Processing of nacreous lustruous pigments

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to pearlescent-based mica platelets coated with titanium dioxide having a chromium (III) oxide coating and a process for their manufacture.

Such pigments are known, for example, from German Patent No. 1 467 468. For the preparation of these pigments, mica platelets coated with metal oxide are provided with a coating of chromium hydroxide, which during drying and calcining of the pigment. converted to a chromium oxide layer. , V

In order to do this ^p±^gmeiⁿ with an optic pearlescent 3-es, is needed, and^by the primary particles forming the layer had a size below 10 nm, since larger particles scatter in the light produced, which is detrimental to the interference effect affecting the pearl luster.

While the deposition of the chromium hydroxide layer can be controlled so as to produce a relatively thick, smooth hydroxide layer on the support, it has not been possible to produce it at the time. calcined closed layer of chromium trioxide. Generally, by calculating by heat shrinkage, conversion of the hydroxide to the oxide results in granular coatings which greatly deteriorate the gloss of the formulation. Also, no interference phenomena can occur in the tear-like layer of chromium trioxide, so that the coloring layer of chromium trioxide rather damages the base pigment plate.

It has hitherto not been possible to deposit chromium oxide on pearlescent pigments in the amount required for intense green coloring in the closed layer and the fineness required to obtain high gloss pigments with the desired interference effects.

It is therefore an object to find a method according to which pearlescent pigments could also be coated with a layer of chromium trioxide of sufficient thickness without adversely affecting the gloss and interference effects.

This object has been achieved by the present invention. In particular, it has been found that the chromium hydroxide layer, which is coated with phosphate ions prior to annealing, is thickened during calcination to a dark transparent coating, producing pearlescent pigments with a green powder color and a very good gloss. Unexpectedly, this effect is already achieved with a relatively small amount of phosphate.

The invention therefore relates to pearlescent pigments based on mica platelets coated with an oxide of nitrite, which have a chromium oxide coating, characterized by Ί-ί », ^ofthat the layer of the roma is elespon ^0,05 mole of phosphonium ion, based on 1 mole of chromium compound in the layer.

The subject of the invention is ^tand^ké způso^b production of pearls^Ťov^E 1г ^ 1у ^ pigment^at with green ^pr^áškby coating the mica pigment with a titanium dioxide layer with another chromium hydroxide coating and calcining the pigment thus obtained, characterized in that the pigment, after coating with chromium hydroxide, is contacted with an aqueous solution containing at least 0.05 moles of phosphate ions, based on per mole of chromium compound in the layer.

St^ýhO^dou obsatouje roz^tO^to and^lespo^{ň 0,1} mole of phosphate ions per mole of c^hromit^Ecompounds.

The advantage of the pigment according to the invention is that almost any thickness of chromium trioxide can be deposited without substantially reducing the gloss. On the contrary, the chromium trioxide layer contributes greatly to the burn-out of the radiation due to its smooth uniform structure and small particle size according to the surface of the top.^barvy, ^pspeech^of pay opticians from^ákhe^y for interference in a thin layer and wherein the intrinsic color of chromium trioxide acts as an additional filter. ·

Because of the intrinsic color of the chromium oxide layer, the pearlescent pigments of the invention have a green powder color, while the interference color is formed from the overall thickness of the metal oxide layer and the chromium oxide layer. By selecting the base pigment and the thickness of the chromium oxide layer, both the desired interference color as well as the color saturation of the green powder can be arbitrarily controlled.

Any mica pigment coated with metal oxide may serve as the base pigment. Preferably, however, a mica pigment coated with titanium dioxide is used. The mica flake pigments used as base pigments are generally mica flake with a diameter of 5 to 200 µm and coated with a layer of metal oxide. For the preferred refractive index, titanium dioxide or its aquates and / or zirconium dioxide or its aquates are preferably used as the metal oxide coating. However, other colorless or possibly also colored metal oxides such as SnO2, AAjO or FegOy may also be used with or alternatively with these metal oxides.

An especially frequently used pigment is, for example, a micaceous flake pigment in which micaceous flakes having a diameter of 5 to 50 microns and a thickness of 0.5 microns are stoichiometrically coated with an optionally hydrated titanium dioxide layer, the mica surface carrying a TiO2 layer. up to 500 mg TiOg / m ·. These pearlescent pigments have different interference colors, depending on the layer thickness of the precipitated metal oxide.

Usually one^and o prodι^atyou too^{, kt}er^E of calenified at higher temperatures ⁶⁰⁰ and^of 1 ⁰⁰⁰ ° C ·. All these pigments are known and are described, for example, in German patents 14 67 468, 19 59 998 and 20 09 566 and in German Laid-open Nos. 20 60 850, 21 06 613, 22 14 545, 22 15 191, 22 44 298, 23 13 331, 23 13 332, 24 29 762, 25 22 572, 25 22 573 and 26 28 353.

