FR2801894A1 - COMPOSITION BASED ON A RARE EARTH SULFIDE HAVING AN ORGANIC SURFACE GROUP, ITS USE AS PIGMENT COLORS, IN PARTICULAR IN PAINTS - Google Patents

Abstract

The invention relates to a composition which is based on a rare-earth sulfide and to its use as a colored pigment, especially in paints. The composition comprises a support which is based on a rare-earth sulfide and which contains at least one alkaline and/or alkaline-earth element, at least part of which is included in the crystalline network of said sulfide; and a layer which at least partially coats the support and which is based on at least one oxide which may have OH radicals on the surface. The invention is characterized in that the composition has on its surface groups from the deposit on the coated support comprising at least one compound chosen from the following; water-insoluble fatty alcohols, water-insoluble aliphatic amines, silanes comprising an alkoxylated radical, epoxy-functionnalized silazanes or polyorganosiloxanes. The inventive composition is produced according to a method in which the coated support is brought into contact with at least one of the aforementioned compounds, a condensation reaction is carried out on the support and the resulting composition is separated from the reaction medium.

Description

<B> <U> COMPOSITION BASED ON RARE EARTH SULFIDE </ U> </ B> WITH <B> <U> ORGANIC SURFACE, USE </ U> </ B> <B> The present invention relates to a composition based on a rare earth sulphide, particularly in the case of paints, paints and varnishes. on the surface of which has been deposited an organic group, and its use as a colored pigment especially in paints.

Mineral pigments are widely used in many industries including paints, plastics and ceramics. However, most of the inorganic pigments which are suitable for applications as above and which are actually used at the present time on an industrial scale, generally use metals (cadmium, lead, chromium, cobalt in particular) of which employment is becoming more and more strictly regulated, even banned, by the legislation of many countries, given their very high toxicity. The case of red pigments based on cadmium selenide and / or cadmium sulphoselenide, and for which rare earth sulphide-based substitutes have already been proposed, may more particularly be mentioned as non-limiting examples. by the Applicant. Compositions based on rare earth sesquisulfides and alkaline elements have thus been described in EP-A-545746.

These new pigments have proved to be particularly useful substituents. However, it appears interesting to further improve their properties. Thus, the thermal resistance, the durability measured by the acid resistance or the ultraviolet resistance are among these properties. Moreover, there is also a need for pigments that can be used in paints. The known pigments for paints generally undergo treatments fixing organic products of the hydrophobic type on their surface, but these products tend to solubilize in the paint and to migrate to the interfaces of the film or film of paint when it is dried. which can cause a detachment of this film.

The object of the invention is therefore the development of pigment type compositions suitable for use in painting.

Another object of the invention is to provide pigment compositions which have good properties as regards heat resistance or durability in their application medium, for example in paints or in plastics.

For this purpose, the composition according to the invention is of the type comprising a support based on a rare earth sulphide which contains at least one alkaline and / or alkaline earth element of which at least part is included in the crystal lattice of said sulfide; a layer at least partly coating said support and based on at least one oxide capable of having surface OH groups; and it is characterized in that it has on its surface groups resulting from the deposit on the coated support of at least one compound chosen from water-insoluble fatty alcohols, water-insoluble aliphatic amines, silanes comprising an alkoxylated group, silazanes or epoxyfunctionalized polyorganosiloxanes.

The invention also relates to a process for the preparation of such a composition which is characterized in that it comprises the following steps: the coated support is brought into contact with at least one abovementioned compound; whereby a condensation reaction of the compound is carried out on the support; the resulting composition is separated from the reaction medium.

Other features, details and advantages of the invention will appear even more fully on reading the description which follows, as well as various concrete but non-limiting examples intended to illustrate it.

The composition of the invention comprises two main constituents, the coated support and the surface group thereof. These two constituents will now be described successively.

As indicated above, the support is based on a rare earth sulphide which contains at least one alkaline and / or alkaline earth element of which at least part is included in the crystal lattice of said sulphide.

Reference may be made here to the teaching of the European patent application EP-A-545746. It may be recalled that the alkaline element may be chosen in particular from lithium, sodium or potassium. Of course, the sulfide may include several alkali or alkaline earth elements.

According to one variant, the alkaline or alkaline-earth element is included essentially or totally in the crystal lattice.

The sulphide may be more particularly a sesquisulphide.

The sesquisulphide may in particular have a cubic crystallographic structure of Th3P4 type, which has gaps in the cation network; this lacunary structure can be symbolized by giving to the sesquisulphides the formula M10,66 1 11,33 S16 (see in particular on this subject, WH ZACHARIASEN, "Crystal Chemical Studies of the 5f-Series of Elements." The Ce2S3-Ce3S4 Type of Structure " , Acta Cryst., (1949), 2, 57).

The alkaline or alkaline-earth elements can be introduced into these cationic vacancies, until saturation or not of these latter. The presence of this element in the sulphide or sesquisulphide can be evidenced by simple chemical analysis. Furthermore, the X-ray diffraction analyzes show that there is preservation of the Th3P4 crystalline phase of the sesquisulphide, with in some cases a more or less significant modification of the mesh parameters, a function of both the nature and the amount of alkaline or alkaline earth element introduced.

In the case of sesquisulphide, the rare earth may be more particularly cerium or lanthanum. Even more particularly, the rare earth sesquisulphide is a sesquisulphide Ce2S3 and cubic.

Generally, the amount of alkaline or alkaline earth element is at most 50% of the rare earth molar amount of sulfide or sesquisulphide.

