MXPA00008826A - Sulphide and oxysulphidepigments - Google Patents

Abstract

The invention concerns rare earth metal sulphide or oxysulphide pigments, and yttrium sulphide or oxysulphide pigments, based on flaky substrates.

Description

PIGMENTS OF SULFIDE AND OXISULPHIDE The present invention relates to sulphide and oxysulfide pigments that are. they roast in substrates in the form of lamellae coated with a sulphide or oxysulfide of a rare earth metal and / or yttrium, and their preparation and use, especially in finishes for automobiles, paints, inks, plastics and cosmetic formulations.

The sulfide pigments of rare earth metals and yttrium sulfide without carriers, and their use in plastics, coating materials and cosmetics, are known from EP 0 203 838 Bl. EP 0 545 746 Bl discloses pigments comprising a composition based on a sesquisul furo of a rare earth or yttrium metal and a coating agent.

In EP 0 620 254 Bl a pigment based on a rare earth metal sulfide or an yttrium sulfide, is used as a vehicle which is coated with a transparent oxide, preferably a metal oxide.

These pigments of sulphides of rare earth metals and yttrium sulfides, although they can be employed with good effect as absorption pigments for numerous REF .: 122207 purposes, can not be considered as pearlescent pigments due to the absence of interfacial capacity and poor brightness.

Therefore, it was the object of the invention to provide sulphides or oxysulfides pigments of rare earth metals and yttrium sulfides or oxysulfides which had good opacity and strong color tones, covering a relatively broad color spectrum, and at the same time time they had the interference properties and brightness of pearl gloss pigments.

. It has now been surprisingly found that, by coating the substrates in the form of lamellae with pigments of sulphides or oxysulfides of rare earth metals (lanthanides) and yttrium, pigments are obtained which have advantageous color properties.

On the sheet-like substrates it is possible to apply sulfide or oxysulfide layers of uniform rare earth and yttrium metals having a high gloss, give the pigment a spray color and possibly generate the interference colors of the thin lamellae.

Therefore, the invention provides sulphide and oxysulfide pigments which are based on substrates in the form of lamellae, characterized in that the substrates are coated with a sulphide or oxysulfide of a rare earth metal and / or yttrium.

The invention further provides a process for preparing the pigments of the invention and for the use of these pigments in formulations such as paints, varnishes, printing inks, plastics and cosmetics.

The substrates are coated with a sulfide of rare earth or yttrium metals having the formula M2S3, wherein M is at least one element selected from the group consisting of the lanthanides of atomic numbers 57 to 71 and yttrium. Preferably, M2S3 is a sesquisul furo of? ~ Ce2S3 or cubic? -La2S3. However, mixtures of sulfides, such as? -Ce2S3 or? -La2S3, or mixed sulfides, such as LaYS3, are also suitable. The coating could additionally consist of oxysulfides of the formula 2S3_xOx (2.5 <x < 0.05).

A suitable foil-form base substrate is any foil-shaped material known to the person skilled in the art, which is stable under the conditions of the coating. Particular mention could be made of natural or synthetic mica (alumina and potassium silicates), kaolin, talc, vermiculite, Ti02, Si02 and A1203 flakes, glass flakes, graphite, metal flakes, bismuth oxychloride, iron oxide in the form of lamella, LCPs (liquid crystal polymer pigments), holographic pigments and other materials in the form of lamellae.

Preference is given to mica, such as, for example, muscovite or phlogopite. However, the lamellar substrate employed may also comprise materials that already have a metal oxide coating, especially mica flakes or Si02 with one or more coatings of, for example, Ti02, Zr02, Sn02, A1203, Si02, ZnO or mixtures of these metal oxides.

Other suitable substrate materials are thin metal flakes, which in some cases. for example, as in the case of Al flakes - they are wrapped by a layer of a low refractive index stabilization compound, such as silica. In addition to Al flakes, other metal flakes used include those of Ag, Ti, Cu / Zn and other metals.

The size of these lamellar substrates is not critical per se, and therefore, it is possible to use particles of the appropriate size for the intended application. In general, the substrate will be employed in particle sizes of about 1 to 200 μm, in particular about 5 to 100 μm. The thickness of the particles is generally about 0.1 to 5 μm, in particular about 0.5 μm.

