MXPA00003320A - Production of free-flowing particulate materials using partially neutralised fatty acids - Google Patents

Abstract

Spherical agglomerates of finely divided material such as inorganic oxides are prepared by admixing a slurry of finely divided material with a solution of a partially neutralised carboxylic acid.

Description

"PRODUCTION OF PARTICLE MATERIALS THAT FLOW FREELY USING PARTIALLY NEUTRALIZED FATTY ACIDS" BACKGROUND OF THE INVENTION The present invention relates to the production of free flowing spheres of solid particulate materials using partially neutralized carboxylic acids. In producing and processing the finely divided solid materials in dry form, it is desirable that the particles be of essentially uniform and free flowing shape and size. It is required that the different finely divided materials are dispersed essentially in polymeric or liquid media. In these dispersions, the term "primary particles" refers to the individual crystals and aggregates tightly retained therefrom. "Agglomerates" are larger associations of primary particles. Ideally, a dispersion consists mainly of primary particles and a minimum of loosely retained aggregates, which consist of co-adherent primary articles. In contrast, when finely divided materials are processed in dry solid form, the particles can be ^^ tiiMÍ? ^ im ^ - ^^^^^ m larger, but preferably are of uniform shape and size so that they flow freely. Powders consisting of these finely divided materials generally exhibit poor flow properties and easily generate undesirable levels of fine dust. Powders that are coated with hydrophobic agents that help pigment moistening and dispersion in polymer systems can worsen problems such as dusty state. Poor flow characteristics result in difficulties in achieving accurate regulated flow delivery. Excessive dusty state can cause problems with respect to industrial hygiene. Free-flowing aggregates overcome these problems. A weakness of current methods for producing free-flowing powders of these aggregates is difficult to disaggregate into primary pigment particles, which limits their applications. A further weakness of some methods used to produce free flowing powders is that significant amounts of binders, up to 20 weight percent, are required with respect to the particulate material. Some freely flowing plastic-grade pigments or fillers can be obtained commercially. Due to the role of pigments stsaáEs. IMRIHMiMikllBI ^^^^ j ^ í ^^ tt ^ such as titanium dioxide, opacifying agents, the primary pigment particles must be submicron size. Free flowing plastic grade pigments or fillers or fillers can be obtained such as TR36 from TiOxide or R-FK21 from Bayer; however, both of these classes suffer from a difficulty to disaggregate and disperse, which limits their usefulness. The present invention essentially overcomes this weakness. U.S. Patent No. 4,375,989 discloses titanium dioxide pigments whose dispersibility is improved by coating with an organic coating and also an inorganic coating. The organic substances used for coating include large molecule fatty acids and their salts. Suitable inorganic coatings are oxides and hydroxides of aluminum, zinc, titanium, zirconium and magnesium. U.S. Patent No. 4,186,028 discloses aqueous fluid suspensions of fillers or fillers or pigments containing dispersion aids which may include phosphonocarboxylic acids and / or salts thereof. U.S. Patent No. 4,563,221 discloses pigments comprising titanium dioxide in particles having an organic coating of isostearic acid, dodecylbenzene sulfonic acid and an agent cationic emulsifier of a fatty alkyl amine. The pigment particles are described as free-flowing coatings, and after treatment do not require milling in a fluid energy mill. US Patent Number 1,722,174 proposes the use of alkali metal and ammonium salts of the fatty acids to provide organophilic lithofono (a mixture of zinc sulphide and barium sulfate). U.S. Patent Number 3,042,539 gives a know the use of alkali metal and ammonium salts of the fatty acids to treat the zinc oxide to produce organophilic pigments of very fine particle size. U.S. Patent No. 4,255,375 discloses the treatment of aqueous pigment dispersions organic with at least one organic acid (such as octanoic acid) which is liquid at temperatures below 100 ° C, or a salt thereof, at a pH value which the acid is insoluble in water, maintaining a temperature