EP0986516A1

EP0986516A1 - Titanium, cerium and alkaline or earth-alkaline based compound, preparation methods and use as colouring pigment

Info

Publication number: EP0986516A1
Application number: EP98929492A
Authority: EP
Inventors: Catherine Hedouin; Thierry Seguelong
Original assignee: Rhodia Chimie SAS
Current assignee: Rhodia Chimie SAS
Priority date: 1997-06-06
Filing date: 1998-06-04
Publication date: 2000-03-22
Also published as: US6294011B1; FR2764282A1; KR100354475B1; FR2764282B1; AU743575B2; AU7923598A; CN1263510A; CA2292747A1; KR20010013450A; JP2000513700A; WO1998055401A1

Abstract

The invention concerns a compound based on titanium, cerium and alkaline or earth-alkaline, its preparation methods and use as colouring pigment, characterised in that it corresponds to formula (1) MxCeyTizOt in which M represents an alkaline or earth-alkaline and x, y and z verify the following equations: 0.1 ≤ y/z ≤ 1.5; 1 ≤ (x+z)/y ≤ 15; x+y+z = 1; (x+3y+4z)/2 ≤ t ≤ (x+4y+4z)/2. The product can be prepared by forming a mixture comprising a salt, sol or suspension of titanium, a compound of element M and a cerium compound then drying and calcining the resulting mixture. In a second embodiment the mixture is prepared by bringing together a cerium compound and a titanium compound in a liquid medium; adding a base to the resulting mixture, thereby obtaining a precipitate; bringing together a compound of element M and the resulting precipitate; drying and calcining the resulting mixture.

Description

TITANIUM-BASED COMPOUND. OF CERIUM AND ALKALINE OR ALKALINE EARTH. ITS PREPARATION METHODS AND ITS USE AS A COLORING PIGMENT

RHONE-POULENC CHEMISTRY

The present invention relates to a compound based on titanium, cerium and alkali or alkaline earth, its methods of preparation and its use as a coloring pigment.

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.

The problem that arises is that most of the mineral pigments which are suitable for applications such as above and which are actually used to date on an industrial scale, 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 reputedly very high toxicity. Mention may more particularly be made, by way of nonlimiting examples, of the case of yellow pigments of the lead chromate or molybdate type.

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

The object of the present invention is therefore to provide a substitution pigment in the range of yellow and free from toxic metals.

For this purpose, the compound based on titanium, cerium and alkali or alkaline earth of the invention is characterized in that it corresponds to formula (1):

M _x Ce _y Ti _z O _t in which M represents an alkali or an alkaline earth and x, y and z satisfy the following equations:

0.1≤ y / z ≤1.5

1≤ (x + z) / y ≤15 x + y + z = 1 (x + 3y + 4z) / 2 <t ≤ (x + 4y + 4z) / 2 The invention also relates to a process for preparing the compound as defined above which, according to a first variant, is characterized in that it comprises the following stages: - a mixture comprising a salt, a sol or a suspension of titanium, a compound of element M and a compound of cerium is formed;

- drying and calcining the mixture thus formed.

According to a second variant, the process for preparing the compound as defined above is characterized in that it comprises the following stages: - a compound of cerium, a compound of titanium and a base is brought into contact, whereby a precipitate is obtained;

- A compound of the element M and the precipitate thus obtained are brought into contact;

- It is dried and then the mixture obtained is calcined.

Other characteristics, details and advantages of the invention will appear even more completely on reading the description which follows, as well as various concrete but nonlimiting examples intended to illustrate it.

The product of the invention is a compound based on titanium, cerium and alkali or alkaline earth. It will be noted that the formula (1) given above is intended only to indicate the relative proportions of the different elements without prejudging the structure of the compound. It should be noted here that the invention also applies to products in which M represents an alkaline / alkaline-earth mixture. Furthermore, the compound of the invention can also comprise an additional rare earth other than cerium. By rare earth is meant the elements of the group constituted by yttrium and the elements of the periodic classification with atomic number included inclusively between 57 and 71. This additional rare earth can be more particularly lanthanum, neodymium, praseodymium or terbium . The total content of cerium and of any additional rare earth is defined by the value of y given in the description.

