US3689211A

US3689211A - Dry cleaning method

Info

Publication number: US3689211A
Application number: US16759A
Authority: US
Inventors: John J Giampalmi Jr; Istvan K Telegdy; Manfred Wirth
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1969-04-24
Filing date: 1970-03-05
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05
Also published as: GB1307318A; FR2039440B1; NL7005922A; BE749533A; DE2019418A1; FR2039440A1

Abstract

AN IMPROVED METHOD FOR DRY CLEANING FABRICS, E.G., COTTON, COTTON-SYNTHETIC BLENDS, RAYON, NYLON, WOOL, WORSTED, ETC, WHCIH COMPRISES A THREE-STEP PROCESS: (A) CONTACTING THE FABRIC WITH A DRY CLEANING SOLVENT CONTAINING FROM 0.005 TO 25 VOLUME PERCENT OF H2O AND 0.01 TO 5 VOLUME PERCENT OF A DETERGENT FOR FROM ONE TO 20 MINUTES; AND THEN, IN ANY ORDER, (B) CONTACTING THE FABRIC WITH A DRY CLEANING SOLVENT CONTAINING 0.01 TO 15 VOLUME PERCENT OF A DETERGENT FOR FROM ONE TO 20 MINUTES; AND (C) CONTACTING THE FABRIC WITH A DRY CLEANING SOLVENT CONTAINING 0.01 TO 5 VOLUME PERCENT OF A DETERGENT FOR FROM ONE TO 20 MINUTES.

Description

P 5, 1972 J. J. GIAMPALMI, JR, ET AL 3,689,211

DRY CLEANING METHOD Filed March 5, 1970 3 Sheets-Sheet 1 Tan k Tank H ZZZ l'l/a/er separa/or L r k Tank Tank Fi/fer I 12 l T 2 Was/7 whee/ Y L W0 7 6/ Je oara/or 5/i// STEP 3 f Tank Tank T 017% W066 whee INVENTORS.

HTTORNEY P 5, 1972 J. J. GIAMPALMI, JR., ET AL 3,689,211

DRY CLEANING METHOD Filed March 5, 1970 3 Sheets-Sheet 5 STEP! Tank Tank Tank STEP 2 7 Tank Tank Tank 1 it I PE-L Tank Tan/v Tank I ll ZZZ r Wash "1 wheel H 0 2 Wa/r se oara/or 0 IMVENTORS 69 7 John J.Giumpalm| Jr /J/uan K Te/e dg Man/R90 W/r 5y az cmui HTTORNEY Ser. No. 16,759

Int. Cl. D061 N US. Cl. 8-142 13 Claims ABSTRACT OF THE DISCLOSURE An improved method for dry cleaning fabrics, e.g., cotton, cotton-synthetic blends, rayon, nylon, wool, worsted, etc., which comprises a three-step process:

(a) contacting the fabric with a dry cleaning solvent containing from 0.005 to 25 volume percent of H 0 and 0.01 to volume percent of a detergent for from one to 20 minutes; and then, in any order,

(b) contacting the fabric with a dry cleaning solvent containing 0.01 to 15 volume percent of a detergent for from one to minutes; and

(c) contacting the fabric with a dry cleaning solvent containing 0.01 to 5 volume percent of a detergent for from one to 20 minutes.

This application is a continuation-in-part of my copending application, Ser. No. 818,892, filed Apr. 24, 1969, now abandoned.

SUMMARY OF THE INVENTION In accordance with the method of the instant invention, those fabrics typically dry cleaned, e.g., cottons, cotton-synthetic blends, rayon, polyesters, nylon, wool, worsted, Fiberglas, leather, fur, etc., may now be cleaned more effectively with a minimum of ordinary soil deposition.

The invention provides a system for effective simultaneous or separate dry cleaning of cotton, synthetic and cotton-synthetic blend fabrics by substantially eliminating the preferential soil redeposition which the art has experienced when attempting to dry clean these fabrics togther, said preferential soil redeposition resulting from the cleaning system as well as the surface chemistry and morphology of the fabrics.

Further, the invention provides a flexible system which may be tailored to the various soil levels, types of soil, odors, and the like, encountered by the industrial dry cleaner, and to the particular cleaning equipment utilized.

Yet further, the invention provides a flexible cleaning system which will prevent problems associated with excess water, such as filter plugging, detergent separation from the solvent, water spotting, and the like, by permitting the dry cleaner to select the optimum sequence of steps to deal with these problems.

