Method of producing emerald chrome pigment

FIELD: chemistry.

SUBSTANCE: method of producing emerald chrome pigment involves calcination of a mixture containing chromic anhydride, boric acid and urea, subsequent washing and drying the pigment. The mixture is calcined at temperature 750-800°C for 0.5-1.0 hours to obtain a melt which is boiled with addition of boric acid in mass ratio of melt to solution equal to 1:6. The mixture has the following weight ratio of ingredients: chromic anhydride - 20 pts. wt, boric acid - 60-80 pts. wt, urea - 3-4 pts. wt.

EFFECT: obtaining green pigment with a tinge of emerald green.

1 ex

 

The invention relates to the manufacture of dyes, in particular the production of emerald green chrome pigment, and can be used in the paint industry. A method of obtaining emerald green chrome pigment by hydrothermal treatment at a temperature of 230 to 250°C. hydrated chromechrome under pressure to 39.5-40.5 ATM in the presence of alkali (Awts of the USSR №467086, SS 1/34, Appl. 09.07.73, publ. 15.04.75.) and the way to obtain emerald green chrome pigment by hydrothermal treatment of chromium hydroxide at a temperature of 280-300°C and the pressure 63-85 ATM in the presence of monochromate sodium in the amount of 50 to 150 wt.% from the chromium source hydroxide chromium (Awts of the USSR №442693, SS 1/34, Appl. 25.06.71, publ. 5.06.76). However, these methods require a sufficiently high pressure in the hydrothermal processing of chrome-containing raw material, which complicates the process of obtaining emerald green chrome pigment.

The closest to this invention to the technical essence and the achieved result, adopted for the prototype, is a method for emerald green chrome pigment comprising calcining the mixture, containing a chromium compound, boric acid or urea, followed by washing and drying of the pigment (patent GB No. 1522051, C01G 37/033 published: 1978-08-23).

This method does not require high pressure, ka the analogues, however, the resulting product does not reach the tones required to be considered emerald.

The task of the invention is the obtaining of chromium trioxide pigment green shade of emerald green. This goal is achieved by the proposed method of obtaining emerald green chrome pigment comprising calcining the mixture containing chromic anhydride, boric acid and urea, followed by washing and drying the pigment, which differ from the known fact that the mixture contains boric acid when following a weight ratio of ingredients:

chromic anhydride20 parts
boric acid60-80 parts
urea3-4 parts

The process of calcination of the mixture is carried out at a temperature of 750-800°C for 0.5-1.0 hour with receiving water. In the operation of the washing of the pigment include boiling water with the addition of a solution of boric acid at a ratio of mass of water and a solution of 1:6.

The possibility of obtaining a technical result, namely the purchase of the product melt the emerald shade is explained in the following. The chemical composition of emerald green chrome pigment is abgedreht chromium oxide Cr 2O3·nH2O (see, for example, Efremenko, Ivison. Chemistry and technology of pigments, ed. 3-e, Corr. and additional, Goskomizdat, 1960, str). The ratio Cr2O3and H2O ranges from 1 to 2 moles of H2About 1 mol Cr2O3. The ratio of elements (Cr, O, and N) hydrate chromium oxide composition Cr2O3·H2O can be written as 2CrOOH. Rhombic (orthorhombic) modification of oxyhydroxide chromium (III)having the composition CrOOH, has emerald green color and decomposes in the temperature range of 480-550°C with the formation of CrO2(chromium dioxide, which has a black color) and Cr2O3(see, for example, Inorganic compounds of chromium: a Handbook/ Ed.: Rowans V., Kireeva M.V., Berg. and others - L.: Chemistry, 1981. p.13). During annealing in the temperature range of 480-550°C samples emerald green chrome pigment, obtained from bichromate potassium and sodium in a mixture with boric acid and chromium trioxide in a mixture with boric acid and urea, the resulting black powder. Therefore, there is reason to believe that emerald green chrome pigment is an orthorhombic modification of oxyhydroxide chromium (III).

In the process of roasting boric acid loses a significant portion of the water of hydration and goes at 140°C in pyrobombus acid (see, for example, Efremenko, the. Century Riskin. Chemistry and technology of pigments, ed. 3-e, Corr. and additional, Goskomizdat, 1960, str):

4H3IN3→H2O+H2B4O7

When heated to 150°C and above urea is gradually becoming NH4NCO, NH3, CO2biuret, cyanuric acid (see, for example, concise encyclopedia of chemical. Ed. Nr. of Knunyants I.L. (resp. amended) and the other Is 3. - Moscow: "Soviet encyclopedia", 1964. the STB. 328). Cyanuric acid in turn when heated depolymerized with the formation of cyanic acid, which in water in the presence of mineral acids rapidly hydrolyzed to the NH3and CO2(see, for example. Concise encyclopedia of chemical. Ed. Nr. of Knunyants I.L. (resp. amended) and the other Is 3. - Moscow: "Soviet encyclopedia", 1964. the STB. 831). Therefore, the total reaction of the decomposition of urea can be represented by the equation:

So, boric acid serves as a source of water necessary for obtaining a group HE. In the process of roasting chromic anhydride interacts with the group HE:

CrO3+HECrOOH+O2

Thus, boric acid necessary for the formation of chromium trioxide it is emerald green chrome pigment.

