Goniochromatic gloss pigments based on silicate pigments coated with titaniumdioxide, which are heat treated in a reducing atmosphere

The present invention relates to novel goniochromatic luster pigments on the basis of in a reducing atmosphere heated, titanium dioxide-coated silicatic platelets which at least one layer packet of<sl><li>A) a colorless coating having a refractive index n ≤ 1.8 and</li><li>B) a colorless coating having a refractive index n ≥ 2.0 exhibit.</li></sl>

Furthermore, the invention relates to the preparation of these luster pigments and to their use for coloring paints, printing inks, Inks, plastics, glasses, ceramic products and Decorative cosmetic preparations.

Luster or effect pigments are used in many areas of technology used, for example in automotive coatings, decorative Coating, plastics pigmentation, in paints, Printing inks, especially security printing inks, and in the Cosmetics.

Their optical effect is based on the directed reflection of Light at predominantly sheetlike, mutually parallel oriented, metallic or strongly refractive pigment particles. produce Depending on the composition of the pigment platelets Interference, reflection and absorption phenomena angle-dependent color and lightness.

Due to their optical effects nichtkopierbaren win this Pigments also increasingly important for the production of Forgeryproofness as banknotes, checks, Debit cards, credit cards, tax stamps, postage stamps, rail and Airline tickets, phone cards, lottery tickets, gift certificates, ID cards and identification cards.

Markings, which were made with the effect pigments, and the absence of these markings or their alteration, For example, in a color copy (disappearance of color flops and Glitter), are safe unaided, naked eye recognizable and thus allows easy identification of the Original from the copy.

Of particular interest are goniochromatic luster pigments, which an angle-dependent color change between several intensive Interference colors and hence an attractive color play show.

Heretofore, a number of goniochromatic luster pigments metallic base known about physical vapor deposition (US-A-3,438,796 and 5,135,812) or by coating Metal platelets by gas phase decomposition of volatile precursor (CVD = chemical vapor deposition) or by wet chemical Coating the metal platelets (EP-A-668 329 and EP-A-708 154) getting produced.

Goniochromatic luster pigments based on transparent, silicate Substrates coated or iron (III) oxide platelets are in DE-A-196 18 569, EP-A-753 545 and the earlier German Patent Application 198 08 657.1 described.

The known luster pigments differ from the Pigments of the invention by the nature of the substrate material and / or the applied coatings.

The invention had the object of further goniochromatic provide luster pigments having advantageous Application properties are characterized and the coloristic expand opportunities.

Accordingly the goniochromatic initially defined Luster pigments found.

Furthermore, a method for preparing these luster pigments found which is characterized in that the coatings (A) and (B) independently of one another either wet-chemically by hydrolytic decomposition of organic or inorganic metal compounds or by gas phase decomposition of volatile, organic or inorganic metal compounds on the heated in a reducing atmosphere, titanium dioxide-coated silicatic platelets applied.

Finally, the use of the luster pigments of the invention for coloring paints, printing inks, inks, plastics, Glasses, ceramic products and preparations of the decorative cosmetic.

based The goniochromatic luster pigments of the invention on heated in a reducing atmosphere, titanium dioxide coated en silicatic platelets which multiple coating a exhibit.

As silicate platelets are particularly bright or white mica suitable, and flakes of preferably wet ground muscovite are particularly preferred. Of course can also use other natural micas, such as phlogopite or biotite, artificial mica or talc or glass flakes as a starting material serve.

The silicate platelets having a substantially from Titania existing layer is that as children Components (generally &lt;5 wt .-%), further preferably colorless metal oxides such as tin dioxide, zirconium dioxide, aluminum oxide oxide and silicon dioxide.

The size of the silicate platelets is not critical per se and can be matched to the particular application. In the Usually have platelet average largest diameters of about 1 to 200 microns, particularly about 5 to 100 microns, and thicknesses of about 0.1 to 1 .mu.m, in particular about 0.5 .mu.m. Their specific free Surface area (BET) is usually from 1 to 15 m²/G, particular from 3 to 12 m²/G.

