvent Number:7,435,265 from the United States Patent and Trademark Office (PTO) owispatent 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 selected from terpenes, halohydrocarbons, certain glycol ethers, polyols, ethers, esters of glycol ethers, esters of fatty acids and other long chain carboxylic acids, fatty alcohols and other long-chain alcohols, short-chain alcohols, polar aprotic solvents, siloxanes, hydrofluoroethers, dibasic esters, and aliphatic hydrocarbons solvents or similar solvents or mixtures of such solvents and the pressurized fluid solvent is preferably densified carbon dioxide.<H pressurized, utilizing, Cleaning, system, 7435265.html, Patent, pto, 7435265

Title: 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 selected from terpenes, halohydrocarbons, certain glycol ethers, polyols, ethers, esters of glycol ethers, esters of fatty acids and other long chain carboxylic acids, fatty alcohols and other long-chain alcohols, short-chain alcohols, polar aprotic solvents, siloxanes, hydrofluoroethers, dibasic esters, and aliphatic hydrocarbons solvents or similar solvents or mixtures of such solvents and the pressurized fluid solvent is preferably densified carbon dioxide.

Patent Number: 7,435,265 Issued on 10/14/2008 to Damaso, et al.

Inventors: Damaso; Gene R. (Northlake, IL), Schulte; James E. (Cicero, IL), Racette; Timothy L. (Plainfield, IL)
Assignee: R.R Street & Co. Inc. (Naperville, IL)

Appl. No.: 10/804,338

Filed: March 18, 2004

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
09837849	Apr., 2001	6755871
09419345	Oct., 1999	6355072

Current U.S. Class: 8/142 ; 8/158

Current International Class: B08B 11/00 (20060101)

Field of Search: 8/142,156

References Cited [Referenced By]

U.S. Patent Documents


210965	December 1878	Schultz et al.
3701627	October 1972	Gruenewalder
3966981	June 1976	Schultz
4012194	March 1977	Maffei
4129718	December 1978	Muzzio
4309300	January 1982	Danforth et al.
4619706	October 1986	Squires et al.
4824762	April 1989	Kobayashi et al.
4973423	November 1990	Geke et al.
5158704	October 1992	Fulton et al.
5266205	November 1993	Fulton et al.
5279615	January 1994	Mitchell et al.
5306350	April 1994	Hoy et al.
5316591	May 1994	Chao et al.
5370742	December 1994	Mitchell et al.
5377705	January 1995	Smith, Jr. et al.
5417768	May 1995	Smith, Jr. et al.
5456759	October 1995	Stanford, Jr. et al.
5486314	January 1996	Wack et al.
5574002	November 1996	Shiino et al.
5610132	March 1997	Momoda et al.
5676705	October 1997	Jureller et al.
5683473	November 1997	Jureller et al.
5683977	November 1997	Jureller et al.
5733380	March 1998	Murphy
5738127	April 1998	Heymanns et al.
5746776	May 1998	Smith et al.
5759209	June 1998	Adler et al.
5783082	July 1998	DeSimone et al.
5789505	August 1998	Wilkinson et al.
5858022	January 1999	Romack et al.
5865852	February 1999	Berndt
5866005	February 1999	DeSimone et al.
5868856	February 1999	Douglas et al.
5868862	February 1999	Douglas et al.
5888250	March 1999	Hayday et al.
5942007	August 1999	Berndt et al.
5943721	August 1999	Lerette et al.
5944996	August 1999	DeSimone et al.
5977045	November 1999	Murphy
6012307	January 2000	Malchow
6051421	April 2000	Sauer et al.
6090771	July 2000	Burt et al.
6120613	September 2000	Romack et al.
6148644	November 2000	Jureller et al.
6148645	November 2000	DeYoung et al.
6156074	December 2000	Hayday et al.
6200352	March 2001	Romack et al.
6204237	March 2001	Suzuki et al.
6211422	April 2001	DeSimone et al.
6258766	July 2001	Romack et al.
6273919	August 2001	Hayday
6280481	August 2001	Storey-Laubach et al.
6344243	February 2002	McClain et al.
6350287	February 2002	Hayday
6355072	March 2002	Racette et al.
6491730	December 2002	Cauble et al.
6558432	May 2003	Schulte et al.
6673120	January 2004	Hayday
6711773	March 2004	DeYoung et al.
6734154	May 2004	Flynn et al.
6736859	May 2004	Racette et al.
6755871	June 2004	Damaso et al.
6802961	October 2004	Jackson
7008458	March 2006	Hayday
7087094	August 2006	Galick et al.
7147670	December 2006	Schulte et al.
2004/0168262	September 2004	Racette et al.
2004/0173246	September 2004	Damaso et al.
2004/0231371	November 2004	Scheper et al.
2005/0044636	March 2005	Galick et al.
2006/0207035	September 2006	Hayday

