GB2146260A - Water-in-oil emulsions comprising an inverting surfactant - Google Patents

Abstract

The compatibility of an otherwise incompatible inverting surfactant in a water-in-oil emulsion of a water insoluble polymer is improved by incorporating a compatibilizing amount of an N,N-dialkyl amide of a long chain aliphatic compound in the water-in-oil emulsion. The resulting composition comprises (a) a water-in-oil emulsion of droplets of an aqueous liquid and a water-soluble polymer dispersed throughout a continuous oil phase, (b) a normally incompatible inverting surfactant and (c) a compatibilizing amount of an N,N-dialkyl amide of a long chain aliphatic compound. Typically the water-soluble polymer is based on acrylamide or methacrylamide, the oil is a hydrocarbon, and the inverting surfactant is a fatty amide, a sorbitan derivative, an alkali metal salt of a long chain carboxylic acid, or an ethylene oxide/alcohol condensate.

Description

SPECIFICATION Water-in-oil emulsions comprising an inverting surfactant The present invention relates to water-in-oil emulsions of a water-soluble polymer, particularly to water-in-oil polymeric emulsions.

Various water-soluble polymers such as copolymers of acrylamide and acrylic methacrylic acid are useful in a variety of applications such as enhanced or secondary oil recovery of petroleum, flocculation of finely divided solids from aqueous suspensions such as sewage, plating waste, potable water, and the like. These water-soluble polymers are often advantageously prepared as water-in-oil emulsions, i.e., a dispersion of water droplets containing the polymer in a continuous oil phase. In use, the water-in-oil polymer emulsion is inverted, such as by the addition of the emulsion to relatively large amounts of water, to allow the polymer to dissolve in the new continuous water phase and impart a coincident viscosity increase.

Although the polymer emulsions are prepared using an emulsifier (e.g., a surfactant which is commonly soluble in the continuous oil phase), such emulsifiers are often not of a sufficiently high HLB value to effectively cause the inversion of the polymeric emulsion and dissolution of the polymer in water, particularly in the sea or salt water normally encountered in secondary oil recovery operations. Heretofore, to facilitate the inversion of the water-in-oil emulsion and/or dissolution of the water-soluble polymer, several methods have been proposed to increase the overall HLB of the water-in-oil emulsions.

For example, it has been proposed to reduce the amount of the low HLB emulsifiers employed in the preparation of the water-in-oil emulsion. Alternatively, it has been proposed to employ, as the emulsifier used in the preparation of the water-in-oil emulsion, a surfactant having a high as possible HLB value. Unfortunately, these methods have met with limited success since the amounts and/or HLB value of the emulsifiers employed in the preparation of the emulsion are limited by the requirement that a stable water-in-oil emulsion must initially be prepared.

Alternatively, a surfactant having a higher HLB value, a so-called inverting surfactant, has often heretofore been added to the previously prepared emulsion to increase the overall HLB value of the emulsion. This so-called inverting surfactant is particularly necessary to effectively invert the emulsion in the sea or salt waters normally encountered in secondary oil recovery operations. In general, surfactants having HLB values of at least 10 are generally required to achieve the desired invertability while maintaining a reasonable concentration of the inverting surfactant in the emulsion. Unfortunately, many surfactants having the necessary high HLB values are not normally compatible (e.g., insoluble) with the water-in-oil emulsion. Specifically, upon their addition to the emulsion, gel particles are found in the resulting formulation.

Moreover, severe problems are often experienced if the resulting formulations are subjected to repeated freeze-thaw cycling.

In view of these deficiencies in the prior art, it would be highly desirable to provide a water-inoil emulsion containing a surfactant having a sufficiently high HLB to impart to the emulsion the desired ability to invert in sea water or aqueous solutions having high concentrations of salt.

Accordingly, one aspect of the present invention is an improved water-in-oil emulsion of a water-soluble polymer. The improved emulsion comprises (a) a water-in-oil emulsion of droplets of an aqueous liquid and a water-soluble polymer dispersed throughout a continuous oil phase, (b) a normally incompatible inverting surfactant and (c) an N,N-dialkylamide of an acid, preferably an aliphatic acid, having at least 6 carbonatoms, to render the inverting surfactant soluble in the composition.

In another aspect, the present invention is a method for improving the compatibility of an otherwise incompatible inverting surfactant in a water-in-oil emulsion of a water-insoluble polymer, said method comprising incorporating an N,N-dialkylamide, preferably an N,Ndialkylamide of a long chain aliphatic compound, in the water-in-oil emulsion.

In the present invention a solubilizing amount is an amount of the dialkyl amide sufficient to improve the solubility of the otherwise incompatible inverting surfactant in the water-in-oil emulsion. This increased solubility is generally evidence by the reduced formation of gel upon the addition of the inverting surfactant to the water-in-oil emulsion. The use of the dialkyl amide to solubilize the higher HLB surfactant is particularly advantageous since the dialkyl amide does not significantly effect the overall HLB of the resulting emulsion. Therefore, the water-in-oil emulsions containing the inverting surfactant having the higher HLB value rapidly invert in sea water and water of a high concentration of salt. Moreover, the formulations are generally rendered more stable to repeated freeze-thaw cycles.

