Dry cleaning methods and compositions

Details Dry cleaning methods and compositions Dry cleaning methods and compositions

2001-01-22

2001-07-10

Diamond, Alan (Department: 1753)

Cleaning compositions for solid surfaces, auxiliary compositions

Cleaning compositions or processes of preparing

For cleaning a specific substrate or removing a specific...

C510S285000, C510S289000, C510S290000, C510S407000, C008S142000

Reexamination Certificate

active

06258766

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to methods and compositions for carrying out the dry-cleaning of fabrics (e.g., garments) in liquid carbon dioxide.
BACKGROUND OF THE INVENTION
Commercial dry cleaning systems currently employ potentially toxic and environmentally harmful halocarbon solvents, such as perchloroethylene. Carbon dioxide has been proposed as an alternative to such systems in U.S. Pat. No. 4,012,194 to Maffei. A problem with carbon dioxide is, however, its lower solvent power relative to ordinary solvents.
German Patent Application DE3904514 A1, published Aug. 23, 1990, describes a cleaning system combining various conventional anionic or nonionic surface active agents with supercritical CO
2
. The system described therein appears to combine the detergency mechanism of conventional surface active agents with the solvent power of supercritical fluid carbon dioxide. A carbon dioxide dry cleaning system effective for liquid carbon dioxide is not provided.
U.S. Pat. No. 5,683,473 to Jureller et al. (see also U.S. Pat. No. 5,683,977 to Jureller et al.) describes a dry cleaning system utilizing carbon dioxide in liquid form in combination with surfactants that contain a functional moiety that is CO
2
-philic, which surfactants are not conventionally used for detergent cleaning. Since there are numerous advantages to employing conventional surfactants (e.g., cost, ready availability, established regulatory approval, established toxicology, etc), it would be extremely desireable to have a dry cleaning system for liquid carbon dioxide that employs conventional surfactants that do not contain a CO
2
-philic group.
U.S. Pat. No. 5,377,705 to Smith et al. describes a precision cleaning, system in which a work piece is cleaned with a mixture of CO
2
and a co-solvent. Smith provides an entirely non-aqueous system, stating: “The system is also designed to replace aqueous or semi-aqueous based cleaning processes to eliminate the problems of moisture damage to parts and water disposal” (col. 4 line 68 to col. 5 line 3). Co-solvents that are listed include acetone and ISOPAR™ M (col. 8, lines 19-24). Use in dry cleaning is neither suggested nor disclosed.
In view of the foregoing, there is a continuing need for effective carbon dioxide-based dry cleaning systems.
SUMMARY OF THE INVENTION
A method for dry-cleaning articles such as fabrics and clothing in carbon dioxide comprises contacting an article to be cleaned with a liquid dry cleaning composition for a time sufficient to clean the fabric. The liquid dry-cleaning composition comprises a mixture of carbon dioxide, a surfactant, and an organic co-solvent. After the contacting step, the article is separated from the liquid dry cleaning composition.
Preferably, the liquid dry cleaning composition is at ambient temperature, of about 0° C. to 30° C. The surfactant is soluble in the co-solvent. The surfactant may or may not be soluble in the CO
2
. Hence, in one embodiment; the surfactant may contain a CO
2
-philic group. However, in the preferred embodiment, the surfactant does not contain a CO
2
-philic group. Hence, an advantage of the present invention is that, by proper use of the co-solvent, conventional surfactants may be employed in a liquid carbon dioxide dry cleaning system.
DETAILED DESCRIPTION OF THE INVENTION
The term “clean” as used herein refers to any removal of soil, dirt, grime, or other unwanted material, whether partial or complete. The invention may be used to clean nonpolar stains (i.e., those which are at least partially made by nonpolar organic compounds such as oily soils, sebum and the like), polar stains (i.e., hydrophilic stains such as grape juice, coffee and tea stains), compound hydrophobic stains (i.e., stains from materials such as lipstick and candle wax), and particulare soils (i.e., soils containing insoluble solid components such as silicates, carbon black, etc.).
