AU3814797A - High water content, low viscosity, oil continuous microemulsions and emulsions, and their use in cleaning applications - Google Patents

Description

HIGH WATER CONTENT, LOW VISCOSITY, OIL CONTINUOUS MICROEMULSIONS AND EMULSIONS, AND THEIR USE IN CLEANING APPLICATIONS

Background of the Invention

This invention concerns microemulsions and emulsions, and their use in various applications.

Microemulsions are well known. Typical components of microemulsions include water, an organic solvent, and surfactants. Often, microemulsions are used as cleaning formulations. For example, U.S. Patent 4,909,962 describes a clear, single phase, pre-spotting composition provided in the form of a microemulsion, solution, or gel, this composition characterized as being infinitely dilutable with water without phase separation. U. S. Patent 5,462,692 describes water continuous microemulsions containing a perfume as their primary water-insoluble hydrocarbon component. The patent employs, among other components, tall oil fatty acids, in formulations useful as hard surface cleaners. U. S. Patent 5,597,792 describes oil continuous, high water content (water in oil) emulsions and microemulsions useful for cleaning purposes, which contain ionic surfactants soluble in the organic solvent phase, such surfactant being of average molecular weight ranging from 350 to 700, preferably greater than 400 and less than 600, exclusive of counterion. One of many categories of ionic surfactants, briefly described and not exemplified, is fatty acid salt.

Other references describe compositions useful in cleaning applications. In systems described as being oil continuous, the systems have low water contents. While predominately describing water continuous systems, some of the examples in U.S. Patent 4,909,962 exemplify low water containing, oil continuous (water in oil) systems. It is desirable to find new compositions for such purposes which possess high water contents and are oil continuous. Such oil continuous microemulsions are especially suitable to function as cleaning compositions to remove oil or grease.

Summary of the Invention

This invention, in one respect, is a single phase oil continuous microemulsion useful as a liquid cleaning composition, comprising: A. water in an amount not less than about 40 percent by weight and not greater than about 75 percent by weight based on the total weight of the microemulsion;

B. an organic solvent or a mixture of two or more organic solvents, wherein the organic solvent or mixture of organic solvents are characterized as containing no more than about 2 weight percent water at 25°C when the organic solvent is saturated with water in the absence of surfactants or other additives, and wherein the organic solvent or the mixture of two or more organic solvents are in an amount not less than about 10 percent and not greater than about 60 percent by weight based on the total weight of the microemulsion;

C. one or more anionic surfactants which are at least partially soluble in the one or more organic solvents, wherein at least one of said surfactants is an olefinic or a saturated fatty acid salt, which has an average molecular weight in the range from 225 to 365 exclusive of the counterion group, and wherein the one or more anionic surfactants are present in a total amount greater than about 0.1 percent and not greater than about 10 percent by weight based on the total weight of the microemulsion. The microemulsion preferably is characterized as being an oil continuous microemulsion and as having an electrical conductivity of less than Z microSiemens/centimeter when measured at use temperatures and a viscosity less than 40 centistokes as measured at use temperatures, wherein Z is represented by the following formula: Z = (1/3)(Φ_w) ∑Am_ι, wherein Φ_W represents the volume fraction of water in the microemulsion, i represents a given electrolyte, A represents the molar conductivity of electrolyte i and m, represents the molarity of electrolyte i in the aqueous phase.

In another respect, this invention is an emulsion, which upon standing at 25°C forms at least two phases wherein one phase is an oil continuous microemulsion, comprising:

A. water in an amount not less than about 60 percent by weight and not greater than about 95 percent by weight based on the total weight of the emulsion;

B. an organic solvent or a mixture of two or more organic solvents, wherein the organic solvent or mixture of organic solvents are characterized as containing no more than 2 weight percent water at 25^CC when the organic solvent is saturated with water in the absence of surfactants or other additives, and wherein the organic solvent or the mixture of two or more organic solvents are present in an amount not less than about 4 percent and not greater than about 40 percent by weight based on the total weight of the emulsion; C. one or more anionic surfactants which are at least partially soluble in the one or more organic solvents, wherein at least one of said surfactants is an olefinic or a saturated fatty acid salt, which has an average molecular weight in the range from 225 to 365 exclusive of the counterion group, and wherein the one or more anionic surfactants are present in a total amount greater than 0.1 percent and less than about 5 percent by weight based on the total weight of the emulsion.

The emulsion preferably is characterized as being an oil continuous emulsion, wherein the emulsion has an electrical conductivity of less than Z microSiemens/centimeter ("μS/cm") when measured at use temperatures and a viscosity less than 40 centistokes ("cSf ) as measured at use temperatures, where Z is as described above, represented by the following formula: Z = (1/3)(Φ ²∑_rA₍m_ι wherein Φ_W represents the volume fraction of water in the microemulsion, i represents a given electrolyte, A represents the molar conductivity of electrolyte i and rn represents the molarity of electrolyte i in the aqueous phase.

In still another respect, this invention is a bicontinuous or water continuous microemulsion or emulsion, meeting all criteria mentioned above except the Z value, which is perturbable into the compositions of the invention described above, through addition of salt or a saturated hydrocarbon of molecular weight less than about 87, and which comprises:

A. an organic solvent or a mixture of two or more organic solvents, wherein the organic solvent or mixture of organic solvents are characterized as containing no more than 2 weight percent water at 25°C when the organic solvent is saturated with water in the absence of surfactants or other additives; and

B. one or more anionic surfactants which are at least partially soluble in the one or more organic solvents, wherein at least one of said surfactants is an olefinic or a saturated fatty acid salt, which has an average molecular weight in the range from 225 to 365 exclusive of the counterion group, and wherein the one or more anionic surfactants are present in a total amount not less than about 0.1 percent and not greater than about 10 percent by weight based on the total weight of the microemulsion.

In yet another respect, this invention is a method for cleaning metal having grease or oily soil on a surface of the metal which comprises applying the microemulsion or the emulsion described above to the metal which has grease or oily soil on the surface of the metal to remove at least a portion of the grease or oily soil from the metal.

The microemulsions and emulsions of this invention find utility as liquid cleaning compositions for use in metal cleaning, hard surface cleaning, circuit board defluxing, automotive cleaning, cold cleaning, dry cleaning, paint stripping and fabric cleaning. Further, the microemulsions and emulsions are particularly effective for removing grease and oily substances. In household and personal care, the compositions of this invention can be used in laundry pretreaters, laundry detergents, coatings, skin cleansers, hair cleaning and conditioning formulations, and in aerosol, pump, spray or liquid pesticide formulations. The compositions can also be used in industrial coatings and sealants applications, such as in adhesives, inks, polishes, latexes and as processing solvents. The compositions of this invention can be used in soil remediation and water desalinization as well as in applications to enhance oil recovery and in the delivery of acids and other additives to oil wells. The compositions of this invention can be used in pharmaceutical applications such as in vaccine adjuvants, topical drug delivery vehicles and in self- heating compositions. The compositions of this invention can be used as media for producing nanoparticles in ceramics applications as well as in applications for manufacture of catalysts such as zeolites and of semiconductors. The compositions of this invention can be used in fuels to solubilize alternative fuel materials such as alcohols. The compositions of this invention can be used to stabilize enzymes, facilitate heterophase reactions and increase surface area in reaction media applications. The compositions of this invention can be used to produce latexes and water soluble polymers by microemulsion polymerization as well as to produce heterophase polymers such as self-reinforcing plastics and to make polymer dispersions. It may also be possible to employ these formulations to dissolve agricultural pesticides and the like with the resultant composition being used to apply on crops. In addition, the microemulsions and emulsions of this invention can be used in cleaning applications to deliver bleaching agent and enzyme in a formulation such that the bleaching agent limitedly degrades the enzyme. The compositions of this invention can also be employed as metal working fluids, including cutting fluids, forming fluids, quenching fluids and protecting fluids, and as force-transmitting hydraulic fluids.

