- Patented Jan. 7, 1936 2,026,862

UNITED STATES " PATENT OFFICE

7 2,026,862 PREPARATION or TITANIUM PIGMENTS Joseph Blumenfeld, Paris, France, and Max Mayer, Karlsbad, Czechoslovakia, assignors to Krebs Pigment & Color Corporation, Newark, N. J., a corporation of Delaware No Drawing. Application May 15, 1930, ‘ Serial No. 452,810 12 Claims. (Cl. 134-—58) This invention relates to improvements in the ‘calcining steps, result in a product having in preparation or manufacture of titanium pigments . creased durability and decreased oil absorption. ‘and, the improved products resulting from such The oxides and hydroxidesof the tetravalent improved process. ' rare earths of the titanium-thorium family, which 5 Titanium pigments have been used extensively family also includes zirconium and cerium, have 5 as substitutes for other pigments and have shown suitable characteristics for use in this connection a general superiority over such pigments, espe and may be applied to the titanium oxide by pre cially when compared to other white pigments. cipitation or coagulation from solutions in which They are, however, inclined to become powdery the titanium oxide is suspended. 10 or to “chalk off” and this characteristic makes We have also found that an improvement in 10 them objectionable for use where they will be the sintering of the above composite pigment or exposed to the weather. of the titanium oxide alone, may be accomplished ' This application is a continuation in part of by effecting the sintering in an acid atmosphere ' our 'copending applications Serial Numbers 2,233 produced by freeacids or by the heating of salts 15 and 2,234, ?led January 13, 1925. of an acid character. It is preferable to use for 15 It is an object of the present invention to pro- ' this purpose salts whose residues may be re vide a process for preparing a titanium pigment moved by washing the calcined product. Magne of improved characteristics and one which may sium chloride, ammonium sulphate, and alkali 0 be safely used where it will be exposed to the salts are examples of substances suitable for this weather. It is another object to provide a method purpose. for preparing a pigment having greater durabil In carrying out our improved process, the ti ityand one which will not be subject to the above tanium oxide may be mixed with the rare earth defect. It is also an object of the invention to ,compound, preferably the hydroxide or oxide in 25 improve the quality of vthe pigment by controlling colloidal solution, and the rare earth oxide or the conditions under which it is sintered. An hydroxide may be deposited upon, and within the 25 other object of the invention is to produce a new pores of, the particles of titanium oxide either by pigment of improved characteristics. Other ob precipitation or coagulation. The composite pre jects will become apparent. _ cipitate resulting from the ?lling of the pores so The ‘invention, broadly stated, comprises add of the titanium oxide with the rare earth oxide ing to precipitated titanic acid, substances which or hydroxide may then be calcined at 800-1000° 30 will improve the characteristics of the pigment C. to give it the desired pigment properties. resulting from the calcining .operation. It also Titanium oxide'adaptable to be pore ?lled as includes the addition of substances adapted to described herein may be obtained conveniently 35 fill and remain in the interstices or pores of the from the main titanium product of. the process F titanium pigments as well as the addition of ma described in United States Patent 1,504,672, but 3° terials adapted to assist in the sintering action tetravalent oxides of titanium obtained by pre but which materials may be subsequently washed cipitation and having any degree of hydration are from the pigment. , also suitable and can be used in the present case. 40 In view of the pigmentary qualities required in 'Further, these oxides and hydroxides may or may the ?nished product, the materials added to ?ll not be dried and/or calcined beforeithey are the interstices or pores should have the essential put in suspension in the solution. In cases where characteristics of pigments or at least they the oxide has been calcined it is, of course, pref should not detrimentally affect the pigmentary erable to bring it ?rst to a fairly ?ne state of qualities of the product. It is also desirable that division. ' 45 45 the material used for this purpose be'one which In order to describe our invention more clearly, may be applied to the titanium oxide by precipi the following speci?c examples are given. It is tation or coagulation from the solution in which not intended, however, to restrict the invention the latter is suspended and one which will with to the particular conditions and proportions re 50 stand the calcination‘ to which the composite cited, since it is apparent that these examples are 50 pigment is subjected. The ?lling or closing of the .only illustrative and many modi?cations may be interstices or pores of the titanium oxide by the made to obtain the desired improvement. deposition of the ?nely divided particles resulting .from the coagulation or precipitation, and thev I Example I . ' . 