The thickness of the TiO₂Layer determines the reflection color of the tile and is preferably 50 to 100 nm (silver) or 300 to 340 nm (blue; optical layer thicknesses).

The luster pigments of the invention are the titania-coated Silicate platelets in a reducing Gas atmosphere heated.

As reducing gases here are, for example, ammonia gas, hydrogen, volatile hydrocarbons (especially C₁-C₄alkanes) and mixtures thereof. These gases are preferably mixed Inert gases such as nitrogen, is used (see. EP-A-735 115 and amongst others, referred to EP-A-322 071).

Preferred reducing gases are ammonia gas and mixtures of Ammonia gas with volatile hydrocarbons such as methane, ethane and / or propane, for which a volume ratio of about 95: 5 to is recommended 70:30. The nitrogen content in the total amount of gas of each particularly preferred reducing gas / inert gas mixtures is preferably up to 90 Vol .-% and at 10 to 60 Vol .-%.

Suitable reduction temperatures are in the reduction with Ammonia gas is preferably 750 to 850 ° C and in the implementation Ammonia gas / hydrocarbon mixtures preferably&gt; 800 to 900 ° C.

When reducing blue, reduced titanium species with Oxidation Numbers &lt;4 to 2 (lower titanium oxides such as Ti₃O₅, Ti₂O₃ to formed to TiO, titanium oxynitrides and titanium nitride). Usually be 5 to 100 wt .-% of the originally present titanium dioxide reduced.

Reduced titania-coated mica pigments are commercially available under the name Paliocrom®.

The reduced titanium dioxide-coated silicatic platelets are highly refractive. Your refractive index n is generally ≥ 2.0, preferably ≥ 2.4. They are visible light, depending of the considered wavelength substantially permeable virtually impervious to.

The luster pigments of the invention have a colorless low refractive Coating (A) in combination with a colorless high refractive coating (B) on. You can buy several same or various combinations (layer packets) (A) + (B) but contained, is preferably covered with a single Layer packet (A) + (B).

The colorless low refractive coating (A) has a Refractive index n ≤ 1.8, preferably ≤ 1.6, and in the visible Wavelength range an absorption constant k = 0th

The layer material (A) are any low-index colorless substances that a durable film on the Substrate chip may be applied, wherein inorganic Materials are preferred.

Especially suitable are for example metal oxides and metal oxide hydrates such as silicon oxide, silicon oxide hydrate, aluminum oxide, aluminum oxide hydrate and mixtures thereof, with silicon oxide (hydrate) is preferred.

The geometric layer thickness of the coating (A) is generally 50 to 800 nm, preferably 100 to 600 nm. Since the Layer (A) essentially determines the interference colors of the invention Pigments determines it has a particularly pronounced Farbenspiel facing and therefore preferred luster pigments only one layer packet (A) + (B), a minimum layer thickness of about 200 nm. If multiple (eg, 2, 3 or 4) layer packets (A) + (B) present, the layer thickness of (A) preferably from 50 to 200 nm.

With increasing layer thickness of (A) are the dry pigment powder in the plan several times in succession, the interference colors watching Blue-green-gold-red-violet, with starting with the blue of the second order, the angular dependence of the hue increases. However, the interference colors are dry State visible and disappear when wet or in Paint completely. is The additional coating with (B) the optically variable layer visible also in paints.

The colorless high refractive coating (B) has a refractive index n ≥ 2.0, in particular ≥ 2.4, and in the visible wavelengths. range an absorption constant k = 0th

The layer material (B) are all highly refractive colorless Substances which occupied a durable film on the with (A) Iron oxide platelets may be applied, is suitable.

