DE10331903A1 - Silver pigment with high covering power, used in paint, lacquer, automotive coating, printing ink, plastics, ceramics, glass, cosmetic, pigment or dry preparation, has absorbing layer besides layers of high and lower refractive index - Google Patents

Abstract

Silver pigments with high covering power, based on coated flaky substrates, have sequence(s) of (B) a colorless, 10-300 nm thick layer with refractive index n at most 1.8 between (A, C) highly refracting, 5-200 nm titanium dioxide (TiO2) layers with absorbing layer of titanium (Ti), iron, chromium (Cr), cobalt, nickel, vanadium, molybdenum (Mo) and tungsten (W) oxide, sulfide, nitride, sulfoxide and/or aluminum, silver, Cr, palladium, platinum, gold, Mo or W metal layer. Independent claims are also included for the following: (1) preparation of the silver pigments by coating the substrate by a wet chemical method by hydrolytic decomposition of metal salts in aqueous medium by chemical or physical vapor deposition (CVD, PVD) and/or by reduction from aqueous solutions of metal salts; (2) pigment preparations or dry preparations containing binder(s), optionally additive(s) and the silver pigment(s).

Description

The present invention relates to silver-colored gloss pigments with high hiding power based on multiple coated platelet-shaped substrates.

Gloss or effect pigments used in many areas of technology, especially in the area car paints, decorative coatings, plastics, colors, Printing inks and in cosmetic formulations.

Processes for producing pearlescent pigments are known from the prior art, with the aid of which alternating layers with high and low refractive indices can be applied to finely divided substrates. Such pigments based on multi-coated platelet-shaped substrates are, for. B. from the US 4,434,010 . JP H7-759 . US 3,438,796 . US 5,135,812 . DE 44 05 494 , DE 44 37 753, DE 195 16 181 and DE 195 15 988 known.

Of particular importance Pearlescent pigments on a mineral basis. Pearlescent pigments by coating an inorganic, platelet-shaped carrier with a highly refractive, mostly made of oxide layer. The color of these pigments is through wavelength selective Partial reflection and interference of the reflected or transmitted Light caused at the medium / oxide or oxide / substrate interfaces.

The interference color of these pigments is determined by the thickness of the oxide layer. The hue of an interference silver pigment is due to a single high refractive index layer in the optical sense generated, the optical thickness of a reflection maximum (1st order) in the visible wavelength range conditional at approx. 500 nm. The human eye takes this wavelength than the color green true. The intensity course this maximum on their wavelength axis is so wide that so much light reflects in the whole range of visible light is that the human eye has a very bright but colorless Perceives impression.

According to the - especially from the compensation optical Components - known Rules of optics thinner Layers increase in a three-layer system compared to the one-layer system the intensity at the interference maximum by about 60%. As a result, the profile the light reflected by interference much more pronounced, so that for such a multilayer system to expect a green reflection color is.

In the DE 100 61 178 describes an interference system in the form of alternating high-index layers of TiO ₂ and low-index layers on a transparent substrate plate, which produces an intense silver color impression at certain layer thicknesses.

This pigment type is characterized by a very bright and pure silver tone with high transparency. This transparency is desirable in numerous applications because it enables a particularly high variety of attractive combinations with other coloring components in the application. In many cases - especially for applications in thin coatings - in addition to the attractive silver effect, high hiding power is also desirable. Multilayer pearlescent pigments as in the DE 100 61 178 have a particularly high level of transparency due to their structure, so that increasing the hiding power while maintaining the bright silver effect was a particular challenge. The present invention describes the solution to this problem.

• (A) einer hochbrechenden Beschichtung bestehend aus TiO₂ mit einer Schichtdicke von 5–200 nm,
• (B) einer farblosen Beschichtung mit einem Brechungsindex n ≤ 1,8 mit einer Schichtdicke von 10–300 nm,
• (C) einer hochbrechenden Beschichtung bestehend aus TiO₂ mit einer Schichtdicke von 5–200 nm,

enthalten,
wobei die Schichten (A) und (C) zusätzlich eine absorbierende Schicht von Oxiden, Sulfiden, Nitriden, Suboxiden der Elemente Titan, Eisen, Chrom, Kobalt, Nickel, Vanadium, Molybdän und Wolfram oder eine Metallschicht aus Aluminium, Silber, Chrom, Palladium, Platin, Gold, Molybdän oder Wolfram und/oder Kombinationen davon aufweisen.The invention therefore relates to silver-colored gloss pigments with high hiding power on the basis of multi-coated platelet-shaped substrates, which comprise at least one layer sequence

