Processing of nacreous lustruous pigments with yelow pulwerized dye with improved light resistance

BACKGROUND OF THE INVENTION The present invention relates to yellow-powdered pearlescent pigments with improved light fastness based on mica scales coated with a titanium dioxide layer, wherein an additional coloring protective layer is applied to the titanium dioxide layer and a method for producing the same. ,

Both German Patent No. 1,467,468 and the teachings of German Patent No. 2,852,585 disclose that another thin layer of chromittho hydroxide on titanium dioxide coated mica plates causes an improvement in the light fastness of the base pigments. While a favorable effect of TiO2-coated chromium hydroxide layer on anatase form is described in DBP 1 467 468, a similar effect on TiOg-coated mica in rutile form is disclosed in DOS No. 2,852,585. Both patents are directed to obtaining non-color TiOo-mica pigments. »»

However, these improved pigments are not yet fully satisfactory, so that there remains a need for pigments with improved light fastness.

In particular, light-stable pearlescent pigments with a strong gold luster are needed, but in addition, a clock of pigments with a yellow powder color and any interference colors.

It has now been found that not only by applying a chromittium hydroxide layer, but by other hardly soluble chromium compounds, the luminous stability of TiOg-containing mica pigments is improved, and in particular by further calcination of the chromium compound-coated pigments. Pigments with a yellow powder color are highly preferred in the annealing process.

The object of the invention is to: ^perle^Ťově ^les^andl^E p^igmen '^you se Hutou ^pr^áškA further coloring protective layer is applied to the titanium dioxide layer, characterized in that they are provided with a layer of lime-chromate and / or chromite-phosphate, calculated on the basis of potency. chromium trioxide 0.2 to 3% based on total pigment content.

^ExE^dThe subject matter of the invention is the perlef forest ejection method ^pigment^at with improved light fastness based on mica scales coated with metal oxygen, characterized in that the mica pigment coated with metal oxide and / or hydroxide is suspended in water, ^to suspensi se ^při^will at least 5⁰ and^of 1⁰⁰ ° C a ^hpH range between 3 and^of A solution of chromite salt and optionally phosphate salt is maintained while the pH is kept constant by the addition of hydroxyl ions, and then the coated flame is filtered, washed and dried, and ^Annealing se při ^tepLo^tin the range 5⁰⁰ and^of 1 ⁰⁰⁰ Deň: 32 ° C.

The chromite salt solution is preferably added in such a manner that after annealing, the moisture content calculated on chromium trioxide is 0.2 to 3%.

Although it has been known for about 20 years to improve the light fastness of mica pigments of TiO2 by applying a chromium hydroxide layer, the calcination of the chromium compound-coated pigments has not been considered. Unexpectedly, however, pigments, which are just as outstanding in light fastness as in the yellow powder paint, have been obtained by precisely calcining in particular. Especially with yellow interference colors, superbly brilliant gold pigments are obtained. *

In the production of the pigments according to the invention, the mica plates are first coated in the usual manner with a layer of TiO2 and possibly also with certain metal oxides. The mica flakes used as t-base pigments are generally mica flakes having a diameter of 5 to 200 µm and a thickness of 0.1 to 5 µm, which are coated with a metal oxide layer. For the preferred refractive index, mainly titanium dioxide or its aquates and / or oxide are used as the metal oxide coating.

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zirconium or its aquats. However, other colorless or possibly colored metal oxides, such as SnOg, AlgO4, can also be used together with these metal oxides.^net,A particularly frequently used pigment is, for example, a mica flake pigment in which mica flakes of 0.5 µm diameter are uniformly coated with a layer of optionally hydrated titanium dioxide, the mica surface carrying a TiO 2 layer of 50 to 500 mg TiOg per m 2. These pearly shiny pigments have different interference colors according to the thickness of the precipitated metal oxide layer.

All these pigments are known and are described, for example, in German patents and patent applications Nos. 1 467 468, 1 959 998, 2 009 566, 2 060 850, 2 106 13 13, 2 214 545, 2 215 191 and 2 522 572 Pigments with a yellow interference color are particularly preferred. Longer treatment with chromium compounds in these cases leads to magnificent gold pigments, which most favorably differ in a clear color tone from the hitherto known reddish gold pigments containing iron oxide.

