June 26, 1945. A. T. McCORD ET AL 2,379,019 PREPARATION OF PIGMENTARY MATERIALS Filed May 29, 1942 2 Sheets-Sheet 1

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ANATASE

Y-TANCACD

SPINEL, MgA,0,

ZNC TTANATE

ZnTO,

LMENITE, FeTiO,

MAGNESUM TTANATE MgTiO, 9

ZING TANATE

NVENTORS Azar (a 2/7 (or a All B24.1.1 (7//ova A'.5ozzzzi Alt1-61 (62/5 ATTORNEYS June 26, 1945. A. T. McCORD ETAL 2,379,019 PREPARATION OF PIGMENTARY MATERIALs Filed May 29, 1942 2 Sheets-Sheet 2

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TEORECA RUTLEliot Xzr Toyto, ----- experimeNA

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ANATASE. Torzno 6 to ido 90 % Znd MoisésMoso Ana,yev ZaacSara COy faroda ASzezzaars

274MeaAt TORNEYS Patented June 26, 1945 2,379,019

UNITED STATES PATENT of FICE 2,379,019 PREPARATION OF PIGMENTARY - MATERIALs Andrew T. McCord and Barold F. Saunders, Ead donfield, N. J., assignors to The Sherwiri-Wi Ohioams Company, Cleveland, Ohio, a company of Application May 29, 1942, serial No. 445,022 23 Claims. (C. 106-300) An object of this invention is to prepare pig found that when a relatively small amount of a Enents of high durability characteristics and ex titanate, especially one of the metatitanate type, cellent pigmentary properties, comprising ti is introduced into the dioxide itself, in tanium dioxide detectable by X-ray analysis as the manner hereinafter described, a consider anatase or rutile, and/or compounds having the 5 able improvement in chalk resistance is obtained general formula acRTiOasyFiOa, where R is a bi at the expense of only a minor reduction in the Valent metal, where gy may be zero or a quantity, hiding power of paints made from this pigment. and where TiO2 is titanium dioxide present in When the quantity of titanate so introduced is solid Solution in the RTiO3, and determinable by very small, there may be an actual improvement chemical analysis as an excess over the theo in the color and brightness. retical proportion for RTiO3. More particularly, Several processes have been devised for the the present invention is concerned with pigments conversion of anatase into rutile, mixtures of in which the R of RTO is zinc, and in the fol rutile and zinc orthotitanate (ZnTiO4) and/or lowing specification we will describe in detail Solid solutions of titanium oxide in zinc ortho Only that embodiment of the broader invention. titanate. The high hiding power or obliterating power of Thus, for example, Goldschmidt U. S. Patent titanium dioxide, particularly when in the pig No. 1348,129 converts precipitated titanium di mentary rutile modification is well known, and oxide to the rutile modification by heating at 900 titanium dioxide is, therefore, a preferred pig C. to 1000 C. in the presence of a volatile halo ment for white paints of all types, where the 20. gen compound, as Zinc chloride. Goldschmidt maximum obliteration of the surface to be paint in U. S. Patent 1,436,164 converts the anatase led is desired. One of the objections to titanium form of titanium dioxide, as precipitated by ther pigments for paint-and other usage is the tend mal hydrolysis of an solution, to a ti ency for these pigments to chalk out of the paint tanate by heating it, together with a compound film when exposed to weather. In tinted paints of a bivalent metal compound such as a com using titanium dioxide in combination with a pound of calcium, strontium, barium, magnesium, coloring pigment, the chalking of the titanium , zinc, or manganese. Cole in U. S. Patent induces a white, dusty surface on the paint film 2,184,938 obtains mixtures of titanium dioxide which lightens the apparent tint or color of the and solid solutions of titanium dioxide in zinc paint, and the effect is known as “fading." The 30 Orthotitanate by heating titanium dioxide with titanates, such as zinc titanate or lead titanate, varying proportions of a zinc compound in the are far superior to titanium dioxide as respects presence of a phosphate compound. Booge, in chalk resistance and fading resistance when used U. S. Patent 2,253,551 produces titanium oxide with coloring pigments, but lack the superior in the rutile form intimately combined and asso hiding power of the titanium dioxide ciated with minor amounts of zinc orthotitanate The addition of a titanate, such as zinc titanate by heating a mixture of titanium oxide of the or lead titanate, to paints formulated primarily anatase modification and a minor proportion of with titanium dioxide as the principal pigment a zinc compound. . has been recommended for the purpose of in In all of these processes the titanium oxide proving resistance to chalking. In general, it has 40 used in the starting mixture has been the anatase been found, however, that the proportion of ti modification either as precipitated by thermal tanate required to effect a satisfactory improve hydrolysis from ilmenite solutions or titanium . ment in the resistance to chalking has been so Sulphate solutions, or from the calcination of great that the consequent drop in hiding power these precipitates. The titanate obtained has and color of the paint is excessive. We have 45 been the 2inc orthotitanate of cubic symmetry, 2 2,379,019 formula aczngTiO4.gTiO2, in which ac and 2) are and of the spinel structural type. (Cole and Nel whole numbers and ac is greater than 2), and we son, J. Phys. Chem. vol. 42, Feb. 1938, pp. define the term "zinc-titanium- Con 245-251.) pound of the ilmenite structure type' as mean We have found that when mixtures in varying ing either the pure zinc metatitanate of hexag proportions of ?y- and a metal oxide, onal symmetry and the ilmenite structure type, such as zinc oxide, are heated, entirely differ or a solid solution of titanium dioxide therein, ent results are obtained as compared to similar and of the general formula, acznTiO3.gTiO2. treatment of similar mixtures but in which the We are aware that Lederle in U. S. Patent titanium is supplied as anatase. As will be later 0 2,140,235 states that zinc titanate pigments are pointed out, titanium dioxide in the y-titanic obtained by heating zinc oxide with titanium acid modification does not conform to the teach dioxide in the proportion of at least 0.9 moi of ings of prior art dealing with reaction between zinc oxide to 1 mol of titanium dioxide at tem a titanium compound and a metal compound to peratures between 500° C. and 1100° C. He also form titanates. The tendency for combination of the y-titanic states that between the limits of 1 to 1.5 mois of acid and an oxide, as zinc oxide, for example, is zinc oxide to 1 mol of titanium dioxide, with tem so noticeable even at 100 that, although the X peratures of 900 to 1100° C., mixtures of zinc ray does not reveal conversion to titanate, the titanate crystals of the spinel crystalline form metal oxide is so tightly bound to the titanium with those of the corundum crystalline form are oy adsorption or otherwise that it cannot be ex obtained, while at lower temperatures, for in tracted therefrom by leaching with the usual sol stance 500 to 900° C., mixed crystals of spinel vents for zinc oxide, such as ammoniacal am-- form only are produced; that with proportions of monium chloride. (See Table I.) The titan more than 1.5 mols of zinc oxide to 1 mol of ates prepared from y-titanic acid and a metal titanium dioxide, exclusively mixed crystals of oxide in the manner described herein are highly 25 zinc titanate having the structure of Spinel are suitable for use as pigments, possessing excellent obtained. Lederle in U. S. Patent 2,140,236 states texture, whiteness, brightness, hiding power, and that the undesirable texture characteristics resistance