Water-in-oil emulsions employed in the practice of the present invention are emulsions in which the dispersed phase is an aqueous phase containing a water-soluble polymer and the continuous phase is a water-immiscible, inert liquid. The ratio of the water phase to the oil phase is suitably any ratio that permits the formation of a stable water-in-oil emulsion. Within this constraint, it is generally desirable to minimize the proportion of the oil phase, thereby maximizing the concentration of the water soluble polymer in the emulsion. For similar reasons, it is generally desirable that the concentration of the water-soluble polymer in the disperse.

aqueous phase can be as concentrated as possible without appreciably destabilizing the water-inoil emulsion. Preferably, based on the total volume of the water-in-oil emulsion, the disperse, aqueous phase constitutes from 20 to 80, more preferably from 50 to 78, most preferably from 60 to 75, volume percent and the continuous oil phase constitutes from 80 to 20, more preferably from 50 to 22, most preferably from 40 to 25, volume percent. Preferably, the disperse aqueous phase in the water-in-oil emulsion comprises from 35 to 65, more preferably from 40 to 60, most preferably from 40 to 50, weight percent of the water-soluble polymer.

The water-soluble polymers useful herein are characterized by being at least inherently dispersible and preferably soluble in the disperse aqueous phase and insoluble in the waterimmiscible, inert liquid of the continuous oil phase of the water-in-oil emulsion. The watersoluble polymers advantageously employed are polymers, both homopolymers and copolymers, of a,fi-ethylenically unsaturated carboxamides; vinyl esters of saturated carboxylic acids such as vinyl acetate and vinyl propionate, a,ss-ethylenically unsaturated carboxylic acids and anhydrides such as acrylic acid, methacrylic acid and maleic anhydride; ethylenically unsaturated sulfonic acids such as vinylbenzyl sulfonic acid; and similar water soluble monomers.In addition to the aforementioned water-soluble monomers, the water-soluble polymer may optionally contain a minor amount, e.g., up to about 1 5 mole percent. of a copolymerizable water-insoluble monomer such as monovinylidene aromatic, e.g., styrene; a vinyl halide, e.g., vinyl chloride or vinylidene chloride; and the like.

In general, the water-insoluble polymers useful in preparing the water-in-oil emulsions of the present invention are polymers of an a,ss-ethylenically unsaturated caboxamide wherein at least 1 5 mole percent of the polymerized monomer units (so-called mers) have pendant carboxamide groups.The carboxamide group preferably has the formula:

wherein R3 and R4 are each independently hydrogen; alkyl; aminoalkyl (preferably dialkyl aminomethyl); hydroxyalkyl; or a group of the formula -R5-N+(R6)3X- wherein R5 is alkylene, preferably methylene, each R6 independently is hydrogen, alkyl or hydroxyalkyl and X is a neutralizing anion such as a chloride, bromide, methylsulfate anion or hydroxide; an amine substituted ester for example a quaternary ammonium substituted ester of the chemical formula:

wherein each R7 independently is alkyl and n is an integer from 1 to 4; and the like. Preferably, R3 and R4 are each independently hydrogen or alkyl, most preferably hydrogen.

Preferably, from 50 to 100 mole percent, most preferably from 60 to 100 mole percent of the mers have pendant carboxamide groups. Preferred carboxamide polymers are the polymers of acrylamide and methacrylamide, with the homopolymers of acrylamide and copolymers containing at least 60 moles percent of polymerized acrylamide being especially preferred.

Although the molecular weight of the water-soluble polymer is not particularly critical to the practice of the pesent invention, in general, the water-soluble polymer will have a molecular weight ranging from 10,000 to over 25,000,000, with a weight average molecular weight comonly being in excess of 500,000, more commonly being in excess of 1,000,000.

The continuous oil phase of the emulsion generally comprises a water-immiscible, inert liquid, which is usually an organic liquid such as a liquid hydrocarbon or substituted hydrocarbon liquid. A preferred group of organic liquids are the liquid hydrocarbons having from 4 to 1 5 carbon atoms including aromatic and aliphatic hydrocarbons and mixtures thereof such as benzene, xylene, toluene, mineral oils, liquid paraffins, e.g., kerosene, naphtha and the like.

Methods for preparing the water-in-oil emulsions of the water-soluble polymers are well-known in the art and reference is made thereto for the purpose of this invention. lilustrative of such techniques are described in U.S. Patent Nos. 3,284,393: 3,624,019 and 3,734,873, all of which are hereby incorporated by reference. In general, the water-in-oil emulsions are prepared by dispersing an aqueous solution of the monomer in an inert hydrophobid liquid organic dispersing medium containing a sufficient amount of water-in-oil emulsifying agent (conventionally and hereinafter referred to as a "primary emulsifier") and the resulting emulsion heated under free-radical forming conditions to polymerize the monomer in the disperse phase.

