Abstract:
Disclosed are formulations for producing chemical solvent admixtures that can be employed to clean a surface for further work; and that can be applied to cloths for the cleaning operation yet alleviate problems with solvent evaporation into the atmosphere to cause many legal and environmental problems, and a method of storing and disposing of cloths soaked with the formulation that alleviates current problems.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This Application is a continuation-in-part of U.S. patent application Ser. No. 08/004,438, filed on Jan. 14, 1993, now abandoned which is a continuation-in-part of U.S. patent application Ser. No. 07/991,378, filed Dec. 16, 1992, now abandoned which is a continuation-in-part of U.S. patent application Ser. No. 07/743,258, filed Aug. 9, 1991, now U.S. Pat. No. 5,188,754 which is a continuation-in-part of U.S. patent application Ser. No. 07/686,180, filed Apr. 16, 1991, now abandoned, which is a continuation-in-part of U.S. patent application Ser. No. 07/614,228, filed Nov. 15, 1990, now abandoned. 
    
    
     FIELD OF INVENTION 
     This invention relates to cleaning formulations and method of handling cloths soaked therewith. More particularly, it relates to a formulation or solvent that can be employed to effect good cleaning and alleviate current problems; for example, a solvent blend that can be employed to remove soils from a surface when applied to a cloth and a method of handling the solvent-laden cloths that alleviates problems experienced heretofore. 
     BACKGROUND OF THE INVENTION 
     The prior art is replete with a wide variety of different types of formulations and allusion to the problems created with their use. For example, the nearest approach of which we are aware involves wiping the surface to be cleaned with a cloth on which a solvent; such as methyl ethyl ketone; or a solvent blend, or formulation, such as methyl ethyl ketone, aromatic naptha, isopropyl alcohol, and ethyl acetate has been applied. Other solvent blends that include chlorofluorocarbons and trichloroethane are also used. The wipe cloths are then open to the atmosphere or are transferred to a metal can for temporary storage. The cloths then go through several stages of transfer and storage until they are eventually laundered, buried as a solid waste or incinerated. 
     Alternatively, the wiping operation is performed or the cloths stored in an enclosed area equipped with forced ventilation and a carbon absorption system. The solvent vapors from the surfaces being cleaned and from the used wipe cloths are carried into the filtration media where they are partially absorbed. Periodically the solvents are stripped from the carbon and are incinerated. 
     Several disadvantages are inherent in these prior art type systems and deleterious effects result therefrom. Using the first approach, the solvents evaporate rapidly from the work piece during the wiping operation and further evaporation takes place from the solvent-laden wipe cloths during storage and transfer prior to their final disposal. The emissions from certain solvents eventually reach the atmosphere where they react with other air emissions in the presence of sunlight to form ozone and/or create smog. 
     Alternatively, certain other solvent emissions will reach the stratosphere where they deplete the protective ozone layer, causing extensive damage to animal and plant life on earth. These solvents are primarily chlorofluorocarbons and trichloroethane. There are federal, state and local regulations that restrict volatile emissions from cleaning operations and violations can lead to severe penalties including fines, incarceration of managing personnel, and shut down of the offending facility. 
     Many of these solvents have been banned by federal statute. The federal statute entitled &#34;Clean Air Act&#34; was passed by Congress in 1990 and signed into law. This law curtails the use of such common solvent cleaners as chloroform, dichloromethane, methyl ethyl ketone, methyl isobutyl ketone, toluene, trichloroethylene, trichloroethane and xylenes. A formulation which contains none of these curtailed ingredients but which are efficient cleaners and have low flammability, low toxicity and slow evaporation rates should have wide acceptance in many industries. 
     The carbon absorption system for collection and disposal of wipe solvents has other disadvantages. It is expensive to install and to operate and has limited collection efficiency and capacity. Moreover, such a system is not feasible in large facilities where cleaning operations are required in widely scattered locations, but requires rather closely located areas and a central facility. 
     This invention overcomes these disadvantages and deleterious effects. Specifically, it is desirable that a cleaning formulation have the following features: 
     1. The formulation should achieve superior cleaning with a considerable reduction of volatile emissions to the atmosphere. 
     2. The formulation should have excellent cleaning efficiency for a wide variety of soils. 
     3. The cleaning formulation should have a low evaporation rate, low toxicity, and be nonflammable; for example, as demonstrated by having a flash point of 100 degrees Fahrenheit or higher when measured by the closed cup method. 
     In addition, the method of disposing of cloths soaked in the formulation should be adequate to keep the emissions to the atmosphere low. 
     SUMMARY OF THE INVENTION 
     The invention should provide at least one of the features described hereinbefore as desirable and not heretofore provided by the prior art. 
     Specifically, it is an object of this invention to provide substantially all of the advantages described hereinbefore as desirable and not heretofore provided by the prior art. 
     These and other objects will become apparent from the descriptive matter hereinafter, particularly when taken in conjunction with the appended drawings. 
     In accordance with this invention there is provided a cleaning formulation that can be applied to a cloth and employed to wipe a variety of soils from a surface on which other operations are to be performed. 
     In accordance with one embodiment of this invention, such a cleaning formulation is shown by a combination of a major and effective amount; for example, 98-75 percent by volume of a first ingredient comprising propylene glycol methyl ether acetate; and a minor and effective amount; for example, 2 to 25 percent by volume of a second ingredient consisting essentially of methyl isoamyl ketone. 
     An alternative second ingredient is 2 to 20 percent by volume of normal butyl acetate. 
