Патент USA US2113945код для вставки
2,113,945 Patented Apr. 12, 1938 UNITED STATES PATENT OFFICE Walter WI Pleohner, Piney' River, Va, and Arthur W. Hixson, Leonia, N. 1., assignors to National Lead Company, New York. N. Y... a corporation of New Jersey No Drawing. ‘ ‘ Application November 23, 1934, Serial No. 754,454 13 Claims. , (on. 23-202) ' a . ly ?nely‘ divided, condition, and, therefore, has been extremely dl?icult to ?lter and impossible to wash free from impurities contained in the Our present invention generally relates to ti tanium oxide pigments having improved proper ties,_ and more speci?cally to a novel method of mother liquor. This extreme ?neness of particle - - , producing a pigment of this type. It is believed that the hiding power of a pig size and di?lculty in washing has resulted in ment is some function of the refractive index among other properties; the greater the differ ‘calcined products of very poor color and very low hiding power, entirely unsuitable for use as ence between, the refractive index of the pigment . pigments. a pigment. ‘ ‘ We have discovered that under suitable condi tions, to be disclosed below, titanium dioxide 10 and that of the vehicle in which it may be sus 10 pended the greater will be the hiding power of the pigment. In this way is partially explained the relatively high hiding power of the titanium adapted to pigment uses can be precipitated from atitanium chloride solution. Furthermore, pi-g ment’ so obtained shows a remarkably improved tinting strength and hiding power over titaniumv Thus the refractive indices of a few of the common white pigments are: 15 Titanium dioxide (anatase) _____________ __l 2.55' .oxide pigments hitherto offered in the trade. 15 Thus, if tinting strength is'determined by the Zinc sulphide 2.37 tentative method oi test of the American Society Lead basic carbonate_______’_ __________ _-__ 1.99. of'Testing Materials, A. S. T. M. Designation: . Zinc oxide ' 1.90 D332-31T, A. 8. T. M. Tentative Standards 1933,‘ Blane ?xe Linseed oil 1.64v - 1.49 525, the highest value shown ‘by old commercial products is about 1100-1200, whereas our pig 20~ ment gives values of MOO-1500. The hiding pow- , Titanium dioxide which has hitherto been com mercially prepared has always been precipitated ' er of our form of titanium dioxide is correspond by the hydrolysis of sulphuric acid solutions of» ingly greater. We now ascribe this to the fact titanium, and, as has been shown by Weiser and that our pigment is in the rutile modi?cation 25 ' Milligan: J. Phys. Chem. 38, 513 (1934), such an since it is precipitated from a‘ chloride solution, and has. therefore, a higher refractive index than the ordinary titanium dioxide pigment. oxide always exists as the anatase modi?cation which has the refractive index indicated in. the above tabulation. 30 ' _ It has been long known that therefractive in dex of the rutile modi?cation of titanium dioxide is 2.71, and, therefore, if titanium dioxide could be so precipitated as to form rutile’ on calcine tion, and, furthermore, if the precipitation con It may be stated, therefore, that it is one of the primary objects of the present invention to provide a titaniuinoxide compound which. pos sesses tinting strength and hiding power greatly improved over similar types of pigments ‘hitherto used, and which compound is readily derived 35 ditions, or “hydrolysis conditions” as it is fre irom. a titanium chloride solution. We have discovered that titanium dioxide may quently called in the art, 'were such as to form particles which on calcination were suitable for be precipitated from a chloride solution in a formv pigment purposes, a new white pigment far su . highly suitable'for use as a pigment if the pre perior in hiding power to’the pigment grade cipitation, or hydrolysis, is carried on under such titanium oxides now commercially available conditions as to give relatively rapid precipita 40 would have been obtained. " It, also, was shown by Weiser and Milligan in the publication cited above that'when titanium dioxide is precipitated from a chloride solution 45 the rutile modi?cation is always obtained. Ti tanium dioxide has not been prepared under such conditions in the past because until the time of our discovery it was not known how to precipitate the oxide from a chloride solution 50 and obtain the other properties, (purity, white ness, proper particle size, ?lterability, etc), nec essary for the production of a material suitable for pigment purposes. Titanium diomde which has been precipitated from chloride solutions by others has usually been in a pept, or extreme tlon in the presence of coagulants which prevent the well-known peptizing action of the chloride ion. Such suitable conditions involve the addi tion of relatively concentrated aqueous solutions of titanium tetrachloride to'a boiling solution of 45 water containing a very small amount of coagu-‘ lant. We have found that negative divalent ions, as for .exampleoxalate, tartrate or sulphate, be have as coagulants and cause the hydrous tita 50 nium omdes to be precipitated in a readily ?lter able and easily ed state, and when so pre cipitated the titanium dioxide obtained after calcination has rerkably high