According to another characteristic, the molar amount of alkali or alkaline earth is at least 0.1%, and advantageously between 5% and 50% and more particularly 5 and 20%, of the molar amount of rare earth.

Mention may also be made as rare earth sulfides used as support in the context of the present invention, those described in the European patent application EP-A-680930 to the description of which we can refer. These rare earth sulphides comprise at least one alkaline element and they consist of whole monocrystalline grains of average size of at most 1.5 Nm. They are obtained by a process in which at least one rare earth carbonate or hydroxycarbonate is brought into contact with at least one compound of an alkaline element and the mixture is heated in the presence of at least one gas chosen from hydrogen or carbon disulfide. These products also have an average size (CILAS particle size) generally less than 2 Nm, more particularly between 0.7 and 1.5 Nm. After deagglomeration under mild conditions, the average size may be at most 1.5 Nm and advantageously between 0.3 and 0.8 Nm.

The support of the composition further comprises a layer based on at least one oxide deposited on its surface of the support.

This peripheral layer coating the support may not be perfectly continuous or homogeneous. However, preferably, this coating layer is uniform and of controlled thickness.

The oxide must be capable of having -OH surface groups. It is also generally and preferably a transparent oxide. By transparent oxide is meant here an oxide which, once deposited on the support in the form of a film more or less fine, absorbs little or no light at all in the visible range, and this of so as not to mask the original intrinsic color of said support. In addition, it should be noted that the term oxide, which is used for convenience throughout this specification, 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 be made more particularly of silicon oxide (silica), aluminum oxide (alumina), zirconium oxide (zirconia), titanium oxide and 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 solely, silica. The aforementioned oxides thus have surface groups of the type AI-OH, Ti-OH or Si-OH.

Reference may also be made to a product of this type comprising such a layer, and to its process of preparation, to the European patent application EP-A-620254.

The second constituent of the composition of the invention is the group present on the surface of the coated support.

This surface group is derived from the deposition of a compound which will now be described, on the coated support. Without wishing to be bound by a theory, it may be thought that the group is grafted or adsorbed on the support, via the OH groups mentioned above.

The compound deposited on the support may first be selected from water insoluble fatty alcohols.

By fatty alcohols is meant aliphatic primary alcohols having at least 8 carbon atoms. Mention may in particular be made of C 8 -C 30 fatty alcohols, more particularly Ca-C25 fatty alcohols.

As alcohol may be mentioned stearic alcohol or octadecanol CH3 (CH2), 7OH.

By way of example and in the case of the compounds of the alcohol type which have just been described and of a silica support, it can be thought that the grafting with the support is of the Si-OR type, R representing the carbon residue of the 'alcohol.

The compound may also be selected from aliphatic amines insoluble in water. Amines in which the carbon chain has at least 10 carbon atoms, more particularly between 10 and 35, are generally used. The aliphatic chain of the amine may optionally comprise an ethylenic linkage. As amine, mention may be made especially of oleylamine CH 3 (CH 2) 7 CH =CH (CH 2), NH 2.

Still as an example and in the case of the compounds of the amine type which have just been described and of a silica support, it is possible to think that the grafting with the support is of the Si-NR type, R representing the carbon residue of the mine.

The compound may also be chosen from silanes comprising at least one alkoxylated group. The term "B" is understood to mean the products of formula (R) 4 Si, the radicals R representing identical or different carbon groups, at least one of them being an alkoxy radical. These alkoxy radicals may be more particularly methoxy or ethoxy radicals. Preferably, one of the other radicals is a carbon chain of at least 8 carbon atoms.

By way of example, there may be mentioned octadecyltrimethoxysilane CH3 (CH2) "- Si (OCH3) 3, dimethyloctadecylmethoxysilane CH3 (CH2)" - Si (OCH3) (CH3) 2. In the case of compounds of the silane type, it can be thought that the grafting with the support is of the support-O-Si (R) type, R representing the carbon residues of the silane.

Enfin, le composé peut être choisi parmi les polyorganosiloxanes époxyfonctionnalisés. II s'agit de produits du type silicone constitués de motifs de formule<B>(I)</B> et terminé par des motifs de formule<B>(11)</B> représentées ci-dessous

dans lesquelles les symboles R1 sont semblables ou différents et représentent un radical alkyle linéaire ou ramifié contenant 1 à 8 atomes de carbone, les radicaux alkyles étant de préférence méthyle, éthyle, propyle, et octyle, un radical cycloalkyle contenant entre 5 et 8 atomes de carbone cycliques, éventuellement substitué, un radical aryle contenant entre 6 et 12 atomes de carbone pouvant être substitué, de préférence phényle ou dichlorophényle, une partie aralkyle ayant une partie alkyle contenant entre 5 et 14 atomes de carbone et une partie aryle contenant entre 6 et 12 atomes de carbone, substituée éventuellement sur la partie aryle par des halogènes, des alkyles et/ou des alkoxyles contenant 1 à 3 atomes de carbone, les symboles Y' sont semblables ou différents et représentent le groupement R1, et/ou un groupement époxyfonctionnel, relié au silicium du polyorganosiloxane par l'intermédiaire d'un radical divalent contenant de 2 à 20 atomes de carbone et pouvant contenir au moins un hétéroatome, de préférence de l'oxygène, et l'un au moins des symboles Y' représentant un groupement époxyfonctionnel. Les polyorganosiloxanes linéaires peuvent être des huiles de viscosité dynamique à 25 C, de l'ordre de 10 à 10 000 mPa.s à 25 C, généralement de l'ordre de 50 à 5 000 mPa.s à 25 C et, plus préférentiellement encore, de 100 à 600 mPa.s à 25 C, ou des gommes présentant une masse moléculaire de l'ordre de 1 000 000. La viscosité dynamique à 25 C, de toutes les silicones considérées dans la présente description peut être mesurée à l'aide d'un viscosimètre BROOKFIELD, selon la norme AFNOR NFT 76 102 de février 1972. The compound may also be chosen from silazanes, that is to say the products of formula (R) 3 Si-NH-Si (R) 3, the radicals R being identical or different, representing carbon groups. The silazanes may be chosen from diphenyldisilazanes, that is to say the products of formula (D (R) 2 Si-NH-Si (R) 2 (D, the radicals R being more particularly alkyl radicals. example, 1,3 diphenyl 1,1,3,3, disilazane may be mentioned