above of the melting temperature of the acid until the pigment is has transferred to the organic phase and then add the base to increase the pH until the acid becomes soluble in water. The amount of organic acid added to the pigment is greater than 10 percent by weight of the resulting composition, based on the exposure of the acid and salt as "from 0.1 to 4 parts ... by weight per part of the pigment. "The pigment is recovered as spherical granules of 0.1 to 3 millimeters in diameter, US Patent No. 3,506,466 discloses pigments of titanium dioxide, with or without inorganic coatings, which is treated with salts of water soluble alkanolamines and oxycarboxylic acids and then milled in a fluid energy mill, Hungarian Patent Number 148,370 discloses organophilic oxide pigments prepared by adding a solution of aqueous soap of an alkali metal or ammonium salt of a fatty acid (such as sodium stearate). ammonium) or an aqueous slurry of an oxide, such as titanium dioxide, then adding an acid such as HCl to adjust the pH to about 5. U.S. Patent Number 4,224,080 discloses inorganic oxide pigments (such as titanium dioxide) ) coated with alumina and treated with water-soluble reaction products of excess hydroxy organic acids di- or poly-basic with di- or poly-basic alcohols. British Patent Number 909,220 discloses dried titanium dioxide pigments which are treated with water soluble salts of organic acids (e.g., carboxylic acids) with tertiary amines. The pigments *. * A¿a.feM¿i £ L- * - * > "& & & & amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; amp; formed by the reactions of the organic acids with the alkali hydroxides or amines US Patent Number 4,923,518 discloses chemically inert pigmented zinc oxide compositions prepared by the wet treatment of chemically reactive zinc oxide-based pigments including the Application of chemically inert organic or inorganic coatings These coatings may include water insoluble metal soaps of a saturated or unsaturated monocarboxylic acid or various hydrated metal oxides The pigment particles may be spherical or acicular in shape US Patent Number 4,277,288 gives to disclose a process for producing a granular pigment composition that flows freely from an essentially dry powdery state by contacting a fluid bed of pigment and a granulation aid. U.S. Patent No. 5,215,583 discloses the formation of granules of a suspension of one or more pigments, wherein the suspension also contains ^^ gm 0.05 to 5 percent of a soluble salt, which is selected from alkali metal / alkaline earth metal chlorides, sulfates and phosphates. U.S. Patent No. 5,215,584 discloses a method for producing inorganic granules of a suspension of one or more inorganic pigmenting agents and a hydrolyzed or hardly soluble compound of one or more types of ion present per se as an essential constituent in one or more pigments The American Patent Number 5, 108,508 discloses a method for producing free-flowing, non-fine-powdering microgranules, comprising providing an aqueous pigment suspension optionally containing 0.1 percent to 0.9 percent by weight of a binder and optionally containing 0.1 percent to 2.0 percent by weight of silicone oil and spray the suspension in a spraying tower through a hollow cone nozzle. The binder is a sodium or ammonium polyacrylate, and the granules have a toroidal shape. U.S. Patent No. 5,634,970 discloses a granulation process comprising pre-treating the inorganic pigments by adding oils as binders and subjecting the pre-treated pigment to a. stage of consolidation to form scales that later disintegrate by crushing or coarse grinding. Many techniques have been developed to produce and process these finely divided materials, but in most cases they still lack uniformity in size and particularly shape, and therefore do not flow as freely as desired. There is clearly room for improvement in this field. Accordingly, an object of the present invention is to produce finely divided particulate materials such as pigments, wherein the particles are agglomerates of essentially uniform size and shape. Another object of the invention is to produce particles that are essentially spherical in shape. A further object of the invention is to produce free flowing agglomerates that are robust enough to survive manual handling while still being soft enough to easily disintegrate and disperse within the media in which the powder is being incorporated.