     In accordance with another embodiment of this invention, there is provided a composition that has a less irritating odor than that of the compositions described hereinbefore. This composition comprise up to 50% propylene glycol methyl ether acetate, from 15 to 65% propylene glycol methyl ether, up to 35% isoparaffins and up to 35% normal butyl acetate. 
     In accordance with another embodiment of this invention there is provided a method of disposing of cloths onto which the formulation has been applied which comprises the steps of: 
     1. applying the solvent into the cloth and wiping the surface; 
     2. placing the solvent-laden cloth in a bag designed and constructed of materials to prevent permeation of solvent liquid or vapors through the walls of the bag; 
     3. closing the bag opening, such as tying off the opening with wire or string or sealing closed the opening to prevent loss of solvent liquid or vapors; 
     4. storing the vapor-proof bag and solvent laden cloth in an enclosed collection can; 
     5. storing in covered bins in a lined transfer bag the vapor-proof bags and solvent-laden cloths that have been dumped thereinto; 
     6. compacting the sealed bags containing the solvent-laden cloths into steel or fibre drums; and 
     7. disposing of the compacted sealed bags and contents. 
     As an example, the respective bags may be combustible and the entire bags and solvent-laden cloths burned in an incinerator to produce harmless gaseous emissions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, FIG. 1 represents a prior art collection system. 
     FIG. 2 represents a proposed collection system. 
     FIG. 2a shows respective steps in the proposed collection system in somewhat greater detail. 
     FIG. 2b shows further details of the disposal of the solvent-laden rags. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     It should be borne in mind that this invention may be useful in multiple areas. The specific instance in which it has been employed most zealously has been in the attempts to upgrade the wiping of surfaces for elimination of various &#34;soils&#34; to form light-weight but strong components for making aircraft parts or the like. Accordingly, it is in this environment that this invention will be described most closely hereinafter. 
     In this invention, the chemicals are listed in the Condensed Chemical Dictionary, 11th Ed., Van Nostrand Reinhold, New York, 1987. No statement was found therein of the chemicals of this invention being used as cleaning chemicals. 
     An important consideration in selecting the components in the blend was the volatility, or evaporation rate. If the volatility was too low, the cleaner would not dry off the surface being cleaned. On the other hand, if the volatility was too high, an excessive amount evaporated to the atmosphere, creating atmospheric contamination. The ideal evaporation rate was found to be between 30 and 100 percent of the evaporation rate of n-butyl acetate which is used as a reference to define evaporation rates of liquids. 
     A typical example of a major ingredient is propylene glycol methyl ether acetate, having a structural formula I, C 6  H 12  O 3 , as follows: ##STR1## 
     It is projected that other glycol ethers or glycol ether acetates can be used instead of propylene glycol methyl ether acetate, but such modification would alter the evaporation rate and other critical properties. 
     In this invention, a propylene glycol methyl ether acetate should have a flash point no lower than 116 degrees Fahrenheit if it is desired that the material be nonflammable, or have a flash point above 100 degrees Fahrenheit as measured by the closed cup method. Similarly, the propylene glycol methyl ether should have a flash point no lower than 89 degrees Fahrenheit if compositions of this invention are to be nonflammable, or have a flash point above 100 degrees Fahrenheit as measured by the closed cup method. If the lower flash points can be tolerated, even greater quantities of impurities are acceptable so as to lower the flash point. This is not normally desirable in most of the cleaning applications in which we have tried the formulation of this invention. Care must be taken that any alteration does not exceed the limits set forth in accordance with this formulation; specifically, the flash point of the formulation, if it is to be nonflammable must be 100 degrees Fahrenheit or higher when measured by the closed cup method. 
     It has been found advantageous to have a formulation that has sufficiently low toxicity, reported as Threshold Limit Value-Time Weighted Average toxicity, (TLV-TWA toxicity). This is sometimes variously referred to only as &#34;TLV&#34; or &#34;TWA&#34; (toxicity). It must be low enough to allow eight hours continuous human exposure to at least 100 ppm without ill effects. 
     The Threshold Limit Value-Time Weighted Average (TLV-TWA) is the time-weighted average concentration for a normal eight hour workday and a forty hour workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect. It is expressed in the reference as parts per million (ppm) which is parts of vapor or gas per million parts of contaminated air by volume at 25 degrees C. and 760 torr. 
     The optimum result has been found to be where only about 2 percent by volume of a total amount of the formulation is the second ingredient with the proportion of the first and major ingredient being about 98 percent by volume of the first and second ingredients comprising the formulation. In optimum formulations, our formulation has been found to be able to provide a TLV-TWA toxicity well above 200 parts per million, since the major ingredient has no established TLV toxicity. Even higher TLV toxicity values can be obtained; for example, TLV-TWA value up to about 1000 parts per million. As a consequence, the optimum formulation has extremely low toxicity, or recognized high TLV-TWA toxicity value. 
     Table I hereinafter lists the properties of some typical glycol ethers and glycol ether acetates It can be seen that propylene glycol methyl ether is slightly too flammable since its flash point is only 97 degrees Fahrenheit. 
     On the other hand, ethylene glycol methyl ether is too toxic, since its maximum exposure limit is only 25 ppm. In like manner, ethylene glycol butyl ether is too toxic, since its maximum exposure limit is only 50 ppm. Ethylene glycol ethyl ether, ethylene glycol ethyl ether acetate, and diethylene glycol methyl ether each evaporate too slowly. 
     Herein when the specific chemical is described, the allusion is to that chemical alone without being significantly modified by the presence of other ingredients. 
     
