OA11556A - Mineral collector compositions of fatty hydroxamicacid in admixture with an oil and process of maki ng same. - Google Patents

Description

011556

MINERAL COLLECTOR COMPOSITIONS OF FATTY HYDROXAMIC ACID IN ADMIXTURE WITH ANOIL AND PROCESS OF MAKING SAME

BACKGROUND OFTHE INVENTION 5 Alkyl or alkaryl hydroxamic acids and their salts are well-known collectors for the froth flotation of oxide minerais. Soviet workers hâve found a variety of applications forsuch alkyl hydroxamic acids, such as those described by Pradip and Fuerstenau, MineraiFlotation with Hydroxamate Collectors, Reaqents in the Minerais Industry, Ed. M.J. Jonesand R. Oblatt, Inst. Min. Met., London, 1984, pp. 161-168, a recent review that 10 summarizes the flotation application of alkyl hydroxamic acids.

Hydroxamic acids hâve been used for the flotation of metals or minerais such as pyrochlore, fluorite, huebnerite, wolframite, cassiterite, muscovite, phosphorite, hématite,pyrolusite, rhodonite, chrysocolla, malachite, barite, calcite, and rare-earths. They aregenerally more powerful and more sélective then conventional fatty acids, fatty amines, 15 petroleum sulfonates and alkyl sulfates. However, the commercially employed methods ofmaking alkyl or alkaryl hydroxamic acid or its salts are tedious and unsafe from the pointof view of industrial production. A procedure for making potassium alkyl hydroxamate is disclosed in OrqanicSvnthesis, Vol. Il, page 67. In the disclosed process, solutions of KOH and NH2OH-HCI in 20 methanol are combined. After the KCI byproduct is filtered off, the filtrate is combined witha liquid mixture of methyl caprylate and methyl caprate, and, after standing for 24 hours,the product crystals are filtered off. Major drawbacks of this method include low yields,the use of a large amount of toxic and flammable methanol, and the use of potassiumhydroxide, which is more expensive than sodium hydroxide. In addition, the industrial 25 scale filtration of a methanolic reaction mixture is clearly undesirable from a safetystandpoint. U.S. Pat. No. 3,922,872 to Hartiage daims an improved method of making fattyhydroxamates. Hydroxylamine sulfate and the methyl ester of a fatty acid are reacted inthe presence of dimethylamine in an anhydrous lower alcohol slurry. The free hydroxamic 30 acids formed are neutralized with dimethylamine or an alkali métal base to yield anammonium or alkali métal sait, which précipitâtes, and is filtered and dried. However, thedisclosed procedure also employs flammable lower alcohols, such as methanol, éthanol orisopropanol, requiring the filtration of the final hydroxamic product, which is hazardous.Moreover, because of the heterogeneous nature of the reaction, the réaction rate is very 011556 slow, e.g., on the order 15 hours in methanol and 5 days in isopropyl alcohol, and the yields are relatively low, i.e., on the order of about 75 percent.

Various Russian workers hâve reported methods for making alkyl hydroxamicacids and their salts in aqueous alkaline media. Gorlovski, et al., Vses. Soveshch. poSintetich. Zhirozamenitelyam, Poverkhnostnoaktivn, Veschestvam i MoyushchimSredstvam, 3rd, Sb., Shebekino, 1965, 297-9 Chem. Abst. 66, 4983h, 1967, report theproduction of sodium alkyl hydroxamates by reacting the methyl ester of a C7i9 carboxylicacid with an aqueous solution of hydroxylamine sulfate and NaOH at a molar ratio of1:1.22:2.2 and a température of 55°C or below.

Shchukina et. al., Khim. Prom., Moscow, 1970, 49(3) 220, report a yield of only 72to 78 percent of the free C7.9 hydroxamic acid by reacting the methyl ester, hydroxylaminesulfate, and sodium hydroxide for two hours at 20°-25°C and one hour at 55°-60°C,followed by acidification to pH 4-5 at températures below 40°C. Shchukina et al., in Sin.Primen. Novykh Proverkh. Veshchestv, 1973, 123-31 reported in C.A. 80, 1974, 95199K,also report a simple lab method for the production of a reagent designated as IM-50 fromC7.9 esters.

Russian workers, in Russian Patent No. 390,074, Chem. Abst. 79, 115162C(1973), and in Zh. Prikl, Khim, (Leningrad) 1972 45(8), 1895-7, Chem. Abstract 78,29193m 1973, report improved yields with the use of 3 to 5 percent of an anionicemulsifier in an alkaline aqueous medium. The use of an anionic surfactant such assodium lauryl sulfate (3-5 percent based on the weight of the methyl ester), reportedlygave an improved yield of 61.2 percent for valerihydroaxmic acid and 89 percent forcaprihydroxamic acid. To obtain the claimed yields, however, a 40 molar percent excessof hydroxylamine hydrochloride or sulfate was required. Moreover, both the sodium saltsand the free hydroxamic acids recovered are solids, which are difficult to handle andprocess.