In general, the primary emulsifiers are oil-soluble surfactants which permit the formation of a water-in-oil emulsion. The oil-soluble primary surfactants generally have a hydrophilic-lipophilic balance (HLB) from 3 to 9, preferably from 4 to 8. MCCutcheon's Emulsifiers and Detergents, International Edition, 1981, ppg 248-253 sets forth a number of illustrative examples of surfactants having HLB values with these desired ranges.

Of the surfactants having the desired HLB values, the surfactants advantageously employed as the primary emulsifiers are the anionic and nonionic surfactants.

Representative anionic surfactants include the fatty amides (substituted or unsubstituted) wherein the fatty groups contain from 15-22 carbon atoms such as the N,N-dialkanol substituted fatty amides wherein the alkanol group contains 2-6 carbon atoms; the sorbitan derivatives such as sorbitan monooleate and sorbitan monostearate and various alkali metal salts of a long chain carboxylic acid. Representative nonionic surfactants include the condensation products of higher fatty alcohols with a limited number of moles of ethylene oxide such as the reaction product of a mole of oleyl alcohol or lauryl alcohol with 2 or 3 moles ethylene oxide.

Combinations of two or more surfactants may be employed.

Preferably, the emulsifying surfactant is a sorbitan derivative, particularly sorbitan monooleate, or a combination thereof with the amide reaction product of oleic acid with isopropanol amine.

The primary emulsifiers are employed in an amount sufficient to form a desirably stable waterin-oil emulsion. In general, such an amount of emulsifying agent is within the range from about 0.1 to about 29, preferably from 1.5 to 3, weight percent based on the weight of the aqueous phase of the water-in-oil emulsion.

As used herein, the term "inverting surfactant' refers to a surfactant capable of facilitating the inversion of the water-in-oil emulsion, upon the dilution of the emulsion in water. This generally results in an increase in the viscosity of the resulting mixture. By facilitating the inversion of the water-in-oil emulsion, it is meant that, upon the addition of sufficient amounts of water to invert an emulsion containing the inverting surfactant, the water-soluble polymer in the disperse aqueous phase of the water-in-oil emulsion more rapidly becomes dissolved in the continuous water phase than if no inverting surfactant was present in the emulsion being inverted.Although any surfactant which facilitates the aforementioned inversion is usefully employed herein, in general, the inverting surfactant will possess an HLB value from 8 to 25, preferably from 10 to 20, more preferably from 11 to 1 8. Such inverting surfactants are well-known in the art and reference is made thereto for the pruposes of this invention. Representative inverting surfactants include certain reaction products of an alkylene oxide such as ethylene or propylene oxide with an alkylated phenol or long chain (e.g., from 6 to 20 carbon atoms) fatty alcohol, fatty acid, alkyl mercaptan or primary amine; the dialkyl diphenol ether sulfonates; and the like.

In the practice of the present invention, the inverting surfactant is a surfactant which is not entirely compatible with the water-in-oil emulsion. Such incompatibility is evidenced by the formation of at least some gel upon their admixture. Typically, these surfactants will exhibit an HLB value of at least 12, more typically of at least 1 3. Of such inverting surfactant, those most advantageously employed will depend on a variety of factors including the individual components of the water-in-oil emulsion, including the primary emulsifier and the specific water-insoluble polymer and the like. Preferably, the inverting surfactants are nonionic.More preferably, the inverting surfactants are the alkylphenol ethoxylates having 10-16 moles of ethylene oxide per mole of alkylphenol and fatty alcohol ethoxylates, particularly linear secondary alcohols having from 11 to 1 5 carbon atoms with from 9 to 1 2 moles of ethylene oxide per mole of the alcohol. Most preferred inverting surfactants are octyl or nonylphenyl ethoxylates.

The inverting surfactant is employed in an amount sufficient to facilitate the inversion of the water-in-oil emulsion, with the inverting surfactant advatageously being employed in an amount from 0.1 to 15, preferably from 0.5 to 5, weight percent based on the total weight of the waterin-oil emulsion.

The N,N-dialkyl amides useful in the practice of the present invention are represented by the structural formula:

wherein R is an alkyl, alkenyl, cycloalkyl or aryl group, or an inertly substituted alkyl, alkenyl, cycloalkyl or alkyl group, or mixtures of two or more thereof and has at least 6 carbon atoms and R' and R2 are each independently an alkyl group. R is preferably an aliphatic group and more preferably, R' and R2 are each independently methyl or ethyl and each R is a straight or branched chain alkyl group having from 6 to 18 carbon atoms. The most preferred N,N-dialkyl amides are represented by the following structural formula:

wherein n is an integer from 4 to 16, preferably from 4 to 1 0.

The N,N-dialkyl amide is employed in a compatibilizing amount. Specifically, the dialkyl amide is employed in an amount sufficient to reduce the formation of gel or other evidence of insolubility upon the addition of the inverting surfactant to the emulsion, i.e., less gel is formed upon the addition of the inverting surfactant to the water-in-oil emulsion when a dialkyl amide is employed than when no dialkyl amide is used.Preferably, the N,N-dialkly amide is employed in an amount such that there is no gel formation upon the addition of the otherwise incompatible, inverting surfactant to the emulsion, i.e., the normally incompatible inverting surfactant is rendered soluble or at least dispersible, as colloidal sized particles, in the emulsion, Although the compatibilizing amounts of the N,N-dialkyl amide will vary depending on a variety of factors including the specific water-soluble polymer, its concentration, the type and concentration of the other components of the water-in-oil emulsion and the like, in general, to compatibilize an otherwise incompatible, inverting surfactant, the dialkyl amide is generally employed in an amount from 0.1 to 20, preferably from 0.5 to 5, weight percent based on the weight of the water-in-oil emulsion.Most preferably, the dialkyl amide is employed at about the same concentration as the inverting surfactant.

