FR2758545A1 - Composition, used as pigments in e.g. plastics, ceramics, rubbers - Google Patents

Abstract

Composition comprising a mixture of two sulphides of formula A-S (I) and A<1>-B-S2 (II). In (I) and (II), A = alkaline earth metal; A<1> = alkali metal; and B = rare earth. Also claimed is the preparation by mixing and subjected to calcination under a sulphur containing gas, e.g., CS2. Preferably the composition is of formula (A-S)x(A<1>-B-S2)1-x (III). In (III), x = 0.1-0.95; B = Ce; and A = Ca or Sr. The composition is coated by a peripheral layer of a transparent oxide and/or it contains fluorine atoms.

Description

COMPOSITIONS BASED ON RARE EARTH SULPHIDES. ALKALIN AND
OF ALCALINO EARTH. THEIR METHODS OF PREPARATION AND THEIR
USE AS A COLORING PIGMENT
RHONE-POULENC CHEMISTRY
The present invention relates to compositions based on rare earth, alkali and alkaline earth sulphides, their preparation processes and their use as coloring pigment.

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

Unfortunately, the problem is that most of the inorganic pigments which are suitable for applications such as above and which are actually used today 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, in fact given their deemed very high toxicity. Mention may thus more particularly be made, by way of nonlimiting examples, of the case of red pigments based on cadmium selenide and / or on cadmium sulfoselenide.

Rare earth sulfides are known as possible substituents.

However, there is a need for other substitute pigments to expand the color gamut.

The object of the present invention is to provide new pigments which meet the environmental problem mentioned above and which can complete the range of existing replacement pigments.

For this purpose, the compositions of the invention are characterized in that they comprise a mixture of two sulphides of formula (1):
AS and of formula (2):
A'BS2 in which A represents at least one alkaline earth, A 'at least one alkali and B at least one rare earth.

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

As indicated above, the products of the invention are based on a mixture of two sulphides corresponding to formulas (1) and (2) given above. As regards the respective proportions of these two sulphides, the compositions of the invention can be represented by the following overall formula: (AS) X (A'BS2) 1 X and, in this case, x can be more particularly included between 0.1 and 0.95 and even more particularly between 0.4 and 0.95.

As regards the chemical elements included in the composition of the products of the invention, the term rare earth is understood here and for the remainder of the description, the elements of the group consisting of yttrium and the elements of the periodic table of number atomic included between 57 and 71.

For the sulphides of formula (1), the alkaline earth metal can be more particularly calcium or strontium. For the sulphides of formula (2), the rare earth can more particularly be cerium or lanthanum.

According to a particular embodiment in the case where the alkaline earth metal is calcium or strontium, where the alkali is sodium or potassium and where x is between 0.4 and 0.95, the compositions of l The invention consists of a solid solution of a sulphide of formula (2) in a sulphide of formula (1).

The compositions of the invention exhibit colors which can vary from yellow to dark red. More particularly, in the case where the alkaline is sodium,
Alkaline earth metal strontium or calcium and rare earth cerium, this color varies as a function of the sulphide content of formula (2) in a range from yellow when x as defined above is equal to 0.95 to dark red when x is 0.4.

The compositions of the invention can be prepared by a process using a solid-gas reaction. Thus, compounds comprising the elements A, A 'and B. are mixed. This mixture can be homogenized by grinding. As suitable compounds, mention may be made of rare earth oxides, alkali carbonates and alkaline earth carbonates. The mixture is then subjected to calcination under a gas containing sulfur. As gas, carbon disulphide CS2 can be used in particular. The calcination is carried out at a temperature and for a sufficient time to obtain the reaction. It is possible to carry out several successive calcinations between which the mixture is cooled and it is ground again. The calcination temperature can vary between 600 and 1200 C. The duration can vary between 15 minutes and 5 hours, for example.

Particular variants of the sulphide-based compositions of the invention will now be described.

According to a first variant, the composition comprises a layer based on at least one transparent oxide, deposited on its surface or its periphery.

For this variant, reference may be made with regard to the transparent oxide and the preparation process to French patent application FR-A-2703999 in the name of
Applicant whose teaching is incorporated herein.

