US 2951043 A
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Unite States Paten CLEANER FOR PAINT APPLICATORS Robert E. Blank, Mayfield Heights, Ohio, assignor to The Sherwin-Williams Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Filed Sept. 9, 1954, Ser. No. 455,067
2 Claims. (Cl. 252-171) This invention relates to cleaning compositions for removing wet and partially dried paint from paint applicators and for softening brushes which have become hardened with dried paint. Thus these cleaners are useful in cleaning spray guns, brushes and paint rollers to remove undried or partially dried paint and for softening paint which has hardened in the paint applicator.
Like many things, painting is enjoyable to most people until it is necessary to clean up after the job is done. So distasteful is this phase in some cases that it is conveniently postponed until later, by which time the paintapplying tool, usually the brush, has the consistency of concrete. While it would be most desirable to eliminate the clean-up entirely, at this stage in the development of painting, facilitation of this phase is the most that can be accomplished.
Much has been done in the field of emulsion paints, for example, to aid the painter. Emulsion paints are readily washed out under the tap and tools for applying such paints are easily restored after use without more than tolerable discomfiture. The oil base or synthetic drying oil base paints have been more diflicult to bring to this high order of development and the replacement rate is high for paint applicators used with these materials.
It is a principal object of this invention to provide a composition useful in cleaning paint applicators.
Another object of this invention is to provide a paint applicator cleaning material which so combines with the wet or partially dried paint that the resulting mixture is readily removed from the applicator in a stream of water.
Another object of this invention is to provide a paint applicator cleaning composition which is useful in softening dried paint contained in paint applicators. The compositions of this invention will not ordinarily dissolve dried paint, but in most cases, these compositions find utility in softening dried paint, for example, as may be contained in a paint brush, which will enable the brush to be at least partially cleaned with a comb or wire brush.
Other objects of this invention appear as the description proceeds.
To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the appended claims, the following description setting forth in detail certain illustrative embodiments of the invention, such disclosed means constituting, however, but a few of the various forms in which the principle of this invention may be employed.
It has been found that a highly useful cleaning composition can be produced by admixing a normally liquid hydrocarbon, certain organic esters of phosphoric acid, a monoalkyl ether of an alkylene glycol, and a pair of non-ionic surfactants which while possessing similar chemical structure differ in their relative attraction for water and for fatty materials. Many of the cleaning composi- 2,951,043 Patented Aug. 30,1960
tions heretofore used for similar purposes have contained a single non-ionic surfactant and the compositions of the present invention are distinguished over and represent a major improvement over such prior compositions in this respect.
Cleaning compositions of the type in question are subjected to two distinct phases where the ultimate removal means is water or an aqueous medium. The contaminated brush, i.e., one which has been used to apply paint within the last few days, is usually immersed in the cleaning solution and agitated therein. This action results in the cleaning solution becoming contaminated with paint ingredients and alters the physical characteristics of the resulting mixture.
The brush which is now wet with paint ingredients plus the cleaning solution is exposed either to a stream or a container of water and again agitated. Thus the paint-cleaner system is now subjected to an entirely different physical environment and must be capable of accommodating this condition. While many cleaners have been able to survive with some satisfaction this much of an operation, the difliculty has occurred when the brush incompletely cleaned and wet with water is sought to be further cleaned in the same composition or fresh cleaner. In the presence of water most prior cleaners tend to acquire the characteristics of shaving cream and become quite ineffective for washing paint from an applicator device.
The compositions of the present invention in the provision of a plurality of non-ionic surfactants of different dispersion medium characteristics obviate this principal difficulty with compositions heretofore available.
Broadly stated, therefore, this invention comprises a composition of matter comprising an admixture of:
(a) A normally liquid hydrocarbon.
ll nlo-r-o R,
wherein R and R are each selected from the group consisting of aliphatic and aromatic radicals, and R is selected from the group consisting of hydrogen, aliphatic and aromatic radicals.
(c) A monalkyl ether of an alky-lene glycol.
(d) A hydrophilic non-ionic compound selected from the group consisting of organic esters of polyglycols and organic ethers of polyglycols; and
(e) A lipophilic non-ionic compound selected from the group consisting of organic esters of polyglycols and organic ethers of polyglycols.