COMPENDIUM OF THE INVENTION In accordance with the present invention, it has been found that mixing a solution of a partially neutralized carboxylic acid with a suspension Aqueous thickened from a finely divided solid material such as metal oxides, produces spherical agglomerates of uniform small size. After washing, dehydration and drying, the spheres retain their size and shape and produce a free flowing powder. Micronization (ie, the process in a fluid energy mill), normally required to produce a finely divided, easily dispersible solid such as a pigment, is not required of course. The The invention provides a process for preparing spherical agglomerates of finely divided materials and, as a product, spherical agglomerates of finely divided materials, which preferably comprise a carboxylic acid metal soap. The product is durable during the handling and shipping and is also more dispersible in the media than the products of the prior art. These and other objects, advantages and particularities of the invention will become apparent to those skilled in the art, when studying the following detailed description, including the appended claims and the figure.

BRIEF DESCRIPTION OF THE DRAWING The single figure is a photomicrograph of essentially spherical titanium dioxide agglomerates prepared according to the invention, at a 50-fold amplification.

DETAILED DESCRIPTION OF THE INVENTION According to the invention, finely divided materials of various types incorporating metal oxides can be formed into spherical agglomerates of essentially uniform size by mixing the materials, preferably in the form of an aqueous slurry, with a solution of a partially neutralized carboxylic acid. . It is important that the single acids are partially neutralized to provide a mixture of the carboxylic acid and a salt thereof, since the experiments indicate that, surprisingly, none of the acids alone or completely neutralized acids (ie, the salts alone) provide the desired effects. Aqueous or non-aqueous solutions of acids can be used. Aqueous slurries of finely divided materials mixed with partially neutralized acid solutions can be prepared by any suitable method, including the addition of a base to an acid solution, then mixing with HfnrTT-lililí n iriiMMi ^^^ iJi = jjfci ^^ llilggl "a slurry aqueous suspension, separate additions of the acid and its salt to form a partially neutralized acid in admixture with the aqueous slurry, and form the partially neutralized acid in situ in the aqueous slurry by separate additions of the acid and base The invention has been satisfactorily demonstrated with pigments such as titanium dioxide and is broadly applicable to metal oxides in general, as well as materials that contain or are coated with metal oxides. As mentioned above, the method is particularly applicable to materials containing surface metal hydroxyl groups. Since the agglomerates formed by the invention are to be used without additional grinding steps, which would destroy the agglomerates, the starting material must be free of large aggregates. A suitable starting material may require milling in a device such as a sand mill or a fluid energy mill before treatment. Aggregates larger than normal can also be removed by steps such as hydro-classification or sieving. Although several metal oxides, for example, zinc oxide, titanium or alumina, are readily applicable to the invention, the modification of the surface by means such as coating with a layer of alumina or other ., generally suitable metal oxide will provide many other particulate materials useful for the invention. Among these particulate materials are the various minerals, inorganic pigments and fillers or fillers, clays, ceramics or refractory materials and the like. Suitable metal oxides include those which form insoluble metal soaps with various carboxylate anions, and preferably have isoelectric temperatures greater than about 5. Suitable metal oxides include, but are not limited to, metal oxides, for example, aluminum, beryllium, cadmium, cerium, chromium, copper, lead, manganese, nickel, tin, zirconium, magnesium, iron and zinc. The isoelectric temperatures of the metals are listed in "The Isoelectric Points of Solid Oxides, Solid Hydroxides and Aqueous Hydroxo Complex Systems" by George A. Parks, Chemical Reviews, volume 65 (2), pages 177-198 (1965), which is incorporated herein by reference. The invention is particularly effective with inorganic oxide pigments, such as alumina, zirconia, magnesia and titanium dioxide. The invention can be practiced in materials of less than about one micron in average diameter and is preferably carried out although in pigments and filling materials having particle sizes average from about 0.01 to about 10 microns. The spherical agglomerates preferably produced are at least about 10 microns in diameter, more preferably from about 100 to about 500 microns in diameter. The titanium dioxide particles, particularly useful in the present invention include crystalline forms of anatase and rutile, and can be treated or coated, e.g., with one or more oxides or hydroxides of metals including aluminum, silicon, titanium, zirconium, magnesium, antimony, beryllium, cerium, hafnium, lead, niobium, tantalum, tin, zinc. Titania pigments or other inorganic oxides may contain aluminum, introduced by any suitable method, including the co-oxidation of titanium (or other metal) halides and aluminum as in the "chloride process" or the addition of aluminum compounds prior to calcination in the "sulfate process". Aluminum compounds can also be add by precipitation of the hydrated aluminum oxides to the surface of the base crystal. Other metals whose oxides have isoelectric temperatures, sufficiently high, by which is meant more than about 5, such as zinc, must replaced by aluminum.