Particularly suitable besides metal sulfides such as zinc sulfide are also here especially metal oxides and metal oxide hydrates, such as titanium dioxide, Titanium oxide hydrate, zirconium dioxide, zirconium oxide hydrate, Tin dioxide, tin oxide hydrate, zinc oxide, zinc oxide hydrate and their Mixtures with titanium dioxide and titanium oxide hydrate and their Mixtures with up to about 5 wt .-% of other metal oxides, in particular tin dioxide, are preferred. Titanium dioxide can also used together with low refractive colorless metal oxides , when the refractive index of these blends is ≥ 2.0.

The coating (B) preferably has a lower layer thickness than the coating (A). Preferred geometric layer thicknesses are for the coating (B) about 5 to 50 nm, particularly 10 to 40 nm.

The inventively preferred, essentially of titanium dioxide existing coating (B) preferably has an optical Layer thickness of ≤ 100 nm, ie in itself and silvery still shows no interference effects.

The luster pigments of the invention are distinguished by good Hiding power, high brightness values, intense blue color with pronounced goniochromaticity and "silky appearance" in applique shape and the uniform, homogeneous and filmy build their interference-capable coating and thus extend the range of known luster pigments advantageously.

In the process for producing the luster pigments of the invention the coatings (A) and (B) independently each other either wet-chemically by hydrolytic decomposition organic or inorganic metal compounds or by Gas phase decomposition (CVD) of suitable volatile metal compounds applied.

Of course, both approaches can arbitrarily for preparing the individual layers are combined. If both applied coatings wet chemically, so it is unnecessary to Intermediate drying of the coated with (A) substrate wafer; is the same reaction medium used, as can also the Intermediate isolation omitted. Accordingly, the intermediate isolation usually also in the implementation of both Coating steps are not required by the CVD method.

layers to produce the silicon and / or aluminum oxide (hydrate) (A) are the wet chemical and the CVD preparation route equally suitable.

In the wet-chemical variant may be advantageous according to the EP-A-668 329 method described proceed in the organic silicon and / or aluminum compounds in which bound the organic radicals bonded via oxygen atoms to the metal are, in the presence of the substrate flakes and an organic Solvent in which the metal compounds soluble are and which is miscible with water, are hydrolyzed.

The preferred embodiment consists in the hydrolysis of the Metal alkoxides (especially tetraethoxysilane and aluminum triisopropoxide) in the presence of an alcohol (especially isopropanol or ethanol) and aqueous ammonia as a catalyst.

The process is referred to in EP-A-668 329 The method described preferably followed in which the substrate wafer, Isopropanol, water and ammonia submits this Mixture with stirring at 40 to 80 ° C, especially 60 to 70 ° C, heated and a solution of the metal in isopropanol continuously metered. After stirring for about most 1 to 15 h the mixture is cooled to room temperature and isolated by filtration and the coated pigment Dry.

Silicon oxide (hydrate) coatings (A) can also advantageously starting from alkali metal silicates, especially sodium silicate, be generated.

The process involves the expediently so that the substrate wafer suspended in water, the suspension to about 20 to 100 ° C, preferably 40 to 80 ° C, heated with a base (especially an alkali metal such as potassium hydroxide or Caustic soda) a pH of usually 4 to 9, preferably 6.5 to 8.5, particularly about 7.5, is established and the Alkalimetailsilikatlösung with simultaneous addition of an aqueous inorganic acid such as hydrochloric acid, in particular a dilute Hydrochloric acid, added to maintain a constant pH. Possibly stirred for a few minutes to up to 2 hours.

In CVD-variant, according to the described in EP-A-708 154 Methods described procedure. Here are silanes contain at least one alkanoyloxy in the gas phase with Water vapor and, when the silanes and alkyl or phenyl exhibit, oxygen in the presence of the fluidized substrate platelets decomposed.

Preferred silanes have alkoxy and alkanoyloxy, is more preferably di-tert. -butoxydiacetoxysilan.

