US3285858A - Dry cleaning solvent - Google Patents

Description

United States Patent 3,285,858 DRY CLEANING SOLVENT Alfred Hirsch, Mentor, Francis Huba, Painesville, and Roland J. Horvath, South Euclid, Ohio, assignors to Diamond Alkali Company, Cleveland, Ohio, a corporation of Delaware No Drawing. Filed Aug. 7, 1964, Ser. No. 388,277 6 Claims. (Cl. 252171) This invention relates to halogenated solvents, and more particularly to improved solvent compositions suitable for use in the dry cleaning and specialty cleaning arts, and characterized by selective solvent action, good thermal stability, convenient boiling point range, and low flammability and toxicity.

Because of their wide use in large quantities by persons of relatively little training in the handling of toxic or dangerous chemicals, cleaning solvents must be relatively safe to use. They must also have selective solvent action so that they will dissolve and wash away undesirable dirt and grease without dissolving portions of the oods being cleaned. Moreover, the solvents should have a low degree of flammability and a boiling point which is high enough to avoid excessive loss at dry cleaning temperatures and yet low enough to permit easy removal of the solvent from the goods after cleaning.

The substances currently in widest use as solvents for cleaning both fabrics and special items such as electronic components and magnetic tapes are chlorinated solvents such as trichloroethylene, erchloroethylene and methylchloroform. Their major disadvantages include boiling points too high for convenient use and the property of dissolving certain plastics used, for example, in buttons and ornamentation on clothing and also in certain types of electrical mountings, insulations and color codings. Perchloroethylene has the additional disadvantage of being toxic enough to require rather careful handling.

Another common cleaning solvent, carbon tetrachloride, is so toxic as to create a serious health hazard, especially when used in large quantities. Stoddard solvent, a high boiling petroleum naphtha fraction, is quite flammable and is also hard to remove after the cleaning process because of its low vapor pressure. 1,1,2-trichloro-1,2,2-trifluoroethane, a dry cleaning solvent recently described in US. Patent 3,042,479, is too expensive for wide use, has limited solvent power and is also extremely volatile (boiling point 46 C.) so that solvent losses are a serious problem in normal cleaning processes. Indeed, it is often necessary to refrigerate the solvent for recovery.

A principal object of the present invention, therefore, is to provide new solvents which are useful for cleaning a wide variety of items and substances.

A further object is to provide compositions with selective solvent action, thermal stability and non-flammability and favorable physical properties for cleaning solvent applications.

A further object is to provide solvents which have low toxicity.

Still another object is to provide a solvent which may be used in a number of cleaning applications including dry cleaning, cold cleaning, ultrasonic cleaning, vapor degreasing and the like.

Other objects and advantages of the present invention will in part be obvious and will in part appear hereinafter.

3,285,858 Patented Nov. 15, 1966 "ice The present invention comprises a composition of matter suitable for use as a cleaning solvent which contains a major proportion of at least one tetrachlorodifluoroethane. More specifically, it comprises a solvent consisting essentially of a substantially constant-boiling mixture of major proportion (about 85% by weight) of tetrachlorodifiuoroethane and a minor proportion (about 15-30% by weight) of at least one diluent therefor, said diluent being a halogenated hydrocarbon which is normally a liquid at room temperature.

Tetrachlorodifiuoroethane (C Cl F exists in two isomeric forms, symmetrical and unsymmetrical, melting at 238 C. and 406 C., respectively. Both isomers boil at about 92 C. A mixture of these two compounds is commercially available and has a melting point of 30.6 C. It has been found that tetrachlorodifiuoroethane has excellent solvent properties for dry cleaning purposes;' however, its high melting point precludes its use in pure form. According to this invention, therefore, the melting point of tetrachlorodifiuoroethane is depressed by the addition of about l530%, preferably about 2025%, by weight of a liquid halogenated hydrocarbon diluent.