Foreign Patent Documents


1092803	Apr., 2001	EP
WO 9401227	Jan., 1994	WO
WO96/15304	May., 1996	WO
WO 9738044	Oct., 1997	WO
WO 9949122	Sep., 1999	WO
WO 0050145	Aug., 2000	WO
WO 0056970	Sep., 2000	WO
WO 0106053	Jan., 2001	WO
WO 0129305	Apr., 2001	WO
WO 0129306	Apr., 2001	WO
WO 02086223	Oct., 2002	WO

Other References

US 6,001,133, 12/1999, DeYoung et al. (withdrawn) cited by other .
International Search Report (PCT/US 02/12239) (Apr. 18, 2002). cited by other .
Dyck, et al., Supercritical Carbon Dioxide Solvent Extraction from Surface-Micromachined Microchemical Structures, SPIE Michomachining and Microfabrication (Oct. 1996). cited by other.

Primary Examiner: Webb; Gregory E
Attorney, Agent or Firm: Howrey LLP Fournier; David B.

Parent Case Text

This application is a division of U.S. patent application Ser. No. 09/837,849, filed on Apr. 18, 2001, which is a continuation-in-part of U.S. patent application Ser. No. 09/419,345 (Now U.S. Pat. No. 6,355,072) filed on Oct. 15, 1999.

Claims

What is claimed is:

1. A system for cleaning substrates comprising: a non-pressurizable cleaning vessel adapted to hold contaminated substrates and organic solvent; an organic solvent tank operatively connected to the cleaning vessel; a pump or compressor for moving organic solvent from the organic solvent tank to the cleaning vessel; a pressurizable drying vessel adapted to hold cleaned substrates and pressurized fluid solvent; a pressurized fluid solvent tank operatively connected to the drying vessel; and a pump or compressor for moving pressurized fluid solvent from the pressurized fluid solvent tank to the drying vessel.

2. The system of claim 1 further comprising a cleaning unit within the non-pressurizable cleaning vessel.

3. The system of claim 2 wherein the cleaning unit is operatively connected to the non-pressurizable cleaning vessel.

4. The system of claim 3 wherein the cleaning unit is rotatable.

5. The system of claim 3 wherein the cleaning unit is perforated.

6. The system of claim 3 wherein the cleaning unit comprises a drum or a wheel.

7. The system of claim 3 wherein the cleaning unit is operatively connected to the non-pressurizable cleaning vessel via one or more motor activated shafts.

8. The system of claim 1 wherein the non-pressurizable cleaning vessel comprises an inlet and an outlet through which cleaning fluids can pass.

9. The system of claim 1 further comprising a filtration assembly operatively connected to the non-pressurizable cleaning vessel.

10. The system of claim 1 wherein the filtration assembly comprises at least one filter selected from a mesh filter, and adsorptive filter or an absorptive filter.

11. The system of claim 1 further comprising a drying unit within the pressurizable drying vessel.

12. The system of claim 11 wherein the drying unit is operatively connected to the pressurizable drying vessel.

13. The system of claim 12 wherein the drying unit is rotatable.

14. The system of claim 12 wherein the drying unit is perforated.

15. The system of claim 12 wherein the drying unit comprises a drum or a wheel.

16. The system of claim 12 wherein the drying unit is operatively connected to the pressurized drying vessel via one or more motor activated shafts.

17. The system of claim 1 wherein the pressurizable drying vessel comprises an inlet and an outlet through which pressurized fluids can pass.

18. The system of claim 1 wherein the organic solvent tank contains an organic solvent.

19. The system of claim 18 wherein the organic solvent comprises a glycol ether, a cyclic terpene, a halocarbon, a polyol, an ether, an ester of a glycol ether, a fatty alcohol, a short chain alcohol, a siloxane, a hydrofluoroether, an aliphatic hydrocarbon, an ester of dibasic carboxylic acids, a ketone, an aprotic solvent or mixtures thereof.

