COMPOSITIONS FOR MAKING STABLE EMULSIONS AND DISPERSIONS

Abstract: An adjuvant containing iota-carrageenan, a gel-inducing cation which is ammonium, potassium, calcium, barium, or magnesium, and selected anionic, non-ionic or amphoteric surface-active agents when mixed with water and with water-insoluble liquids or low melting solids forms a concentrated emulsion containing 1%-45% or more by volume of dispersed phase and having a viscosity less than 2, 000 mPa.s at room temperature which is stable during storage at room temperature, dilutable with water without loss of stability, and stable to multiple freeze-thaw cycles.

Description: COMPOSITIONS FOR MAKING STABLE EMULSIONS AND DISPERSIONS The invention relates to an adjuvant which in aqueous form can be mixed with materials which are water-insoluble liquids or par iculate solids to form aqueous emulsions having a unique combination of properties. It has previously been known that surface active agents can be used as adjuvants to water wherein insoluble oils or particulate solids may be minutely dispersed to form emulsions. These emulsions have been found useful in numerous commercial products due to the beneficial delivery of the dispersed material in a form which retains the physical handling properties of an aqueous solution but they lack the combination of stability with low viscosity which characterizes emulsions made with the adjuvant of the present invention. It also has been known that the stability, or resistance to separation of such emulsions may be enhanced by thickening the aqueous phase, also known as the continuous or external phase, with thickeners to inhibit the collision of the particles of the dispersed phase, also known as the discontinuous or internal phase. Inhibition of such collisions lessens the likelihood of merger or coalescence of the dispersed particles into larger particles, which coalescence leads to complete separation. Thickening the aqueous external phase also has been known to inhibit the settling or creaming of the dispersed particles which is caused by differences between the specific gravities of the internal phase and the external phase of the emulsion. In prior art, the thickeners used to inhibit separation have included vegetable gums and clays, including gelatin, cellulose derivatives, gum tragacanth, gum acacia, sodium alginate, Irish Moss and its extractive gums, kappa-carrageenan and lambda-carrageenan. These thick- eners have usually been used in combination with surface active agents. However, the introduction of such thick¬ eners in an amount sufficient to provide a substantial increase in stability has necessarily greatly increased the viscosity of the emulsion so that it is no longer useful for many of the purposes of the emulsion before thickening. It has also been known that an aqueous thixo- tropic gel useful as a vehicle for dispersed substances may be prepared with a composition consisting essen- tially of iota-carrageenan, a sequestrant for calcium, and a water-soluble compound of calcium which slowly dissolves in water and releases calcium ions as described in Stancioff et al. U.S. Patent No. 3,562,176 issued February 9, 1971. However, dispersions made with such gels lack the stability properties of emulsions made in accordance with the present invention. It has also been known that enhanced emulsion stability can often be achieved by use of combinations of two or more different surface active agents. These surface active agents may be of similar chemical struc¬ ture, or may vary considerably. In this regard, the surface activity of soaps, such as potassium oleate, has been known to be enhanced by use in combination with long-chain aliphatic alcohols, resulting in con- siderably increased emulsifying ability, as taught by Prince, in Emulsions and Emulsion Technology, Part 1, Lissant, ed., 148-153, (1974). However, the increased stability of emulsions provided by such combinations falls short of that provided by the present invention. Emulsions in which water is the external phase are used in many commercial products and may be desired to have a wide range of physical properties. These properties may be related to aesthetic appeal, ease and safety of use, and efficiency. In the field of agricultural chemicals, such as pesticides, insecti¬ cides and herbicides, aqueous emulsions are often -BΛJRE-A OMPI superior to hydrocarbon-based solutions, due to decreased flammability and decreased phytotoxicity. Emulsions of such agricultural chemicals may also need to be stable, not