Under ordinary circumstances, the compositions of the present invention are clear, colorless, homogeneous liquids. Homogeneity and clarity of solution are obtained when the components are admixed in proper proportions. While it is desirable to obtain cleaning solu tions which are clear and homogeneous, clarity and homogeneity are not essential to the effective operation of the composition as a cleaning agent for paint-applying tools. Different proportions from those hereinafter indicated will in many cases result in non-homogeneity and a cloudy appearance. Such compositions are, nevertheless, useful for the purposes herein stated.
In the preferred compositions, i.e., those which are homogeneous, clear solutions, the major component is a normally liquid hydrocarbon. Experience has shown that the hydrocarbon phase of these compositions may be aliphatic, aromatic, cycloaliphatic or mixed, aliphaticaromatic. Commercially available mixtures, e.g., min- 3 eral spirits, petroleum ether, VM & -P naphtha and other such petroleum distillates may be used. However, if economics is not a primary consideration of the formulator, hydrocarbons of a higher degree of purity may be used. Included among such materials are hexane, heptane, octane, decane, dodeeane, cyc'lohexane, cyclohexene, methyl cyclohexane, alpha pinene, beta pinene, turpentine, styrene, alpha methyl styrene, vinyl toluene, and the normal aromatic hydrocarbon solvents such as benzene, toluene and xylene. The pure compounds as such may be used or mixtures of such pure compounds may be used. However, as indicated above, for satisfactory and economic formulation, the commercially available hydrocarbon mixtures, e.g., mineral spirits, are generally employed.
The second essential component of the present compositions is an organic ester of phosphoric acid. One of the desirable characteristics of the compositions of this invention is their substantial neutrality. The advantages of neutral compositions are manifest, particularly from the standpoints of packaging and handling in manufacture as well as ultimate use. Thus, for most purposes, the dry esters of phosphoric acid are indicated because of their obvious neutrality. However, it has been found that the diesters of phosphoric esters may also be employed since the third hydrogen atom under the conditions encountered is so tightly bound as to have virtually no effect upon the neutrality of the composition. Thus, the diand triorganic esters of phosphoric acid are of particular utility in these compositions.
The efiectiveness of phosphate esters as solvents for dried and partially dried paint films is well known and this property of phosphates is utilized in the present compositions. Apparently the etfectiveness of the phosphate esters as solvents for pain-ts is'attributable to the phosphate radical rather than to the organic portion, the organic portion having primarily utility in improving the solubility of the phosphate in the medium in which it is carried prior to contact with the paint. Hence, in the present case, there is little of critical nature to be attributed to the organic portion of the molecule except insofar as solubility in the hydrocarbon medium may be involved. Most phosphate esters are soluble in aliphatic hydrocarbons as well as aromatic hydrocarbons without too much difficulty up to the limit of their solubility. The limits of solubility cover, for most practical purposes, concentrations which will normally be encountered. Thus, the organic portion of the phosphate esters may be aliphatic, aromatic, alkylaryl, cycloaliphatic or mixed aliphatic, aromatic, and/ or cyclo-aliphatic. useful'in accordance formula:
herewith have the following general ll R o-P 011;
Ra wherein R and R are each selected from the group consisting of aliphatic and aromatic radicals, and R is selected from the group consisting of hydrogen, aliphatic radicals and aromatic radicals.
Specific examples of phosphate esters useful in accord ance with this invention include, therefore, tri-phenyl phosphate, tri-cresyl phosphate, tri-(t-butyl phenyl) phosphate, tri-ethyl phosphate, tri-isopropyl phosphate, tri-nbutyl phosphate, tri-amyl phosphate, tri-capryl phosphate, tri-lauryl phosphate, tri-(p-chlorophenyl) phosphate, tricyclohexyl phosphate, tri-methyl cyclohexyl phosphate, di-cresyl phosphate, monobutyl dicresyl phosphate, monooctyl diphenyl phosphate, diphenyl phosphate, di-Z-ethyl hexyl phosphate, di-capryl phosphate, di-lauryl phosphate, di-ethyl phosphate, di-cyclohexyl phosphate, di-(paramethoxy phenyl) phosphate, etc. Halogen, alkoxy, nitro, etc. substituent groups may replace one or more hydrogen atoms in the organic radicals forming a part of the In general, then, the phosphate esters compounds above listed. The presence of such substituent groups whether organic or inorganic does not adversely affect the compositions of this invention and, in fact, may in some cases be quite beneficial. The power of the nitro group as a solvent factor is notable and the greater wetting properties of the metal sulphonate radical is advantageous in the high molecular weight phosphates where solubility in the hydrocarbon phase can be maintained.