As a rule, the basic pigments are products which are calcined at higher temperatures of 600 to 1000 ° C. However, it has also been found that very good results are also obtained when the chromium compound layer is applied directly after the scales have been coated with other metal oxides and then annealed. According to this simpler process requiring only one annealing, pigments are obtained which favorably differ from those of the prior art, but generally do not fully achieve the quality of the pigments double annealed after the metal oxide coating with the chromium compound. Nevertheless, the pigments which can be prepared according to this one-step process are valuable for use in certain applications. In any case, it is crucial that:. the pigment is calcined after coating with a chromium compound.

Particularly preferred base pigments are rutile / mica pigments, known from German Offenlegungsschrift No. 2,522,572, which have a layer composition such that a thin layer of TiO2 is first precipitated onto the mica surface and then alternately at least the order of SnO2 / TiO2 and then alternatively anneal at about 1000 ° C. However, these preparations can also be used without calcination as with other base pigments. The annealing then results in a rutile structure of the product coated with the sparingly soluble chromium compound.

To deposit a layer containing a chromium compound, the base pigment having the desired interference color is suspended in an aqueous solution and coated with a layer of chromium hydroxide and / or chromium phosphate. The deposition conditions can vary within wide limits. It is only desirable that the sparingly soluble chromium compound formed in suspension by chemical reaction, hydrolysis or reduction is formed per unit of time in such an amount that it normally settles on the pigment surface without causing a significant amount of free precipitated particles to form in the suspension.

The formation of a sparingly soluble chromium compound can be based on both chromium salts and chromium compounds. When chromium compounds are used, the pigment suspension may either contain the ions (hydroxyl and / or phosphate ions) required for precipitation, allowing the chromium salt solution to flow slowly, or hydroxyl and / or phosphate ions may be slowly added to the pigment suspension containing the chromium salt.

However, both the chromium salt solution and the precipitate-containing solution can also be added simultaneously to the pigment suspension, while maintaining the pH constant as a rule, or the ions needed for precipitation by a chemical reaction, such as homogeneous, can be formed in the pigment suspension. hydrolysis.

However, chromium ions can also be formed in situ from chromium compounds. The chromium salt solution is mixed in the pigment slurry with a reducing agent such as hydrazine or hydroxylamine, either with one component added and the other is added, or both components are slowly added to the pigment slurry simultaneously.

The pH in the pigment slurry should be above 3, with values ​​in the range of 4.5 to 9 being preferred. A pH value which would vary with the addition of the acidic chromium salt solution in a strong acidic range alone may be used. each base: ammonia (in solution or gaseous), sodium hydroxide solution or potassium hydroxide solution. Preferably, ammonia is used.

Each soluble chromite salt or chromate is used to deliver chromium ions.

Preferably, a solution of chromium chloride or chromium alum or potassium chromate is used. If phosphate precipitation is to be carried out, both orthophosphoric acid as well as its primary, secondary and tertiary salts and polymeric phosphates can be used. For example, in addition to phosphoric acid, ^ 12 HgO, РадР₂°? xx 7 H2O a (ΝθΡΟ₃)_χ.

The precipitation can be carried out at any temperature between the freezing point and the boiling point of the suspension. It has been shown, however, that coagulation may occur at relatively low temperatures. It is therefore advantageous^dwork at increased^E toploto eg 50 a^of 100 ° C, in particular 5 ° a^of Low: 14 ° C. However, also at a different temperature, a good quality precipitation is usually achieved.

It is not necessary for a pure chromium hydroxide or chromium phosphate precipitate to form on the pigment particles. They can be applied as mixtures of chromium (III) hydroxide and chromium (III) phosphate, as well as mixtures with other, preferably colorless, metal oxides to be deposited. cell simultaneously with the chromium compound or in a thin layer before or after.