to Weathering. usually found in titanates obtained by heating to It is well known that the compound ZingTiO4, gether titanium dioxide and a metal oxide may zinc orthotitanate, Crystallizes in the cubic sys 30 be avoided by a combination of steps comprising tem and possesses crystalline structure of. the mutual precipitation of the compounds, a two spinel type (Wyckoff's MgAl2O4(k). (Wyckoff, The stage calcination, and pressure treatment of the structure of crystals, 2nd edition (1931), p. 292.) in-process materials. (It will be understood that The terms "symmetry" and 'structure types' are the corundum crystalline form as referred to by used in this specification and the claims attached 5 Lederle is the same as the ilmenite structural thereto in the same sense that they are employed type, the latter being the more recent nomen in Wyckoff. On p. 287 of the reference, Wyckoff clature as employed by Wyckoff and Hanawalt describes compounds, R2MXA, type (k) with the for compounds of this type.) space group Oh. The pattern of ZnTiO3 has not The probable phase diagram covering the sys hitherto been published, and this compound has 40 tem. TiO2/ZnO obtained by heating proportions been found by us to be of hexagonal symmetry of titanium dioxide in the form of anatase, such and of the FeTiO3 or ilmenite structure type. for instance as is derived from thermal hydroly Wyckoff's ilmenite, FeTiO3 (aac). (Wyckoff, The sis of sulphate solutions of titanium in the usual structure of crystals, Supplement, 2nd ed. (1935) commercial procedure With zinc oxide, is shown page 54.) in solid lines in Fig. 2. The dotted lines are in The two titanates, Zinc Orthotitanate, Serted to set forth experimental data, on a lim Zn2TiO4, and 2inc metatitanate, ZnTiO3, possess ited time of heating of 12 hours. specific and different lattice structures in which The samples were prepared for X-ray ex the elements are so arranged as to exhibit char amination by molding a mixture of the Sample 50 with a minor amount of glyceryl phthalate solu acteristic diffraction patterns comprising lines tion in mineral spirits as a binder into a solid spaced substantially as shown in Fig. 1 of the rod 3mm. dia. x 15 mm, long. The rod was baked accompanying drawings, when measured on a and then placed in the camera in such a manner scale calibrated in Angstrom units (A). that the rod forms one side of the defining slit, Zinc orthotitanate, ZnTiO4, cubic. ao=846A. 5 5 the other side being a block of brass. The X-ray Zinc metatitanate, ZnTiO3, hexagonal. beam was impinged upon the rod in the usual atos-3.56Aag=58° 38'. manner. The power was supplied by a General Fig. 1 also shows the lines of the pattern of the Electric XRD Unit consisting essentially of a 50 FeTiO3 structure type. The presence of TiO in kv. transformer, a Kenotron rectifier and a G. E. solid solution in either of these titanates produces 60 CA-2 -cooled X-ray tube with molybdenum changes of minute order in line position and/or target. The current employed for Operation was intensities in the powder diffraction patterns of 30 kV.P. with 20 ma. the pure titanate, and solid solutions effects are It will be seen from the diagram Fig. 2 that easily demonstrable in a back-reflection camera by heating mixtures of zinc oxide with the anatase or in a Laue pattern because of small changes in 65 forms of titanium dioxide, for instance as from the length of the unit cell. As the quantity of hydrolysis of ilmenite sulphate solution, the re titanium dioxide in solid solution in the titanate Sulting titanates are primarily the zinc ortho increases there is a slight change in the value titanate, ZnTiO4, Solid solutions of variable com of do. . position ac2nTiO4.2fTiO2, and mixtures of these In this specification and the claims appended 70 with TiO2 in either anatase or rutile forms, in thereto we use the term "zinc-titanium-oxygen agreement with Cole, as described in U. S. Pat compound of the spinel structure type' as mean ing either the pure zinc orthotitanate of cubic ent 2,184,938, and Cole and Nelson J. Phys. Chem. symmetry and the spinel structural type, or a vol. 42, Feb. 1938, pp. 245-251. The areas of the Solid Solution of titanium dioxide therein, of the 75 diagram agree reasonably well with those of Cole, 2,879,019 3 Table Equivalent Ratio2no/TiO ratio Temp.O. U. S. 2,140,235 Fouad . . .. TiOzno 1-i.5 -0.66 900-1, 100 Mture offine titanate rystals.gif Mituresgrute and solid solution of variable component l the spinel crystalline form with a2ntiQ4. TiO of spinel crystalline form only. No ill of the corundum crystalline menite type crystals found. Or. l-1.5 -0.66 500-900 Mixed crystals of the spinel crystal- Same as above at above 800DC. Solid solution of variable line form. - composition a2nTiOyiOs of spine structural typo only, at between C. - . Excess of 1.5 Below.66. Mixed crystals of zinctitanates have Rutle and/or solid solution of yariable components 1. i.e crystalliné structure of a2ai04. TiO of spinel crystalline form. spinel. s Exces of2 , Bely .5 Excess Zno is not bound...... - ZnTiO, with unbound Zno. lesianLess than 1 labelAbove 900-100 ------RuteTiOyTiO and a solid(spinel solution crystal of type). variable proportions 2ns less an As 800-900 ...... Sane as for 900-1000. --Less than 1. Above1. 1 60-800 ------AnataseyTiO, and(spine a solid crystal solution type). of variable crystals z2ng iO. By the term "y-titanic acid” as used both in approximately 70° C. A similar mixture of hy this specification and the claims attached there drous oxide of the anatase form obtained by ther to, we mean that form of hydrous titanium oxide mal hydrolysis of ilmenite sulphate solution was which may be obtained from a variety of pro prepared in the same manner with zinc oxide. cedures, such for instance, as that disclosed in ap Portions of each mixture before and after cal plication Serial No. 349,345, filed. August 1, 1940 25 cination at a range of temperatures were ex (Patent No. 2,326,156), and which is character tracted by extraction procedure #1, below. A ized by properties of high degree of in second portion of each sample was extracted by inineral acids, and of being directly convertible to extraction procedure i2 below. rutile without the use of sintering agents or ac In Table III, following, col. 3 shows the per celerating agents when calcined at temperatures 3) centage of the total ZnO present, which remained of as low as 800 to 900 C., and particularly by with the extracted residue as fixed, or in some possessing a characteristic crystalline structure manner closely adherent to TiO2, and col. 4 shows in which the chemical Constituents are so ar as a percentage of the total sample taken, the granged in the lattice as to produce upon X-ray 35 ZnO which was extracted in the procedure. The analysis a characteristic band pattern, the bands high retention of the ZnO by y-titanic acid as of which are spaced on a scale measured in ang compared to anatase at low temperature, is not stron units to correspond to the positions indi only indicative of a high reactive or absorption cated in Fig. 1, and to those set forth in the table value, but is a distinguishing feature between the given in Patents Nos. 2,326,156 and 2,326,157, is 8) two titanium compounds. This table also indi sued August 10, 1943. cates that after heating at temperatures above The corresponding characteristic lines of the that at which rutile is formed, more free or un two pure 2inc titanates upon the same scale in bound TiO2 is released as rutile from the mixture angstrom units, are shown in Table II. with Y-titanic acid than from that with anatase. Table II 45 Eactraction procedure #1-A sample of suff