Finally, the compound may be chosen from epoxyfunctionalized polyorganosiloxanes. These are products of the silicone type consisting of units of formula <B> (I) </ B> and terminated by units of formula <B> (11) </ B> represented below

in which the symbols R 1 are the same or different and represent a linear or branched alkyl radical containing 1 to 8 carbon atoms, the alkyl radicals being preferably methyl, ethyl, propyl, and octyl, a cycloalkyl radical containing between 5 and 8 carbon atoms. cyclic carbon, optionally substituted, an aryl radical containing from 6 to 12 carbon atoms which may be substituted, preferably phenyl or dichlorophenyl, an aralkyl moiety having an alkyl moiety containing from 5 to 14 carbon atoms and an aryl moiety containing from 6 to 12 carbon atoms, optionally substituted on the aryl part by halogens, alkyls and / or alkoxyls containing 1 to 3 carbon atoms, the symbols Y 'are similar or different and represent the group R1, and / or an epoxyfunctional group connected to the silicon of the polyorganosiloxane via a divalent radical containing from 2 to 20 carbon atoms e and which may contain at least one heteroatom, preferably oxygen, and at least one of the symbols Y 'representing an epoxyfunctional group. The linear polyorganosiloxanes may be oils with a dynamic viscosity at 25 ° C., of the order of 10 to 10,000 mPa.s at 25 ° C., generally of the order of 50 to 5,000 mPa.s at 25 ° C., and more preferably still, from 100 to 600 mPa.s at 25 ° C., or gums having a molecular weight of the order of 1,000,000. The dynamic viscosity at 25 ° C. of all the silicones considered in the present description can be measured at 1 ° C. using a BROOKFIELD viscometer, according to the AFNOR NFT 76 102 standard of February 1972.

Selon une variante particulière, les radicaux R1, semblables ou différents, représentent un radical alkyle linéaire ou ramifié contenant de 1 à 8 atomes de carbone. On peut citer plus particulièrement les produits de formule (Me)3Si--(-(Si(Me)20)x - (Si(Me)Y'O)Y-Si(Me)3 dans laquelle Y' représente

et la somme x+y peut être notamment comprise entre 8 et 25. La valeur de y peut varier dans une large gamme, de préférence y est égal ou supérieur à 2, y pouvant même atteindre la valeur de 25. As examples of divalent radicals linking an organofunctional group of the epoxy type, mention may be made of those included in the following formulas

According to one particular variant, the radicals R 1, which are similar or different, represent a linear or branched alkyl radical containing from 1 to 8 carbon atoms. Mention may more particularly be made of the products of formula (Me) 3 Si - (- (Si (Me) 20) x - (Si (Me) Y 'O) Y-Si (Me) 3 in which Y' represents

and the sum x + y can be in particular between 8 and 25. The value of y can vary over a wide range, preferably y is equal to or greater than 2, y can even reach the value of 25.

In the case of compounds of the silicone type with an epoxy functional group, it may be thought that it is the epoxy function that reacts with the OH groups of the coating layer of the support to allow grafting or adsorption.

The compositions of the invention are generally in the form of a powder consisting of particles having an average size of at most 5 nm, more particularly at most 2 nm, even more particularly less than 1.5 nm. particle size were obtained using the laser diffraction technique using a CILAS granulometer.

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

The method comprises a first step in which the coated support is brought into contact with at least one abovementioned compound. This contacting allows a condensation reaction of the compound on the support, in particular by reaction between the support-OH bonds and the OH, NH 2 or NH, OR, or epoxy groups of the various compounds.

An amount of compound is usually used which is between 0.5% and 5% and preferably between 0.5% and 2% by weight based on the coated carrier.

The contacting is preferably in a solvent medium of organic type. Suitable solvents include aromatic solvents, for example xylene.

When operating in a solvent medium concentrated in support, the contacting is preferably with shear stirring or with grinding to avoid aggregation of the support.

According to a preferred variant, the condensation reaction is carried out in the presence of a base which acts as a catalyst. More particularly, a base selected from amines, especially amino alcohols, is used. As an example, triethanolamine may be mentioned.

This base is used in an amount sufficient to render the reaction medium basic. The amount of base can thus be between 0.05 and 0.2% by weight relative to the coated support.

At the end of the reaction, the resulting composition is separated from the reaction medium by any suitable means.

The invention also relates to colored pigments consisting of or comprising at least one composition of the type which has just been described above. The sulphide-based compositions or the pigments according to the invention have a very good coloring power and a very good hiding power and, therefore, are perfectly suitable for coloring many materials, such as plastics, paints and others.