The third essential component of the composition of this invention is as indicated above a rnonoalkyl ether of an alkylene glycol. The solvency characteristics of these compositions are attributable mainly to the presence of an ether of an alkylene glycol. These are commercially available under the trade name Cellosolve. Specific examples of monoalkyl ethers of alkylene glycols including the mono-methyl, mono-ethyl, mono-propyl, monoisopropyl, mono-butyl, mono-t-butyl, mono-octyl, etc. ethers of alkylene glycols such as ethylene glycol, trimethylene glycol, tetramethylene glycol, and the like.
This ingredient in combination with the phosphate provides a quite powerful solvent medium for wet and partially dried paint films and also a softening composition for dried paint. It also appears that the mono-alkyl ether of an alkylene glycol component aids in imparting homogeneity to the overall composition by acting as a solubilizing agent for the several normally incompatible ingredients.
The fourth and fifth essential ingredients of these compositions are physically separate and distinct but because they possess chemical similarity are conveniently discussed together. The compositions of the present invention are characterized by the presence therein of one agent of this chemical class which has hydrophilic characteristics and a second agent of this chemical class which has lipophilic characteristics.
Chemically the fourth and fifth ingredients of these compositions may be described as organic esters or ethers of polyglycols. If the basic polyglycol nucleus is considered, the general formula may be represented as follows:
wherein n is 2 or 3 and x is from 2 to 33 or more. At least one of the terminal hydrogen atoms in the polyglycol nucleus must be replaced with an organic radical. The convenient means of replacing hydrogen in a glycol is through etherification or estcrificati on and hence the organic radical R may be the organic residue of a phenol or an alcohol or it maybe the organic residue of an organic carboxylic acid. While it is not essential for the purposes of this invention, the remaining terminal hydrogen atom may also be replaced with such an organic residue, which organic residue may be the same as or different from the organic residue which is required as a replacement for the first terminal hydrogen atom. By organic residue is meant the remainder of an alcohol, phenol or carboxylic acid upon removal of an hydroxyl group. This is, of course, a consideration of these compounds apart from methods of synthesizing them. Assuming that the organic radical R is, then, selected from the group consisting of radicals having the formula R and R" may then be identified as any organic radical in which the free or reactive bondis directly attached to a carbon atom. R maybe aliphatic, c'yclo-aliphatic or aromatic. For most purposes, R is conveniently alkyl, cyclo-alkyl, aryl or aralkyl. While economics and convenience dictate the use of organic radicals R which are composed of carbon and hydrogen only, such products being commercially available, this is not tosay that the presence of substituent groups in these organic radicals will in any way alter the manner in which these compositions performg if reasonable selection of such substituentgroups is made. For example, the inertness of the alkoxy constituent group is well known and it can be expected, then, that the replacement of a hydrogen atom in one of the organic radicals R by an alkoxy group such as methoxy will have no marked influence upon the functioning of the polyglycol ether or ester. The substituent group hydroxyl may also be used as a replacement for one or more of the hydrogen atoms in the normally available organic radicals -R when, for example, one is seeking to introduce hydrophilic characteristics as opposed to lipophilic characteris'tics. Halogen atoms in replacement of one or more of the hydrogen atoms in the organic radicals R may also appear, provided, of course, the replacement is not such as to vastly alter the chemical characteristics of the resultant compound. For example, replacement of hydrogen atoms on an aromatic ring by chlorine, bromine, or fluorine yields a very stable compound which has somewhat improved solubilizing characteristics, but so far as influencing the balance of the polyglycol composition, it has little or no influence. The presence of carbonyl groups in the radicals R in some cases will improve the solvency properties of the resulting compound. Thus it can be seen that if reasonable selection of substituent groups is made and the introduction of obviously inoperative or harmful groups avoided, it is not necessary that the nature of the organic radical R should be restricted to carbon and hydrogen-containing radicals.