Russian Patent No. 513,970, May 15, 1976, Chem. Abst. 85, 66277g, 1976,discloses the formation of a solution of mixed free C3 to Cn hydroxamic acids inhydrocarbons for use as a flotation agent. The disclosed hydroxamic acids were formedby treating carboxylate esters with the sulfaterait of hydroxylamine in an alkali medium,and then treating the resulting sodium alkyl hydroxamates with a minerai acid in thepresence of 100-250 weight percent of a hydrocarbon containing less than 20 percentpolar organic components, e.g., higher alcohols or esters. The aqueous layer containingNaCI or Na2SO4 was discarded as effluent. Because of the incomplète reaction of the 011556 starting ester, this process is inefficient, producing a product that contains significantquantities of the unreacted starting ester. U.S. Patent No. 4,629,556 discloses the removal of various colored impurities fromkaolin clays utilizing alkyl, aryl or alkyl aryl hydroxamates as collectors. The disclosedhydroxamates are produced by reacting free hydroxylamine with the methyl ester of anorganic acid having an appropriate length hydrocarbon Chain and configuration in anon-aqueous medium, such as methanol, in a manner similar to the methods discussedabove. U.S. 4,871,466 discloses a method for the production of alkyl or alkaryl hydroxamicacids and/or salts. In the disclosed method, the methyl or ethyl ester of a fatty acid having6 to 22 carbon atoms is reacted with a hydroxylamine sait and an alkali métal hydroxide inthe presence of a mixture of water, a C8 to C22 alcohol, and, preferably, a non-ionic orcationic surfactant. The disclosed reaction results in the formation of a hydroxamatesolution, which can be used without further processing in the froth flotation of non-sulfideminerais, or acidified to form a liquid alcohol solution of the acid before use in the flotationprocess. The disclosed process éliminâtes the need for hazardous and expensive^recovery steps, such as filtration, it is relatively rapid, taking only three to five hours forcompletion, and provides relatively high conversions to hydroxamates. However, the finaléproduct of the disclosed method contains some unreacted starting ester.

Improvements in the industrial production and performance of the alkylhydroxamate collectors are still required. For example, the handling of solid products isdifficult in large scale of production, and increases the complexity and cost ofmanufacturing. Although this problem may be overcome by carrying out the reaction inthe presence of alcohols, as taught in U.S. Patent No. 4,871,466, as discussed above, theuse of Cg to C22 alcohols leads to reduced yields through the competing reaction oftransestérification and hydrolysis of the methyl esters, e.g., carboxylic acids and othercarbonyl components derived from the starting ester. In addition, where hydroxamic acidcollectors are used in the flotation process, the shorter Chain alcohols, e.g., C8, canproduce uncontrollable frothing or produce undesirable froth properties, enhancing therecovery of undesirable minerais, and longër Chain alcohols, i.e., C,o and above, canreduce frothing substantially, which is a serious concern in column flotation where acertain amount of controlled froth phase is necessary. Furthermore, in certainapplications, depending on the value minerai being floated, the higher alcohols can adsorbon the value minerai in a reverse configuration, i.e. they can adsorb with the polar group 011556 exposed to the water phase, thereby reducing hydrophobicity on the value minerai beingimparted by the alkyl hydroxamic acid, resulting in the reduced recovery of the valueminerai. The commercial alcohols, which can be expensive, also hâve a very strong,sometimes offensive odor, which varies with Chain length.

Therefore, there remains a need for alkyl hydroxamic acid collectors and a procéssfor preparing such collectors that overcome the problems discussed above. The présentinvention provides such collectors and a process for preparing them.

SUMMARY OF THE INVENTION

The invention is directed to collector compositions for use in the removal ofimpurities from minerai ores, and to methods for making and using such coilectorcompositions. Typically, a collector composition of the invention comprises a mixture of aC6 to C22 fatty hydroxamic acid and an oil, where the oil is preferably selected from thegroup consisting of hydrocarbon, vegetable, plant, and animal oils, and is most preferablya fatty triglycéride oil. Preferred hydrocarbon oils include, but are not limited to aliphatichydrocarbons, aromatic hydrocarbons, and mixtures thereof, such as benzene, xylene,toluene, minerai oil fractions, kerosene, naphthas, and petroleum fractions.

Preferably, the hydroxamic acid is présent in the compositions of the invention inan amount of from about 5 to about 70 percent by weight, more preferably from about 10to about 50 percent by weight, and the oil is présent in an amount of from about 10 toabout 95 percent by weight, more preferably from about 20 to about 70 percent by weight,based upon the weight of the composition. Optionally, the collector composition furthercomprises up to about 70 percent, preferably, from about 10 to about 50 percent byweight, of a frother.