In general, in addition to solubilizing an otherwise incompatible, inverting surfactant, the dialkylamide will improve the low temperature properties, such as freeze-thaw stability, of the resulting water-in-oil emulsion. Specifically, in many instances, a water-in-oil emulsion containing an inverting surfactant will exhibit gel formation, skin formation and/or solidification upon repeated cycles of freeze-thaw. In such case, the N,N-dialkyl amide will often reduce the amount of gel or skin formation upon exposure of the water-in-oil emulsion containing the inverting surfactant to repeated freeze-thaw cycles. (See, for example, the test methods described in Example 1).In addition, the emulsions containing the N,N-dialkyl amide are often flowable at lower temperatures, e.g., - 20'C, than an identical emulsion except containing no N,N-dialkyl amide.

In preparing the water-in-oil emulsion of the present invention, a compatibilizing amount of the N,N-dialkyl amide, water-in-oil emulsion and the inverting surfactant are admixed. In general, an amount of the dialkyl amide sufficient to render the inverting surfactant sufficiently compatible in the water-in-oil emulsion is advantageously admixed with the inverting surfactant and the resulting admixture subsequently added to the water-in-oil emulsion. Alternatively, a compatibilizing amount of the dialkyl amide can be added to the water-in-oil emulsion and the otherwise incompatible, inverting surfactant subsequently added thereto.

In general, the blending or admixing of the dialkyl amide and inverting surfactant in the water-in-oil emulsion is advantageously conducted using mild agitation sufficient to uniformly disperse, which term includes solubilizing, the inverting surfactant and dialkyl amide in the water-in-oil emulsion. The resulting emulsion is a fluid liquid which can easily be poured or pumped. It can rapidly be converted for use by adding it to an aqueous medium, including an aqueous liquid containing a high concentration of salt, such that it inverts to form an aqueous solution of the water-soluble polymer.

The following examples are set forth to illustrate the invention and should not be construed as limiting its scope. All parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1 A water-in-oil emulsion of a water-soluble polymer comprising, in polymerized form, 70 percent acrylamide and 30 percent acrylic acid is prepared using the polymerization techniques and conditions as described in U.S. Patent No. 3,284,393. The water-in-oil emulsion comprises 27 percent of a continuous oil phase comprised of Isopar M (a mixture of isoparaffinic hydrocarbons having a flash point of 77"C) and oil-soluble, primary emulsifiers. The oil-soluble, primary emulsifiers contained by the emulsion are sorbitan monooleate and oleic isopropanolamide. The discontinuous aqueous phase comprises the remainder of the water-in-oil emulsion and is composed of about 40 percent of the water-soluble polymer based on the total weight of the discontinuous aqueous phase.

To a part of the water-in-oil emulsion is added 4 percent, based on the weight of the water-inoil emulsion, of a mixture containing equal parts of (1) an inverting surfactant of an octylphenol (HLB = 15.8) condensed with 1 6 moles of ethylene oxide per mole of octylphenol and (2) an N,N-dimethyl amide composition comprised of 50 percent N,N-dimethyl caprylamide, 40 percent N,N-dimethyl capramide, 5 percent N,N-dimethyl caproamide and 5 percent N,N dimethyl lauramide. This addition is conducted using mild agitation. No gel is exhibited upon this addition of the subsequent solubilization of the mixture in the oil phase of the water-in-oil emulsion.

A portion of the water-in-oil emulsion formulation (Sample No. 1) is tested for its ability to invert in an aqueous solution having a high salt concentration by placing the resulting emulsion in synthetic sea water containing an additional 3 percent potassium chloride. The emulsion formulation formed a good initial dispersion. This dispersion is mildly agitated using a paddle stirrer for thirty minutes and at the end of this period, the viscosity increase of the salt water containing the emulsion is measured using a Brookfield viscometer with Spindle No. 1 at 100 rpm and found to be 35 centipoise (cps).

A second portion of the resulting water-in-oil emulsion formulation is subjected to three repeated freeze-thaw cycles, each cycle consisting of exposing the formulation for 22 hours to - 200"C, followed by exposing the formulation to ambient temperatures, i.e., from 1 8 to 25"C, for 2 hours. The condition of the emulsion formulation is inspected at the end of each cycle (i.e., at the end of the thaw portion of each cycle). During each cycle and at the end of the three cycles, the water-in-oil emulsion formulation (returned now to room temperature) is found to maintain its fluidity with no gel being formed.