It is also possible to alter the chemical composition of the precipitate formed by subsequent reaction. Nepiř. the chromium hydroxide precipitate may be partially or completely converted by reacting the pigment particles coated with the precipitate with a phosphate-containing solution to chromium phosphate without losing its effectiveness.

Minor amounts of chromium compound are sufficient to achieve the improved light fastness of the present invention. Already at 0.5% by weight (calculated as 0Γ)₂θ₃ and based on total pigment) is a provable stabilizing effect; with increasing chromium content occurs^pO ^annealingyet further enhanced ^barevn^E saturation produced^éhwhich can help very nice effects. Above 4% by weight of chromium, the total chromium cannot react with titanium dioxide to yellow chromium titanate, but will remain, for example, as chromium oxide,^of will show a green tone in powder color p^igmentu.

While this may serve for special effects, it is generally not desirable in the present invention to seek to improve the light fastness while obtaining pigments with a yellow powder color, especially magnificent gold pigments. The pigments according to the invention therefore preferably have a chromium compound content in the range of 0.2 to 3% by weight calculated as.

After coating of the basic pigments with chromium hydroxide and / or chromite with chromite, the pigments are further processed in a conventional manner. As a rule, they are filtered, washed and dried. In contrast to the known treatment with chromium hydroxide coating, the temperature is then calibrated⁵⁰⁰ to 1 ⁰⁰⁰ ° C, yield 7⁰⁰ to ⁹⁰⁰ Deň: 32 ° C. ^ i this^kaLc^andilci^{, k}This is usually carried out for half an hour, optionally removing any possible chromium (III) hydroxide and other hydroxides and aquates, and reacting with TiO2 to form a superbly yellow pigment color.

Thus obtained^toan^{é pig}ment^y have ^tohutoto t^OThe light-retardant properties of the non-flame retardant compositions of the prior art are greatly improved so that valuable novel pigments are obtained by the process according to the invention. The pigments according to the invention can be used as hitherto known pigments, also, for example, as additives for plastics, paints or varnishes, but especially in cosmetics. Due to the improved light fastness, all applications in which the pigments are exposed to external waves, in particular, for example in automotive paints, are also preferred. Parts and percentages in the following examples are intended to be monotonous unless otherwise indicated.

Example 1

120 g of mica pigment coated according to the method of DOS 2 522 572 with alternating layers 'ΓΙ ^ /' ^^ / 'ΤΙ ^ / ^^ /' Τί ^ ^and Then freaked out ^při 9⁰⁰ ° C, with yellow thermo-color (plate size 10 to 60 µm, mica content 50.8%, Ti0 content₂ 42.2%, SnO content₂ 7%) with sus^pends in ^{2,4 1} vo^dy and sow on ⁷⁵ Deň: 32 ° C. Sus^pThe enzyme was adjusted to pH 6.0 with a 9% ammonia solution and a solution of 0.8 g of Kg / H2 O in H2 O (30 ml) was added over 15 minutes while maintaining the pH by adding 5% aq. The solution is constant. Then I still miss³⁰ minutes at ⁷⁵ ° C, filtered ^{, p}wash and dry^and and 3⁰ minutes ^Annealing at ⁸⁰⁰ Deň: 32 ° C. Yellow is obtained^E armed ^pigment with gold shiny ^barvou a ^0,1 % chromium content, calculated as CrgO4.

In an analogous manner, the same base pigment is coated with an amount of chromium hydroxide such that, after annealing, the content of C? In an aging test, in which pigments processed into PVC are exposed to high humidity and tl.freo0am of light, it is shown that pigments coated with 0.1 % CrO4 mm exhibit a less pronounced discolouration than the base pigments and that already at 0.5% a change in coloring can hardly be detected. At the same time, it is clear that products with a CrgO content of from 4% mm &amp; lt; 2 &amp; gt; green tone.

