MXPA99004647A - Use of a beta rare earth sulphide as colouring pigment and method for preparing same - Google Patents

Abstract

The invention concerns the use of a beta rare earth sulphide as colouring pigment and its method of preparation. A beta rare earth sulphide is used, the rare earth being lanthanum, cerium, praseodymium, samarium or neodymium. The sulphide consists of whole crystallites, said crystallites forming medium-sized aggregates of not more than 1.5&mgr;m. The method of preparation of this rare earth sulphide is characterised in that a rare earth compound is reacted with at least one sulphidising gas selected among hydrogen sulphide or carbon sulphide. The pigment can be part of compositions of the following types:plastic, paint, surface coating, rubber, ceramic, glazing, paper, ink, cosmetic products, dyes, leather, laminated coating or other types of compositions with a base of at least one mineral binder or obtained therefrom.

Description

PROCEDURE FOR THE PREPARATION OF A METAL SULFIDE OF RARE EARTHS. BETA SHAPE THIS METAL OF RARE EARTH IS THE LANTANO. CERIUM. PRASEODYMIUM. SAMARIO OR NEODIMIUM The present invention relates to the use, as color pigments, of a rare earth metal sulfide, of beta form, and to its preparation process. Colored inorganic pigments have already been widely used in many industries, particularly in paints, plastics and ceramics. In such applications, the properties, which are, among others, thermal and / or chemical stability, dispersibility (ability of the product to properly disperse in a given medium), compatibility with the medium to be colored, intrinsic color, the ability to color and opacity, all constitute particularly important criteria that will be taken into consideration in the selection of a suitable pigment. Most inorganic pigments, which are suitable for applications, such as the above, and which are currently used at present on an industrial scale, however, present a problem. This is because they make use, generally, of metals (cadmium, lead, chromium and cobalt, in particular) whose use has become increasingly regulated severely, or even prohibited, by the legislation of many countries, due to its supposedly very high toxicity. It is thus seen that there is a great need for novel inorganic substitution pigments. The object of the present invention is to supply such pigments, in the range of reds, in particular, and, more especially in the Bordeaux red range. According to a first embodiment, the present invention provides a process for the preparation of a rare earth metal sulfide, beta, this rare earth metal is lanthanum, cerium, praseodymium, samarium or neodymium, in which, a carbonate or a hydroxycarbonate of the rare earth metal is reacted with the hydrogen sulfide. According to a second embodiment, the process is characterized in that a rare earth metal compound is reacted with a sulfurized gas mixture, based on hydrogen sulfide and a carbon disulfide. The present invention is applied to the preparation of a lanthanum, cerium, praseodymium, samarium or neodymium sulfide, as well as mixed sulfides, ie sulphides of two or more rare earth metals of the group given above. Consequently, anything described subsequently for a single sulfur also applies to mixed sulfides. In the case of the first embodiment, the process is characterized in that a carbonate, or a hydroxycarbonate, of the rare earth metal is reacted with the hydrogen sulfide. According to a second embodiment of the invention, a mixture of two gases is used. It has been noted that it is possible to modify the color of the sulfur, varying the oxygen content of this sulfide. This oxygen content can be modified by varying the content of the carbon disulfide in the gas mixture. Thus, all the other parameters of the process are the same in another way, a high content of carbon disulfide promotes the production of sulfides with low oxygen content, ie products with lighter colors of clear Bordeaux type, for example, in a higher content of hydrogen sulphide makes it possible to obtain products with higher oxygen concentrations and thus with darker colors. The sulfur gas or sulfur gas mixture can be used with an inert gas, such as argon or nitrogen. The rare earth metal compound, used for the reaction, in this second embodiment, is preferably a carbonate or a hydroxycarbonate. Nitrates can also be mentioned. An oxide of a rare earth metal can also be used. The sulfiding reaction is generally carried out at a temperature of 600 to 1000 ° C, preferably at 600 to 800 ° C, in particular at 800 ° C or in the region of this temperature. The duration of the reaction corresponds to the time necessary to obtain the desired sulfide, typically from one to four hours.

