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.
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


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.




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, α-terpene isomers, pine oil, α-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)


1/2


for dispersion, about 0.5-9.0 (MPa)


1/2


for polar, and about 0.0-10.5 (MPa)


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)


1/2


for dispersion, about 0.0-7.0 (MPa)


1/2


or polar, and about 0.0-5.0 (MPa)


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)


1/2


for dispersion, about 3.0-7.5 (MPa)


1/2


for polar, and about 8.0-17.0 (MPa)


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)


1/2


for dispersion, about 4.5-20.5 (MPa)


1/2


for polar, and about 15.0-30.0 (MPa)


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)


1/2


for dispersion, about 1.5-6.5 (MPa)


1/2


for polar, and about 5.0-10.0 (MPa)


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)


1/2


for dispersion, about 3.0-10.0 (MPa)


1/2


for polar, and about 8.0-16.0 (MPa)


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)


1/2


for dispersion, about 2.0-7.5 (MPa)


1/2


for polar, and about 1.5-6.5 (MPa)


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)


1/2


for dispersion, about 3.1-18.8 (MPa)


1/2


for polar, and about 8.4-22.3 (MPa)


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)


1/2


for dispersion, about 3.0-9.0 (MPa)


1/2


for polar, and about 9.0-16.5 (MPa)


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)


1/2


for dispersion, about 0.0-4.5 (MPa)


1/2


for polar, and about 0.0-4.5 (MPa)


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)


1/2


for dispersion, about 4.0-10.0 (MPa)


1/2


for polar, and about 1.5-9.0 (MPa)


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)


1/2


for dispersion, about 0.0-2.0 (MPa)


1/2


for polar, and about 0.0-2.0 (MPa)


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)


1/2


for dispersion, about 4.0-6.5 (MPa)


1/2


for polar, and about 4.0-11.0 (MPa)


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)


1/2


for dispersion, about 3.0-8.0 (MPa)


1/2


for polar, and about 3.0-11.0 (MPa)


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)


1/2


for dispersion, about 6.0-17.0 (MPa)


1/2


for polar, and about 4.0-13.0 (MPa)


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° C. and 830 psig/20° C.

















TABLE 1















Evaporation








Soluble





Rate




Hansen Solubility Parameters




















in




Specific




Flash




(n-butyl






Hydrogen








carbon




Gravity




Point




acetate =




Dispersion




Polar




Bonding




Total






Solvent




dioxide




(20° C./20° C.)




(° F.)




100)




(MPa)


1/2






(MPa)


1/2






(MPa)


1/2






(MPa)


1/2
























Terpenes














Pine Oil




y




.929


a






193


a






  0.5


a






13.9


a






8.0


a






10.2


a






19.0


a








d-limonene




y




.843


c






121


c






  0.5


c






16.6


c






0.6


c






0.0


c






16.6


c










(25° C./25° C.)






Halocarbons






1,1,2-trifluoro-




y




1.57


b






none


b






2100


b






14.7


b






1.6


b






0.0


b






14.7


b








trichioroethane






n-propyl




y




1.35




none









  5.8




16.0


h






6.5


h






4.7


h






17.9






bromide





(25° C./25° C.)






Perfluorohexane




y




1.67


f






none


f






1000


d






12.1


d






0.0


d






0.0


d






12.1






Glycol Ethers






Triethylene




y




0.92@




>200


d







 <1


d






13.3


a






3.1


a






8.4


a






16.0


a








glycol mono-





15.5° C.






oleyl ether






Ethylan HB4*




y




1.12




>200


d







 <0.5


d






17.4


d






9.2


d






13.0


d






23.6


d








Polyols






Hexylene




y




.921


b






201


b






  1.0


b






15.8


b






8.4


b






17.8


b






25.2






glycol






Ethers






Tetraethylene




y




1.005


b






285


b






 ˜<0.5


d






15.7


b






2.0


b






8.2


b






17.8


b








glycol






dimethyl ether






Esters of Glycol Ethers






Ethylene




y




1.124


b






181


b






  2.0


b






16.4


b






10.4


b






12.9


b






23.3


b








glycol






diacetate






Esters of Carboxylic Acids






Decyl




y




0.869


b






212


b






  0.6


b






14.9


b






5.7


b






3.1


b






16.4


b








acetates**






Tridecyl




y




0.875


b






261


b






  0.1


b






15.1


b






5.1


b






1.6


b






16.1


b








acetates***






Soy methyl




y




0.87


c


@




425


c






 <0.5


c






16.1


c






4.9


c






5.9


c






17.8






esters*





(25° C./25° C.)