The collector compositions of the invention may be prepared by reacting an esterof a C6 to C22 fatty acid with a hydroxylamine sait, preferably, a sulfate or hydrochloridesait of hydroxylamine, and a base in the presence of an oil and water to produce an alkylhydroxamate sait. The alkyl hydroxamate sait is then acidified, forming an organic layerand an aqueous layer, where the organic layë'r contains a C6 to C22 fatty hydroxamic acidsubstantially free of hydrolysis and transestérification products of the ester, and theorganic layer is separated from the aqueous layer to provide a minerai collectorcomposition, comprising a mixture of the C6 to C22 fatty hydroxamic acid and the oil. 011556

The benefication performance of the collecter compositions of the invention issignificantly improved when compared to prior art compositions, due to a lack of alcoholand a substantially reduced amount of fatty or starting ester in the collecter compositions.Generally, the collecter compositions of the invention are substantially free of starting 5 ester, such that the amount by weight of C6 to C22 fatty acid ester or starting ester is lessthan the amount by weight of hydroxamic acid. Typically the amount of fatty acid ester orstarting ester présent in the collecter compositions of the invention is 50 percent less thanthe amount of hydroxamic acid, preferably, less than 20 percent, and, most preferably,less than 10 percent of the amount of hydroxamic acid. 10 Esters useful in the process of forming the collecter compositions of the invention include, but are not limited to, methyl and ethyl esters of caproic acids, enanthic acid,caprylic acid, pelargonic acid, caproic acid, undecanoic acid, làuric acid, tridecanoic acid,myristic acid, pentadeconic acid, palmitic acid, margaric acid, stearic acid, oleic acid,benzoic acid, ethyl benzoic acid, salicylic acid, α-naphthoic acid, β-naphthoic acid, 15 cyclohexyl carboxylic acid, and cyclopentyl carboxylic acid.

The collecter compositions of the invention may be used to remove impurities from anon-sulfide minerai ores by forming an aqueous slurry of the minerai ore, conditioningthe minerai ore slurry with the collecter composition of the invention, which is generallyprepared by the method described above, and separating the impurities and the collecter 20 composition from the minerai ore.

DETAILED DESCRIPTION OFTHE INVENTION

The présent invention is directed to useful alkyl hydroxamic acids and the 25 production of such useful alkyl hydroxamic acids by the reaction of the methyl or ethylester of a fatty acid having 6 to 22 carbon atoms with a hydroxylamine sait and an alkalimétal hydroxide in the presence of water, either a hydrocarbon oil or a fatty oil derivedfrom plants, animais or fish, or mixtures thereof, and, preferably, with an optional non-ionicor cationic surfactant. The resulting alkyl hydroxamate sait is subsequently acidified with 30 an acid, and the oil/fat solution of the hydroxamic acid is separated from the aqueousphase, resulting in the formation of a liquid solution or a paste of the hydroxamic acid.The hydroxamic solution or paste can then be used without further modification in the frothflotation of non-sulfide minerais, such as kaolin clays, or can be further diluted with 011556 frothers, such as, e.g., pine oil, aliphatic C5 to C8 alcohols, polyglycols, polyglycol ethers, etc., to provicie a liquid solution useful in a minerai floatation process.

The hydroxamic acid coliector compositions of the invention are produced in high yields, typically greater than 90 percent by weight, and, typically, contain substantially less 5 unconverted starting ester and undesirable side reaction products resulting fromtransestérification and hydrolysis of the starting ester, such as, for example, carboxylicacids and other carbonyl products, than prior art compositions. As a resuit, theperformance of the coliector compositions of the invention is significantly improved whencompared to prior art compositions. 10 The process of the invention for producing alkyl hydroxamic acids éliminâtes the need for hazardous and expensive recovery steps such as filtration, is relatively rapid,being completed in only 3 to 5 hours, and results in extremely high conversions, i.e., onthe order of 90 to 100 percent, due to the élimination of competing transestérificationreactions, and, thus, provides higher yields than prior art processes. When the optional 15 surfactant is used in the process of the invention, the amount of the surfactant required issmaller than that required in prior art processes. In contrast to the prior art referencesdiscussed above, the use of an oil as a carrier from the beginning of the hydroxamic acidpréparation, affords better dispersion of Chemicals, better handling of the reactor in largescale manufacture, more uniform heat distribution, higher yields of hydroxamic acid, and 20 better control of the reactions and acidification.

In addition, when utilized in the froth flotation of non-sulfide minerais, the oil solutions of the hydroxamic acids are significantly more effective than prior artcompositions, producing higher value minerai recovery yields and grades. In general, theoils used tend to be froth neutral, unlike alcohols, having very little effect on froth. The 25 relative froth neutrality of the oil solutions of the hydroxamic acids allows the use ofseparate alcohol frothers to independently control the froth phase properties as desired. .

