Patented May 2, 1939 2,156,727

UNITED STATES PATENT OFFICE 2,156,72 BLUE PIGMENT COLORS AND A PROCESS OF PREPARNG THEV Erich Korinth, Frankfort-on-the-Main-Hochst, and Georg Medler, Murasier, Germany, assign ors to H. G. Faroenindustrie Aktiengesellschaft, Frankfort-on-the-Main, Germany No Drawing. Application August 31, 1934, Se ria No. 42,346. in Germany September 13, 933 Clains. (C. 134-58) The present invention relates to blue pigment fate to run into an aqueous suspension of colors prepared from and to a carbonate which simultaneously contains the proceSS of preparing them. Salts of in a dissolved condition. The We have found that a new kind of stable blue precipitate then contains a sufficient quantity of s pigment colors can be prepared in an economical manganese compounds, so that in the Subsequent nanner from barium Sulfate With the aid of man heating process the desired blue color may be ganese. COnpounds. These pigment colors fulfil obtained. It is particularly advantageous fur the highest requirements. thermore to add a Substance having a basic ac The characteristic feature of the new proceSS tion, for instance barium carbonate and to carry O consists in heating barium Sulfate together With Out the process in an oxidizing melt; the blue O manganese compounds So as to obtain a thermic pigment thus produced has a particularly deep reaction, under Such conditions as lead to the color. production of the MnO4 group or counteract itS The barium sulfate may also be produced only decomposition. This can be attained, in a man during the heating process, for instance from 5 ner in itself known, by carrying out the heating barium carbonate or barium nitrate and sodium 5 process in the presence of basic Substances and Sulfate. It is likewise possible to start from the not too high a temperature. The temperature finished, precipitated barium sulfate. which is most Suitable is between about 400 C. It may be particularly advantageous to start and about 850° C. Furthermore it is advisable With the cheap heavy spar if it is finely ground. 20 for the maintenance or the formation of the In this case it Suffices for instance to mix the 20 MnO4 group to carry out the heating proceSS heavy Spar powder With a Solution of the de either with access of air or oxygen or in the pres Sired manganese compounds, to add a Small ence of a substance having an Oxidizing action, quantity of basic Substance and oxidizing flux Such as a nitrate. (preferably barium carbonate and barium ni 25 As basic substances, there may advantageously trate) and to heat the mixture to incandescence 25 be used particularly basic barium compounds, for about half an hour to one hour, for instance such as barium carbonate, barium hydroxide or at about 700 C. v . An addition of basic Substances If the manganese compound has not been com may, however, also be dispensed with, if con pletely bound to the barium sulfate, green to 30 pounds are present which, by the action of the brown Colors first appear which can readily be 30 high temperatures, produce a basic compound, renoved by an after-treatment with an acidified for instance barium nitrate. The manganates Solution of a bisulfite of an alkali or alkaline and permanganates of the alkali metals and al earth metal Or With Sulfurous acid. The previ kaline earth metals likewise produce alkaline Ously COWered blue coloration then appears in a 35 Substances during the heating process. Conse complete purity. 35 quently, they can be caused to react with the In many cases it is Sufficient to carry out the barium Sulfate without any further addition; purification by the addition of dilute nitric acid during this process they simultaneously act as to the finished fused maSS Without adding a par compounds providing manganese and alkali. ticular reducing agent. AS Soon as the purifica 40 As to the quantitative proportions, it is Suit tion is complete, the acid and the manganese 40 able, for instance if potassium manganate or po Which has been dissolved, are removed by de tassium permanganate are used, to add up to 15 Canting. It has been found to be advantageous per cent. of these compounds to the barium Sul not to use Water for the decanting process, but a fate before the heating process. In a cases it Salt Solution by Which the Solubility of the bari is advisable to mix as intimately as possible the 45 barium sulfate and the manganese compound Un Sulfate is repressed, that is a solution of sul used, so that the latter is homogeneously dis fate salt, or preferably barium salt, for instance tributed in a particularly fine state in the total barium nitrate. There is thus prevented a too quantity of barium Sulfate. far-reaching attack; the Velocity at which the The process may be carried out for instance as dispersed particles deposit at the bottom is simul 50 follows: The barium sulfate is precipitated in the taneously increased. If the acid has been re presence of the manganese compounds, for in noved in this manner, the product can be further stance manganese nitrate, KMnO4, K2MnO4, treated by Washing and drying operations. It is BaMnO4, or the like. It is sufficient for this pur advisable however, to add a Small quantity of 5 pose to cause or a solution of a sul barium carbonate to the product in order to cre 55 2 2,156,727 ate a buffer against later actions of stronger (5) An intimate mixture of 710 grams of cal acids. cined sodium sulfate, 1.3 kilos of barium nitrate, The barium carbonate may be added SubSe 50 grams of potassium permanganate and 150 quently or it may be precipitated upon the de grams of barium hydroxide is fused for about 2 5 posited pigment. The addition of barium car hours at 500 C. The fused maSS obtained is bonate acts by its neutralising effect and by the further treated as described in Example 3. There reduction of the solubility of the barium sulfate is obtained a light-blue pigment. owing to the formation of barium bicarbonate by (6) 280 grams of sodium sulfate containing the action of acid. Water of Crystallization, 50 grams of caustic SOda, 10 The color pigments prepared according to the 25 grams of calcined sodium carbonate and 65 () described process appear to be crystals of barium grams, of potassium manganate are dissolved at sulfate, in the lattice construction of which bari 35° C. to 40° C. in 1000 grams of water. The un manganate is embedded. The color pig solution is filtered and caused to run