A unique aspect of this invention is the advantage of forming high water containing compositions which are low viscosity and oil continuous, using naturally occurring and renewable unsaturated and saturated fatty acid salts, in low concentrations, to give products having enhanced environmental compatibility and electrolyte tolerance over similar water in oil ("w/o") microemulsions which employ sulfonated surfactants.

Microemulsions

As described above, the microemulsions of this invention contain as essential components water, an organic solvent, and one or more anionic surfactants. Such microemulsions and emulsions are characterized as being oil continuous and having a high water content. Microemulsions are generally considered to be compositions in thermodynamic equilibrium which have suspended particle sizes in the range from 50 to 1000 angstroms. "Electrolyte" as used herein means any solvated salts in the microemulsions or emulsion including ionic surfactant or added salts such as magnesium sulfate, sodium carbonate and sodium chloride. As used herein, "oil continuous" means compositions, either microemulsions or emulsions, which have an electrical conductivity below Z microSiemens/centimeter wherein Z is represented by the following formula: Z = (1/3)(Φ_w)²∑.A.m. wherein Φ_W represents the volume fraction of water in the composition, i represents a given electrolyte, A represents the molar conductivity of electrolyte i and m₍ represents the molarity of electrolyte i in the aqueous phase. Thus, a composition 0.02 molar in an electrolyte having a molar conductivity of 120,000 (microSiemens x liter/ centimeter x mol) and a volume fraction of water of 50 percent has a Z value of 200 and is therefore an oil continuous microemulsion below 200 microSiemens/ centimeter (Z). Preferably, the compositions of this invention have an electrical conductivity below 0.5 Z, more preferably below 0.25 Z and most preferably below 0.1 Z. By contrast bicontinuous compositions are above Z and below 2Z and water continuous compositions are above 2Z.

In the single-phase, oil continuous microemulsions, the water is present in an amount not less than about 40 percent by weight and not greater than about 75 percent by weight based on the total weight of the microemulsion. Preferably, the microemulsion contains not less than about 45 weight percent water. Preferably, the microemulsions contain not greater than about 70 weight percent water, more preferably not greater than about 65 weight percent and even more preferably not greater than about 60 weight percent.

In the single-phase, oil continuous microemulsions, an organic solvent or a mixture of two or more organic solvents is employed, wherein the organic solvent or mixture of organic solvents are characterized as containing no more than 2 weight percent water at 25°C when the organic solvent is saturated with water in the absence of surfactants or other additives. Preferably, the organic solvent or mixture of organic solvents contain no more than 1 weight percent water at 25°C when saturated, more preferably no more than 0.5 weight percent water. Water uptake of an organic solvent can be readily determined by water titration, for example, wherein water is added to the one or more organic solvents until cloudiness of solution is observed or an excess water phase develops. The organic solvent or the mixture of two or more organic solvents are present in an amount not less than about 10 percent and not greater than about 60 percent by weight based on the total weight of the microemulsion. Preferably, the organic solvent or the mixture of two or more organic solvents are present in an amount not less than about 15 weight percent, more preferably not less than about 20 percent, most preferably not less than about 25 weight percent; and preferably, not greater than 50 weight percent. Classes of organic solvents that can be used in the practice of this invention include aliphatic alcohols, aliphatic esters, aliphatic hydrocarbons, chlorinated aliphatic hydrocarbons, aromatic hydrocarbons, aliphatic diesters, aliphatic ketones, and aliphatic ethers. In addition, a solvent can contain two or more of these functional groups or can contain combinations of these functional groups. For example, alkylene glycol diethers, alkylene glycol monoethers and alkylene glycol ether acetates may be employed as solvents in the practice of this invention. As used herein, alkylene glycol ethers includes dialkylene glycol ethers. The alkylene glycol monoethers and alkylene glycol diethers are particularly useful to decrease viscosity of a microemulsion. Preferred classes of organic solvents are the aliphatic hydrocarbons, aromatic hydrocarbons, alkylene glycol monoethers, alkylene glycol diethers, and alkylene glycol ether acetates. More preferred classes of organic solvents are the aliphatic hydrocarbons, alkylene glycol monoethers, and alkylene glycol diethers.

The aliphatic alcohols can be primary, secondary or tertiary. Preferred aliphatic alcohols have 4 to 24 carbon atoms. Representative examples of more preferred aliphatic alcohols include 1-hexanol, isoheptyl alcohol, octanol, 2-ethyl-hexanol, nonanol, dodecanol, undecanol, and decanol.

Preferred aliphatic esters have 4 to 24 carbon atoms. Representative examples of more preferred aliphatic esters include methyl laurate, methyl oleate, hexyl acetates, pentyl acetates, octyl acetates, nonyl acetates, and decyl acetates.

The aliphatic hydrocarbons can be linear, branched, cyclic or combinations thereof. Preferred aliphatic hydrocarbons contain 3 to 24 carbon atoms, preferably 6 to 24 carbon atoms. Representative examples of more preferred aliphatic hydrocarbons include alkanes such as liquid propane, butane, pentane, hexane, heptane, octane, decane, dodecane, hexadecane, mineral oils, paraffin oils, decahydronaphthalene, bicyclohexane, cyclohexane, and olefins such as 1-decene, 1-dodecene, octadecene, and hexadecene. Examples of commercially available aliphatic hydrocarbons are Norpar™ 12, 13, and 15 (normal paraffin solvents available from Exxon Corporation), Naphtha SC 140 petroleum distillate (also from Exxon), Isopar™ G, H, K, L, M, and V (isoparaffin solvents available from Exxon Corporation), and Shellsol™ solvents (Shell Chemical Company).

Preferred chlorinated aliphatic hydrocarbons contain 1 to 12 carbon atoms, more preferably contain from 2 to 6 carbon atoms. Representative examples of more preferred chlorinated aliphatic hydrocarbons include methylene chloride, carbon tetrachloride, chloroform, 1 ,1 ,1 -trichloroethane, perchloroethylene, and trichloroethylene. Preferred aromatic hydrocarbons contain 6 to 24 carbon atoms. Representative examples of more preferred aromatic hydrocarbons include toluene, naphthalene, biphenyl, ethyl benzene, xylene, alkyl benzenes such as dodecyl benzene, octyl benzene, and nonyl benzene.

Preferred aliphatic diesters contain 6 to 24 carbon atoms. Representative examples of more preferred aliphatic diesters include dimethyl adipate, dimethyl succinate, dimethyl glutarate, diisobutyl adipate, and diisobutyl maleate.

Preferred aliphatic ketones have 4 to 24 carbon atoms. Representative examples of more preferred aliphatic ketones include methyl ethyl ketone, diethyl ketone, diisobutyl ketone, methyl isobutyl ketone, and methyl hexyl ketone.

Preferred aliphatic ethers have 4 to 24 carbon atoms. Representative examples of more preferred aliphatic ethers include diethyl ether, ethyl propyl ether, hexyl ether, butyl ether, and methyl t-butyl ether.

