Bleaching and dyeing; fluid treatment and chemical modification – Cleaning or laundering – Dry cleaning
Reexamination Certificate
1998-08-28
2001-08-07
Liott, Caroline D. (Department: 1751)
Bleaching and dyeing; fluid treatment and chemical modification
Cleaning or laundering
Dry cleaning
Reexamination Certificate
active
06270531
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to carbon dioxide-based formulations that contain surfactants, and methods of using the same. The compositions and methods are useful for a variety of applications, including the cleaning of garments and fabrics.
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.
PCT Application WO 97/16264 by The University of North Carolina at Chapel Hill describes cleaning systems that employ liquid or supercritical carbon dioxide in combination with a surfactant that contains a “CO
2
-philic” group. The term “CO
2
-philic” was first coined in conjunction with such surfactants by J. DeSimone and colleagues. See, e.g., J. DeSimone et al.,
Science
265, 356-359 Jul. 15, 1994).
PCT Application WO96/27704 (Sep. 12, 1996) by Unilever, describes dry cleaning systems using densified carbon dioxide and special surfactant adjuncts. The surfactants employed have a CO
2
-philic moiety connected to a CO
2
-phobic moiety. See also U.S. Pat. No. 5,683,473 to Jureller et al; U.S. Pat. No. 5,683,977 to Jureller et al.; U.S. Pat. No. 5,676,705 to Jureller et al.
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. Indeed, since some water must be present in dry-cleaning, such use is contrary to this system.
In view of the foregoing, there is a continuing need for effective carbon dioxide-based cleaning systems.
SUMMARY OF THE INVENTION
A method for 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, optionally water, and an end-functional polysiloxane surfactant. In one embodiment an organic co-solvent is also included. 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.
End-functional polylsiloxanes used in carrying out the present invention are represented by the formula X
1
—A—X
2
, wherein X
1
and X
2
are the end-functional groups or moities (e.g. as described below) and A is a siloxane group such as polydimethylsiloxane.
As discussed below, the end-functional polysiloxane may be provided in liquid CO
2
as a mixture, the mixture useful as an intermediate for preparing the dry cleaning compositions noted above, or useful in other applications where a surfactant in carbon dioxide is desired (including, but not limited to, electronic cleaning operations such as silicon wafer cleaning, cleaning mechanical parts sucy as gyroscopes, dry cleaning of fabrics, as wetting agents for CO
2
based systems, and as dispersing additives for compounds including organic and inorganic compounds dispersed in CO
2
, as described in U.S. Pat. No. 5,789,505).
Also disclosed is an improved a process which involves contacting liquid or supercritical CO
2
with a mobile CO
2
-phobic substance. The improvement comprises lowering the surface tension between said CO
2
and CO
2
-phobic substance by adding to the CO
2
an end-functional polysiloxane surfactant.
A further aspect of the present invention is a composition comprising: (a) liquid or supercritical carbon dioxide; and (b) from 0.001 to 30 percent surfactant, wherein said surfactant is an end-functional polysiloxane surfactant having the formula X
1
—A—X
2
, wherein X
1
and X
2
are CO
2
-phobic groups, and A is a polysiloxane group.
A further aspect of the invention is a composition comprising: (a) liquid or supercritical carbon dioxide; (b) from 0.001 to 30 percent surfactant, wherein said surfactant is an end-functional polysiloxane surfactant; and (c) from 0.01 to 50 percent of a CO
2
-phobic compound, which CO
2
-phobic compound is non-covalently associated with said surfactant.
DETAILED DESCRIPTION OF THE INVENTION
The terms alkyl or loweralkyl as used herein means C1 to C4 linear or branched, saturated or unsaturated alkyl, including methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, and tert-butyl.
The term “halo” as used herein means halogen, including fluoro, chloro, bromo, and iodo. Fluoro is preferred.
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 particulate 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.
“End Functional” Polysiloxane (PSI) materials have specific utility as surfactants in the formulation of CO
2
based cleaning systems. Detergency in non-aqueous cleaning systems is facilitated by surfactants that increase the quantity and stability of entrained water in the system. End Functional PSI materials are differentiated from other functional PSI materials by the locale and orientation of the functional group (e.g., hydrophilic or lipophilic functional groups; preferably hydrophilic functional groups) being at either (or both) termini of the molecules. The term “termini” or “terminus” herein refers to the discontinuation or end of dimethyl siloxane repeat units in the molecule. Thus the functional group is typically covalently joined to a dimethyl silyl group, rather than emanating from a methyl siloxane linkage in the backbone of the polymer.
As noted above, end-functional polysiloxane surfactants used in carrying out the present invention are represented by the formula X
1
—A—X
2
, wherein X
1
and X
2
are the end-functional groups or moities (e.g. as described below) and A is polysiloxane group such as polydimethylsiloxane, typically having a molecular weight of 100 or 200 to 100,000, 200,000 or 400,000 g/mole. Such compounds are more particularly represented by the formula:
wherein:
n is from 1 or 2 to 20, 100, 500, 1,000, 5,000, or 10,000. Preferably, n is 1 or 2 to 20, 50 or 100.
At least one, and preferably both, of X
1
and X
2
are CO
2
-phobic groups, such as lipophilic or hydrophilic (e.g., anionic, cationic) groups, but are not CO
2
-philic groups. The X
1
and X
2
groups may be the same or different. Optionally, but less preferably, one of X
1
or X
2
may be a CO
2
-philic group, such as an alkyl or aryl group as the polysiloxane end terminus.
R is alkyl, aryl, or haloalkyl such as perfluoroalkyl. Lower alkyl, particularly methyl, is preferred, trifluoropropyl is preferred, and phenyl is preferred. Methyl is most preferred.
In general, the materials of the invention contain multiple siloxane repeat units that are “CO
2
-philic”, and CO
2
-phobic end-functional groups capable of forming non-covalent assoc
DeYoung James P.
Stewart Gina M.
Storey-Laubach Bernadette
Liott Caroline D.
MiCell Technologies, Inc.
Myers Bigel Sibley & Sajovec P.A.
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