slowly, while ments are completely fast to light, insoluble and vigorously stirring, into a boiling solution of 700 15 resistant to atmospheric conditions. They are grams of barium nitrate and 25 grams of caustic 5 distinguished by the excellent purity of their soda, and 2000 grams of Water. The violet precip color and a Small content of black and more itate obtained is filtered by Suction and intimately over by the known good pigmentary properties kneaded, without previously Washing it, With 100 of the barium sulfate. The following examples grams of finely pulverized barium nitrate. The 20 Serve to illustrate the invention, but they are mass is then dried and the dried cake which has 20 not intended to limit it thereto: been reduced to Small pieces is heated for about (1) 5 kilos of potassium manganate or potas 45 minutes at 690 C. in a covered Crucible. The sium permanganate and 25 kilos of barium ni product obtained is then treated with 1 liter of wa trate are together dissolved in 500 liters of water. ter and finely ground. The Suspension is mixed, The Solution is precipitated at boiling tempera while stirring with nitric acid until an acid reac 25 ture, while vigorously stirring, with a solution of tion is obtained. The nitric acid is caused to act 12 kiloS of calcined sodium sulfate in 50 liters of upon the Suspension for about 1 hour. The SuS Water. pension is then decanted with a Saturated solution The violet or violet-red precipitation product of barium nitrate until the acid and the manga is heated for about 15 minutes at a temperature nese which has been dissolved are removed. A 30 between 750° C. and 800° C., while being exposed Small quantity, for instance A2 per cent. of ba to the air. rium carbonate is precipitated upon the suspend The mixed crystal obtained by way of precipi ed blue pigment and the pigment is then dried tation is destroyed with separation of manganese after having been thoroughly Washed. 35 by gently heating it. Later, there is formed in its We claim: 5 place a body of a pale blue coloration. In order i. The process of producing blue manganate to obtain the pigment in a pure color, that is pigment colors which comprises heating to a tem free from any excess of manganese-oxide or perature of between about 400° C. and about 850 barium manganate, it may be necessary to sub C. an intimate mixture of barium sulfate and a 40 ject the heated product which has been conmi manganese compound in the presence of a basic nuted to small pieces by chilling or grinding, to Substance and of air and purifying the product a purification, for instance with hydrochloric thus obtained with a solution containing Sul acid and a Solution of a bisulfite of an alkali or furous acid. an akaline earth metal. 2. The process of producing blue manganate (2) A solution of 1.3 kilos of barium nitrate 45 pigment colors which comprises heating to a 45 and 100 grams of manganese nitrate containing 6 temperature of between about 400 C. and about molecules of water of crystallization in 10 liters 850 C. an intimate mixture of barium sulfate of Water is precipitated at boiling temperature by and a manganese compound in the presence of a means of a Solution of 1.3 kilos of calcined sodium Sulfate in 5 liters of water. The precipitate ob basic Substance and an agent having an oxidizing tained is further treated as described in Example action, and purifying the product thus obtained 50 1. In this case also there is obtained an azure With a Solution containing sulfurous acid. pigment. 3. AS new products, blue pigment colors con (3) An intimate mixture of 900 grams of sisting of crystals of barium sulfate containing barium sulfate (precipitated and of a pure white in a particular lattice construction barium man color), 250 grams of barium nitrate, 50 grams of ganate, Said pigment colors being identical With 55 potassium permanganate or potassium manga those produced by the proceSS of claim 4 and nate and 150 grams of barium hydroxide is being completely fast to light, insoluble and re slightly moistened and heated for about one hour sistant to atmospheric conditions and having an at about 720° C. in the presence of oxygen. The excellent purity of blue color. sintered cake obtained is then reduced to Small 4. The process of producing blue manganate 60 pieces (for instance by chilling it) and the pig pigment colors which comprises heating to a ment is purified with dilute hydrochloric acid and temperature of between about 400° C. and about a solution of a bisulfite of an alkali or alkaline 850° C. an intimate mixture of barium sulfate and 65 earth metal. There is obtained a dark azure a manganese compound in the presence of a basic pigment. substance and of air and purifying the product 65 (4) An intimate mixture of 900 grams of thus obtained with a Solution containing a strong heavy Spar (finely ground and of a pure white mineral acid and a reducing agent. color), 250 grams of barium nitrate and 62 grams 5. The process of producing blue manganate 0. of barium carbonate is covered with a hot solu pigment colors which comprises heating to a 70 tion of 30 grams of barium permanganate, and temperature of between about 690 C. and about the whole is intimately mixed and then heated 720° C. an intimate mixture of finely ground for about 1 hour at about 690° C. in the presence heavy spar and a manganese compound in the of Oxygen. The further treatment is carried out presence of a basic substance and of air and puri 75. as described in Example 3. fying the product thus obtained with a solution 75 2,156,727 3 containing a strong mineral acid and a reducing by heating an intimate mixture of barium sulfate agent. and a manganese compound under oxidizing 6. The process of producing blue manganate conditions the steps which comprise adding to pigment colors which comprises heating to a the starting mixture a substance yielding a basic temperature of 720° C. an intimate mixture of compound when heated, heating the resulting precipitated pure white barium sulfate, barium mixture to a temperature of between about 400 nitrate, potassium permanganate and barium hy C. and about 850° C., cooling the mixture and droxide in the presence of oxygen and purifying purifying it with a solution containing sulfurous the product thus obtained with dilute hydro acid. 10 chloric acid and bisulfite solution. ERICH KORINTH. O 7. In the process of producing pigment colors GEORG MEDER.