The initiator materials used as substrates are known and can be prepared by known techniques. Mica particles of the order of the desired size can be obtained by wet or dry milling of. mica followed by classification. Materials coated with metal oxides, especially mica flakes coated with metal oxides, can be obtained commercially - for example, as pearl luster pigment Iriodin® from Merck KgaA, Darmstadt, Germany - or they can be prepared by known techniques. Such techniques are described, for example, in the following patents and patent applications: US 3,087,828, US 3,087,829, DE 19 59 998, DE 20 09 566, DE 22 14 545, DE 22 44 298, DE 23 13 331, DE 25 22 572, DE 31 37 808, DE 31 37 809, DE 31 51 343, DE 31 51 354, DE 31 51 355, DE 32 11 602, DE 32 35 107, WO 93/08237 and EP 0 763 573.

The pigments of the invention are prepared by adding a salt solution of a rare earth metal and / or yttrium- and optionally oxalic acid to an aqueous suspension of a lamellar substrate, the pH of the suspension is optionally kept constant, by the simultaneous addition of a base, within a range that causes the hydrolysis of the added salt, and the pigment thus coated with an oxide or hydrated oxide or oxalate is separated, washed, dried, preferably at '80 - 150 ° C for 10 minutes to 1.5 hours, and calcined, preferably at 400-900 ° C. Finally, the product is calcined in a stream of H2S gas or in a gas stream of CS2 or H2S / CS2 under inert gas for 10 minutes to 2 hours at temperatures of 550 to 1200 ° C, preferably 800 to 1000 ° C, in the course of which the oxalate or oxide of the rare earth metal and / or yttrium is converted to the sulfide or oxysulfide.

It is also possible to carry out the reaction with H2S or CS2 in a fluidized bed reactor (CVD process).

To carry out the CVD variant, it is advisable, as is generally the case for CVD processes, to use a fluidized bed reactor or a tubular furnace. The particles of the substrate to be coated are heated in the reactor, for example with fluidization by means of an inert fluidization gas such as N2 or argon, at the desired reaction temperature (generally from 400 to 900 ° C, preferably from 650 to 850 ° C). The elemental sulfur or H2S and / or CS2 is then introduced from the separate nozzles with the help of the inert streams of the carrier gas (advantageously undercurrent of the fluidizing gas) of the upstream evaporator vessels, the sulfur concentration being it judiciously holds 0.5 to 5% by volume, preferably __ 2% by volume, based on the total amount of gas in the reactor.

In addition to the sulfur-containing compounds, particularly preferred sulfur donors include hydrogen sulfide and elemental sulfur.

If elemental sulfur is used, the procedure adopted is to judiciously make finely ground inert sulfur powder for about 1 to 4 h and then heat it in the absence of oxygen to the reaction temperature, generally 400-1200 ° C, preferably 400-900 ° C and, in particular, 600-850 ° C.

Depositing the layers of rare earth metal oxide or hydrous oxide or yttrium oxide or hydrous oxide layers in the presence of one or more coating agents *, selected, for example, from the group of the alkali metal and / or alkali metals, on the substrates in the form of lamellae, it is possible to produce sulphide layers of strongly colored, smooth, defined and stable rare earth metals or layers of yttrium sulfide, respectively. The coating agent is in the form of an inclusion in the crystal structure of the sulfide layer M2S3 or the oxysulfide layer M2S3_xOx. The coating agent may be selected only or in mixtures of the alkali metal and / or alkali metal salts; preferably the use of sodium or potassium is given. In the course of the coating, the substrates in the form of lamellae with the oxide or hydrous oxide layer, the coating agent is added in the solid form or in aqueous solution in amounts, based on the substrate, of 0.02 to 2.0% by weight , preferably from 0.05 to 0.2% by weight. The proportion of the coating agent in the sulfide layer or the oxysulfide layer is 0.01 to 1.0% by weight, preferably 0.05 to 0.5% by weight.

Particular preference is given to substrates in the form of lamellae having a cerium sulphide layer or an oxysulfide layer and coating with sodium.