The instant invention, then, comprises a three-step method for dry cleaning fabrics. In its simplest form, the method is as follows:

(A) Contacting a fabric with a bath consisting of a dry cleaning solvent, H 0 and a detergent for about one to 20 minutes, then removing the liquid from the wheel, preferably by draining and/or extraction; and then, in any order,

(B) Contacting the fabric with a bath consisting of a dry cleaning solvent and a detergent for about one to 20 minutes, then removing the liquid from the wheel, preferably by draining and/ or extraction; and

(C) Contacting the fabric with a bath consisting of a dry cleaning solvent and a detergent for about one to nited States Patent Ofice Patented Sept. 5, 1972 20 minutes, thereafter removing the liquid from the wheel, preferably by draining and/ or extraction.

It is to be noted that one may optionally utilize Water in (C), particularly when (C) is used as the second bath.

DETAILED DESCRIPTION OF THE INVENTION In more detail, one embodiment of the method may be carried on as follows:

Step 1.-Fabric is contacted, in the presence of water, with a dry cleaning solvent containing a nonionic and/or anionic detergent. The amount of water may suitably vary from about 0.005 to about 25 percent by volume in relation to the solvent bath employed, and may be in the form of liquid or steam, which may contact the fabric before, at the same time, i.e., be present in the solvent, or after the introduction of the cleaning solvent. If woolens are in the fabric load, the amount of water should not exceed the tolerance level of the fabric.

The cleaning solvent, preferably a chlorinated hydrocarbon solvent, suitably should contain between about 0.01 and 5 volume percent detergent in relation to the solvent, it being preferred to employ an anionic detergent, such as a phosphate ester or a petroleum sulfonate.

The fabric is then agitated in this water-solvent-detergent mixture environment for about 2 to about 12 minutes to effect cleaning. The liquid is then separated from the fabric, such as by first draining and then extracting.

The soiled solvent may then be separated from the contaminants by, for instance, filtration or distillation. The distillate or filtrate may be re-utilized, if desired, in the process.

The sequence of the next two steps may be selected from two alternatives (B-C) or (C-B), said selection to be based upon (1) the soil level and type of soil, (2) the cleaning equipment employed, (3) the nature of the fabric to be cleaned, (4) the amount of H 0 present in the system and on the garments and (5) odors present.

(B) The fabric is contacted with a dry cleaning solventdetergent mixture, and agitated therein for about 3 to about 15 minutes. The detergent, which may be the same or different from that compound or compounds employed in the previous step(s), is preferably an anionic and/or nonionic surfactant, and more preferably a phosphate ester plus a nonionic detergent, and should be present in about 0.01 to 15 volume percent in relation to the solvent, preferably a chlorinated hydrocarbon solvent. The liquid is then separated from the fabric, such as by draining and then extracting.

Once again, the soiled solvent may be separated from contaminants, such as by filtration or distillation. The distillate or filtrate may then be re-utilized as above.

(C) The fabric is contacted with a dry cleaning solventdetergent mixture, and agitated therein for about one to about 12 minutes. The detergent, which may be the same or different from that compound or compounds employed in the previous step(s), is preferably an anionic detergent, such as a phosphate ester or a petroleum sulfonate, and should be present in about 0.01 to 5 percent by volume in relation to the solvent, preferably a chlorinated hydrocarbon solvent. The liquid is then separated from the fabric, such as by draining and then extracting.

One may optionally utilize from 0.005 to 25% by volume to the solvent bath employed of water, particularly when (C) is the second bath.

The soiled solvent may be re-utilizecl in the process, after treatmentas above, if desired.

After the three-step treatment, regardless of the order chosen, the cleaned fabric may be given any further finishing treatment desired, and/ or dried. It is to be noted that solvent soluble or compatible finishing compositions may be placed in any of the three baths, if desired, preferably (C) in or added after the third bath extraction. Therefore, the process may serve not only the purpose of cleaning, but also may be utilized to finish the fabrics.

One preferred embodiment of the invention is illustrated in FIGS. 1 through 3. Each step is outlined below:

Step. 1.The dry cleaning solvent-phosphate ester detergent mixture is pumped or gravity fed into a container, such as a wash wheel or similar device. The fabric can be dampened with water or steam prior to contact with the cleaning solvent, or water can be added to the wash wheel at the same time, as or after, the introduction of the cleaning solvent to the wash wheel. One source of the solvent/ detergent mixture is Tank I, as illustrated in FIG. 1.