According to this variant, the product of the invention comprises a composition, of the type described above, which forms a core and, coating this core, a peripheral layer of transparent oxide.

Of course, some variations around this structure are possible. In particular, the peripheral layer coating the composition may not be perfectly continuous or homogeneous. However, preferably, the products according to the invention consist of a uniform coating layer of controlled thickness of transparent oxide, and this so as not to alter the original color of the composition before coating.

By transparent oxide is meant here an oxide which, once deposited on the composition in the form of a more or less thin film, absorbs little or no light rays in the visible range, and this of so as not to mask the original intrinsic color of the composition. Further, it should be noted that the term oxide, which is used for convenience for this part of the present specification, is to be understood as covering also oxides of the hydrate type.

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

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 of zirconium ZrSiO4 (zircon) and rare earth oxides. According to a preferred embodiment of the present invention, the coating layer is based on silica. Even more advantageously, this layer is essentially, and preferably only, composed of silica.

A process for preparing compositions with a coating layer can consist in bringing together the composition as it was obtained after calcination and a precursor of the oxide forming a layer, and in precipitating this oxide. The processes for precipitating the oxides and the precursors to be used are described in particular in FR-A2703999.

In the case of silica, mention may be made of the preparation of silica by hydrolysis of an alkyl-silicate, forming a reaction medium by mixing water, alcohol, the composition which is then suspended, and optionally of a base, and then introducing the alkyl-silicate, or even a preparation by reaction of the composition, of a silicate, of the alkali silicate type, and of an acid.

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

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

As regards titanium oxide1, it can be precipitated by introducing into an aqueous suspension of the composition according to the invention a titanium salt on the one hand such as TiC4, TiOCI2 or TiOSO4, and a base on the other hand. . It is also possible to operate, for example, by hydrolysis of an alkyl titanate or precipitation of a titanium sol.

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

According to another variant, the composition based on sulphides of the invention may contain fluorine atoms.

For this variant, as regards the arrangement of the fluorine atoms and the preparation process, reference may be made to French patent application FR-A 2706476 in the name of the Applicant, the teaching of which is incorporated here.

The fluorinated compositions can preferably exhibit at least one of the following characteristics
- the fluorine atoms are distributed according to a concentration gradient decreasing from the surface to the heart of the compositions.

- the fluorine atoms are mainly distributed at the outer periphery of the compositions. By external periphery is meant here a thickness of material measured from the surface of the particle, of the order of a few hundred Angstroms. The term “predominantly” also means that more than 50% of the fluorine atoms present in the composition are found in said outer periphery.

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

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

The process for preparing the products according to this variant consists in contacting and reacting with a fluorinating agent, the composition as it was obtained after calcination under a gas containing sulfur. This fluorination can be carried out according to any technique known per se.

In particular, the fluorinating agent can be liquid, solid or gas. Preferably, the operation is carried out under treatment conditions where the fluorinating agent is liquid or gaseous.

As examples of fluorinating agents suitable for carrying out this treatment, there may be mentioned more particularly fluorine F2, halogen fluorides, ammonium fluoride, rare gas fluorides, fluoride. nitrogen NF3, boron fluoride BF3, tetrafluoromethane, Hydrofluoric acid HF.

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

The reaction conditions are preferably chosen such that said treatment induces fluorination only on the surface of the composition (mild conditions).

In this regard, carrying out fluorination to the core of the composition does not provide substantially improved results compared to essentially surface fluorination. In a practical way, one can monitor and control experimentally 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 gradual introduction of fluorine) .

A third variant of the products of the invention relates to the fluorinated products of the type which has just been described but which are also encapsulated by a layer of transparent oxides.

In this case, a composite product is thus obtained consisting more precisely on the one hand of the fluorinated composition as obtained and defined above and, on the other hand, of a layer based on at least one transparent oxide deposited at the surface of said composition and coating the latter.

Everything that has been said above with regard to the process for obtaining such a layer applies of course here.