cient quantity to be equivalent to 0.5 gran of ZnO is heated to 60° C. With 100 cc. of a mixture Hexagonal ilmenite type ZnTiO ZnTiO cubic spinel of 200 g. NH4C1, 450 g. 30% NHaOH and 750 g. Á Intensity hkl water, for 30 minutes. Dilute to 250 cc. and fl 50 ter. An aliquot portion of the filtrate is neu 4. tralized with HCl, and add 10 cc. excess HC. 3. Make up to 200 cc. and titrate with Kae(CN)6 . 2. 2. using uranium nitrate outside indicator to de 2. termine ZnO. 2. Eactraction procedure #2.-Same as #1, ex 1. 55 1. : cept that the extraction mixture consists of an 1. i. ammoniacal ammonia carbonate solution con l. taining 120 g. NH3 and 110 gm. CO2 per liter. . l. 1. Table III l. 1. l. O Col. 4. i. Coi, Col. 3 Percent i. Mixture Percent fixed ZO Tenp.,Col. 2 ZnO procedure procedureeased Tödcols. i c oC. -- in litre 05 Per. Per hal-Miller indices. cent cent 2 1. 2 That y-titanic acid possesses other properties. TiO2nO distinguishing it among reactive titanium diox ides from that of the anatase form produced, as 85 15 80 27.4 30 10.9 10.4 risie for instance by thermal hydrolysis of ilmenite 70 85 .1515 875750 60.166.6 s 66.063.0 5.95.0. 5.65.1 io.Do. sulphate solutions, is further evidenced by its re 85 15 975 73.3 79.3 4.0 3. Do. activity toward zinc oxide. A mechanical mix 85 15 80 None None 15. 14.9 Aaatase. 85 - 15 750 . . 4.3 44.6. 8.8 8,3 D0. ture of 85% y-titanic acid and 15% zinc oxide 85 5 87s 73 . . .3 4,3 4.3 Do. was wetted out with a small quantity of water 85. 5 97S 8.3 82.0 28, 27 do. for good mixing and dried at low temperature, 4. 2,379,019 the time of heating has been too short for com Fig. 3 On the accompanying drawings shows plete conversion. Above about 900° C. the pat the phase diagram for the system titanium ox terns show Only the presence of spinel type Crys ide-zinc oxide when the titanium component of tals. the starting mixture is the hydrous titanium ox In reading the diagram, Fig. 3, it will be un ide defined herein as 'y-titanic acid.' The zinc derstood that within a zone, as the proportions oxide may be supplied as the oxide or as any com of TiO2 over ZnO decrease, the gy factor of the pound of Zinc, such for example as zinc Sulphate TiO2 component also decreases, since the excess or zinc chloride, or even as finely powdered Zinc of TiO2 over ZnO decreases as compared to the metal, which will be converted to the oxide under theoretical, and as a greater percentage of the the conditions of heating employed, and if, in total TiO2 above the theoretical is present in the case of the use of zinc metal, Sufficient oxy Solid Solution. gen is present to supply the required amount for When interpreting the temperatures of heat conversion to oxide. The y-titanic acid and the ing herein employed, it is to be understood that zinc compound may be brought together in any an accompanying time factor sufficient to permit desired manner. We prefer to employ the wet 5 stabilization of the phase at that temperature is cake carrying 10 to 80% moisture as obtained to be taken. We have found that for the rage by washing and filtering the precipitate obtained covered, a period of time up to one hour may still by contacting an aqueous solution of ammonium show traces of compounds belonging normally fluotitanate with aqua ammonia in the manner Within the Zone for a lower temperature, espe described in Patent No. 2,326,156, and incorpo 20 cially in the region of transition where two zones, rating dry zinc oxide into this wet cake by thor as shown in Fig. 3, meet. Above 1 hour the ough and complete mixing, and then feeding the products are reasonably well stabilized, and at mixture into a rotary calciner maintained at 4 hours usually completely so, and further ex such speed of rotation that the material will be tension of time effects no further changes. in the effective calcination zone for a period of 2 5 As shown by the diagrams in Fig. 2 and Fig. 3, from two to four hours. In determining the ex below 600° C. titanate formation has not occurred act conditions of palcination our usual proce to any appreciable extent. However, by great dure is, having predetermined the ratio of y-ti prolongation of time, some degree of titanate tanic acid to zinc oxide desired, and mixed the formation may be effected, and we have found tWO, the temperature of the heating apparatus 30 that at 450 for 100 hours some titanate had is set according to the product desired, as deter formed, while with 150 hours at 430°, which was mined from Fig. 3. The speed of rotation when the lowest temperature at which any pattern of a rotary calciner is used for the heating, or the a titanate was observed, a very faint indication time between charging and discharging of a 35 of titanate could be detached in the X-ray pat muffle or other type of furnace is employed, is tern. Such prolongation of time is, of course, determined by operation. Samples of the dis impractical from any industrial standpoint. charge upon examination by X-ray disclose by At proportions of 1.5 to about 4 mols of TiO2 their pattern whether or not the time of heat as y-titanic acid (Fig. 3) with 1 mol of ZnO, ing is sufficient, and the operation period is ad 40 and temperatures