Coating the base pigment with chromite will shift the interference color of the base pigment to a range that corresponds to a higher optical thickness of the layer. This results in particularly attractive mixed colors, especially when using base pigments with a blue, green or silver glossy color. In principle, however, bases with a yellow or red interference color are also suitable for coating the process according to the invention with preparations having a yellow or red interference color. especially for cosmetic purposes.

The base pigments are coated with chromium hydroxide by a known method. Because stable aqueous chromium salt solutions are strongly acidic, either the base pigment suspension in the strongly acidic chromium salt solution can be slowly neutralized while precipitating the formed chromium hydroxide into pigment scales, or leaving it to the aqueous base suspension. The chromium salt solution and the base are simultaneously flowed through the pigment so that a pH suitable for the precipitation of chromium hydroxide is maintained in the suspension. The pH in the precipitation above 3, preferably in the range of 4.5 to 9. Any base can be used to adjust the pH. E.g. mention may be made of ammonia (in solution or gaseous), sodium hydroxide or potassium hydroxide. Preferably an 8% solution is used.

In principle, any chromium-ion-containing solution can be precipitated, and this also means hydrolysable chromium-ion complexes, such as an amine complex. Preferably, a solution of chromium chloride or chromium alum is used.

However, the chromium-ion-containing solution can also be prepared in the base pigment suspension by reducing the chromium-ion-containing solution with a suitable reducing agent, such as a hydrosin. E.g. For example, the potassium dichromate and Uydda-avnisulfate solutions may be fed simultaneously to the suspension so that there is still a slight excess of reducing agent in the reaction vessel, or the chromene or Uydda-avisulfate may be in suspension and the other component is added.

Depending on the precipitation method, the precipitation rate is controlled so that only as much chromium trioxide as can be deposited on the pigment surface at each time of application of the layer without further nucleation in the solution. ?

I -J

The precipitation of chromium hydroxide can be carried out at any temperature between the freezing point and the boiling point of the suspension. However, it has been shown that, at relatively low temperatures, precipitation may occur. It is therefore advantageous^dn^{é p}racovat ^por increased^E te^plotě^, e.g. 50 to 100 ° C, especially 60 to 100 ° C ⁹⁰ Deň: 32 ° C. But that^ké at another te^pAs a rule, this precipitation is usually accomplished.

After the desired chromium hydroxide has precipitated, it is stirred for about half an hour, preferably^dat elevated temperature of about 7⁰ ° C and then not^hand slowly flow in the mites^to O^bsahuj^jc: Phosphorous ions. It is then stirred at elevated temperature for a period of time, e.g. about half to an hour, for the reaction to proceed with the chromium hydroxide layer.

Both orthophosphoric acid and its primary, secondary and tertiary salts as well as polymeric phosphates are suitable for the delivery of phosphonate ions. The only requirement is that they can be incorporated in an aqueous solution into a suspension of the chromium hydroxide-coated pigment. In addition to phosphoric acid, for example, KH ^FO ^, Na ^ O O ^ lSSΗ is suitable₂θ, Νβ ^ ΡΟ ^. 12 HgO, Na 2 PgO 2. 7 H 10 and (NaPO 4), *. Irrespective of the type of phosphate ion-containing material, practically the same results are obtained.

The amount of phosphate added is controlled according to the amount of precipitated chromium hydroxide. However, it has been found that a very low phosphate mammonite is already suitable, which will influence the desired pigment gloss improvement. Even with 0.1% phosphate, based on the required stoichiometric amount to produce CrPO4, a considerable improvement is achieved. At about 0.5% phosphate, the effect is already complete. By prolonging the amount of phosphate, the gloss properties of the pigment cannot be further improved, but otherwise there will be no negative effect of a larger amount of phosphate. Up to 100% stoichiometric immunity and even more can be added without adversely affecting the gloss properties of the formulation. At very high phosphate levels, the total amount of phosphate cannot, of course, be absorbed into the layer. In any case, the layer should contain at least 0.05% phosphate, preferably 0.1%.

After coating the base pigment with chromium hydroxide and after treating the ions with the process ions according to the invention, the pigments are obtained in a conventional manner. The reagents are filtered off, washed and dried and calcined. Annealing, which is carried out at a temperature of 600 to 1000 ° C, with an outlet⁷⁰⁰ and^of 900 °) layer ^hy^droxi^din ctoomitéto oúvochií and converted to Uc^gO^. In this calcime, which is usually carried out for half an hour, it turns out that. The pigments according to the invention have a crack-free layer with a very good gloss. In particular, the advantages of the process according to the invention are manifested in such pigments which do not rub a relatively thick layer of chromium trioxide, since these have a particularly high risk of cracking and could not be practically prepared according to known processes with satisfactory gloss. For the first time, pigments coated with a layer of chromium trioxide with good gloss, which can contain, for example, at least 60% CrgO-j, can also be prepared by the process according to the invention. The pigments of the invention should in any case have a content of at least 5% CrO3

The pigments according to the invention can be used as hitherto known pigments, for example as additives to plastics, paints and varnishes, but in particular also in cosmetics. The new pearlescent pigments are generally added in an amount of 0.1 to 80%. Conventional formulations are inadequate. powders, mmat! and chopsticks, e.g. eye shadows, eye shadows, liquid eye shadows and eyeliner preparations, rod-shaped make-up, powder-like make-up, emulsion make-up, oily gel make-up, protective emulsions from light and tanning emulsions, bath foam concentrates with a color lotion and hair lotions. The pearlescent pigments according to the invention are characterized by an intensely green powder coating and an excellent gloss. .