'? R =., R? Fato- The partially neutralized solutions of appropriate carboxylic acids can be used to treat finely divided materials according to the invention. Suitable carboxylic acids can have one of three acid groups and from 3 to about 18 carbon atoms. The "fatty acids" are preferred whereby it is intended to include conventional fatty acids (ie, saturated or unsaturated monocarboxylic acids having from 3 to about 18 carbon atoms), resin acids (ie, acids found in resins that occur in the oil-resin of pine trees or a resin oil produced as a by-product in the Kraft paper industry) and naphthenic acids. Carboxylic acids are discussed in Kirk-Oth er's Concise Encyclopedia of Chemical Technology, (John Wiley and Sons, New York, 1985), pages 217-219, the pages of which are incorporated herein by reference. Preferably, the acids are saturated or unsaturated monocarboxylic acids having from 3 to about 18 carbon atoms, more preferably from 4 to about 12 carbon atoms, and especially preferably from about 6 to about 10 carbon atoms. . A highly preferred material that has been used effectively with titanium dioxide is caprylic (octanoic) acid. The carboxylic acids used must have a pKa (the negative logarithm of the acid ionization constant) of less than about 9, preferably from about 3 to about 9, and especially preferably within the range from about 3 to about 7, to provide the solubility characteristics appropriate. Mixtures of different acids can be used. To achieve the desired effect, the partially neutralized acid added to the aqueous slurry must be at least 0.05 weight percent of the dry weight of the finely divided material, preferably from about 0.1 to about 10 weight percent, and especially preferred way from about 0.5 to about 2 weight percent. The amount of the acid residue actually retained in the spherical agglomerated product should be at least about 0.05 weight percent of the dry weight of the finely divided material, preferably from about 0.2 to about 1 weight percent. The acid should be at least about 5 weight percent neutralized, preferably about 15 to about 99 mole percent. The acid must be neutralized to a pH of between 3 and 8, more preferably to a pH of 4 to 7. The acids can be used with any appropriate bridge of hydroxyl groups, Yes ... ... ^^ utu ^ .. .. H ^ .. ^ tt .... ^ .., .. «faith.-..., ... ... - * - - • •: aa • ^^ | 5 sg¡ gí¡te preference for an ammonium or alkali metal hydroxide, such as sodium hydroxide. In addition to the hydroxyl sources, other Lewis bases, such as amines, e.g. alkanolamines, for example, triethanolamine can be used. These amines include the mono-, di- and trialkanolamines such as monoethanolamine, diethanolamine, morpholine and the like. Mixtures of different bases can be used. The process of the invention includes a step of mixing an aqueous slurry of a finely divided material with an amount of the partially neutralized carboxylic acid effective to form spherical agglomerates. The partially neutralized acids can be prepared by any suitable method, such as by mixing the appropriate amount of a base such as sodium hydroxide with an aqueous solution of a carboxylic acid. The aqueous slurry which is the acid solution to be added must be mixed with sufficient vigor to allow intimate mixing of the aqueous slurry and the added acid to overcome the thickening initiation of the aqueous slurry immediately after the addition of the solution acidic. The degree of mixing will depend on the vessel and the design of the agitator and will be readily apparent by experiments for those skilled in the art. The concentration of the aqueous slurry suspension can affect the size of the beads formed, forming larger beads of more concentrated aqueous slurries. The concentration of the maximum aqueous slurry is determined by the viscosity that can be accepted, particularly after the formation of the count, to minimize undesirable shear stresses in the beads once they have formed. A typical concentration scale would be 500 to 700 grams per liter. In the case of pigments such as titanium dioxide, the thick aqueous suspension may contain particles that have not had any surface modification subsequent to the formation of the crystal (oxidation in the process of chloride or calcination in the sulphate process) and they are referred to as raw pigments. Alternatively, the particles may have some surface treatment or modification e.g., precipitating a coating of metal hydroxides, phostates, silicates or the like. These modified particles can be washed, dried and optionally ground in a process such as in a fluid energy mill before the re-formation of the aqueous slurry. The pH of the aqueous slurry before the addition of the partially neutralized carboxylic acid should be within the range of about 4 to ^ sa ^ -A «^. -Jtabet? TsAa: ^^ P about 8. The acids are neutralized to a pH of between about 3 and about 8, preferably between about 4 and about 7. During the addition of the partially neutralized acid to the aqueous slurry and allowing an appropriate time for interaction and formation of beads, the beads are washed and dehydrated optionally and then dried. Dry cake consists of spherical agglomerates whose sizes vary from as low as 10 microns to 1000 microns or larger. Under optimal preparation conditions, the agglomerates are essentially spherical and reasonably uniform in size and exhibit excellent flow properties. A main aspect of this invention is that even when the agglomerates are strong enough for normal material handling operations, they are not soft enough to easily deagglomerate under normal processing conditions, for example in twin screw extrusion apparatus. Although it is not desired to be limited by any theory, the mechanism of the process of the invention related at least to particles comprising inorganic oxide, can be rationalized in the following manner. The reaction between a carboxylic acid and an alkali continues in the following manner (reversible): • 'J?? I * - -' ~ - »-.« - ,, .... ma imm & -L. m - t * .... ^,., .- ¿¿¿¿aefei ,,. (1) R-COOH + OH ^ - * R-COO + H20 (R is any appropriate chemical group) Mixing a solution of the partially neutralized soluble carboxylic acid with a finely divided material, such as a titanium dioxide pigment, allows intimate contact in the water soluble carboxylic acid salt with the surface of the pigment. The salt anion can then react with surface metal hydroxide groups of the pigment to produce a bound metal soap and release a hydroxyl group, as shown in equation (2): (2) M-OH + R -COO ^ R-COO-M + OH "(M = metal) 15 The reaction (2), like the reaction (1), which comprises that it is completely or essentially reversible, the balance being affected by the pH. Generally, the release of hydroxyl groups would lead to an elevation in pH and limit the number of groups of The carboxylic acid can be fixed to the surface of the pigment by the aforesaid reaction (2). However, the presence of a non-neutralized acid acts as a stabilizer, the hydroxyl released from the reaction (2) being consumed by the acid in the reaction (1), producing more salt anions, which will react with free M-OH groups on the surface of the pigment (M-OH). The reaction continues in this sequence until either all the free acid is consumed or no additional M-OH sites are available for reaction. The latter condition can be described as saturation of the M-OH sites (or other active sites) and should be approximated to be achieved to produce the desired hydrophobic surfaces in the particles. When insufficient free acid is available to saturate the surface of the pigment by the formation of R-COO-M bonds as in reaction (2), the formation of the count can still occur by adsorption of the R-COO groups "up to the surface of the pigment and a sufficient quantity of R-COO groups is fixed, either chemically bound as in R-COO-M or adsorbed in the R-COO groups. " During the wash however, only those groups that form the R-COO-M bonds are retained by the aggregates. The carbon analysis of the dehydrated and dried washed samples shows that the carbon content is equivalent to the non-neutralized component of the acid / acid salt mixture. The salt is removed during washing and apparently acts essentially as a catalyst for the reaction (2).

'W lS «aisi? -g¿i» g. - ^ », > _j4aH-S ..