Thus, and even more specifically, they can be used in the coloring of plastics which may be of the thermoplastic or thermosetting type. As thermoplastic resins that can be colored according to the invention, mention may be made, purely by way of illustration, of polyvinyl chloride, polyvinyl alcohol, polystyrene, styrene-butadiene, styrene-acrylonitrile and acrylonitrile-butadiene-styrene copolymers. (ABS), acrylic polymers including polymethyl methacrylate, polyolefins such as polyethylene, polypropylene, polybutene, polymethylpentene, cellulose derivatives such as for example cellulose acetate, cellulose acetate butyrate, ethylcellulose, polyamides including polyamide 6-6.

As regards the thermosetting resins for which the compositions or pigments according to the invention are also suitable, mention may be made, for example, of phenoplasts, aminoplasts, in particular urea-formaldehyde, melamine-formaldehyde copolymers, epoxy resins and thermosetting polyesters.

The compositions or pigments of the invention can also be used in special polymers such as fluorinated polymers, in particular polytetrafluoroethylene (PTFE), polycarbonates, silicone elastomers and polyimides.

In this specific application for coloring plastics, it is possible to use the compositions or pigments of the invention directly in the form of powders. They can also preferably be used in a pre-dispersed form, for example premixed with a part of the resin, in the form of a paste concentrate or a liquid, which makes it possible to introduce them to any stage of the manufacture of the resin.

Thus, the compositions or pigments according to the invention can be incorporated into plastics such as those mentioned above in a proportion by weight ranging generally from 0.01 to 5% (referred to the final product) or from 40 to 70% by weight. % in the case of a concentrate.

The compositions or pigments according to the invention are also likely to be suitable for applications in the rubber industry, in particular in floor coatings, in the paper and printing ink industry, in cosmetic products, in glazes and for many other uses such as, for example, and not limited to laminate coatings, in particular for kitchens and other worktops, ceramics. The compositions or pigments of the invention can be particularly used in the field of paints.

In the present description, the term "paint" is used generically. II denotes any coating of polymeric nature deposited on a substrate and more particularly the actual paints (aqueous paints, solvent paints, powder paints), varnishes, stains and plastic resins. It is possible to cite the paints comprising the following resins: alkyd resins, the most common of which is called glycerophthalic acid; resins modified with long or short oil; acrylic resins derived from esters of acrylic acid (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 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 compositions or the pigments are used in a proportion of 5 to 30% by weight of the paint and 0.1 to 5% by weight of the glaze.

The paints are preferably paints used in the household and industrial sector especially the building and the car industry. The most common substrates are wood; metals and their alloys such as steel, stainless steel, aluminum, copper, iron; plastics and mineral glasses; cements, plaster and fiber cement.

The compositions or pigments of the invention are particularly interesting for paints for prepainted sheet metal for stamping (of the so-called "coi-coating" type). These are industrial paints used to paint generally metal panels that will be stamped after application of the paint. Industrially, these paints are applied in a continuous process by spraying, drying and then firing at high temperature for very short periods of time. This kind of paint is therefore requested for good flexibility as well as good adhesion, folding tests are carried out for this purpose. These paints must also crosslink very quickly, so systems with catalyst are used.

These paints must also have good external resistance and the dispersion of the pigments must be optimized. Indeed the deposited paint thicknesses can be very low, of the order of about ten microns for example.

The invention thus relates to paints, especially of the above type, comprising a composition or a pigment as described above.

Examples will now be given. EXAMPLE 1 This example relates to the preparation of compositions or pigments according to the invention.

Starting from a rare earth sesquisulphide pigment of the type described in particular in Example 2 of the European patent application EP-A-620254. It is a cerium sesquisulphide Ce2S3 doped with sodium in a Na / Ce molar ratio of 0.2 and coated with a silica layer in a SiO21Ce2S3 mass ratio of 4.6%. This pigment constitutes the comparative product 1.

A suspension of the aforementioned pigment at 55% solids content in xylene is prepared using a disperser equipped with a deflocculating blade at 900 rpm. Triethanolamine is added, making the basic medium 0.1% with respect to the pigment. The compound to be grafted is then incorporated at a rate of 1% relative to the pigment. Finally, the mixture is milled for 20 minutes at 4000 rpm. After grinding, the solvent phase is evaporated to obtain a powder.

Thus 7 pigments are prepared by grafting the compounds given below.

       To verify that the compound has been grafted, a dispersion test is carried out in the water of the dried pigment (measurement of compatibility of the pigment in polar solvents) and a measurement of the contact angle of a drop of water. water on the dried pigment.

Table 2 below gives the results obtained.

Table <SEP> 2
<tb> Pigment <SEP> angle <SEP> of <SEP> test <SEP> of <SEP> dispersion <SEP> in <SEP> water
<tb> wetting <SEP> with
<tb> water
<tb> 2 <SEP> 135 <SEP> Flotation
<tb> 3 <SEP> 140 <SEP> Flotation
<tb> 4 <SEP> 127 <SEP> Flotation
<tb> 5 <SEP> 150 <SEP> Flotation
<tb> 7 <SEP> 129 <SEP> Flotation
<tb> 8 <SEP> 150 <SEP> Flotation
<tb><U> 1 <SEP> Comparative <SEP> 0 <SEP> Dispersion </ U> The treated pigments have a hydrophobic behavior; they are no longer dispersed in water and the contact angles with water are greater than 90. The results are not given for the product 6 because, in this case, the test is not relevant for establishing the grafting, the molecule used for the grafting is indeed not sufficiently hydrophobic. The following examples will show indirectly for this product that the molecule used has actually been grafted onto the pigment. EXAMPLE 2 This example shows the properties of the pigments of the invention in their application in painting and in a formulation of the polyester-melamine type.