With the process of the invention, fatty hydroxamic acids are produced by reactinga methyl or ethyl ester of a fatty acid having 6 to 22 carbon atoms, and, preferably, at least8 carbon atoms, with a hydroxylamine sait and an alkali métal hydroxide in the presence 30 of water, and an oil, selected from the group of hydrocarbon oils, fatty oils, or mixturesthereof. The reaction proceeds according to the équations: 011556

Il , η2ο RCOR1 + ΝΗ,ΟΗ ΗΧ + 2ΜΟΗ -=-► Ο Οί| II η2ο RCNHOM + ΗΧ -►

Oil Ο

II RCNHOM + MX + ROH + 2Η2ΟΟ

II

RCNHOH+ MX wherein R is a C6 to C22 alkyl, a C6 to Ci0 aryl, or a C7 to C14 alkaryl group; M is an alkali métal; R1 is methyl or ethyl, and 5 X is a halide, sulfate, bisulfate, phosphate, nitrate or similar anion residue from a mineraiacid.

Useful acid esters include the methyl and ethyl esters of such carboxylic acids ascaproic acids (C6), enanthic acid (C7), caprylic acid (C8), pelargonic acid (C9), caproic acid(Ci0), undecanoic acid (Cn), lauric acid (C12), tridecanoic acid (C12), tridecanoic acid (C13), 10 myristic acid (C14), pentadeconic acid (C15), palmitic acid (C16), margaric acid (C17), stearicacid (C18) and the like, in addition to oleic acid (C18), benzoic acid, ethyl benzoic acid,salicylic acid, a- and β-naphthoic acid, cyclohexyl carboxylic acid, cyclopentyl carboxylic ;r'. acid etc. Ethyl esters of above carboxylic acids may also be used, but require a higherreaction température than the methyl esters. 15 Hydroxylamine salts, such as the sulfate or hydrochloride, can also be used.

Suitable alkali métal hydroxides include sodium hydroxide, NaOH, potassium hydroxide,KOH, and the like. Amines such as ammonia, dimethylamine, etc. can be used in place ofhydroxides. Suitable acids are hydrochloric, hydrobromic, sulfuric, nitric, etc.

As discussed above, the use of a non-ionic or cationic surfactant is preferred. 20 Examples of useful surfactants include non-ionic surfactants, such as alkylpolyethyleneoxy compounds represented by the formula: RO(EO)n-H, 25 where R is C8 to Ci8 alkyl, EO is ethyleneoxy^and n is an integer from 1 to 10, as well asthe reaction products of ethylene oxide and higher alkylene oxides with active hydrogencompounds, such as phénols, alcohols, carboxylic acids and amines, e.g.,alkylphenoxyethyleneoxy ethanols. Suitable cationic surfactants include alkyl ammoniumor quaternary ammonium salts, e.g., tetraalkyl ammonium chloride or bromide, dodecyl 011556 ammonium hydrochloride, dodecyl trimethyl quaternary ammonium chloride and the like,and ethoxylated fatty amines. Other suitable surfactants are described in McCutcheon'sbook of détergents and emulsifiers, the contents of which are incorporated herein byreference. Also included in the aforementioned surfactants are oligomeric and 5 poiymerizable surfactants described at pages 319-322 of Blackley, EmulsionPolymerization Theory and Practice, John Wiley and Sons (1975), the contents of whichare incorporated herein by reference. Examples of such oligomers include ammoniumand alkali métal salts of functionalized oligomers, sold by Uniroyal Chemical under thetrade name "Polywet", and copolymers of acrylonitrile and acrylic acid having molecular 10 weights less than 2,000, which are prepared in the presence of chain terminating agentssuch as n-octyl mercaptan. Examples of poiymerizable surfactants include sodium saltsof 9- and 10-{acrylamido)stearic acid and the like. The effective amounts of the surfactantrange from about 0.5 to 3 percent by weight, of the alkyl ester, preferably about 1 to 2percent by weight, same basis. 15 The reaction température can range from about 15° to 55°C., preferably from about 25°to 35°. The amount of water used should be sufficient to dissolve thehydroxylamine sait, and can vary from about 15-50 percent, generally depending on theconcentration of the hydroxylamine sait solution. The amount of oil used in the reactioncan also vary from about 15 to 50 percent, and is preferably sufficient to keep the reaction 20 mixture liquid throughout the course of the reaction at the selected température.

The oil can be any suitable oil that will provide the resuit of the invention, such as hydrocarbon oils, including, but not limited to, an aliphatic hydrocarbons, aromatichydrocarbons, and mixtures of aliphatic and aromatic hydrocarbons. Preferredhydrocarbon oils include, but are not limited to, benzene, xylene, toluene, minerai oil 25 fractions, kerosene, naphthas, petroleum fractions, and the like. Most preferredhydrocarbon oils are low odor hydrocarbon oils, preferably a paraffin oil, containing lessthan about 1 percent aromatics. The oil can also be a fatty oil, such as a triglycéride oil,which is an ester of glycerol with fatty acids, substantially free of polar components, suchas hydroxyl groups. These triglycéride oils are most often derived from animais, plants or 30 fish by rendering, pressing, or solvent extraction. Fatty oils that can be used include, but are not limited to, soybean oil, corn oil, canola oil, sunflower oil, peanut oil, cod liver oil, shark liver oil, and similar plant, animal and fish oils. The oil used in the présent invention can also be a mixture of a hydrocarbon oil and a fatty oil. 011556