As alkali, mention may be made of sodium, preferably, and also lithium, potassium and cesium. According to a particular embodiment of the invention, x, y and z satisfy the following equations:

0.2≤ y / z ≤1, 3 1, 5 <(x + z) / y <8 Cerium can be present in different forms in the compound of the invention. Thus, it can appear in the lll ⁺ state. It can also occur in the IV ⁺ state. It can also be present at the same time in both states. The oxidation state of cerium can be demonstrated by electron microscopy. The compound of the invention comprises, at least in part, a titanate of cubic perovskite structure. Generally, it has a mixture of phases in which one or more other phases different from the cubic perovskite phase exist, for example Ceθ2, Na2ÎigO- | 3, Na2 ^" T ^" i5θι ι, There may also be the presence of another mixed titanate (based on sodium, cerium and titanium for example) of orthorhombic structure.

The compound of the invention is preferably a micronic product. Thus, its average particle size is preferably at most 2.5 μm, more particularly at most 1.5 μm (Cilas particle size). The invention also relates to pigment compositions which comprise a compound as described above. The term “pigment composition” means any composition capable of being able to color the substrate in which it is incorporated. The preparation of the compound of the invention will now be described. According to a first variant, the method comprises a first step in which a mixture is formed comprising a salt, a sol or a suspension of titanium, a compound of element M and a compound of cerium.

Titanium is generally used in the form of a compound of this element. This compound can be a salt. This titanium salt is generally chosen from halides, oxyhalides, sulfates, oxysulfates and titanium alkoxides. More particularly, titanium can be used in the form of titanium dioxide in suspension or in the form of a sol.

One can in particular use as starting titanium dioxide a product resulting from the calcination of a titanium dioxide gel at a temperature which can be for example between 400 and 600 ° C. Said gel can be obtained by neutralizing a solution of a titanium salt with a base.

This titanium salt is generally chosen from the salts mentioned above. More particularly, a titanium halide or oxyhalide will be used, preferably titanium oxychloride. As usable base, there may be mentioned ammonia, urea, ammonium acetate, ammonium hydrogen carbonate, ammonium carbonate, or a primary, secondary, tertiary amine, such as, for example , methylamine, ethylamine, propylamine, n-butylamine, sec-butylamine, n-pentylamine, 2-amino pentane, 2-amino-2-methyl butane, 1-amino methyl- 3 butane, diamino-1, 2 ethane, diamino-1, 2 propane, diamino-1, 3 propane, diamino-1, 4 butane, diamino-1, 5 pentane, diamino-1, 6 hexane , dimethylamine, diethylamine, trimethylamine, triethylamine or a quaternary amine such as, for example, a tetraalkylammonium hydroxide preferably having alkyl radicals containing from 1 to 4 carbon atoms, in particular tetramethylammonium hydroxide or tetraethylammonium hydroxide, the so-called mineral bases such as soda, potash, ammonia, lithium hydroxide. It is also possible to use a mixture of bases. The gel can also be obtained by thermohydrolysis of a titanium salt, such as a sulfate or a titanium oxychloride.

It is also possible to use a titanium dioxide sol. This sol can be obtained by thermohydrolysis of a solution of a titanium salt, possibly in the presence of germs of titanium dioxide or one of its hydrates (thermohydrolysis seeded).

This titanium salt can also be chosen from halides, oxyhalides, sulfates, oxysulfates and titanium alkoxides. For example, titanyl sulfate will be used.

The soil can also be obtained by following the process described in EP-A-335773, the teaching of which is incorporated here. This process consists in resuspending in an aqueous liquid medium a titanium dioxide which has been obtained by hydrolysis of a titanium oxychloride in the presence of an acid or a salt of an acid of the citric acid, gluconic acid type. , tartaric acid, aspartic acid. The above-mentioned aqueous liquid medium can be acidic or basic. As indicated above, since the cerium can be present in the compound in the form III ⁺ and or IV ⁺ , the cerium can be provided in the form of a compound of cerium III ⁺ and / or of a compound of cerium IV ⁺ .