Preferred alkylene glycol monoethers, dialkylene glycol monoethers, alkylene glycol diethers, and alkylene glycol ether acetates include propylene glycol diethers having 5 to 25 carbon atoms, propylene glycol ether acetates having 6 to 25 carbon atoms, propylene glycol monoethers having 7 to 25 carbon atoms, ethylene glycol ether acetates having 6 to 25 carbon atoms, ethylene glycol diethers having 6 to 25 carbon atoms, and ethylene glycol monoethers having 8 to 25 carbon atoms. Representative examples of more preferred solvents within this broad class include propylene glycol dimethyl ether, propylene glycol benzyl methyl ether, propylene glycol butyl methyl ether, propylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol butyl methyl ether, dipropylene glycol dibutyl ether; propylene glycol methyl ether acetate, dipropylene glycol methyl ether acetate, propylene glycol butyl ether acetate; propylene glycol monobutyl ether, propylene glycol monohexyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monohexyl ether; ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol butyl ether acetate; ethylene glycol diethyl ether, ethylene glycol dibutyl ether; ethylene glycol hexyl ether, ethylene glycol octyl ether, ethylene glycol phenyl ether, diethylene glycol hexyl ether, and diethylene glycol octyl ether. Most preferred alkylene glycol monoethers are propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, propylene glycol monopropyl ether and dipropylene glycol monopropyl ether.

In preferred embodiments of the present invention, alkylene glycol monoethers are employed in admixture with one or more other organic solvents. The addition of alkylene glycol monoethers facilitates the preparation of low viscosity microemulsions and emulsions. The alkylene glycol monoether is present in an amount not less than about 5 weight percent based on the total weight of the microemulsion, preferably not less than about 10 weight percent, more preferably not less than about 15 weight percent; not greater than about 50 weight percent, preferably not greater than about 40 weight percent and more preferably not greater than about 25 weight percent. In general, the ratio of glycol ether to total surfactants should be greater than 2 to 1 by weight, in both microemulsions and emulsions. The alkylene glycol monoether is present in the emulsions containing about 70 - 80 percent water in an amount not less than about 5 weight percent based on the total weight of the emulsion, and not greater than about 15 percent.

In the single phase oil continuous microemulsions, one or more anionic surfactants of specified chemical structure are employed which are at least partially soluble in the one or more organic solvents. The one or more anionic surfactants are preferably also characterized as possessing greater solubility in the one or more organic solvents than in water and preferentially partitioning into the organic solvent in a mixture of water and organic solvent. Preferably, the one or more anionic surfactants are no more than sparingly water soluble. Here the term solubility does not include dispersability or emulsifiability. The one or more anionic surfactants have a molecular weight greater than 225 and less than 365. If two or more anionic surfactants are employed, "molecular weight" as used above is calculated based on the average of the molecular weights of the two or more anionic surfactants. Often the naturally occurring fatty acids used to prepare the anionic surfactants are available commercially as blends of various molecular weight components, in various degrees of unsaturation and carbon content.

A preferred class of anionic surfactants are anionic surfactants of formula (R¹ - COO)_y M (formula I) wherein R¹ represents an olefinically unsaturated or a saturated alkyl, y is 1 or 2, wherein M represents a cationic counterion and wherein the total number of carbons in R¹ is from 13 to 23. Preferably R¹ is unsaturated internally in the alkyl group and is not alpha.beta-unsaturated nor is the olefinic unsaturation conjugated with the carboxyl group. The molecular weight of an anionic surfactant of formula (I) is calculated exclusive of the weight of M; that is, molecular weight is calculated for R - COO only.

The anionic surfactants containing M as a counterion can be readily prepared from their acid precursors wherein M is hydrogen, such as by reacting the carboxylic acid with a metal hydroxide including hydroxides of ammonium, lithium, sodium, potassium, magnesium, calcium, etc. Selection of a particular M counterion is not critical so long as the resulting surfactant remains at least partially soluble in the organic solvent and preferably is no more than sparingly water soluble and provides anionic surfactants which are capable of producing the microemulsions and emulsions of this invention. Preferably, M is monovalent, and more preferably is selected from sodium, potassium and "onium" (e.g., quat. nitrogen as in ammonium, etc.) cations. Preferably, the anionic surfactants have an ave. molecular weight of at least about 250, more preferably at least 280 and most preferably at least about 295. Preferably, the anionic surfactants have a molecular weight not greater than 345 and more preferably not greater than 340, and most preferably not greater than 337, exclusive of the counterion M.

Examples of specific anionic surfactants useful in the invention are salts of the following olefinic and saturated aliphatic and alicyclic carboxylic acids:

Olefinic fatty acids: myristoleic (cis-tetradec-9-enoic) acid; palmitoleic (cis-9-hexadecenoic) acid; linolenic (9,12,15-octadecatrienoic) acid; linoleic (9,12 or 13-octadecadienoic) acid; oleic (cis-9-octadecenoic) acid; arachidonic (5,8,11 ,14-eicosatetraenoic) acid; erucic (cis-13- docosenoic) acid; and unsaturated, 5-carbon alicyclic acids: hydnocarpic acid (C₎₆H₂₈O₂); chaulmoogric acid (C₁₈H₃₂O₂); and gorlic acid (C,_βH₃₀O₂); and

Saturated fatty acids: myristic (tetradecanoic - C₁₄H₂₈O₂) acid; palmitic (hexadecanoic C^H^O_j) acid; stearic (octadecanoic - C₁₈H₃₆O₂) acid; eicosanoic (arachidic - C₂₀H_<0O₂) acid; and docosanoic (behenic - C₂₂H₄₄O₂) acid.

An advantage of using the preferred anionic surfactants is that relatively small amounts of the preferred anionic surfactants are needed to provide the high water content, oil continuous microemulsions and emulsions of this invention. Consequently, the amount of residual anionic surfactant left on a surface cleaned with the microemulsions and emulsions is minimal, and problems of streaking and so forth are also minimal. An additional advantage is that since the acids are mostly derivatives of natural products, they are considered by some to be more "environmentally friendly" than typical synthetic anionic surfactants.

Preferably, the preferred anionic surfactants are present in the microemulsions in an amount not less than about 0.5 weight percent and more preferably not less than about 1 weight percent. Preferably, the preferred anionic surfactants are present in the microemulsions in an amount not greater than about 6 percent and more preferably in an amount not greater than about 5, weight percent. While a carboxylic acid (in addition to its salt) may be included in the formulation, the acid acts not as a surfactant but much as the aliphatic alcohol organic solvents mentioned above. However, the acids act less effectively on a weight basis than such an alcohol, due to the generally higher molecular weight of the acids.

In the single phase oil continuous microemulsions, the specific carboxylic acid salt surfactants previously described may be supplemented with other typical anionic, sulfonate surfactants of the sulfonated alkylbenzene/toluene/naphthalene-type commonly available. For example, those represented by the formula R_κB-SO₃M wherein R represents alkyl, x is 1 or 2, B is a biradical when x is 1 or is a triradical when x is 2 and which is derived from an aromatic moiety and wherein M represents the same cationic counterion mentioned previously, and wherein the total number of carbons in R_κ is from 18 to 30. Molecular weight of an anionic surfactant of formula R_xB-SO₃M is calculated exclusive of the molecular weight of counterion M; that is, molecular weight is calculated for R_xB-SO₃ only. Such adjunct sulfonate surfactants containing M as a counterion can be readily prepared from their precursor sulfonic acid by reacting it with a metal hydroxide including hydroxides of ammonium, lithium, sodium, potassium, magnesium, calcium. Selection of a particular M counterion is not critical so long as the resulting surfactant remains at least partially soluble in the organic solvent and, preferably, no more than sparingly water soluble, and proves capable of assisting the specific carboxylic acid-derived anionic surfactants in producing the microemulsions and emulsions of this invention. Preferably, M is monovalent. Preferably, B is derived from benzene, toluene or naphthalene. Preferably, the adjunct sulfonate surfactants have a molecular weight greater than 400. Preferably, these adjunct surfactants have a molecular weight less than 600 and more preferably less than 550.