The fabric is then agitated in the wash wheel for 2 to 8 minutes, the liquid drained from the wheel and the residue extracted from the fabric. All, or a portion of, the solvent mixture so removed from the container may then be treated for H and soil removal, such as by distillation. The treated solvent is then preferably removed to Tank III for subsequent use in Step 3.

Step 2.The fabric is next contacted with a drycleaning solvent containing 0.25 to 15 volume percent of a dry cleaning detergent consisting of from to 90% by weight of at least one phosphate ester (as detailed below), and from 95 to by weight of a nonionie dry cleaning detergent (also detailed below), said mixture being pumped or gravity fed from Tank II into the wash wheel. The fabric is agitated for 3 to minutes, all, or a portion of, the used solvent mixture being continuously filtered, such as between Tank II and the wash wheel, or vice versa. FIG. 2 shows one such filtration arrangement, others being suitable.

At the end of the agitation period, the liquid is drained from the wheel and the residue extracted from the fabric. The liquid so removed is then stored in Tank II for subsequent re-use in Step 2.

According to the soil level of the fabric cleaned, a portion of the used solvent is distilled, such as at least about 1% by weight, and, after water separation, the distillate returned to the process. It is preferred to periodically distill at least about a 5% by weight portion of said solvent.

The solvent mixture which is depleted by fabric pickup, filtration or distillation is then replenished by the same mixture utilized to initially contact the fabric,- thereby eliminating the necessity to test-and-add. For further information see US. Pat. 3,482,928.

Step 3.--The fabric is finally contacted with a solventphosphate ester detergent mixture, pumped or gravity fed from Tank III, as illustrated in FIG. 3, into the container and the fabric agitated therein for one to 8 minutes. The liquid is then removed as above and preferably fed into Tank I for subsequent use in Step 1.

FIGS. 5 through 7 illustrate two alternative methods for carrying out the process of this invention, it being understood that other suitable alternatives are obvious to those skilled in the dry cleaning art.

Step 1.--The solvent mixture, as in FIG. 1 above, is contacted with the fabric in the wash wheel, removed and distilled, the only difference between FIGS. 1 and 5 being that the distillate is stored in Tank 11 rather than III, it being preferred, in this instance, to utilize the distillate in Step 2.

Step 2-The fabric is next contacted with a solventphosphate ester detergent mixture (as in FIG. 3 above), pumped or gravity fed from Tank II, as illustrated in FIG. 6, into the wash wheel and the fabric agitated therein as in FIG. 3.

The soiled solvent, depending upon soil concentration, may then be returned directly to Tank I (indicated by solid lines) for subsequent re-use in Step 1 (FIG. 5), or all, or a portion of, the soiled solvent may be distilled, the distillate preferably being stored in Tank I, again for subsequent re-use in Step 1.

Step 3.-The fabric is finally contacted with a solvent- 4 detergent mixture as illustrated by FIG. 7. It is to be noted that Step 3 (FIG. 7) and Step 2 (FIG. 2) are the same, excepting their sequence in the total operation.

If the cleaning conditions warrant, filtration may suitably be utilized for particulate removal either above or below the wash Wheel in FIGS. 1, 3, 5 and 6.

SUITABLE SOLVENTS The dry cleaning solvents which are suitable for the method of this invention include chlorinated hydrocarbons, such as carbon tetrachloride, methyl chloroform, ethylene dichloride, trichloroethylene and perchloroethylene; chlorofluorocarbons, such as trichlorofluoromethane, tetrachlorodifluoroethane, dichlorotetrafluoroethane, trichlorotrifiuoroethane and mixtures thereof; and hydrocarbon solvents, such as Stoddard solvent, naphtha and other petroleum solvents.

ANIONIC DETERGENTS Anionic detergents which are suitable include various salts of alkyl sulfonates, sulfated and sulfonated amines and amides, phosphate esters, alcohol sulfates, ethoxylated alcohol sulfates, sulfonates of alkyl naphthalenes, sulfated ethoxylated alkyl phenols, sulfated fatty esters, sulfated and sulfonated oils and fatty acids; dodecyl and tridecyl benzene sulfonates, petroleum sulfonates and taurates.

It is preferable when employing the monovalent salts, e.g., Na, Li, K and NH of alkyl sulfonates, sulfated and sulfonated amines and amides and alcohol sulfates, that the alkyl moieties contain at least 16 carbon atoms, and when employing the divalent salts, e.g., Ca, Mg and mono-, diand triethanolamine salts of-these same detergents, the alkyl moieties contain at least 10 to 12 carbon atoms.