The element M and the cerium are generally brought in the form of a salt. Water-soluble salts are preferably used. Inorganic salts or organic salts can be used. As inorganic salts, there may be mentioned more particularly nitrates. In the case of cerium, it can be used for example in the form of cerium nitrate III ⁺ and / or cerium nitrate IV ⁺ . An aqueous solution of ceric nitrate can for example be obtained by reaction of nitric acid with a hydrated ceric oxide prepared in a conventional manner by reaction of a solution of a cerous salt, for example cerous nitrate, and an ammonia solution in the presence of hydrogen peroxide. It is also possible to use a ceric nitrate solution obtained according to the electrolytic oxidation process of a cerous nitrate solution as described in document FR-A-2 570 087, and which can constitute an advantageous raw material. It will be noted here that the aqueous solution of cerium IV salts may have a certain initial free acidity, for example a normality varying between 0.1 and 4 N. According to the present invention, it is as much possible to use an initial solution of cerium IV salts actually showing some free acidity as mentioned above, that a solution which will have been previously neutralized in a more or less extensive manner by adding a base, such as for example an ammonia solution or also alkali hydroxides (sodium, potassium, etc. .), but preferably an ammonia solution, so as to limit this acidity. We can then, in the latter case, define in a practical way a neutralization rate (r) of the initial cerium solution by the following equation:

r = n3 - n2 ni

in which ni represents the total number of moles of Ce IV present in the solution after neutralization; n2 represents the number of moles of OH ions "effectively necessary to neutralize the initial free acidity provided by the aqueous solution of cerium salt IV; and n3 represents the total number of moles of OH ions" provided by the addition of the base. When the "neutralization" variant is used, in all cases a quantity of base is used which must imperatively be less than the quantity of base which would be necessary to obtain the total precipitation of the hydroxide species Ce (OH) 4 ( r = 4).

As organic salts of element M and of cerium, oxalates and acetates can be mentioned.

Titanium, element M and cerium are mixed in the proportions corresponding to the stoichiometry of the desired compound.

The above-mentioned mixing can be carried out by first bringing together the titanium salt, sol or suspension and a compound of element M, then, secondly, by adding to the first mixture thus obtained a compound of cerium. In a second stage of the process, the mixture obtained above is dried.

According to a preferred variant of the invention, the drying is carried out by atomization. By spray drying is meant spray drying of the mixture in a hot atmosphere (spray-drying). The atomization can be carried out by means of any sprayer known per se, for example by a spray nozzle of the sprinkler apple type or the like. One can also use so-called turbine atomizers. On the various spraying techniques likely to be used in the present process, reference may be made in particular to the basic work by MASTERS entitled "SPRAY-DRYING" (second edition, 1976, Editions George Godwin - London).

For atomization, the gas inlet temperature can be for example between 200 and 220 ° C. The gas outlet temperature can be between

100 and 150 ° C. It will be noted that it is also possible to carry out the spray-drying operation by means of a "flash" reactor, for example of the type developed by the Applicant and described in particular in French patent applications no. 2 257 326, 2 419 754 and 2 431 321. In this case, the treating gases (hot gases) are driven in a helical movement and flow in a vortex well. The mixture to be dried is injected along a trajectory coincident with the axis of symmetry of the helical trajectories of said gases, which allows the momentum of the gases to be transferred perfectly to the mixture to be treated. The gases thus in fact perform a double function: on the one hand the spraying, that is to say the transformation into fine droplets, of the initial mixture, and on the other hand the drying of the droplets obtained. Furthermore, the extremely short residence time (generally less than about 1/10 of a second) of the particles in the reactor has the advantage, inter alia, of limiting possible risks of overheating as a result of too long contact with the hot gases. One can use more particularly the "flash" reactor represented in FIG. 1 of French patent application 2431 321.

Depending on the respective flow rates of the gases and of the mixture to be dried, the inlet temperature of the gases is between 400 and 900 ° C. and more particularly between 600 and 800 ° C., the temperature of the dried solid between 150 and 300 ° C. Drying can also be done by lyophilization. The dried product is then calcined. This calcination is usually done in air. It can also be done in a neutral medium, under nitrogen for example, or in a slightly reducing medium. The calcination temperature can be between 700 and 800 ° C. This temperature can more particularly be fixed at 750 ° C. or approximately 750 ° C. The higher the calcination temperature, the more the color of the compound turns green. The lower this temperature, the more the color becomes pale yellow. The duration of the calcination can vary for example between 1 and 3 hours. Too long a calcination time may cause a magnification of the product obtained.