At the conclusion of the heating, the formed sulfide can be recovered. If it is desired to obtain a product with a finer particle size, the latter can be deagglomerated. Deagglomeration under moderate conditions, for example wet milling or air jet milling, under moderate conditions, makes it possible to obtain a sulfide exhibiting, in particular, an average aggregate size of not more than 1.5 μm. The rare earth metal sulfide, obtained by the processes of the invention, is one that exhibits the beta crystallographic form. The beta form, as used herein, is understood to mean a compound of the formula Ce? 0S14OxS? _x, where x is between 0 and 1, 0 is excluded, crystallization in the quadratic system, group of space I 4? / acd. A characteristic of the sulfide obtained by the processes of the invention is that it is composed of complete crystallites. These crystallites form aggregates and these aggregates constitute the powder, which is produced by the process. By "full crystallite" is meant a crystallite which has not been broken or chipped. The crystallites may, in fact, be chipped or broken during grinding. The photographs of the scanning electron microscopy of the product of the invention make it possible to show that the crystallites that constitute it, generally have not been chipped. The aggregates that constitute the sulfide usually exhibit an average size no greater than 1.5 μm. This average size is generally not greater than 1 μm and more particularly not greater than 0.8 μm. In the description, the size and particle size distribution characteristics were measured by the laser diffraction technique, with the use of a Cilas HR 850 particle size meter (volume distribution). It should be noted that the sulfide obtained by the processes of the invention may be deagglomerated. Thus, it may not be provided in the form of agglomerates, with average sizes within the values given above. In this case, aggregates can be agglomerated and / or slightly sintered and have a larger size of these values. Simple deagglomeration under moderate conditions makes it possible to obtain aggregates with an average size no greater than 1.5 μm or within the ranges given above.

According to a specific embodiment, the sulfide is provided in the form of a pure phase, the simple beta phase, as defined above. The sulfur, obtained by the processes of the invention, can also exhibit a variable content of oxygen. This content, expressed as the weight of oxygen with respect to the weight of total sulfur, should not be greater than 0.8%. In the case where the rare earth metal is cerium, the sulfur will generally exhibit a Bordeaux red color. According to a specific embodiment, the cerium sulfide exhibits an L * coordinate of chromaticity less than 40 and a b * / a * ratio of less than 0.6. The chromaticity coordinates L *, a * and b *, are given here (and throughout the description) in the 1976 CIÉ system (L *, a * and b *), as defined by the Copimission Internationale d 'Eclairage (International Commission) of Lighting) and listed in Rcueil des Normes Fran? alses (Compendium of French Standards) (AFNOR), colorimetric color No. X08-12, No. X08-14 (1983). They are determined by means of a colorimeter sold by Pacific Scientific. The nature of the illuminant is D65. The observation surface is a pellet with a surface area of 12.5 cm2. The conditions of observation correspond to the vision under an opening angle of 10 °. In the given measurements, the specular component is excluded. Various alternative forms of the invention will now be described. According to a first alternative form, the sulfide, as described above, additionally comprises a layer based on at least one transparent oxide, this layer being deposited on its surface or its periphery. Reference can also be made, with respect to a product of this type, to French Patent Application FR-A-2, 703, 999. The peripheral layer covering the sulfide may not be perfectly continuous or homogeneous. Preferably, however, the sulfides, according to this embodiment, comprise a transparent oxide coating layer, which is uniform and of controlled thickness and which does not detrimentally affect the original color of the sulfide, before coating. By "transparent oxide" it is meant an oxide which, once deposited on the sulfur, in the form of a more or less fine film, only absorbs light rays in the visible region in a very small extent or not at all, and that it does not hide, or only conceals very slightly, the original intrinsic color of sulfur. In addition, it should be noted that the term "oxide", as used herein, should be understood to cover oxides of the hydrated type. These oxides, or hydrated oxides, can also be amorphous and / or crystalline. Mention may be made, more particularly, as examples of such oxides, to silicon oxide (silica), aluminum oxide (alumina), zirconium oxide (zirconia), titanium oxide, zirconium silicate, ZrSi04 (zircon) and to oxides of rare earth metals. According to a preferred alternative form, the coating layer is based on silica. Even more advantageously, this layer consists only, essentially and preferably, of silica. According to another alternative form, the sulfide may additionally comprise fluorine atoms. In this case, reference can also be made, with respect to the arrangement of the fluorine atoms, to French Patent Application FR-A-2, 706, 476.