In commercial use, it is important that the composition of a dry cleaning solvent remain constant or nearly constant even after repeated cleaning cycles. When the solvent is a single compound, this presents no problem. But when a mixture of compounds is used, there may be a change in composition as it is used unless the components are chosen carefully with an eye toward behavior on distillation or vaporization. A material of essentially constant composition may be obtained by choosing an azeotropic mixture or by using components whose boiling points are so close that separation under the conditions of use does not occur. For the purpose of this invention, two compounds have been found particularly useful and are preferred diluents for depressing the melting; point of tetrachlorodifiuoroethane; they are trichloroethylene (B.P. 87 C.) and l,l,2-trichloro-l-fiuoroethane (B.P. 88C.).

l,1,Z-trichloro-l-fluoroethane may be prepared by either of two methods. The first and preferred method is by the reaction of trichloroethylene with hydrogen fluoride in the presence of a Lewis acid catalyst (e.g.,. boron trifiuoride), as described in British Patent 684,117. This method gives the desired product in about 80% yield; because of the closeness of the boiling points of starting material and product, the reaction mixture may be subsequently chlorinated to convert unreacted trichloroethylene to pentachloroethane before the product is separated by distillation. Alternatively, since either the reactant or the product may be used as diluents, separation thereof may be eliminated and the mixture used directly.

An alternative method for the synthesis of 1,1,2-trichloro-l-iluoroethane is by the reaction of 1,l,l,2-tetrachloroethane with hydrogen fluoride in the presence of an antimony fluoride catalyst.

As indicated hereinabove, the preferred composition of the solvent of this invention is about -80% (by Weight) tetrachlorodifluoroethane and about 20-25% trichloroethylene or l,l,Z-trichloro-l-fluoroethane. Solvents with this composition have melting points in the range of about -30 to 20 C., and boiling points of about 88 C.

The compositions of this invention have a combination of properties which make them excellent for use as dry They are substantially less toxic than cleaning solvents.

perchloroethylene. Their vapor pressure is high enough Table I so that they can easily be removed from fabrics at moderate temperatures, leaving little or no odor. They are SolventA SolventB stable over long storage periods and at temperatures as :1 high as 200 C. (392 F.). They are non-flammable and 0 lo I) 1) (i) onorrosive, and are compatible wlth a w i q 0f i:: "II 87-88 88-83 12% emulsifiers and dry cleaning soaps. The emu s1 ers may M.P., C

--20 -2 2 t 20C. 1.615 1.610 1.623 be present in quantities up to 2% by we1ght. The followg fz gt g if gl i 215 214 205 s 1 '1' en ing are exemplary of emulsifiers 1n current use gg z ggfi fj 0.011 M17 M06 10 Non-1on1c: 1C 1 l Ethylene oxide condensation products of phenols f and high molecular weight aliphatic alcohols, Toxicity measurements show that Solvent A is about Phosphate esters of the above, one-half and Solvent B about one-fifth as toxic as per- Sorbitan monooleate-fatty acid ester combinations, chloroethylene. V V c i i V H W Other physical properties *WlllCh are important to the Cyclic tertiary amines, action of a dry cleaning and specialty solvent include Tetrakis(2-hydroxypropyl)ethylenediamine esters of evaporation rate, solvent power (kauri-butanol number high molecular weight carboxylic acids, quaterand mixed aniline point) and surface tension. These nized with dimethyl sulfate, properties are determined by standard methods established Anionic: Alkali metal and amine salts of petroleum sulby the American Society for Testing Materials. The evapfonates, alkyl aryl sulfonates, ether sulfonates, caroration rate is based on a figure of 100 for carbon tetraboxylic-sulfonic acid esters, etc. chloride. The kauri-butanol number 1s an empirical I figure which increases with increasing solvent power. The solvent compositions of this invention are also use- Th mi ed aniline oint i the temperature at whi h a 1 for cleaning metal stampings, magnetic tapes, printed standard solute dissolves and therefore decreases with circuits, vacuum tube parts, and electronic components increasing solvent power. Surface tension is determined such as switches, relays, potentiometers and resistors, by means of the capillary rise method. These properties since, in addition to the advantageous properties described are iv n for several solv nts i Tabl II,

Table II Solvent Power Surface Solvent Evapora- Tension,

tion Rate Kauri- Mixed dynes/cm.