R may then be an aliphatic radical such as the alkyl radicals methyl, ethyl, propyl, butyl and amyl; omegachloroamyl, 2-ethyl hexyl, cycloaliphatic radicals, e.g., cyclohexyl, methyl cyclohexyl; capryl, lauryl, oleyl, aralkyl radicals, e.g., phenyl ethyl, parachlorophenyl ethyl, tertiary butyl phenyl ethyl, alkaryl radicals, e.g., tertiary Butyl "phenyl, cresyl, naphthyl, xylyl, p-chlorophenyl, ricinoleyl, stearyl and the organic residues of such vegetable oil fatty acids as linseed oil fatty acids, tung oil fatty acids, soy bean oil fatty acids, etc. Either one or both of the hydrogen atoms in the polyglycol nucleus above may be replaced with one, the same, or different organic radicals such as those mentioned above. Other such organic radicals will become immediately apparent to those skilled in the art.
T The chemical nature of the fourth and fifth ingredients is, therefore, as described above and as will be further exemplified in the specific examples to follow. While the chemical nature of the compounds of the fourth and fifth ingredients is important, the truly critical consideration with respect to these compounds is the difference in their physical afiinity for an aqueous or a fatty dispersion medium. In the previous paragraphs little was said with respect to the chemical feature, namely the value of x representing the number of alkylene oxide polymer units. When the number of alkylene oxide polymer units is low, ire; 'x is from 2 to 7, the resulting compound tends to be hydrophobic and lipophilic. When the number of alkylene oxide units is more than 7 and as high as 30 or more, the compound tends to be hydrophilic and lipophobic. The ultimate physical property of the compound will depend not only upon the magnitude of x but also upon the number and nature of organic radicals such as replacement for the hydrogen atoms of the terminal hydroxy groups. A short chained aliphatic group and particularly a short chained aliphatic group characterized by the presence therein of a hydroxyl substituent group as a replacement for one or both of the terminal hydrogen atoms where x from 2 to 7 will virtually insure water solubility of the resulting compound. This compound will be hydrophilic and lipophobic. The replacement of one of the terminal hydrogen atoms by a phenyl group where x is between 2 and 7 will yield a compound which is definitely hydrophilic, but the aromatic group in the presence of an aromatic solvent would confer a tendency on the part of the compound toward solubility or miscibility with such solvent. Thus, it is possible to alter the hydrophobichydrophilic characteristics by varying the magnitude of d the polyglycol polymer or by the introduction of hydr6= philic or hydrophobic groups into the molecule of. the surfactant. Examples of both modes of variation of the physical characteristics of the fourth and fifth essential ingredients of these compositions are given in the specific examples which follow.
The relative amounts of the two surfactants of different physical characteristics appears to be controlled only by economic considerations. Both must be present and the ratio of one surfactant to the other may vary widely although a practical range includes a ratio of 5 parts of the lipophilic to 1 part of the hydrophilic surfactant all the way to the reverse situation of 1 part of the lipophilic surfactant to 5 parts of the hydrophilic surfactant. Ordinarily within this range of concentration homogeneity of the solution is not destroyed by an imbalance between these two components. If one cares nothing for the physical appearance of the cleaning solution, the hydrophilic and lipophilic surfactants may be admixed in random proportions. Since these two compounds possess similar chemical structure, one serves as a solubilizing medium for the other. If there is an over-abundance of the hydrophilic compound present in these compositions, the solubilizing power of the lipophilic surfactant will be insufiicient to bring all of the hydrophilic surfactant into homogeneous solution and the balance will appear as a cloud producing dispersion or even as a separate liquid layer in the composition. In other words, a given amount of a lipophilic surfactant will dissolve and will also solubilize into the balance of the composition only a certain amount of the hydrophilic surfactant. The relative power of these two ingredients to mix and form homogeneous solutions is. indeed complex and depends to a large extent on the chemical construction of the constituent radicals and the degree of polymerization of the polyglycol. N evertheless, the adjustment to tolerable ratios within the cleaning solution itself assuming significant quantities of each and a proper solvent blend is such that there is always provided a satisfactory balance between the hydrophobichydrophilic (lipophobic-lipophilic) ingredients. It should be borne in mind, however, that operability and saleability or appearance are not necessarily interdependent. The compositions which appear in the specific examples to follow illustrate both clear, homogeneous solutions and heterogeneous admixtures, both such examples possessing satisfactory cleaning properties in accordance with this invention.