                                           TABLE I__________________________________________________________________________PROPERTIES OF GLYCOL ETHERS AND GLYCOL ETHER ACETATES                                   TLV-TWA            EVAPORATION RATE                         FLAMMABILITY                                   TOXICITY            (based on n-Butyl                         (Flash Pt.,                                   (Max ExposureCOMPOUND         Acetate = 1) Deg. F)   Limit, PPM)__________________________________________________________________________1)  ETHYLENE GLYCOL            0.5          110        25  METHYL ETHER2)  ETHYLENE GLYCOL            0.3          120       100  ETHYL ETHER3)  ETHYLENE GLYCOL            0.2          120       100  ETHYL ETHER ACETATE4)  ETHYLENE GLYCOL            0.06         190        50  BUTYL ETHER5)  DIETHYLENE GLYCOL            0.02         200       NONE ESTABLISHED  METHYL ETHER6)  PROPYLENE GLYCOL            0.7           97       100  METHYL ETHER7)  PROPYLENE GLYCOL            0.4          116       NONE ESTABLISHED  METHYL ETHER  ACETATE__________________________________________________________________________ Deg. = Degrees Pt. = point Max = maximum 
    
     There are several other compounds in this family of chemicals as shown in the Condensed Chemical Dictionary, 11th Ed., but they do not exhibit the optimum chemical and physical properties as does the major ingredient delineated herein. 
     Similarly, other ketones or aliphatic esters could be used instead of the methyl isoamyl ketone or n-butyl acetate but such substitution may alter the evaporation rate, toxicity and flammability. Care must be taken that the alteration is not intolerably great. 
     Table II shows the properties of several ketones and aliphatic esters compared with the ones described in this invention. 
     Herein when the specific chemical is described, the allusion is to that chemical alone without being significantly modified by the presence of other ingredients. 
     