Fatty Alcohols






2-ethyl-




y




0.829


b






171


b






  2.0


b






15.9


b






3.3


b






11.9


b






20.2


b








hexanol






Aprotic Solvents






Dimethylsulf-




y




1.097


b






203


b






  2.6


b






18.4


b






16.4


b






10.2


b






26.6


b








oxide






Dimethyl




y




.94


b






136


b






 20


b






17.4


b






13.7


b






11.2


b






24.7


b








formamide






Propylene




y




1.185


b






270


b






  0.5


b






20.0


b






18.0


b






4.1


b






27.3


b








carbonate






Siloxanes






Octamethyl




y




0.96


g


@




144


g






 <1


d






15.1


d






0.8


d






0.0


d






15.1


h








cyclotetra





(25° C./25° C.)






siloxane/deca-






methyl






cyclopenta-






siloxane+ +






Hydrofluoroethers






1-methoxy-




y




1.52




none









 900


d






13.7


d






6.1


d






8.2


d






17.1


d








nonafluoro-






butane






Aliphatic Hydrocarbons






Isoparaffins




y




0.77




140









 <10




15.7


d






0.0


d






0.0


d






17.1


d








(DF 2000)






Dibasic Esters






Dimethyl




y




1.084


b






225


b






 <0.9


b






17.0


b






4.7


b






9.8


b






20.2


b








glutarate











*∝Phenyl-ω-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












a


Barton A.F.M.; Handbook of Solubility Parameters and Other Cohesion Parameters, 2


nd


Edition; CRC Press, 1991 (ISBN 0-8493-0176-9)












b


Wypych, George; Handbook of Solvents, 2001; ChemTec (ISBN 1-895198-24-0)












c


AG Environmental Products, website.












d


Estimated.












e


Clean Tech Proceedings 1998, pg 92












f


Fluorochem USA












g


GE Silicones Fluids Handbook, Bulletin No. 59 (9/91).












h


Fedors Method: R.F. Fedoers, Polymer Engineering and Science, 1974.













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.




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.




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.




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


.




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


110


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.




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


.




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.




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.




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 to remove pressurized fluid solvent from the textiles.




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.




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.




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.




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.




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.




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.




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


.




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


or other additives to impart other desirable attributes to the articles being treated. 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


.




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.




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.




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.




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.




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.




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.




As discussed above, 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, cyclic methyl siloxanes, hydrofluoroethers, dibasic esters, and aliphatic hydrocarbons solvents or similar solvents or mixtures of such solvents are organic solvents that can be used 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.




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.




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.




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° C. and 25° C. 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 in the same manner but test swatches were treated for 20 minutes. During this time the liquid carbon dioxide was stirred using an agitator mounted on the inside cover of the Parr bomb. 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.




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 soil removal capabilities. 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.














TABLE 2













Delta Whiteness Values















Cleaning




Insoluble




Insoluble







Time




Soil




Soil






Solvent




(min.)




Removal




Redeposition

















Liquid carbon dioxide (neat)




20




3.36




−1.23






Pine oil




12




8.49




−6.84






d-limonene




12




10.6




−9.2






1,1-2 trichlorotrifluoroethane




12




11.7




−14.46






N-propyl bromide




12




11.18




−9.45






Perfluorohexane




12




2.09




−3.42






triethylene glycol mono-oleyl




12




10.54*




−1.86*






ether (Volpo 3)






α-phenyl-ω-hydroxy-poly




12




1.54**




−13.6**






(oxy-1,2-ethanediyl)






Hexylene glycol




12




6.9




−1.4






Tetraethylene glycol dimethyl




12




10.08




−4.94






ether






Ethylene glycol diacetate




12




6.29




−3.39






Decyl acetates (Exxate 1000)