Fluorinated sulfide may exhibit at least one of the following characteristics: "Fluorine atoms are distributed along a gradient of concentration that decreases from the surface to the sulfide core;" Fluorine atoms are distributed mainly in the outer periphery of sulfur. By external periphery is meant means, in this case, a thickness of material, measured from the surface of the particle, of the order of a few hundred Angstroms. In addition, "mainly" is understood to mean that more than 50% of the fluorine atoms present in the sulfide are in this outer periphery; "the percentage by weight of the fluorine atoms present in the sulfide will not exceed 10% and preferably 5%;" the fluorine atoms are present in the form of fluorinated or sulfur-fluorinated compounds, in particular in the form of fluorides of rare earth metals or sulfur fluorides (thiofluorides) of rare earth metals.

Of course, the present invention considers the combination of the modalities described above. Thus, it is possible to develop a sulfide comprising an oxide layer and, furthermore, comprise fluorine atoms. The methods for the preparation of the sulfides, according to these alternative forms, will now be described. For the first alternative form, described above, that is to say for the sulfide exhibiting a layer of a transparent oxide, the preparation process may consist in bringing together the sulfide, as obtained after the sulfuration reaction,. and a precursor of the transparent oxide that forms the layer, and in precipitation this oxide. The processes for precipitating the oxides and the precursors to be used are described, in particular, in patent FR-A-2, 703, 999. In the case of silica, mention may be made of the preparation of the silica by hydrolysis of an alkyl silicate, a reaction mixture being formed by mixing water, alcohol, sulfide, which is then suspended, and, optionally, a base, followed by the introduction of the alkyl silicate or, alternatively, a preparation by the reaction of the sulfide, of a silicate, of the alkali metal silicate type, and of an acid. In the case of a layer based on alumina, the sulfide, an aluminate and an acid can be reacted, whereby the alumina is precipitated. This precipitation can also be obtained by taking together and reacting the sulfur, an aluminum salt and a base. Finally, alumina can be formed by the hydrolysis of an aluminum alkoxide. With respect to titanium oxide, it can be precipitated by introducing, within an aqueous suspension of the sulfide, according to the invention, a titanium salt, such as TiCl 4, TiOCl 2 or TiOS 04, on the one hand, and a base, other. It is also possible to carry out the preparation, for example, by hydrolysis of an alkyl titanate or precipitation of a titanium sol. Finally, in the case of a layer based on zirconium oxide, it is possible to carry out the preparation by the co-hydrolysis or co-precipitation of a sulfide suspension, in the presence of an organometallic zirconium compound, for example a zirconium alkoxide, such as zirconium isopropoxide.

The process for the preparation of the sulfide, according to the second alternative form, a sulfide, comprising fluorine atoms, employs a fluorination. This fluorination can be carried out according to any technique known per se, which carries together the sulfide, as obtained after the sulphuration reaction, and a fluorinating agent. In particular, the fluorinating agent may be liquid, solid or gaseous. Preferably, the fluorination is carried out under treatment conditions where the fluorinating agent is liquid or gaseous. Mention may be made more particularly, as examples of fluorinating agents which are suitable for carrying out the treatment, according to the invention, to fluorine F2, alkali metal fluorides, ammonium fluoride, rare gas fluorides, nitrogen fluoride , NF3, boron fluoride, BF3, tetrafluoromethane or hydrofluoric acid, HF. In the case of a treatment under a fluorination atmosphere, the fluorinating agent can be used in pure form or diluted in a neutral gas, for example nitrogen.