between 600 and 775° C., the justed accordingly. . products show X-ray patterns of crystals of the If desired, however, the bringing together of Spinel type and anatase, while at the same temper the starting components may be effected in a ature range for proportions of greater than about 'number of other ways, such as adding the zinc 4 mols of TiO2 to 1 mol of ZnO, the X-ray pat compound to One of the liquors used for pre s tern shows only crystals of the ilmenite struc cipitating the y-titanic acid, by adding a soluble tural type and anatase. Within the range of be Zinc compound to the slurry of y-titanic acid tween 1 and about 1.5 mols of TiO2 to mol of and then precipitating the zinc by addition of a ZnO, and within the temperature range of about suitable reagent, or by dry mixing of dry y-ti 825' to 900 C., X-ray examination of the prod tanic acid with the dry zinc compound. The ucts shows patterns of both the spinel and the mixture may be dried previous to calcination, ilmenite type of crystals. Within this mol range, rather than fed wet, or the calcination may be as the temperature approaches 800° C., the spinel accomplished in other types of furnaces such as pattern is entirely absent, or at most only ex a muffle furnace. s tremely faint, and within a restricted zone of In order to accomplish the desired end, i. e., a 775 to 825 C., only the patterns of the ilmenite product of the composition ac2nTiO3.yTiO2 asso structure type are found, any excess TiO2 present ciated with either anatase or rutile, the propor above the theoretical for the metatitanate, tion of the starting materials must be such as to ZnTiO3, being present in solid solution in the provide an excess of one mol weight of TiO2 for 80 each mol of ZnO. With proportions between 1 ZnTiO3.With proportions of greater than aboutw 2 mols and 1.5 mol. weight of TiO2 to 1 mol weight of of TiO2 to l mol of ZnO, at between about 775 2ao at temperatures between about 600°.C. and and 975 C., the products upon X-ray examina 75' C., the products will show upon X-ray ex tion show exclusively the patterns due to zinc amination, either the characteristic superimposed 65 patterns of anatase titanium dioxide and a zinc titanium-oxygen compounds of the ilmenite type, titanium compound of the spinel structure type, i. e., acznTiO3.yTiO2, and rutile, while above this ac2nTiO4/TiO2 or of Zn2TiO4 plus unbound ZnO. temperature the patterns are those of the spinel A portion of the TiO2 is in Solid solution in the structure type, and rutile. Orthotitanate. At between about 775 C. and 900° It will thus be evident from Fig. 2 that for all C., the products upon X-ray examination show 70 proportions of a mixture of titanium dioxide and the patterns of both a zinc-titanium compound zinc oxide, when the TiO2 is supplied in the (cubic zinc orthotitanate) of spinel type and anatase modification, as for example, the precipi one (hexagonal zinc metatitanate) of the ilme tated hydrous oxide obtained from hydrolysis of nite type, with no titanium oxide pattern unless 5 titanium sulphate solution, heating induces pri 2,379,019 5 marily the formation of the cubic zinc ortho have been set forth in the preceding discussion titanate which upon X-ray examination produces and in Fig. 3. The use of specific examples would patterns of the spine structure type. Below seen unnecessary, and since the range of pro about 800° C., TiO2 in excess of that required portion and temperature is great, it is imprac to produce Zn2O4 is in solid solution, tical to cover the entire field by such specific ex amples. The following will illustrate the process czna Toglio, rather than cover it. Eacamaple 1.-Illustrating method of prepara and when the temperature is raised above 800 tion of a pigmentary zinc titanate of the type C., a part or all of this excess TiO2 is set free O ac2nTiO3.gTiO2 wherein the TiO2 is in excess of in the form of rutile. that required by the zinc present to form ZnTiO3, When, however, the titanium oxide in the mix but which upon X-ray analysis shows only the ture is supplied as y-titanic acid, and TiO2 is in patterns of the ilmenite structure type. molecular excess over the ZnO present, the ma To 200 lbs. of an aqueous slurry of y-titanic jor reaction is toward the formation of the hexag 5 onal zinc metatitanate, and X-ray examina acid containing 60 lbs. of TiO2 is added 40 lbs. tion reveals this metatitanate to be of the of high grade zinc oxide, and thoroughly mixed. . ilmenite structural type, so that products ob (Mol ratio approximately 1.5 mols TiO2 per mol tained with proportions of more than 1 mol of ZnO.) The mixture is partially dewatered weight of TiO, as y-titanic acid to each mol of by filtration followed by drying at 100° C., and ZnO primarily show upon X-ray examination 20 then heated for four hours at 800° C. The prod the characteristic patterns of the ilmenite type uct is a white pigment of high brightness, of plus titanium dioxide, the titanium dioxide be good resistance to chalking, and excellent cov ing of the anatase or rutile modification accord ering power, and upon X-ray analysis exhibits ing to the temperature employed. When it is 25 a powder diffraction pattern containing sub known that the TiO2 present is in excess of the stantially only those lines which are charac theoretical for the molecular ratio TiO2 to ZnO, teristic of a zinc-titanium compound of the ill but TiO2 lines of titanium dioxide either in ana menite structure type, although chemical assay tase or rutile modification are not found in the reveals an excess of TiO2 over the ZnO necessary X-ray pattern, or are found to an insufficient to form ZnTiO3. degree, as indicated by the chemical proportions, 30 Eacample 2.