exhibiting coalescence or separation of the dispersed phase for several months whether stored at moderate temperatures (20 * to 30 * C) or subjected to repeated freezing and thawing, as may occur in the field. Such aqueous emulsions often need to have low viscosity, less than 2,000 mPa-s (milli Pascal seconds) at 20 β C. as determined with a Brookfield LVT viscometer at 6 rpm; for ease of handling, mixing with other chemicals, or spraying onto crops. Similarly such aqueous emulsions often need to be readily diluted with water of any temperature from 1 β C to 45 β C without coalescence of the dispersed phase. Additionally, the proportion of dispersed internal phase may need to be as low as 1.0% of the total, on the basis of volume, or as great as 45% of the total on the basis of volume. However, the conditions taught by the prior art as necessary in order to achieve one of these pro¬ perties often prevent achievement of another. For example, while it has been known that increased viscosity enhances stability of an emulsion, this also makes the emulsion less readily dilutable. It has also been known that aqueous emulsions composed of greater than 30% internal phase usually have very high viscosity, and that efforts to reduce the viscosity often lead to instability. The preparation of such emulsions often requires undesirably high shear and high energy input, in the case of homogenization, to finely disperse high concentrations of oil. The present invention provides an adjuvant capable of forming aqueous emulsions and dispersions having a wide range of dispersed phase content of at least 1% preferably from 1 to 45% by volume with improved properties of low viscosity (less than 2,000 -4- mPa«s), stability (that is freedom from coalescence) upon storage for at least one month at room tempera¬ ture, as well as after repeated freezing and thawing, ease of dilution with water ranging in temperature from 1"C. to 45 # C. or higher without. coalescence, and ease of preparation without high shear and high energy input as is required in the case of homogenization. These aqueous emulsions and dispersions have proper¬ ties desired for specific fields of utility, such as agricultural chemicals, cosmetics, pharmaceuticals-, dyes, monomers for emulsion polymerization, industrial and other products. The present invention also offers the advantage that it makes it possible to provide an adjuvant containing no calcium ion but instead ammonium, potassium, barium or magnesium ions; this is advan¬ tageous because of the incompatibility of many emulsions with calcium. Moreover, it provides a way safely and economically to pre-emulsify biologically active or hazardous oils at a central location having bulk handling and containment facilities. In this way, simple containers and agitators may be used in the field to dilute the emulsion concentrate to the degree necessary to apply the effective emulsified ingredient at a safe, as well as effective level of addition per unit area. The adjuvant of the present invention consists essentially of an aqueous solution of iota-carrageenan; a water soluble gel-inducing cation selected from the group consisting of ammonium, potassium, calcium, barium, or magnesium or mixtures thereof an amount equivalent to at least 4.8% by weight of the iota- carrageenan; and a water-soluble surface active agent which does not interact with iota-carrageenan in aqueous solution to form a precipitate and which is capable, when shaken together with water and the insoluble material to be emulsified in the absence of carrageenan, of forming a unstable dispersion of discrete particles of the material which, although separating readily from the water, do not coalesce to a substantial extent, which dispersion has a viscosity no greater than 200 mPa*s at 20 β C; the surface active agent is anionic, non-ionic, or amphoteric and amounts to 1.25 to 60 times the weight of the iota-carrageenan. It is one of the features of this invention that an aqueous solution of iota-carrageenan (a sulfated algil polysaccharide) is mixed with a soluble surface active agent or agents as defined above in the presence of the specified soluble gel-inducing cations to produce an aqueous solution which is useful as an.adjuvant for making aqueous emul¬ sions of water-immiscible liquids and dispersions of particulate solids. The term iota-carrageenan as employed herein means polysaccharides (as well as their salts with cations such as ammonium, alkali metals, or alkaline earth metals) composed essentially of glycosidically