Example 2 ^WITHuspenze 1^{20 May G} základníirn ^Fri^^GFrom the example 1 in FIG ^{2,4 1} vo^dy Lies to ⁷⁵ ° C in 50 ml of water, keeping the pH constant by the addition of 5% ammonia. After 30 minutes of stirring, half of the suspension is filtered, prommye, dried and calcined for 30 minutes at⁸⁴⁰ Deň: 32 ° C. К dru^hee half of the suspension is ex^idá rozto^to 1^,5 ^G Т ^ НЮд. 12^HgO in 10 ° ml in^dy and after 3⁰ minutác^h se od^diltrtje^, and dried 3⁰ minutes ^Annealing at ⁸⁴⁰ Deň: 32 ° C. ^Oba ^eventThe tubes show a fresh gold shine and contain 0.5 $ C ^ O ^.

In the light fastness test, no difference between the two preparations can be detected, but both preparations are considerably more stable than light preparations.

Example 3

The method of DOS 2,522,572 is coated with potassium mica having a plate size of 5 to 200 µm at 75 °^C and ^hodiotě ^{pH 1} to ^2,5 nej^prve vrs ^ ou ^Tand^Og with a thickness of 5 nm^{, p}then a layer of SnOg and a thickness of 5 to 10 nm, a layer of TiOg of a thickness of 45 to 55 nm, again a layer of SnOgO of a thickness of 5 nm and finally a layer of TiOg until a yellow interference color is obtained. The pH is then adjusted to 6, and both the chromium chloride solution and the ammonia solution are added simultaneously, keeping the pH at a constant value of 6. After precipitation of a chromium hydroxide layer corresponding to 0.1% of chromium trioxide, based on the total. gment, with pigment from^diltrtje^, ^ o ^ ye, dried and ^phive ^hO^din^y se ^Annealing at ⁸00 Deň: 32 ° C

In an analogous manner, the same basic pigment is coated with a chromium hydroxide masculinity to give a content of C ^ gO ^ ^ 0, 5, 1.0, 4.0 and 8% after annealing. In an aging test in which PVC-treated pigments are exposed to high humidity and ultraviolet light, the pigments coated with 0.1% CrgO have already had less discolouration than the basic pigments and that even at 055% Cr2O4 content, discoloration can hardly be detected. At the same time, it is clear that products containing CrgO₃ from 4% have a bright green ton.

Comparable results are obtained when it is coated with a CrPO6 layer instead of Cr (OH) 6 and then calcined.

For example, 4 g of potassium mica having a plate size of 10 to 60 µm is suspended in water and, according to the method of DOS 2 522 572, coated with alternate TiOg / SnOg / TiOg layers until a silver interference color is obtained. Thereafter, the suspension is adjusted to pH 6.0 with 10% sodium hydroxide solution, and a solution of 0.44 g of KCr / SOg / g · 4 HgO in 30 ml of water is added slowly, keeping the pH constant at 5 by concurrent addition of 5% ammonia solution. It is then filtered, washed, dried and calcined at 820 ° C for 30 minutes. A silvery shining pigment with a yellow powder color and a very good light fastness is obtained which contains 0.2% &lt;*^Γ2θ3 *

Example 5 g of potassium mica with a plate size of 10 to 60 μ ee is suspended in 1.5 l of water and, according to the method of DOS 2 522 572, it is coated until a green interference color is obtained. Thereafter, the suspension is adjusted to pH 6.0 with 10% sodium hydroxide solution, and a solution of 1.8 g КСг / ЗОд / 2.12 H 2 O in 100 ml of water is slowly added while maintaining the pH constant at 5 by adding 5 # ammoniacal solution. value. The pigment is then filtered, washed, dried and calcined at 800 for 30 minutes^QC. A pigment was obtained with a yellow powder color and a greenish yellow interference color with 0.3% CrgOy content

Example 6 g of potassium mica having a particle size of 10 to 60 µm is suspended in 1.6 L of water and coated according to the method in DOS 2 522 572 until a red interference color is obtained. Then the suspension is adjusted to pH 5.8 and a solution of 1.04 g KCr (SO4) is added.₂* 12 H₂0 in 60 ml of water, maintaining the pH constant with a 5% ammonia solution.

It is then filtered, screened, dried and calcined at 800 ° C for 30 minutes. * A reddish glistening pigment with a yellow powder color having a high light fastness and a 0.2% CrgOy content is obtained.