-Illustrating method of prepara the excess is assumed to be in solid solution in tion of a pigmentary zinc titanate composition the titanate. of the type anatase plus acznTiO3.gTiO2, wherein Above 600 C., if the time factor' is sufficient, the TiO2 is in excess of that required by the zinc and we have found that a 2 hour heating period present to form ZnTiO3, and which upon X-ray is usually sufficient, there will be in the rhate 35 analysis exhibits both the patterns of hexagonal rial no unbound or free zinc oxide as determin ZnTiO3 of the ilmenite structure type and of TiO2 able by X-ray analysis, and one of the objects of of the anatase modification. - our inventon is to provide a material contain A quantity of y-titanic acid obtained by con ing unbound titanium dioxide but substantially tacting an aqueous solution of ammonium fluo no zinc other than as the titanate. 40 titanate, (NH4)2TiF6 with aqueous ammonia, Without wishing to be bound by theoretical washing, dewatering, and drying, and containing considerations as to the reason why titanium by analysis 90 pounds of TiO2 is dry mixed with dioxide in the form of y-titanic acid behaves en 10 pounds of higr grade zinc oxide (mol ratio tirely differently from titanium dioxide in the approximately 9 molls of TiO2 to 1 mol of ZnO). form of anatase in its reaction to temperatures . The mixture is heated at 725° C. for two hours. in the ZnO/TiO system, we believe that such The product upon X-ray analysis exhibited sub difference is a function of its inherently greater stantially only the characteristic patterns of a reactivity than those other forms of titanium zinc-titanium compound of the ilmenite struc oxide, even though the latter do possess sufficient ture type and titanium oxide of the anatase activity to be termed "reactive.' This is shown nodification. in that y-titanic acid may of itself be directly Eacample 3.-Illustrating the preparation of a converted to rutile at temperatures between 800 pigmentary Zinc titanate compound of the type and 900° C., without the addition of any fluxing rutile plus acznTiO3-yTiOa, wherein the TiO2 is or sintering agent, whereas the anatase type of 55. in excess of that required to form ZnTiO3, and prior art may be heated above 1000° C. without which upon X-ray analysis exhibits the char converting to rutile. acteristic patterns of both hexagonal zinc meta Where y-titanic acid is heated through an in titanate of the ilmenite structural type and ti creasing temperature range, it is converted, as tanium oxide of the rutile modification. shown by the X-ray, first into anatase at the 60 The mixture of ?y-titanic acid and zinc oxide lower temperatures, and then, as the tempera of Example 2 is heated for 4 hours at 900° C. ture reaches the vicinity of 750 to 800 C., into Upon X-ray examination the product exhibits the rutile modification. No difference between the characteristic patterns of a zinc-titanium the anatase obtained from heating y-titanic acid oxygen compound of the ilmenite structure type at temperatures below about 750° C. and the 65 and titanium oxide of the rutile modification. anatase obtained by calcination at Similar tem Ecample 4.- Illustrating the method of prepa peratures of the hydrous oxide produced by ther ration of a pigmentary zinc titanate composi mal hydrolysis of titanium sulphate solution has tion of the type acznTiOyTiO2 mixed with been found by the X-ray, but that an inherent 70 aczna TiO4-y'TiO2, and which upon X-ray analy difference does exist is demonstrated by the fact sis exhibits a pattern characteristic of a mix that at very slightly higher temperatures the ture of crystals of the spine and the ilmenite former is converted to rutile while the latter re structure type with those of ilmenite structure sists such conversion. . . predominating. The principles and practice of our invention 75 A quantity of Y-titanic acid obtained as in 6 2,879,019 Example 2, and equivalent to 100 lbs. of TiO2 Table IV is mixed with 50 lbs. of high grade zinc oxide. The mixture is heated for four hours at 850° C. Ingredients, percent Tinting Percent reflectance until a portion removed as a Sample exhibits upon X-ray analysis, substantially only the pat y-titanic Anatase Zno Strength Blue Amber Green terns characteristic of crystals of ilmenite struc 40 600 81.9 86.0 86.3 ture type with a minor amount of crystals of the 45 675 82.8 86.5 88.8 50 725 825 86.0 85.9 spine type. 55 775 84.4 87.4 88.0 Eacample 5.-Illustrating the use of zinc sul 0 () 825 84.6 87.8 88.2 65 925 85.4 87.8 88.5 phate instead of zinc oxide. 70 30 1025 85.9 88.4 89.0 A solution of zinc sulphate in Water was pre 75 25 1100 86.1 88.6 89.2