The preparation of some pearlescent pigments according to the invention will be described in the following examples. While other basic pigments can be coated with the same good success, instead of the base pigments used, other variations in the priming conditions described above are also possible. Parts and percentages are by weight unless otherwise stated.

Example 1

To a suspension of 100 g TiOg mica pigment with blue interference color (plate size 10 to ⁶⁰ [mu] m, 5 [deg.] mica, 5 [deg.] m ^{2 1} let the water flow slowly^ipři ⁷⁰ Deň: 32 ° C ^whit- solution of 175 g of KCr / SO4 / gx 12 HgO in 0.6 l of water during 2 hours · Simultaneously with the dosing of 5 »NH4 solution keep the pH of the suspension constant at 6. After about half an hour stirring solution 5 is added. g NagHPO 4. 12 HgO in 100 ml water and stirred for 1 hour

Even at 7 ° C. Then it is filtered,^pThe mixture is washed freely ^při 12⁰ ° C a ^ofíhá se ³⁰ minutes pM

840 Deň: 32 ° C.

To evaluate the gloss, the pigment is sprayed as a 2% suspension into a nitroeeluloza-acrylic resin lacquer and removed on a card on a 500 µm wet film foil and evaluated after drying. The pigment produced according to the example shows a strong green interference color and a sparkling green gloss.

The pigment produced by the wall process, but which has not been coated with phosphate, shows a lower gloss, while the chromium oxide layer hardly contributes to the formation of an interference color.

Example 2 a to g

To a suspension of 10 kg TiOp-dye pigment with a blue interference color (plate size 10 to 60 µm, 49% mica, 51% TiOg) in 200 L water is slowly added (flow rate 2⁰ 1 / h) at 75 °^C rozto^to 17,5 ^kg KCr7SO0 / g. 1^{2 HgO} in ^{80 1} vtdy^, the pH is determined to 6 by the simultaneous addition of a 5% N 4 solution. During the application of the chromium hydroxide layer, aliquots of the suspension are taken after a different time and are separated, however. they are processed in the same way. 0.5 g of NagHPO4 was added to each sample. 12 HgO / g base pigment in pattern^toat, ^pAfter half an hour, filter, wash and dry ^Annealing se ³⁰ minutes at ⁸⁸⁰ Deň: 32 ° C. The following pigments are obtained:

<td>Sample no.</td><td>Chromium oxide layer / g CrgO4 / g base pigment</td>

<td>2 a</td><td> 0,168</td>

<td>2 b</td><td> 0,192</td>

<td>2 c</td><td> 0,222 '</td>

<td>2 d</td><td> 0,231</td>

<td>2 e</td><td> 0,242 .</td>

<td>2 f</td><td> 0,247</td>

<td>2 S</td><td> 0,266</td>

Upon evaluation of the pigments obtained according to the method of Example 1, it appears that all pigments have a good gloss and high color, and with increasing chromium oxide, the interference color shifts towards yellow as it corresponds to the development of optically thick layers.

Přikladla aži *

According to Example 1, pigments were prepared, but using a different min. NajHPO ^. 12 HgO for further treatment. The following table shows the amount of phosphate to be used for the toxic pigments as a percentage of the amount necessary for the stoichiometric reaction to CrPO4.

<td>Sample no.</td><td>Phosphate Quantity</td>

<td>3 e</td><td> 0</td>

<td>3 b</td><td> 0,01 %</td>

<td>3 c</td><td> 0,1 %</td>

<td>2 d</td><td> 0,5 %</td>

<td>3 e</td><td> 1 ,0 %</td>

<td>3 f</td><td> 2,0 %</td>

<td>3 g</td><td> 4,0 %</td>

<td>3 h</td><td> 10,0 %</td>

<td>3 i</td><td> 100,0 %</td>

According to the evaluation of the pigments according to the method of Example 1, it is found that with 0.1% phosphate, the gloss and color of the pigment is already favorably affected, and with 0.5% phosphate the desired green tone and good gloss is achieved and no longer improved.

Example 4 to e

According to Example 1, pigments are prepared, but in contrast to Example 1, phosphate ion-containing substances listed in the following table are used for further phosphoenate treatment. corresponding to 66% of the stoichiometric amount.

Sample no.

ab

CD

e phosphorus compound ⁿ3 ° 4 kh₂fo₄№3 * 04. 12 H₂0 ^Νβ4^Ρ2θ7 · 10 H₂O

When evaluating the pigments according to the method of Example 1, it is found that the pigments have a good gloss and a distinctive color, depending on the type of phosphate compounds used.