In the single phase oil continuous microemulsions, one or more nonionic surfactants can be also be employed to supplement or enhance the effectiveness of the anionic surfactant(s). The one or more nonionic surfactants are employed in an amount from 0 to about 6 percent by weight based on the total weight of the microemulsion. Preferably, the one or more nonionic surfactants are employed in an amount not greater than about 3, more preferably not greater than about 2, weight percent. Preferably the combined weight of the anionic surfactants and nonionic surfactants amounts to not greater than about 10, and more preferably not greater than about 8, weight percent of the microemulsion.

Nonionic surfactants which may usefully be employed in this invention include alkylphenol alkoxylates and primary and secondary alcohol alkoxylates wherein the alkoxylate can be ethoxy, propoxy, butoxy or combinations thereof. Mixtures of alcohol alkoxylates can be used. Preferred nonionic surfactants are alkylphenol ethoxylates and primary and secondary alcohol ethoxylates. The alkylphenol ethoxylates and primary and secondary alcohol ethoxylates are represented by the formula:

R-O-(CH₂CH₂O)_π-H

wherein R is a hydrocarbon containing 9 to 24 carbon atoms and n is a number averaging from 1 to 9. Commercially available nonionic surfactants are sold by Shell Chemical Company under the name Neodol™ and by Union Carbide Corporation under the name Tergitol™. Representative examples of preferred commercially available nonionic surfactants include Tergitol™ 15-s-series and Neodol™ 91 or 25 series. Additional representative examples of useful nonionic surfactants include polyoxyethylated polypropylene glycols, polyoxyethylated polybutylene glycols, polyoxyethylated mercaptans, glyceryl and polyglyceryl esters of natural fatty acids, poiyoxyethylenated sorbitol esters, polyoxyethylenated fatty acids, alkanol amides, tertiary acetylinic glycols, N-alkyl- pyrrolidones, and alkyl polyglycosides. More preferred nonionic surfactants employed in this invention are secondary alcohol ethoxylates. Representative examples of preferred commercially available secondary alcohol ethoxylates include Tergitol™ 15-S-3, Tergitol™ 15-S-5 and Tergitol™ 15-S-7.

The microemulsions of this invention may further contain other types of surfactants such as amphoteric surfactants with molecular weights above 350, betaines such as N-alkylbetaines including N,N,N-dimethyl- -hexadecyl-amino-(3-propionate), and sulfobetaines such as N,N,N-dimethyl-hexadecyl-amino-propylene sulfonate.

Conductivity of a microemulsion of this invention is measured at use temperatures as the conductivity can vary with temperature, because the phase behavior of the microemulsion can also change with temperature. It follows that it is possible to make a microemulsion which is not oil continuous and does not fall within the scope of this invention at room temperature, but which when heated to a higher use temperature is oil continuous and does fall within the scope of this invention. Electrical conductivity can be measured using standard techniques and conventional equipment, employing, for example, a Fisher brand model 326 conductivity meter which has a one centimeter gap between the anode and cathode in the probe. When such a device is used, the probe is simply immersed in the solution, the instrument is allowed to equilibrate, and the conductivity value obsen ed from the device. It should be understood that the device must be calibrated using standard electrolyte solutions of known conductivity prior to measuring conductivity of compositions of this invention.

The microemulsions of this invention have a viscosity less than 40 centistokes as measured at use temperatures. Viscosity is measured at use tempera-tures because viscosity can vary with temperature. It follows that it is possible to make a microemulsion which is not within the scope of this invention at room temperature, but which when heated to a higher use temperature possesses a viscosity which does fall within the scope of this invention. Preferably, the single-phase, oil continuous microemulsions have a viscosity less than 30 centistokes, more preferably less than 20 centistokes, and even more preferably less than 10 centistokes and most preferably less than about 8 centistokes. An advantage of preferred microemulsions of this invention is that upon dilution with up to at least ten percent by weight of water or oil, viscosity of the resulting composition does not increase above 40 centistokes. Viscosity can be measured by well known methods using conventional equipment designed for such purpose. For example, a capillary viscometer such as a Cannon-Fenske capillary viscometer equipped with a size 350 capillary can be used following the procedure of ASTM D 445. Alternatively, a Brookfield Model LVT Viscometer with a UL adapter can be used to measure viscosities in centipoise.

It follows that the one or more surfactants are employed in an amount effective to form an oil continuous microemulsion. This amount varies depending on the amount and nature of the components in the entire microemulsion composition. It is equally important, however, that the microemulsions contain a high water content, generally above 40 weight percent based on the total weight of the composition. This being the case, the invention microemulsions are characterized as being compositions which are neither bicontinuous nor water continuous.

A generalized methodology used to design high water, single phase microemulsion cleaning systems is as follows: (A) select an organic solvent or organic solvent blend having the desired low water uptake; (B) determine the relationship between surfactant structure (e.g., hydrophilicity) and conductivity, viscosity and phase behavior (e.g., the presence of liquid crystals) of compositions with the desired level of water, surfactants, organic solvent and additive contents by varying only the surfactant or surfactant blend composition; (C) the procedure of steps A and B may be repeated as necessary at several solvent and surfactant concentrations until the amount and types of solvent and surfactant necessary to give a single phase oil continuous structure at the desired water level (based on the information generated in step B) are determined; (D) determine the viscosity and conductivity of the oil continuous microemulsion; (E) if viscosity is too high, it may be adjusted by reducing surfactant concentration, by changing the solvent composition (e.g., by increasing the level of an oxygenated solvent such as glycol ether or alcohol), by adding a second class of surfactant (e.g., nonionic to an anionic based system) or by adding electrolytes to up to 0.6, preferably up to 0.2 weight percent (excluding surfactant) or by changing the organic solvent to surfactant ratio; (F) if needed, adjust surfactant or surfactant blend composition (repeat step B, C, and D with new formulation) from step E to provide a single phase oil continuous microemulsion; and (H) confirm that viscosity and conductivity of the oil continuous microemulsion are within the scope of this invention. It should be noted that some steps may be deleted or repeated depending on the circumstances.

In general, optimum cleaning performance is obtained when the microemulsion systems are prepared with a minimum amount of surfactant. This leads to low residue and lower inherent viscosities (in the absence of liquid crystals). In order to determine the minimum amount of surfactant required, the methodology described above should be repeated at various surfactant levels for a given solvent system and water content. Typically, the minimum surfactant level is defined as the lowest surfactant level where one may traverse the region of microemulsion structures from water continuous to oil continuous without the generation of any excess phases. In practice, it has been found that efficient systems (lowest surfactant levels) are obtained when one uses predominantly a anionic surfactant of the higher end on the range of molecular weight specified and then adjusts the phase behavior using a second component (either addition of small amounts of electrolyte or adjusting the composition of the solvent phase, for example by addition of the low molecular weight hydrocarbon described below).

Another consideration when designing optimum oil continuous microemulsions is the avoidance of high viscosity regions during the cleaning process. When used, the microemulsions described here may be transformed from their oil continuous structure through the bicontinuous region into the water continuous, via, e.g., evaporation of solvent components giving a new solvent balance; solubilization of soils which may favor a water continuous structure; or addition of water during a water rinsing procedure. For this reason, the most preferred systems should maintain low viscosities not only in the oil continuous region but also in the bi- and water-continuous regions.