When the reaction between the methyl ester and hydroxylamine is complété, andthe alkyl hydroxamate sait has been formed, the hydroxamate sait is acidified by theaddition of acid, forming two phases, which should be maintained at a températuresufficiently high to avoid the solidification of the organic product phase. The aqueous 5 phase is then removed décantation or by the method disclosed in U.S. Pat No. 3,933,872,incorporated herein by reference. The organic phase contains the alkyl hydroxamic acidcollecter, and is useful as a flotation collecter, either as formed or after addition of a frotherand/or other additives. Useful frothers include pine oil, aliphatic C5 to C8 alcohols,polyglycols, polyglycol ethers, etc. Other types of additives may be also incorporated into 10 the diluent System specifically to improve performance. Examples of useful additivesinclude petroleum sulfonates,· sulfosuccinates, ethoxylated or propoxylated alcoholsurfactants, etc., which boost the performance of alkyl hydroxamic acids.

The présent invention is also directed to the novel compositions produced by theabove-described process. The compositions of the invention comprise a fatty hydroxamic 15 acid, a hydrocarbon oil or fatty oil, and, optionally, a frother or other additive incorporatedinto the diluent System to improve performance. Where a surfactant is used in theproduction of the fatty hydroxamic acids of the invention, residual surfactant may also be . présent in the composition. The alkyl hydroxamic acid content ranges from about 5percent to about 70 percent, preferably from about 10 percent to about 50 percent, and 20 the oil content ranges from about 10 percent to about 95 percent, preferably from about 20percent to about 70 percent. If frothers are added, they may be used in an amount of upto about 70 percent of the total composition, preferably in the range of about 10 to about50 percent. If other additives are incorporated to boost the performance, they may beused in amounts ranging up to about 20 percent of the diluent, preferably about 5 about 25 10 percent.

The above-described compositions are useful in the froth flotation of non-sulfideminerai ores, such as those mentioned above, including copper ores, iron ores, rare andrare earth métal ores, and, more particularly, in the benefication of clays.

Useful flotation methods are well established, and are known to those of ordinary30 skill in the art. The methods generally comprise grinding of ore to liberate minerai valuesand provide ore particles having a size suitable for flotation. The ground ore pulp is pHadjusted, and conditioned with pre-selected and prescribed reagents, such as collectors,frothers, modifier, and dispersants. With some ores, such as glass sands, clays, tailing, 10 011556 etc., the as-mined feed material is already finely divided and, therefore, no additionalgrinding is required.

In the case of the beneficiation of clays, for example, substantially no grinding ofthe as-mined feed is required, because the average particle size is of the order of a few 5 microns. The major impurities in kaolin clays are anatase, TiO2, and complex ironminerais, which impart color to the clay, and decrease its brightness, thus making the clayunsuitable for many of its applications where purity and brightness are absolutelyessential. Conventionally, the removal of such impurities is accomplished by a variety ofmethods, an important one being flotation using tall oil fatty acid. 10 In the froth flotation for beneficating clay, where the clay is slurried in an. aqueous medium, conditioned with an effective amount of a dispersing agent and collector, andfloated, the method of the invention comprises employing as the collector the novelcompositions above, i.e., the hydroxamic acid solution, in quantities ranging from about0.1 to about 18 pounds per ton of ore, preferably 0.5 to 6 pounds per ton. The novel 15 process of the présent invention results in the recovery of clays in high yields, having lowTiO2 content and increased brightness.

As a first step in carrying out such a process, the clay to be purified is blunged inwater, i.e., mixed with water to form a suspension, at an appropriate solids concentration,as described in U.S. Patent No. 4,629,556, the contents of which are incorporated herein 20 by reference. A relatively high pulp density, in the range of about 35 to about 70 percentby weight solids, is preferred since the interparticle scrubbing action in such pulp helpsiiberate colored impurities from the surfaces of the clay particles.

Following conventional practice, a suitable dispersant, such as sodium silicate,polyacrylate, or polyphosphate, is added during blunging in an amount, e.g., about 1 to 25 about 20 Ib. per ton of dry solids, sufficient to produce a weil-dispersed clay slip. An alkali,such as ammonium hydroxide, is also added, as needed, to produce a pH above about 6,and preferably is the range of about 8 to about 10.5. In accordance with the invention, thehydroxamate collector is then added to the dispersed clay under conditions, i.e., properagitation speed, optimum pulp density, and adéquate température, which permit reaction 30 between the collector and the colored impuriïies of the clay in a relatively short time,generally not longer than about 5 to about 15 minutes.