To carry out the CVD variant is recommended as generally customary for CVD process using a fluidized bed reactor. The substrate plates are in the reactor under fluidization (Turbulence) with an inert gas such as nitrogen fluidized to the desired reaction temperature (typically 100 to 600 ° C, preferably 150 to 300 ° C), silane and water vapor (And optionally oxygen) are then using inert Carrier gas streams (advantageously part-streams of the fluidizing gas) from upstream vaporizer vessels introduced via separate nozzles, the silane concentration being advantageously carried out at ≥ 5 vol .-%, preferably ≤ 2 Vol .-%, based on the total amount of gas is in the reactor maintained. The amount of water vapor should at least the stoichiometrically for the hydrolysis of the silane required amount correspond, but preference is given 10 to 100 times that amount.

Also the deposition of coatings (B) is on both the CVD way and wet chemically possible.

For the CVD variant suitable as starting compounds particularly, metal, metal halides, and organometallics. Preference is given to those compounds which at temperatures up to 200 ° C have a sufficiently high vapor pressure to a to ensure simple vaporization possible without decomposition.

The alcoholates aromatic alkoxides such as phenoxides come and Benzylalkoholate and aliphatic, especially C₁-C₄alcoholates as n-, iso- and tert-butanolates, preferably methanolate and Ethanolates, and in particular n-and iso-propoxides and also their Mixtures.

When metal halides the chlorides are preferred.

Organometallics can eg metal, particularly those with up to 4 carbon atoms in the alkyl chain, Metallalkenyle, metal aryls, be Metallarylalkyle and Metallalkylalkenyle.

Examples which may be mentioned as suitable starting materials:<ul><li>Alkoxides such as titanium tetraethoxide, titanium tetra-n- and -iso-propanolate and in particular mixtures of titanium tetraethoxide and titanium tetraisopropoxide, preferably in the Molar ratio of about 1: 1, which is characterized by low evaporation temperatures (120 ° C) and low decomposition temperatures (Hydrolysis with steam at about 200 ° C possible) distinguished, and zirconium n- and isopropoxide;</li><li>Halides such as titanium tetrachloride, zirconium tetrachloride and tin tetrachloride;</li><li>Organyl as tin tetramethyl, tin tetra-n-butyl and zinc diethyl.</li></ul>

The decomposition of these metal compounds filmy about to the coated with (A) substrate wafer depositing metal oxide layers is advantageously carried out also in a fluidized bed reactor, and in the case of the alcoholates and water vapor If desired, air, in the case of halides and water vapor in the Case of Organyl oxygen used as an additional reaction gas becomes. Suitable decomposition temperatures are in the Usually 100 to 600 ° C, preferably 150 to 300 ° C (alcoholates) 150 to 350 ° C (halides) or 300 to 500 ° C (Organyl).

coatings Analogous to the metal oxide (hydrate) (A), the Metal oxide (hydrate) layers (B) are also wet-chemically by Hydrolysis of metal (eg of titanium ethoxide) in alcoholic medium or preferably by hydrolysis of inorganic Metal salts, in particular halides, preferably be applied by chlorides, in aqueous suspension.

For deposition of the preferred titanium dioxide layers (B) can be advantageously proceed by the with an aqueous suspension (A) -coated substrate platelets to usually 50 to 100 ° C, preferably 70 to 80 ° C, heated with a base (especially an alkali metal such as potassium hydroxide or sodium hydroxide) a pH of generally 0.5 to 5, preferably 1.5 to 2.5, in particular about 2.2, is established and a titanium tetrachloride solution with simultaneous addition of base to maintain a constant pH metered.

Both the deposited from the gas phase and the wet-chemical Titanium oxide (hydrate) is crystallized incompletely. The amorphous portions can by calcination of the isolated (and dried) pigment in crystalline form, usually in the Anatase, are transferred. These heating the Pigment generally about 1 to 4 hours at 400 to 1000 ° C. Should the Titanium dioxide coating (B) after calcination in the rutile modification present, so it is recommended that the titanium oxide (hydrate) by co-depositing tin oxide (hydrate) with about 0.5 to 10 wt .-% to dope tin dioxide, which comprises Formation of rutile favors.