The reaction conditions are preferably selected so that this treatment only carries out fluorination on the surface of the sulfide (moderate conditions). In this aspect, the performance of the fluorination to the sulfide core does not produce results that are substantially improved with respect to an essentially superficial fluorination. In practice, it is possible to monitor experimentally and control the degree of progression of the fluorination reaction, for example, by measuring the change in the increase in the mass of the materials (increase in mass made by the gradual introduction of fluorine). The fluorinating agent may be more particularly ammonium fluoride. As indicated above, it is possible to consider the preparation of a sulfide that combines the constituent characteristics of the various modalities: the oxide layer and the presence of fluorine atoms. In order to obtain such combinations, the preparation processes just described are combined. Thus, the treatment of the fluorination can be carried out in a first stage and then, in a second stage, the sulfur, thus treated, and a precursor of the transparent oxide are put in contact, and this transparent oxide is precipitated on the sulfur. Another process can also be considered. In this case, in the first stage, the sulfide and the precursor of the transparent oxide are brought into contact and then this transparent oxide is precipitated on the sulfide, and, finally, in a further step, the fluorination treatment is carried out. The sulfide of the invention, such as that obtained after the reaction with the gas or sulfurization mixture, can be treated in order to deposit on it a zinc precursor. This deposit can be made by the reaction of a zinc precursor with aqueous ammonia or ammonium ammonia. Reference may be made for this treatment to French patent application FR-A-2741629, the teachings of which are incorporated herein. Some essential elements of this treatment are remembered below. The zinc precursor can be a zinc oxide or hydroxide, which is used in suspension. This precursor can also be a zinc salt, preferably a soluble salt. That may be a salt of an inorganic acid, such as a chloride, or, alternatively, a salt of an organic acid, such as an acetate. For deposition of the zinc compound, the sulfide, the zinc precursor, the aqueous ammonia and / or the ammonium salt, are placed in contact in the presence of an alcohol. The alcohol used is generally selected from aliphatic alcohols, such as, for example, butanol or ethanol. The alcohol can, in particular, be introduced with the zinc precursor in the form of an alcoholic solution of zinc. According to another advantageous variant, the sulfur, the zinc precursor, the aqueous ammonia and / or the ammonium salt are placed in contact in the presence of a dispersing agent. The object of this dispersion agent is to prevent the agglomeration of the particles forming the support, during its placement in the suspension, for the treatments described above. It also makes it possible to work in more concentrated media. This promotes the formation of a homogeneous layer of transparent oxide over all the particles.