                                           TABLE II__________________________________________________________________________                                TLV-TWA         EVAPORATION RATE                      FLAMMABILITY                                TOXICITY         (based on n-Butyl                      (Flash Pt.,                                (Max ExposureCOMPOUND      Acetate = 1) Deg. F)   Limit, PPM)__________________________________________________________________________  KETONES1)  METHYL ETHYL  KETONE      3.8          24        2002)  METHYL PROPYL  KETONE      2.3          45        2003)  METHYL ISOBUTYL  KETONE      1.6          73        1004)  METHYL HEXYL  KETONE       .1          160       1005)  METHYL ISOAMYL  KETONE      0.5          96        100  ALIPHATIC ESTERS6)  ETHYL ACETATE         4.1          24        2007)  PROPYL ACETATE         2.3          55        2008)  AMYL ACETATE         0.4          101       2009)  N-BUTYL ACETATE         1.0          72        150__________________________________________________________________________ Deg. = Degrees Max 32  maximum Pt. = point 
    
     The methyl ethyl ketone and the methyl propyl ketone have a higher evaporation rate than desired. In addition, they are too flammable in that their flash point is down to about 24 to 45 degrees F. These components would lower the flash point of the formulation to under 100 degrees Fahrenheit. 
     Methyl isobutyl ketone also evaporates too rapidly. Methyl hexyl ketone has too low an evaporation rate. The methyl isoamyl ketone is about the optimum ketone compound. 
     The methyl isoamyl ketone has about the optimum vapor pressure and by virtue of its slow evaporation it is relatively non-toxic. 
     An alternative minor component is n-butyl acetate, an aliphatic ester. This compound was selected from a list of aliphatic esters shown in Table II based on their physical and chemical properties. Ethyl acetate and propyl acetate evaporate too rapidly and their flash points are too low. Amyl acetate has a satisfactory evaporation rate and flash point, but has a strong odor even when diluted to 5 percent by volume. The n-butyl acetate has a relatively low flash point, but it does not lower the flash point of the total formulation to under 100 degrees Fahrenheit when mixed at 5 to 20 percent by volume. 
     An odor masking ingredient is frequently employed. Typical of an odor masking ingredient is a concentration within the range of a trace up to 5.0 percent by volume of d-limonene, a C 10  H 16  cyclic hydrocarbon. 
     Although there are several blends of cleaning formulations on the market, none of these combinations exhibit the efficiency and have the scientific approach employed in this invention. 
     The formulation can clean surfaces in preparation for applying sealants, adhesives, paints and can effectively clean machinery, automobiles, structures such as walls or floors or even the light weight parts for aircraft. It can be used inside buildings and in non-ventilated areas with no danger of fire or toxicity. 
     The formulation can be employed to clean a variety of different kinds of soil such as oils, greases, waxes, uncured resins, dirt, stains, carbon, marking inks, wet paints and others. In this way the surface is made ready for further work as indicated in the preceding paragraph. 
     A formulation with a mild-odor is shown in Table III. 
     
                                           TABLE III__________________________________________________________________________                  OPTIMUM    ALLOWABLE                  CONCENTRATION                             RANGE                  (Percentage)                             (Percentage)__________________________________________________________________________PROPYLENE GLYCOL METHYL                  25          5-35ETHER ACETATEPROPYLENE GLYCOL METHYL                  40         30-60ETHERISOPARAFFINS (ISO-DECANE AND ISO-                  28         10-33UNDECANE IN ANY PROPORTION)NORMAL BUTYL ACETATE    5          2-33D-LIMONENE              2         trace-5__________________________________________________________________________ 
    
     The percentages given herein are percent by volume. 
     The ranges given in Table III have been formulated based on laboratory tests. For example, it has been found that the combined concentrations of propylene glycol methyl acetate and propylene glycol methyl ether must be at least 65 percent in order for the formulation to have a satisfactory cleaning efficiency. At least 5 percent of this total must be propylene glycol methyl ether acetate to reduce the flammability. The concentration of propylene glycol methyl ether acetate is also limited by its odor, 35 percent being the maximum desirable. These findings then set the range of propylene glycol methyl ether acetate at 5 to 35 percent and the range of propylene glycol methyl ether at 30 to 60 percent. In the case of normal butyl acetate, it has been found that at least 2 percent is needed to clean certain types of soils, particularly marking inks. On the other hand if more than 15 percent is added, the flash point is lowered to the point where the formulation becomes too flammable. The isoparaffins, specifically iso-decane and iso-undecane, increase the flash point of the formulation which is desirable. If, on the other hand, 65 percent is the minimum concentration of the two glycol ethers and 2 percent is the minimum concentration of the butyl acetate, the maximum concentration of the isoparaffins becomes 33 percent. The d-limonene is added to improve the odor. If more than 5 percent is added, the citrus odor becomes too strong. 
     Table IV compares the properties of the mild-odor formulations with those of the formulation described in an earlier filed application of which this is a continuation-in-part. Table IV shows that the mild-odor formulation is an efficient cleaner, has a low toxicity, is nonflammable at ambient temperatures up to 91 degrees Fahrenheit, has a low vapor pressure and low evaporation rate to reduce volatile organic compound emissions so it can be used with the wipe cloth management system as described hereinafter in subject invention to further reduce emissions. The mild-odor formulation evaporates from surfaces at ambient conditions leaving no residue. It conforms to government environmental regulations and has a mild, pleasant odor. The new formulation has a wide application in industry where odors associated with formulations such as the strong odors given hereinbefore may be objectionable. 
     