linked hexose units in the form of D-galactose and 3,6-anhydro-D-galactose residues; these polysaccharides are further distinguished by exhibiting in the infrared spectrum a strong absorption peak at 805-810 reciprocal centimeters, as well as the absorption peak at 845-850 reciprocal centimeters exhibited by common varieties of carrageenan, such as that extracted from Chondrus crispus. Thus, the preferred polysaccharides which exhibit properties suitable for the practice of this invention are polysaccharides wherein the ratio of the absorption peak at 805-810 reciprocal centimeters rela¬ tive to the absorption peak at 845-850 reciprocal centi¬ meters is from 0.50 to 0.90, although the value of this ratio may range from 0.4 to 1.0. The average number of ester sulfate groups in iota-carrageenan as determined by conventional analytical procedures in relation to hexose sugar units is high, namely, about 60% to about 125% of the number of hexose sugar units. The usual sources of the iota-carrageenan that is employed in the practice of this invention are the following seaweeds: Genus and species; Eucheuma spinosum (muricatum) Eucheuma isifor e Eucheuma uncinatum Eucheuma serra Eucheuma gelidium Agardhiella tenera Agardhiella coulterii Gymnogongrus norvegicus Gymnogongrus furcellatus Ahnfeltia durvillaei The foregoing is not an exhaustive list of all seaweeds which yield iota-carrageenan, but only a list of the most readily available types. The hexose composition of iota-carrageenan varies somewhat, depending on the type of seaweed from which the polysaccharide is obtained and on the process¬ ing conditions employed in its recovery from the seaweed. Extraction with alkali generally enhances gelling pro¬ perties and is normally, therefore, preferred. However, alkali extraction is not essential. Thus extraction using plain water is adequate. Generally, the ratio of D-galactose residues to 3,6-anhydro-D-galactose residue as determined by conventional analytical pro¬ cedures is from about 2:1 to about 1:1. The molecular weight of the polysaccharide may vary from about 20,000 to 1,000,000. The soluble gel-inducing cation or cations of the present invention may be provided as a part of any soluble salt such as a chloride, a nitrate, a sulfate (for example calcium sulfate dihydrate), or it may be a part of the iota-carrageenan as in the case of calcium iota-carrageenan, or it may be a part of the surface- active agent, as in the case of potassium oleate or potassium stearate. The amount of cation must be chemically equivalent to at least 4.8% by weight of the iota-carrageenan. There is no upper limit on the amount of cations, although there is nothing to be gained by employing more than an amount fully equivalent to the iota-carrageenan. Although any anionic, nonionic or amphoteric surface active agent meeting the requirements specified above can be used, it should be noted that certain ones, notably those containing carboxyl salt groups such as fatty acid soaps, have a sequestering effect on divalent cations, rendering them insoluble for the purposes of the present invention. Consequently, when a material such as calcium iota-carrageenan is employed in combina¬ tion with a fatty acid soap the calcium is ineffective as a gel-inducing cation and another non-sequestered cation such as ammonium or potassium must be used. These may be added in the form of a soluble salt such as ammonium or potassium chloride, ammonium or potassium sulfate, ammonium or potassium nitrate, or they may be added as a part of the surface active agent, or both. For example, the fatty acid soap used may be a potassium or ammonium soap. The first requirement of the surface active agent, its non-reactive character when mixed with iota- carrageenan can be determined simply by visual observa¬ tion of a solution containing 1% by weight of iota- carrageenan or salt thereof in water when there is mixed with it the selected surface-active agent in an amount equal to ten times the iota-carrageenan by weight. If no precipitate forms, the surface-active agent is satisfactorily non-reactive. The second requirement of the surface-active agent, its dispersing or emulsifying -^3-EXcT O PI / WIPO .v capability, can be readily determined by preparing a water solution containing 10%. by weight of the surface- active agent; into the solution at room temperature there is stirred 1% by volume of the water immiscible liquid of particulate solid which is desired to be emulsified, observing whether or not a dispersion is formed (even though it settles