Addition of electrolyte is an effective method for adjusting phase behavior; however, increasing electrolyte content decreases surfactant efficiency. Therefore, total electrolyte content (excluding surfactants) should be minimized. In another manifestation of the invention, a microemulsion having a conductivity, measured at its use temperature, of greater than its Z number (a bicontinuous or an oil in water microemulsion) comprising the components mentioned earlier may be perturbed (also referred to loosely as "titrated" with aqueous sodium carbonate electrolyte) to generate microemulsions. This perturbation is accomplished by the introduction, by total weight of the composition, of either up to about 0.5 percent of an electrolyte as mentioned above, or up to about 20 percent, preferably up to 10 percent or less, of an aliphatic or alicyclic hydrocarbon of not greater than 100 molecular weight. Typically, the electrolyte selected for this purpose can be one or more of the salts mentioned previously or a soluble polymer electrolyte, for example, a water-soluble polyacrylic acid or polyacrylate salt. The low molecular weight hydrocarbon can, for example, be propane, butane, pentane, hexane or cyclohexane. Generally the lower weight the hydrocarbon, the more effective in perturbation. The use of the electrolyte is described below in all of the Examples and the effective use of the lower hydrocarbon (cyclohexane) in Example 8 (Samples E-1 through E-3) and Example 9 (Samples H-1 through H-4). In Example 13, a number of Sample formulations were prepared using the methodology noted above, until the properties were appropriately adjusted by varying the levels and types of the formulations' components and the Na Carb electrolyte in Samples S-1 through S-5, where the w/o microemulsion of conductivity less than Z was ultimately prepared by perturbation.

Emulsions

The cleaning emulsions of this invention are well dispersed when sufficiently mixed; however, upon standing the emulsions form at least two phases wherein one phase is an oil continuous microemulsion. Typically, only two phases form when the emulsions are allowed to stand. As used herein, "standing" means allowed to sit undisturbed for 7 days at 25°C.

The emulsions of this invention contain water in an amount greater than 60 percent by weight and less than 95 percent by weight based on the total weight of the emulsion. Preferably, the emulsions contain water in an amount greater than 70 weight percent, more preferably greater than 75 weight percent; preferably less than 90 weight percent, more preferably less than 88 weight percent.

The types of organic solvents employed in the emulsions of this invention are the same as those described above under the Microemulsions heading, including all the classes of solvents, physical characteristics of the solvents, representative examples and preferred solvents. However, the amount of solvent employed in the emulsions of this invention is greater than 4 percent and less than 40 percent by weight based on the total weight of the emulsion. Preferably, the amount of solvent employed for an emulsion is greater than 8 weight percent, more preferably greater than 10 weight percent; preferably less than 25 weight percent, and more preferably less than 15 weight percent.

The descriptions of useful ionic surfactants and nonionic surfactants are the same as that described above under the Microemulsions heading. However, the amount of ionic surfactant employed is from about 0.1 percent to about 5 percent by weight based on the total weight of the emulsion. Preferably, the amount employed is less than about 3 weight percent.

The definition used above to describe "oil continuous" compositions is also used to describe the emulsions. Conductivity is measured, after agitation and before phase separation occurs, at use temperatures as the conductivity can vary with temperature because the phase behavior of the emulsion can also change with temperature. It follows that it is possible to make an emulsion which is not oil continuous and does not fall within the scope of this invention at room temperature, but which when heated to a higher use temperature is oil continuous and does fall within the scope of this invention.

In addition, the emulsions have a viscosity less than 40 centistokes as measured at use temperatures. Viscosity is measured at use temperatures because viscosity can vary with temperature. It follows that it is possible to make an emulsion which is not within the scope of this invention at room temperature, but which when heated to a higher use temperature possesses a viscosity which does fall within the scope of this invention. Preferably, the emulsions have a viscosity less than 20 centistokes, more preferably less than 10 centistokes.

A generalized methodology utilized to design high water emulsion cleaning systems is as follows: (A) select an organic solvent or organic solvent blend having the desired low water uptake; (B) determine the relationship between surfactant structure (e.g., hydrophilicity) and conductivity of a composition with the desired water, surfactants, organic solvent, and additive contents by varying only the surfactant or surfactant blend composition; (C) the procedure of steps A and B may be repeated as necessary at several solvent and surfactant concentrations until the amount and types of solvent and surfactant necessary to give an oil continuous emulsion structure at the desired water level (based on the information generated in step B) are determined; (D) determine the viscosity, conductivity and water content of the emulsion, stability (time to phase separation) of the oil continuous emulsion; (E) if viscosity is too high, it may be adjusted by varying the surfactant concentration, organic solvent to surfactant ratio, or by addition of an additional organic solvent, such as a glycol ether, to decrease viscosity; (F) if needed, adjust surfactant or surfactant blend composition (repeat step B, C, and D with new formulation from step E) to provide an oil continuous emulsion; and (H) confirm that viscosity and conductivity of the oil continuous microemulsion are within the scope of this invention. It should be noted that some steps may be deleted or repeated depending on the circumstances.

Qptionals

In addition to the required components listed above for microemulsions and emulsions, respectively, a variety of optional materials may be added depending on end use, desired physical properties of the microemulsion or emulsion, and the like. Hence, various detergent additives, chelating agents (such as tetrasodium ethylenediamine tetraacetate "EDTA"), sequestering agents, suspension agents, perfumes, enzymes (such as the lipases and proteases), brighteners, preservatives, corrosion inhibitors, phosphatizing agents, UV absorbers, disinfectants, biologically active compounds such as pesticides, herbicides, fungicides and drugs, fillers, and dyes may be included in a microemulsion or emulsion of this invention.

Prior to use, any sodium alkyl toluene sulfonates used to supplement the anionic carboxylate surfactant in the preparation of microemulsions should be treated to remove residual sulfate salts and alkyl toluene disulfonate by extraction of a solution of surfactant in PnB using aqueous hydrogen peroxide followed by neutralization using aqueous sodium hydroxide. "PnB" denotes propylene glycol n-butyl ether (DOWANOL™ PnB obtained from The Dow Chemical Company), "PnP" denotes propylene glycol n-propyl ether (DOWANOL™ PnP obtained from The Dow Chemical Company), "w/o" denotes oil continuous microemulsions, "o/w" denotes water continuous microemulsions, Naphtha SC 140 is a commercial petroleum distillate obtained from Exxon Corporation and Exxal™ 7 is a commercial isoheptyl alcohol (5-methyl hexanol), also obtained from Exxon.

Sodium erucate ("Na Erucate") is the sodium salt of erucic acid and is prepared in situ, by neutralization of erucic acid with 5N aqueous sodium hydroxide solution. Similarly, the other acid salts are prepared by neutralization of their respective carboxylic acid with sodium hydroxide or other aqueous alkaline metal or alkaline earth base, e.g. potassium hydroxide or the like. The term "Na Oleate", "Na Stearate", "Na Linoleate", "Na Palmitate", etc., represents the sodium salt of each of those respective carboxylic acids.

The following examples are included for the purposes of illustration only and are not to be construed to limit the scope of the invention or claims.

Unless otherwise indicated, all parts and percentages are by weight. In all examples, viscosities were measured at 25°C using ASTM D 445 on a Cannon-Fenske capillary viscometer using a size 350 capillary or on a Brookfield Model LVT Viscometer with a UL adapter.

Example 1. Concentrate

A concentrate solution is prepared by mixing 16.2 parts Exxal™ 7 isoheptyl alcohol with 16.2 parts DOWANOL™ PnP propylene glycol n-propyl ether ("PnP") and 41.7 parts DOWANOL™ PnB propylene glycol n-butyl ether ("PnB"), in which erucic acid is combined and then neutralized with a 5N aqueous sodium hydroxide solution, to yield 16.2 parts Na erucate and 9.7 parts water. The result is a low viscosity, stable, clear single- phase solution. This concentrate solution may subsequently be "perturbed", by the addition of electrolyte, water and organic solvent, into a resulting w/o microemulsion of the invention. Example 2. Water-in-Oil Microemulsion

A sample of 3.08 parts of the solution prepared as described in Example 1 is mixed with 2.2 parts of n-heptane and 4.72 parts Dl water to give a two-phase product, with excess oil phase, and a conductivity of 4040 microSiemens/centimeter ("μS/cm") (where Z =1374) having overall composition of 5 parts Na erucate, 22 parts heptane, 12.9 parts PnB, 5 parts PnP, 5 parts Exxal 7, and 50.1 parts water. The two-phase product is "titrated" with a 10 percent sodium carbonate ("Na Carb") solution. Upon addition of 1 part of the Na Carb solution, dispersed liquid crystals ("LCs") form and resulting sample's conductivity drops to 1770 μS/cm (Z =1475). After a total of 1.25 part Na Carb solution is added, a clear, single- phase microemulsion product forms having 1430 μS/cm conductivity(Z =1490), and after a total 1.5 part Na Carb solution is added, the resulting clear, single-phase, bluish water/oil microemulsion has 430 μS/cm conductivity(Z = 1590) and a viscosity of 9.7 centistokes ("cSt") measured by Brookfield LVT viscometer with UL adapter.