Finally, it is possible to envisage a last variant in which the product comprising a layer based on at least one transparent oxide deposited on its surface is also fluorinated. This product can be obtained by contacting the composition, as obtained after calcination under a gas containing sulfur, and a precursor of the transparent oxide, then by precipitating this oxide. Secondly, the product thus obtained is subjected to a fluorination treatment of the type described above.

The sulphide-based compositions of the invention can very particularly be used as coloring pigments.

They indeed have good coloring power and good covering power and, therefore, are suitable for coloring many materials, such as plastics, paints and others. The compositions of the invention exhibit good thermal stability up to 300 ° C. in air.

Thus, and more precisely still, they can be used in the coloring of plastics which can be of the thermoplastic or thermosetting type.

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, acrylonitrilebutadiene-styrene (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, ethyl cellulose, polyamides including polyamide 6-6.

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

The sulphide-based compositions of the invention can also be used in special polymers such as fluoropolymers, in particular polytetrafluoroethylene (P.T.F.E.), polycarbonates, silicone elastomers and polyimides.

In this specific application for the coloring of plastics, the sulphide-based compositions of the invention can be used directly in the form of powders. It is also possible, preferably, to use them in a pr dispersed form, for example as a premix with a part of the resin, in the form of a paste concentrate or of a liquid, which allows them to be introduced at any rate. what stage of resin manufacturing.

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

The sulphide-based compositions 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, 2-ethylhexyl or butyl acrylate; vinyl resins such as, for example, polyvinyl acetate, polyvinyl chloride, butyralpolyvinyl, formalpolyvinyl, and copolymers of vinyl chloride and vinyl acetate or vinylidene chloride; the most frequently modified aminoplast or phenolic resins; polyester resins; polyurethane resins; epoxy resins; silicone resins.

Generally, the sulphide-based compositions 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.

Finally, the sulphide-based compositions according to the invention are also likely to be suitable for applications in the rubber industry, in particular in floor coverings, in the paper industry and printing inks, in the field. cosmetics, as well as for many other uses such as, for example, and without limitation, dyes, in leathers for finishing the latter and laminate coverings 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 inorganic binder.

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

The term “hydraulic binders” is understood to mean substances having the property of setting and hardening after addition of water, forming hydrates which are insoluble in water. The products of the invention apply most particularly to the coloring of cements and of course of concretes made from these cements by adding water, sand and / or gravel thereto.

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 both. Mention may be made, by way of example, 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. By way of example, PORTLAND cements can be given and, in this type of cements, fast or very fast setting Portland cements, white cements, those resistant to sulphates as well as those comprising blast furnace slags and / or fly ash and / or meta-kaolin.

Mention may also be made of cements based on hemihydrate and calcium sulphate as well as magnesian cements known as Sorel cements.

The compositions of the invention also apply to the coloring of aerial binders, that is to say binders which harden in the open air by the action of CO 2, of the calcium or magnesium oxide or hydroxide type.

The compositions of the invention are finally applied to the coloring of plaster and binders of the anhydrous or partially hydrated calcium sulfate type (CaSO4 and CaSO4, 1 / 2H20).

Finally, the invention relates to compositions of colored matter in particular of the plastics type, paints1 stains, rubbers, ceramics, glazes, papers, inks, cosmetics, dyes, leathers, laminated coatings or compositions based on or obtained from less one inorganic binder, which comprise a composition based on sulphides of the type described above.

Examples will now be given.

In these examples, the chromatic coordinates L *, a * and b * are given in the CIE 1976 system (L *, a * and b *) as defined by the Commission Internationale d'Eclairage and listed in the Collection of French Standards (AFNOR), colorimetric color No. X08-12 (1983). They are determined with regard to measurements made on products and plastics by means of a colorimeter marketed by the Company Pacific Scientific. The nature of the illuminant is D65 The observation surface is a circular pellet with a surface area of 12.5 cm 2. The observation conditions correspond to a vision at an aperture angle of 10. In the measurements given, the specular component is excluded.

The products are prepared as follows.

The reaction mixture consists of rare earth oxide (CeO2), alkali carbonate (A'2CO3, xH2O, A '= Li, K, or Na) and alkaline earth carbonate (AC03, A =
Ca or Sr). It is homogenized by grinding before calcination.

