FR2755971A1 - USE AS A COLORING PIGMENT OF A RARE EARTH SULFIDE OF BETA FORM AND PROCESS FOR THE PREPARATION THEREOF - 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 mu 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

USE AS A COLORING PIGMENT OF A RARE EARTH SULFIDE FROM
BETA FORM AND ITS PREPARATION METHOD
RHONE-POULENC CHEMISTRY
The present invention relates to the use as coloring pigment of a rare earth sulfide of beta form and to its preparation process.

 Mineral coloring pigments are already widely used in many industries, particularly in paints, plastics and ceramics. In such applications, the properties of, among others, thermal and / or chemical stability, dispersibility (ability of the product to disperse correctly in a given medium), compatibility with the medium to be colored, intrinsic color, coloring power and opacifying power are all particularly important criteria to take into consideration when choosing a suitable pigment.

 Most of the mineral pigments which are suitable for applications such as above and which are actually used to date on an industrial scale pose a problem, however. In fact, they generally use metals (cadmium, lead, chromium, cobalt in particular), the use of which is becoming more and more severely regulated, or even prohibited, by the laws of many countries, given their reputed toxicity. very high.

 We therefore see that there is a significant need for new substitute mineral pigments.

 The object of the present invention is to provide such pigments, in the range of red in particular and, more particularly, in the range of burgundy red.

 For this purpose, use is made, according to the invention, of a rare earth sulfide of beta form, the rare earth being lanthanum, cerium, praseodymium, samarium or neodymium.

 The invention also relates to a process for the preparation of such a rare earth sulfide which is characterized in that a rare earth compound is reacted with at least one sulfurizing gas chosen from hydrogen sulfide or hydrogen sulfide. carbon.

 Other characteristics, details and advantages of the invention will appear even more completely on reading the description which follows, as well as concrete but not limited examples intended to illustrate it.

 The sulfide which can be used according to the invention is a lanthanum, cerium, praseodymium, samarium or neodymium sulfide. The present invention also applies to mixed sulfides, that is to say the sulfides of two or more rare earths from the group given above. The invention applies more particularly to cerium sulfide.

The rare earth sulphide which can be used according to the invention is a sulphide which has the beta crystallographic form. By beta form is meant here and for the whole of the description, a compound of formula Ce10S14OxS1 x in which x is between 0 and 1, 0 being excluded, crystallizing in the quadratic system, space group I 41 / ad
A characteristic of the sulfide which can be used according to the invention resides in the fact that it consists of whole crystallites. These crystallites form aggregates and these aggregates constitute the powder in the form of which the sulphide occurs. By whole crystallite is meant a crystallite which has not been broken or broken. Crystallites can in fact be broken or broken during grinding. The photos in scanning electron microscopy of the product of the invention make it possible to show that the crystallites which constitute it have not been broken.

 The aggregates constituting the sulfide have an average size of at most 1.5pu.

This average size can be at most 1 μm and more particularly at most 0.8 μm.

For the whole of the description, the size and granulometry characteristics are measured by the laser diffraction technique using a granulometer of the type
CILAS HR 850 (volume distribution).

 It should also be noted that the sulfide which can be used according to the invention is disaggregatable. It may thus not be presented directly in the form of medium-sized aggregates in the values given above. In this case, the aggregates can be agglomerated and / or slightly sintered and have a size greater than these values. In this case, a simple disagglomeration under mild conditions makes it possible to obtain aggregates of average size of at most 1.5clam or in the ranges given previously.

 According to a particular embodiment, the sulfide is in the form of a pure phase, it is the only beta phase as defined above.

 The sulphide which can be used according to the invention can also have a variable oxygen content. This content, expressed by weight of oxygen relative to the weight of all of the sulfide, can be at most 0.8%.

 In the case where the rare earth is cerium, the sulphide presents a burgundy red color. According to a particular embodiment, the cerium sulphide has a chromatic coordinate L * of less than 40 and a ratio b * / a * of less than 0.6. The chromaticity coordinates L *, a * and b * are given here and for the rest of the description in the CIE 1976 system (L *, a * and b *) as defined by the International Lighting Commission and listed in the Collection of French Standards (AFNOR), colorimetric n "X08-12, n" X08-14 (1983). They are determined with regard to the measurements made on the products and the plastics using a colorimeter marketed by the Pacific Scientific Company. The nature of the illuminant is D65. The observation surface is a circular patch with a surface area of 12.5 cm2. The observation conditions correspond to a vision under an opening angle of 10. In the given measurements, the specular component is excluded.