Example 3. Perturbable Microemulsion and W/O Microemulsion

In the manner of Example 1 , a sample is prepared from the same components in slightly modified ratios, by varying amounts of the two glycol ethers - employing instead 14.9 parts PnB and 3 parts PnP. The resulting o/w microemulsion contains LCs and has conductivity of 4250 μS/cm (Z = 1375). This is a perturbable microemulsion which can be converted into a w/o microemulsion by addition of electrolyte. When titrated with a 10 percent Na Carb solution (the electrolyte), as described in Example 2, the o/w microemulsion is converted to a single-phase, clear bluish water/oil microemulsion of low viscosity. Addition of 1 part of the Na Carb solution gives a microemulsion having a conductivity of 530 μS/cm (Z = 1472) and a 9.5 cSt viscosity.

Example 4. Naphtha-based Product and Perturbable Microemulsion

In the manner of Example 1 , a sample is prepared, substituting a petroleum distillate - Naphtha SC 140 supplied by Exxon Chemical, for the previous heptane organic solvent base. The components of the sample and their respective amounts are: Naphtha

SC 140 = 22 parts, PnB = 15 parts, PnP = 3 parts, Exxal 7 = 5 parts, Na erucate = 5 parts and Dl water = 50 parts. The resulting sample is a clear, single-phase o/w perturbable microemulsion, having conductivity of 4420 μS/cm (Z = 1459). When that perturbable o/w microemulsion is titrated with 10 percent Na Carb solution, the following results are observed: 1 part Na Carb solution gives a clear, single-phase product of conductivity 3620 μS/cm (Z = 1547); 1.75 part Na Carb solution gives an excess water phase milky emulsion which has conductivity of 1030 μS/cm (Z = 1620) and viscosity of 11.5 cSts. Then to that emulsion, an additional quantity of the Naphtha SC 140 organic solvent is added to adjust the water/oil balance in order to produce the desired w/o microemulsion. When a total of 4.76 parts of the Naphtha SC 140 have been added, a single-phase, clear bluish w/o microemulsion is formed which exhibits conductivity of 1110 μS/cm (Z = 1370) and viscosity of 7.5 cSt. It is an excellent grease removal product.

Example 5. Cleaning Process

The 1110 μS/cm conductivity, low viscosity w/o microemulsion prepared as described in Example 4 is contacted with steel coupons coated with Lithium grease in accordance with the standard Conoco cleaning test. Excellent grease removal and cleaning is observed.

Example 6. d-Limonene-based Product

In the same fashion as the preceding examples, a sample is prepared substituting d-limonene for the heptane used previously. d-Limonene is an organic base solvent component commonly employed in a wide range of cleaning products. The sample prepared comprises the following amounts of each respective component: d-limonene = 22 parts, PnB = 14.9 parts, PnP = 3 parts, Exxal 7 = 5 parts, and Dl water = 50.1 parts, and the resulting o/w microemulsion contains LCs and has conductivity of 4670 μS/cm conductivity (Z = 1527). When that composition is "titrated" with the 10 percent Na Carb solution, 0.5 part Na Carb solution provides a resulting microemulsion still containing LCs, with conductivity of 1180 μS/cm conductivity (Z = 1573). Further titration to a total of 1 part Na Carb solution converts the sample to a clear, single-phase w/o microemulsion of 375 μS/cm conductivity (Z = 1613) and having a viscosity of 13.5 cSt. Example 7. High Water-Content Emulsions

In the same fashion as Example 2, a formulation is prepared using: Na erucate = 2.5 parts, heptane = 10.5 parts, PnB = 3.5 parts; PnP = 3.5 parts, Dl water = 80 parts. To that perturbable o/w emulsion containing an excess of the oil phase, are added varying amounts of the Na Carb, passing through intermediate bicontinuous formulations, until a clear w/o microemulsion with some excess water phase results. Upon agitation, this gives an emulsion which has a conductivity of approximately .5Z and a viscosity of 12.5 cSt. The various stages of this preparation are shown graphically in Table 1 , Samples A-1 through A-4.

Examples 8 - 13. Use of Other Na Carboxylates as the Anionic Surfactant Component

In a fashion similar to the preceding Examples, various formulations are prepared employing a variety of sodium carboxylic acid salts in place of the Na erucate found in the previous Examples. The other components of the formulations are selected from Na Carb, n-heptane, PnB, 1 -hexanol and Dl water, and in some formulations, cyclohexane. With each different Na carboxylate, a series of formulations are prepared - adjusting the ratios of the various components to attain the desired properties of conductivity lees than 1Z and a low viscosity. From these series, one can observe how the methodology described in the teachings above is used for the preparation and then fine tuning of each formulation. The properties of each microemulsion or emulsion formulation can also be observed in these Examples. The formulations' various compositions and their respective resulting physical properties and calculated Z numbers are presented in Tables 2 - 7, found below.

TABLE

Example 7

Na Erucate Heptane PnB PnP Water CycloNa2C03 Phase Conductivity Viscosity Z hexane Behavior (μS/cm) (cSt)

Sample

A-1 2.5 10.5 3.5 3.5 80 0 0 excess oil 2080 na 690

A-2 2.5 10.5 3.5 3.5 79.4 0 0.6 excess oil 8160 na 2400

A-3 2.5 10.5 3.5 3.5 78.8 0 1.2 1 p. cl. 4400 na 3920

A-4 2.5 10.5 3.5 3.5 78.6 0 1.4 excess water 2450 12.5 4490 TABLE 2

Example 8

Na Oleate Heptane PnB 1 -hexanol Water CycloNa2C03 Phase Conductivity Viscosity Z hexane Behavior (μS/cm) (cSt) t Sample o

B 5.5 21.5 23 0 49.8 0 0.2 1 p. cl. 5360 na 1880

C-1 5.5 22 17.5 5 50 0 0 1 p. cl. 4550 na 1600

C-2 5.44 21.78 17.33 4.95 50.4 0 0.1 1 p. cl. 4120 na 1740

C-3 5.39 21.57 17.16 4.9 50.8 0 0.2 1 p. cl. 1950 6.5 1880

D-1 5.39 21.57 17.16 6.86 49 0 0 LCs na na 1840

D-2 5.37 21.46 17.07 6.82 49.2 0 0.05 LCs na na 1910

D-3 5.35 21.36 17 6.8 49.4 0 0.1 1 p. cl. 2640 na 1980

D-4 5.33 21.25 16.9 6.76 49.6 0 0.15 1 p. cl. 1270 na 2050

D-5 5.32 21.2 16.83 6.74 49.74 0 0.17 1 p. cl. 620 7 2080

E-1 5.42 21.67 17.24 4.92 50.6 0 0.15 1 p. cl. 3060 na 1810

E-2 4.93 19.73 15.69 4.48 46.06 8.97 0.14 1 p. cl. 1920 na 1630

E-3 4.53 18.11 14.4 4.1 42.24 16.5 0.12 1 p. cl. 1380 7 1450

1 p. cl. = ^■ t phase clear na=not measured LCs=liquid crystals

TABLE

Example 9

Na Stearate Heptane PnB 1 -hexanol Water Cyplp- Na2C03 Phase Conductivity Viscosity Z hexane Behavior (μS/cm) (cSt)