• (A) a high-index coating consisting of TiO ₂ with a layer thickness of 5-200 nm,
• (B) a colorless coating with a refractive index n ≤ 1.8 with a layer thickness of 10-300 nm,
• (C) a high-index coating consisting of TiO ₂ with a layer thickness of 5-200 nm,

contain,
the layers (A) and (C) additionally an absorbent layer of oxides, sulfides, nitrides, suboxides of the elements titanium, iron, chromium, cobalt, nickel, vanadium, molybdenum and tungsten or a metal layer made of aluminum, silver, chromium, palladium , Platinum, gold, molybdenum or tungsten and / or combinations thereof.

• – einen hohen Glanz bei steiler und geneigter Betrachtungsweise
• – ein besonders hohes Deckvermögen
• – einen besonders metallischen Glanzeffekt.

The opaque silver pigments according to the invention show in comparison to the known pearlescent pigments in the silver range

• - a high gloss with a steep and inclined view
• - a particularly high hiding power
• - a particularly metallic gloss effect.

The subject of the invention is furthermore the use of the opaque invention Silver pigments in paints, varnishes, in particular car paints, printing inks, Plastics, ceramic materials, glasses and cosmetic formulations. The pigments according to the invention are also also for the production of pigment preparations and for the production of dry preparations, such as B. granules, chips, pellets, sausages, briquettes, etc., suitable. The dry preparations are especially for Printing inks and suitable in cosmetics.

Suitable base substrates for the multilayer pigments according to the invention are selectively or non-selectively absorbing platelet-shaped substrates. Layered silicates are preferred substrates. Natural and / or synthetic mica, talc, kaolin, platelet-shaped iron or aluminum oxides, glass, SiO ₂ -, TiO ₂ -, graphite platelets, synthetic carrier-free platelets, titanium nitride, titanium silicide, liquid crystal polymers (LCPs), holographic pigments are particularly suitable , BiOCl, platelet-shaped mixed oxides, such as. B. FeTiO ₃ , Fe ₂ TiO ₅ , or other comparable materials.

The size of the base substrates is on is not critical and can be tailored to the respective application become. As a rule, the platelet-shaped substrates have a thickness between 0.005 and 10 μm, in particular between 0.05 and 5 μm. The expansion in the other two areas is usually between 1 and 500 μm, preferably between 2 and 200 μm, and in particular between 5 and 60 μm.

The thickness of each layer (A) and (B) and (C) with high and low refractive index the base substrate is essential for the optical properties of the pigment. For the opaque silver pigment with a high metallic gloss effect must the thickness of the individual layers precisely adjusted to each other become.

The thickness of the layer (A) or (C) is 5-200 nm, preferably 10-100 nm, in particular 20-70 nm. The TiO ₂ layers (A) and (C) can have the same or different layer thicknesses. The thickness of the layer (B) is 10-300 nm, preferably 20-100 nm, in particular 30-80 nm. The TiO ₂ layers can be in the rutile or in the anatase modification. Layers (A) and (C) are preferably rutile layers.

The pigments can contain several, identical or different combinations of layer packs, but preference is given to covering the substrate with only one layer pack (A) (A ') + (B) + (C) (C') + optionally (D). To intensify the color strength, the pigment according to the invention can contain up to 4 layer packets, although the thickness of all layers on the substrate should not exceed 3 μm. An odd number of layers are preferably applied to the platelet-shaped substrate, each with a highly refractive layer in the innermost and outermost layers. A structure in the sequence is particularly preferred
Substrate + (A) (A ') (B) (C)
Substrate + (A) (B) (C) (C ')
Substrate + (A) (A ') (B) (C) (C')
Substrate + (A ') (A) (B) (C)
Substrate + (A) (B) (C ') (C)
Substrate + (A) (A ') (B) (C') (C)
Substrate + (A ') (A) (B) (C) (C')
the layer sequence (A) (B) (C) (C ') is particularly preferred.