Comparative Example I To a second part of the original water-in-oil emulsion is added 2 percent, based on the weight of the water-in-oil emulsion, of the inverting surfactant of the dioctylphenol/ethylene oxide condensation product (no dialkyl amide is employed). Significant amounts of small gel particles are noted upon the addition of the inverting surfactant to the water-in-oil emulsion. Upon evaluating the resulting formulation's resistance to repeated freeze-thaw cycles by the aforedescribed testing methods, due to the instability of the emulsion, the formulation was found to become a rubbery lump during the freeze portion of the first cycle. The emulsion remains as a lump at room temperature.

EXAMPLE 2 In a manner similar to that of Example 1, a series of water-in-oil emulsion formulations (Sample Nos. 2-4, respectively) are prepared by adding 2, 3 and 5 percent, based on the weight of the water-in-oil emulsions, of a mixture containing equal parts of the octylphenol ethoxylate inverting surfactant and the N,N-dialkyl amide to separate portions of the water-in-oil emulsion. Each of the samples is formulated without the formation of any gel particles, thereby indicating that the N,N-dialkylamide has made it possible to effectively solubilize the otherwise incompatible inverting surfactant, at various concentrations, in a water-in-oil emulsion.

Upon the addition of each formulation to separate synthetic sea water solutions containing an additional 3 percent potassium chloride, all the formulations formed a good initial dispersion.

The viscosity of each of the resulting sea water solutions containing the polymer is measured 30 minutes after initial mixing of each of the emulsions with the seawater. The viscosity of the seawater containing 2 percent of the mixture (1 percent of the inverting surfactant) (Sample No.

2) is found to be only 1 centipoise, indicating that the polymer has not been effectively dissolved. The viscosity of the seawater containing 3 percent of the mixture (1.5 percent of the inverting surfactant) (Sample No. 3) is 14.5 centipoise. The viscosity of the seawater containing 5 percent of the mixture (2.5 percent of the inverting surfactat) (Sample No. 4) is 33.5 centipoise.

Moreover, when subjected to three repeated freeze-thaw cycles, all formulations remained fluid (i.e., flowable throughout). In addition, no gel particles are found in the formulations containing 2 or 3 percent of the surfactant/dialkyl amide mixture. The formulation containing 5 percent of the mixture exhibits slight gel formation following the second freeze-thaw cycle.

Although emulsion formulations can be prepared using 1 percent of the surfactant/dialkyl amide mixture, the formulation does not exhibit viscosity increases upon inversion.

An emulsion formulation can also be prepared using 6 percent of the surfactant/dialkyl amide mixture. However, the resulting emulsion quickly inverted without addition of more water and subsequently gelled into a rubbery mass without exposure to low temperatures.

Comparative Example 2 Several water-in-oil emulsion formulations (Samples Nos. 2a, 3a, 4a and 5a) are prepared by adding 1, 1.5, 2.5 and 3 percent, based on the total weight of the water-in-oil emulsion, of the octylphenol based inverting surfactant to the water-in-oil emulsion. Regardless of the amount of the inverting surfactant being added to the emulsion, a significant number of small gel particles are formed upon the preparation of each emulsion formulation. In addition, when subjected to repeated freeze-thaw cycles, all formulations become solid (non-flowable) at the lower temperature. On returning to room temperature, the emulsion formulation containing 1 percent of the inverting surfactant (Sample No. 2a) is fluid but exhibited small gel particles in the first and subsequent cycles.The emulsion formulation containing 1.5 percent of the inverting surfactant (Sample No. 3a) was also fluid at room temperature but exhibited larger gel lumps after the second and third cycles. The formulations containing 2.5 and 3 percent of the inverting surfactant (Samples Nos. 4a and 5a, respectively) remained non-flowable (a rubbery lump) after the freeze portion of the first cycle and did not thereafter become fluid.

EXAMPLE 3 In a manner similar to Examples 1 and 2, a water-in-oil emulsion formulation (Samples No. 6) is prepared by the addition of 5 percent, based on the total weight of the water-in-oil emulsion, of an admixture comprising equal parts of an inverting surfactant of a nonylphenol (10) ethoxylate sold as Dowfax 9N 10 by The Dow Chemical Company (HLB = 13.5) and the N,Ndimethyl amide mixture employed in Example 1 to the water-in-oil emulsion. The formulation is prepared with no gel formation. In addition, when the formulation is subjected to three repeated freeze-thaw cycles, the emulsion remains fluid througout. Similar results are obtained using 6 weight percent of the nonylphenol ethoxylate surfactant/N,N-dialkyl amide mixture.

Comparative Example 3 The nonylphenol (10) ethoxylate is added (without the N,N-dialkylamide) to an identical waterin-oil emulsion at a concentration of 2.5 percent based on the weight of the emulsion. Upon said addition, numerous small gel particles are formed. In addition, when the resulting formulation is subjected to repeated freeze-thaw cycles, the formulation becomes solid beginning with the second cycle without thereafter becoming fluid at room temperatures. Similar results are obtained using 3 percent of the nonylphenol ethoxylate inverting surfactant.

Example 4 A water-in-oil emulsion is prepared in a manner similar to Example 1 except that, following preparation, a mixture of sodium carbonate and sodium bisulfate is post-added to the emulsion.