55 retention of these particles during the drying and About '1 to 10 parts by weight of ?nely ‘ground, 5 2 2,028,862 preferably calcined, titanium oxide is suspended ing acid may be removed by treating the moist in 100 parts by weight of a solution of titanium or dry product with an oxide of a metal capable or titanyl sulphate containing about 200 grams I of reacting with the sulphate, for example, zinc of titanium oxide per litre. This sulphate solu oxide or magnesium oxide. A considerably ‘ tion may be obtained by the customary procedure smaller quantity of potassium bisulpliate, for ex- 5 of treating ilmenite with sulphuric acid. The ample as little as 2% of the weight :of titanium mixture is heated to hydrolytically precipitate ' oxide, may be used. titanium oxide from the sulphate solution upon the suspended titanium oxide. The heating may, Example V 10 be done under atmospheric or increased pressure As another example of the heating of titanium 1,0 and a re?ux cooler may be used if it is desired oxide with an alkali salt, 10 parts by weight of to prevent evaporation. moist titanium hydroxide, obtained from a neu The pore-?lled titanium oxide is separated from tral or basic titanium sulphate solution, are inti the solution, for instance, by ?ltering, and may mately mixed with about 0.5 parts by weight of 15 be washed to free it from acid, and calcined at potassium carbonate, and the mixture is heated 15 about 800-1000“ C. for a suitable time, for example, two hours, at a Example II temperature of about 800-1000° C. The calcined material is washed ?rst with water to remove the About 10 parts by weight of calcined titanium potassium sulphate and then with mineral acid 20 oxide are ?nely ground and mixed with 7 parts until completely neutral and is then dried. A 20 by weight of a colloidal thorium solution contain considerably smaller quantity of potassium car ing about 300 grams of thorium oxide per litre bonate-may be used, for example, very satisfactory of solution. The water of the mixture is evapo results are obtained by using potassium carbonate rated and calcination is effected at red heat. in the proportion of .5% of the titanium oxide. 25 The calcined product may be cooled and ground If the oxide, referred to in the above examples, 25 in a wet or dry condition. , , is obtained by precipitating titanium sulphate The calcining of the titanium dioxide before solution, it will contain sumcient sulphuric acid depositing the thorium oxide gives the particles 9. to convert the alkali carbonate to a sulphate. A de?nite structure upon which the pore ?lling me. similar result may be obtained by adding an 30 terlal may be deposited. It is apparent that a‘ alkali hydroxide. 30 similar improvement may be accomplished by The improvement in‘ whiteness of the pigment adding the ?nely ground calcined titanium oxide resulting from the calcining in the presence of an to a colloidal solution of titanium oxide and co- ' alkali salt does not seem to be dependent upon agulating the colloidal titanium dioxide. the presence of the sulphate radical, since similar 36 If preferred, the titanium or thorium oxide may improvement may be accomplished by heating in 35 be coagulated by heating and the water may be the presence of other alkali salts. Improvements separated from the suspended material by de in results may be accomplished by adding the al canting and/or ?ltering, after which the com kali salt in proportions up to about 2% of sodium posite solids may be calcined and ground. salt, but the addition of a greater amount does 40 An improved result may also be obtained by not greatly improve the whiteness of the product. 40 using moist precipitated titanium dioxide, con The quantity of water soluble salt present during taining about 50% water, in place of the calcined the calcining may be regulatedby controlling the material referred to in the above illustrations. concentration of the solution from which the solids are separated or by washing the separated a Sample III solids so as to remove a portion only of the water 45 The pore-?lled titanium oxide, referred to in soluble salt. ' the above examples, may be calcined in the It is apparent that various modi?cations and presence of a salt. For example, a small quantity combinations of the above illustration may be of colloidal titanium or’thorium oxide may be used and that the quantities may be varied and 60 mixed with titanium oxide and this mixture may it is not intended to restrict the invention to the 50 be dispersed in sodium sulphate solution. The particular embodiment described. In the ap sodium sulphate. will coagulate the colloidal pended claims the term titanium-thorium family titanium or thorium oxide and the water may is used to include these elements, together with then be evaporated or otherwise separated from zirconium and cerium. 