Due to the buffering effect of the acid / acid salt mixture, a significantly higher level of the carboxylic acid groups can be attached to the surface of the pigment, forming a hydrophobic surface. This coverage by the species having low affinity for water causes the pigment particles to agglomerate together to reduce the total surface energy in the system. Minimization of the amount of exposed surface per unit volume leads to a generally spherical shape for agglomeration of the acid groups and associated pigment particles. It seems that essentially all the pigment particles are fixed to the spherical agglomerates, and that during drying, the spheres In general, they retain their forms and produce a freely flowing powder. As illustrated in the figure and described in Example 6, the agglomerates are essentially spherical and reasonably uniform in size. Through the term "Essentially" spherical, it is meant that the agglomerates have a spherical appearance when amplified such as e.g. in the figure. It is therefore believed that when the partially neutralized carboxylic acids are placed in contact with inorganic oxides such as titanium and ^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ alumina that have surface groups of M-OH, metal soaps are formed linked or more soluble. By essentially capturing the active sites in the particles and creating on the same hydrophobic surfaces, this treatment causes the spherical agglomerates to form. The treatment should be carried out in media essentially free of other anions which could preferably form stable compounds on the surfaces of the particles. Example 11, for example, illustrates that the fluoride ion was able to block the octoate anion and prevent the formation of spherical agglomerates. In most cases, the process of the invention is affected by surface loading phenomena, where a positive surface charge on the treated particles attracts the negatively charged acid anions. Each pigment or coating material, e.g. Inorganic oxides, has its own isoelectric temperature (the pH value at which the surface will not have a neutral charge), therefore, the pH for the mixture of solid material and partially neutralized acid must be adjusted to an appropriate level so that nature of the exposed surface produces a positive surface charge. Preferably the pigment or other solid material includes a component and / or a surface coating that it comprises an elemental oxide whose isoelectric temperature is greater than about 5. These materials include the oxides of metals, for example, of aluminum, zinc, zirconium, beryllium, cadmium, cerium, chromium, copper, manganese, nickel, hafnium, lead, niobium, tantalum and tin. Even when the acid anions will bind to positively charged sites such as alumina, they can not bind to negatively charged sites (under the range of pH values used) such as silica or phosphate. A too high level of negatively charged sites will prevent sufficient coverage of the surface by the acid groups to make the surface sufficiently hydrophobic to account. The coverage of these negatively charged sites with species such as aluminum, 15 can cause the surface to be positively charged sufficiently to take the counts during the addition of the acid / acid salt mixture. A treatment level that is too high with, for example, aluminum hydroxides can hamper the formation of beads due to the gelatinous nature of the precipitated hydroxides which can bind the particles so that they can not be easily separated into beads and also due to the larger group of hydroxyl groups that need to be removed to make the surface hydrophobic as in reaction 25 (2). Therefore, the nature of the coating of ^^ j ^ »'¿e *' '- &** **« MIEMIM - ** - ** "* * * - pigment must be carefully considered before adding the partially neutralized acid. partially neutralized carboxylic acids (and mixtures of the aqueous slurry and acid slurry, once combined) must be low enough to achieve a sufficient positive charge on the particles to attract the acid anions, however, high enough to form insoluble metal soaps or other insoluble compounds on the surface of the particle. These pH levels will necessarily differ for the different combinations of particulate and acid materials. In general, the appropriate pH values will be within the range of about 4 to about 8, and those skilled in the art can easily select the actual pH values by experiments or their previous experience. The following examples indicate preferred embodiments of the invention, these embodiments are illustrative only and are not intended and should not be construed as limiting the claimed invention in any way.

EXAMPLES Example 1 A titanium dioxide pigment produced by co-oxidation of the vapor phase of TÍCI4 and AICI3 to produce 1.09 weight percent of AI2O3 with respect to TiO2, was milled in a sand mill to produce an aqueous slurry of dioxide. titanium which is referred to as "fines". The fines were sieved through a 20 micron sieve. 2400 grams of THYO2 fines in a total volume of 8 liters were heated to 85 ° C and a solution of NaOH (200 grams per liter) was added with mixing until a pH of 7.5 was achieved. The neutralized fines were then dehydrated and washed with 3.6 liters of demineralized water by vacuum filtration. This product was then fumigated in a paste in demineralized water to form an aqueous slurry in a concentration of approximately 600 grams per liter. 18 grams of n-octanoic acid (BDH Laboratory Supplies, 99 percent minimum test) were mixed and mixed in 500 milliliters of demineralized water and a solution of ammonium hydroxide (28 percent NH3) added until the pH of the solution was 7.0. This solution was then added to the aqueous slurry of the titanium dioxide pigment which was reformed into ^^^^^^^^^ l ^^^^^^ ßß »g» M «^^^^^^^^^^^« siiafe * ^^^^^? ^^^? ? * ^ tó! »!? ^ at ^ pasta under agitation. The thick aqueous slurry initially thickened then began to thin out as the beads formed. Within two minutes, the titanium dioxide particles had agglomerated into 5 spheres. All the pigment particles were incorporated into the spheres, as demonstrated by the crystalline supernatant liquid when the stirring was stopped. The beads were transferred to a tray and dried at 105 ° C. During drying, the cake was easily crushed to produce free flowing spheres at an average of approximately 200 microns in diameter.

