DE4319669A1 - New lustrous blue pigments - comprising lamellar substrate coated with colourless oxide and mixed molybdenum and/or tungsten oxide - Google Patents

Abstract

Lustrous pigments comprise a lamellar substrate coated with: (a) a first layer of colourless metal oxide; (b) a second layer of MoO2/MoO3 and/or WO2/WO3 mixed oxides; and (c) opt. a third layer of colourless metal oxide. Pref. the substrate comprises silicate and/or metallic platelets. Layers (a) and (b) comprise Ti, Zr, Si, Sn and/or Al oxide or hydroxide, esp. TiO2 and/or ZrO2. USE/ADVANTAGE - The pigments are blue metal-effect or pearlescent materials with interesting interference colour effects. They may be used in lacquers, printing inks, plastics, glass ceramics and cosmetics. Their high stability and good covering power make them esp. suitable for use in automobile lacquers.

Description

The present invention relates to new luster pigments the basis of multi-coated, platelet-shaped Substrates with

• A) a first layer of colorless metal oxide,
• B) a second layer of molybdenum (IV-VI) - and / or Tungsten (IV-VI) mixed oxides and
• C) if desired, a third layer of colorless Metal oxide.

The invention further relates to the production of these Gloss pigments and their use for coloring Lac ken, printing inks, plastics, glasses, ceramic products Decorative cosmetics and preparations.

Gloss or effect pigments are increasingly in used in many areas of technology, for example in Automotive paints, in decorative coatings, in art fabric coloring, in printing, painting, especially safe colors and in cosmetics.

Their optical effect is based on the directed reflection on mostly flat, aligned, aligned metal or strongly refractive pigment particles. Depending on The type of pigment particles is also referred to as a metallic effect pigments (e.g. aluminum, zinc, copper or their alloy gen) or pearlescent pigments (e.g. based on metal oxide layered mica such as muscovite, phlogopite and biotite, valley cum or glass).

The luster pigments can be coated by coating the starting sub strate with thin films of highly refractive oxides such as Chromium (III) oxide, especially iron oxide and titanium oxide, multi-phase be constructed. Through interference and possibly absorption tion arises in these cases depending on the  Thickness of the oxide layer a variety of color variations; these pigments are therefore also called interference pigments.

Due to the directed reflection of the incident light the platelet-shaped pigment particles show the z. B. in Lacquer-oriented, coated gloss pigments Goniochro maticity, d. H. the color impression (brightness and / or color tone and / or color saturation) of your paintwork changes to Dependence on the exposure or viewing angle. This Effects can be based on a complicated interplay of Reflection and transmission of the incident light back lead, the color of which is due to the pigment particles called phenomena such as interference on thin layers and absorption at colored centers can be changed.

Depending on the thickness of the TiO ₂ layer, mica pigments coated with colorless oxides such as titanium dioxide show delicate interference colors and have an essentially white to yellowish body color of weak intensity. In the case of TiO ₂ -coated metal pigments, the respective interference color is superimposed by a strong metallic sheen, which is created by reflection of the incident light on the impermeable metallic substrate.

The Be layering with colored oxides, especially with Iron (III) oxide. Particularly brilliant color pigments are here in the yellow to red area if the inter reference color approximates the absorption color Right. However, interference color and body color are not correct match, so the applied pigments show in the favorable Fall an angle-dependent color impression, a "two tone "effect. In the worst case, dull, unat tractive shades.

Especially with the interference pigments with a blue body color has so far not succeeded, satisfactory To manufacture products.

In US Pat. Nos. 3,951,679 and 4,047,769, pigments are described, for example, which are obtained by the deposition of Berlin blue (Fe ₄ [Fe (CN) ₆ ] ₃ ) from aqueous solution on metal oxide-coated mica. The major problem with these pigments is that they tend to release cyanide and, moreover, are not thermally stable. In addition, the homogeneous precipitation of Berlin blue poses difficulties.

Furthermore, the coverage is also coated with metal oxide Mica with organic dyes or pigments (EP-A-3 67 236 and US-A 4 755 229) are known, however, to to achieve a certain stability with the help of additive substances must be bound to the substrate surfaces.

The invention was therefore based on the object, stable gloss to provide pigments with blue shades that also are easy and reproducible to manufacture.

Accordingly, the luster pigments defined at the outset were obtained find.

Furthermore, there was a process for producing this gloss found pigments, which is characterized in that the platelet-shaped substrate by gas phase decomposition volatile compounds of metals in the presence of acid fabric and / or water vapor in succession with the layer ten (A), (B) and if desired (C).

In addition, the use of these luster pigments became one coloring of paints, printing inks, plastics, glasses, ke ramische products and preparations of the decorative Kosme tik found.