<U> Preparation of the grinding base </ U> The grinding base is prepared from the following constituents URALAC SN800 (polyester resin) 31.64 g CYMEL 303 (melamine crosslinking agent) 20.87 g BYK 354 (agent 2.7 g SOLVESSO 150 (75%) DOWANOL PNB (25%) (solvents) 16.98 g pigment 27.74 g 120 g of glass beads 1 mm in diameter are added. The mixture is ground using a disperser equipped with a Teflon disk for 20 minutes at 7000 rpm. After grinding, the crushed material is recovered by filtering on a 100 micron fabric.

<U> Paint preparation </ U> The paint is prepared from the grinding base obtained previously with the following constituents grinding base 54.08 g URALAC SN800 (polyester resin) 89.06 g SOLVESS0150 (75%) DOWANOL PNB (25%) (solvents) 6.51 g CYCAT 4040 (paratoluene sulfonic acid catalyst PTSA) 1 g <U> Drying conditions: </ U> The tests include an air drying phase of one hour (time required for solvent evaporation). The crosslinking conditions are a temperature of 140 ° C. and a duration of twenty minutes. For the tests of evaluation of the thermal resistance, a sweep in temperature was carried out of 200 C to 300 C for times of 2 minutes.

The various properties obtained for the paint comprising pigments according to the invention or according to the prior art are given below.

<U> Colorimetry </ U> Measurement conditions Colorimetric measurements are performed according to ISO 7724 using a spectrocolor meter DATACOLOR DC3890.

The measurement conditions are as follows: - specular excluded (only the backscattered intensity is measured) - the ultraviolet is 100% filtered - the results are expressed under the illuminant / observer torque C / 10 The measurements were carried out on contrast cards, the paint being applied at 150 wet microns. The results are given in Table 3 below.

Table <SEP> 3
<tb><U> 30 'DRYING <SEP> AIR, <SEP>20'140'> C </ U>
<tb><U> COLORIMETRY <SEP> LENETA </ U><SEP> BOTTOM <SEP> WHITE <SEP> BOTTOM <SEP> BLACK
<tb> Pepper <SEP> L * <SEP> a * <SEP> b * <SEP> L * <SEP> a * <SEP> b *
<tb> 1 <SEP><U> comparative </ U><SEP> 42.97 <SEP> 56.41 <SEP> 58.01 <SEP> 38.59 <SE> 47.83 <SEP> 51, 38
<tb> 5 <SEP> 42.81 <SEP> 56.21 <SEP> 58.01 <SEP> 38.54 <SE> 47.62 <SEP> 51.32
<tb> 4 <SEP> 42.52 <SEP> 56.58 <SEP> 57.3 <SEP> 36.76 <SEP> 45.26 <SEP> 47.97
<tb> 6 <SEP> 42.93 <SEP> 56.15 <SEP> 57.37 <SEP> 38.68 <SEP> 48.04 <SEP> 51.79
<tb> 2 <SEP> 42.78 <SEP> 55.87 <SE> 57.72 <SEP> 39.51 <SE> 49.17 <SEP> 52.81
<tb> 3 <SEP> 42.87 <SEP> 55.98 <SEP> 56.7 <SEP> 38.17 <SEP> 46.32 <SEP> 48.34
<tb> 7 <SEP> 42.71 <SEP> 56.49 <SEP> 58.37 <SEP> 37.74 <SEP> 46.84 <SEP> 50.13
<tb><U> 8 <SEP> 43.06 <SEP> 56.63 <SEP> 58.18 <SEP> 38 <SEP> 46.79 <SE> 50.4 </ U> We can see from the Table 3 that the color of the paints incorporating pigments of the invention undergoes virtually no variation.

<U> Gloss </ U> Measuring conditions The gloss is evaluated according to NFT 30-064 and DIN 6753 using a gloss meter (MICROGLOSS BYK GARDNER). Depending on the surface condition of the paint to be tested, we select the angle that is the most resolutive to differentiate the samples; measurements were made at an angle of 20 and 60. The paints are applied to a glass plate, the paints are applied to the filmstrip to a thickness of 150 microns.

The results are given in Table 4 which follows.

Table <SEP> 4
<tb><U> 30 'DRYING <SEP> AIR, <SEP>20'1400C</U>
<tb><U> BRILLIANCE <SEP> GLASS </ U>
<tb> Chili <SEP> BRILLIANCE <SEP> 20 <SEP> BRILLIANCE <SEP> 60
<tb> 1 <SEP><U> comparative </ U><SEP> 58 <SEP> 89
<tb> 5 <SEP> 71 <SEP> 94
<tb> 4 <SEP> 67 <SEP> 90
<tb> 6 <SEP> 62 <SEP> 90
<tb> 2 <SEP> 70 <SEP> 93
<tb> 3 <SEP> 58 <SEP> 90
<tb><U> 7 </ U><SEP> 61 <SEP> 90
<tb><U> 8 <SEP> 80 <SEP> 97 </ U> There is an improvement in gloss for the paints incorporating the pigments of the invention. <U> Opacity </ U> Opacity is evaluated as follows: The paint to be tested is applied to 50, 100 and 150 micron polyester films in wet condition. For each film, the deposited dry thickness is measured (using a thickness gauge (Fisher)), the color on a white background and the color on a black background. Then for each thickness, we calculate the difference in hue (dE *) between the white background and the black background. The curve of the color difference is plotted against the thickness for each paint. Finally, for each paint, the difference in hue is extrapolated to an identical thickness for each sample. The results are given in Table 5 below.