As colorless low-index materials suitable for coating (B) are preferably metal oxides or the corresponding oxide hydrates, such as. As SiO ₂ , Al ₂ O ₃ , AlO (OH), B ₂ O ₃ , MgF ₂ , MgSiO ₃ or a mixture of the metal oxides mentioned, suitable. Layer (B) is in particular an SiO ₂ layer.

In comparison with the in DE 100 61 178 The multilayered silver pigments described with high transparency may have to be modified downwards, depending on the thicknesses of the absorbent layers A 'and C', in order to preserve the silvery color impression. By precisely matching the layer thicknesses, however, more or less intense interference colors can be superimposed on the silver effect, for example in the blue or gold range.

The additional layers A 'or C 'determine the opacity of the Product. The thickness of these layers is between 0.5 nm and 100 nm, preferably between 1 and 50 nm and particularly preferably between 2 and 30 nm. With increasing thickness and number of layers A 'and / or C 'increases the opacity of the product, at the same time the brightness of the silver increases Color impression. These properties can vary within wide limits and thus the desired one optical properties of the product can be selected accordingly.

The pigments according to the invention can be produced by creating multiple high and low refractive interference layers and thinner Absorption layers with a precisely defined thickness and smooth surface the finely divided, platelet-shaped substrates.

The metal oxide layers are preferably applied wet-chemically, with those for production wet chemical coating processes developed from pearlescent pigments can be used. Such methods are e.g. B. described in DE 14 67 468 . DE 19 59 988 . DE 20 09 566 . DE 22 14 545 . DE 22 15 191 . 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 35 017 or also in further patent documents and other publications known to the person skilled in the art.

With wet coating, the Substrate particles suspended in water and with one or more hydrolyzable metal salts or a water glass solution one for the hydrolysis is shifted to a suitable pH value, which is selected in such a way that the metal oxides or metal oxide hydrates are precipitated directly on the platelets, without causing co-precipitation comes. The pH is usually constant by simultaneously adding a base and / or acid held. Subsequently the pigments are separated, washed and at 50-150 ° C for 6-18 h dried and optionally 0.5-3 h annealed being the annealing temperature be optimized with regard to the respective coating can. As a rule, the annealing temperatures are between 250 and 1000 ° C, preferably between 350 and 900 ° C. if desired can the pigments are separated after applying individual coatings, dried and annealed if necessary to be conspicuous of the other layers to be resuspended.

In the event that the layers A 'and C' contain Fe ₃ O ₄ or FeTiO ₃ or other reduced oxide types or metals, a reduction step, for example annealing in a reducing atmosphere, may be necessary.

Furthermore, the coating can also be carried out in a fluidized bed reactor by gas phase coating, z. B. the in EP 0 045 851 and EP 0 106 235 proposed methods for the production of pearlescent pigments can be applied accordingly.

The color of the opaque pigments can keep within a very wide range while maintaining the silver effect different choice of occupancy or the resulting Layer thicknesses can be varied. Fine-tuning for one certain shade can over the pure choice of quantity through visually or metrologically controlled Approach the desired Color can be achieved.

To increase light, water and weather stability, it is often advisable, depending on the area of application, to subject the finished pigment to a post-coating or post-treatment. Post-coatings or post-treatments include, for example, those in the DE-PS 22 15 191 . DE-OS 31 51 354 . DE-OS 32 35 017 or DE-OS 33 34 598 described methods in question. This post-coating (layer D) further increases the chemical stability or facilitates the handling of the pigment, in particular the incorporation into different media.

The pigments of the invention are with a Variety of color systems compatible, preferably from the field of varnishes, paints and inks. For the production of printing inks for z. B. gravure printing, flexographic printing, offset printing, offset overprint coating, is a variety of binders, especially water-soluble types, suitable as z. B. from the companies BASF, Marabu, Pröll, Sericol, Hartmann, Gebr. Schmidt, Sicpa, Aarberg, Siegberg, GSB election, Follmann, Ruco or Coates Screen INKS GmbH are sold. The printing inks can water-based or solvent-based be constructed. Furthermore, the pigments are also for laser marking of paper and plastics, as well as for applications in the agricultural sector, e.g. B. for Greenhouse films, and z. B. for the coloring of tarpaulins, suitable.

