CZ301200B6 - Process for preparing combined inorganic pigment consisting of natural substrate and metal oxides or sulfides - Google Patents

Abstract

The present invention relates to a process for preparing synthetic combined inorganic pigments based on selected natural substrates, clay minerals and feldspars, where the surface of their particles is treated with metal oxides or sulfides, wherein the invented preparation process is based on precipitation of corresponding metal cations or their combinations from corresponding metal salts in liquid phase in the form of their hydroxides of sulfides using urea or thioacetamide in the presence of the given natural substrate. Resulting combined inorganic materials show color effects and in powder or paste form, they can be used as high-grade, thermostable and ecologic pigments.

Description

A process for producing a combined inorganic pigment comprising a natural substrate and metal oxides or sulfides

Technical field

The invention relates to a process for the production of combined inorganic pigments based on selected natural substrates, the surface of which is treated with metal oxides or sulfides. The resulting combined inorganic pigments show a color effect and can be used as high quality, thermostable and ecological pigments.

BACKGROUND OF THE INVENTION

Synthetic inorganic pigments are predominantly powdered substances completely insoluble in water or in common organic solvents. When dispersed in a suitable environment, they become the color component of paints, plastics, paper, building and ceramic materials.

They are characterized by high opacity, coloring ability, weathering resistance, lightfastness and most of them desirable thermostability. Inorganic pigments with an increased sorption capacity or platelet character have anti-corrosive or anti-corrosive pigments. other barrier properties. The quality of inorganic pigments depends on their physicochemical properties, which besides their optical parameters (hiding power, color shade) also influence their processing (impurity content, reactivity, dispersibility in binders and stability of the resulting suspension).

At present, due to their hygienic defects, toxicity, some inorganic pigments are limited in practice and need to be gradually replaced by other, environmentally acceptable materials. Inorganic chromium-based pigments (for example barite yellow, BaCrO ₄ ) are suspected of being highly toxic and are suspected of having carcinogenic effects. Another problem group is inorganic pigments containing cadmium (for example CdS, CdSe) or uranium. Some of these inorganic dyes are replaced by organic dyes, which are, however, thermally and weatheringly unstable, color sensitive to the chemical environment and, compared to inorganic pigments, their price is significantly, even of a higher order. On the other hand, the color range of inorganic pigments is much narrower compared to the color range of organic dyes.

GB 556 496 (1942) describes a process for producing green Cr-based pigments by precipitating Cr cations from its salts (e.g. Cr ₂ (SO ₄ ) ₃ ) to Cr (OH) 3 with an alkali, namely NaOH, KOH, (NEH4) ₂ CO ₃ or Na ₂ CO ₃ , in the presence of extenders such as BaSO ₄ , CaSO ₄ , kaolins and slate powders. However, under the conditions of the production method, a mixture of the present extender (filler) and Cr (OH) ₃ particles is produced, wherein the extender particles are only aggregated into larger units by the amorphous Cr (OH) ₃ component. Furthermore, the document describes a process for producing pigments wherein Cr (OH) ₃ particles are deposited on the surface of an extender, but the process is based on an oxidation reduction process where the preparation of Cr (OH) ₃ from a chromic acid salt (chromates) is required. sodium sulfide in a considerable stoichiometric excess in terms of hydrolysis, since the sulfide acts primarily here as a reducing agent for the reduction of Cr 2 to Cr 3.

SUMMARY OF THE INVENTION

The above-mentioned disadvantages are eliminated by the preparation of combined inorganic pigments, which results from the precipitation of cations of at least one of the metals Co, Bi, Fe, Mn, Ni, Cu, Al, Cr and Cd in the form of their hydroxides by urea or sulfides using thioacetamide in liquid phase. of the present natural substrate, which consists of at least one of the minerals from the group of clay minerals or at least one of the minerals from the group of feldspars or mixtures thereof. The resulting product has the character of a combined inorganic pigment with a color shade characteristic of the combination of ingredients.

-1GB 301200 B6

The hydroxides or sulfides of the above metals are precipitated by metal hydroxide precipitating agents or metal sulfide precipitating agents from the respective metal salts. Urea is used to precipitate hydroxides and thioacetamide is used to precipitate sulfides. The feed, consisting of a natural substrate suspension, metal salts, and a metal hydroxide precipitant or metal sulfide precipitant, is maintained at a temperature of 50 to 100 ° C for at least 15 minutes and a maximum of 10 hours under continuous stirring, and the resulting product is filtered. After filtration, the product is washed and left either in the form of a paste or a suspension or dried to a powder or granulated form in the case of metal sulfides or is ignited in these forms to the corresponding metal oxides. The input substrates or the resulting products can be mechanically treated by milling or ultrasonic disintegration. As minerals from the group of clay minerals, for example, kaolinite, illite, montmori Honit or mixtures thereof can be used.

The combined inorganic pigment produced in this way makes it possible to reduce the cost of the resulting products, since the prices of natural substrates are very favorable compared to pure pigments and in the inorganic pigments where the natural substrate content ranges from 25 to 99% by weight. a more costly pigment component consisting of metal oxides or sulfides.

The composition, shape and particle distribution of the combined inorganic pigments based on clay minerals or feldspars are derived from the nature of the starting natural substrates and determine the basic technological properties of the products, in particular their dispersibility, suspension stability and coating opacity. They are preferably platelet-shaped and, in addition, in terms of their processing and functionality, types with an optimum mean particle size can be selected among them, or they can be easily adjusted by available techniques.