12




11.69




−8.6






Tridecyl acetates (Exxate




12




11.24




−4.86






1300)






Soy methyl esters (SoyGold




12




5.81




−7.71






1100)






2-ethylhexanol




12




12.6




−3.4






Propylene carbonate




12




2.99




−1.82






Dimethylsulfoxide




12




5.84




−0.22






Dimethylformamide




12




7.24




−10.09






Isoparaffins (DF-2000)




12




11.23




−5.95






Dimethyl glutarate




12




9.04




−1.23











*After two extraction cycles










**After three extraction cycles.













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° C. to 20° 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.















TABLE 3














Percentage by







Weight of Solvent on




Weight of







Test Swatch (grams)




Solvent















Before




After




Removed from






Solvent




Extraction




Extraction




Swatch

















Pine oil




7.8




0.1835




97.66%






d-Limonene




5.8




0.0014




99.98%






1,1,2-Trichlorotrifluoroethane




1.4




0.0005




99.96%






n-Propyl bromide




2.8




<0.447




>84%






Perfluorohexane




1.0




0.0006




99.94%






Triethylene glycol monooleyl




0.8




0.1824




77.88%






ether (7)






α-phenyl-ω-hydroxy-poly




16.0




5.7




64.5%






(oxy 1,2-ethanediyl);






(Ethylan HB4)






Hexylene glycol




4.9




0.3481




92.87%






Tetraethylene glycol dimethyl




5.2




.1310




97.48%






ether






Ethylene glycol diacetate




5.3




0.0418




99.21%






Decyl acetate (2)




2.4




0.0015




99.94%






Tridecyl acetate (1)




4.8




0.0605




98.75%






Soy methyl esters (8)




4.9




0.0720




98.54%






2-Ethylhexanol




0.5




0.0599




99.09%






Propylene carbonate




6.6




0.0599




99.09%






Dimethyl sulfoxide




3.3




0.5643




82.69%






Dimethylformamide




3.0




0.0635




97.88%






Octamethylcyclooctasiloxane/




5.5




0.0017




99.97%






Decamethylcyclopenta-






siloxane (4)






1-Methoxynonofluorobutane (6)




0.7




not




˜100%








detected






Isoparaffins (5)




4.3




0.0019




99.96%






Dimethyl glutarate (3)‡




5.8




0.0090




99.85%











Notes on Table 3: (1) Exxate 1300 (Exxon); (2) Exxate 1000 (Exxon); (3) DBE-5 (DuPont); (4) SF1204 (General Electric Silicones); (5) DF-2000 (Exxon); (6) HFE-7100 (3M); (7) Volpo 3 (Croda); (8) Soy Gold 1100 (AG Environmental Products)













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.