Since the silver pigments according to the invention strong shine with high coverage and neutral body color combine, they can be particularly effective effects in the achieve different application media, e.g. B. in cosmetic formulations, such as B. nail varnishes, lipsticks, press powders, gels, lotions, Soaps, toothpaste, in paints, in particular car paints and industrial paints, and powder coatings, as well as in plastics and ceramics.

It goes without saying that for the various applications, the multilayer pigments are also advantageously mixed with organic dyes, organic pigments or other pigments, such as. B. transparent and opaque white, colored and black pigments and with platelet-shaped iron oxides, organic pigments, holographic pigments, LCPs (Liquid Crystal Polymers), and conventional transparent, colored and black gloss pigments based on metal oxide coated mica and SiO ₂ platelets , etc., can be used. The multilayer pigments can be mixed in any ratio with commercially available pigments and fillers.

The pigments according to the invention are also suitable for the production of flowable pigment preparations and dry preparations, especially for Printing inks containing one or more pigments according to the invention, Binder and optionally one or more additives.

The object of the invention is thus also the use of pigments in formulations such as paints, printing inks, Security printing inks, varnishes, plastics, ceramic materials, glass and in cosmetic formulations.

The following examples are intended the invention closer explain but without limiting it.

example 1

Level A

100 g of mica with a particle size of 10–60 μm are heated to 75 ° C in 2 l of demineralized water. After this temperature has been reached, a solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is slowly metered into the mica suspension. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 270 g of a 32% TiCl ₄ solution are metered in at this pH, the pH being kept constant with 32% sodium hydroxide solution. The pH is then raised to 7.5 and at this pH 270 g of sodium silicate solution (13.5% by weight SiO ₂ ) are slowly metered in, the pH being raised to 7.5 with 10% HCl is kept constant. A solution consisting of 3 g SnCl ₄ × 5 H ₂ O in 90 g water is then slowly added to the mica suspension at pH 2.0. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 300 g of a 32% TiCl ₄ solution are metered in. After stirring for 0.5 h at pH = 1.8, the coated mica pigment is filtered off, washed and dried at 110 ° C. for 16 h. Now the pigment is annealed at 850 ° C for 1 hour.

Level B

The annealed product is sieved (63 μm mesh size) and mixed intimately with 2% by weight of silicon powder (grain size <5 mm) and 2% by weight of anhydrous CaCl ₂ . This mixture is annealed for one hour at 850 ° C in a nitrogen atmosphere.

A silver-colored gloss pigment is obtained with blue-gray body color.

Example 2

In a closed apparatus 200 g of the intermediate from Example 1 / Step A are demineralized in 2 l Suspended water and heated to 75 ° C with vigorous stirring. At this temperature the pH was adjusted to 8.0 with sodium hydroxide solution (32%).

A nitrogen stream (approx. 130 ml / h) is passed into the suspension until work-up begins to prevent the penetration of atmospheric oxygen. A solution of 10.8 g of FeSO ₄ × 7 H ₂ O, 1.8 g of KNO ₃ and 0.6 g of sulfuric acid (20%) in 30 ml of demineralized water is added to this suspension at a rate of 2 ml / min. metered. The pH is kept at 8.0 with sodium hydroxide solution (32%). After the metering phase has ended, stirring is continued for 0.5 h at pH 8.0 and 75 ° C., the product is filtered off, washed with 10 l of demineralized water and dried at 110 ° C. for 16 h. The product is then sieved (63 μm mesh size).

A silver-colored gloss pigment is obtained with gray body color.

Example 3

200 g of the intermediate from Example 1 / Step A are suspended in 1 l of demineralized water and a solution of 3.2 g of AgNO ₃ and 16 ml of ammonia solution (25%) in 40 ml of demineralized water is added. Then, with vigorous stirring, a solution of 2 ml of formaldehyde solution (37%) in 40 ml of demineralized water at a rate of 1 ml / min. dropwise. The suspension is stirred for a further 0.5 h, the product is filtered off, washed with 10 l of demineralized water and dried at 110 ° C. for 16 h. Finally, screening (63 μm) takes place.

A silver-colored gloss pigment is obtained with light gray body color.

