Note: Descriptions are shown in the official language in which they were submitted.
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HIGH WATER CONTENT, LOW VISCOSITY, OIL CONTINUOUS MICROEMULSIONS AN~
EMULSIONS, AN~ 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, microemuisions 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
15 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
30 continuous. Such oil continuous microemulsions are especially suitable to function as
cleaning compositions to remove oil or grease.
Summary of the Invention
3~ This invention, in one respect, is a single phase oil continuous microemulsion
useful as a liquid cleaning composition, comprising:
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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
5 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
lo 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 = (113)(~w)2~;jAjmi, wherein ~w represents the volume fraction of water in the
20 microemulsion, i represents a given electrolyte, Aj 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 2~~C
forms at least two phases wherein one phase is an oil continuous microemulsion,
2s comprising:
A. water in an amount not less than about ~0 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
30 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 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;
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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
5 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 microSiemensfcentimeter
(",uS/cm") when measured at use temperatures and a viscosity less than 40 centistokes
10 ("cSt") as measured at use temperatures, where Z is as described above, represented by the
following formula: Z = (1/3)(q)w)2~jAimj wherein ~ 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 still another respect, this invention is a bicontinuous or water continuous
15 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
20 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
25 365 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 sur~ace of the metal which comprises applying the microemulsion or
30 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
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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
s formulations. The compositions can also be used in industrial coatings and sealants
~pFlic~tions, 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
10 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
15 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
30 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
3s 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 ~0 to
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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
s below Z microSiemens/centimeter wherein Z is represented by the following formula: Z =
(1/3)(~w)2~ ,Ajm, wherein ~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
20 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
2s 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
30 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
35 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.
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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
s 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
lo 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, decahydl~naphLhalene, bicyclohexane,
cyclohexane, and olefins such as 1-decene, 1-dodecene, octadecene, and hexadecene.
Examples of commercially available aliphatic hydrocarbons are NorparTM 12, 13, and 15
(normal paraffin solvents available from Exxon Corporation), Naphtha SC 140 petroleum
till~t~ (also from Exxon), IsoparTM G, H, K, L, M, and V (isoparaffin solvents available from
30 Exxon Corporation), and ShellsolTM 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
35 tetrachloride, chlol~,form, 1,1,1-trichloroethane, perchloroethylene, and trichloroethylene.
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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.
s 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,
lo diisobutyl ketone, methyl isobutyl ketone, and methyl hexyl ketone.
Preferred aliphatic ethers have 4 to 24 carbon atoms. P~epresentative
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
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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
s 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
15 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 ~wo
or more anionic surfactants are employed, "molecular weight" as used above is c~lc~ ted
based on the average of the molecular weights of the two or more anionic surfactants. Often
20 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 (R'
- COO)y M (formula 1) wherein R' represents an olefinically unsaturated or a saturated alkyl,
2s y is 1 or 2, wherein M represents a cationic counterion and wherein the total number of
carbons in R' is from 13 to 23. Preferably R' 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 c~lc~ t~d 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
3s 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,
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and more preferably is selected from sodium, potassium and "onium" (e.g., quat. nitrogen as
in ammonlum, 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
s 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 (~,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 (C,8H~O2); and gorlic acid (C,8H30O2); and
Saturated fatty acids: myristic ~tetradecanoic - C,4H28O2) acid; palmitic (hexadecanoic
C,6H~O2) acid; stearic (octadecanoic - C,8H3~O2) acid; eicosanoic (arachidic - C20H40O2) acid;
and docosanoic (behenic - C22H44O2) acid.
An advantage of using the preferred anionic surfactants is that relatively smallamounts 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 friendlr' 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
30 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,
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sulfonate surfactants of the sulfonated alkylbenzene/toluene/naphthalene-type commonly
available. For example, those represented by the formula RxB-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
5 previously, and wherein the total number of carbons in Rx is from 18 to 30. Molecular weight
of an anionic surfactant of formula RXB-S03M is cz~lc~ ted exclusive of the molecular weight
of counterion M; that is, molecular weight is calculated for RxB-SO~ 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
10 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
15 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
30 alkoxylates can be used. P~ er,ed 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)n-H
wherein R is a hydrocarbon containing 9 to 24 carbon atoms and n is a number averaging
3~ from 1 to 9. Commercially available nonionic surfactants are sold by Shell Chemical
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Company under the name NeodolTM and by Union Carbide Corporation under the name
TergitolTM. Representative examples of preferred commercialiy available nonionicsurfactants include TergitolTM 1 ~-s-series and NeodolTM 91 or 25 series. Additional
representative examples of useful nonionic surfactants include polyoxyethylated
5 polypropylene glycols, polyoxyethylated polybutylene glycols, polyoxyethylated mercaptans,
glyceryl and polyglyceryl esters of natural fatty acids, polyoxyethylenated 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
0 commercially available sacondary aicohol ethoxylates include Tergitol~M ~5-s-3, TergitolTM
1 5-s-5 and TergitolTM 1 5-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-arnino-(3-propionate), and sulfobetaines such as
15 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 foliows 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
20 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 exarnple, 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
2s solution, the instrument is allowed to equilibrate, and the conductivity value observed 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 4û centistokes
30 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
3s than 30 ce, ILi~Lokes, more preferably less than 20 centistokes, and even more preferably
less than 10 centistokes and most preferably less than about 8 centistokes. An advantage
11
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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
5 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
lo 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 c~f 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: (A3 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,
20 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
25 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
30 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 F 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
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low residue and iower 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.