 Different variants of the invention will now be described.

 According to a first variant, the sulfide, as described above, further comprises a layer based on at least one transparent oxide, deposited on its surface or its periphery. Reference may also be made, with regard to a product of this type comprising such a layer, to French patent application FR-A-2703999 in the name of the Applicant, the teaching of which is incorporated here.

 This peripheral layer coating the sulphide may not be perfectly continuous or homogeneous. However, preferably, the sulfides according to this embodiment comprise a uniform coating layer and of controlled thickness of transparent oxide, and this so as not to alter the original color of the sulfide before coating.

 By transparent oxide is meant here an oxide which, once deposited on the sulfide in the form of a more or less fine film, absorbs little or no light rays in the visible range, and this of so as not to mask or little mask the intrinsic color of origin of said sulfide. In addition, it should be noted that the term oxide, which is used for convenience throughout the present description, should be understood as also covering hydrated type oxides.

 These oxides, or hydrated oxides, can be amorphous and / or crystallized.

 By way of example of such oxides, mention may more particularly be made of silicon oxide (silica), aluminum oxide (alumina), zirconium oxide (zirconia), titanium oxide, silicate zirconium ZrSiO4 (zircon) and rare earth oxides. According to a preferred variant, the coating layer is based on silica. Even more advantageously, this layer is essentially, and preferably only, made of silica.

 According to another variant, the sulphide which can be used according to the invention can also comprise fluorine atoms.

In this case, reference may also be made, with regard to the arrangement of the fluorine atoms, to French patent application FR-A-2706476 in the name of the
Applicant whose teaching is incorporated here.

Fluorinated sulfide can have at least one of the following characteristics:
- The fluorine atoms are distributed according to a decreasing concentration gradient from the surface to the heart of said sulfide.

 - the fluorine atoms are mainly distributed at the outer periphery of the sulfide. The term external periphery is understood here to mean a thickness of material measured from the surface of the particle, of the order of a few hundred Angstroms. Furthermore, the majority means that more than 50% of the fluorine atoms present in the sulphide are found in said external periphery.

 the percentage by weight of the fluorine atoms present in the sulphide does not exceed 10%, and preferably 5%.

 - The fluorine atoms are present in the form of fluorinated or sulfofluorinated compounds, in particular in the form of rare earth fluorides or sulfofluomers (thiofluorides) of rare earths.

 Of course, the invention also relates to the combination of the embodiments which have been described previously. Thus, one can consider a sulfide comprising an oxide layer and further comprising fluorine atoms.

 The process for preparing the sulfides of the invention will now be described.

 This process is characterized in that a rare earth compound is reacted with at least one sulfurizing gas chosen from hydrogen sulfide or carbon sulfide.

 The rare earth compound is preferably a carbonate or a hydroxycarbonate. Mention may also be made of nitrates. We could also use a rare earth oxide.

 Another characteristic of the process of the invention is the nature of the sulfurizing gas.

This gas can be hydrogen sulfide or carbon sulfide. According to a particular embodiment of the invention, a mixture of these two gases is used. It has been found that it is possible to modulate the color of the sulfide by varying the oxygen content of this sulfide. This oxygen content can be modified by varying the content of carbon sulphide in the gas mixture. Thus, all the other process parameters being equal, a high content of carbon sulphide promotes the production of sulphides with low oxygen contents, that is to say products of lighter colors such as light burgundy for example while that a higher hydrogen sulfide content makes it possible to obtain products with higher oxygen concentrations and therefore of darker colors. The gas or the mixture of sulfurizing gas can be used with an inert gas such as argon or nitrogen.

 The sulfurization reaction is generally carried out at a temperature between 600 "C and 1000 C, preferably around 800" C.

 The reaction time corresponds to the time necessary to obtain the desired sulfide. By way of example, this duration may be between one and four hours approximately.

 After heating, the sulfide formed is recovered. If it is desired to obtain a product with a finer grain size, this can be deagglomerated. A disaggregation under mild conditions, for example wet grinding or of the air jet type under mild conditions, makes it possible to obtain a sulphide having the size given above, in particular, an average size of aggregates of at most 1, 5clam.

 Several variants of the sulfide have been described above. The methods of preparing the sulfides according to these variants will now be described.