                                           TABLE IV__________________________________________________________________________COMPARISON OF PROPERTIES OFORIGINAL AND NEW FORMULATIONS               Original Formulation               (From Pending Patent)                           New Formulation__________________________________________________________________________Cleaning efficiency Excellent   GoodFlash Point deg. Fahrenheit               110         91-101Toxicity, TLV-TWA (max.               400         150exposure limits)Odor                Strong      MildVapor pressure      4.5         6.4(mm mercury @ 20 degrees C.)Evaporation rate (n-butyl               30          50acetate = 100)Compatible with wipe cloth management               Yes         Yessystem per pending patent)__________________________________________________________________________ 
    
     The new formulations described immediately hereinbefore have certain properties which may make them less desirable than the original formulation; for example, they may be more flammable or more toxic. About 50 percent of the workers may be bothered by the odor of the older formulation. All the original and the new formulations are increasingly in demand as a result of a Clean Air Act passed by Congress in 1990. As indicated hereinbefore, this law curtails the use of some common solvent cleaners such as chloroform, dichloromethane, methyl ethyl ketone, methyl isobutyl ketone, toluene, trichloroethylene, trichloroethane, and xylenes. A formulation which contains none of these curtailed ingredients but which is an efficient cleaner, nonflammable, and has low toxicity and evaporates slowly leaving no residue is desirable. This is particularly true where it has a pleasant odor that will have wide acceptance in the manufacturing industries. Where it is desired to eliminate any problem with flammability, formulations have been developed which contain a higher portion of higher flash point ingredients and a lower portion of low flash point ingredients. For example, propylene glycol methyl ether acetate has a flash point of 117 degrees Fahrenheit. By increasing the concentration of this component to 55 to 75 percent (% by vol.) level as opposed to 25 percent in the flammable formulation, the flash point of the admixture is increased. On the other hand, propylene glycol methyl ether has a flash point as low as 89 degrees (although some batches are as high as 98 degrees). The flash point of the admixture is lower when the concentration of the lower flash point ingredient is kept low. Care must be taken to maintain a combination of the two ingredients mentioned above to at least 65 percent of the total formulation to maintain cleaning efficiency. 
     There are a large number of variations of the formulation available. If too much propylene glycol methyl ether acetate (PMA) is added, the odor becomes too strong. If too little PMA is added, the cleaning efficiency is reduced. If too much propylene glycol methyl ether is added, the flammability is increased. This is frequently intolerable. The proportion of propylene glycol methyl ether must be decreased. If too little propylene glycol methyl ether is included, however, the cleaning efficiency is reduced. If too much isoparaffins are added, the cleaning efficiency is reduced; if too little, the other components must be increased to undesirable levels. N-butyl acetate is included in some of the formulations to help clean certain types of inks and dyes. If too much n-butyl acetate is present the formulation smells too &#34;fruity&#34; and the flash point is reduced. If this is intolerable, then the proportion of n-butyl acetate must be decreased. 
     Further details of the new formulation are shown in Table V. These formulations differ from each other, each having specific advantages. Formulation A is the least flammable and the least toxic and has the lowest vapor pressure and evaporation rate. Formulation B has the mildest odor of the three formulations. Formulation C is the best cleaner, being composed of two components having good cleaning efficiencies. 
     Table VI along with a comparison of the formulations and properties of earlier formulations that we have developed, show the advantages and the industrial applications in terms of cleaning efficiency, flash point, toxicity, odor, vapor pressure, evaporation rate and the like. 
     