Depending on the desired effect, the sulfide layer or the oxysulfide layer of the rare earth metals or yttrium may have thicknesses up to about 400 nm, preferably from 10 to 300 nm. In these common layers they reach contents of sulphides of rare earth metals or of yttrium sulphides or of the corresponding oxysulfides which, based on the substrate, are from approximately 1 to 400% by weight, in particular from 5 to 300% by weight. weight. Depending on the thickness of the layer of the sulphide or oxysulfide layer, interference colors are obtained which, with the growth of the thickness of the layer, go from silver through gold, red, violet and blue, to green and, finally, to interference colors of higher order.

With pigments containing not only a layer of yttrium sulphide or rare earth metal sulfide or a corresponding oxysulfide layer, but also other layers (preferably 3 to 7 layers) of high and low refractive index materials (preferably oxides) ) and, optionally, semitransparent metals (multilayer pigments), it is possible to obtain very strong angle-dependent color effects (color reduction, goniochromaticity).

It is also possible to subject the finished pigment to an operation after coating or after the treatment which also improves light stability, stability of time and chemical stability or facilitates handling of the pigment, especially its incorporation into various media. Examples of subsequent coatings and subsequent treatments are the processes described in DE-C 22 15 191, DE-A 31 51 354, DE-A 32 35 017 or DE-A 33 34 598.

The additionally applied substrates form only about 0.1 to 5% by weight, preferably about 0.5 to 3% by weight of the overall pigment.

The pigments of the invention are a major enrichment of the art. The color of the powder that goes from orange to red, and the interference color, which can be generated as desired, result in extremely interesting effects that can be obtained for numerous applications; in particular, in the case of substrates that already have an interference color, this can be intensified and varied by means of the sulfide layer or the oxysulfide layer. The application areas arise in cosmetics, where the pigments of the invention can be used, for example, in varnish for nails, in make-up, gels, powders, ointments, emulsions, lipsticks and other formulations, in general concentrations of 0.1 to 80% by weight, and in industry, for example for pigmentation of paints, other coating materials, printing inks or plastics.

The plastics comprising the pigments of the invention in amounts of 0.1 to 10% by weight, preferably 0.1 to 5% by weight, are exceptionally suitable for laser marking using, for example, a C02 or Nd-YAG laser. The marks obtained are remarkable for their high contrast and definition.

The following examples are intended to illustrate the invention without limiting it: And emplos Ei emplo 1 100 g of mica of particle size of 10.-60 μm are suspended in 2 1 of water. At a pH of 5.5 and at 60 ° C, a solution of 26 g of Ce (S04) -4H20 in 420 ml of dilute sulfuric acid is measured, the pH is kept constant by the simultaneous dropwise addition of sodium hydroxide solution to 25%. The mixture is stirred for 0.5 h and the product is separated, washed with water, dried at 80 ° C for 0.5 h, first calcined at 500 ° C in an argon stream for 0.5 h and finally at 950 ° C in a stream. of H2S / argon (10 1 / h of H2S) for 1 h.

The resulting pigment has an intense orange color and a high gloss.

Example 2 By the same procedure as in Example 1, 100 g of Si02 flakes of particle size from 5 to 40 μm are coated with cerium sulphide. With regard to the pigment described in Example 1, the resulting pigment has an even more intense orange color and increased brightness. 3 Using the procedure of Example 1, 100 g of rutile grade Iriodin® 103 (mica pigment coated with Ti02 of particle size 10 to 50 μm from Merck KgaA, Darmstadt, Germany) is coated with cerium sulphide. The resulting pigment has an intense orange-gold color and a high gloss.

Example 4 a) 100 g of mica of particle size of 10-60 μm are suspended in 2 1 of DI water and the suspension is heated to 75 ° C with continuous stirring. The pH of the suspension is adjusted to 6.0 using dilute hydrochloric acid (20%). During the addition of 650 ml of aqueous CeCl3 solution (108 g of CeCl3-7H20 in 600 g of DI water) the pH is kept constant at 6.0 using 20% sodium hydroxide solution. After the end of the addition, stirring is continued to complete the precipitation. The resulting pigment is filtered, washed, then dried at 110 ° C. The mica pigment coated with Ce02 is a white powder color and exhibits a weak silver interference. g of the product of Example 4a) in a quartz vessel are placed in a tubular furnace having a quartz tube. The oven is heated to 650 ° C (200 cmV in) under argon. Subsequently, H2S gas is additionally passed through the system for 1 h. After the end of the reaction, the product is allowed to cool to room temperature under inert gas (argon). This gives a bright red pigment that has a layer of? -Ce2S3.