Similarly, monovalent and divalent salts of ethoxylated alcohol sulfates are found suitable when the alcohol moiety contains at least about 18 carbon atoms, and there are about 2 to 6 ethylene oxide groups present in the molecule.

Monovalent and divalent salts of alkyl naphthalene sulfonates are suitable when the alkyl group contains at least about 12 carbon atoms.

The monovalent salts, e.g., Na, K, Li and NH of the sulfated ethoxylated alkyl phenols are suitable when the alkyl group contains at least about 9 carbon atoms, and there are between about 2 to 6 ethylene oxide groups presout. The divalent salts of these sulfonates, e.g., Ca and Mg, and the ethanolamine salts which have alkyl groups containing at least about 6 carbon atoms are also suitable.

The Na, K, NH Ca, Mg, Li and monodiand trieth-- anolamine salts of sulfated fatty esters are also suitable anionic detergents. Examples of sulfated fatty esters include sulfated oleic acid esters, such as glyceryl trioleate, propyl oleate, and amyl oleate, and sulfated ricinoleic esters.

Salts similar to the above of sulfated and sulfonated oils and fatty acids are also suitable. Examples of the oils include vegetable oils, such as tall oil and castor oil; and marine fatty acid oils, such as sperm oil and cod oil.

The Na, K, NH. Ca, Mg, Li and mono-, diand triethanolamine salts of dodecyl and tridecyl benzene sulfonates and petroleum sulfonates are additional anionic surfactants which can be employed in the method of this invention. The term petroleum sulfonates is used herein in its well-known meaning wherein said petroleum moieties are, primarily, naphthenes, fatty and. aromatic acids and aliphatics.

Taurate salts are also suitable anionic detergents; for example, the taurate salts of Na, K, NH Ca, Mg, Li and mono-, diand triethanolamine are useful in the method of this invention. Taurate salts of the general formula Fatty acid NCH2OHiSO X Alkyl or Cycloalkyl wherein X is one of the above mentioned metals or amines,

are generally suitable. Examples of the fatty acid moiety include oleyl, palmitoyl, tall oil and tallow.

A preferred class of anionic detergents are the phosphate esters. The class of phosphate esters which have been most successfully employed are those of the general formula wherein n represents an integer from 2 to 4; m represents an integer from to about 12; p represents an integer from 1 to 2; -R represents a radicalvselected from the group consisting of hydrogen, alkyl, phenyl, alkylphenyl and arylphenyl, said alkyl moieties having from 1 to about 20 carbon atoms; and when R is hydrogen, m is at least 1; and when m is 0, R is a carbon chain of at least 4 carbon atoms; and, M being hydrogen or a (water-soluble) saltforming cation such as sodium, magnesium, potassium, ammonium, alkyl ammonium or the like. The phosphate esters can be prepared in any of the well-known manners, such as described, for example, in US. Pat. No. 3,004,056 or Kosalapoif, G. A. Organophosphorous Compounds, John Wiley and Sons, Inc., New York (1950). A particularly suitable class of phosphates falling within the class above set forth are those phosphate esters having the following formulas:

Pat. No. 3,004,056. U

6 NONIONIC DETERGENTS wherein n represents an integer from 2 to 4; a represents an integer from 2 to about x is an integer from 1 to 2; and Z represents an alkyl radical having from 4 to 20 carbon atoms. Suitable surfactants falling within this class of nonionics above outlined are nonylphenoxy octa(ethoxy)ethano1, butylphenoxy tetra(ethoxy)ethanol, cosylphenoxy octadeca(ethoxy)ethanol and the like.

Representative of nonionic surfactants falling within the other enumerated classes are: alkanolamine fatty acid H condensates, long chain alcohol ethylene oxide condensates, alkyl polyoxyethylene amines and amides, ethoxylated lauric acid, .glyceryl trioleate, sorbitan monooleate and alkyl dimethyl amine oxide.

SPECIFIC EMBODIMENTS Example 1 The method of the present invention was tested under commercial conditions as follows:

An industrial dry cleaning machine was used in the following test The machine had a fabric capacity of 1b., a 50 gal. holding tank for the solvent used in Step 1, a gal. holding tank for the solvent used in Step 2, and a 50 gal. holding tank for the solvent used in Step 3. The machine was also equipped with a main still (capacity 260 gal.), a filter still (capacity 230 gal.), and a bump filter (capacity 77 gal.).