The following specific examples will serve to illus-v trate the mode of compounding these compositions, it being understood that such examples are for illustrative purposes only and are not intended to limit the scope of Hydrophilic alkyl-phenyl polyglycol ether (No. 2)-- 2 Example II Petroleum naphtha 18 Tri-t-butyl phosphate 1 0 Monoethyl ether of ethylene glycol 2 Butyl phenyl polyglycol ether (No. 1) 2 Butyl phenyl polyglycol ether (No. 2) u 2 Example III Mineral spirits 18 Triphenyl phosphate 2 Monobutyl ether of ethylene glycol 2 Capryl-phenyl polyglycol ether (No. 1) 1.5
Capryl-phenyl polyglycol ether (No. 2) 1.5
Example IV Mineral spirits -r is Tri-(Z-ethyl hexyl) phosphate 2 Monoethyl ether of ethylene glycol- 2 Isop'ropyl-phenyl polyglycol other (No. 1) 1 n-Octyl-phenyl polyglycol ether (No. 2) 2 Example V Turpentine 1O Dioctyl' phosphate 2 Monobutyl ether of ethylene glycol 2 Cresyl polyglycol other (No. 1) 2 Cresyl polyglycol ether (No. 2) 2 Example VI Minern' spirits -9 di-(Methylcyclohexyl) phosphate 1.3 Mono-ethyl ether of trimethylene glycol 3 Oleyl phenyl polyglycol' ether (No. 1) 1 Butyl phenyl polyglycol ether (No. 2) 1 Example VII Hexane 20' Dilauryl phosphate 3 Monoethyl ether of tetramethylene glycol 2 Phenyl polyglycol ether (No. 1) S Pheiiyl polyglycol ether (No. 2) 1 Example VIII Heptane 20 Mono-octyl diphenyl phosphate 3 Mono-ethyl ether of ethylene glycol 2 Di-phenyl polyglycol ether (No. 2) 2 The di-acetic acid ester of polyglycol (No. 2) 1 Example IX Mineral spirits 18 Butyl di-cresyl phosphate 2 Mono ethyl ether of ethylene glycol 2 t-Butyl phenyl polyglycol ether (No. 1) 1.5 t-Butyl phenyl polyglycol ether (No. 2) 1.5
The foregoing examples are examples of clear, homogeneous compositions all of which exhibit very satisfactory characteristics with respect to cleaning paint-applying implements and Washing out under a stream of tap water. As has been indicated herein, the fact that the composition may not be homogeneous does not necessarily influence its utility as a cleaning composition. For example, random admixtures of the several ingredients were made and as was expected, non-homogeneous compositions were obtained. The following example shows such a composition.
This latter composition is stable as an admixture and while it will clean brushes, there seems to be a little deficiency in the amount of hydrophilic ingredient making it somewhat difiicult to remove the paint-cleaner composition with water. This composition also has a tendency to thicken up when the concentration of paint ingredientsbecomes fairly high.
Example XII v Parts by volume Tr'i-cresyl phosphate 8 Monomethyl ether of ethylene glycol" 8 Tertiary butyl phenyl polyglycol ether (No. l) 6 Tertiary butyl phenyl polyglycol ether (No. 2) 6 It will be observed that this composition contains hydrocarbon ingredient. The composition is he ogeneous and clear and it works quite well as a paint imple ment cleaning solution. This shows that the role ofthe hydrocarbon component is that of a diluent rather a solvent and the hydrocarbon component is used s a practical means of producing a solution which is a6": nomical.