Calcination can be carried out by introducing the product into an oven at room temperature, then raising the oven temperature to the values indicated above and maintaining the temperature in stages over the duration indicated. One can also proceed by introducing the product directly into the oven which has been previously heated to the desired calcination temperature.

According to a second variant, the process for preparing the compound comprises a first step in which a compound of cerium, a compound of titanium and a base are brought into contact in a liquid medium. This liquid medium can be either water or an organic solvent. When the liquid medium is water, it is possible to use a titanium salt or suspension and a cerium salt as respective compounds of the titanium and cerium, the salts being preferably soluble. When the liquid medium is an organic solvent, use is preferably made of soluble titanium and cerium salts. The organic solvent is preferably a polar solvent to best dissolve the salts. Examples of solvents that may be mentioned include alcohols such as ethanol. The fact of working in an organic solvent makes it possible to avoid any hydrolysis of the salts. What was said above in the description of the first variant of the process concerning the cerium and titanium salts also applies here.

Mention may be made, as base, of ammonia, urea, ammonium acetate, ammonium hydrogen carbonate, ammonium carbonate, or primary, secondary and tertiary amines, so-called mineral bases such as soda, potash, ammonia, lithium hydroxide. It is also possible to use a mixture of bases. As the preferred base, ammonia is used.

This can be done by first bringing the cerium compound and the titanium compound into the liquid medium and then adding the base to the mixture thus obtained, whereby a precipitate is obtained;

The precipitation can also be carried out while keeping the pH of the precipitation medium constant. In this case, it is possible, for example, to form a liquid medium containing the titanium compound and then add thereto the cerium compound with the base. In the case of the use of a cerium III salt, the pH value can thus be fixed between 7 and 10. In a following step, a compound of the element M is brought into contact with the precipitate thus obtained. What has been said previously on the compounds of the element M, also applies here. The compound of the element M and the precipitate can be brought into contact in particular by redispersing the precipitate in a solution of a salt of the element M. This step can be carried out in the aqueous phase. Finally, in a last step, it is dried and then the mixture obtained above is calcined. The drying and calcination conditions for this second variant are the same as those given for the first.

The preparation of the compound of the invention can be done according to a third variant. This variant corresponds to a process of the solid-solid reaction or chamotte type. In this case, a mixture of solid compounds of cerium, titanium and the element M is formed and said mixture is calcined. As solid cerium compound, there may be mentioned cerium oxide, cerium carbonate or hydroxycarbonate and solid cerium salts. For titanium, titanium oxide can be used. For element M, mention may be made of the carbonates, oxalates, nitrates, borates and iodides of this element. The calcination conditions will depend on the nature of the precursors used. It will be calcined at a temperature sufficient to obtain the desired phase. The calcination time can be longer than that given for the other variants, for example, it can be of the order of ten hours. The compound of the invention having the characteristics mentioned above or as obtained by the methods which have just been described can be used very particularly as coloring pigment.

The product of the invention 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, purely by way of illustration, polyvinyl chloride, polyvinyl alcohol, polystyrene, styrene-butadiene, styrene-acrylonitrile, acrylonitrile-butadiene-styrene copolymers. (ABS), 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 product according to the invention is also suitable, mention may, for example, be made of phenoplasts, aminoplasts, in particular urea-formaldehyde, melamine-formaldehyde copolymers, epoxy resins and thermosetting polyesters.

The product of the invention can also be used 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 product of the invention 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 paste concentrate or of a liquid which makes it possible to introduce it at n no matter what stage of resin manufacturing. Thus, the product 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 product 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 acid

(methyl or ethyl) and methacrylic, optionally copolymerized with acrylate ethyl, 2-ethyl hexyl or butyl; vinyl resins such as, for example, polyvinyl acetate, polyvinyl chloride, butyralpolyvinyl, formalpolyvinyl, and 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 product is 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 product according to the invention is also likely to be 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 product 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 product of the invention is also used in the coloring of 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 product of the invention is finally used in the coloring of plaster and binders of the anhydrous or partially hydrated calcium sulphate type (CaSθ4 and CaSO I / 2H2O).