To a portion of the resulting emulsion is added 3 percent, based on the weight of the emulsion, of a mixture comprised of equal parts of an octylphenol (12-13) ethoxylate available as Triton X-102 from Rohm 8 Haas (HLB = 14.6) and a N,N-diaikyl amide mixture identical to that employed in Example 1 (Sample No. 7). The emulsion formulation is prepared without the formation of gel particles or other evidence of incompatibility of the inverting surfactant in the emulsion. Similar excellent compatibility is exhibited with an emulsion formulation (Sample No.

8) prepared by the addition of 4 percent of a mixture of equal parts of an octylphenol (9-10) ethoxylate available as Triton X-100 from Rohm 8 Haas (HLB = 13.5) and the dialkyl amide to the emulsion.

For purposes of comparison, when the Triton X-102 inverting surfactant only is added to another portion of the resulting emulsion (Sample No. 7aG), the resulting emulsion formulation exhibits a number of small gel particles due to the incompatibility of the surfactant in the emulsion.

When subjected to three repeated freeze-thaw cycles, the emulsion formulations (Sample Nos.

7 and 8) containing the inverting surfactant and a dialkyl amide remained fluid without gel formation after three freeze-thaw cycles. Alternatively, formulations which contain only the inverting surfactant are solid or nearly solid after the first cycle.

EXAMPLE 5 A series of water-in-oil emulsion formulations (Sample Nos. 9-16) are prepared by admixing a water-in-oil emulsion identical to the emulsion employed in Example 4 with equal parts of an inverting surfactant of an octylphenol (16) ethoxylate having a calculated HLB value of 1 5.8 and the N,N-dialkly amide specified in the accompanying Table I.

For purposes of comparison, water-in-cil emulsion formulations (Sample Nos. 9a, 1 Oa and 11 a) are prepared by adding, to the water-in-oil emulsion, 1, 2 and 3 percent, based on the weight of the water-in-oil emulsions, of the octylphenol (16) ethoxylate inverting surfactant without the aid of the dialkyl amide.

The amounts of gel formed upon the initial addition of the surfactant to each of the water-inoil emulsion is observed. In addition, each of the formulations is subjected to freeze-thaw testing. The ability of each formulation to invert upon the addition of the emulsion formulations to distilled water and sea water having an additional 3 percent potassium chloride is also determined. The results of this testing are summarized in the accompanyiaig Table I.

TABLE I N,N-Dialkyl Amide (1) Freeze-Thaw Evaluation (3) Inversion (4) Sample Gel Form- distilled No. Type Amount ation (2) 1st cycle 2nd cycle 3rd cycle water sea water 9 M12 1 n.g. fluid fluid fluid poor poor 10 M12 2 n.g. fluid fluid slt.gel fair-ppt. fair 11 M12 3 n.g. slt.get slt.gel gel fair-ppt. fair-ppt.

12 M18-OL 1 n.g. fluid fluid fluid poor poor 13 M18-OL 1.5 n.g. fluid fluid fluid poor poor 14 M18-OL 2 n.g. fluid fluid fluid poor fair 15 M18-OL 2.5 n.g. slt.gel slt.gel slt.gel good-ppt. good-ppt.

16 M18-OL 3 n.g. akin akin akin good-ppt. good-ppt.

9A+ - - gel slt.gel slt.gel gel - 10A+ - - gel solid solid solid - 11A+ - - gel solid solid solid - + Not an example of the present invention.

1) The type of N,N-dialkyl amide is given in abbreviated form with M12 = N,N-dimethyl lauramide (95%) sold as Hallcomid TM M12 by the CP Hall Co.

M18 = N,N-dimethyl oleamide (80%) sold as Hallcomid TM M18-OL by the CP Hall Co.

2) Gel formation refers to the amounts of gel formed upon the addition of the inverting surfactant (or mixture thereof with the N,N-dialkyl amide to the water-in-oil emulsion with n.g. indicationg no gel and gel indicationg that at least small gel particles are formed upon the addition of surfactant to the water-in-oil emulsion.

3) Freeze-thaw testing is conducted by the methods described in Example 1. Examination of the samples after each freeze-thaw cycle (i.e., after the thaw portion of each cycle just prior to subjecting the sample to the freeze portion of the next cycle) is determined and the condition indicated wherein:: "fluid" - a fluid formulation having no gel "skin" - a fluid formulation exhibiting some skin "slt.gel" - a generally fluid formulation having slight gel "gel" - a formulation which is still fluid but having more gel and generally larger gel particles.

"solid" - non-flowable formulation 4) Inversion relates to the ability of the emulsion to invert before freezing as evidenced by separation or precipitation of the polymer from the aqueous medium upon the addition to water and the viscosity increase of the resulting mixture with: poor - little viscosity increase within 30 minutes after the addition of the emulsion formulation to the distilled or sea water.

fair - fair dispersion accompanied by little or some viscosity increase 30 minutes after inversion fair-ppt. - same as fair except some to most of the polymer precipitates from solution upon inversion good - a good dispersion usually accompanied by a corresponding viscosity increase thirty minutes after adition of the emulsion formulation to the distilled water or sea water good-ppt. - same as good except some polymer lumps are noted upon inversion.