This dispersion agent can be selected from the group of dispersing agents by a steric effect, and, in particular, water-soluble or non-ionic, water-soluble polymers. Dispersing agents which may be mentioned are cellulose and its derivatives, polyacrylamides, polyethylene oxides, polyethylene glycols, polyoxyethylene polyoxypropylene glycols, polyacrylates, polyoxyethylenated alkylphenols, polyoxyethylenated long-chain alcohols, polyvinyl alcohols, alkanolamides, dispersing agents of the type of polyvinylpyrrolidone and compounds based on xanthan gum. The sulfur described, has good coloration capacity and cover capacity and, for this reason, it is suitable for the coloring of numerous materials, such as plastics, paints and others. More specifically, it can be used in the coloring of polymers for plastics, which may be of the thermoplastic or thermoset type. Mention may be made as thermoplastic resins capable of being colored, according to the invention, only in the form of illustration, to poly (vinyl chloride), poly (vinyl alcohol) polystyrene, styrene-butadiene, styrene-acrylonitrile and acrylonitrile copolymers -butadiene-styrene (ABS), acrylic polymers, in particular poly (methyl methacrylate), polyolefins, such as polyethylene, polypropylene, polybutene or polymethylpentene, cellulose derivatives, such as cellulose acetate, cellulose acetobutyrate or ethylcellulose , or polyamides, which include the 6.6 polamide. With respect to the thermosetting resins for which the sulfide is also suitable, mention may be made, for example, of phenoplast, aminoplast, in particular urea-formaldehyde or melamine-formaldehyde copolymers, epoxy resins and thermoset polyesters. The sulfide can also be used in special polymers, such as fluorinated polymers, in particular polytetrafluoroethylene (P.T.F.E.), polycarbonates, silicone elastomers or polyimides. In this specific application for the coloring of plastics, sulfur can be used directly in the powder form. It is also possible, preferably, to use it in a previously dispersed form, for example as a pre-mix with a portion of the resin, or in the form of a concentrated paste or a liquid, which makes it possible to introduce it at any stage in the manufacture of the resin. Thus, the products, according to the invention, can be incorporated in plastics, such as those mentioned above, in a proportion by weight that generally varies from 0.01 to 5% (relative to the final product) or from 20 to 70%, in the case of a concentrate. The products of the invention can also be used in the field of paints and varnishes and, more particularly, in the following resins: alkyd resins, the most common of which is glyceryl phthalate resin; resins modified with a long or short oil; acrylic resins derived from esters of acrylic acid (methyl or ethyl) and methacrylic acid, optionally copolymerized with ethyl, 2-ethylhexyl or butyl acrylate; vinyl resins, such as poly (vinyl acetate), poly (vinyl chloride), poly (vinyl butyral), poly (vinyl formal), and copolymers of vinyl chloride and vinyl acetate or vinylidene chloride; phenolic or aminoplast resins, generally modified; polyester resins; polyurethane resins; epoxy resins; or silicone resins.

The products are generally used in the proportion of 5 to 30% by weight of the paint and from 0.1 to 5% by weight of the varnish. In addition, the products, according to the invention, are also suitable for applications in the rubber industry, in particular in floor finishes, in the paper industry and in printing inks, in the field of cosmetics, and many others uses, such as in dyes, in leathers, for finishes of the latter, and laminate coatings for kitchens and other work surfaces, ceramics and glass. The products of the invention can also be used in the coloration of materials based on or obtained from, at least one inorganic binder. This inorganic binder can be selected from, typically, hydraulic binders, air-cured binders, plasters, and anhydrous or partially hydrated calcium sulfate binders. By "hydraulic binders" is meant substances having the property of setting and hardening, after the addition of water, with the formation of water-insoluble hydrates. The products of the invention apply very particularly to the coloration of cements and, of course, of the concretes made of these cements, by the addition to the latter of water, sand and / or gravel. In the context of the present invention, the cement may be, for example, of aluminous type, ie any cement containing a high proportion of alumina as such or of aluminate, or both. Mention may be made, as examples, of cements based on calcium aluminate, in particular those of the Dry type. The cement may also be of silicate type and, more particularly, based on calcium silicate. Examples of which can be given by Portland cements and cements of this type, Portland cements that set quickly or very quickly, white cements, those that are resistant to sulfates and those that comprise slag from blast furnaces and / or fly ash and / or meta-kaolin. Mention may also be made of cements based on calcium sulfate hemihydrate and magnesia cements, known as Sorel cements.