With the help of the manufacturing method according to the invention can multiply coated luster pigments in a simple manner in large Quantities are produced reproducibly. There are completely pigment particles coated with a high quality of the individual Coatings (homogeneous, filmlike).

The luster pigments of the invention are advantageous for many purposes, such as the coloring of plastics, glasses, ceramic products, decorative cosmetic preparations and in particular paints, inks and printing inks, also Security inks. When applying the pressure are all conventional industrial printing methods such as screen printing, gravure printing, Bronze printing, flexographic printing and offset printing are suitable.

For these purposes can be the invention Pigments can also advantageously in admixture with transparent and opaque white, colored and black pigments and also conventional Luster pigments based on metalloxidibeschichteten Mica and metal pigments and known goniochromatic using luster pigments.

Examples

Manufacture and use of luster pigments according to the invention

To assess the coloristic properties of the pigments obtained 0.4 g pigment in 3.6 g of a polyester mixing varnish with 21 wt .-% solids and stirred for 2 minutes in a Red Devil® dispersed. With a blade (200 .mu.m wet film thickness, simple doctoring) were then the pigmented Paints made on a black and white cardboard. The measurement of the CIELAB values ​​were after drying the film with a Gonio spectrophotometer Multi Flash (Fa. Optronics) at a Angle difference of 20 ° to 115 ° to the gloss angle over black Underground. The reported color coordinates relate to the Illuminant D65. L is the lightness, a * the red or Green component and b * the blue or yellow portion, H is the hue angle and C the chroma. In this measuring arrangement is only part of the Color play, namely essentially the color of paint in Supervision, detected.

example

<sl><li>a) 100 g of a blue silver, ammonia-reduced, TiO₂Mica pigment (Paliocrom® Blue Silver L6000, BASF) were slurried in 1.5 liters of isopropanol, first with 400 g Water and 40 g of 25 wt .-% aqueous ammonia solution and after heating to 60 ° C in about 24 hours with a mixture of 345 g of tetraethoxysilane and 345 g of isopropanol. After stirring for about 2 hours and cooling the suspension the product was filtered, washed with isopropanol and dried under reduced pressure at 80 ° C. The dried SiO₂-coated pigment (203 g) indicated the air a violet, invisible in the paint body color.</li><li>b) A suspension of 100 g of the SiO₂-coated and dried Product in 1350 ml of water was heated to 75 ° C and then to a pH value of 2.2 with 32 wt .-% hydrochloric acid set. Then, 120 ml of an aqueous titanium tetrachloride solution was (200 g TiCl₄/ L) was added in 120 minutes. By simultaneous addition of 32 wt .-% sodium hydroxide solution was the pH kept constant at 2.2. After stirring 30 min and cooling the suspension the product was filtered, washed with water and dried under reduced Pressure at 80 ° C dried.</li></sl>

The pigment obtained had a silicon content of 26.1 wt .-% and a titanium content of 12.9 wt .-%. Applied in varnish, showed the pigment good opacity and an angle-dependent color play of intense greenish blue to violet at a high brightness level.