Example 4

200 g of the intermediate from Example 1 / Step A are suspended in 2 l of demineralized water and heated to 75 ° C. with vigorous stirring. Now the pH is adjusted to 2.9 with hydrochloric acid (10%). Then 10 g of a hydrochloric acid FeCl ₃ solution (12% Fe) at a rate of 2 ml / min. metered in, the pH being kept constant at 2.9 with sodium hydroxide solution (32%). After a subsequent stirring time of 15 minutes, the product is filtered off, washed and dried at 110 ° C. for 16 hours. The dried powder is calcined at 850 ° C under forming gas (8% H ₂ /92% N ₂ ) and sieved (63 μm). A pigment with a metallic silver sheen and a gray body color is obtained.

Example 5

100 g of mica with a particle size of 10–60 μm are heated to 75 ° C in 2 l of demineralized water. After this temperature has been reached, a solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is slowly metered into the mica suspension. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 265 g of a 32% TiCl ₄ solution are metered in at this pH, the pH being kept constant with 32% sodium hydroxide solution. The pH is then raised to 7.5 and at this pH 270 g of sodium silicate solution (13.5% by weight SiO ₂ ) are slowly metered in, the pH being raised to 7.5 with 10% HCl is kept constant. A solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is then slowly metered into the mica suspension at pH 2.0. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 290 g of a 32% TiCl ₄ solution are metered in. Then the pH is raised to 2.9 with sodium hydroxide solution (32%) and 10 g of a hydrochloric acid FeCl ₃ solution (12% Fe) at a rate of 2 ml / min. metered in, the pH being kept constant at 2.9 with sodium hydroxide solution (32%). The product is after a stirring time of 15 min. filtered off, washed and dried at 110 ° C for 16 h. The dried powder is calcined at 850 ° C under forming gas (8% H ₂ /92% N ₂ ) and sieved (63 μm). A covering pigment with a metallic silver sheen and a gray body color is obtained.

Example 6

100 g of mica with a particle size of 10–60 μm are heated to 75 ° C in 2 l of demineralized water. After this temperature has been reached, a solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is slowly metered into the mica suspension. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 265 g of a 32% TiCl ₄ solution are metered in at this pH, the pH being kept constant with 32% sodium hydroxide solution. Then the pH is raised to 2.9 with sodium hydroxide solution (32%) and at this pH 10 g of a hydrochloric acid FeCl ₃ solution (12% Fe) at a rate of 2 ml / min. metered in, the pH being kept constant at 2.9 with sodium hydroxide solution (32%). The pH is then raised to 7.5 and, at this pH, 270 g of sodium water glass solution (13.5% by weight SiO ₂ ) are slowly metered in, the pH being constant at 7.5 with 10% HCl is held. A solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is then slowly metered into the mica suspension at pH 2.0. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 285 g of a 32% TiCl ₄ solution are metered in. Then the pH is raised to 2.9 with sodium hydroxide solution (32%) and 10 g of a hydrochloric acid FeCl ₃ solution (12% Fe) at a rate of 2 ml / min. metered in, the pH being kept constant at 2.9 with sodium hydroxide solution (32%). The product is after a stirring time of 15 min. filtered off, washed and dried at 110 ° C for 16 h. The dried powder is calcined at 850 ° C under forming gas (8% H ₂ /92% N ₂ ) and sieved (63 μm). A highly opaque pigment with a metallic silver sheen and gray body color is obtained.

Example 7

100 g of mica with a particle size of 10–60 μm are heated to 75 ° C in 2 l of demineralized water. After this temperature has been reached, a solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is slowly metered into the mica suspension. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 265 g of a 32% TiCl ₄ solution are metered in at this pH, the pH being kept constant with 32% sodium hydroxide solution. Then the pH is raised to 2.9 with sodium hydroxide solution (32%) and at this pH 10 g of a hydrochloric acid FeCl ₃ solution (12% Fe) at a rate of 2 ml / min. metered in, the pH being kept constant at 2.9 with sodium hydroxide solution (32%). The pH is then raised to 7.5 and, at this pH, 270 g of sodium water glass solution (13.5% by weight SiO ₂ ) are slowly metered in, the pH being constant at 7.5 with 10% HCl is held. A solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is then slowly metered into the mica suspension at pH 2.0. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 285 g of a 32% TiCl ₄ solution are metered in. After a subsequent stirring time of 15 minutes, the product is filtered off, washed and dried at 110 ° C. for 16 hours. The dried powder is annealed at 850 ° C under forming gas (8% H ₂ /92% N ₂ ) and sieved (63 μm). A highly opaque pigment with a metallic silver gloss and gray body color is obtained.