Butanol Aniline (20 C.) Number Point C.

Solvent A 67 24. 0 Solvent B 69 24. 8 Perchloroethylene 41 Trichloroethylene 84 31. 6 Carbon tetrachloride. 100 26. 8 Methylchlorofonnn 139 25. 5 Chloroform 118 27. 2 Methylene chloride. 147 28. 2 Stoddard solvent, B.P. 310-388" F. 61 1,1,Z-trichloro-l,2,2-trifluoroethane 170 19.6 Tetrachlorodifiuoroethaue 1,1,2Ftrich1oro l-fluoroethane. Kerosene n-Heptane .4 Petroleum naphtha 4 Water ,8

hereinabove, they have a selective solvent action whereby they readily remove soldering flux, dirt, and other undesirable materials but do not attack plastic or fabric insulating materials and color codings, on resistors and the like. Further, they are relatively poor solvents for lubricant materials used on potentiometers and the like; this is an advantage because it is desirable that such lubricant materials remain on the parts through the cleaning process.

In the following description and examples, two specific solvent compositions are representative of the composi tions of this invention. All percentages are by weight unless otherwise indicated.

Solvent A contains 80% C Cl F and 20% CHC1=CC1 Solvent B contains 75% C Cl F and 25% CH CICCI F Table I gives various physical properties of Solvent A, Solvent B and perchloroethylene.

It will be seen from Table II that Solvents A and B have intermediate evaporation rates, high enough for, easy EXAMPLE I.PREPARATION OF 1,1,2-TRI- CHLORO-l-FLUOROETHANE A one-gallon stainless steel autoclave is charged with 2630 g. (20 moles) of trichloroethylene and 26.3 grams of boron trifluoride (in the form of a methanol solution). The autoclave is sealed and 800 g. (40 moles) of hydrogen fluoride is introduced. The system is heated to 150 C and maintained at that temperature with stirring for about two hours; the internal pressure is about 600 psi.

The autoclave is then cooled and vented; the unreacted hydrogen fluoride is absorbed in ice water. The product liquid (shown by vapor phase chromatographic analysis to be 78.4% 1,1,Z-trichloro-l-fiuoroethane, 19% trichloroethylene and 2,6% 1,2-dichloro-1,l-difluoroethane) is 6 EXAMPLE 3 The compatibility of three solvents with common emusifying agents .used in dry cleaning is tested by measuring the solubility of water in a solution of 1-2%' by volume of the emulsifier in the solvent. All listed emulsifiers are anionic with the exception of Kleerwite 200, which is nonionic. Results are given below.

Water Solubility (Percent by weight) Emulsifier (Percent by volume) Solvent A Solvent B Perchloroethylene None Perclite (Signal Chemical Co.) Power Pack (Pennsalt Chemical Corp.) Buckeye 250 (Davis Young Soap Co.) Code 166 (Davis Young Soap Co.) Fortified Power Pack (Pennsalt Chemicals Corp). Kleerwite 200 (Marclene Chemical Co.)

Pace Perk (Caled Products) 1 Cloudy.

fluoroethane, is collected at 88 C. at atmospheric pres- 35 sure.

From the above it will be seen that the compatibility of the solvents of this invention with common dry cleaning emulsifiers is comparable to that of perchloroethylene.

EXAMPLE 4 Corrosion studies are run on a number of metal and plastic-coated metal strips by allowing a stream of moist air containing by volume of solvent to pass over the strips for fourteen hours at 120 and 200 C. Results are given below, in terms of corrosion in mils per year.