80 20 200 86.2 88.8 89.6 pared by adding sufficient purified crystal zinc 40 60 325 78.5 85.0 84.7 sulphate to water to be equivalent to 10 pounds 45 55 425 79.7 85.5 85.6 50 50 45 79.6 85.6 85.5 of ZnO in 100 pounds. Into this solution was 5 55 45 525 79.4 85.2 85.3 60 40 625 82.0 86.6 86.9 added a quantity of dried y-titanic acid contain 65 35 675 83.0 87.3 87.6 ing 500 pounds of TiO2, and the mass thoroughly 70 30 750 84.0 87.8 88.0 mixed in a blade mixer. The mass was then 75 25 800 84.0 87.7 88.0 heated at a temperature of 930° C. for a period 80 20 850 84.6 88.2 88.6 of four hours. The product was rutile associated 20 An examination of the columns will show the with a minor amount of a zinc-titanium-oxygen following. For equivalent mixtures of titania compound of the ilmenite structure type, and and zinc oxide those products obtained when y upon pulverization showed excellent pigmentary titanic acid was the starting material, possess properties of texture, color and hiding power. several more points of tinting strength than do Eacample 6.-A mixture was prepared in the 25 the corresponding products when anatase was same manner as in Example 5, except that zinc used as the starting material. chloride was used in place of 2inc sulphate. The The tinting strength of a white pigment is a mixture was heated for 4 hours at 800° C. and measure of its ability to whiten the tint of a the product was of pigmentary rutile associated colored pigment mixed with it, and is relative with a minor amount of a zinc-titanium-oxygen 30 in nature, being compared to a standard to compound of the ilmenite structure type. which is affixed an arbitrary value. The tint Eacample 7-The procedure of Example 3 was ing strength of the white pigments reported followed, except that anatase obtained by the herewith were determined in general accordance thermai hydrolysis of ilmenite sulphate solution with the method A. S. T. M. designation was used instead of y-titanic acid. Upon X-ray 35 D-332-36, with the exception that the Hoover examination the product showed the characteris automatic muller was used in place of the hand tic pattern of a zinc-titanium-oxygen compound mulling described in the procedure. Pastes were of the spinel structure type, and titanium diox prepared by mulling together the white pig ide of the rutile modification. 40 ment, ultramarine blue, and acid refined liriseed We have further found that the whole or a oil of 12.5 acid number. The proportions used part of the zinc in the mixture of ry-titanic acid were 1.500 grams of the sample pigment, 0.300 with zinc oxide or a compound of zinc which may gram of ultramarine blue and 1.25 cc. of oil. be converted to the oxide by heating, may he These quantities were given a preliminary mix replaced by magnesium, or by other metal ele 45 ing with a spatula, mulled for 150 revolutions of ment which will combine with the y-titanic acid the plates in the Hoover muller with a pick up upon heating to form a titanate of the type after each fiftieth revolution, and graded by RTOs, or which will to some extent go into solid by placing the paste on a glass slide between solution as the oxide in the titanate to give a similar smears of standards of higher and lower 5) strength, these standards having previously compound of the type acRTiO3. (R.Ti) O2, where been prepared in a similar manner as described R may be Zn, or other bivalent metal orCertain a mix for the preparation of the sample, except for ture of two or more bivalent metals. the amount of blue, which is increased or de very definite pigmentary advantages may be ob creased in 5% increments. The standard used tained by effecting the formation of these multi -55 was a commercial anatase titanium dioxide pig metal compounds of the ilmenite structural type ment which was arbitrarily assigned a tinting and solid solutions of metal oxides in such ti strength of 1250, and the methods of grading tanates. By proper proportioning of the metals. to standard and calculating the tinting strength different combinations of chemical and weather was in conformance with the A. S. T. M. desig ing resistance, chalking and fading resistance, O nation previously referred to. and color tones result. A marked superiority in Reflectance is the ratio of light reflected from color brilliance or tone and color strength is a sample to that reflected from a standard mag found in the products resulting from heating to nesium oxide under conditions of equal diffuse gether y-titanic acid and compounds of iron. illumination as viewed from a direction nor copper, nickel, manganese, or other bivalent s mal to the surface. The reflectance or percent metal, or mixtures of these compounds, which brightness of the samples in this series were produce colored titanates, as compared to simi determined upon a surface prepared as follows: lar treatment of similar mixtures with anatase. 1,500 grams of the pigment sample was mixed or this purpose the metal element may be and mulled with 3.86 cc. of a dammar, warnish. added as oxide, hydroxide, carbonate, stiphate, The pastes were then-drawn down over a black chloride, or other compounds which produce the andso arranged white surface as to byleave metans a wet of filma doctor of 0.003' blade oxideThe upon superiority heating. of the products made by our thickness. The fins were then dried. Re process will be apparent from the data given 'fectance was determined with the standard blue, the following table: . 