Example 8

100 g of mica with a particle size of 10–60 μm are added to 75 ° C in 2 l of demineralized water heated. After this temperature has been reached, a solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is slowly metered into the mica suspension. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 270 g of a 32% TiCl ₄ solution are metered in at this pH, the pH being kept constant with 32% sodium hydroxide solution. The pH is then raised to 7.5 and 270 g of sodium water glass solution (13.5% by weight SiO ₂ ) are slowly metered in at this pH, the pH being kept constant at 7.5 with 10% NCl becomes. Then the pH is lowered to 2.9 with hydrochloric acid (10%) and at this pH 10 g of a hydrochloric acid FeCl ₃ solution (12% Fe) at a rate of 2 ml / min. metered in, the pH being kept constant at 2.9 with sodium hydroxide solution (32%). Then 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water at pH 2.0 are slowly added to the mica suspension. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 285 g of a 32% TiCl ₄ solution are metered in. The product is after a stirring time of 15 min. filtered off, washed and dried at 110 ° C for 16 h.

The dried powder is calcined at 850 ° C under forming gas (8% H ₂ /92% N ₂ ) and sieved (63 μm). A pigment with a metallic silver sheen and a gray body color is obtained.

Example 9

Level A

100 g SiO ₂ platelets with a particle size of 5–40 μm are heated to 75 ° C in 2 l demineralized water. After this temperature has been reached, a solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is slowly metered into the pigment suspension. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 270 g of a 32% TiCl ₄ solution are metered in at this pH, the pH being kept constant with 32% sodium hydroxide solution. The pH is then raised to 7.5 and at this pH 270 g of sodium silicate solution (13.5% by weight SiO ₂ ) are slowly metered in, the pH being raised to 7.5 with 10% HCl is kept constant. A solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is then slowly metered into the suspension at pH 2.0. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 300 g of a 32% TiCl ₄ solution are metered in. After stirring for 0.5 h at pH = 1.8, the coated SiO ₂ platelets are filtered off, washed and dried at 110 ° C. for 16 h. Now the pigment is annealed at 850 ° C for 1 hour.

Level B

The annealed product is sieved (63 μm mesh size) and mixed intimately with 2% by weight of silicon powder (grain size <5 mm) and 2% by weight of anhydrous CaCl ₂ . This mixture is annealed for one hour at 850 ° C in a nitrogen atmosphere.

A silver-colored gloss pigment is obtained with blue-gray body color.

Example 10

100 g Al ₂ O ₃ platelets with a particle size of 5–60 μm are heated to 75 ° C in 2 l demineralized water. After this temperature has been reached, a solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is slowly metered into the pigment suspension. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 265 g of a 32% TiCl ₄ solution are metered in at this pH, the pH being kept constant with 32% sodium hydroxide solution. The pH is then raised to 7.5 and at this pH 270 g of sodium silicate solution (13.5% by weight SiO ₂ ) are slowly metered in, the pH being raised to 7.5 with 10% HCl is kept constant. A solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is then slowly metered into the suspension at pH 2.0. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 290 g of a 32% TiCl ₄ solution are metered in. Then the pH is raised to 2.9 with sodium hydroxide solution (32%) and 10 g of a hydrochloric acid FeCl ₃ solution (12% Fe) at a rate of 2 ml / min. metered in, the pH being kept constant at 2.9 with sodium hydroxide solution (32%). After a subsequent stirring time of 15 minutes, the product is filtered off, washed and dried at 110 ° C. for 16 hours. The dried powder is calcined at 850 ° C under forming gas (8% H ₂ /92% N ₂ ) and sieved (63 μm).

A covering pigment is also obtained metallic silver sheen and gray body color.