Another factor of these compositions which should observed is that those compositions which are" horn geneous, clear solutions at ordinary temperatures In y show tendency to break and become discontinuous at reduced temperatures, i.e., 10 F. p A
In the above examples, the organic polyglycol ethers and esters are referred to as No; l and No. 2f. polyglycol esters and ethers of type No. 1 are having from about 2 to about 7 alkylene oxide and from this structural consideration tend to liy phobic or lipophilic Examples of such polyglycol esters, or ethers of type No. 1 include the hydrophobic, phenyl polyglycol ethers, e.g., t-butyl phenyl polyethylene glycol ether (2-7 ethylene oxide groups), capryl-phenyl polyethylene glycol ether (2-7 ethylene oxide groups), isopropyl-phenyl polyethylene glycol ether (S ethyIen o'x-ide groups), cresyl polyethylene glycol ether (2-7 ethylene oxide groups), etc. I I
The polyglycol esters and others of type No. 2" are those having more than 7 alkylene oxide groups in "I molecule and these from the standpoint of chemical ture tend to be hydrophilic in nature. Specificj exani ples of type No. 2 include t-butyl phenyl polyethylene" glycol ether (15 or more ethylene oxide groups): phe y l" polyethylene glycol ether (approximately 20' etliyle'iie oxide groups), octyl phenyl polyethylene glycoLethr' (approximately 30 ethylene oxide groups), cresoyl poly ethylene glycol ester (approximately 25 ethyleneoxide' groups). As indicated above, proportions of ingredihts. beyond their significant presence arenot important; If it is desired, however, to produce a clear, homogeneo composition of matter which because of its olarit homogeneity is a more saleable product, then in' general the 'novel'cleaning fluids of this invention will possess" a formulation substantially as follows:
Parts by Hydrocarbon solvent 91030 Organic dior tri-phosphate ester 1fto3j Monoalkyl ether of an alkylene glycol Up'to 2 Hydrophobic-lipophilic polyglycol ether or ester having the formula n 2n )x n 2n wherein n is 2-4, x is 2 to 7 and R is anorganic radical and R" is selected from hydrogen" and organic radicals Hydrophilic polyglycol ether or ester havingthe formula RO-(C H O-) -C H Q where the characters have the same significance as'in the general formula immediately above H 1 and y is an integer from 8 to 30 [to 5' The compositions of this invention have, in general, a; specific gravity at 75 F. in the range of from abo t 0.70 to about 0.90. The percentage of non-volatilqmatter (NVM) ranges from about 7% up to about 50%, and the composition is substantially neutral, i.e.,-;=hasa pH of ab'out'7. There has been provided, therefore, a low odor, non-caustic emulsifiable brush, roller, orspray gun cleaner. The composition contains no inorganic salts and can 'be produced as a clear, homogeneous liquid. using-these cleaning solutions, the implement wet with paint is thoroughly saturated with a supply of the cleaner. The paint-cleaner combination on the implement readily emulsifies with a large quantity of water flowing from a tap and the implement may thus be rinsed clean with water. The remaining paint-cleaner combination in the container remains as a liquid, i.e., does not assume the properties of shaving cream and is still eifective as a cleaning composition after repeated use. If paint has become hardened on the paint applying tool, as, for example, a tool allowed to dry for a week or more, immersion in the cleaning solution for a period of time will soften the paint and enable its removal with a wire brush or other such instrument to mechanically dislodge the paint.
Other ingredients may be included in these compositions, for example, aliphatic alcohols, e.g., cyclohexyl alcohol, capryl alcohol, lauryl alcohol, to aid in solubilizing the various ingredients in the hydrocarbon base. Rust inhibitors, high powered organic solvents, e.g., acetone, dioxane, etc. may also be included without impairment of the cleaning power of the base composition.
Other modes of applying the principle of this invention may be employed instead of those specifically set forth above, changes being made as regards the details herein disclosed, provided the elements set forth in any of the following claims, or the equivalent of such be employed.
It is, therefore, particularly pointed out and distinctly claimed as the invention:
1. A cleaning composition for paint applicators comprising a clear, homogeneous admixture of (a) from 9 to 20 parts by volume of a normally liquid hydrocarbon.
(b) from 1 to 3 parts by volume of an organic phosphate ester having the general formula:
wherein R and R are each selected from the group consisting of aliphatic and aromatic radicals, and R is selected from the group consisting of hydrogen, aliphatic and aromatic radicals (0) 2 parts by volume of a rnonoalkyl ether of a polymethylene glycol, containing from 2 to 4 methylene groups (d) from about 1 to about 5 parts by volume of a hydrophilic, non-ionic compound selected from the group consisting of organic esters of polyglycols and organic ethers of polyglycol; and
(e) from 1 to about 5 parts of volume of a lipophilic,
non-ionic compound selected from the group consisting of organic esters of polyglycols and organic ethers of polyglycols. 2. A cleaning composition for paint applicators comprising a clear, homogeneous admixture of (a) about 18 parts by volume of mineral spirits (b) about 2 parts by volume of butyl di-cresyl phosphate (0) about 2 parts by volume of mono-ethyl ether of ethylene glycol (d) about 1.5 parts by volume of a hydrophilic, nonionic tertiary butyl phenyl polyethylene glycol ether (at least 15 ethylene oxide groups); and
(e) about 1.5 parts by volume of a lipophilic nonionic tertiary butyl phenyl polyethylene glycol ether (2 to 7 ethylene oxide groups).
References Cited in thefile of this patent UNITED STATES PATENTS Ensrninger Aug. 1, 1939 Eisen Dec. 21, 1954 Gamrath -1 Mar. 15, 1955 OTHER REFERENCES