For the luster pigments according to the invention come as substrates in particular silicate or metallic platelets or their mixtures into consideration.

Light or white mica are particularly preferred, in particular their scales of wet ground muscovite. Of course Other natural mica such as phlogopite and organic are also available tit, artificial mica, talc and glass scales suitable.

Silicate substrates can be used in the manufacture of gloss pigments according to the invention advantageously already in it layer with colorless oxides such as titanium, zirconium and / or mica platelets coated with tin dioxide are used,  as they are known under the names Iriodin® (E. Merck, Darmstadt), Flo nac® (Kemira Oy, Pori, Finland) and Mearlin® (Mearl Corpo ration, New York) are on the market.

As metallic substrates come for the invention Pigments all metals known for metallic effect pigments in Platelet shape in question; e.g. B. are next to copper and its Alloys such as brass or bronze, especially aluminum and its alloys like aluminum bronze. Prefers are aluminum plates, which are easily manufactured by Her punch out of aluminum foil or according to usual Verdü solution or grinding techniques can be obtained. It can if commercially available products are used, the Metal surface largely free of grease or other be should be laid.

The size of the substrate particles is not critical per se and can be tailored to the particular application. As a rule, the particles have an average largest diameter of approximately 5 to 120 μm and thicknesses of approximately 0.2 to 4 μm. The specific free surface area (BET) of the metal flakes is generally 0.5 to 5 m ² / g.

The luster pigments according to the invention are notable for Multiple coating of the platelet-shaped substrate.

The first layer (A) is the usual one for coating of interference pigments suitable metal oxides or their Mixtures built up. Here are the colorless metal oxides such as silicon, tin and aluminum oxide, especially zirconium oxide and especially titanium dioxide, which is found in both rutile and can also be present in anatase modification, preferred. Of the Use of colored metal oxides such as iron oxide and chromium oxide also conceivable, but usually the colorless ones To prefer metal oxides to achieve pure shades of blue.

The thickness of the layer (A) is not critical per se and usually lies in that for the classic pearlescent pig ment known range from about 20 to 400 nm, in particular 35 to 250 nm.  

However, it is also possible to coat the substrate only with extremely thin TiO ₂ layers of about 20 nm thickness, which do not cause interference colors and only as an adhesion promoter between the substrate and the subsequent layer of molybdenum or tungsten mixed oxides (B) serve. In the case of thick layers (B) (approximately 20 to 200 nm), particularly strong blue-tinted pigments are obtained without a two-tone effect. This is of course also the case if the TiO ₂ layer produces a blue interference color (TiO ₂ content of the pigment about 52% by weight).

The second blue layer (B) is essentially made up of mixed valence oxides of molybdenum and / or tungsten, in which the metals are present in oxidation states from IV to VI. The limits for the gross composition of these oxides are MO ₂ and MO ₃ (M = Mo, W). Pure MO ₃ is colorless, so lower metal oxides must be present at least in part. If the production of layer (B) is carried out in the presence of steam, the deposited oxides can also contain water (oxide hydroxides). Such oxi dische and oxide hydroxide phases are known in the literature as Magn'li phases or molybdenum and tungsten blue.

Scanning electron micrographs of coated mica pigments show the structure of the layer (B) according to the invention made of felt-like interwoven needle crystals with needle lengths of less than 100 nm. The layer is not constructed like a film, which is why it does not lead to a change in the interference color of the substrate. It is semi-permeable, ie it is so dense on the one hand that a blue color impression arises at the appropriate viewing angle, and on the other hand so transparent that the interference color is also not obscured at the appropriate viewing angle, and brings about an intensification of the interference color by lowering the white base of the light . With suitable TiO ₂ layer thicknesses, any color flops can be realized.

In particular with metallic substrates, the fiction according layer (B) can also be constructed in film form and thus contribute to the interference.  

Depending on which shade - absorption or interference color - should predominate, is a thicker or thinner Layer (B) to choose. Appropriate molybdenum or tungsten contents are usually 0.1 to 30% by weight, preferably 3 to 25% by weight.

Furthermore, the luster pigments according to the invention can also have a third layer (C) which, like layer (A), preferably consists of colorless metal oxides such as silicon oxide, tin oxide and aluminum oxide and / or aluminum hydroxides (Al (OH) ₃ , AlO (OH)), especially zirconium dioxide and very special titanium dioxide. If desired, this cover layer can further improve the resistance to environmental influences.

The thickness of the layer (C) is also not critical, in general mine is about 1 to 400 nm, especially 5 to 200 nm.

The layer (C) can with appropriate layer thicknesses and when using strongly refractive oxides such as titanium dioxide Contribute to interference of the pigment. In this case it leads the series of interference at the one indicated by (A) (and (B)) layered substrate specific location.