Example 11

100 g SiO ₂ platelets with a particle size of 5–40 μm are heated to 75 ° C in 2 l demineralized water. After this temperature has been reached, a solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is slowly metered into the pigment suspension. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 265 g of a 32% TiCl ₄ solution are metered in at this pH, the pH being kept constant with 32% sodium hydroxide solution. Then the pH is raised to 2.9 with sodium hydroxide solution (32%) and at this pH 10 g of a hydrochloric acid FeCl ₃ solution (12% Fe) at a rate of 2 ml / min. metered in, the pH being kept constant at 2.9 with sodium hydroxide solution (32%). The pH is then raised to 7.5 and, at this pH, 270 g of sodium water glass solution (13.5% by weight SiO ₂ ) are slowly metered in, the pH being constant at 7.5 with 10% HCl is held. A solution consisting of 3 g of SnCl ₄ × 5 H ₂ O in 90 g of water is then slowly metered into the suspension at pH 2.0. The pH is kept constant at 2.0 with 32% sodium hydroxide solution. The pH is then reduced to 1.8 and 285 g of a 32% TiCl ₄ solution are metered in. Then the pH is raised to 2.9 with sodium hydroxide solution (32%) and 10 g of a hydrochloric acid FeCl ₃ solution (12% Fe) at a rate of 2 ml / min. metered in, the pH being kept constant at 2.9 with sodium hydroxide solution (32%). After a subsequent stirring time of 15 minutes, the product is filtered off, washed and dried at 110 ° C. for 16 hours. The dried powder is calcined at 850 ° C under forming gas (8% H ₂ /92% N ₂ ) and sieved (63 μm). A highly opaque pigment with a metallic silver sheen and gray body color is obtained.

example

A basecoat for cars is produced according to the following recipe.

To the above acrylic melamine resin system (100 pbw), 20 pbw of silver pigment according to Example 1 are added. The resulting mass is diluted with a diluent to the spray consistency (Ford cup No. 4, 12-15 seconds) of the resulting paint. This paint is sprayed onto a substrate as a base coat. A colorless topcoat is also applied to the basecoat, which is produced according to the following recipe:

The top layer is flashed off at 40 ° C for 30 minutes and then at 30 minutes Branded at 135 ° C.

Claims (9)

Silver pigments with high hiding power based on multi-coated platelet-shaped substrates, which have at least one layer sequence of (A) a highly refractive coating consisting of TiO ₂ with a layer thickness of 5-200 nm, (B) a colorless coating with a refractive index n ≤ 1, 8 with a layer thickness of 10-300 nm, (C) a high-index coating consisting of TiO ₂ with a layer thickness of 5-200 nm, the layers (A) and (C) additionally containing an absorbent layer of oxides, sulfides, Nitrides, suboxides of the elements titanium, iron, chromium, cobalt, nickel, vanadium, molybdenum and tungsten or a metal layer made of aluminum, silver, chromium, palladium, platinum, gold, molybdenum or tungsten and / or combinations thereof. Silver pigments according to claim 1, characterized in that the platelet-shaped substrates are natural or synthetic mica, glass, Al ₂ O ₃ , Fe ₂ O ₃ , SiO ₂ or TiO ₂ platelets. Silver pigments according to claim 1 or 2, characterized in that that the layer (B) consists essentially of silicon dioxide, aluminum oxide, Magnesium fluoride or mixtures thereof. Silver pigments according to one of claims 1 to 3, characterized in that that they have the following layer sequence: Substrate + (A) (A ') (B) (C) Substrate + (A) (B) (C) (C ') Substrate + (A) (A ') (B) (C) (C') Substrate + (A ') (A) (B) (C) substratum + (A) (B) (C ') (C) Substrate + (A) (A ') (B) (C') (C) substratum + (A ') (A) (B) (C) (C'). Silver pigments according to one of claims 1 to 4, characterized in that that they only have layer sequence (A) (B) (C) (C '). Silver pigments according to one of claims 1 to 5, characterized in that that they're increasing the light, temperature and weather stability have an outer protective layer (D). Process for producing the silver pigments according to one of the Expectations 1 to 6, characterized in that the coating of the substrates wet chemical by hydrolytic decomposition of metal salts in aqueous Medium and / or in the CVD or PVD process takes place and / or by reduction from aqueous solution of metal salts. Use of the silver pigments according to Claim 1 in paints, lacquers, Car paints, industrial paints, printing inks, security printing inks, Plastics, ceramic materials, glasses and in cosmetic formulations and for the production of pigment preparations and dry preparations. pigment preparations or dry preparations containing one or more binders, optionally one or more Additives and one or more silver pigments according to claim 1.