Example 2 Example 1 was repeated with the exception that the pH of the octanoic acid solution was increased to 8 with ammonia instead of 7. During the addition of the ammonium octoate solution to the aqueous slurry of dioxide pigment of titanium that was re-formed into paste, the aqueous solution thickened to a certain degree, but did not form accounts. The evaluation of octanoic acid with sodium hydroxide shows that at a pH of about 7, 90 mole percent of the acid has reacted, while at a pH of 8 the neutralization has essentially been completed. This Thus, the fully neutralized acid is ineffective in forming the spherical agglomerates.

Example 3 1100 grams of titanium dioxide fines, heated, neutralized and washed as in Example 1, were re-formed into paste after being dehydrated in vacuo with 1 liter of demineralized water. 11 grams of the octanoic acid were added to the fines formed again in paste. Some flocs (small masses formed in the fluid through coagulation or agglomeration of the fine suspended particles) were observed to form, but the slurry retained a creamy consistency. The accounts equivalent to those obtained in Example 1 were not formed with the non-neutralized acid.

Example 4 1200 grams of titanium dioxide fines were treated in 4 liters of water at a temperature of 85 ° C with stirring. The sodium aluminate solution equivalent to 0. 2 percent AI2O3 based on the weight of titanium dioxide and added to the fines, followed by a solution s A ^. - iMlffntiiii '. * ¡T *.-..- .... ^^^ of sodium hydroxide to raise the pH up to 7.5. The slurry of pigment coated as alumina was washed on a vacuum filter with 1.8 liters of demineralized water. The washed and dehydrated cake was again pulped with one liter of demineralized water. 12 grams of the octanoic acid in 100 milliliters of demineralized water were mixed with a sufficient sodium hydroxide solution to neutralize 25 mole percent of the octanoic acid. The pH was 5.7. This solution is added to the suspension slurry of washed titanium dioxide, re-formed into paste. The beads formed easily after 1 to 2 minutes of mixing. The beads were dehydrated, washed with 2.4 liters of demineralized water and then dried at 105 ° C. The dry cake was easily crushed to produce free flowing spheres of a titanium dioxide pigment of approximately 100 microns in diameter.

Example 5 1200 grams of titanium dioxide fines were heated in 4 liters of water at a temperature of 85 ° C. The sodium aluminate solution equivalent to 1 percent AI2O3 by weight of TiO2 was added, followed by 200 grams per liter of hydrochloric acid to achieve a pH of 8. The The resulting slurry was graduated with 3 liters of demineralized water. After dehydration, the filter cake was re-formed into a paste with 600 milliliters of demineralized water. Twelve grams of hexanoic acid in 50 milliliters of demineralized water was dosed with enough sodium hydroxide to neutralize 17 mole percent of the acid. The pH was 5.3. The solution was added to the slurry of titanium dioxide re-formed into paste. The resulting mixture thickened considerably, and gradually thinned through about 5 minutes. The accounts were visible after this time. To complete the reaction with the hydroxyl groups of the pigment coating, an additional 6 grams of hexanoic acid with sufficient sodium hydroxide to neutralize 40 mole percent of the acid in 100 milliliters of demineralized water were added to the slurry of titanium dioxide and they were stirred for 30 minutes. The resulting mixture was dehydrated and dried. The dried cake contained large beads of approximately a diameter of 1 millimeter.

Example 6 They were heated to 85 ° C, 1200 grams of fine titanium dioxide in 4 liters of water with added NaOH - £ * &** - * - - -ifflftiflfT lMr • - ^ «^ ¡gyf- ^ -t to raise the pH to 7.5 and the resulting slurry was washed with 1.8 liters of demineralized water. The resulting filter cake was re-formed into a paste with 600 milliliters of demineralized water. To twelve grams of hexanoic acid in 100 milliliters of water were added 3.9 grams of triethanolamine. This solution (pH 5.0) was added to the re-formed titanium dioxide. The slurry was thickened and gradually thinned after about 5 minutes of stirring after which the aqueous slurry was very fluid. Sources of approximately 275 microns were formed. The mixture was dehydrated and then dried. The dried cake was easily crushed to form a free flowing powder. The Figure, a photo-micrograph of the 50-fold amplification material, shows that the agglomerates are spherical and essentially of uniform size.

Example 7 They were neutralized at a pH of 7.5, 1200 grams of titanium dioxide fines in 2 liters of water. To this slurry a solution of 9 grams of octanoic acid in 100 milliliters of demineralized water was added to which a sufficient amount of the sodium hydroxide solution was added to neutralize the 20 molar percent of the acid. The pH was 5.6. The beads formed easily within approximately 1 minute of shaking. The resulting mixture was dehydrated, and then washed with 2.4 liters of demineralized water, dehydrated and dried at 105 ° C. Three equivalent treatments were carried out with the exception that the degree of neutralization was 40 percent to 60 percent and 80 percent, respectively. The dried samples were analyzed to determine the carbon content, which is listed below in Table I.