 For the first variant described above, that is to say for the sulphide having a layer of a transparent oxide, the preparation process can consist in bringing together the sulphide as it was obtained after the sulphurization and a precursor layer oxide, and precipitating this oxide. The methods of precipitation of the oxides and the precursors to be used are described in particular in FR-A-2703999.

 In the case of silica, mention may be made of the preparation of silica by hydrolysis of an alkyl silicate, by forming a reaction medium by mixing water, alcohol, sulfide which is then suspended, and optionally d 'a base, and then introducing the alkyl silicate, or alternatively a preparation by reaction of the sulfide, a silicate, of the alkaline silicate type, and an acid.

 In the case of an alumina-based layer, the sulfide, an aluminate and an acid can be reacted, whereby alumina is precipitated. This precipitation can also be obtained by bringing together and reacting the sulphide, an aluminum salt and a base.

 Finally, alumina can be formed by hydrolysis of an aluminum alcoholate.

 As regards titanium oxide, it can be precipitated by introducing into an aqueous suspension of sulfide according to the invention and a titanium salt on the one hand such as TiC4, TiOC12 or TiOSO4, and a base on the other go. One can also operate for example by hydrolysis of an alkyl titanate or precipitation of a titanium sol.

 Finally, in the case of a zirconium oxide-based layer, it is possible to proceed by cohydrolysis or coprecipitation of a suspension of the sulfide in the presence of an organometallic compound of zirconium, for example a zirconium alkoxide such as 'zirconium isopropoxide.

 The process for preparing the sulfide according to the second variant, sulfide comprising fluorine atoms, uses fluorination.

 The fluorination can be carried out according to any technique known per se by bringing together the sulphide and a fluorinating agent.

 In particular, the fluorinating agent can be liquid, solid or gaseous. Preferably, one operates under treatment conditions where the fluorinating agent is liquid or gaseous.

 As examples of fluorinating agents which are suitable for carrying out the treatment according to the invention, mention may more particularly be made of fluorine F2, alkali metal fluorides, ammonium fluoride, rare gas fluorides, nitrogen fluoride NF3, boron fluoride BF3, tetrafluoromethane, hydrofluoric acid HF.

 In the case of a treatment under a fluorinating atmosphere, the fluorinating agent can be used pure or in dilution in a neutral gas, for example nitrogen.

 The reaction conditions are preferably chosen so that said treatment induces fluorination only on the surface of the sulphide (mild conditions). In this regard, the conduct of a fluorination to the core of the sulfide does not bring substantially improved results compared to an essentially surface fluorination.

In a practical way, one can follow and experimentally control the degree of progress of the fluorination reaction, for example by measuring the evolution of the mass gain of materials (mass gain induced by the progressive introduction of fluorine) .

 The fluorinating agent can more particularly be ammonium fluoride.

 As indicated above, it is possible to envisage preparing a sulfide combining the characteristics constituting the different embodiments: the oxide layer and the presence of fluorine atoms. To obtain the combinations of these embodiments, the preparation methods which have just been described are combined.

 Thus, the fluorination treatment can be carried out in a first step, then, in a second step, the sulfide thus treated is brought into contact with a precursor of the transparent oxide, and the transparent oxide is precipitated on the said sulfide.

 Another process is also possible. In this case, in a first step, the sulfide is brought into contact with a precursor of the transparent oxide, then the transparent oxide is precipitated on the said sulfide and finally, in a last step, the fluorination treatment is carried out.

 The sulfide described has in fact a coloring power and a covering power and, therefore, is suitable for coloring many materials, such as plastics, paints and others.

 Thus, and more precisely, it can be used in the coloring of polymers for plastics which may be of the thermoplastic or thermosetting type, these polymers being capable of containing traces of water.

As thermoplastic resins capable of being colored according to the invention, there may be mentioned, for purely illustrative purposes, polyvinyl chloride, polyvinyl alcohol, polystyrene, styrene-butadiene, styrene-acrylonitrile, acrylonitrilebutadiene-styrene (ABS) copolymers. ), acrylic polymers, in particular polymethyl methacrylate, polyolefins such as polyethylene, polypropylene, polybutene, polymethylpentene, cellulose derivatives such as, for example, cellulose acetate,
Cellulose aceto butyrate, ethylcellulose, polyamides including polyamide 6-6.