55 the mixture of solids which may then be calcined The sintered product produced according to 55 by heating to about 800-1000° C. After the cal the above processes, or modi?cations of these cining the sodium sulphate remaining upon the processes, may be ground wet or dry and mixed _ pigment may be separated by washing the .cal with the usual diluting agents and ?llers, such cined mixture. If desired, other salts, such as as barium sulphate, zinc oxide and others, to '30 potassium carbonate, may be substituted for the produce a durable primary material for paints 6° sodium sulphate. and other covering materials and one which may ~ ' Example IV be applied where it is to be exposed to the An improved product will also result from sin weather. " 65 taxing the titanium oxide with a salt, without What we claim is: 65 the addition of a pore-?lling material. As an il- - 1. A process for the manufacture oi’ titanium lustration, 10 parts by weight of titanium oxide in pigments which comprises suspending titanium a moist or dry condition are intimately mixed dioxide particles in a solution of a thorium com with two parts by weight of potassium bisulphate pound, and heating said solution and thereby 70 and the mixture may be calcined at a tempera hydrolytically precipitating thorium dioxide on 70 ture of 800° to 1000° C. The sulphuric and sul said suspended particles. ' . » phurous acid given oif during the heating may 2. A process for the manufacture of titanium be collected and utilized. After heating, the pigments which comprises suspending particles potassium sulphate is extracted from the calcined of titanium dioxide in a solution of a thorium 75 materials by washing with water and any remain compound, heating said solution and thereby hy- 76 v 2,026,862 3 drolytically precipitating thorium dioxide on ing said suspension to precipitate a zirconium said suspended particles, separating said mixture oxide in the presence of said titanium dioxide. from solution, freeing said mixture from acid, 8. A calcined composition for use as a pigment and calcining the same. comprising titanium dioxide having zirconium I 3. In a process for the production of a titanium oxide in its pores. - ~ pigment the steps of suspending particles of 9. A calcined composition for use as a pigment titanium dioxide in a solution of a compound of comprising titanium dioxide having thorium ox one of the elements selected from the group of ide within its‘ pores. ' elements consisting of cerium, thorium and zir 10. In’ a process for the production of a ti 10 conium, and treating said suspension to precipi tanium pigment the steps of suspending particles 10 tate an oxide of one of said elements in the pres of titanium dioxide in a solution of a compound ence of said titanium dioxide. of one of the elements cerium, thorium and zir 4. A calcined composition for use as a pig conium, treating said suspension to precipitate ment comprising titanium dioxide having an ox an oxide of one of said elements in the presence ide of- one of the elements selected from the of said titanium dioxide and calcining said 15 group of elements consisting of cerium, thorium» mixture. ' ’ and‘ zirconium within its pores. 11. In a process for the production of a ti 5. In a process for the production of a titanium tanium pigment the steps of suspending particles pigment the steps of suspending particles of ti of titanium‘dioxide in a solution of a cerium com 20 tanium dioxide in a solution of a cerium com pound, treating said suspension to precipitate an 20 pound and treating said suspension to precipitate oxide of cerium in the presence of said titanium a cerium oxide in the presence of said titanium dioxide and calcining said mixture. 12. In a process for the production of a ti-‘ _ _ dioxide. 6. A calcined composition for use as a pigment tanium pigment the steps of suspending particles 25 of titanium dioxide in a solution of a zirconium 25 comprising titanium dioxide having cerium oxide compound, treating said suspension to precipitate within its pores. ' ‘ a zirconium oxide in the presence of said titanium 7. In a process for the production of a titanium dioxide‘ and calcining said mixture. pigment the steps of suspending titanium dioxide JOSEPH BLU'MENFELiD. 30 in a) solution of a zirconium compound and treat MAX MAYER. 30