The products of the invention can also be used for the coloring of air-cured binders, that is, binders that harden in open air by the action of C02 of the calcium or magnesium oxide or hydroxide type. Finally, the products of the invention can be used for coloring plasters and binders of the anhydrous or partially hydrated calcium sulphate type (CaS04 and CaS04-% H20) The invention thus provides colored compositions of a material, in particular of plastics, paints, varnishes, rubbers, ceramics, lusters, papers, inks, cosmetic products, dyes, leathers or laminate coatings of the type based on, or obtained from, at least one inorganic binder, which comprises, as the coloring pigment, a sulphide , as defined above, or obtained by processes of the type described above The following Examples further illustrate the present invention In these Examples, the particle size was determined according to the aforementioned technique. a dispersion of the product in an aqueous solution containing 0.05% by weight of sodium hexametaphosphate, which has been subjected to anti- emanating the treatment with an ultrasonic probe (probe with a tip diameter of 13 mm, 20 kHz, 120 W) for 3 minutes.

EXAMPLE 1 Synthesis of ß-Ce10S? 400.i7So.83 (light red sulfide) Procedure: 16 g of cerium hydroxycarbonate (Ce (OH) C03), containing 70.7% of Ce02, was calcined under a flow of H2 (flow rate = 10 1 / h) and CS2 (flow rate) 1. 4 1 / h), according to the following temperature profile: temperature rise at 800 ° C at a rate of 8 ° C / minute, then a stationary phase of 1 hour at this temperature. Results: 13 g of the product, with the formula given above (a single present phase, according to the X-ray plates) were obtained, with an oxygen content of 0.15% by mass (determined under the unit cell parameter) .

The particle size obtained is 0.74 μm (s / m = 0.49). The colors, determined in the CIR Lab system, are: L * / a * / b * = 38.9 / 36.3 / 16.7 The absorptions at 400 and 700 nm are as follows: R400 / R700 = 5.06 / 65.63. 10 g of the pigment, thus synthesized, were mixed in a rotating container with 2 kg of a reference polypropylene Eltex® PHV 001. The mixture was then injected at 220 ° C using a Kapsa injection molding machine, model Protoject 10/10 , with a cycle of 41 s. The mold was maintained at a temperature of 35 ° C. A double thickness parallelepiped (2 and 4 mm) was thus obtained. It was observed that the pigment disperses well. The chromaticity coordinates and the absorptions, measured in the thick part of the plate, are as follows: L * / a * / b * = 33.5 / 39.6 / 20.6 R400 / R700 = 2.4 / 60.2.

EXAMPLE 2 Synthesis of ß-Ce10S? 400.8 o.2 (dark red sulfide) Procedure 14 g of cerium hydroxycarbonate (Ce (OH) C03), containing 70.7% of Ce02, were calcined under a flow of H2S, ( flow 0 10 1 / h), according to the following temperature profile: temperature rise to 800 ° C in the 8 ° C / minute regime, then a stationary phase of 3 hours at this temperature. Results: 11.2 g of the product, with the formula given above (a single phase present, according to the X-ray plates), was obtained, with an oxygen content of 0.69% by mass (determined by virtue of the unitary cell parameter ). The particle size obtained is 0.76 μm (s / m = 0.44). The colors and the absorptions, determined by the CIÉ Lab system, are: L * / a * / b * = 36.1 / 27.4 / 12 R400 / R700 = 5.05 / 64.35.

After injection into polypropylene, under the conditions of Example 1, colors and absorptions became: L * / a * / b * = 29.7 / 31.4 / 16.4 R400 / R700 = 2.05 / 59.5 The following examples are They refer to some products, which, after their preparation, were taken to a complementary treatment to obtain a transparent oxide layer, to deposit zinc or fluorine. The treatment to deposit the oxide layer and for the introduction of the zinc is as follows: The polyvinylpyrrolidone (PVP) was dissolved in ethanol. The fluorinated cerium sulfide was added to this solution, then the aqueous ammonia solution and finally the zinc precursor. The ethyl silicate was introduced continuously in two hours. After the introduction of the ethyl silicate, the mixture matured for two hours. The particles thus obtained were washed with ethanol by filtration and then dried at 50 ° C for twelve hours.