                       TABLE V______________________________________NONFLAMMABLE, MODERATE ODORCLEANING FORMULATIONSFormulationsA               B           CAll.        Opt.    All.    Opt.  All.   Opt.Range       Conc.   Range   Conc. Range  Conc.______________________________________IngredientsPropylene   65-75   65      55-75 55    60-75  60GlycolMethylEtherAcetate(PMA)Propylene               5-10  10    25-40  40GlycolMethylEther(PM)Isoparaffins   25-30   30      25-33 33(C11, C12)Butyl   2-5      5      2-5    2Acetate______________________________________ Concentrations are % by volume Conc. = Concentration Opt. = optimum All. = allowable 
    
     
                                           TABLE VI__________________________________________________________________________COMPARISON OF PRIOR AND NEW FORMULATIONS                     New     SERIAL NO.             SERIAL NO.                     Formulations     07/614,228             07/686,180                     A   B   C__________________________________________________________________________INGREDIENTSPropylene 67-98         67-98              5-35   65  55  60GlycolMethylEtherAcetate(PMA)Propylene         30-60       10  40GlycolMethylEther (PM)Isoparaffins      10-33   30  33             (C10,   (C11,                         (C11,             C11)    C12)                         C12)Butyl      2-33   2-33     5   2AcetateMethyl         2-33IsoamylKetoned-Limonene     0-5 0-5PROPERTIESCleaning Efficiency     Excell  Good    Good                         Good                             ExcellFlash Point Degrees     110 112  91     105 101 101FahrenheitToxicity, TLV-     400 400 150     300 200 150TWAOdor      Strong         Strong             Mild    Mod.                         Mod.                             Mod.Vapor Pressure     5.0 4.3 6.4     3.5 4.0 6.6mm HgEvaporation rate     30  30  50      28  29  46(butyl acetate= 100)Evaporate at     Yes Yes Yes     Yes Yes YesAmbient Temp.Residue after     None         None             None    None                         None                             NoneEvaporationCurtailed Chemicals     None         None             None    None                         None                             NoneUse with Wipe-     Yes     Yes     Yes Yes YesCloth ManagementSystem__________________________________________________________________________ *Concentrations are shown as % by volume Isoparaffins are isoform Mod. = Moderate Excell  Excellent 
    
     An improved series of mild-odor formulations have been developed for facilities which are able to use flammable solvents and which prefer a mild-odor. These formulations (Tables VII, IX, and X) are similar to those shown in Table III. The differences are a wider allowable range of some of the components and elimination of d-limonene. D-limonene has been eliminated because it is not necessary to improve the odor and it has been found that d-limonene is very slow to evaporate and may leave a residue. 
     
                       TABLE VII______________________________________Compositions of New Mild-Odor Formulations        ALLOW-   OPTIMUM        ABLE     CONCENTRATION        RANGE    (Percent By        (Percent By                 Volume)        Volume)  (A)       (B)______________________________________PROPYLENE GLYCOL          0-50       25METHYL ETHERACETATEPROPYLENE GLYCOL          15-65      40        65METHYL ETHERISOPARAFFINS (ISO-          0-35       30        30DECANE AND ISO-UNDECANE IN ANYPROPORTION)NORMAL BUTYL   0-35        5         5ACETATE______________________________________ 
    
     The ranges given in Table VII have been formulated based on laboratory tests. For example, it has been found that the combined concentrations of propylene glycol methyl ether acetate and propylene glycol methyl ether must be at least 65% in order for the formulation to have a satisfactory cleaning efficiency. Concentrations of propylene glycol methyl ether acetate over 50% have a strong odor. Therefore, since the maximum concentration of propylene glycol methyl ether acetate is 50% and the minimum combined concentration of propylene glycol methyl ether acetate and propylene glycol methyl ether is 65%, then the minimum concentration of propylene glycol methyl ether must be 15%. Furthermore, concentrations of propylene glycol methyl ether over 65% would result in a blend with a TLV-TWA of less than 150. Isoparaffins up to 35% may be added to provide a more desirable higher TLV-TWA. Normal butyl acetate has been found to be an efficient cleaner for certain dyes and inks; therefore concentrations up to 35% may be included. 
     Table VIII shows the properties of the new mild-odor formulations. Even though the TLV&#39;s are the same formulation (A) is less toxic by inhalation than formulation (B) because of the lower vapor pressure. It is also slightly less flammable. Formulation (B) has a milder odor than (A) due to the absence of propylene glycol methyl ether acetate. Formulation (B) is also faster drying. Both of these formulations are efficient cleaners, have low toxicities, mild odors, and low evaporation rates to reduce volatile organic compound emissions. The new mild-odor formulations evaporate from surfaces at ambient conditions leaving no residue and they conform to government environmental regulations. Although the new formulations are flammable, they have a wide application in industry where odors associated with formulations, given hereinbefore, may be more irritating. 
     