Step l.-l08 lbs. of dark colored, highly soiled cotton coveralls (grease, dust, carbon black and other particulate soil and water soluble soils, such as perspiration) were placed into the wash wheel, i.e., washing container. To the coveralls was then added the following formulation:

Perchloroethylene-SO gal. (97.9 volume percent) H O1 gal. 2.0 volume percent) Detergent-0.0625 gal. (0.1 volume percent) The detergent used had the following composition:

Weight percent (A) CnHw 0-(CgH4O)5aO-POH 15 O-+Na I] (B) CnHm 0-(C2H4O)5's-O-P-Ot0H4C2)s-u0-Cu 19 5 H (C) CuHzI-O-{C2H40)a'1O-POH 22. 5

((13) O(C H O)- H 45 .A.. .V V r.-

Perchloroethylem m.

The coveralls were then agitated in the above mixture for 4 minutes. The liquids were then extracted by rapidly revolving the wash wheel for 3 minutes. The extracted solvent was then sent to the main still, and the distillate removed to the holding tank for Step 3.

Step 2.-'Ihe coveralls were then subjected to a continuous cleaning cycle for 9 minutes, with constant agita tion, about 60-80 gal. of solvent-detergent being present in the wash wheel at one time. The solvent detergent mixture used in this step comprises about 95 volume percent perchloroethylene and up to 5 volume percent of a mixture of the same detergent as used in Step 1, but in the following proportions:

Weight percent The solvent-detergent mixture was continuously recycled between the Wash wheel and the holding tank. This mixture was filtered between the holding tank and the wash wheel. The liquids were then extracted as in Step 1, the extraction lasting about 2 minutes, the extract being returned to the holding tank. Step 3.--The coveralls were finally agitated for 4 minutes in 50 gal. (99.875 volume percent) of perchloroethylene to which had been added 0.0625 gal. (0.125 volume percent) detergent. The detergent Was the same composition as described in Step 1. The liquids were then extracted, as previously done, for 3 minutes. The extract was then removed to the holding tank for 'Step 1. It is to be noted that sutficient detergent was carried over from Step 3 to the Step 1 holding tank, that no further detergent needed to be added for a subsequent Step 1 operation.

The coveralls were then dried by hot air (about 190 F. air heated by passing over steam coils) for 20-30 minutes. The recovered solvent-H O vapor from this operation were removed to a H O separator, the H going to a sewer while the solvent was removed to the holding tank for Step 3.

Example 2 The 3step process of the instant invention was compared with a commercially available 2-step industrial dry cleaning process, the two processes being of about the same cleaning duration.

In the same machine as described in Example 1, 108 lbs. of the same type coveralls as previously described, along with 2 clean, new white shirts, one 100% cotton and the other 65%-35% polyester/cotton, were placed in the wash wheel. The 3-step method of the invention was then carried out exactly as previously described in Example 1, Le, 17 minutes total cleaning time.

The 2-step process was carried out in a machine essentially the same as above, except that it had a fabric capacity of about 165 lbs. The machine was loaded with coveralls and 2 shirts of the same material as were loaded into the 3-step process machine.

The 2-step process was essentially as follows:

Step A.The fabric load was agitated for 3 minutes in a perchloroethylene-water-monovalent imidazoline salt detergent mixture. The liquid was then extracted as above for about 2 minutes, the extract removed to a still, and the distillate stored for subsequent use in Step 1.

Step B.The fabric load was then subjected to a continuous cleaning cycle for 13 minutes, with continuous agitation, in a perchloroethylene-detergent mixture (similar to that used in Step 1 of the 3-step method). The solvent-detergent mixture was continuously recycled between the wash wheel and the holding tank, and continuously filtered between the holding tank and the wash wheel. The liquid was then extracted as above for 2 minutes, and the fabric load dried as in Example 1.

The 2 sets of shirts from the above two processes were then compared for brightness on a Hunterlab model D-40 Refiectometer (Hunter Associates Laboratory, Inc., 9529 Lee Highway, Fairfax, Va.). The results are found in FIG. 4. t

It is to be noted that the results shown in FIG. 4 are the result of severe conditions due to cleaning the shirts in the presence of dark, oily coveralls. Therefore, if light garments of a similar type soil load are compared when cleaned in the absence of high soil loads, the trends found in FIG. 4 will hold true, but the numerical differences between the two processes would be greater, and the brightness index would be generally higher.