75 green and amber filters of the Hunter Reflec 2,879,019 7 tometer. The procedure for the determination more than 4 mols of TiO, said heating being of the brightness or reflectance is described in at a temperature between about 600 and 775 C., the National Bureau of Standards Research and for a sufficient period of time to convert all Paper 1345. of the zinc present to zinc metatitanate of hex The anatase derived titanates were all def 5 agonal symmetry and of the ilmenite structure initely of poorer texture, i. e., harder and more type, and containing TiO2 in Solid solution. . . difficult to pulverize, than the corresponding y 5. Method of preparing a pigmentary material products. The X-ray analysis of all these com which comprises heating a mixture of y-titanic pounds corresponds to that which would be ex acid and a zinc compound selected from the pected from the diagrams of Figs. 2 and 3. () group consisting of zinc oxide and compounds of Having thus described our invention, what Zinc which yield zinc oxide on heating, in such we claim as new and desire to secure by Letters proportions that for every mol of ZnO in said Patent is: y mixture there will be present between 1 and 3 . Method of preparing a pigmentary mate mols of TiO2, said heating being at a tempera terial, which comprises heating a mixture of y ture between about 775 and 825 C., and until titanic acid and a zinc compound selected from upon X-ray examination of the material, among the group consisting of zinc oxide and com those lines of the diffraction pattern which are pounds of zinc which yield zinc oxide on heating, due to compounds of zinc, substantially only in Such proportions that for every mol of ZnO in those lines which are characteristic of a zinc said mixture there will be present more than : titanium-oxygen compound of hexagonal sym2 . one mol of TiO2, said heating being. at a tem rinetry and of the ilmenite structure type are perature between about 600 and 975 C., and found. until upon X-ray examination of the material, 6. Method of preparing a pigmentary material among those lines of the diffraction pattern which comprises heating a mixture of y-titanic which are due to compounds of zinc, substan dt acid and a zinc compound Selected from the tially only those lines are found which are char group consisting of zinc oxide and compounds acteristics of a zinc-titanium-oxygen compound of zinc which yield zinc oxide on heating, in such of hexagonal Symmetry and of the ilmenite proportions that for every mol of ZnO in said structure type, the mol ratio of ZnO to TiO2 mixture there will be present between 1 and 3 being between 1 to 1 and 1 to about 2.3 if the () mols of TiO2, said heating being at a tempera heating be to a temperature between 775 C. and ture between about 775 and 825 C., and until 825° C., and the mol ratio being 1 to more than upon X-ray examination of the material the dif about 2.3 if the heating be to a temperature be fraction pattern is found to contain substantially tween 775° C. and 975° C., and the mol ratio be-, only those lines which are characteristic of a zinc ing 1 to more than 4 if the heating be to a metatitanate of hexagonal symmetry and of the . temperature, of between 600° C. and 775 C. ilmenite structure type. 2. Method of preparing a pigmentary mate 7. Method of preparing a compound of the rial, which comprises heating a mixture of y general formula aznTiO3.yTiO2, which comprises titanic acid and a zinc compound selected from heating a mixture of y-titanic acid and a zinc the group consisting of zinc oxide and com 40 compound selected from the group consisting of pounds of zinc which yield zinc oxide on heat zinc oxide and compounds of zinc which yield ing, in such proportions that for every mol of zinc oxide on heating, in such proportions that ZnO in said mixture there will be present more for every mol of ZnO in said mixture there will than 4: mols of TiO2, said heating. being at a be present between 1 and 3 mols of TiO2, at a temperature between about 600 and 775 C., and temperature between 775 and 825. C., for a suff until upon X-ray examination of the material, cient period of time to convert all of the zinc among those lines of the diffraction pattern present to zinc metatitanate of hexagonal sym which are due to compounds of zinc, substan metry and of the ilmenite strutture type, and tially only those lines are found which are chair containing TiO2 in solid solution. acteristic of a zinc-titanium-oxygen compound 8. Method of preparing a compound of the of hexagonal symmetry and of the ilmenite general formula acznTiO3.yTiO2, and wherein the structure type. TiO2 in excess of that required to form ZnTiO3 3. Method of preparing a pigmentary material is in solid solution in the ZnTiO3, which com which comprises heating a mixture of yrtitanic prises heating a mixture of y-titanic acid and a acid and a zinc compound selected from the zinc compound selected from the group consisting group consisting of zinc oxide and compounds of of zinc oxide and compounds of zinc which yield zinc which yield zinc oxide on heating, in such zinc oxide on heating, in such proportions that proportions that for every mol of ZnO in said for every mol of ZnO in said mixture there will mixture there will be present more than 4 mols be present, between 1 and 3 mols of TiO2, at a 60 temperature between 775 and 825° C., for a suffi of TiO2, said heating being at a temperature be cient period of time to convert substantially all tween 600 and 775 C., and until upon X-ray of the zinc present to zinc metatitanate of hex examination of thematerial there is found in . agonal symmetry and of the ilmenite structure the diffraction pattern substantially only those . type, and containing. TiO2 in Solid solution. . lines which are characteristic of anatase and of 9. Method of preparing a pigmentary mate a zinc-titanium-oxygen compound of hexagonal rial which comprises heating a mixture of a zinc symmetry and of the ilmenite structure type, compound selected from the group consisting of . 