20. The system of claim 19 wherein the organic solvent comprises a glycol ether.

21. The system of claim 20 wherein the glycol ether: is soluble in carbon dioxide between 600 and 1050 pounds per square inch and between 5 and 30 degrees Celsius; has a specific gravity of greater than approximately 0.800; has a dispersion Hansen solubility parameter of between 13.0 (MPa).sup.1/2 and 19.5 (MPa).sup.1/2; has a polar Hansen solubility parameter of between 3.0 (MPa).sup.1/2 and 7.5 (MPa).sup.1/2; and has a hydrogen bonding Hansen solubility parameter of between 8.0 (MPa).sup.1/2 and 17.0 (MPa).sup.1/2.

22. The system of claim 20 wherein the glycol ether has an evaporation rate of lower than 50 (based on n-butyl acetate=100) and has a flash point greater than 100 degrees Fahrenheit.

23. The system of claim 1 wherein the pressurized fluid solvent tank comprises pressurized fluid solvent.

24. The system of claim 23 wherein the pressurized fluid solvent comprises carbon dioxide, xenon, nitrous oxide, or sulfur hexaflouride.

25. The system of claim 23 wherein the pressurized fluid solvent comprises carbon dioxide.

26. The system of claim 25 wherein the carbon dioxide is densified.

Description

BACKGROUND

1. Field of the Invention

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.

2. Related Art

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.

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.

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.

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. The heating required to evaporate combustible solvents in a conventional drying process increases the risk of fire and/or explosions. In many cases, heating the solvent will necessitate explosion-proof components and other expensive safety devices to minimize the risk of fire and explosions. Finally, conventional hot air drying is an energy intensive process that results in relatively high utility costs and accelerated equipment wear.

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 utilizes a solvent having less adverse attributes than those solvents currently used and reduces solvent losses.

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.

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 is 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.

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.

U.S. Pat. No. 5,377,705, issued to Smith et al., discloses a system designed to clean parts utilizing supercritical carbon dioxide and an environmentally friendly co-solvent. Parts to be cleaned are placed in a cleaning vessel along with the co-solvent. After adding super critical carbon dioxide, mechanical agitation is applied via sonication or brushing. Loosened contaminants are then flushed from the cleaning vessel using additional carbon dioxide. Use of this system in the cleaning of textiles is neither suggested nor disclosed. Furthermore, use of this system for the cleaning of textiles would result in redeposition of loosened soil and damage to some fabrics.

U.S. Pat. No. 5,417,768, issued to Smith et al., discloses a process for precision cleaning of a work piece using a multi-solvent system in which one of the solvents is liquid or supercritical carbon dioxide. The process results in minimal mixing of the solvents and incorporates ultrasonic cavitation in such a way as to prevent the ultrasonic transducers from coming in contact with cleaning solvents that could degrade the piezoelectric transducers. Use of this system in the cleaning of textiles is neither suggested nor disclosed. In fact, its use in cleaning textiles would result in redeposition of loosened soil and damage to some fabrics.

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.

U.S. Pat. No. 6,200,352 discloses a process for cleaning substrates in a. cleaning mixture comprising carbon dioxide, water, surfactant, and organic co-solvent. This process uses carbon dioxide as the primary cleaning media with the other components included to enhance the overall cleaning effectiveness of the process. There is no suggestion of a separate, low pressure cleaning step followed by the use of densified fluid to remove the cleaning solvent. As a result, this process has many of the same cost and cleaning performance disadvantages of other liquid carbon dioxide cleaning processes. Additional patents have been issued to the assignee of U.S. Pat. No. 6,200,352 covering related subject matter. All of these patents disclose processes in which liquid carbon dioxide is the cleaning, solvent. Consequently, these processes have the same cost and cleaning performance disadvantages.

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.

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

In the present invention, certain types of organic solvents, such as terpenes, halohydrocarbons, certain glycol ethers, polyols, ethers, esters of glycol ethers, esters of fatty acids and other long chain carboxylic acids, fatty alcohols and other long-chain alcohols, short-chain alcohols, polar aprotic solvents, siloxanes, hydrofluoroethers, dibasic esters, and aliphatic hydrocarbons solvents or similar solvents or mixtures of such solvents are used in cleaning substrates. Any type of organic solvent that falls within the range of properties disclosed hereinafter may be used to clean substrates. However, unlike conventional cleaning systems, in the present invention, a conventional drying cycle is not performed. 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.