In the inventive method for producing the multi-coated platelet-shaped substrates the individual layers successively by gas phase decomposition volatile compounds of the metals in the presence of Oxygen and / or water vapor on the substrate particles applied (chemical vapor deposition, CVD process).

This assignment can be advantageous in a heatable vortex Layer reactor, as described, for example, in EP-A 33 457 or DE-A 38 13 335 is described in which the unbe layered or already coated once or twice Substrate particles are first fluidized with a fluidizing gas and to those for the decomposition of the respective metal compound required temperature of usually 70 to 350 ° C be heated. The vaporized metal compounds and the gases required for decomposition are then separated Nozzles entered.  

For the deposition of the first and, if desired, the third layer of metal oxide, in particular the halides, especially the chlorides, and the alcoholates, both aromatic and phenolates and benzyl alcoholates, and aliphatic, especially C ₁ -C ₄ -alkano late, are volatile metal compounds such as n-, iso- and tert-butanolates, preferably methano late and ethanolates and particularly preferably n- and iso-pro panolates.

Preferred metal compounds are titanium, zirconium, Silicon and tin tetrachloride, aluminum chloride and Ti tan and zirconium n and iso propanolate.

These metal compounds are conveniently by What hydrolyzed to the oxides. At least which stoichiometrically required to form the desired oxides amount of water vapor can be supplied, but you can also work with a small excess. As a fluidizing gas can both stick in the decomposition of the metal halides serve as well as air when using the metal alcoholates nitrogen is preferable.

To evenly and completely enveloping the substrate, ho to obtain homogeneous layers, the amount of gas in the Me tallverbindung in general not more than 5 vol .-% before preferably not more than 2% by volume of the total amount of gas in the re actuator.

The hydrolytic decomposition of the particularly preferred Ti tantetrachloride is generally at 150 to 250 ° C before taken.

As already mentioned above, in the process according to the invention, substrates coated with metal oxide, in particular titanium dioxide, can be used as starting materials. This is particularly favorable in the case of the TiO ₂ -coated mica, since these are known commercial products. Of course, the metal, especially aluminum pigments used can already be coated with TiO ₂ deposited from alcoholic solution of organic titanium acid esters (EP-A 3 28 906). However, in the case of metal pigments, the substrates coated from the gas phase will always be preferred because of the better quality.

In terms of process technology, it is favorable to have a third coating without intermediate insulation of that covered with layer (B) Pigments after exchange of the vortex gases directly in the same Reactor.

To deposit the blue layer (B) are considered volatile Molybdenum or tungsten compounds advantageously the carbo nyls, especially molybdenum and tungsten hexacarbonyl sets that expediently by oxygen or air in Mixture with nitrogen in the presence or absence of water steam can be decomposed.

In order to obtain the desired molybdenum or tungsten mixed oxides MO _x , the oxygen should generally be 0.5 to 10% by volume, preferably 0.8 to 6% by volume, and the water vapor should be about 0 to 2% by volume. % of the total amount of gas in the reactor.

The required reactor temperature is generally 150 to 250 ° C, preferably 200 to 220 ° C.

After coating is complete, the cooled Pro carried out as usual.

The process according to the invention enables the multi-coated gloss pigments to be produced in a simple and reproducible manner. The pigments obtained are characterized by high gloss and high color purity. Particularly brilliant blue pigments result if the interference color of the TiO ₂ -coated substrate matches the intrinsic color of layer (B) or if only an extremely thin TiO ₂ layer was applied. Interesting color flops from red to blue, green to blue and yellow to pigeon blue can be achieved by choosing suitable TiO ₂ layer thicknesses and molybdenum or tungsten contents.

The gloss pigments according to the invention are advantageously suitable for many purposes, such as for coloring paints, printing ink ben, plastics, glasses, ceramic products and accessories decorative cosmetics. Because of their high  They are particularly stable and have good hiding power of great interest for automotive painting.

Examples Production of gloss pigments according to the invention

The coatings of mica or TiO ₂ -coated mica pigments and aluminum umpigmenten described in the examples were each in an externally heated fluidized-bed reactor made of glass with a diameter of 8 cm and a height of 80 cm with a glass frit bottom and a suspended with stock up on a nitrogen jet cleaning filter and two nozzles for gas introduction are placed on the side above the frit bottom.

To assess the color of the pigments obtained each 0.4 g of the pigment samples in 3.6 g of a polyester Mixed paint with 21 wt .-% solids and stirred Dispersed in the Red Devil for 2 minutes. With a Spiralra kel (80 microns wet film thickness) were then on a black and white cardboard prints of the pigmented varnish does. The CIELAB values were measured after drying the film with a DATACOLOR spectrophotometer MCS 111 with metallic measuring head GK 111 at an angle difference of 20 ° -70 ° to the gloss angle. The details of the color values (L, a *, b *) refer to standard illuminant D 65 and a Be viewing angles of 25 °, 45 ° and 70 °. L corresponds to the brightness, a * the red or green component and b * the blue or yellow content. H is the color angle and C is the chroma. Ge measurement was carried out on a white surface with simply scraped off Rehearse.