When the clay has been conditioned after the addition of collector, it is transferredto a flotation cell, and typically diluted to a pulp density that is preferably in the range ofabout 15 to about 45 percent by weight solids. The operation of the froth flotation 11 011556 machine is conducted in conventional fashion. After an appropriate period of operation,during which the titaniferous impurities are removed with the foam, the clay suspensionremaining in the flotation cell can be leached for the removal of residual iron oxides,filtered, and dried in any conventional fashion known in the art. 5

EXAMPLES

The following non-limiting examples are merely illustrative of the preferredembodiments of the présent invention, and are not to be construed as limiting the 10 invention, the scope of which is defined by the appended daims. Ail parts andpercentages are by weight unless otherwise specified.

Comparative Example A 15 Following the procedure of Wang, as set forth in U.S. 4,871,466, for comparative purposes, 107 parts of hydroxylamine sulfate were dissolved in 264.4 parts of water in asuitable-three-neck reaction vessel equipped with a condenser, a mechanically-drivenstirrer and a thermometer. After the hydroxylamine sulfate was dissolved, 273.8 parts ofdodecyl -alcohol, 4.8 parts of a 50 percent dioctyl/decyl dimethyl ammonium chloride 20 surfactant, and 200 parts of methyl caprylate/caprate, the starting ester, were introduced.The réaction mixture was cooled to 10-15°C with stirring in an ice/water bath, and 200parts of a 50 percent sodium hydroxide (NaOH) solution was added slowly through anaddition funnel. During the addition of sodium hydroxide, the température was maintainedat 15 to 20°C. After the caustic addition, the température was allowed to rise to 25°C, 25 and the reaction was continued for 4 to 5 hours at 25 to 30°C. At the completion of thereaction, i.e., when the IR spectrum of the reaction mixture showed no trace of the esterband at 1175 cm'1, 225.4 parts of 30 percent sulfuric acid were added to the reactionmixture, and two phases formed and were separated. A titration analysis of the upperorganic layer (513.7 parts),.a solution of the hydroxamic acid in dodecyl alcohol, indicated 30 32 percent hydroxamic acid in contrast to the theoretical yield of 39.2 percent, representing an 81.7% yield based on the amount of starting ester. An NMR analysisindicated the presence of other components in the organic layer, including 7.1 percent byweight of the unreacted methyl caprylate/caprate, 8.6 percent by weight C8 to C10carboxylic acids derived from the starting methyl esters, and 7.1 percent by weight of 12 011556 other carbonyl components derived from the starting ester, where the percentages arebased only on the total weight of hydroxamic acid, unreacted ester, and other reactionProducts in the alcohol solvent. The hydroxamic acid amount was 77.2 percent.

5 Comparative Example B

Following the procedure described in Russian patent 513,970 for comparativepurposes, 992 parts of an aqueous 12 percent solution of hydroxylamine sulfate wereintroduced into a suitable three-neck reaction vessel equipped with a condenser, a 10 mechanically-driven stirrer, and a thermometer. Following the addition of thehydroxylamine sulfate solution, 168.5 parts of methyl caprylate/caprate were added,followed by the slow addition with stirring of 162.4 parts of a 50 percent sodium hydroxidesolution through an addition funnel over a period of 30 minutes. During the addition of thesodium hydroxide, the température was maintained at 26° to 28°C. After the caustic 15 addition, the reaction was continued for 2 hours, while continuing to maintain thetempérature at 26° to 28°C. After the two hour hold period, 79.46 parts of concentratedsulfuric acid (96.4%) were added slowly, and the température was allowed to increase to40°C to keep the resulting hydroxamic acid in liquid form. At this time, 169.5 parts ofkerosene were added, and the acid/kerosene layer was separated from the bottom 20 aqueous layer. The product layer (344.85 parts) was analyzed by titration, and found tocontain 17.4 percent by weight hydroxamate in contrast to the theoretical yield of 50percent by weight, representing a 35% yield of alkyl hydroxamic acid. The percentage ofhydroxamic acid was 35%, of other carbonyl components was 14% and of starting esterwas 51%, as determined by NMR. The weight ratio of starting ester to alkyl hydroxamic 25 acid, as measured using NMR analysis, was 1.46 to 1.

Comparative Example C

The process of Comparative Example B was repeated using 496 parts of a 12 30 percent hydroxylamine sulfate solution, 84.25 parts methyl caprylate/caprate, 81.2 parts of a 50 percent NaOH solution, and 39.73 parts sulfuric acid. Again the température after the addition of sulfuric acid was allowed to rise to 40°C, and 211.9 parts of kerosene were added. The upper organic layer was separated from the aqueous layer and analyzed by titration, indicating a 10.54 percent by weight yield of hydroxamate in contrast to the 13 011556 theoretical yield of 28.57 percent by weight, representing a 37 percent yield. The NMRanalysis showed 37% hydroxamic acid, 13% other carbonyl components and 50% startingester. The weight ratio of starting ester to alkyl hydroxamic acid, as measured using NMRanalysis, was 1.36 to 1. 5 EXAMPLE 1