Finally, the invention relates to 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 on or obtained from at least one mineral binder, which comprise, as coloring pigment, a product according to the invention or obtained by methods of the type described above.

Examples will now be given.

Examples 1 to 7 and 9 to 10 relate to the preparation of products according to the invention. The characteristics of the products are indicated in table 1 given below. The quantities of reagents used are those corresponding to the x, y and z values given in the table.

EXAMPLES 1 AND 2 A basic titanium sol is used (in NaOH medium) having a dry extract of

20%. This soil is mixed with sodium oxalate dissolved hot in deionized water. Cerous nitrate solution is added to the mixture. The suspension is then atomized by a Bϋchi® dryer. The gas outlet temperature is 120 ° C. The product obtained is calcined for 2 hours at 750 ° C (temperature rise: 5 ° C / min).

EXAMPLE 3

Sodium oxalate is introduced into permuted water and then a powder of a titanium gel calcined at 500 ° C. Finally, a cerous nitrate solution is added. The suspension is then atomized by a Bùchi® dryer. The gas outlet temperature is 120 ° C. The product obtained is calcined for 2 hours at 750 ° C (temperature rise: 5 ° C / min).

EXAMPLE 4 Crystallized sodium nitrate is dissolved in ceric nitrate obtained by electrolytic oxidation of a cerous nitrate solution and having a neutralization rate as defined above of r = 0. Dilute and add the same gel as that of example 3. The suspension is then atomized by a Bûchi® dryer. The gas outlet temperature is 130 ° C. The product obtained is calcined under the same conditions as above. EXAMPLE 5

Cerous nitrate is added to tetrabutylorthotitanate diluted in ethanol. Then, at a stroke, concentrated ammonia is added in an amount sufficient to precipitate the titanium and the cerium. The precipitate thus obtained is filtered then washed and redispersed in a solution of sodium nitrate. The suspension is then atomized by a Bùchi® dryer. The gas outlet temperature is 120 ° C. The product obtained is calcined under the same conditions as above.

EXAMPLE 6

Sodium nitrate is introduced into permuted water and then a powder of a titanium gel calcined at 500 ° C. Finally, a cerous nitrate solution is added. The drying is done in a flash reactor of the type described above. The inlet gas temperature is 600 ° C, that of the outlet 130 ° C. Calcination is carried out under the same conditions as in Example 3.

EXAMPLE 7

The procedure is as in Example 4 but using sodium iodide. In addition, the calcination is carried out by introducing the product obtained after atomization into the oven at 750 ° C. The product is kept for 2 hours at this temperature.

Table 1

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 for the measurements made on products and plastics using a colorimeter sold by the Pacific Scientific Company. The nature of the illuminant is D65. The observation surface is a circular patch of 12.5 cm ^ of surface. The observation conditions correspond to a vision under an opening angle of 10 °. In the given measurements, the specular component is excluded.

EXAMPLE 8

This example illustrates the use of the products of the invention for coloring plastics. 10 g of products according to Examples 1, 2 and 3 are mixed in a rotating cube to 2 kg of a reference polypropylene ELTEX® PHV 001. The mixture is then injected at 220 ° C. using an injection press KAPSA model Protoject 10/10 with a cycle of 41 s. The mold is maintained at the temperature of 35 ° C.

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

The colorimetric coordinates, measured on the thick part of the plate and on a white background, are given in table 2 below:

Table 2

the specular component is included, 1% of pigment has been introduced into the plastic.

EXAMPLE 9

This example relates to the preparation of a product comprising cerium and lanthanum of formula Na _x (Ce, La) _y Ti _z Ot.

Dissolved sodium nitrate crystallized in ceric nitrate obtained by electrolytic oxidation of a cerous nitrate solution and having a neutralization rate as defined above of r = 0. A lanthanum nitrate solution is then added and then a powder of a titanium gel calcined at 500 ° C. The amounts of lanthanum and cerium in the prepared product are in the La / Ce atomic ratio of 0.7 / 2.

The product obtained is calcined for 2 hours at 750 ° C.

The characteristics of the product obtained are given in table 3. EXAMPLE 10

This example illustrates the preparation of products by a chamotte route.