Claims
  • 1. A process for cleaning substrates comprising:placing the substrates to be cleaned in a vessel wherein the vessel is not pressurized; adding at least one organic solvent to the vessel; cleaning the substrates for a time sufficient to clean the substrates with the organic solvent in the absence of liquid carbon dioxide; removing a portion of the organic solvent from the vessel; adding at least one pressurized fluid solvent to the vessel; removing the pressurized fluid solvent from the vessel; and removing the substrates from the vessel; wherein, when the pressurized fluid solvent is liquid carbon dioxide, the liquid carbon dioxide is at a subcritical condition.
  • 2. The process of claim 1 wherein the organic solvent comprises a cyclic terpene.
  • 3. The process of claim 2 wherein the cyclic terpene: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)1/2 and 17.5 (MPa)1/2; has a polar Hansen solubility parameter of between 0.5 (MPa)1/2 and 9.0 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 0.0 (MPa)1/2 and 10.5 (MPa)1/2.
  • 4. The process of claim 3 wherein the cyclic terpene further:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 5. The process of claim 4 wherein the cyclic terpene is selected from a group including α-terpene isomers; pine oil; α-pinene isomers; d-limonene; and mixtures thereof.
  • 6. The process of claim 1 wherein the organic solvent comprises a halocarbon.
  • 7. The process of claim 6 wherein the halocarbon: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 1.100; has a dispersion Hansen solubility parameter of between 10.0 (MPa)1/2 and 17.0 (MPa)1/2; has a polar Hansen solubility parameter of between 0.0 (MPa)1/2 and 7.0 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 0.0 (MPa)1/2 and 5.0 (MPa)1/2.
  • 8. The process of claim 7 wherein the halocarbon further:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 9. The process of claim 8 wherein the halocarbon is selected from a group including chlorinated hydrocarbons; fluorinated hydrocarbons; brominated hydrocarbons; and mixtures thereof.
  • 10. The process of claim 1 wherein the organic solvent comprises a glycol ether.
  • 11. The process of claim 10 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)1/2 and 19.5 (MPa)1/2; has a polar Hansen solubility parameter of between 3.0 (MPa)1/2 and 7.5 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 8.0 (MPa)1/2 and 17.0 (MPa)1/2.
  • 12. The process of claim 11 wherein the glycol ether further:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 13. The process of claim 12 wherein the glycol ether is selected from a group including monoethylene glycol ether; diethylene glycol ether; triethylene glycol ether; monopropylene glycol ether; dipropylene glycol ether; tripropylene glycol ether; and mixtures thereof.
  • 14. The process of claim 1 wherein the organic solvent comprises a polyol.
  • 15. The process of claim 14 wherein the polyol: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 0.920; has a dispersion Hansen solubility parameter of between 14.0 (MPa)1/2 and 18.2 (MPa)1/2; has a poiar Hansen solubility parameter of between 4.5 (MPa)1/2 and 20.5 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 15.0 (MPa)1/2 and 30.0 (MPa)1/2.
  • 16. The process of claim 15 wherein the polyol further:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 17. The process of claim 16 wherein the polyol contains two or more hydroxyl radicals.
  • 18. The process of claim 1 wherein the organic solvent comprises an ether.
  • 19. The process of claim 18 wherein the 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 14.5 (MPa)1/2 and 20.0 (MPa)1/2; has a polar Hansen solubility parameter of between 1.5 (MPa)1/2 and 6.5 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 5.0 (MPa)1/2 and 10.0 (MPa)1/2.
  • 20. The process of claim 19 wherein the ether further:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 21. The process of claim 20 wherein the ether contains no free hydroxyl radicals.
  • 22. The process of claim 1 wherein the organic solvent comprises an ester of glycol ethers.
  • 23. The process of claim 22 wherein the ester of glycol ethers: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 15.0 (MPa)1/2 and 20.0 (MPa)1/2; has a polar Hansen solubility parameter of between 3.0 (MPa)1/2 and 10.0 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 8.0 (MPa)1/2 and 16.0 (MPa)1/2.
  • 24. The process of claim 23 wherein the ester of glycol ethers further:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 25. The process of claim 1 wherein the organic solvent comprises an ester of monobasic carboxylic acids.
  • 26. The process of claim 25 wherein the ester of monobasic carboxylic acids: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)1/2 and 17.0 (MPa)1/2; has a polar Hansen solubility parameter of between 2.0 (MPa)1/2 and 7.5 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 1.5 (MPa)1/2 and 6.5 (MPa)1/2.
  • 27. The process of claim 26 wherein the ester of monobasic carboxylic acids further:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 28. The process of claim 1 wherein the organic solvent comprises a fatty alcohol.