hiding power and tint streth m is comparable in all 55, 2,113,945 2 other respects to the titanium pigments previous ly available. > ‘ Hence, it is pointed out that another impor tant object of the invention is to provide tita 5 nium dioxide in the rutile modi?cation, the com pound being in a non-peptized state and hem! characterized by its readily ?lterable condition. Another advantage of our process is that the titanium oxide prepared by our method is ‘of 10 unique purity. We have not been able to detect any impurities ‘in our product by any chemical speci?c description is but illustrative of a typical embodiment of our invention, and that various changes may be made in the various ingredients, steps, temperatures, quantities of the process, and the uses of the resulting product, without depart» ing from the spirit of the invention as set forth in the following claims. What we claim is: 1. Process for the preparation of ‘pure titanium dioxide having rutile crystalline structure which 10' comprises hydrolytically precipitating non-pep means known to us. On the other hand titanium tized, easily ?lterable, hydrous titanium oxide “ oxides precipitated .from sulphuric acid solutions. from an aqueous titanium tetrachloride solution , containing a small amount of a negative, divalent analyze about as follows: coagulating ion, separating the said hydrous 15 15 . Per cent titanium oxide and calcining it to rutile crystal Titanic oxide ____________________ __ 98.3 -99.2 Sulphuric anhydride_____________ .._ Ferric oxide; ___________________ __ Phosphoric ,anhydride_'_ __________ __ 20 Water soluble _______________ _'____- 0.010.010.190.23- 0.81 0.02 0.31 0.62 line structure. comprises adding an aqueous solution of titanium ,20 tetrachloride to hot water containing a small amount of a negative, divalent coagulating ion, heating the mixed solutions to hydrolytically precipitate non-peptized hydrous titanium oxide in readily fllterable form, separating the so ob 25 to. . It is to be further understood that the fol 25' tained hydrous titanium oxide and calcining it to lowing detailed disclosure of the mode of practis ing our invention is addressed to those skilled in the art of preparing titanium oxide pigments; rutile crystalline structure. , _ 3..Process for the-preparation of pure titanium dioxide having rutile crystalline structure which such skilled persons are fully aware of the ap comprises hydrolytically precipitating non-pep tized, easily ?lterable hydrous titanium oxide paratus and manipulations usually utilized in the art ocl - ‘ dioxide having rutile crystalline structure which In order that our method of preparation of pure titanium dioxide in the rutile modi?cation may be more readily understood we give an example in. de tail, although we do not wish to be limited there 30 . 2. Process for the preparation of pure titanium titanium compounds. from an- aqueous solution of titanium tetra Titanium tetrachloride is .obtained by the chloride containing a small amount of a. coagu- . chlorination under reducing conditions of titanif lant selected from the‘group consisting of the erous materials. The operation may be carried acids and alkali metal salts of the sulfate, tar 35 35 out so as to yield titanium chloride containing but trate and oxalate radicals, separating the said relatively small amounts of impurities. The ti hydrous titanium oxide and calcining it to rutile tanium tetrachloride is then dissolved in two crystalline structure. volumes of cold water yielding a clear aqueous 4. ‘Process for the preparation of pure titanium 40 chloride solution of titanium containing about 15 40 per cent titanium oxide. All the iron present is dioxide having rutile crystalline structure which comprises adding an aqueous solution of titanium reduced to the ferrous condition in order to pre tetrachloride to hot water containing a . small vent the hydrolysis which ferric salts readily amount of a coagulant selected from the group undergo. This reduction'may be accomplished consisting of the acids and alkali metal salts ‘many of the known methods, such as by the in 45 45 troduction of metallic zinc; In order to insure the of the sulfate, tartrate and oxalate radicals, heat ing the mixed solutions to hydrolytically precipi absence of ferric iron throughout the precipita tate. non-peptized hydrous titanium oxide in tion. we prefer to the solution to a'content readily ?lterable form, separating the so obtained of two to three grams per ‘liter of titanium oxide hydrous ‘titanium oxide and calcining it at a tem the titanous state. ' ~ . perature between 700° C. and 1000° C. to rutile 50 in Having 1000 pounds 8 chloride solution con crystalline structure. ' taining 15 per cent titanium. oxide, this is added 5. Process for the preparation of pure titanium to 10,000 pounds of boiling water containing 10 dioxide having rutile crystalline structure which -‘ pounds of oxalic acid during about one hour. comprises adding an aqueous solution of titanium When the addition has been completed about 95 tetrachloride to hot water containing a small 55 55 per cent of the titanium will have been precipi amount of a coagulant selected'from the group tated as hydrous titanium dioxide; the