In a suitable three-neck reaction vessel, equipped with a condenser, amechanically-driven stirrer, and a thermometer, 1627 parts of hydroxylamine sulfate were 10 dissolved in 4066 parts of water, and 4145 parts of soybean oil, 67 parts of a 50 percentdioctyl/decyl dimethyl ammonium chloride surfactant, and 3036 parts of methylcaprylate/caprate were introduced. The réaction mixture was cooled to about 10 to about15°C with stirring in an ice/water bath, and 3028 parts of 50 percent sodium hydroxidewas then added slowly through an additional tunnel maintaining the température at about 15 15 to about 20°C throughout the addition. After the addition of the sodium hydroxide, the température was allowed to rise to 25°C, and the reaction was continued for about 4 to5 hoursfat a température of about 25 to about 30°C. The completion of the reaction wasdetermined from the IR spectrum of the reaction mixture, which showed no trace of theester bànd at 1175 cm'1. Two phases were formed by the addition of 5120 parts of 18.76 20 percent sulfuric acid, and separated, while maintaining the température above thesolidification température of the hydroxamic acid, e.g., about 30° to 40°C. The upperorganic layer, 7719 parts, was found to contain 38.5 percent by weight free hydroxamicacid, corresponding to a 97.5 percent yield, when compared to the theoretical yield of 39.5percent. Only traces of starting methyl ester and acids derived by hydrolysis were 25 présent, as evidenced by the high yield of product. The organic solution, which wasobtained by phase séparation, was compatible with tall oil fatty acids, containedcapryl/capra hydroxamic acid in soybean oil, and was liquid at températures above about30°C, and a paste at lower température. 30 EXAMPLE 2

The procedure described in Example 1 was repeated. However, following theacidification and séparation of the phases, 1281 parts of alcohol frother MIBC were added.The resulting liquid product had a hydroxamic acid of content of 32.7 percent, and 011556 remained liquid at a température of 20°C. The liquid product was again found to be compatible with tall oil fatty acid. 14 EXAMPLE 3

The procedure of Example 1 was repeated, replacing the soybean oil being withhydrocarbon oil, Escaid 110. Following phase séparation, the hydroxamate content of theresulting oil solution was 39 percent, representing a 98.7 percent yield of hydroxamic acid.NMR analysis showed the presence of less than 3 percent starting ester and carboxylicacid. The product was substantially free of starting ester, having a weight ratio ofunconverted starting ester to alkyl hydroxamate of only 0.02 to 1. The solidification pointof the product was 32°C. EXAMPLE 4

The procedure of Example 1 was repeated, replacing the soybean oil with a cornoil. Following phase séparation, the hydroxamate content of the resulting oil solution was 38.9 percent, representing a 98.5 percent yield of hydroxamic acid, and the solidificationpoint was about 30°C. EXAMPLES 5-8

The procedure of Example 1 was again followed, except that the methylcaprylate/caprate was repiaced by an équivalent amount of methyl stéarate, Example 5,ethyi oleate, Example 6, methyl palmitate, Example 7, or methyl napththolate, Example 8.Similar conversions of the methyl esters to hydroxamic acids were achieved, andsolidification point were similar to those obtained in Example 1. EXAMPLES9-15

Four thousand parts of fresh kaolin dry basis were blunged at about 60 percent solids for six minutes in a laboratory Morehouse Cowles Dissolver, Model: W12, with water and 6 parts of sodium silicate. A prescribed amount of collecter, along with 15 011556 AEROFROTH® 70 Frother, was then added to the well dispersed clay slurry, and themixture was conditioned in the same blunger for an additional six minutes.

After conditioning, the entire pulp was diluted with water to 20 percent solids. Asufficient amount of the diluted pulp was taken to provide 2000 parts of fresh kaolin clay in 5 a 4.5 liter laboratory Denver flotation cell. Flotation was carried out at 20 percent solids bycarefully regulating the air flow for up to 15 minutes while agitating at 1200 rpm.

Flotation of this kaolin clay sample, designated Sample A, was significantlyimproved with the novel collectors of the présent invention, Examples 9 to 14, whencompared to the plant standard co-collector System, which ïs a 1/1 combination of tall oil 10 with a collector made in accordance with U.S. Patent No. 4,871,466, a commercial alkylhydroxamate collector product used in Example 15. The results of the comparison areprovided in Table I.

Table I: Results of Denver Flotation Test Work on Kaolin Sample A EXAMPLE COLLECTOR FROTHER YIELD TiO2 No. Type Lbs/T Type Lbs/T % % V. 9 1:1 Ex. 3/Fatty Acid 2 AF-70 0.25 80.1 0.801 10 1:1 Ex. 3/Fatty Acid 4 AF-70 0.25 82.4 0.538 11 Example 3 2 AF-70 0.25 84.7 0.440 12 Example 3 1 AF-70 0.50 95.6 0.548 13 1:1 Ex. 1/Ex. 3 1.5 AF-70 0.50 74.3 0.501 14 Example 1 1.25 AF-70 0.25 87.6 0.346 15 commercial collector 1 Tall Oil 1 83.6 0.800 EXAMPLE 16