Articles that can be cleaned by the method of the present invention are, in general, garments and fabrics (including woven and non-woven) formed from materials such as cotton, wool, silk, leather, rayon, polyester, acetate, fiberglass, furs, etc., formed into items such as clothing, work gloves, rags, leather goods (e.g., handbags and brief cases), etc.
Liquid dry-cleaning compositions useful for carrying out the present invention typically include water. The source of the water is not critical in all applications. The water may be added to the liquid solution before the articles to be cleaned are deposited therein, may be atmospheric water, may be the water carried by the garments, etc.
In one embodiment of the invention, better particulate cleaning may be obtained in the absence of water added to the dry-cleaning composition. There is inherently water present on or in the garments or articles to be cleaned as they are placed in the cleaning vessel. This water serves in part to adhere particulate soil to the articles to be cleaned. As the water is removed from the garments into the cleaning composition during the cleaning process, the removal of water from the article to be cleaned facilitates the removal of particulates from the articles to be cleaned. Thus, decreasing the amount of water originally in the cleaning system can serve to facilitate the cleaning of particulate soil from the articles to be cleaned by the action of the water inherently carried by the article to be cleaned.
Liquid dry-cleaning compositions useful for carrying out the present invention typically comprise:
(a) from zero (0), 0.02, 0.05 or 0.1 to 5 or 10 percent (more preferably from 0.1 to 4 percent) water;
(b) carbon dioxide (to balance; typically at least 30 percent);
(c) surfactant (preferably from 0.1 or 0.5 percent to 5 or 10 percent total, which may be comprised of one or more different surfactants); and
(d) from 0.01 or 0.1 to 50 percent (more preferably 1, 2 or 4 percent to 30 percent) of an organic co-solvent.
Percentages herein are expressed as percentages by weight unless otherwise indicated.
The composition is provided in liquid form at ambient, or room, temperature, which will generally be between zero and 50° Centigrade. The composition is held at a pressure that maintains it in liquid form within the specified temperature range. The cleaning step is preferably carried out with the composition at ambient temperature.
The organic co-solvent is, in general, a hydrocarbon co-solvent. Typically the co-solvent is an alkane co-solvent, with C
10
to C
20
linear, branched, and cyclic alkanes, and mixtures thereof (preferably saturated) currently preferred. The organic co-solvent preferably has a flash point above 140° F., and more preferably has a flash point above 170° F. The organic co-solvent may be a mixture of compounds, such as mixtures of alkanes as given above, or mixtures of one or more alkanes. Additional compounds such as one or more alcohols (e.g., from 0 or 0.1 to 5% of a C1 to C15 alcohol (including diols, triols, etc.)) different from the organic co-solvent may be included with the organic co-solvent.
Examples of suitable co-solvents include, but are not limited to, aliphatic and aromatic hydrocarbons, and esters and ethers thereof, particularly mono and di-esters and ethers (e.g., EXXON ISOPAR L, ISOPAR M, ISOPAR V, EXXON EXXSOL, EXXON DF 2000, CONDEA VISTA LPA-170N, CONDEA VISTA LPA-210, cyclohexanone, and dimethyl succinate), alkyl and dialkyl carbonates (e.g., dimethyl carbonate, dibutyl carbonate, di-t-butyl dicarbonate, ethylene carbonate, and propylene carbonate), alkylene and polyalkylene glycols, and ethers and esters thereof (e.g., ethylene glycol-n-butyl ether, diethylene glycol-n-butyl ethers, propylene glycol methyl ether, dipropylene glycol methyl ether, tripropylene glycol methyl ether, and dipropylene glycol methyl ether acetate), lactones (e.g., (gamma)butyrolactone, (epsilon)caprolactone, and (delta) dodecanolactone), alcohols and diols (e.g., 2-propanol, 2-methyl-2-propanol, 2-methoxy-2-propanol, 1-octanol, 2-ethyl hexanol, cyclopentanol, 1,3-propanediol, 2,3-butanediol, 2-methyl-2,4-pentanediol) and

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