latter is consisting‘ of the acids and alkali metal salts in a coagulated form such that it settles well and I of the sulfate, tartrate and oxalateradicals, heat i may be readily filtered and washed. ‘ After ?ltra ing the mixed solutions to hydrolytically pre , tion and washing the precipitate is converted to cipitate non-peptized hydrous titanium oxide in 00 the anhydrous rutile form by calcining at a tem readily ?lterable form, separating the so ob- .. perature of from 700° to 1000° C. tained hydrous titanium oxide and calcining it While in the above example oxalic acid has been at a temperature between ‘700° C. and 1000° C. used as the coagulant any substance dissociating j to form a product possessingl'rutile crystalline so as to produce a divalent negative ion in aqueous 05 solution, sulphuric acid for example, may be used. structure, a tinting strength between 1400 and 1500' as determined by A. S. T. M. method, Tartarlc acid, in addition to the oxalic’ and sul D332-31T, covering power, whiteness, particle furic, dissociates so as to produce a divalent nega tive ion in aqueous solution and at the same time size, and brightness rendering" said product adaptable for pigment uses. alkali solution, e. g_., sodium sulfate Na?sod, sodium oxalate N??ciod, sodium tartrate NaaCaHrOa etc., may be used. .15 ' _ 6. Process for the preparation of pure tita 70 nium. dioxide having rutile crystalline structure which comprises adding an aqueous solution of 70 is compatible with the strongly acid solution used. Solutions of these acids, most conveniently the _ titanium tetrachloride to hot water containing ‘a small amount of. the sulfate ion, heating It will be understood that the aforegoing the mixed solutions to hydrolytically precipi- ' 8,118,946 3. tate non-peptized hydrous titanium oxide in readily ?lterabie form, separating the so ob tained hydrous titanium oxide and calcining it includas hydrolytic precipitation 01' hydrous tita at a temperature between 700° C.'and 1000“ ‘C. ‘ing an aqueous titanium tetrachloride solution containing a ‘small amount of a coagulant se 6 to ,rutile crystalline structure. 7. Process for the‘ preparation oi’ pure tita— nium dioxide havingrutile crystalline structure which comprises adding an aqueous solution of nium oxide irom an aqueous titanium tetrachlo ride solution, the step which consists in heat lected from the group consisting of the acids and alkali metal salts oi’ the sulfate. tartrate and oxalate radicals to hydrolytically precipitate titanium tetrachloride to hot watercontaining a non-peptized, readily ?lterable hydrous titani small amount of the tartrate ion, heating the mixed solutions to hydrolytically precipitate non um oxide. 10 11. In a processvi'or the preparation of pure peptized hydrous titanium oxide in readily ?l titanium dioxide having rutile structurev which terable form, separating the so obtained hy includes hydrolytic precipitation of hydrous tita drous titanium oxide and calcining it at a tem nium oxide from an aqueous titanium tetrachlo perature between 700° C. and 1000° Q. to rutile ~rlde solution, the. step which consists in heat 15' crystalline structure. ing an aqueous titanium tetrachloride solution 8. Process for the preparation of pure tita containing a small amount oi the sulfate ion to nium dioxide having rutile crystalline structure hydrolytically precipitate non-peptized, readily which comprises adding an aqueous solution of titanium tetrachloride to hot water containing‘ a small amount of the oxalate ion, heating the‘ mixed solutions to hydrolytically precipitate non peptized- hydrous titanium oxide in readily ?i terable form, separating the so obtained hydrous illterable hydrous titanium oxide. 0 12. In a process for the preparation of pure titanium dioxide having rutile structure which’ includes hydrolytic precipitation of hydrous tita- , nium oxide from an aqueous titanium tetrachlo ride solution, the step which consists in heat titanium oxide and calcining it at a tempera- _‘ ing an aqueous titanium tetrachloride solution ture between 700° C. and 1000" C. to rutile crys containing a small amount 0! the tartrate ion to talline structure. .hydrolytically precipitate non-peptized, readily 9. In a process for the preparation oi’ pure ?lterable hydrous titanium oxide. titanium dioxide having rutile structure which 13. In a process for the preparation oiv pure ‘ includes hydrolytic precipitation of hydrous tita nium oxide from an aqueous titanium tetrachlo titanium dioxide having rutile structure which, includes hydrolytic precipitation 01' hydrous tita ride solution, the step which consists in heating nium oxide from an aqueous titanium tetra an aqueous titanium tetrachloride solution con taining a. small amount of a nega heating an aqueous titanium-tetrachloride solu tive,.divalent ion to hydrolytically precipitate non-peptized. readily ?lterable hydrous titanium ion to hydrolytically precipitate non-peptised, oxide. 10. In a process for the preparation of pure titanium dioxide having rutile structure which chloride solution, the step which consists in tion containinga small amount of the oxalate readily ?lterable hydrous titanium oxide. ' . vWilli-‘1211112 W. PLECHNEB. ARTHUR W. B12808.