Table <SEP> 5
<tb><B><U> 30S <SEP> AIR. </ U></U><U><SEP>20'1400C</U>
<tb><B> OPACITY <SEP> PET </ B>
<tb> Pepper <SEP> dE * <SEP> to <SEP> 40 <SEP> m
<tb> 1 <SEP><U> comparative </ U><SEP> 7.6
<tb> 5 <SEP> 8
<tb> 4 <SEP> 6.4
<tb> 6 <SEP> 9.1
<tb> 2 <SEP> 7.3
<tb> 3 <SEP> 7.8
<tb> 7 <SEP> 7.5
<tb> 8 <SEP> 9.2 Product 4 substantially improves opacity and product 2 also has a noticeable effect. Other products have little impact.

<U> Rheology </ U> The rheology of the paints was evaluated using the CARRIMED CSL 100 rotary rheometer by performing a speed gradient sweep from 0 to 100 s-1 and then a 100 s-1 step and a gradient descent. speed from 100 to 0 s-1. These measurements make it possible to evaluate the rheological behavior of the paint and to apprehend the dispersing effect of the additives grafted on the surface of the pigments. The quality of the dispersion is evaluated using two parameters: the viscosity at 100 s-1 and the rheological behavior of the paint (Newtonian or Rheofluidifier). The results are given in Table 6 below.

Table <SEP> 6
<tb> Chili <SEP><U> Behavior </ U><SEP> Viscosity <SEP> to <SEP> 100 <SEP> s- '<SEP> Pa.s
<tb> 1 <SEP><U> comparative </ U><SEP> newtonnian <SEP> 3.8
<tb> 5 <SEP> newtonnien <SEP> 2,7
<tb> 4 <SEP> Rheofluidifier <SEP> 2.7
<tb> 6 <SEP> newtonnien <SEP> 2,5
<tb> 2 <SEP> rheofluidifier <SEP> 2,8
<tb> 3 <SEP> newtonnian <SEP> 2,3
<tb> 7 <SEP> rheofluidifier <SEP> 2
<tb> 8 <SEP> rheofluidifier <SEP><B><U> 2,5 </ U></B></B></b></b></b></b></b></b></b></b></b></b></b></b></b></p> the viscosity of these paints is lower than that comprising an untreated pigment. The pigments of the invention therefore offer greater ease and greater flexibility of use in the application environment than those of the prior art.

<U> Mechanical resistance </ U> Various tests have been carried out to evaluate the flexibility and adhesion of paint films. The adhesion is evaluated by a grid test (standard ISO 2409): the cutter is made a grid of 100 tiles of one millimeter side; an adhesive tape is applied to the grid; remove the tape and evaluate the condition of the grid with a score ranging from 0 (no peeling paint) to 5 (the paint is completely peeled).

The flexibility of the paint film is tested using the following tests - the ERICHSEN stamping test (ISO 1520): a steel ball is applied to a constant stress and speed on the back of the plate. To test, this ball deforms the plate, we note the penetration distance of the ball at which the paint begins to crack.

the deformation test using a cylindro-conical mandrel: the paint plate to be tested is deformed on a cylindro-conical mandrel; we note the radius of curvature of the mandrel to which the paint begins to crack.

The results are given in Tables 7 and 8 below.

Table <SEP> 7
<tb> Results <SEP> in <SEP> adherence
<tb><U> 30 'DRYING <SEP> AIR, <SEP>20'140'> C </ U>
<tb><U> PLATE <SEP> AL36 </ U>
<tb> Chili <SEP> Adherence
<tb> 1 <SEP><U> comparative </ U><SEP> 0
<tb> 5 <SEP> 0
<tb> 4 <SEP> 0
<tb> 6 <SEP> 0
<tb> 2 <SEP> 0
<tb> 3 <SEP> 0
<tb> 7 <SEP> 0
<tb><U> 8 <SEP> 0 </ U>
<tb> Table <SEP> 8
<tb> Results <SEP> in <SEP> flexibility
<tb><U> 30 'DRYING <SEP> AIR, <SEP>20'140"C</U>
<tb><U> PLATE <SEP> AL36 </ U>
<tb> Pigment <SEP> Fits <SEP> Erichsen <SEP> Cylindrical Chuck <SEP>
<tb> v = 5.8mmlmin)
<tb> 1 <SEP><U> comparative </ U><SEP> 6.1
<tb> 5 <SEP> 6.1
<tb> 4 <SEP> 5.2
<tb> 6 <SEP> 6.1
<tb> 2 <SEP> 6.2
<tb> 3 <SEP> 6
<tb> 7 <SEP> 6.3
<tb> 8 <SEP> 6.4 * in all cases no cracking of the paint was observed using the smallest radius of curvature of the mandrel.

The presence of grafted compounds on the pigments of the invention does not alter the flexibility of the paint film or its adhesion. It may therefore be thought that the grafted compounds have remained on the surface of the pigment and that there has been no migration to the interfaces of the film, otherwise the values given above would be bad.