120 C. 200 C. Test Strip Solvent A Solvent B Perchloro- Solvent A Solvent B Perchlorae hylene r ethylene Chrome plated steel 0. 09 0.12 0.61 0. 51 0.44 0, 56 Nickel plated steel O. 0. 36 0. 65 0. 48 0. 39 0. 41 Tin plated steel. 0. 94 0. 85 l. 59 5. O8 4. 84-. 3. 78 Copper 1.47 3. 34 1.47 3. 28 7.29 32. 78 Brass--- 0.92 2.17 0.93 3. 24 3. 73 3.18 Zinc 0. 03 4. 96 1. 44 O. 91 0. 30 0. 42 Aluminum 2. 52 1. 59 2. 62 5. 74 2. 64 4. 42 Shim steel. 0.30 0. 94 1.15 1. 58 l. 28 0.89 Galvanized 2. 87 l. 74 0. 5. 01 6. 53 4. 39 Rubber... Vinyl coat on aluminum (l Acrylic coat on aluminum 5 a 2) Polyvinyl fluoride coat on aluminum. (t) 2 2 a 1 Darkened. 2 N 0 change. 3 Partially dissolved. 4 Turned tan. 6 Turned pink. 6 S1. darkened.

EXAMPLE 2 EXAMPLE 5 Comparative laboratory tests are run on the ability of three solvents to remove oily materials from wool; results are given below. (Lanolin is an ingredient in many cosmetics; cetyl alcohol is present in lipsticks; and oxidized trioleum is a typical degradation product formed when skin secretions remain in prolonged contact with clothing.)

From these results, it will be apparent that both Solvent A and Solvent B are equally as effective or more eifective than perch-loroethylene.

The effect of the solvents of this invention and of perchloroethylene on plastics used to make buttons, belt buckles and other textile ornamentation is tested by placing a weighed sample of the plastic in a vial of solvent and agitating at 24 C. for one hour on a shaker machine. The solvent is then drained and the sample is dried for one hour at a pressure of 10 mm. of mercury and weighed. Percent Weight change and visual appearance are tabulated below for the following samples.

1Styrene-but-adiene-acrylonitrile copolytner, molding grade.

2Same, extrusion grade.

3Melamine resin.

4, 5Cellulose acetate butyrate.

6Cellulose acetate.

7Acrylate molding powder.

Solvent A Solvent B Perchloroethylene Sample No.

Percent wt. Physical Percent wt. Physical Percent wt. Physical change appearance change appearance change appearance Key to physical appearance: Ono visible effect; Table IV 1lost lustre; 2lost lustre, blanched; 3lost lustre, etched. Cleaning I EXAMPLE 6 Solvent time, Tape Condition see. A two-inch sample of video recording tape is placed in s 1 t A 90 Cl E t f 0 Vel'l 0311,1106 9C 011 CO3 in a Soxhlet extractor; the extractor flask 1s filled with sol- Solvent B 90 Clean, no efiect 0n coating.

Perchloroethylene 30 Pinholes in coating. vent and the solvent is heated under reflux. After 20 Trichloroethylene 30 About 3 of coating w move passes of solvent through the extracto? tape Methylchloroform 10 About 5% of coatingremoved, dried and examined to determine its condition. m ved.

1,1,2-trich10ro-1,2,2-trifluoro- 90 Pmholes in coating. Table III glves results for a number of solvents. ethane,

Table These results show that Solvents A and B are superior to T di the other solvents tested in that they cause no deteriorasolventl' A N con tion of the tape within the time allotted for the test, and so vent O c ange Yet are completely effective in cleaning the tape during Solvent B No change. this period Perchloroethylene Some removal of coating at It is desirable that a solvent which is to be used for foldscleaning electronic parts have a high capacity for removal Trichloroethylene Co a t i n g about 3% reof flux. Therefore, several solvents are tested for their 1 H moved. capacity to remove Kester electronic soldering fiux under Methylchloroform C o a tin g about 2% reultrasonic 9183111118 condlfilonsmoved 4 In Test A, a thin coatlng of soldering flux is applied to k Y 0 l wei bed and cleaned 'lass late which meast t 1 a previous y g g p Methylene chloride C f z g comple e y I ures about 1% x 3 inches. The plate is rewelghed after 1 1 2 trich1mo 1 2 m the application of the flux coating and is then suspended in a test tube containing the solvent, in an ultrasonic genfluomethane gf m coating at 5 erator identical with that used in Example 7. The plate These results show that Solvent A and Solvent B are superior to prior art solvents in their physical eiiect on magnetic tape.

velopment Company).

maximum cavitation.