within a few minutes) and measuring the viscosity of the dispersion by means of a Brookfield Syncro-lectric LVT Viscometer at 6 rpm while the. solution is at approximately room temperature (20 * C); if a dispersion is formed and the viscosity is less than 200 mPa»s, the surface-active agent is effec¬ tive. Surface-active agents of two or more different types can be used together; for example, a preferred surface-active agent is a potassium soap of a long chain (12-20 carbon atoms) fatty acid such as potassium oleate or stearate mixed with a long chain (12-20 carbon atoms) fatty alcohol such as oleyl alcohol or hexadecyl alcohol, the amount of alcohol being from 0.1 to 10% by weight of the mixture with the potassium soap. The combination of potassium oleate with oleyl alcohol is particularly desirable because it decreases the energy input required to emulsify a water immiscible liquid in the aqueous adjuvant and producing smaller, more uniform droplets of the dispersed material. Among suitable nonionic surface-active agents are sorbitan monopalmi- tate, polyoxyeth lene sorbitan monopalmitate, polyoxy- ethylene alkyl phenols, for example octylphenoxy- polyethoxy ethanol; useful amphoteric surface-active agents include the sodium salt on N-coco beta-amino propionate; of the anionic surface-active agents, fatty acid soaps are particularly useful, such as the sodium, ammonium, or potassium soaps of fatty acids having from 12 to 20 carbon atoms. r In making the adjuvant of this invention, a dilute solution of iota-carrageenan is first prepared by dispersing a salt of iota-carrageenan into the vortex of rapidly stirring water. While the sodium salt is readily soluble in water at 25 * C, the potassium, ammonium, calcium, barium or magnesium salt require heating to about 70"C to dissolve, after which the solution is cooled. Alternatively, a solution of calcium iota-carrageenan may be prepared by the methods described in U.S. Patent No. 3,562,176, issued February 9, 1971. However, it is a feature of this invention that the calcium salt need not be used, nor does calcium need to be present at any step in the invention, provided another gel-inducing cation is present such as ammonium, potassium, barium, or magnesium. The presence of other non-gel-inducing soluble cations such as sodium is not objectionable.. To the iota-carrageenan solution is added the surface active agent or agents, and soluble salts of gel-inducing cations if an insufficient amount is associated with the carrageenan or surface-active agents, and the solution is stirred until all components have dissolved. The solution so formed may contain all of the water to be present in the final emulsion, or any lesser portion of that water in which case it is a concentrated adjuvant which may be diluted with the remainder of the water at or before the time the water immiscible material is mixed with it to form the desired aqueous emulsion. The aqueous adjuvant concen¬ trate contains the iota-carrageenan, gel-inducing cation, and surface-active agent in relative proportions as defined above but in higher concentrations than the diluted adjuvant or the finished emulsion. The concen¬ tration of the iota-carrageenan in the finished emulsion should be from 0.2-0.8% by weight of the water present, the amount of soluble gel-inducing cation should be at least chemically equivalent to 4.8% of the amount of iota-carrageenan, and the concentration of the surface- active agent should be from 1 to' 20% by weight of the water present. The diluted adjuvant containing the concen- trations of ingredients set forth above has exceptional utility as an aqueous adjuvant into which a water- immiscible liquid or particulate solid may readily be emulsified by simple mechanical stirring. Emulsions prepared from the aqueous adjuvant of this invention may range in proportion of internal phase from 1% of the total on the basis of volume, to 45% of the total on the basis of volume, or higher. Such emulsions are stable for more than one month when stored at room tem¬ perature and are also stable after freezing and thawing; they are dilutable in water at any temperature from 1 β C to 45 * C without coalescence; and they exhibit low viscosity of less than 2,000 mPa » s at 20 β C as measured on a Brookfield LVT viscometer at 6 rpm. The pH of the aqueous adjuvant can vary over a considerable range depending upon the precise surface- active agent employed and the pH of the concentrated aqueous emulsion prepared from the adjuvant can also vary over a considerable range