 As regards the thermosetting resins for which the sulphide is also suitable, mention may, for example, be made of phenoplasts, aminoplasts, in particular urea-formaldehyde, melamine-formaldehyde copolymers, epoxy resins and thermosetting polyesters.

 It is also possible to use the sulfide in special polymers such as fluoropolymers, in particular polytetrafluoroethylene (P.T.F.E.), polycarbonates, silicone elastomers, polyimides.

 In this specific application for coloring plastics, the sulphide can be used directly in the form of powders. It is also possible, preferably, to use it in a pre-dispersed form, for example in premix with a part of the resin, in the form of a concentrated paste or of a liquid which makes it possible to introduce it at n no matter what stage of resin manufacturing.

 Thus, the products according to the invention can be incorporated into plastics such as those mentioned above in a weight proportion generally ranging either from 0.01 to 5% (reduced 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 stains and more particularly in the following resins: alkyd resins, the most common of which is called glycerophthalic; long or short oil modified resins; acrylic resins derived from esters of acrylic (methyl or ethyl) and methacrylic acid optionally copolymerized with ethyl acrylate, 2-ethylhexyl or butyl; vinyl resins such as, for example, polyvinyl acetate, polyvinyl chloride, butyralpolyvinyl, formalpolyvinyl, and the copolymers of vinyl chloride and vinyl acetate or vinylidene chloride; the aminoplast or phenolic resins most often modified; polyester resins; polyurethane resins; epoxy resins; silicone resins.

 Generally, the products are used in an amount of 5 to 30% by weight of the paint, and from 0.1 to 5% by weight of the stain.

 In addition, the products according to the invention are also capable of being suitable for applications in the rubber industry, in particular in floor coverings, in the paper and printing ink industry, in the cosmetic field. , as well as many other uses such as for example, and not limited to, dyes, in leathers for the finishing thereof and laminate coatings for kitchens and other worktops, ceramics and glazes.

 The products of the invention can also be used in the coloring of materials based on or obtained from at least one mineral binder.

 This mineral binder can be chosen from hydraulic binders, aerial binders, plaster and binders of the anhydrous or partially hydrated calcium sulphate type.

 By hydraulic binders is meant substances having the property of setting and hardening after addition of water by forming hydrates insoluble in water. The products of the invention apply very particularly to the coloring of cements and, of course, of concretes produced from these cements by adding thereto water, sand and / or gravel.

 In the context of the present invention, the cement may, for example, be of the aluminous type. By this is meant any cement containing a high proportion either of alumina as such or of aluminate or of both. By way of example, mention may be made of cements based on calcium aluminate, in particular those of the SECAR type.

 The cement can also be of the silicate type and more particularly based on calcium silicate. PORTLAND cements can be given as an example and, in this type of cements, Portland cures with rapid or very rapid setting, white cements, those resistant to sulfates as well as those comprising blast furnace slag and / or fly ash and / or meta-kaolin.

 We can also mention cements based on hemihydrate, calcium sulphate as well as magnesium cements known as Sorel cements.

 The products of the invention are also used for coloring aerial binders, that is to say binders hardening in the open air by the action of CO2, of the calcium or magnesium oxide or hydroxide type.

 The products of the invention are finally used for coloring plaster and binders of the anhydrous or partially hydrated calcium sulphate type (CaSO4 and CaSO4, 1 / 2H20).

 Finally, the invention relates to compositions of colored matter, in particular of the plastics, paints, stains, rubbers, ceramics, glazes, papers, inks, cosmetic products, dyes, leathers, laminated coatings or of the type based or obtained from at least one inorganic binder, which comprise as coloring pigment, a sulphide as defined above or obtained by methods of the type described above.

 Examples will now be given. In these examples, the particle size was determined according to the aforementioned technique. It is further specified that the measurement was carried out on a dispersion of the product in an aqueous solution at 0.05% by weight of sodium hexametaphosphate and which has previously undergone passage through the ultrasonic probe (probe with tip of 13mm diameter, 20KHz, 120W) for 3 minutes.

EXAMPLE 1
Synthesis of P-CelgS1400,1780.83 (light red sulfide)
Procedure.

16 g of cerium hydroxycarbonate (Ce (OH) CO3) comprising 70.7% of CeO2 were calcined under a flow of H2S (flow = 1011h) and CS2 (flow = 1.41 / h) depending on the profile
following temperature: temperature rise up to 800 C at the speed of 8 "C / min,
then stop for 1 hour at this temperature.