For practical reasons, those formulations which could not be formulated without gel formation are not tested for invertability.

As evidenced by the data presented in Table I, the formulations containing the inverting surfactant and any of the various, specified dialkyl amides exhibit essentially no gel formation upon the addition of the otherwise incompatible inverting surfactant to the water-in-oil emulsion.

Alternatively, when the inverting surfactant is added to the emulsion without the dialkyl amide, gel formation is noted. Moreover, when subjected to repeated freeze-thaw cycles, the emulsion formulations of the present invention which contain the combination of a dialkyl amide and the inverting surfactant show generally better performance than those formulations containing only the inverting surfactant.

Each of several formulations identical to Sample No. 1 6 except containing, as the inverting surfactant, Dowfax 9N10 or Triton X-1 14 exhibit similarly improved performance.

Comparative Example 4 Butanol, which is known to be capable of coupling alkylphenol ethoxylate surfactants having high HLB values in aliphatic oiis, was mixed, at equal parts, with Triton X-165 inverting surfactant. This mixture was found to be soluble in kerosene, an oil commonly employed in the preparation of water-in-oil polymeric emulsions. However, when the mixture of the inverting surfactant and butanol was added to the water-in-oil polymeric emulsion prepared by the techniques described in Example 1, immediate and significant gel formation was exhibited.

Comparative Example 5 A mixture of sorbitan monooleate surfactant available as Span 80 from Atlas Chemie and having a relatively low HLB value (HLB = 4.3) is mixed with equal parts of Triton X-165 inverting surfactant. Several emulsion formulations are prepared from an emulsion identical to the emulsion employed in preparing Sample No. 1 by adding various amounts (2, 4, 6 and 8 percent based on the total weight of the water-in-oil emulsion) of a mixture of equal parts of the inverting surfactant and the lower HLB surfactant. No gel formation is evidenced upon the addition of the mixture to the emulsion. When subjected to three repeated freeze-thaw cycles, each of the resulting emulsion formulations, although becoming non-fluid during the freeze portion, reverted to a fluid with no gel formation being evidenced after each thaw portion of the cycle.However, due to the relatively low HLB value of the emulsion, no viscosity increase was noted upon the addition of each of these emulsions to either distilled water or sea water containing an additional amount of potassium chloride.

Comparative Example 6 Similar results as obtained in Comparative Example 5 are obtained when mixtures containing equal amounts of the inverting surfactant and a diethanolamide of C15-C22 fatty acids are added to the water-in-oil emulsion at concentrations of 2, 4, 6 or 8 percent based on the weight of the water-in-oil emulsion. Specifically, no gel formation is noted upon the addition of the mixture to the emulsion. In addition, the resulting emulsion formulations, although becoming non-fluid during the freeze portion, reverted to fluids having no gel after the thaw portion of each cycle.

However, no viscosity increase was noted thirty minutes after initial addition of the emulsion to either distilled water or sea water.

Comparative Example 7 When from 1 to 6 percent baes on the weight of the emulsion of a mixture of equal parts of lauryl alcohol, a known coupling agent, and the inverting surfactant employed in Comparative Example 4 are added to the water-in-oil emulsion identical to that of Example 1, no gel formation is exhibited. Although resulting formulations solidify at the lower temperatures encountered during the freeze portion of each freeze-thaw cycle during freeze-thaw testing, they revert to fluids upon reexposure to room temperatures. However, a relatively poorer inversion and lower increases in viscosity are experienced due to the low HLB of the formulations.

Similarly, poorer invertibility is exhibited by an emulsion having from 1 to 6 weight percent of a mixture of equal parts lauryl alcohol and an octylphenol ethoxylate sold as Triton X-114 by Rohm 8 Haas added thereto.

Comparative Example 8 The addition of 0.5 percent of the N,N-dialkyl amide of Example 1 to a vvater-in-oil emulsion identical to that of Example 1 does not visibly affect the emulsion. Upon extended exposure to temperatures of - 20"C, the formulation solidifies but reverts to a fluid upon exposure to room temperature (i.e., during the thaw portion of each cycle). However, the inversion and dissolution of the polymer upon addition of added amounts of KC1 is not significantly improved by the NtN-dialkyl amide. Similar results are obtained with emulsion formulations prepared from 1 to 3 percent of the dialkyl amide.

Example 6 A water-in-oil emulsion of a water-soluble polymer comprising, in polymerized form, 25.5 percent acrylamide and 74.5 percent of a quaternized dimethylamino ethylmethacrylate is prepared using the polymerization techniques and conditions as described in U.S. Patent No.

3,284,393. The water-in-oil emulsion comprises 27 percent of a continuous oil phase comprised of Isopar M (a mixture of isoparaffinic hydrocarbons having a flash point of 77"C and oil soluble primary emulsifiers). The oil-soluble, primary emulsifiers contained by the emulsion are sorbitan monooleate, an alcohol (7) ethoxylate and the reaction product of oleic acid with isopropanol amide. The discontinuous aqueous phase comprises the remainder of the water-inoil emulsion and is composed of about 57 percent of the water-soluble polymer based on the total weight of the discontinuous aqueous phase.