Powdered cerium hydroxycarbonate powders, titanium gel calcined at 500 ° C and sodium nitrate are mixed in an agate crucible. The mixture obtained is calcined for 12 hours at 750 ° C. The characteristics of the product obtained are given in table 3.

Table 3

EXAMPLE 11

This example illustrates the preparation of a product according to the invention by a precipitation process.

The suspension of a dried T.O2 gel (80 g / l of TiO 2) is introduced into a reactor equipped with an agitator. The pH of the suspension is adjusted to 8 using an 8M ammonia solution. . With constant stirring and at controlled pH (pH = 8) by adding ammonia, a solution of cerous nitrate is then added slowly. The precipitate obtained is centrifuged (4500 rpm) then washed twice with an ammonia solution. The precipitate thus obtained is then resuspended in water (C = 150 g I) and then atomized with Bùchi® in the presence of the sodium carbonate solution. The inlet and outlet temperatures of Bùchi® are respectively 210 ° C and 100 ° C. The dried solid is calcined for 2 hours at 750 ° C (rate of rise 5 ° C / min). The product is then injected into polypropylene under the conditions described in Example 8. The characteristics of the product obtained are given in Table 4 below. The colorimetric coordinates after injection into the polypropylene are measured as in Example 8.

Table 4

The color coordinates after injection into the polypropylene are L * = 82.7; a * = - 1; b * = 58.6.

Claims

1- Compound based on titanium, cerium and alkaline or alkaline-earth, characterized in that it corresponds to formula (1):

M _x Ce _y Ti _z Ot in which M represents an alkali or an alkaline-earth and x, y and z satisfy the following equations:

0.1≤ y / z ≤1.5 1≤ (x + z) / y ≤15 x + y + z≈1 (x + 3y + 4z) / 2 <t <(x + 4y + 4z) / 2

2- Compound according to claim 1, characterized in that x, y and z satisfy the following equations:

0.2≤ y / z <1.3 1.5, <(x + z) / y <8

3- Compound according to claim 1 or 2, characterized in that M is sodium.

4- Compound according to one of the preceding claims, characterized in that it comprises cerium in the III ⁺ state and cerium in the IV ⁺ state.

5- Compound according to one of the preceding claims, characterized in that it comprises, at least in part, a titanate of cubic perovskite structure.

6- Compound according to one of the preceding claims, characterized in that it comprises an additional rare earth other than cerium.

7- Pigment composition, characterized in that it comprises a compound according to one of the preceding claims.

8- Process for the preparation of a compound according to one of claims 1 to 6, characterized in that it comprises the following steps: - a mixture comprising a salt, a sol or a suspension of titanium, a compound of element M and a cerium compound; - drying and calcining the mixture thus formed. 9- Process for the preparation of a compound according to one of claims 1 to 6, characterized in that it comprises the following steps:

- A compound of cerium, a compound of titanium and a base is brought into contact in a liquid medium, whereby a precipitate is obtained;

- dried and then calcined the mixture obtained.

10- A method according to claim 9, characterized in that the liquid medium is an organic solvent.

11- A method according to claim 8, characterized in that the above mixture is formed by first bringing into contact, a salt, a sol or a suspension of titanium and a compound of the element M, then, in a second step, a cerium compound is added to the mixture thus obtained.

12- Method according to one of claims 8 to 11, characterized in that it is dried by atomization or lyophilization.

13- Method according to one of claims 8 to 12, characterized in that the compound of element M, cerium or titanium is a salt.

14- A method of preparing a compound according to one of claims 1 to 6, characterized in that a mixture of solid compounds of cerium, titanium and the element M is formed and said mixture is calcined.

15- Use of a compound according to one of claims 1 to 6 or obtained by a process according to one of claims 8 to 14, as a coloring pigment.

16- Use according to claim 15, characterized in that the compound is used as a pigment in plastics, paints, stains, rubbers, ceramics, glazes, papers, inks, cosmetic products, dyes , leathers, laminate coatings and materials based on or obtained from at least one mineral binder.

17- 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 comprise, as coloring pigment, a compound according to one of claims 1 to 6 or obtained by a process according to one of claims 8 to 14 or a composition according to claim 7.