The alkyl hydroxamate composition of Example 1 was evaluated at a dosage of 20 1.25 Lbs./T with 0.25 Lbs/T of AF-70 frother using a laboratory column cell incorporating microcell bubble generator System. The clay yield was 97.8 percent and the TiO2 content of the flotation product was 0.421 percent. 16 011556 EXAMPLES 17-29

Flotation tests were carried out on three additional kaolin clay samples designatedhere as clay samples B, C and D. These crude clay samples had characteristics as 5 summarized in Table II below:

Table II: Characteristics of Clay Samples B, C and D

Crude Type Crude ID No. GE Bright TiO2 Fe% % Passing 2.0 nm % Pass 0.2 nm Fine C 82.81 2,446 1.375 87.7 46.4 Coarse B 84.38 1.730 0.357 63.8 15.2 Coarse D 84.74 1.783 0.781 76.5 23.5 10 A Premier Mill Agitator blunger was used to blunge 796 parts of fresh wet kaolinclay, équivalent to about 651 parts dry solids, with water and 1.3 parts of sodium silicate at60 percent solids for 6 minutes. A prescribed amount of collector, either a collector of theprésent invention or a prior art collector for comparison purposes, was then added to the 15 well dispersed clay slurry, and the mixture was conditioned in the blunger for an additional6 minutes. The conditioned pulp was then transferred to a 2.3 liter flotation cell, dilutedwith water to about 25 percent solids, agitated at 1000 rpm, and floated with a carefullyregulated air flow in the range of about 0.1 to 1.5 l/min of air for up to about 30 minutes.

The floated product containing colored impurities, mostly titaniferous minerais and 20 anatase impurities, and the unfloated cell product, containing the clean and bright clayvalues, were filtered, dried, and assayed for TiO2 and Fe2O3. The results are set forth inthe Table III below:

V

III 17

Di 15'-

18 011556

The results for crude clay sample B demonstrate the superiority of the novel collectors of the présent invention over both the standard tall oil fatty acid and the commercial collector • of Example 15. The best performer on this crude, based on both produçt yield and TiO2réduction, was the composition of Example 2, which produced a clay product with a yield of60 percent at a TiO2 grade of 0.39 percent, as well as a higher GE brightness.

With fine crude clay sample C, the collectors of the invention again surpassed theflotation performance of both the standard tall oil fatty acid and AP-6493. The best performerwith this crude was the collector of Example 1, which produced the greatest réduction in TiO2level at a comparable product yield of 61 percent.

Coarse crude clay D responded to the standard tall oil floatation very poorly, givingTiO2 réduction of only 0.8 percent, with a product yield of 60 percent. The newly inventedcollectors, along with the commercial collector, produced much improved flotationperformance as compared to the standard fatty acid tall oilsystem. Both the compositions ofExamples 1 and 3 produced significantly better TiO2 réductions than the commercialcollector, at 0.53 percent and 0.66 percent, but lower product yields of 58 percent and 64percent, respectively, as compared to the commercial collector's 0.81 percent TiO2 and 70percent yield.

While it is apparent that the invention disclosed herein is well calculated to fulfill theobjects stated above, it will be appreciated that numerous modifications and embodimentsmay be devised by those skilled in the art. Therefore, it is intended that the appended daimscover ail such modifications and embodiments that fall within the true spirit and scope of theprésent invention.

Claims (7)

19 THE CLAIMS We claim:

1. A method for preparing a minerai collector composition, the method comprising:reacting an ester of a Ce to C22 fatty acid with a hydroxylamine sait and a base in the presence of an oil and water to produce an alkyl hydroxamate sait; then acidtfying the alkyl hydroxamate sait, forming an organic layer and an aqueous layer; and separating the organic layer from the aqueous layer to provide a minerai collectorcomposition, comprising a mixture of the C6 to C22 fatty hydroxamic acid and the oil.

2. The method of claim 1, wherein the organic layer contains a Ce to C22 fattyhydroxamic acid substantially free of starting esters and hydrolysis and transestérificationProducts of the ester.

3. The process of claim 1, further comprising selecting the oil from the groupconsisting of hydrocarbon, vegetable, plant, and animal oils.

4. The process of claim 3, wherein the oil is a fatty triglycéride oil.

5. The process of claim 4, further comprising selecting the ester from the groupconsisting of methyl and ethyl esters of caproic acids, enanthic acid, caprylic acid,pelargonic acid, caproic acid, undecanoic acid, lauric acid, .tridecanoic acid, tridecanoicacid, myristic acid, pentadeconic acid, palmitic acid, margaric acid, stearic acid, oleic acid,benzoic acid, ethyl benzoic acid, salicylic acid, α-naphthoic acid, β-naphthoic acid,cyclohexyl carboxylic acid, and cyclopentyl carboxylic acid.

6. The process according to claim 1, wherein the hydroxylamine sait is a sulfate orhydrochloride sait.

7. The process according to claim 1, further comprising maintaining the organic layerat a température above that at which the hydroxamic acid solidifies.