A) Production of double-coated mica pigments example 1

200 g of ground muscovite mica with a particle size of 5-250 μm were heated to 150 ° C. in a fluidized bed reactor with swirling at a total of 800 l / h of an air / nitrogen mixture. Half of this amount of gas was passed as an air / nitrogen mixture (1: 1) through a water reservoir heated to 50 ° C. The other half of the gas amount, which consisted only of nitrogen, was blown in with a titanium tetrachloride at a temperature of 30 ° C. In this way, 34.5 g of TiCl _{4 were} fed in within 3 h.

After the TiO ₂ deposition had ended, the reactor temperature was raised to 220.degree. The composition of the fluidized gas mixture loaded with water vapor was changed to 100 l / h air and 300 l / h nitrogen. In addition, 400 l / h were blown in through a template heated to 70 ° C. with molybdenum hexacar bonyl-guided nitrogen. In this way, 63.8 g of Mo (CO) _{6 were} fed in within 8 h.

After the deposition of molybdenum oxide, the Pro product cooled and discharged.

The blue pigment obtained had a molybdenum content of 9.5% by weight and a titanium content of 3.8% by weight. The deposited TiO ₂ was in the anatase modification.

The color data of this pigment are in Table 2 listed.

Examples 2 to 8

200 g of the mica pigment coated with metal oxide given in Table 1 were heated to 220 ° C. in a fluidized bed reactor while swirling with a total of 850 l / h of a nitrogen / air (8: 1) mixture. Half of the vortex gases were passed through a water reservoir heated to 50 ° C. In addition, 400 l / h were blown through a nitrogen containing molybdenum hexacarbonyl, which was heated to 70 ° C. So xg Mo (CO) _{6 were} added within 8-24 h.

Details of these experiments and their results are compiled in Table 1. The coloristic data of the pigments obtained are listed in Table 2.  

B) Production of double-coated aluminum pigments Example 9

A mixture of 100 g aluminum powder (average particle diameter 20 microns, BET surface area 4.5 m ² / g) and 100 g coarser aluminum powder (average particle diameter 60 microns, BET surface area 1.5 m ² / g) was in the fluidized bed reactor heated to 180 ° C. while swirling with a total of 800 l / h of nitrogen. Half of the gas stream was passed through a water reservoir tempered at 50 ° C and the other half through a template tempered at 50 ° C with titanium tetrachloride. In this way, 85 g of TiCl _{4 were} fed in within 12 h.

After the TiO ₂ deposition had ended, the reactor temperature was raised to 200.degree. 400 l / h of fluidizing gas (nitrogen / air 7: 1) were passed through a water reservoir heated to 40 ° C. In addition, 400 l / h were blown through a template heated to 70 ° C with molybdenum hexacarbonyl nitrogen.

The blue metallic pigment obtained has a highly metallic sheen had a molybdenum content of 11.5% by weight, a titanium content of 7.3% by weight and an aluminum content of 67.0% by weight.

His coloristic data are listed in Table 2.  

Claims (9)

1. Gloss pigments based on multi-coated, platelet-shaped substrates with

• A) a first layer of colorless metal oxide,
• B) a second layer of molybdenum (IV-VI) and / or tungsten (IV-VI) mixed oxides and
• C) if desired, a third layer of colorless metal oxide.

2. Gloss pigments according to claim 1, in which the substrate from silicate and / or metallic flakes stands. 3. Gloss pigments according to claim 1 or 2, in which the Layers A) and C) essentially made of titanium, zirconium, Silicon, tin and / or aluminum oxide or hydroxide consist. 4. Gloss pigments according to claims 1 to 3, in which the Layers A) and C) essentially made of titanium and / or Zirconium oxide exist. 5. Process for the preparation of the luster pigments according to the Claims 1 to 4, characterized in that one Substrate by gas phase decomposition of volatile compounds against the metals in the presence of oxygen and / or Steam in succession with layers (A), (B) and if desired (C) occupied. 6. The method according to claim 5, characterized in that as volatile molybdenum and tungsten compounds Carbonyle uses. 7. The method according to claim 5, characterized in that one as volatile metal compounds for the layer ten (A) and (C) uses the halides or alcoholates.   8. The method according to claim 5, characterized in that one already in the first layer with colorless metal oxide used substrate and then this with the Layer (B) and if desired (C) occupied. 9. Use of the luster pigments according to claims 1 to 4 for coloring paints, printing inks, plastics, Glasses, ceramic products and preparations from de cosmetic cosmetics.