0 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
lo 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 thTs re~sbn, ~he m~s~ efer~d s~tems should ma~.~1~ low ~iseositie;, "ot
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
2s 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
3s 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
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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.
~n1ulsions
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
lo 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
Is 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 A
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
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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
s 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;
I5 (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.
(~)ptionals
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,
30 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,
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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
5 salts and alkyl toluene disulfonate by extraction of a solution ot surfactant in PnB using
aqueous hydrogen peroxide followed by neutralization using aqueous sodium hydroxide.
"PnB" denotes propylene glycol n-butyl ether (DOWANOLTM PnB obtained from The Dow
Chemical Company3, "PnP" denotes propylene glycol n-propyl ether (DOWANOLTM PnP
obtained from The Dow Chemical Company), '~/o" denotes oil continuous microemulsions,
lO "o/w" denotes water continuous microemulsions, Naphtha SC 140 is a commercial petroleum
still~te obtained from Exxon Corporation and ExxalTM 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 sifu, by
neutralization of erucic acid with 5N aqueous sodium hydroxide solution. Similarly, the other
15 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
20 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.
2s
F~rnple 1. Concentrate
A concentrate solution is prepared by mixing 16.2 parts ExxalTM 7 isoheptyl
alcohol with 16.2 parts DOWANOLTM PnP propylene glycol n-propyl ether ("PnP") and 41.7
parts DOWANOLTM 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 concel~LI~te solution may subsequently be "perturbed", by the addition
of electrolyte, water and organic solvent, into a resulting w/o microemulsion of the invention.
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Fxample 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
s excess oil phase, and a conductivity of 4040 microSiemens/centimeter (",uS/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"3 form and resulting sample's conductivity drops to
1770 ~uS/cm (Z =1475). After a total of 1.25 part Na Carb solution is added, a clear, single-
phase microemulsion product forms having 1430,uS/cm conductivity(Z =1490), and after a
total 1.5 part Na Carb solution is added, the resulting clear, singie-phase, bluish water/oil
microemulsion has 430 ~S/cm conductivity(Z = 1590) and a viscosity of 9.7 centistokes
("cSt") measured by Brooicfield LVT viscometer with UL adapter.
Exampie 3. Per[urbabie Microemuision and'v~viO 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 ilS/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 microemuision having a
conductivity of 530 i S/cm (Z = 1472) and a 9.5 cSt viscosity.
F~mple 4. Naphtha-based Product and Perturbable Microemulsion
In the manner of Example 1, a sample is prepared, substituting a petroleum
ti~ te - Naphtha SC 140 supplied by Exxon Chemical, for the previous heptane organic
30 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
~7
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WO98/~4761 PCTAUS97/13145
microemulsion, having conductivity of 44201 S/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
,uS/cm (Z = 1547); 1.75 part Na Carb solution gives an excess water phase milky emulsion
which has conductivity of 1030 I-S/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,uS/cm (Z = 1370) and viscosity
o of 7.5 cSt. It is an exceilent grease removal product.
Example 5. Cleanin~ Process
The 11101uS/cm conductivity, low viscosity w/o microemulsion prepared as
described in Example 4 is contacted with steel coupons coated with Lithium grease in
IS accordance with the standard Conoco cleaning test. Excellent grease removal and cleaning
is observed.
F~mple 6. d-Limonene-based Product
In the same fashion as the preceding examples, a sample is prepared
20 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 I~S/cm conductivity
25 (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 ~uS/cm conductivity (Z = 1573). Further titration to a total of 1 part Na
Carb solution converts the sample to a clear, single-phase wlo microemulsion of 375 ~S/cm
conductivity (Z = 1613~ and having a viscosity of 13.5 cSt.
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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
s varying amounts of the Na Carb, passing through intermediate bicontinuous formulations,
until a clear w/o microemuision 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.
Fxamples 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
15 from Na Carb, n-heptane, PnB, l-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 lZ 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
20 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.
19
CA 02232976 1998-03-25
W O 98/04761 PCT~US97113145
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CA 02232976 1998-03-25
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CA 02232976 1998-03-25
W O98/04761 PCT~US97113145
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CA 02232976 1998-03-25
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