<U> Resistance to acids: </ U> The resistance to acids is evaluated on the dry paint is deposited a drop of 90% sulfuric acid in water on the paint film to be tested. The color variations are measured every minute using a colorimeter equipped with automatic measurement acquisition and under the measurement conditions given above in the paragraph colorimetry. The results are expressed by giving the initial rate at which the hue varies (dE * Imin). The results are given in Table 9 which follows.

Table <SEP> 9
<tb> Pepper <SEP> dE * Imin
<tb> 1 <SEP><U> comparative </ U><SEP> 0.37
<tb> 5 <SEP><B><U> 0.26 </ U></U>
<tb> 4 <SEP><B><U> 0.28 </ U></B>
<tb> 6 <SEP> 0.25
<tb> 2 <SEP> 0.31
<tb> 3 <SEP> 0.51
<tb> 7 <SEP> 0.28
<tb> 8 <SEP><B><U> 0.33 </ U></B> The pigments according to the invention have a pronounced protective effect. Regarding the product 3, it also has certain advantages for other criteria such as rhelogy or thermal resistance.

<U> Thermal resistance of paints </ U> Coil-coating paints have relatively high firing temperatures. It is therefore necessary to evaluate the thermal resistance of the pigments. Indeed, under the action of heat, the pigment can oxidize and pass from the sulfide form to the rare earth sulfate form. For this, the paints are crosslinked at different temperatures (from 200 to 280 ° C.) for a period of two minutes. The gloss is measured for each painting. The cross-linked samples at 200 ° C. will be used as reference.

The results of gloss monitoring are given in Table 10 which follows and in which is indicated the variation of gloss 0 between 200 ° C. and 280 ° C.

Table <SEP> 10
<tb><U> PLATE <SEP> AL36. <SEP> HELD <SEP> THERMAL <SEP> DRY <SEP> AIR <SEP> 30 ', <SEP>2'</U>
<tb> OVEN <SEP> SU <U> IVI <SEP> BRILLIANCE <SEP> 20 </ U>
<tb><U> Pigment </ U><SEP> o
<tb> 1 <SEP><U> comparative </ U><SEP> 22%
<tb> 5 <SEP> 16%
<tb> 4 <SEP> 3%
<tb> 6 <SEP> 20%
<tb> 2 <SEP> 12%
<tb> 3 <SEP> 13%
<tb> 7 <SEP> 11%
<tb> 8 <SEP> 18% In terms of variation in gloss, there is a clear improvement for the paints incorporating the pigments of the invention.

<U> Aging </ U> The aging test is of the QUVA type. It is done under the following conditions. Irradiation conditions: UVA lamp with a peak centered at 340 nm.

Chamber temperature: 60 C.

Operating cycle: 4 hours of dry phase irradiation at a temperature of 60 ° C and then 4 hours of condensation in the dark at a temperature of 60 ° C.

Moisture is provided by heating a water tray at the bottom of the unit (so steam is produced) and this water condenses on the paint plates.

The half-life of gloss is measured (this is the time required for the initial gloss of the paint to drop by half).

There is also time for the paint to have a dye difference (dE *) of 10. Table 11 below summarizes the aging results.

Table <SEP> 11
<tb> pigment <SEP> 1I2 <SEP> life <SEP> of <SEP> t <SEP> for
<tb> brightness <SEP> dE * = 10
<tb> 5 <SEP> 20 <SEP> 22
<tb> 4 <SEP> 20 <SEP> 26
<tb> 6 <SEP> 16 <SEP> 19
<tb> 2 <SEP> 16 <SEP> 19
<tb> 3 <SEP> 22 <SEP> 27
<tb> 7 <SEP> 25 <SEP> 49
<tb> 8 <SEP> 18 <SEP> 21
<tb> 1 <SEP><U> comparative </ U><SEP> 18 <SEP> 20 Times are expressed in 8-hour cycles.

Products 3, 4, 5 and 7 significantly improve the aging resistance of the paint.

EXAMPLE 3 This example describes an application of a pigment of the invention in a plastic. Rotary cube is mixed with polyamide 12 granules (Rilsan AMN D natural from Atochem company not protected against UV) with the pigment (1% by weight) (either the comparative pigment 1 or the pigment 7) and an agent ". fixative butyl stearate <B> (0.05%). </ B>

The mixture was extruded on a 30 mm diameter twin-screw extruder (ZSK 30 from Werner & Pfleiderer) and then injection molded on Arburg 35T press (350-90 220D allrounder) at 220 ° C to obtain platelets 48 x 40 x 4 mm. These platelets are subjected to an accelerated aging test XENOTEST (1S0 4892) under the following conditions <U> Irradiation conditions </ U>: xenon arc lamp with suprax filters simulating a solar lighting about a hundred times more intense, l irradiance is regulated at 65 Wlmz <U> Chamber temperature </ U>: 30 C <U> Operating cycle </ U>: 27 minutes of irradiation in dry phase at t = 30 C then 3 minutes of irradiation in wet phase at t = 30 C. The moisture supply is done by sprinkling directly liquid water on the test plates by means of nozzles.

The difference in hue (dE *) is measured after 2500 hours. We obtain the results given in Table 12 below

Table <SEP> 12
<tb> Pepper <SEP> dE *
<tb> 1 <SEP><U> comparative </ U><SEP> 2,3
<p> 7 <SEP> 1.5 The pigment of the invention clearly improves the aging resistance of the plastic.

In conclusion, it appears from the properties given above that the treatment of the invention leads to pigments on which the abovementioned compounds are well grafted.