Sample

F 5.5 22 22.5 0 49.8 0 0.2 1 p. cl. 5600 na 1870

G-1 5.5 22 17.5 5 50 0 0 1 p. cl. 4200 na 1600

G-2 5.44 21.78 17.33 4.95 50.4 0 0.1 LCs na na 1740

G-3 5.39 21.57 17.16 4.9 50.8 0 0.2 1 p. cl. 2000 7 1880

H-1 5.5 22 17.5 5 49.8 0 0.2 1 p. cl. 2500 na 1880

H-2 5.24 20.95 16.67 4.76 47.43 4.76 0.19 1 p. cl. 1780 na 1690

H-3 5 20 15.91 4.54 45.27 9.1 0.18 1 p. cl. 1140 na 1500

H-4 4.58 18.33 14.58 4.17 . 41.5 16.67 0.17 1 p. cl. 340 na 1130

1-1 5.5 22 15 7.5 50 0 0 LCs na na 1610

I-2 5.5 22 15 7.5 49.95 0 0.05 LCs na na 1680

I-3 5.5 22 15 7.5 49.9 0 0.1 1 p. Cl. 600 8.5 1750 TABLE 4

ExamplelO I

Na Linoleate Heptane PnB 1 -hexanol Water CycloNa2C03 Phase Conductivity Viscosity Z hexane Behavior (μS/cm) (cSt)

Sample

J 5.5 22 22.5 0 49.8 0 0.2 1 p. cl. 4800 na 1870

K-1 5.5 22 17.5 5 50 0 0 LCs na na 1600

K-2 5.44 21.78 17.33 4.95 50.4 0 0.1 LCs na na 1740

K-3 5.39 21.57 17.16 4.9 50.8 0 0.2 1 p. cl. 1500 7 1880

1 p. cl. = 1 phase clear na=not measured LCs=liquid crystals

TABLE

Examplell

Na Erucate Heptane PnB 1 -hexanol Water CycloNa2C03 Phase Conductivity Viscosity Z hexane Behavior (μS/cm) (cSt)

Sample

L 5.5 22 22.5 0 49.8 0 0.2 1 p. cl. 1080 8 1800

M-1 5.5 22 17.5 5 50 0 0 LCs na na 1530

M-2 5.44 21.78 17.33 4.95 50.4 0 0.1 1 p. cl. 280 11.5 1670 TABLE 6

Example12 f Na Palmitate Heptane PnB 1 -hexanol Water CycloNa2C03 Phase Conductivity Viscosity Z hexane Behavior (μS/cm) (cSt)

Sample

N-1 5.5 22 22.5 0 49.8 0 0.2 excess oil na na 1910

N-2 5.5 22 22.5 0 49.5 0 0.5 1 p. cl. 6000 na 2330

N-3 5.5 22 22.5 0 49.45 0 0.55 excess water na na 2400

0-1 5.5 22 17.5 5 50 0 0 excess oil na na 1640

0-2 5.5 22 17.5 5 49.8 0 0.2 1 p. cl. 4600 na 1920

0-3 5.5 22 17.5 5 49.7 0 0.3 1 p. cl. 2800 na 2060

0-4 5.5 22 17.5 5 49.65 0 0.35 excess water na na 2130

1 p. cl. = 1 phase clear na=not measured LCs=liquid crystals

TABLE

Example13

Na Myristate Heptane PnB 1 -hexanol Water CycloNa2C03 Phase hexane Behavior

Sample

P-1 5.5 22 22.5 0 49.8 0 0.2 excess oil

P-2 5.5 22 22.5 0 49.4 0 0.6 1 p. cl.

P-3 5.5 22 22.5 0 49.35 0 0.65 excess wat

Q-1 5.5 22 17.5 5 50 0 0 excess oil

Q-2 5.5 22 17.5 5 49.8 0 0.2 1 p. cl.

Q-3 5.5 22 17.5 5 49.65 0 0.35 1 p. cl.

Q-4 5.5 22 17.5 5 49.6 0 0.4 excess wat

R-1 5.5 22 17.5 5 49.65 0 0.35 1 p. cl.

R-2 5 20 15.91 4.54 45.14 9.1 0.31 1 p. cl.

R-3 4.58 18.32 14.58 4.16 41.36 16.7 0.29 1 p. cl.

S-1 7 20 15.5 7.5 50 0 0 LCs

S-2 7 20 15.5 7.5 49.9 0 0.1 LCs

S-3 7 20 15.5 7.5 49.8 0 0.2 1 p. cl.

S-4 7 20 15.5 7.5 49.7 0 0.3 1 p. cl.

S-5 7 20 15.5 7.5 49.6 0 0.4 1 p. cl.

1 p. cl. = 1 phase clear na=not measured LCs=liquid crystals

Claims (32)

WHAT IS CLAIMED IS:

1. A single phase oil continuous microemulsion, comprising:

A. water in an amount not less than about 40 percent by weight and not greater than about 75 percent by weight based on the total weight of the microemulsion;

B. an organic solvent or a mixture of two or more organic solvents, wherein the organic solvent or mixture of organic solvents are characterized as containing no more than 2 weight percent water at about 25°oC when the organic solvent is saturated with water in the absence of surfactants or other additives, and wherein the organic solvent or the mixture of two or more organic solvents are in an amount not less than about 10 percent and not greater than about 60 percent by weight based on the total weight of the microemulsion; and

C. one or more anionic surfactants which are at least partially soluble in the one or more organic solvents, wherein at least one of said anionic surfactants present is selected from the group of aliphatic and alicyclic carboxylic acid salts represented by the formula (R¹- COO)y M where R' is a hydrocarbyl group of 14 to 23 carbon atoms, and has a molecular weight in the range from 225 to about 365 exclusive of the M group, where M is an alkali or alkaline earth metal cation of valence 1 or 2 and where y is the integer 1 or 2, and wherein said anionic surfactants are present in a total amount greater than about 0.1 percent and less than about 10 percent by weight based on the total weight of the microemulsion.

2. The microemulsion of Claim 1 , which is characterized as being an oil continuous microemulsion having an electrical conductivity of less than Z microSiemens/centimeter when measured at use temperatures and a viscosity less than 40 centistokes as measured at use temperatures, wherein Z is represented by the following formula: Z = (1/3)(Φ ²∑ Am,- wherein Φ_w represents the volume fraction of water in the microemulsion, i represents a given electrolyte, Ai represents the molar conductivity of electrolyte i and mi represents the molarity of electrolyte i in the aqueous phase.

3. The microemulsion of the preceding claims wherein the one or more organic solvents is an aliphatic alcohol, an aliphatic ester, an aliphatic hydrocarbon, a chlorinated aliphatic hydrocarbon, an aromatic hydrocarbon, an aliphatic diester, an aliphatic ketone, an aliphatic ether, an alkylene glycol monoether, an alkylene glycol diether, an alkylene glycol ether acetate or combinations thereof.

4. The microemulsion of any of the preceding claims wherein the one or more organic solvents is present in an amount not less than 30 weight percent and not greater than 50 weight percent.

5. The microemulsion of any of the preceding claims wherein water is present in an amount not less than 45 weight percent and not greater than 70 weight percent.

6. The microemulsion of any of the preceding claims where at least one of the anionic surfactants is an anionic surfactant having a molecular weight not less than 250 and not greater than about 345, exclusive of the M counterion.