EXAMPLE 7 sults are shown in Table IV.

is treated with the solvent for 5 seconds and then air-dried and weighed. In Test B, the flux-covered plate is baked for 5 minutes at 340 F. prior to cleaning. The results of these tests are summarized in Table V.

Table V Test A Test B Solvent.

Percent Plate Solvent appearance after 16 Percent Flux Appearance hours Flux removed removed Solvent A 99.39 Clean Flux in suspension. 60. 3 99. 84 do do 95. 9 99. 13 White residue. Flux in solution 99 08 Trace residue do 73. 5 99.79 White residue Some flux precipitated 92. 4 1,1,2-trich1oro-1,2,2-trifluoroethane 98. 99 do Flux precipitated 50. 5

It will be seen from Table V that Solvents A and B are superior to all other solvents except methylchloroform for the removal of flux under normal conditions. They are superior to methylchloroform in the condition of the plates and solvent after the cleaning process. Further, Solvent B is vastly superior to all other solvents tested in removal of flux after baking.

EXAMPLE 9 This example tests several solvents for the removal of 7 lubricants used on electronic parts such as potentiometers. 5 Glass plates similar to those used in Example 8 are coated 9 r with Walsco 2601 lubricant. The plates are weighed before and after coating and are then dipped in the solvent for a period of 30 seconds. They are removed, dried and reweighed to determine the percentage of lubricant re- The results of this test show that Solvents A and B are superior to trichloroethylene and perchloroethylene in that they remove much less lubricant.

EXAMPLE 10 Resistors and similar parts used in electronic circuits usually have color codings on their surfaces to show their resistances in ohms and other properties. It is essential that solvents used for cleaning these resistors should not dissolve or obliterate the coding marks,

In this example, resistors are soaked for minutes in a number of solvents and are then dried and examined for survival of the coding marks. Solvents A and B and 1,1,Z-trichloro-l,2,2-trifiuoroethane have no effect on the resistor color codings. In the cases of perchloroethylene, trichloroethylene and methylchloroform, the codings are obliterated by scraping after treatment with the solvent. This example shows that the solvents of this invention are superior to many of those previously known in that they do not damage the surfaces of resistors and other colorcoded articles.

EXAMPLE 11 The behavior of Solvent B as a dry cleaning solvent in actual use is tested by running a number of dry cleaning loads in a Westinghouse Laundromat coin-operated dry cleaning machine. The solvent contains 1% of Perk Sheen 324 detergent (Adco, Inc.), an anionic emulsifier, and 0.07% each of epichlorohydrin and ethyl acetate as stabilizers.

The machine is operated on the following cycle.

Operation: Time, min. (A) Load Variable (B) Wash 6 (C) Drain 1 (D) Spin 4 (E) Auto dry Variable (F) Hot air dry 2 (G) Cool 3 (H) Purge 3 (A) As machine operation is begun, the clothes are tumbled at 51 rpm. as solvent enters the tub from the storage tank through a filter.

(B) When sufficient solvent is in the tub, the washing cycle begins. The solvent is continually circulated through the filter to avoid soil buildup.

(C) During the drain period, the solvent is returned (through the filter) to the storage tank.

(D) Drainage of solvent is completed by spinning the clothes at 265 rpm.

(E) During the auto dry period, air heated to 104 107 C. is blown over the clothes. The effluent air containing solvent vapors is cooled by passage through a water-cooled condenser at about 40 C.; the condensed solvent and water are directed to a separator from which the solvent is returned to storage and the water is dis- 10 carded. Air from the condenser is reheated and recycled to the tub. As the solvent content of the efiluent air decreases, the air temperature rises; when it has reached 74 C., a thermostat returns the machine to the programmed cycle.

(F) Hot air continues to circulate for two minutes after the auto dry period.

(G) Unheated air is passed into the tub to cool the clothes.

(H) Finally, fresh air is drawn into the machine from the atmosphere and vented to the atmosphere in the purge operation,

A total of cycles are run over a ten-day period. In each cycle, a load of clothes weighing approximately eight pounds is cleaned; each load contains a wide variety of fabrics and colors. The amount of dirt in the clothes varies from light to heavy; a number of maintenance loads containing a very high grease, oil and tar content are also run.