In addition, the grafted compounds do not desorb during the formulation and during the drying of the paints. There is no migration of the compounds to the interfaces of the paint film. This point is essential for the adhesion of the paint with its support and the other layers of varnish or paint that can be applied. Indeed, in industrial applications of paint, it is not uncommon for metal parts to be painted with several layers of paint (adhesion primer, primer and varnish). On the contrary, the usual additives or surfactants used to disperse the pigment partially desorb and alter the adhesion of the paint.

The grafting or adsorption of organic compounds has a dual role. It offers a barrier to water and oxygen and a compatibilizing effect with the paint which improves the dispersion of these pigments.

Claims (1)

A composition comprising a support based on a rare earth sulphide which contains at least one alkaline and / or alkaline earth element of which at least part is included in the crystalline lattice of said sulphide. ; a layer at least partly coating said support and based on at least one oxide capable of having surface OH groups; characterized in that it has on its surface groups originating from the deposition on the coated support of at least one compound chosen from water-insoluble fatty alcohols, aliphatic amines which are insoluble in water, and silanes comprising at least an alkoxylated group, silazanes or epoxyfunctionalized polyorganosiloxanes. 2- Composition according to Claim 1, characterized in that the abovementioned compound is chosen from C 8 - C 30 fatty alcohols, more particularly C 8 - C25 - B - 3 - Composition according to claim 1, characterized in that the abovementioned compound is chosen from aliphatic amines whose carbon chain comprises at least 10 carbon atoms, more particularly between 10 and 35 carbon atoms. 4. Composition according to claim 1, characterized in that the abovementioned compound is chosen from silanes comprising a methoxy or ethoxy group. 5- Composition according to one of claims 1 and 4, characterized in that the above compound is selected from silanes comprising a carbon chain of at least 8 carbon atoms. 6. Composition according to one of claims 1, 4 and 5, characterized in that the above compound is selected from silanes comprising an amino group at the end of a carbon chain. 7- Composition according to claim 1, characterized in that the above compound is selected from diphenyldisilazanes. 8- The composition as claimed in claim 1, characterized in that the abovementioned compound is chosen from epoxyfunctionalized polyorganosiloxanes consisting of units of formula (I) and terminated with units of formula (11) represented below in which the R1 symbols are similar. or different and represent a linear or branched alkyl radical containing 1 to 8 carbon atoms, the alkyl radicals being preferably methyl, ethyl, propyl, and octyl, a cycloalkyl radical containing between 5 and 8 cyclic carbon atoms, optionally substituted, a an aryl radical containing from 6 to 12 carbon atoms which may be substituted, preferably phenyl or dichlorophenyl, an aralkyl moiety having an alkyl moiety containing from 5 to 14 carbon atoms and an aryl moiety containing from 6 to 12 carbon atoms, optionally substituted on the aryl part by halogens, alkyls and / or alkoxyls containing 1 to 3 atoms carbon, the symbols Y 'are similar or different and represent the group R1, and / or an epoxyfunctional group, connected to the silicon of the polyorganosiloxane via a divalent radical containing from 2 to 20 carbon atoms and which may contain at least one heteroatom, preferably oxygen, and at least one of the symbols Y 'representing an epoxy functional group. 9- Composition according to claim 8, characterized in that the epoxyfunctional groups are chosen from the following groups       10- Composition according to claim 8 or 9, characterized in that the symbols R1, similar or different, represent a linear or branched alkyl radical containing 1 to 8 carbon atoms. 11. Composition according to one of the preceding claims, characterized in that the rare earth sulphide consists of whole monocrystalline grains of average size of at most 1.5 Nm. 12. Composition according to one of the preceding claims, characterized in that the rare earth sulphide is a sesquisulfide. 13- Composition according to one of the preceding claims, characterized in that the amount of alkaline element and / or alkaline earth is at most 50% of the molar amount of rare earth and in that it is in particular between 5 and 50% of this amount. 14 - Composition according to one of the preceding claims, characterized in that the sulfide has a crystallographic structure of the Th3P4 type. 15. Composition according to one of the preceding claims, characterized in that the alkaline element is lithium, sodium or potassium. 16. Composition according to one of the preceding claims, characterized in that the sulphide is cerium sesquisulphide Ce2S3 y cubic. 17- Composition according to one of the preceding claims, characterized in that the oxide may have surface OH groups is selected from silica, alumina, zirconia, titanium oxide, zircon and oxides rare earths. 18- A process for preparing a composition according to one of the preceding claims, characterized in that it comprises the following steps - the coated support is brought into contact with at least one aforementioned compound whereby a condensation reaction is carried out compound on the support; the resulting composition is separated from the reaction medium. 19- The method of claim 18, characterized in that the condensation reaction is carried out in the presence of a base. 20- The method of claim 19, characterized in that a base is used selected from amines, especially amino-alcohols. 21- Method according to one of claims 18 to 20, characterized in that the contacting of the coated support with at least one said compound in a solvent. 22- colored pigment, characterized in that it consists of, or in that it comprises at least one composition according to one of claims 1 to 17. 23- Compositions of colored material including plastics, rubbers, ceramics , glazes, papers, inks, cosmetics, dyes and laminated coatings, characterized in that they comprise a composition or a colored pigment as defined in any one of claims 1 to 17 and 22. 24- Painting, characterized in that it comprises a composition or a colored pigment as defined in any one of claims 1 to 17 and 22. 25. The paint according to claim 24, characterized in that it comprises at least one resin of the acrylic type or polyester.