A series of water-in-oil emulsion formulations are prepared by adding to separate portions of the water-in-oil emulsion 3, 4, 5, 5.6 and 6 percent based on the weight of the water-in-oil emulsion, of a mixture containing equal parts of (1) an inverting surfactant of an octylphenol condensed with 1 6 moles of ethylene oxide per mole of octylphenol (HLB = 15.8) and (2) an N,N-dimethyl amide composition comprised of 50 percent N,N-dimethyl caprylamide, 40 percent N,N-dimethyl capramide, 5 percent N,N-dimethyl caproamide and 5 percent N,Ndimethyl lauramide. This addition is conducted using mild agitation. No gel is exhibited upon the preparation of the emulsion formulations.

A portion of each of the resulting water-in-oil emulsion formulations is subjected to three repeated freeze-thaw cycles. Although the emulsion formulation containing 3 percent of the surfactant/N,N-dialkyl amide solidified during the freeze cycle, upon subsequent thawing to room temperature, the emulsion formulation reverted to a stable water-in-oil emulsion which exhibits no gel particles. The emulsion formulations having the higher amounts of the mixture are all fluid throughout the three freeze-thaw cycles.

Example 7 A series of water-in-oil emulsion formulations are prepared by adding to separate portions of a water-in-oil emulsion (identical employed to the emulsion in Example 6 except prepared using the reaction product of oleic acid with isopropanol amide as the sole primary emulsifier) 2 and 3 percent, based on the weight of the water-in-oil emulsions, of a mixture containing equal parts of an alcohol (9) ethoxylate sold as 15-59 by BP (HLB = 13.5) and the N,N-dialkyl amide identical to that employed in Example 1. The formulations are formed without the presence of gel being exhibited.

A portion each of the resulting formulations is added to synthetic sea water containing an additional 3 percent potassium chloride. The formulation exhibited excellent inversion with coincident viscosity increase. A formulation containing only 1 percent of the surfactant mixture can be prepared without gel formation but shows poor invertability with the formation of lumps upon its addition to the sea water containing 3 percent added potassium chloride. A formulation containing 4 percent of the surfactant mixture is formed without gel. However, it precipitated upon addition to the sea water containing 3 percent added potassium chloride. The addition of the 15-59 surfactant at a concentration from 0.5-2 percent based on the weight of the waterin-oil emulsion (without using the N,N-dialkyl amide) exhibits gelling and the formation of lumps. In addition, none of the resulting formulations can be effectively inverted in either distilled water or sea water.

Claims (14)

1. A water-in-oil emulsion composition comprising a water soluble polymer, an inverting surfactant which is normally incompatible in the water-in-oil emulsion and an N,N-dialkyl amide of the formula:

wherein R is an alkyl, alkenyl, cycloalkyl, or aryl group, or an inertly substituted alkyl, alkenyl, cycloalkyl or aryl group, and has at least 6 carbon atoms, R' and R2 are each independently an alkyl group.

2. A composition as claimed in Claim 1, wherein R contains from 6 to 18 carbon atoms.

3. A composition as claimed in Claim 1 wherein the HLB of the inverting surfactant is at least 12.

4. A composition as claimed in any one of the preceding claims, wherein the N,N-dialkyl amide has the formula:

in which n is an integer from 4 to 1 6.

5. A composition as claimed in Claim 4 wherein n is an integer from 4 to 10.

6. A composition as claimed in any one of the preceding claims wherein the N,N-dialkyl amide and the inverting surfactant are each employed in an amount from 0.5 to 5 weight percent, based on the weight of the water-in-oil emulsion.

7. A composition as claimed in any one of the preceding claims wherein the inverting surfactant is an alkylphenol ethoxylate or a fatty alcohol ethoxylate.

8. A composition as claimed in any one of the preceding claims, wherein the inverting surfactant is an octyl or nonyl phenol ethoxylate or an ethoxylated derivative of a linear secondary alcohol having from 11 to 1 5 carbon atoms containing from 9 to 1 2 moles of ethylene oxide units per mole of alcohol.

9. A composition as claimed in any one of the preceding claims, wherein the water soluble polymer is homo-or copolymer of an a,ss-ethylenically unsaturated carboxamide.

10. A composition as claimed in any one of the preceding claims, wherein the inverting surfactant and N,N-dialkyl amide are employed in approximately equal concentrations by weight.

11. A method for improving the solubility of an otherwise insoluble inverting surfactant in a water-in-oil emulsion of a water-soluble polymer, which method comprises incorporating in the emulsion an N,N-dialkyl amide.

12. A method as claimed in Claim 11 wherein the inverting surfactant and N,N-dialkyl amide are mixed and the resulting mixture added to the water-in-oil emulsion.

1 3. A water-in-oil emulsion composition substantially as hereinbefore described with reference to the foregoing specific Examples.

14. A method of forming, a water-in-oil emulsion, substantially as hereinbefore described with reference to the foregoing specific Examples.