TABLE I Degree of Neutralization Coal Content Equivalent Weight of Acid 15 (Molar%) (% by weight) Octanoic (% by weight) 20 0.36 0.5 40 0.30 0.45 60 0.20 0.30 80 0 12 0.18 20 It will be seen that there is a good conformity between the amount of the organic material retained by the pigment and the non-neutralized acid content. For example, with 40 percent neutralization, the level of total nonneutralized addition is 60 x 0.75 percent _iM - itfcjí? i- ^^^^^^ ^ m (total acid addition level) = 0.45 percent, exactly the amount of organic acid retained by the pigment. The neutralized acid component is removed by washing. It will also be noted that samples with 20 percent and 40 percent neutralization levels exhibited superior flow properties to samples treated with 60 percent and 80 percent by weight of neutralized acid.

Example 8 They were heated to 85 ° C, 1200 grams of titanium dioxide fines in 4 liters of water, neutralized to a pH of 7.5 with a NaOH solution and washed with 1800 milliliters of hot demineralized water. 16.8 grams of lauric acid in 500 milliliters of demineralized water (Prifrac 2922-1 supplied by Unichema International) which had 25 mole percent neutralized with sodium hydroxide (pH = 6.9) and which was heated to about 70 ° C was added to a 4 liter beaker and the titanium dioxide paste that had been re-formed into paste was added. The slurry was flocculated and formed beads after approximately half or two thirds of the slurry had been added to the beaker. The resulting mixture was dehydrated rapidly. Although ^^^^^^^^^^^^^^^ g ^ ^^^^^^^^^^^^^ jj ^^ | Mjj ^^^^^^ account formation occurred, results were obtained more satisfactory with hexanoic or octanoic acid. The beads were of a diameter of approximately 25 to 75 microns.

Example 9 An aqueous slurry of titanium dioxide fines containing 1275 grams of Ti 2 at a concentration of about 600 grams per liter was raised to a pH of 5.8 with a solution of sodium hydroxide. In the 60 milliliters of demineralized water containing 9.56 grams of octanoic acid under stirring, 4 milliliters of 200 grams per liter of a sodium hydroxide solution was added, yielding a partially neutralized acid solution with a pH of 5.8. The resulting solution was added to the pigment slurry under agitation. The thick suspension thickened immediately and then quickly thinned out as the beads formed. The resulting slurry was dehydrated and washed with 2 liters of demineralized water, dehydrated and dried at 110 ° C. Beads of approximately 300 microns in diameter were formed. Example 10 imSá? i? é ?? An identical treatment to Example 9 was carried out, except that 2-ethylhexanoic acid was used instead of the octanoic acid. In this example, accounts were not formed even after being shaken for 16 hours. Even if you do not want to be bound by any theory, it is believed that the spherical impediment had a part in this case.

Example 11 To 1300 grams of titanium dioxide pigment fines in a slurry of 600 gram concentration per liter was added 5.2 grams of sodium fluoride, resulting in a pH of 7.0. Hydrochloric acid (200 gpl) was added to reduce to a pH of 5.8. A solution containing 9.75 grams of octanoic acid that had been neutralized by 30 percent with sodium hydroxide (pH = 5.8) was then added to the pigment slurry. The beads were not supposedly formed due to the presence of fluoride ions to effectively block the octoate anions from the surface of the pigment.

Example 12 1200 grams of titanium dioxide pigment fines in an aqueous slurry with a total of 2 liters were neutralized to a pH of 5.85 with a sodium hydroxide solution. 80 milliliters of the solution containing nine grams of octanoic acid that had been neutralized up to 30 mole percent with sodium hydroxide (pH = 5.8) were added to the pigment slurry, resulting in the formation of beads within one minute . After being stirred for three minutes, 2.5 milliliters of 200 gpl of the sodium hydroxide solution was then added to dissolve any excess free acid. After being stirred for an additional 20 minutes, the beads were dehydrated, washed with 2.4 liters of demineralized water, dehydrated and dried at 110 ° C. Beads were formed with an average diameter of approximately 225 microns.

Example 13 Twelve grams of beads produced in Example 12 were processed in 300 grams of black PVC to produce a gray mat in a two-roll Farrel mill. The mats were also prepared using TR36 (TiOxide Group) and RFK21 (Bayer), two commercially available titanium pigments with flowing properties ~ - * .- -t - »» ~ -. . ¿¿* - - * - | ir, i MÉSJfifiBiBiV - &- - i Mt-- - A ¿~ - **? freely containing silicones. The mat produced using the prepared product j = g Example 12 was clean, while the mats produced using two commercially obtainable products contained significant numbers of non-dispersed aggregates. A good indication of the degree of pigment dispersion is to measure the brightness (L * value, as defined by Co mission Int. De l'Eclariage 1976 using a Gardner Colorview Spectrophotometer) of the mats. The results are shown below in Table II: TABLE II Pigment L * Example 12 53.8 TR36 44.0 RFK21 49.6 A higher value of L * is indicative of higher dye strength resulting from a more efficient light scattering due to a higher degree of pigment disaggregation and dispersion. The pigment produced in Example 12 is clearly superior for dispersion.