EXAMPLE 3 This example refers to the product of Example 2. The reagents were used in the following proportions g of product / kg of suspension ß ~ Ce? oS? Oo .8So .2 200 95% Ethanol 643 Aqueous ammonia (32%) 100 Zinc acetate 20 Ethyl silicate 32 PVP K10 (Aldrich Company) 5 Molecular weight = 10000 The cerium sulfate used was fluorinated in advance as follows: 10 g of the product were introduced in 100 ml of an ammonium fluoride solution (5% by mass, with respect to the ß ~ Ce? 0S? 400.8So.2) • The pH of the mixture was adjusted to 8 by the addition of an aqueous solution of ammonia and the medium was stirred for one hour.The product was then filtered off and then dried in a desiccator under vacuum.

The product, thus obtained, was treated under the operating conditions given above, using the aqueous ammonia. The product obtained has the following chromatic coordinates, after injection into polypropylene: L * / a * / b * = 36/20/10 EXAMPLE 4 This example refers to the product of Example 1. The reagents were used in the following proportions: g of product / kg of suspension ß ~ CeioSiéOo .17S0.83 200 Ethanol 95% 643 Aqueous ammonia (32%) 100 Acetate of zinc 32 Ethyl silicate 32 PVP K10 (Aldrich Company) Molecular weight = 10000 Cerium sulphide used it was fluorinated in advance as follows: 10 g of the product were introduced into 100 ml of an ammonium fluoride solution (5% by mass), with respect to ß-Ce? 0S? 00.i7So.83) • The pH of the mixture was adjusted to 8 by the addition of an aqueous solution of ammonia and the medium was stirred for one hour. The product was then separated by filtration and then dried in a desiccator under vacuum. The product, thus obtained, was treated under the operating conditions given above, using the aqueous ammonia. The product obtained has the following chromatic coordinates, after injection into polypropylene: L * / a * / b * = 38/33/15.

Claims (10)

1. Process for the preparation of a rare earth metal sulfide, of beta form, this rare earth metal is lanthanum, cerium, praseodymium, samarium or neodymium, characterized in that a carbonate or a hydroxycarbonate of a rare earth metal is reacted with hydrogen sulfide.

2. Process for the preparation of a rare earth metal sulfide, beta, this rare earth metal is lanthanum, cerium, praseodymium, samarium or neodymium, characterized in that a rare earth metal compound is reacted with a gaseous mixture hydrogen sulphide sulfurizer and carbon disulfide.

3. Process according to claim 2, characterized in that the rare earth metal compound is a carbonate or a hydroxycarbonate.

4. Process, according to claim 2 or 3, characterized in that the content of the oxygen of the sulfide, prepared, is modified by varying the content of the carbon disulfide in the gas mixture.

5. Process, according to any of the preceding claims, characterized in that the reaction is carried out at a temperature of 600 to 800 ° C.

6. Process, according to any of the preceding claims, characterized in that the sulfide obtained, after the reaction with the sulfurizing gas or the mixture, is contacted with a precursor of a transparent oxide, so that this oxide precipitates on the sulfide .

7. Process, according to any of claims 1 to 6, characterized in that the sulfide obtained, after the reaction with the sulfurizing gas or the mixture, is brought into contact with a fluorinating agent.

8. Process, according to any of claims 1 to 7, characterized in that a zinc compound is deposited on the sulfide obtained after the reaction with the sulfurizing gas or the mixture, by the reaction of the zinc precursor with the aqueous ammonia or a ammonium salt.

9. The use of the coloring pigment of a sulfide, obtained by the process according to any of the preceding claims.

10. Compositions of colored matter, such as plastics, paints, varnishes, rubbers, ceramics, polishes, papers, inks, cosmetics, dyes, leathers or laminate coatings of the type based on or obtained from at least one inorganic binder, characterized in that they are prepared using a sulfide obtained by the process according to claims 1 to 8.