depending upon the precise nature of the water-insoluble material in the dispersed or internal phase of the emulsion as well as upon the nature of the surface-active agent present. For example, when potassium oleate is used as the surface-active agent and potassium is the gel-inducing cation, the pH is approximately 10-11, whereas when octylphenoxy-polyethoxy ethanol (Triton X-100 TM) is used as the surface-active agent, the pH is about 7. This invention is particularly useful in the preparation of emulsions of low melting waxy material, allowing them to be emulsified in the liquid state and remain in a stable wax emulsion (that is, as a dispersion or emulsion of particulate solids) after cooling. Oils Q-v.PI which maintain their liquid state throughout the prac¬ tical temperature range, including non-polar oils such as -light paraffin oil as well as polar oils, are likewise kept in stable emulsions by the adjuvant prepared by this invention. Emulsions prepared in this way often remain stable for periods greater than one year without coalescence. The following specific examples are intended to illustrate more fully the nature of the invention without acting as a limitation upon its scope. Examples There was dissolved by stirring into 99.7 parts by weight of water at room temperature 0.3 part by weight of iota-carrageenan in the form of calcium iota-carrageenan extracted from JΞ. spinosu . With 5 parts by weight of the foregoing solution, there was mixed one part by weight of an aqueous paste containing 42% by weight of potassium oleate to form an aqueous adjuvant containing about 0.3% by weight of calcium iota-carrageenan and about 7% by weight of potassium oleate surface-active agent. The amount of potassium present was equivalent to more than 4.8% of the iota- carrageenan. A concentrated aqueous emulsion was prepared by stirring into 6 parts by weight of the adjuvant, 4.3 parts by weight of a miticidal polar oil, hexadecyl cyclopropane carbox late containing free hexadecanol as an impurity, sold under the trade name Cycloprate TM using a high speed propeller-type stirrer. The result- ing emulsion had a pH of 10.1 and contained approxi¬ mately 45% by volume of dispersed or internal phase polar oil in the form of droplets having an average diameter of 10 micrometers. The concentrated emulsion had a viscosity less than 2,000 mPa-s and measured as described above and was readily diluted with water 1:100 to form a dilute emulsion sprayable in conventional spray eqύipment for use as a miticide. The concentrated emul¬ sion was stable, displaying no coalescence of oil droplets after storage for three months at room temperature. The concentrated emulsion was subjected to three successive freeze-thaw cycles (from -5 # C. to 42"C.) without any change in particle size. Dilution of the concentrated emulsion with 100 times its weight of ice cold water with minimal agitation was accomplished without loss of stability, both before and after subjection of the con- centrated emulsion to the three freeze-thaw cycles described above. Similar results were obtained by substituting for the calcium iota-carrageenan an equal amount of sodium iota-carrageenan, and substituting a non-polar oil, paraffin oil, for the Cycloprate oil. Similar results were also obtained by substi¬ tuting for the potassium oleate an equal amount of octyl- phenoxy-polyethoxy (9-10) ethanol, sold under the trade name Triton X-100. The same surface-active agents were employed in amounts only one-half as large with similar results. The same emulsion bases were also effective for use in forming concentrated emulsions con¬ taining paraffin oil, a non-polar oil, as the dispersed or internal phase. Similar results were also obtained by substi¬ tuting for the potassium oleate 7% by weight of the sodium salt of N-coco beta-amino proprionate sold under the trade name Deriphat 151 TM, an amphoteric surface- active agent, and substituting a non-polar oil, paraffin oil, for the Cycloprate oil. Unstable emulsions, however, were obtained by substituting for the iota-carrageenan an equal amount of gelatin or gum acacia or Irish Moss, and substituting paraffin oil for the Cycloprate oil. These unstable O PI emulsions displayed extreme creaming of the internal phase from the external phase. Unstable emulsions were also obtained when gelatin or gum acacia or Irish Moss were substituted for the iota-carrageenan in an amount sufficient to give the emulsions a viscosity approxi¬ mately equal to the viscosity of the emulsion containing iota-carrageenan.