The reaction mixture is then placed in a quartz boat itself introduced into a tubular quartz furnace (indirect heating). A first calcination is carried out at 700 ° C. for three hours under flushing with nitrogen and CS2.

After cooling, the charge is ground to be homogenized, then recalcined, still under nitrogen and CS2 scavenging, at 700 ° C. for thirty minutes, then at 11000 ° C. for one hour. The final color of the pigment depends on the proportions of CaS and of NaCeS2 in the initial reagent The final size of the pigment is between 5 and 1OClm.

The solutions obtained here are solid solutions; their composition is expressed as follows: (AS) y (A'CeS2) 1 y.

EXAMPLE 1 (CaS) 0.95 (NaCeS2) 0105
The measured color parameters are:
- L * = 75.0 - a * = 9.6
- b * = 64.1
EXAMPLE 2 (CaS) 0.9 (NaCeS2) 0.1
The color parameters measured are: - L * = 61.6 - a * = 35.0 - b * = 67.5
EXAMPLE 3 (CaS) 0.6 (NaCeS2) 0.4
The color parameters measured are: - L * = 47.0 - a * = 42.7 - b * = 54.0
EXAMPLE 4 (CaS) 0.4 (NaCeS2) 0.6
The color parameters measured are: - L * = 41.6 - a * = 40.8 - b = 33.4
EXAMPLE 5 (SrS) 0.9 (NaCeS2) 0.1
The color parameters measured are: - L * = 78.7 - a * = 6.7 - b * = 63.8
EXAMPLE 6 (SrS) 0.7 (NaCeS2) 0.3
The color parameters measured are: - L * = 58.1 - a * = 35.0 - b * = 68.6

Claims (14)

A'BS2 in which A represents at least one alkaline earth, A 'at least one alkali and B at least one rare earth. AS and of formula (2): CLAIMS 1- Composition characterized in that it comprises a mixture of two sulphides of formula (1); 2- Composition according to claim 1, characterized in that by representing the composition by the overall formula (AS) x (A'BS2) 1.x, the sulphides of formulas (1) and (2) are present in a ratio such that x is between 0.1 and 0.95. 3- Composition according to claim 1 or 2, characterized in that it consists of a solid solution of a sulphide of formula (2) in a sulphide of formula (1). 4- Composition according to one of claims 2 or 3, characterized in that x is between 0.4 and 0.95. 5- Composition according to one of the preceding claims, characterized in that B is cerium. 6- Composition according to one of the preceding claims, characterized in that A is calcium or strontium. 7- Composition according to one of the preceding claims, characterized in that it is coated with a peripheral layer of transparent oxide, more particularly chosen from silicon oxide (silica), aluminum oxide (alumina) , Zirconium oxide (zirconia), Titanium oxide, zirconium silicate ZrSiO4 (zircon) and rare earth oxides. 8- Composition according to one of the preceding claims, characterized in that it contains fluorine atoms, the fluorine atoms being in particular distributed according to a concentration gradient decreasing from the surface to the heart of the composition. 9- A method of preparing a composition according to one of claims 1 to 6, characterized in that mixing compounds comprising elements A, A 'and B and then subjecting the mixture to calcination under a gas containing sulfur. 10- A method according to claim 9 for the preparation of a composition according to claim 7, characterized in that the composition obtained after calcination is brought into contact with a precursor of the layer-forming oxide, and this oxide is precipitated. 11- A method according to claim 9 for the preparation of a composition according to claim 8, characterized in that the composition obtained after the calcination is brought into contact with a fluorinating agent. 12- Use of a composition according to one of claims 1 to 8 as a coloring pigment. 13- Use according to claim 12, characterized in that the composition is used as a pigment in plastics, paints, stains, rubbers, ceramics, glazes, papers, inks, cosmetics, dyes , leathers, laminate coverings and materials based on or obtained from at least one inorganic binder. 14- Compositions of colored matter in particular of the plastics type, paints, stains, rubbers, ceramics, glazes, papers, inks, cosmetic products, dyes, leathers, laminated coatings or compositions based on or obtained from at least one inorganic binder, characterized in that they comprise a composition according to any one of Claims 1 to 8.