                       TABLE VIII______________________________________PROPERTIES OF NEW FORMULATIONS                     (A)     (B)______________________________________Cleaning efficiency       good    goodFlash point, F.           92      90Toxicity, TLV-TWA         150     150(max. exposure limit)Odor                      mild    mildVapor pressure            6.4     8.0(mm mercury at 20 C.)Evaporation rate          50      60(n-butyl acetate = 100)______________________________________ 
    
     
                       TABLE IX______________________________________COMPONENTS         PERCENT BY VOLUME______________________________________Propylene Glycol   40Methyl Ether AcetatePropylene Glycol   25Methyl EtherIsoparaffins (Iso-decane &amp;              30Iso-undecane in any proportion)Normal Butyl Acetate               5______________________________________ 
    
     
                       TABLE X______________________________________COMPONENTS         PERCENT BY VOLUME______________________________________Propylene Glycol   45Methyl Ether AcetatePropylene Glycol   20Methyl EtherIsoparaffins (Iso decane &amp;              30Iso-undecane in any proportion)Normal Butyl Acetate               5______________________________________ 
    
     The formulations of Tables IX and X include propylene glycol methyl ether acetate above 35% and up to about 50% by volume. These formulations will have excellent cleaning abilities and have relatively mild odors, but both will be flammable blends. The formulation of Table X will have a slightly stronger odor than formulation of Table IX. The formulation of Table IX will have a slightly stronger odor than the 35% Propylene Glycol Methyl Ether Acetate blend. The formulation of Table X will have a higher flash point (estimated at 95° F.) than the formulation of Table IX, but still under 100° F. For some facilities, the higher flash point may be desired. The formulation of Table IX has a higher flash point than the 35% Propylene Glycol Methyl Ether Acetate blend. There is no increase in toxicity for these two blends over the 35% Propylene Glycol Methyl Ether Acetate blend. The formulations of Table IX and X do not have hazardous air pollutants. 
     Another aspect of this invention is the use of vapor-proof bags to store the solvent-laden cloths to prevent the emission of volatile organic compounds to the atmosphere. Several types of materials to form the bags were evaluated for this application, including metal foils, various plastics, and materials combined as coextruded multi-layer films. To conduct these evaluations, normal butyl acetate was applied to wipe-cloths which were then placed in a bag constructed of the material being evaluated. The bag opening was tied closed and the bag weighed. The bag was then reweighed after various time periods to determine the solvent loss. The solvent loss using various bagging materials is shown in Table XI. It is seen that metal foils such as 2 mil aluminum effectively prevented permeation of solvent vapors, but the foils tore easily and were difficult to seal into bags. Single layer plastics such as polyethylene, polypropylene and polyolefins had high solvent losses, even with wall thicknesses up to 10 mils. The best results were obtained with multi-layered materials, particularly those having metal foil as one of the layers. A bag constructed of 0.3 mil of aluminum foil in the center with 1.0 to 1.5 mil layers of polyethylene coextruded and bonded to the aluminum foil on each side lost less than 0.1% of the solvent in a 24 hour period. This bag was also tear resistant and its opening was easy to tie closed. Another coextruded material consisting of multi-layers of polyethylene, polypropylene, and vinyl alcohol (bonded together) was also effective, having a loss of 0.3% of the solvent in 24 hours. The aluminized polyethylene bag was preferred, however, because of its low solvent loss, ease of handling, and lower cost. It was found that the most effective means of sealing the bag closed was by twisting the top of the bag and sealing with wire ties or string. It must be cautioned that staples are not to be used to close the bag because the staples create holes through which solvent vapors will escape. 
     
                       TABLE XI______________________________________EFFICIENCY OF BAGGING MATERIAL TOPREVENT SOLVENT PERMEATION            Solvent LossMaterial         (% in 24 hrs)                       Strength______________________________________4.6 mil Polyethylene            12.1       Tear resistant10 mil Polyethylene            11.0       Tear resistant1.1 mil Polyolefin            7.2        Tear resistant4 mil Polypropylene            2.9        Tear resistant2 mil Aluminum   &lt;0.1       Tears easily2 mil Aluminum, Poly-            &lt;0.1       Tear resistantethylene coextrusion2 mil Polypropylene,            0.3        Tear resistantPolyethylene, Vinylalcohol coextrusion______________________________________ 
    