Cleaning abilizy.A qualitative comparison of clothes cleaned with Solvent B with clothes cleaned with perchloroethylene indicates that Solvent B is at least as effective as perchloroethylene and possibly more effective. Quantitative tests, run on cloth swatches containing four standard soil samples, indicate that Solvent B is, on the average, 9.08% to 10.73% more effective than perchloroethylene.

Soil redeposition.Examination of wool and cotton swatches included in several loads during the test shows that soil redeposition is about 15.3% to 17.3% less with Solvent B than with perchloroethylene.

Dye bleeding.No evidence of dye bleeding is noted, even after cleaning of a red load containing clothes of various fabrics all of which are red except for one pair of white pants. Even striped garments (e.g., red and white stripes) show no bleeding.

Shrinkage-Shrinkage of wool garments is about 24%, which is comparable to that resulting from cleaning with perchloroethylene.

Solvent retention.Qualitative comparisons indicate that clothes cleaned with Solvent B have less residual solvent odor than clothes cleaned with perchloroethylene.

Solvent acidity.--No acidic decomposition products are detected in the purge air or in the water separated from the solvent during the auto dry period.

Solvent recovery.-Most of the solvent is recovered during the drain and spin operations. The remainder is removed during the auto dry process, the length of which is an indication of the condensation rate of the solvent. Recovery of Solvent B is virtually complete after thirteen minutes of drying, as compared with eighteen minutes for perchloroethylene.

It is to be understood that the invention is not limited by the specific examples and embodiments described hereinabove, but includes such changes and modifications as may be apparent to one skilled in the art upon reading the appended claims.

What is claimed is:

1. A cleaning solvent consisting essentially of a substantially constant-boiling mixture of about 70-85% by weight of at least one tetrachlorodifiuoroethane and about 1530% by weight of 1,1,2-trichloro-l-fiuoroethane.

2. A cleaning solvent consisting essentially of about 7580% by weight of a mixture of isomeric tetrachlorodifiuoroethanes and about 2025% by weight of 1,1,2- trichloro-1-fiuoroethane.

3. A cleaning solvent consisting of about 75% by weight of a mixture of isomeric tetrachlorodifluoroethanes and about 25% of weight of 1,1,2-trichloro-1-fiuoroethane.

4. A dry cleaning composition comprising the composition of claim 1 in combination with up to about 2% 1 1 12 by weight of an emulsifying agent selected from the group References Cited by the Examiner consisting of anionic, cationic and nonionic types. UNITED STATES PATENTS v 5. A dry cleaning composition comprising the co 2,212,761 9 /1940 Webster 52 172 position of claim 2 in combination with up to about 2% 2 74 034 5 /1956 D L at 252-172 by Weight of an emulsifying agent selected from the group 5 3,042,479 7/1962 Lawrence et a1, 252172 X consisting of anionic, cationic and nonionic types.

6. A dry cleaning composition comprising the composi- LEON D ROSDOL Primary Examiner tion of claim 3 in combination with up to about 2% by JULIUS GREENWALD, ALBERT MEYERS, weight of an emulsifying agent selected from the group 10 SAMUEL BLECH Examiners" consisting of anionic, cationic and nonionic types. S. E. DARDEN, Assistant Examiner.

Claims (2)

1. A CLEANING SOLVENT CONSISTING ESSENTIALLY OF A SUBSTANTIALLY CONSTANT-BOILING MIXTURE OF ABOUT 70-85% BY WEIGHT OF AT LEAST ONE TETRACHLORODIFLUOROETHANE AND ABOUT 15-30% BY WEIGHT OF 1,1,2-TRICHLORO-1-FLUOROETHANE.

4. A DRY CLEANING COMPOSITION COMPRISING THE COMPOSITION OF CLAIM 1 IN COMBINATION WITH UP TO ABOUT 2% BY WEIGHT OF AN EMULSIFYING AGENT SELECTED FROM THE GROUP CONSISTING OF ANIONIC, CATIONIC AND NONIONIC TYPES.