Example 5 g of the product of Example 4a) are heated as in Example 4b) at 750 ° C in a rotary tube furnace under nitrogen (200 cmVmin). Subsequently, a stream of H2S (200 cmVmin) is further passed through the system for 5 h. After the end of the reaction, the product is allowed to cool to room temperature under inert gas (N2). The resulting cerium oxysulfide (Ce20S2) pigments have a green mass and a high gloss tone. 6 a) A solution of CeCl3 (68.4 g of CeCl3-7H20 made up to 700 ml with DI water) and a solution of oxalic acid (H2C204-2H20 made up to 700 ml with DI water) are measured simultaneously but separately at 75 ° C in a mica suspension (100 g mica of particle size 10-60 μm). After the end of the addition, the pigments are washed, dried at 110 ° C and calcined at 800 ° C. b) 10 g of the mica pigments coated with cerium oxalate are heated to 900 ° C in a tubular furnace in a quartz vessel under a stream of N2 (200 cmVmin). Subsequently, a stream of H2S (200 mVmin) is further passed through a system at 900 ° C for 4 h. After the end of the reaction, the product is allowed to cool to room temperature under inert gas (N2). The reddish violet pigments prepared in this way have a coating of β -Ce10S14O.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, the content of the following is claimed as property.

Claims (12)

1. Sulfide and oxysulfide pigments based on lamellar substrates, characterized in that the substrate is coated with yttrium and / or one or more rare earth metal sulphides of the formula M2S3 or the corresponding oxysulfides of the formula M2S3_xOx, wherein M is at least one element selected from the group consisting of the lanthanides and yttrium.

2. The pigments according to claim 1, characterized in that the rare earth metal sulfide or oxysulfide is a cerium, neodymium, praseodymium, samarium, gadolinium, terbium, dysprosium, erbium or thulium sulfide or oxysulfide.

3. The pigments according to claim 1 or 2, characterized in that the sheet-shaped substrate comprises mica flakes, Si02 / Ti02 or A1203 flakes, glass flakes, graphite, bismuth oxychloride or lamellar metal oxides, not coated or coated one or more times.

4. The pigments according to one of claims 1 to 3, characterized in that the mass of the rare earth metal sulphide or oxysulfide, based on the overall pigment, is from 1 to 400% by weight.

5. The pigments according to one of claims 1 to 4, characterized in that the sulphide layer or the oxide layer of rare earth metal is coated with one or more alkali metals and / or ferrous alkali metals.

6. The pigments according to the rei indication 5, characterized in that the coating element is present in amounts of 0.01 to 1.0% by weight, based on the sulfide layer or the oxysulfide layer.

7. The pigments according to the rei indication 5 or 6, characterized in that the coating element is sodium or potassium.

8. The pigments according to claims 1 to 7, characterized in that the substrate in the form of a lamella has a layer of cerium sulfide Ce2S3 coated with sodium.

9. The process for preparing the pigments according to claim 1, characterized in that a solution of a salt of a rare earth metal and / or yttrium and optionally a solution of oxalic acid, is added to an aqueous suspension of a substrate in the form of the lamella and, if desired, a coating in solid form or as an aqueous solution is added to the suspension, the pH of the suspension is kept substantially constant by the simultaneous addition of a base within a range that causes the hydrolysis of the salt added, and the pigment coated in this way with an oxide or hydrous oxide or oxalate is separated, washed, dried, and optionally first calcined at 400 to 800 ° C and finally converted to the sulfide or oxysulfide in the presence of sulfur compounds, CS2, sulfur or hydrogen sulfide of 550 to 1200 ° C.

10. The process according to claim 9, characterized in that the coating comprises one or more alkali metal salts and / or ferrous alkali metal salts. _ •

11. The use of the pigments according to claim 1, characterized in that it is used in formulations such as finishes for cars, paints, varnishes, printing inks, plastics and cosmetics.

12. The formulations, characterized in that they comprise pigments according to one of claims 1 to 8.