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.

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, 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.

The solvents 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 solvents used in conventional cleaning systems must have reasonably high vapor pressures and low boiling points because they must be removed from the substrates by evaporation in a stream of hot air. However, 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. For situations where the desired solvent has a relatively low flash point, the elimination of the hot air evaporative drying cycle significantly increases the level of safety with respect to fire and explosions.

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.

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.

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.

Therefore, according to the present invention, textiles to be cleaned are placed in 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.

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

FIG. 1 is a block diagram of a cleaning system utilizing separate vessels for cleaning and drying.

FIG. 2 is a block diagram of a cleaning system utilizing a single vessel for cleaning and drying.

DETAILED DESCRIPTION

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.

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 to soluble and insoluble contaminants. The term "textile" is inclusive of, but not limited to, woven or non-woven materials, as well as articles made 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.

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.

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.

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.

In the present invention, the preferred organic solvent should have a flash point of greater than 100 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.

Preferably, the organic solvents suitable for use in the present invention include any of the following alone or in combination: 1. Cyclic terpenes, specifically, .alpha.-terpene isomers, pine oil, .alpha.-pinene isomers, and d-limonene. Additionally, any cyclic terpene exhibiting the following physical characteristics is suitable for use in the present invention; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater than about 0.800 (the higher the specific gravity the better the organic solvent); (3) Hansen solubility parameters of about 13.0-17.5 (MPa).sup.1/2 for dispersion, about 0.5-9.0 (MPa).sup.1/2 for polar, and about 0.0-10.5 (MPa).sup.1/2 for hydrogen bonding. 2. Halocarbons, specifically, chlorinated, fluorinated and brominated hydrocarbons exhibiting the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater than about 1.100 (the higher the specific gravity the better the organic solvent); (3) Hansen solubility parameters of about 10.0-17.0 (MPa).sup.1/2 for dispersion, about 0.0-7.0 (MPa).sup.1/2 for polar, and about 0.0-5.0 (MPa).sup.1/2 for hydrogen bonding. 3. Glycol ethers, specifically, mono-, di-, triethylene and mono-, di- and tripropylene glycol ethers exhibiting the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater than about 0.800 (the higher the specific gravity the better the organic solvent); (3) Hansen solubility parameters of about 13.0-19.5 (MPa).sup.1/2 for dispersion, about 3.0-7.5 (MPa).sup.1/2 for polar, and about 8.0-17.0 (MPa).sup.1/2 for hydrogen bonding. 4. Polyols, specifically, glycols and other organic compounds containing two or more hydroxyl radicals and exhibiting the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater than about 0.920 (the higher the specific gravity the better the organic solvent); (3) Hansen solubility parameters of about 14.0-18.2 (MPa).sup.1/2 for dispersion, about 4.5-20.5 (MPa).sup.1/2 for polar, and about 15.0-30.0 (MPa).sup.1/2 for hydrogen bonding. 5. Ethers, specifically, ethers containing no free hydroxyl radicals and exhibiting the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater than about 0.800 (the higher the specific gravity the better the organic solvent); (3) Hansen solubility parameters of about 14.5-20.0 (MPa).sup.1/2 for dispersion, about 1.5-6.5 (MPa).sup.1/2 for polar, and about 5.0-10.0 (MPa).sup.1/2 for hydrogen bonding. 6. Esters of glycol ethers, specifically, esters of glycol ethers exhibiting the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater than about 0.800 (the higher the specific gravity the better the organic solvent); (3) Hansen solubility parameters of about 15.0-20.0 (MPa).sup.1/2 for dispersion, about 3.0-10.0 (MPa).sup.1/2 for polar, and about 8.0-16.0 (MPa).sup.1/2 for hydrogen bonding. 