Colorimetric data of pigment obtained:<tables><table><tgroup cols="6"><tbody><row><entry align="center">Measuring angle in °</entry><entry align="center">L</entry><entry align="center">a *</entry><entry align="center">b *</entry><entry align="center">C</entry><entry align="center">H</entry></row><row><entry align="center">20</entry><entry align="center">74.2</entry><entry align="center">-11.1</entry><entry align="center">-35.7</entry><entry align="center">37.4</entry><entry align="center">252.7</entry></row><row><entry align="center">25</entry><entry align="center">69.9</entry><entry align="center">-12.1</entry><entry align="center">-30.2</entry><entry align="center">32.5</entry><entry align="center">248.2</entry></row><row><entry align="center">35</entry><entry align="center">49.6</entry><entry align="center">-11.1</entry><entry align="center">-21.5</entry><entry align="center">24.2</entry><entry align="center">242.7</entry></row><row><entry align="center">45</entry><entry align="center">39.5</entry><entry align="center">-8.5</entry><entry align="center">-17.2</entry><entry align="center">19.2</entry><entry align="center">243.7</entry></row><row><entry align="center">55</entry><entry align="center">33.2</entry><entry align="center">-6.2</entry><entry align="center">-15.1</entry><entry align="center">16.3</entry><entry align="center">247.7</entry></row><row><entry align="center">65</entry><entry align="center">28.3</entry><entry align="center">-4.1</entry><entry align="center">-13.5</entry><entry align="center">14.1</entry><entry align="center">253.3</entry></row><row><entry align="center">75</entry><entry align="center">37.3</entry><entry align="center">-3.7</entry><entry align="center">-13.2</entry><entry align="center">13.7</entry><entry align="center">254.4</entry></row><row><entry align="center">115</entry><entry align="center">24.1</entry><entry align="center">-1.9</entry><entry align="center">-13.1</entry><entry align="center">13.2</entry><entry align="center">262.0</entry></row></tbody></tgroup></table></tables>

Comparative example

For comparison, the colorimetric data of SiO were₂- And molybdenum coated Mica pigment Paliocrom® Blue Silver L6000 from Example 4 of EP-A-753 545 determined.

This pigment had a titanium content of 7.7 wt .-%, a Silia Conversely maintenance of 29.6 wt .-% and a molybdenum content of 2.6 wt .-%. Applied in varnish, this pigment also showed good hiding power, but only an angle-dependent color play from greenish blue to violet with lower color strength and at a significantly lower level of brightness.

Colorimetric data of pigment obtained:<tables><table><tgroup cols="6"><tbody><row><entry align="center">Measuring angle in °</entry><entry align="center">L</entry><entry align="center">a *</entry><entry align="center">b *</entry><entry align="center">C</entry><entry align="center">H</entry></row><row><entry align="center">20</entry><entry align="center">58.2</entry><entry align="center">-8.8</entry><entry align="center">-22.3</entry><entry align="center">23.9</entry><entry align="center">248.5</entry></row><row><entry align="center">25</entry><entry align="center">48.7</entry><entry align="center">-9.1</entry><entry align="center">-18.6</entry><entry align="center">20.7</entry><entry align="center">244.0</entry></row><row><entry align="center">35</entry><entry align="center">33.3</entry><entry align="center">-8.2</entry><entry align="center">-12.3</entry><entry align="center">14.8</entry><entry align="center">236.1</entry></row><row><entry align="center">45</entry><entry align="center">23.0</entry><entry align="center">-6.6</entry><entry align="center">-8.4</entry><entry align="center">10.7</entry><entry align="center">231.7</entry></row><row><entry align="center">55</entry><entry align="center">16.4</entry><entry align="center">-4.9</entry><entry align="center">-6.4</entry><entry align="center">8.1</entry><entry align="center">232.3</entry></row><row><entry align="center">65</entry><entry align="center">11.5</entry><entry align="center">-3.0</entry><entry align="center">-5.4</entry><entry align="center">6.1</entry><entry align="center">241.0</entry></row><row><entry align="center">75</entry><entry align="center">10.6</entry><entry align="center">-2.6</entry><entry align="center">-5.1</entry><entry align="center">5.7</entry><entry align="center">242.9</entry></row><row><entry align="center">115</entry><entry align="center">7.2</entry><entry align="center">-0.8</entry><entry align="center">-3.9</entry><entry align="center">4.0</entry><entry align="center">259.0</entry></row></tbody></tgroup></table></tables>