Bleaching and dyeing; fluid treatment and chemical modification – Cleaning or laundering – Dry cleaning
Reexamination Certificate
1999-10-15
2002-03-12
Gupta, Yogendra N. (Department: 1751)
Bleaching and dyeing; fluid treatment and chemical modification
Cleaning or laundering
Dry cleaning
C008S137000
Reexamination Certificate
active
06355072
ABSTRACT:
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. 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 utilize 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 discloses a process for cleaning precision parts utilizing a liquefied pressurized gas in the supercritical state and an environmentally acceptable co-solvent. During this process, the parts to be cleaned are pre-treated with the co-solvent and then placed in the cleaning vessel. Afterwards, the contaminants and co-solvent are removed from the parts by circulating a pressurized gas in its supercritical state through the vessel. Redeposition of co-solvent and contaminants is controlled by the amount of pressurized gas that is pumped through the vessel. Co-solvents specified for use in conjunction with the cleaning solvent include aliphatics, terpenes, acetone, laminines, isopropyl alcohol, Axarel (DuPont), Petroferm (Petroferm, Inc.), kerosene, and Isopar-m (Exxon). During the cleaning process, the cleaning solvent (supercritical carbon dioxide) flows through a vessel containing the parts to be treated, through a filter or filters and directly to a separator in which the solvent is evaporated and recondensed. The disclosed co-solvents for use in this patent have high evaporation rates and low flash points. The use of such co-solvents results in high solvent losses, and high fire risks. Furthermore, many of the co-solvents are not compatible with common dyes and fibers used in textile manufacture. Also, the use of supercritical carbon dioxide necessitates the use of more expensive equipment.
Damaso Gene R.
Racette Timothy L.
Schulte James E.
Gupta Yogendra N.
Mayer Brown & Platt
R.R. Street & Co. Inc.
Webb Gregory E.
LandOfFree
Cleaning system utilizing an organic cleaning solvent and a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cleaning system utilizing an organic cleaning solvent and a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cleaning system utilizing an organic cleaning solvent and a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2870393