Claims: Claims : 1. An adjuvant containing by weight 0.2% to 0.8% iota-carrageenan, a gel-inducing cation which is ammon- ium, potassium or calcium in an amount at least 4.8% of the weight of said iota-carrageenan, and 1% to 20% of an anionic, nonionic or amphoteric surface-active agent, the balance being water, which when mixed with water- insoluble liquids or low melting solids forms a concen- trated emulsion containing 1% to 45% or more by volume of dispersed phase and having a viscosity less than 2,000 mPa-s at 70"C, which is stable during storage at room temperature; dilutable with water without loss of stability, and stable to multiple freeze-thaw cycles. 2. A concentrated aqueous emulsion comprising a water-immiscible material, an adjuvant consisting of • iota-carrageenan and a soluble gel-inducing cation selected from ammonium, potassium and calcium in an amount at least equal to 4.8% of the amount of iota- carrageenan, a surface-active agent which is either anionic, nonionic or amphoteric and which is capable of dispersing in water in the absence of iota-carrageenan at least 1% by volume of the water-immiscible material to form an unstable dispersion having a viscosity less than 200 mPa-s at 20 * C, the amount of said surface- active agent being from 1.25 to 60 times the weight of the iota-carrageenan, said emulsion containing in the dispersed phase at least 1% by volume of the water- immiscible material, said emulsion having a viscosity of less than 2,000 mPa«s at 20 β C. and being stable to repeated freeze-thaw cycles, and said emulsion being dilutable with water at 1 * to 45 * C without loss of stability. 3. An adjuvant as claimed in claim 1 characterized in that said ingredients are dissolved in water in the form of a solution containing dissolved therein 0.2 to 0.8% by weight of said iota-carrageenan, said gel- inducing cation, and 1 to 20% by weight of said surface- active agent. 4. An adjuvant as claimed in claim.2 characterized in that the surface-active agent is a mixture of a potassium soap with a long chain fatty- alcohol having from 12 to 20 carbon atoms. 5. An adjuvant as claimed in claim 2 characterized in that the surface-active agent is a mixture of potas¬ sium oleate with oleyl alcohol. 6. The method of making an aqueous adjuvant capable of forming stable emulsions or dispersions of water- immiscible materials, characterized by dissolving in water iota-carrageenan, and dissolving in said solution a soluble gel-inducing cation selected from the group consisting of ammonium, potassium, calcium, barium or magnesium and a surface-active agent selected from the group consisting of anionic, nonionic or amphoteric surface-active agents which is capable of dispersing in water in the absence of iota-carrageenan at least 1% by volume of the desired water-immiscible material to form an unstable emulsion or dispersion having a viscosity less than 200 mPa-s at room temperature, said adjuvant containing dissolved therein 0.2 to 0.8% by weight of said iota-carrageenan based on the weight of the water, said gel-inducing cation in an amount at least equivalent to 4.8% by weight of said iota-carrageenan, and 1 to 20% by weight of said surface-active agent, based on the weight of the water. 7. The method of making an aqueous adjuvant capable of forming stable emulsions or dispersions of water- immiscible material, which method is characterized by dissolving in water iota-carrageenan and a soluble gel- -gtfREAlT OMPI inducing cation selected from the group consisting of ammonium, potassium, calcium, barium or magnesium, and dissolving in said solution a surface-active agent selected from the group consisting of anionic, nonionic - or amphoteric surface-active agents which is capable of dispersing in water in the absence of iota-carrageenan at least 1% by volume of the desired water-immiscible material to form an unstable emulsion or dispersion having a viscosity less than 200 mPa-s at room tempera- ture, said adjuvant containing dissolved therein 0.2 to 0.8% by weight of said iota-carrageenan based on the weight of the water, said gel-inducing cation in an amount at least equivalent to 4.8% by weight of said iota-carrageenan, and 1 to 20% by weight of said surface- active agent, based on the weight of the water. 8. The method as claimed in claim 6 or 7 character¬ ized in that the surface-active agent is a mixture of a potassium soap with a long chain fatty alcohol having from 12 to 20 carbon atoms. 9« Th method as claimed in claim 6 or 7 character¬ ized in that the surface-active agent is a mixture of potassium oleate with oleyl alcohol. 10. A concentrated aqueous emulsion containing in the dispersed phase at least 1% by volume of a water- immiscible material dispersed in the adjuvant as claimed in claim 3, said emulsion having a viscosity less than 2,000 mPa«s at room temperature and being stable to repeated freeze-thaw cycles and dilutable with water at 1° to 45"C without loss of stability.

Inventors: STANCIOFF D, WOMER M
Applicants: FMC CORP
Application year: 1979
Main classification: B01F17
IPC codes: A61K8, A61Q19, B01F17