The essence of the method consists in the following.

The charge, consisting of chromic anhydride and boric acid in the ratio

H3 BO3:CrO3=3÷4:1

and urea in the amount of 15-20% by weight of chromium trioxide, calcined at a temperature of 750-800°C for 0.5-1 hour. The resulting water is decomposed by boiling for 1 hour, cooled to 20°With a solution of boric acid after evaporation (if not water) at a ratio of m(of water):m(solution) = 1:6. Sediment emerald green chrome pigment is filtered and then subjected to two consecutive repulation at a ratio of T:W=1: 5, the temperature of 95-100°C. with stirring at this temperature for 20 minutes. After each repulpable sediment emerald green chrome pigment is filtered and optionally washed with hot water, the volume of which is equal to the volume of water collected on repulpable. After that, the product is dried at a temperature of 75-80°C. the Dried emerald green chrome pigment has the following characteristics:

the content of Cr2O3- 73-76%, the content of CrO3water-soluble is less than 0,0001%, the content of water soluble salts of 0.1 to 0.6%, pH of water extract - 6-7, opacity - 30-35 g/m2the oil absorption-50-58 g oil/100 g pigment, the color tone 495-505 nm.

The filtrate after the first treatment of the melt is cooled to 20°C, as a consequence, the bulk of boric acid crystallizes, and the solution with its small content of the mix with the rest of the filtrate, evaporated, again cooled to 20°C is separated vykristallizovalsya boric acid. The resulting solution is used for the decomposition of water allocated boric acid is dried at a temperature of 80-85°C and used for the preparation of new portions of the charge.

Our own research has shown the following. When the ratio of N3IN3:CrO3less than 3 pigment has a dark green color. When the ratio of N3IN3:CrO3more than 4 levels are rising and spreading capacity and oil absorption, and increases the content of water-soluble salts in the product.

If the charge content of urea is less than 15% by weight chromic anhydride, the product has an increased measure of opacity and dark green color. If the charge urea concentration greater than 20% by weight chromic anhydride, the product has a gray-green color.

When the temperature of annealing below 750°C, the reaction recovery of chromium does not proceed to the end, and the product contains the intermediate black. At temperatures above 800°C To form harmful oxide of chromium.

Example

A mixture consisting of 20 g of chromic anhydride, 60 g of boric acid and 4 g of urea, calcined at 800°C for 30 minutes. The resulting track in the number 45,39 g is decomposed by boiling for 1 hour with 272 g cooled to 20°With a solution of boric acid after evaporation. Sediment emerald green chrome pigment is filtered off on a Raven is E. Buechner. The wet sediment emerald green chrome pigment in an amount 69,28 g moisture content of 60% repulper 98 g of distilled water at a temperature of 95-100°C. with stirring at this temperature for 20 minutes. After this precipitate emerald green chrome pigment is filtered on a Buechner funnel and additionally washed in the layer over 98 g of hot distilled water. Next, the wet sediment emerald green chrome pigment in an amount 49,88 g moisture content of 60% repulper 70 g of distilled water at a temperature of 95-100°C. with stirring at this temperature for 20 minutes, after which the precipitate is again filtered on a Buechner funnel and additionally washed in the layer over 70 g of hot distilled water. After that, the product is dried at a temperature of 75-80°C. the Dried emerald green chrome pigment has the following characteristics: the content of Cr2O3- 75,44%, the content of CrO3water-soluble is less than 0,0001%, the content of water soluble salts of 0.25%, pH of water extract of 6.66, opacity by 34.2 g/m2the oil absorption - of 55.5 g oil/100 g pigment, the color tone is 496 nm.

The filtrate after the first treatment of the melt is cooled to 20°C and separated vykristallizovalsya boric acid, and the solution is mixed with the rest of the filtrate then evaporated to the amount necessary to decompose water again Oh adut to 20°C and separated vykristallizovalsya boric acid. Selected boric acid is dried at a temperature of 80-85°C. After drying receive 44,37 g of boric acid.

Thus, using the proposed method from a mixture containing chromic anhydride, boric acid and urea in the claimed ratio, by calcination, followed by washing get the pigment emerald tones.

The method of obtaining emerald green chrome pigment by calcination of a mixture containing a chromium compound, boric acid and urea, followed by washing and drying the pigment, characterized in that compounds of chromium using chromic anhydride, the mixture contains boric acid, and urea, calcining the mixture is carried out at a temperature of 750-800°C for 0.5 to 1.0 hours of obtaining water, which is boiled with boric acid at a mass ratio of water and a solution of 1:6, and the mixture has the following ratio of ingredients, parts:

chromic anhydride20
boric acid60-80
urea3-4



 

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