Using the reading of the present application, various constructions and alternative modalities will become apparent to those skilled in the art. These variations should be considered within the scope and spirit of the present invention. The invention should be limited only by the claims set forth below and their equivalents.

Claims (31)

R E I V I N D I C A C I O N S

1. Free flowing spherical agglomerates comprise metal oxide materials 5 finely divided and at least one metal soap of a carboxylic acid.

2. The spherical agglomerates of claim 1, which are prepared by mixing an aqueous slurry of the metal oxide material finely 10 divided with a plurality of partially neutralized carboxylic acid.

3. The spherical agglomerates of claim 2, wherein the carboxylic acid is at least one saturated or unsaturated carboxylic acid that 15 has from 3 to about 18 carbon atoms.

4. The spherical agglomerates of claim 2, wherein the acid has a pKa of from about 3 to about 9. The spherical agglomerates of claim 2, wherein the carboxylic acid is neutralized to a pH value within the scale from about 3 to about 8. The spherical agglomerates of claim 5, wherein the carboxylic acid Less is about 5 molar percent neutralized. "- '** *' '' '- ^^^ - ^ - - - - - ~ *. ¿-tj¡ | IMMVÉli? L íf = íía l' J.? É M- ... * & * »*. && 7. The spherical agglomerates of claim 2, wherein the carboxylic acid is present at least about 0.05 weight percent of the metal oxide material. Any of claims 2 to 7, wherein the neutralizing agent is at least a Lewis base 9. The spherical agglomerates of any of claims 1 to 7, wherein the oxide material 10 metal is a pigment of titanium dioxide. 10. The spherical agglomerates of claim 9, wherein the pigment contains aluminum. 11. The spherical agglomerates of claim 9, wherein the dioxide pigment of The titanium is coated with at least one metal oxide whose isoelectric temperature is greater than about

5. The spherical agglomerates of claim 11, wherein the titanium dioxide pigment is coated with an aluminum oxide or hydroxide. 13. The spherical agglomerates of any of claims 2 to 7, wherein the metal oxide material contains a metal whose oxide has an isoelectric temperature of at least about 5. 14. A process for preparing agglomerates that 25 freely flow spherical materials finely ^^^^^^^^^^^^^^^^^ & ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the steps of: a) mixing an aqueous slurry of a finely divided material containing at least one 5 metal oxide with an effective amount of a partially neutralized carboxylic acid to form the spherical agglomerates, b) optionally washing and / or dehydrating the material, c) drying the material, and d) recovering the spherical agglomerates. The process of claim 14, wherein the finely divided material is coated with at least one metal oxide having an isoelectric temperature of 15 at least about 5. 1

6. The process of claim 14 or 15, wherein the finely divided material is a titanium dioxide pigment. 1

7. The process of claim 16, wherein the titanium dioxide pigment contains aluminum. 1

8. The process of claim 17, wherein the titanium dioxide pigment is coated with an aluminum oxide or hydroxide. 1

9. The process of claim 14 or 15, wherein the slurry of the finely divided material - i -, ... ^ ^ ^ ^^ É * a ~ A + ~ r. r - > * at ^ MAA ^ ^ is mixed with a solution of the partially neutralized carboxylic acid. The process of claim 14 or 15, wherein the partially neutralized carboxylic acid is formed in situ by separate additions of the acid and a neutralizing agent. 21. The process of claim 14 or 15, wherein the partially neutralized carboxylic acid is formed by separate additions of the acid and a salt thereof to the aqueous slurry. 22. The process of claim 14 or 15, wherein the partially neutralized carboxylic acid is at least about 5 molar percent neutralized. The process of claim 22, wherein the carboxylic acid has a pKa within the range of about 3 to about 9. The process of claim 19, wherein the partially neutralized carboxylic acid has a pH value of about 3 to about 8. The process of claim 20, wherein the partially neutralized carboxylic acid has a pH value in the range of about 3 to about 8. The process of claim 21, wherein the partially neutralized carboxylic acid has a -... ^^. The pH value within the range of about 3 to about 8. The process of claim 24, wherein the partially neutralized carboxylic acid is 5 neutralizes with at least one Lewis base. The process of claim 25, wherein the partially neutralized carboxylic acid is present in a mixture of (a) from about 0.05 to about 10 weight percent of the material 10 finely divided. 29. The process of claim 26, wherein the partially neutralized carboxylic acid is at least one saturated or unsaturated carboxylic acid having from about 3 to about 18 carbon atoms. 30. The process of claim 27, wherein the partially neutralized carboxylic acid is present in an amount effective to saturate the surface metal hydroxyl sites present in the finely divided material. 31. The spherical agglomerates of finely divided material prepared by the process of claim 14. ** "" "e * A", ^^ and ^^ ^? t & g ^