7. The microemulsion of any of Claim 6 wherein at least one second anionic surfactant is present of formula R_xB-SO₃M wherein R represents alkyl, x is 1 or 2, B is a biradical when x is 1 or is a triradical when x is 2 and which is derived from an aromatic moiety and wherein M represents a cationic counterion and wherein the total number of carbons in Rx is from 18 to 30.

8. The microemulsion of any of the preceding claims wherein the electrical conductivity is less than 0.5 Z microSiemens/centimeter.

9. The microemulsion of any of the preceding claims wherein viscosity is less than 20 centistokes.

10. The microemulsion of any of the preceding claims wherein the electrical conductivity is less than 0.25 Z microSiemens/centimeter.

11. The microemulsion of any of the preceding claims wherein at least one organic solvent is an alkylene glycol monoether.

12. An emulsion, which upon standing at 25° C forms at least two phases wherein one phase is an oil continuous microemulsion, comprising:

A. water in an amount not less than 60 percent by weight and not greater than 95 percent by weight based on the total weight of the emulsion;

B. an organic solvent or a mixture of two or more organic solvents, wherein the organic solvent or mixture of organic solvents are characterized as containing no more than 2 weight percent water at 25° C when the organic solvent is saturated with water in the absence of surfactants or other additives, and wherein the organic solvent or the mixture of two or more organic solvents are in an amount not less than 4 percent and not greater than 40 percent by weight based on the total weight of the emulsion;

C. one or more anionic surfactants which are at least partially soluble in the one or more organic solvents, wherein at least one of said anionic surfactants present is selected from the group of aliphatic and alicyclic carboxylic acid salts represented by the formula (R¹- COO)y M where R' is a hydrocarbyl group of 14 to 23 carbon atoms, and has a molecular weight in the range from about 225 to about 365 exclusive of the M group, where M is an alkali or alkaline earth metal cation of valence 1 or 2 and where y is the integer 1 or 2, and wherein the one or more ionic surfactants are present in a total amount not less than about 0.1 percent and not greater than about 5 percent by weight based on the total weight of the emulsion;

the emulsion characterized as being an oil continuous emulsion, wherein the emulsion has an electrical conductivity of less than Z microSiemens/centimeter when measured at use temperatures and a viscosity less than 40 centistokes as measured at use temperatures, wherein Z is as previously defined.

13. The emulsion of Claim 12 wherein the one or more organic solvents is an aliphatic alcohol, an aliphatic ester, an aliphatic hydrocarbon, a chlorinated aliphatic hydrocarbon, an aromatic hydrocarbon, an aliphatic diester, an aliphatic ketone, an aliphatic ether, an alkylene glycol monoether, an alkylene glycol diether, an alkylene glycol ether acetate or combinations thereof.

14. The emulsion of Claims 12 or 13 wherein the one or more organic solvents is present in an amount not less than 8 weight percent and not greater than 25 weight percent.

15. The emulsion of any of Claims 12-1 wherein water is present in an amount not less than about 70 weight percent and not greater than about 90 weight percent.

16. The emulsion of any of Claims 12-15 wherein the anionic surfactant has a molecular weight not greater than about 345.

17. The emulsion of any of Claims 12-16 wherein the anionic surfactant has a molecular weight not less than 250.

18. The emulsion of Claim 17 wherein at least one additional anionic surfactant is present, of formula R_xB-SO₃M wherein R represents alkyl, x is 1 or 2, B is a biradical when x is 1 or is a triradical when x is 2 and which is derived from an aromatic moiety and wherein M represents a cationic counterion and wherein the total number of carbons in Rx is from 18 to 30.

19. The emulsion of any of Claims 12-18 wherein the electrical conductivity is less than 0.5 Z microSiemens/centimeter.

20. The emulsion of any of Claims 12-19 wherein viscosity is less than 20 centistokes.

21. The emulsion of any of Claims 12-20 wherein the electrical conductivity is less than 0.25 Z microSiemens/centimeter.

22. The emulsion of any of Claims 12-21 wherein at least one organic solvent is an alkylene glycol monoether.

23. The emulsion of any of Claims 12-22 wherein water is in an amount not less than about 80 weight percent and not greater than about 90 weight percent.

24. A cleaning concentrate, which when diluted with water may form the microemulsion of any of Claims 1-11 , which comprises:

A. an organic solvent or a mixture of two or more organic solvents, wherein the organic solvent or mixture of organic solvents are characterized as containing no more than 2 weight percent water at 25° C when the organic solvent is saturated with water in the absence of surfactants or other additives; and

B. one or more anionic surfactants which are at least partially soluble in the one or more organic solvents, wherein at least one of said anionic surfactants present is selected from the group of aliphatic and alicyclic carboxylic acid salts represented by the formula (R¹- COO)y M where R' is a hydrocarbyl group of 14 to 23 carbon atoms, and has a molecular weight in the range from about 225 to about 365 exclusive of the M group, where M is an alkali or alkaline earth metal cation of valence 1 or 2 and where y is the integer 1 or 2, and wherein the one or more anionic surfactants are present in not less than about 0.1 percent and not greater than about 10 percent by weight based on the total weight of the microemulsion.

25. A method for cleaning metal having grease or oily soil on a surface of the metal which comprises applying the microemulsion of any of Claims 1-11 or the emulsion of any of Claims 12-23 to the metal which has grease or oily soil on the surface of the metal to remove at least a portion of the grease or oily soil from the metal surface.

26. The microemulsion of Claim 1 or the emulsion of Claim 12, wherein the carboxylic acid salt, exclusive of the M group has a molecular weight between 250 and 345, the valence of M is 1 and y is the integer 1.

27. The microemulsion or emulsion of Claim 26 wherein the carboxylic acid from which the salt is derived is selected from erucic, oleic and stearic acid.

28. A perturbable composition which comprises:

Component A. an organic solvent or a mixture of two or more organic solvents, wherein the organic solvent or mixture of organic solvents are characterized as containing no more than 2 weight percent water at 25^SC when the organic solvent is saturated with water in the absence of surfactants or other additives; and

Component B. one or more anionic surfactants which are at least partially soluble in Component A., wherein at least one anionic surfactant is selected from the group of aliphatic and alicyclic carboxylic acid salts represented by the formula (R'-COO)y M where R' is a hydrocarbyl group of 14 to 23 carbon atoms, where M is an alkali or alkaline earth metal cation of valence 1 or 2 and y is the integer 1 or 2, and where the salt has a molecular weight in the range from 225 to 365, exclusive of counterion M;

which composition is capable upon addition of electrolyte or low molecular weight hydrocarbon of forming a microemulsion which is characterized as being oil continuous with a conductivity less than Z, said microemulsion comprising:

water present in an amount greater than 45 percent and less than 70 percent, by weight, based on the total weight of the microemulsion;

Component A. present in an amount greater than 15 percent and less than 50 percent, by weight, based on the total weight of the microemulsion; and

Component B. present in an amount greater than 0.1 percent and less than 10percent, by weight, based on the total weight of the microemulsion.

29. The composition of Claim 28 wherein Component A. is an alkylene glycol monoether, and alkylene glycol diether, or combinations thereof.

30. The composition of Claim 28 wherein at least one anionic surfactant of Component B. has a molecular weight greater than 250 and less than 345.

31. A process for preparing an oil continuous microemulsion, comprising the steps of:

Step 1. selecting a perturbable composition of Claim 28,

Step 2. adding to said composition an amount of a salt or other electrolyte sufficient to induce said composition to be converted into an oil continuous microemulsion of conductivity less than Z.

32. The process of Claim 31 , wherein the composition's one or more organic solvents is an alkylene glycol monoether, an alkylene glycol diether, or combinations thereof.