     Although vapor-proof bags have been used to store certain food products such as potato chips, their use for storing used solvent-laden wipe cloths is not known to the inventors. It is also a novel procedure to enclose used wipe cloths in vapor-proof bags. Using existent procedures, the used wipe cloths are either left open to the atmosphere now or placed in containers that do not effectively prevent volatile emissions. This embodiment of this invention prevents such volatile emissions. 
     Specifically, the method of this invention provides a vapor-proof enclosure for storage, eliminates the bulk of cloth filled bags for handling transfer to the incinerator and reduces the cost of transportation and disposal of the cloths. In fact, the combination of the formulation and the method of this invention results in a reduction of the volatile organic emissions in the range of 60 to 96 percent as compared with existing, or prior art, procedures. This invention also overcomes the disadvantages of the carbon absorption system, since the cleaning operation can be performed anywhere in the facility rather than being limited to rooms equipped with a carbon absorption system. In addition, the efficiency of the invention reduces the emissions to 4 to 40 percent of the prior art emissions. Initial costs and maintenance costs are also reduced. 
     Referring to FIG. 1, there is illustrated a diagram of the prior art type of approach in which the wipe-solvent soaked cloth 11 is placed in respective small 13 or large 15 storage containers; or collection cans 17. After that they are transferred to covered, two cubic yard bins 19 and then dumped in a 30 foot roll top hopper 21 that may be used to transport them to an incinerator or landfill. By way of contrast, the proposed collection system of FIGS. 2 and 2b show the solvent-laden cloths 11 being sealed in vapor-proof bags 23, collected in collection cans 25, and stored in 2 cubic yard bins 27, each lined with a transfer bag 29 having an opening 29a for receiving the bags 23. The transfer bag is then used to carry the bags to a compactor 31, which compacts the sealed bags into steel or fibre drums 33. The compacted material is then burned in an incinerator or cement kiln. 
     The specific steps are illustrated in more detail in FIG. 2a. Therein, the formulation is applied from a container 41 onto a cloth 11. Thereafter, the cloth 11 is employed for wiping of a workpiece 12. Suitable gloves 44 can be employed if desired. As illustrated further in FIGS. 2a or 2b, the respective cloth 11 can be placed in a stand alone vapor-proof bag 23 or in a rag can 45 which is lined with a vapor-proof bag 23. The vapor-proof bags 23 are then tied, as by a tie 47, FIG. 2a, to prevent emissions. 
     As shown in FIG. 2b, the sealed bags 23 containing the solvent-laden cloths 11 may be collected in 5 to 30 gallon collection cans 25. The bags are then stored in 2 cubic yard covered bins 27 which are lined with a transfer bag 29. The transfer bag 29 is employed to carry the sealed bags 23 to compactor 31, where the sealed bags 23 containing the solvent-laden cloths 11 are compacted into steel or fibre drums 33. The drums 33 are equipped with gaskets to prevent leakage of vapors. The drums are then sent to the incinerator or kiln for burning. 
     It is helpful to look at a detailed description. Referring to FIG. 1, a cleaner was employed in the old system and can be improved by the formulation of this invention. Specifically, a wiping operation can be employed using the formulation of this invention on clean wipe cloths stored in vapor-proof bags. 
     The sealed bags 23 are collected in the collection cans 25, transferred periodically to a storage bin 27 and then compacted into steel or fibre drums 33 by the compactor 31. The steel or fiber drums may be sealed by a gasketed lid and the assembly is designed to prevent escape of vapors and volatile emissions. The drums can be subsequently buried or incinerated the latter process of which converts the drums and contents to harmless combustion products. 
     As described herein the minimum air polluting wipe-solvent cleaning system is a significant improvement over the prior art type cleaning systems. Specifically, the complete system is a unique solvent formulation and wipecloth handling system having bags of unique design and materials to accomplish the purpose of providing effective cleaning but with a minimum of harmful emissions to the atmosphere. Proper use of these materials result in only 4 to 40 percent of the volatile emissions that have occurred heretofore in the prior art. 
     Specifically, the composition and processes described herein have relatively large commercial application and can be employed in a wide variety of industries. 
     The method of the solvent-laden cloth and bag disposal process can be employed with substantially any formulation. In particular, the formulation disclosed herein is liquid and can be employed in the method of this invention without substantial modification. 
     Although this invention has been described with a certain degree of particularity, it is understood that the present disclosure is made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention, reference being had for the latter purpose to the appended claims.