7. Esters of monobasic carboxylic acids exhibiting the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater than about 0.800 (the higher the specific gravity the better the organic solvent); (3) Hansen solubility parameters of about 13.0-17.0 (MPa).sup.1/2 for dispersion, about 2.0-7.5 (MPa).sup.1/2 for polar, and about 1.5-6.5 (MPa).sup.1/2 for hydrogen bonding. 8. Fatty alcohols, specifically alcohols in which the carbon chain adjacent to the hydroxyl group contains five carbon atoms or more and exhibiting the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater than about 0.800 (the higher the specific gravity the better the organic. solvent); (3) Hansen solubility parameters of about 13.3-18.4 (MPa).sup.1/2 for dispersion, about 3.1-18.8 (MPa).sup.1/2 for polar, and about 8.4-22.3 (MPa).sup.1/2 for hydrogen bonding. 9. Short chain alcohols in which the carbon chain adjacent to the hydroxyl group contains four or fewer carbon atoms and exhibiting the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater than about 0.800 (the higher the specific gravity the better the organic solvent); (3) Hansen solubility parameters of about 13.5-18.0 (MPa).sup.1/2 for dispersion, about 3.0-9.0 (MPa).sup.1/2 for polar, and about 9.0-16.5 (MPa).sup.1/2 for hydrogen bonding. 10. Siloxanes exhibiting the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater than about 0.900 (the higher the specific gravity the better the organic solvent); (3) Hansen solubility parameters of about 14.0-18.0 (MPa).sup.1/2 for dispersion, about 0.0-4.5 (MPa).sup.1/2 for polar, and about 0.0-4.5 (MPa).sup.1/2 for hydrogen bonding. 11. Hydrofluoroethers exhibiting the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and 30 degrees Celsius; (2) specific gravity of greater than about 1.50; (3) total Hansen solubility parameters of about 12.0 to 18.0 (MPa).sup.1/2 for dispersion, about 4.0-10.0 (MPa).sup.1/2 for polar, and about 1.5-9.0 (MPa),.sup.1/2 for hydrogen bonding. 12. Aliphatic hydrocarbons exhibiting the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater-than about 0.700 (the higher the specific gravity the better the organic solvent); (3) Hansen solubility parameters of about 14.0-17.0 (MPa).sup.1/2 for dispersion, about 0.0-2.0 (MPa).sup.1/2 for polar, and about 0.0-2.0 (MPa).sup.1/2 for hydrogen bonding. 13. Esters of dibasic carboxylic acids exhibiting the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater than about 0.900 (the higher the specific gravity the better the organic solvent); (3) Hansen solubility parameters of about 13.5-18.0 (MPa),.sup.1/2 for dispersion, about 4.0-6.5 (MPa).sup.1/2 for polar, and about 4.0-11.0 (MPa).sup.1/2 for hydrogen bonding. 14. Ketones exhibiting the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater than about 0.800 (the higher the specific gravity the better the organic solvent); (3) Hansen solubility parameters of about 13.0-19.0 (MPa).sup.1/2 for dispersion, about 3.0-8.0 (MPa).sup.1/2 for polar, and about 3.0-11.0 (MPa).sup.1/2 for hydrogen bonding. 15. Aprotic solvents. These include solvents that do not belong to any of the aforementioned solvent groups, contain no dissociable hydrogens, and exhibit the following physical characteristics; (1) soluble in carbon dioxide at a pressure of between 600 and about 1050 pounds per square inch and at-a temperature of between 5 and about 30 degrees Celsius; (2) specific gravity of greater than about 0.900 (the higher the specific gravity the better the organic solvent); (3) Hansen solubility parameters of about 15.0-21.0 (MPa).sup.1/2 for dispersion, about 6.0-17.0 (MPa).sup.1/2 for polar, and about 4.0-13.0 (MPa).sup.1/2 for hydrogen bonding.

Preferably, in addition to the three physical properties described with respect to each above group, 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 100 degrees Fahrenheit; and (5) evaporation rate of lower than about 50 (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)).

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 parameters 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.

Any organic solvent or mixture of organic solvents from the groups specified and 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. In Table 1, the solvents are soluble in carbon dioxide between 570 psig/5.degree. C. and 830 psig/20.degree. C.