The surface color layer of metal oxides or sulfides on these natural substrates constitutes 1 to 75 wt. and the resulting combined inorganic pigment produces a completely original range of color shades as they combine the optical properties of the light impermeable clay mineral or feldspar and the respective high refractive index metal oxide or sulfide layers depending on their strength and composition.

DETAILED DESCRIPTION OF THE INVENTION

Preparation of blue pigment g kaolinite was stirred in 2 l of distilled water acidified with 5 ml of concentrated H ₂ SO ₄ . After addition of 12 g CoSO ₄ . 7H ₂ O, 13.5 g Al ₂ (SO ₄ ) ₃ . 16 H ₂ O and 15 g urea ((NH ₂ ) ₂ CO) were added to distilled water to a volume of 5 L. The batch was heated and kept at 90 ° C under reflux with stirring for 6 hours, until basic. flux reaction. The precipitated kaolinite layers Co (OH) ₂ and Al (OH) ₃ were washed with distilled water to a conductivity of 25 pS and dried to constant weight in a vacuum oven at 90 ° C. By annealing to 1200 ° C, the hydroxide layer was converted to the respective CoO and Al ₂ O ₃ oxides in a molar ratio of 2/1.

Preparation of blue pigment (II) g of kaolinite was stirred in 2 l of distilled water acidified with 5 ml of concentrated H ₂ SO ₄ . After addition of CoSO ₄ .7H ₂ O, Al ₂ (SO ₄ ) ₃ . 16 H ₂ O, Cr ₂ (SO ₄ ) ₃ and urea ((NH ₂ ) ₂ CO) were added to distil water to a volume of 5 l. The batch was heated and refluxed for 6 hours at 90 ° C. with stirring, until the solution is alkaline. Kaolinite with deposited layers of Co (OH) 2, Al (OH) 3 and Cr (OH) ₃ was washed with distilled water to a conductivity of 250 pS and dried to constant weight in a vacuum oven at 90 ° C. By annealing to 800 ° C, the hydroxide layer was converted to the respective CoO and Al ₂ O ₃ and Cr ₂ O ₃ oxides in a molar ratio of 2/1 / 1.

-2CL JUIZUU DO

Preparation of green pigment g of kaolinite was stirred in 2 l of distilled water acidified with 5 ml of concentrated H ₂ SO ₄ . After adding CoSO ₄ . 7 H ₂ O and Cr ₂ (SO ₄ ) ₃ and urea ((NH ₂ ) ₂ CO) were charged to 5 L with distilled water. The batch was heated and held at reflux for 95 hours at 95 ° C. condenser while stirring, until the solution is alkaline. Kaolinite with excluded CoCOH layers) ₂ and Cr (OH) ₃ was washed with distilled water to a conductivity of 250 pS and dried to constant weight in a vacuum oven at 90 ^at C. The annealing temperature of 800 ° C was converted to the hydroxide layer a layer of the respective oxides CoO, and Cr ₂ O ₃ in a molar ratio of 1/1.

Preparation of red pigment g of kaolinite was stirred in 2 l of distilled water acidified with 5 ml of concentrated H ₂ SO ₄ . After addition of Fe ₂ (SO ₄ ) ₃ and urea ((NH ₂ ) ₂ CO), the batch was made up to 5 L with distilled water. The batch was heated and held at 100 ° C under reflux with constant stirring for 10 hours. into a basic reaction of the solution. Fe (OH) ₃ deposited kaolinite was washed with distilled water to a conductivity of 250 pS and dried to constant weight in a vacuum oven at 90 ° C. By annealing at 800 ^° C, the hydroxide layer was converted to the corresponding Fe ₂ O ₃ oxide layer.

Preparation of yellow pigment g of kaolinite was stirred in 2 l of distilled water. After addition of CdSO ₄ and thioacetamide (CH ₃ C (S) NH ₂ ), the batch was made up to 5 L with distilled water. The batch was heated and kept at 90 ° C under reflux with stirring for 6 hours. The CdS precipitated kaolinite was washed with distilled water to a conductivity of 250 pS and dried to constant weight in a vacuum oven at 90 ° C.

Industrial applicability

In addition to the use of these combined inorganic pigments in conventional technologies, such as the dyeing of plastics or the production of paints, these materials are particularly suitable in terms of their thermostability for use in engobes and glazes. In view of the increasing worldwide consumption of pigments, the affordable inorganic pigment is particularly suitable for expanding dyeing of exposed concretes.

Claims (1)

PATENT CLAIMS 1. A process for the production of a combined inorganic pigment comprised of 25 to 99 wt. % natural substrate and from 1 to 75 wt. oxides or sulphides of at least one of the metals Co or Bi or Fe or Mn or Ni or Cu or Al or Cr or Cd, wherein the natural substrate is composed of at least one mineral from the group of clay minerals or at least one mineral from the feldspar group or mixtures thereof; by adding to an aqueous suspension 45 of the natural substrate add salt of at least one of the metal and urea precipitating metal hydroxides or thioacetamide precipitating metal sulfides, and the batch is maintained at 50-100 ° C for 15 minutes to 10 hours with stirring, the product is filtered and washed and either in the form of a suspension or paste, or dried to a powdered or granulated form, is retained when thioacetamide is used, or calcined at 800 to 1200 ° C when urea is used.