  • 29. The process of claim 28 wherein the fatty alcohol: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 13.3 (MPa)1/2 and 18.4 (MPa)1/2; has a polar Hansen solubility parameter of between 3.1 (MPa)1/2 and 18.8 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 8.4 (MPa)1/2 and 22.3 (MPa)1/2.
  • 30. The process of claim 29 wherein the fatty alcohol further:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 31. The process of claim 30 wherein, in the fatty alcohol, the carbon chain adjacent to the hydroxyl group contains at least five carbon atoms.
  • 32. The process of claim 1 wherein the organic solvent comprises a short chain alcohol.
  • 33. The process of claim 32 wherein the short chain alcohol: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 13.5 (MPa)1/2 and 18.0 (MPa)1/2; has a polar Hansen solubility parameter of between 3.0 (MPa)1/2 and 9.0 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 9.0 (MPa)1/2 and 16.5 (MPa)1/2.
  • 34. The process of claim 33 wherein the short chain alcohol further:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 35. The process of claim 34 wherein, in the short chain alcohol, the carbon chain adjacent to the hydroxyl group contains no more than four carbon atoms.
  • 36. The process of claim 1 wherein the organic solvent comprises a siloxane.
  • 37. The process of claim 36 wherein the siloxane: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 0.900; has a dispersion Hansen solubility parameter of between 14.0 (MPa)1/2 and 18.0 (MPa)1/2; has a polar Hansen solubility parameter of between 0.0 (MPa)1/2 and 4.5 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 0.0 (MPa)1/2 and 4.5 (MPa)1/2.
  • 38. The process of claim 37 wherein the siloxane:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 39. The process of claim 1 wherein the organic solvent comprises a hydrofluoroether.
  • 40. The process of claim 39 wherein the hydrofluoroether: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 1.500 has a dispersion Hansen solubility parameter of between 12.0 (MPa)1/2 and 18.0 (MPa)1/2; has a polar Hansen solubility parameter of between 4.0 (MPa)1/2 and 10.0 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 1.5 (MPa)1/2 and 9.0 (MPa)1/2.
  • 41. The process of claim 40 wherein the hydrofluoroether:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 42. The process of claim 1 wherein the organic solvent comprises an aliphatic hydrocarbon.
  • 43. The process of claim 42 wherein the aliphatic hydrocarbon: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 0.700; has a dispersion Hansen solubility parameter of between 14.0 (MPa)1/2 and 17.0 (MPa)1/2; has a polar Hansen solubility parameter of between 0.0 (MPa)1/2 and 2.0 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 0.0 (MPa)1/2 and 2.0 (MPa)1/2.
  • 44. The process of claim 43 wherein the aliphatic hydrocarbon:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 45. The process of claim 1 wherein the organic solvent comprises an ester of dibasic carboxylic acids.
  • 46. The process of claim 45 wherein the ester of dibasic carboxylic acids: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 0.900; has a dispersion Hansen solubility parameter of between 13.5 (MPa)1/2 and 18.0 (MPa)1/2; has a polar Hansen solubility parameter of between 4.0 (MPa)1/2 and 6.5 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 4.0 (MPa)1/2 and 11.0 (MPa)1/2.
  • 47. The process of claim 46 wherein the ester of dibasic carboxylic acids:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 48. The process of claim 1 wherein the organic solvent comprises a ketone.
  • 49. The process of claim 48 wherein the ketone: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)1/2 and 19.0 (MPa)1/2; has a polar Hansen solubility parameter of between 3.0 (MPa)1/2 and 8.0 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 3.0 (MPa)1/2 and 11.0 (MPa)1/2.
  • 50. The process of claim 49 wherein the ketone:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 51. The process of claim 1 wherein the organic solvent comprises an aprotic solvent that contains no dissociable hydrogens.
  • 52. The process of claim 51 wherein the aprotic solvent: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 0.900; has a dispersion Hansen solubility parameter of between 15.0 (MPa)1/2 and 21.0 (MPa)1/2; has a polar Hansen solubility parameter of between 6.0 (MPa)1/2 and 17.0 (MPa)1/2; and has a hydrogen bonding Hansen solubility parameter of between 4.0 (MPa)1/2 and 13.0 (MPa)1/2.
  • 53. The process of claim 52 wherein the aprotic solvent:has an evaporation rate of lower than 50 (based on n-butyl acetate=100); and has a flash point greater than 100 degrees Fahrenheit.
  • 54. The process of claim 1 wherein the pressurized fluid solvent is densified carbon dioxide.
RELATED APPLICATION

This application is a continuation-in-part of U.S. patent application Ser. No. 09/419,345, filed Oct. 15, 1999, which issued into U.S. Pat. No. 6,355,072 on March 12, 2002, the disclosure of which is incorporated by reference herein in its entirety.

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Continuation in Parts (1)
Number Date Country
Parent 09/419345 Oct 1999 US
Child 09/837849 US