4. Method of preparing a pigmentary anatase zinc oxide and compounds of zinc which yield associated with a zinc titanate of the general for zinc oxide on heating, and hydrous titanium mula acznTiO3-yTiO2, which comprises heating 70 oxide in the y-titanic acid modification, in such a mixture of y-titanic acid and a zinc compound proportions that for every mol of ZnO in said mix selected from the group consisting of zinc oxide ture there will be present more than about 2 mols and compounds of zinc which yield zinc oxide of TiO2, at a temperature between about 775 and on heating, in such proportions that for every 975 C., until upon X-ray examination of thema mol of ZnO in said mixture there will be present 75 terial, among those lines of the diffraction pats 8 2,379,019 tern which are due to compounds of zinc, Sub 16. A pigmentary composition which contains stantially only those lines which are character TiO2 in solid solution, and which upon X-ray istic of a zinc-metatitanate of hexagonal Sym examination produces a diffraction pattern con metry and of the ilmenite structure type are taining substantially only those lines which are found. characteristic of anatase titanium dioxide and 10. Method of preparing a pigmentary mate a zinc-titanium-oxygen compound of hexagonal rial which comprises heating a mixture of a zinc symmetry and of the ilmenite structure type. compound selected from the group consisting of 17. A pigmentary composition containing an zinc oxide and compounds of zinc which yield excess of TiO2 to ZnO over the theoretical re zinc oxide on heating, and hydrous titanium di O quired to form ZnTiO3, at least a proportion of oxide in the y-titanic acid modification, in such said excess of TiO2 being in solid solution, but proportions that for every mol of ZnO in Said which upon X-ray examination produces among mixture there will be present more than about those lines of the diffraction pattern which are 2 mols of TiO2, at a temperature between about due to compounds of zinc substantially only those 775 and 975° C., until upon X-ray examination 5 lines which are characteristic of zinc-titanium of the material there is found in the diffraction oxygen compound of hexagonal Symmetry and of pattern substantially only those lines which are the ilmenite structure type. characteristic of rutile, and of a zinc-metatitan 18. A pigmentary composition which upon X ate of hexagonal symmetry and the ilmenite ray examination produces a diffraction pattern structure type. 20 containing substantially only those lines which 11. Method of preparing a pigmentary rutile are characteristic of rutile titanium dioxide and associated with a zinc metatitanate of hexagonal a zinc-metatitanate of hexagonal symmetry and symmetry and of the ilmenite structure type and of the ilmenite structure type and having TiO2 of the general formula acznTiO3.gTiO2, in which a in solid Solution. and y are whole numbers and ac is greater than 25 19. A pigmentary composition which upon X y, which comprises heating a mixture of y-titanic ray examination produces a diffraction pattern acid and a zinc compound selected from the group containing substantially only those lines which consisting of zinc oxide and compounds of Zinc are characteristic of anatase titanium dioxide as which yield zinc oxide on heating, in such pro sociated with a minor amount of zinc metatitan portions that for every mol of ZnO in said mix 30 ate of hexagonal symmetry and of the illmenite ture there will be present more than 2 mols of structure type and having TiO2 in solid solution. TiO2, at a temperature between 775 and 975 C. 20. A pigmentary composition which upon X 12. Method of preparing a pigmentary rutile ray examination produces a diffraction pattern associated with a minor amount of zinc meta containing substantially only those lines which titanate of hexagonal symmetry and of the 35 are characteristic of rutile titanium dioxide as ilmenite structure type, which comprises heat sociated with a minor amount of a zinc meta ing a mixture of y-titanic acid and a zinc com titanate of hexagonal symmetry and of the pound selected from the group consisting of zinc ilmenite structure type and having TiO2 in solid oxide and compounds of zinc which yield zinc solution. oxide on heating, in such proportions that for 40 21. A pigmentary composition composed es every mol of ZnO in said mixture there will be sentially of TiO2 and ZnO in the ratio of 1 mol present more than 4 mols of TiO2, at a tempera of ZnO to at least about 2 mols of TiO2, and ture between 775 and 975 C. which, upon X-ray examination, produces among 13. Method of preparing a composition of ... the lines of the refraction pattern which are due matter consisting of rutile associated with a to compounds of zinc, substantially only those solid solution of titanium dioxide in zinc meta lines which are characteristic of zinc metatitanate titanate in variable proportions ac2nTiO3. TiO2, of hexagonal symmetry and of limenite struc and which mixture exhibits upon X-ray exami ture type, and said compound containing TiO2 nation a diffraction pattern comprising substan in solid solution. tially only those lines which are characteristic 50 22. A pigmentary composition composed essen of rutile, and of a zinc-titanium-oxygen con tially of TiO2 and ZnO in the ratio of 1 mol of pound of hexagonal symmetry and of the ZnO to at least about 4 mols of TiO2, and which, ilmenite structure type, which comprises heat upon X-ray examination, produces among the ing a mixture of y-titanic acid and a zinc com lines of the refraction pattern which are due to pound selected from the group consisting of zinc compounds of zinc, substantially only those lines oxide and compounds of zinc which yield zinc which are characteristic of zinc metatitanate of oxide on heating, in such proportions that for hexagonal symmetry and of ilmenite structure every mol of ZnO in said mixture there will be type, and said compound containingTiO2 in solid present more than about 2 mols of TiO2, at solution. temperature between 775 and 975. C. 23. A pigmentary composition composed es 14. A white pigment comprising zinc meta sentially of TiO2 and ZnO, and in which all of titanate of hexagonal symmetry and of the the zinc is present as zinc metatitanate of hexag ilmenite structure type containing titanium di onal symmetry and of ilmenite structure type, oxide insolid solution. and containing some TiO2 in solid solution and 15. A white pigment comprising a mixture of some free anatase. titanium dioxide in the rutile form associated with titanium dioxide in solid solution in zinc ANDREW T. McCORD. metatitanate of hexagonal symmetry and of the HAROLDF. SAUNDERs. ilmenite structure type. -