We claim:

1. An improved method for dry cleaning fabrics, which comprises:

(a) contacting the fabric with a dry cleaning solvent containing from 0.005 to 25 volume percent of H 0 and from 0.01 to 5 volume percent of an anionic or nonionic dry cleaning detergent or mixture thereof for from one to 20 minutes, then removing the liquid; and then, in any order (b) contacting the fabric with a dry cleaning solvent containing from 0.01 to volume percent of an anionic or nonionic drycleaning detergent or mixture thereof for from one to minutes, then removing the liquid; and

(c) contacting the fabric with a dry cleaning solvent containing from 0.01 to 5 volume percent of an anionic or nonionic dry cleaning detergent or mixture thereof for from one to 20 minutes, then removing the liquid.

2. The method of claim 1 wherein the contact time is 2 to 12 minutes in step (a), 3 to 15 minutes in step (b) and one to 12 minutes in step (c).

3. The method of claim 1 wherein the detergent is a mixture of anionic and nonionic detergents in steps (a) and (b); and the detergent is anionic in step (c).

4. The method of claim 1 wherein the solvent is a chlorinated hydrocarbon.

5. The method of claim 1 wherein 0.005 to volume percent H O may be utilized in (c).

6. The method of claim 1 wherein, in the individual steps:

(a) the detergent is anionic, nonionic or mixtures thereof, the solvent is a chlorinated hydrocarbon, and the contact time is 2 to 12 minutes;

(b) the detergent is anionic, nonionic or mixtures thereof, the solvent is a chlorinated hydrocarbon, and the contact time is 3 to 15 minutes; and

(c) the detergent is anionic, the solvent is a chlorinated hydrocarbon, and the contact time is one to 12 minutes.

H 7. Themethod of claim 6 wherein the contact time is 2 to 8 minutes in step (a) and one to 8 minutes in step (c).

. 8. The method of claim 6 wherein the detergent is a phosphate ester or petroleum sulfonate in steps (a) and (c) and a phosphate ester plus a nonionic detergent in step (b).

9. The method of claim 6 wherein the solvent is perchloroethylene.

10. The method of claim 1 wherein, in the individual steps:

(a) the detergent is a phosphate ester or a petroleum sulfonate, and the contact time is 2 to 8 minutes;

(b) the detergent is a phosphate ester plus a nonionic detergent, and the contact time is 3 to 15 minutes; and

(c) the detergent is a phosphate ester or a petroleum sulfonate, and the contact time is one to 8 minutes.

11. The method of claim 1 wherein the order of the steps is (a) (b) (c).

12. The method of claim 1 wherein the order of the 9 13. An improved method for dry laundering fabrics,

which comprises:

(a) contacting the fabric with about 97.9 volume percent perchloroethylene, about 2.0 volume percent water, and about 0.1 volume percent of a detergent composition comprising the following:

Weight percent (A) 16.5 (B) 8.5 (C) 25.0 (D) 50.0

Weight percent u (A) 09H" O-(C2H40)5-eO-P0H 15 H (B) Cn w -(02 40)5n- --P-0+0H4C2)5-5O--C:Hm 7. 6

II (C)..- C aH21- 2 4O)u-7OP0H 22. 5

O-+Na (D) CnHm 0(C2H40)4H 45 Perchloroethy 10 for about 9 minutes, and then removing the liquid; and

(c) finally contacting the fabric with 99.875 volume percent of perchloroethylene and 0.125 volume percent of the same detergent composition as used in step (a) above, and then removing the liquid.

References Cited UNITED STATES PATENTS Mathews et a1 68-13 R Henderson 68-13 R Mathews 68-13 R Gillespie 68-13 R Sugarman et al. 252-171 Knieriem, Jr 8-142 X Nunn, In, et al. 252-351 X Moore 8-142 X Chisholm 252-351 X MAYER WEINBLA'IT, Primary Examiner U .S. C]. X.R.

8-137; 68-13 R, 18 F, R, C; 252-170, 171

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,689,211 D d September 5, 1972 nv nt r(s)John J. Giampalmi, Jr. Istvan K. Telegdy; & Manfred Wirth It is certified that error. appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5 line 45, correct the formula to read as follows "1 Column 6, line 49 insert a parenthesis before "2.0" so that the line will read as follows: v

H O 1 gal. (2.0 volume percent) Column 6, second formula in the table, correct the formula to read as follows (this correction was authorized in an Examiner's Change dated April 18, 1972) Column 9 Claim 13, second formula in the table, correct the formula to read as follows (this correction was authorized in an Examiner's Change dated April 18 1972) Signed and sealed this 13th day of March 1973.

L (SEAL) Attest: I .5

EDWARD M.FLETCHER,JR. ROBERT GOTTSCAHLK Attesting Officer Commissioner of Patents