 Results.

 13 g of product of formula given above are obtained (a single phase present according to the X-ray photos) with a mass oxygen content of 0.15% (determined using the mesh parameter).

 The particle size obtained is 0.74pm (lm = 0.49).

The colors determined in the CIE Lab system are:
Ua * / b * = 38.9136.3116.7
The absorptions at 400 and 700nm are as follows: R400 / R700 = 5.06 / 65.63.

 10 g of the pigment thus synthesized are mixed in a cube rotating at 2 kg of a polypropylene reference ELTEX bd PHV 001. The mixture is then injected at 220 "C using a KAPSA injection press model Protoject 10/10 with a 41 s cycle.

The mold is maintained at a temperature of 35 "C.

 A double thickness (2 and 4 mm) parallelepipedic test piece is thus obtained.

It is observed that the pigment disperses well. The chromaticity coordinates and the absorptions, measured on the thick part of the plate, are as follows: Ua * / b * = 33.5139.6120.6
R400 / R700 = 2.4 / 60.2.

EXAMPLE 2
Synthesis of frCe1 OSi 400,8S012 (dark red suture)
Procedure.

 14 g of cerium hydroxycarbonate (Ce (OH) CO3) comprising 70.7% of CeO2 were calcined under a flow of H2S (flow rate = 1011h) according to the temperature profile according to temperature rise up to 800 "C at the speed of 8 "C / min, then leveling for 3 hours at this temperature.

Results:
11.2 g of product of formula given above are obtained (a single phase present according to the X-ray photos) with a mass oxygen content of 0.69% (determined using the mesh parameter).

 The particle size obtained is 0.76 m (a / m = 0.44).

The colors and absorptions determined in the CIE Lab system are:
Lla * lb * = 36.1 / 27.4 / 12
R400 / R700 = 5.06 / 64.35.

After injection into polypropylene under the conditions of Example 1, the colors and absorptions become:
Ua * / b * = 29.7 / 31.4 / 16.4
R400 / R700 = 2.05 / 59.5.

Claims (10)

1- Use as coloring pigment of a rare earth sulfide, characterized in that a beta-form sulfide is used, the rare earth being lanthanum, cerium, praseodymium, samarium or neodymium 2- Use according to claim 1, characterized in that a sulphide consisting of whole crystallites is used, said crystallites forming aggregates of average size of at most 1.5clam. 3- Use according to claim 2, characterized in that one implements a sulfide whose average size of the aggregates is at most 1 pm, more particularly at most 0.8clam. 4 Use according to claim 1, 2 or 3, characterized in that one implements a sulfide which is in the form of a pure phase. 5- Use according to one of the preceding claims, characterized in that a sulphide is used, the rare earth of which is cerium and which has a chromatic coordinate L * of less than 40 and a lower ratio b * / a * at 0.6. 6- Use according to one of the preceding claims, characterized in that a sulfide is used which comprises a layer based on at least one transparent oxide, deposited on its surface or on its periphery. 7- Use according to one of the preceding claims, characterized in that one implements a sulfide which further comprises fluorine atoms, more particularly distributed in a decreasing gradient from the surface to the heart of the sulfide. 8- Compositions of colored material, in particular of the plastics, paints, stains, rubbers, ceramics, glazes, papers, inks, cosmetic products, dyes, leathers, laminated coatings or of the type based or obtained from at least one mineral binder , characterized in that they are obtained by using a sulphide according to one of claims 1 to 7. 9- Process for the preparation of a rare earth sulphide for the use according to one of the preceding claims, characterized in that a compound of the rare earth is reacted with at least one sulphurizing gas chosen from sulphide hydrogen or carbon sulfide.  1 G Method according to claim 9, characterized in that the rare earth compound is a carbonate or a hydroxycarbonate. 11- Process according to claim 9 or 10, characterized in that the reaction is carried out at a temperature between 600 "C and 1000 C. 12- Process for preparing a sulfide for the use according to claim 6, characterized in that the sulfide obtained by the process according to one of claims 9 to 1 1 and a oxide precursor are brought into contact forming a layer, and this oxide is precipitated. 13- A process for preparing a sulfide for use according to claim 7, characterized in that the sulfide obtained by the process according to one of claims 9 to 1 1 is brought into contact with a fluorinating agent.