TABLE-US-00001 TABLE 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) (MPa).sup.1/2 (MPa).sup.1/2 (MPa).sup.1/2 (MPa).sup.1/2 Terpenes Pine Oil y .929.sup.a 193.sup.a 0.5.sup.a 13.9.sup.a 8.0.sup.a 10.2.sup.a 19.0.sup.a d-limonene y .843.sup.c 121.sup.c 0.5.sup.c 16.6.sup.c 0.6.sup.c 0.0.sup.c 16.6.sup.c (25.degree. C./25.degree. C.) Halocarbons 1,1,2-trifluoro- y 1.57.sup.b none.sup.b 2100.sup.b 14.7.sup.b 1.6.sup.b 0- .0.sup.b 14.7.sup.b trichloroethane n-propyl y 1.35 none 5.8 16.0.sup.h 6.5.sup.h 4.7.sup.h 17.9 bromide (25.degree. C./25.degree. C.) Perfluorohexane y 1.67.sup.f none.sup.f 1000.sup.d 12.1.sup.d 0.0.sup.d 0.- 0.sup.d 12.1 Glycol Ethers Triethylene y 0.92@ >200.sup.d <1.sup.d 13.3.sup.a 3.1.sup.a 8.4.sup.a 16.0.sup.a glycol monooleyl 15.5.degree. C. ether Ethylan HB4* y 1.12 >200.sup.d <0.5.sup.d 17.4.sup.d 9.2.sup.d 13.0.sup.d 23.6.sup.d Polyols Hexylene y .921.sup.b 201.sup.b 1.0.sup.b 15.8.sup.b 8.4.sup.b 17.8.sup.b 25.2 glycol Ethers Tetraethylene y 1.005.sup.b 285.sup.b ~<0.5.sup.d 15.7.sup.b 2.0.sup.b 8.2.sup.b 17.8.sup.b glycol dimethyl ether Esters of Glycol Ethers Ethylene y 1.124.sup.b 181.sup.b 2.0.sup.b 16.4.sup.b 10.4.sup.b 12.9.sup.b 23.3.sup.b glycol diacetate Esters of Carboxylic Acids Decyl y 0.869.sup.b 212.sup.b 0.6.sup.b 14.9.sup.b 5.7.sup.b 3.1.sup.b 16.4.sup.b acetates** Tridecyl y 0.875.sup.b 261.sup.b 0.1.sup.b 15.1.sup.b 5.1.sup.b 1.6.sup.b 16.1.sup.b acetates*** Soy methyl y 0.87.sup.c@ 425.sup.c <0.5.sup.c 16.1.sup.c 4.9.sup.c 5.9.sup.c 17.8 esters* (25.degree. C./25.degree. C.) Fatty Alcohols 2-ethyl- y 0.829.sup.b 171.sup.b 2.0.sup.b 15.9.sup.b 3.3.sup.b 11.9.sup.b 20.2.sup.b hexanol Aprotic Solvents Dimethylsulfoxide y 1.097.sup.b 203.sup.b 2.6.sup.b 18.4.sup.b 16.4.sup.b 10.2.sup.b 26.6.sup.b Dimethyl y .94.sup.b 136.sup.b 20.sup.b 17.4.sup.b 13.7.sup.b 11.2.sup.b 24.7.sup.b formamide Propylene y 1.185.sup.b 270.sup.b 0.5.sup.b 20.0.sup.b 18.0.sup.b 4.1.sup.b 27.3.sup.b carbonate Siloxanes Octamethyl y 0.96.sup.g@ 144.sup.g <1.sup.d 15.1.sup.d 0.8.sup.d 0.0.sup.d 15.1.sup.h cyclotetra (25.degree. C./25.degree. C.) siloxane/deca methyl cyclopentasiloxane++ Hydrofluoroethers 1-methoxy- y 1.52 none 900.sup.d 13.7.sup.d 6.1.sup.d 8.2.sup.d 17.1.sup.d nonafluorobutane Aliphatic Hydrocarbons Isoparaffins y 0.77 140.sup. <10 15.7.sup.d 0.0.sup.d 0.0.sup.d 17.1.sup.d (DF 2000) Dibasic Esters Dimethyl y 1.084.sup.b 225.sup.b <0.9.sup.b 17.0.sup.b 4.7.sup.b 9.8.sup.b 20.2.sup.b glutarate *.varies. Phenyl-.omega.-hydroxy-poly (oxy 1,2 ethanediyl): Akzo Nobel **Exxate 1000; Exxon ***Exxate 1300; Exxon + Soy Gold 1100; AG Environmental Products ++ SF 1204; General Electric Silicones .sup.aBarton A.F.M.; Handbook of Solubility Parameters and Other Cohesion Parameters, 2.sup.nd Edition; CRC Press, 1991 (ISBN 0-8493-0176-9) .sup.bWypych, George; Handbook of Solvents, 2001; ChemTec (ISBN 1-895198