GB2043093A - Producing light stable bismuth oxychloride pigment - Google Patents

Abstract

Nacreous ultraviolet light stable bismuth oxychloride is prepared with minimal sintering thereof by heating a pearlescent pigment comprising both nacreous bismuth oxychloride and a particulate refractory material at a temperature of at least about 350 DEG C for a period of time sufficient to stabilize the bismuth oxychloride against ultraviolet light. The refractory material is selected from the group consisting of mica and talc.

Description

SPECIFICATION Improved method for producing light stable bismuth oxychloride pigment This invention relates to nacreous bismuth oxychloride pigments and more particularly to an improved method of preparing an ultraviolet light stable bismuth oxychloride pigment at high temperature and high productivity.

Because it possesses a high index of refraction and is available in pearlescent form, bismuth oxychloride is widely used as a nacreous or pearlescent pigment in cosmetic products such as lipstick, eyeshadow, rouge and nail polish. The principal drawback in the use of nacreous bismuth oxychloride in such cosmetic products is that the material tends to lose its characteristic white color and darkens on exposure to light, particularly ultraviolet light. Several procedures have been employed in an attempt to minimize the tendency of bismuth oxychloride to materially darken on exposure to light. One such procedure involves using special and expensive packaging materials for the product which serve to screen out light. Another common procedure employs the addition of organic ultraviolet light absorbers, such as 2-hydroxybenzophenone, to the bismuth oxychloride pigment.Such a procedure and the materials used therein are described, for example, in U.S. patent 2,974,053. Such additives are expensive, however, and thereby add to the ultimate cost of the cosmetic product.

Piper U.S. patent 3,917,671 describes a process for stabilizing bismuth oxychloride by heating it at a temperature from about 300"C to about 800"C, preferably 400-700"C, for a period of time sufficient to stabilize the pigment. This process is substantially superior to the processes theretofore known in the art. However, under the Piper process it is necessary to avoid excessively high temperatures in order to prevent sintering and consequent agglomeration of the bismuth oxychloride pigment. Where the pigment is sintered, it becomes gritty, loses its lubricity and further suffers a loss of brightness and coverage or hiding power, as may be readily measured, for example, by a standard lacquer drawdown test on a dark background.At the temperatures that can be tolerated the Piper process, heating must be carried out for at least one hour and more typically from 6 to 1 2 hours in order to accomplish ultraviolet light stabilization. The productivity of the Piper process is limited by these relatively extensive heating time requirements.

Among the several objects of the present invention, therefore may be noted the provision of an improved process for preparation of ultraviolet light stable bismuth oxychloride pigments; the provision of such a process wherein such pigments can be prepared with high productivity; the provision of such a process in which such pigments can be prepared without sintering thereof; and the provision of a method for preparing high quality bismuth oxychloride pigments having a high degree of ultraviolet light stability, brightness, pearlescence and coverage.

Briefly, the present invention is directed to a method for the preparation of nacreous ultraviolet light stable bismuth oxychloride with minimal sintering thereof. The method comprises heating a pearlescent pigment comprising both nacreous bismuth oxychloride and a particulate refractory material. The refractory material is selected from the group consisting of a mica and talc. Heating is conducted at a temperature of at least about 350"C for a period of time sufficient to stabilize the bismuth oxychloride against ultraviolet light.

Further objects and features will be in part apparent and in part pointed out hereinafter.

In accordance with the present invention, it has been discovered that the sintering which normally occurs is heating bismuth oxychloride at high temperature, may be avoided where the pigment comprises both bismuth oxychloride and a particulate refractory material such as mica or talc. As a result, the bismuth oxychloride may be stabilized against ultraviolet light by heating at high temperature for relatively brief periods and a substantial improvement in productivity is thereby achieved. Preferably, the refractory material serves as a support on which the bismuth oxychloride is deposited. Surprisingly, however, it has been discovered that the process of the invention is effective and sintering is substantially avoided where the pigment comprises a simple physical mixture or blend of bismuth oxychloride and a particulate refractory material.

In carrying out the method of the invention, the pigment is heated in air at a temperature of at least about 350"C for a time sufficient to stabilize the bismuth oxychloride against ultraviolet light. In order to avoid prolonged heating, the method is preferably conducted at a temperature of at least 500"C. It has been discovered, moreover, that even at temperatures in excess of 800"C no significant sintering of the pigment is experienced. The major advantage attainable by the process of the invention is realized at temperatures about 700"C where stabilization is completed in 3-4 hours, and especially above 800"C where ultraviolet light stabilization can be accomplished in an hour or less with no sintering or agglomeration of pigment.Where the heating temperature is approximately 900-925"C, stability can be achieved in a heating period of one half hour or less. As a consequence, a several fold increase in productivity can be realized by comparison with the Piper process. The maximum permissible temperature in the process of the invention is approximately 950"C, above which thermal decomposition of bismuth oxychlo ride is encountered.

Because of the time/temperature dependence of the ultraviolet light stabilization treatment of bismuth oxychloride, the method of the invention may alternatively be utilized to achieve higher degrees of stability by heating for times comparable to those of the Piper process but at temperatures substantially above those feasible for that process. By proper selection of temperature and time, benefit in both productivity and ultraviolet light stability can be achieved.

The refractory material component of the pigment is preferably the muscovite form of mica.

However, other natural and synthetic micas may also be used. Additionally talc, which has a high level of lubricity and is adapted for cosmetic formulations, can be employed as the refractory component of the pigment. In accordance with the invention, it has been found that no significant detrimental effects on the brightness and stability of the pigment arise from the minor contaminants commonly contained within commercial sources of mica or talc. Thus, for example, mica typically contains iron, whose oxides are strong pigments of red, black or yellow color; but despite the exposure of the mica to oxidation during heating, no significant coloring or darkening of nacreous pigment is encountered in or as a result of the heating process.

Additionally, commercial mica or talc may contain calcium stearate as a lubricant or anti-caking agent. Slight yellowing is observed as a result of pyrolysis of the stearate during the heating process, but the effect is not sufficient to adversely the pearlescence of the pigment for use in cosmetics.

As noted, it is preferred that the particulate refractive material serve as a support upon which the nacreous bismuth oxychloride is deposited. This form is preferred because it avoids the concentration gradients which may occur in a blend, and it is believed that more consistent ultraviolet light stability is thereby achieved. Additionally, though it has been found that the blend is much more resistant to sintering than bismuth oxychloride along, deposit of the bismuth oxychloride on the refractory support provides further insurance against agglomeration, and thus can provide somewhat more consistent hiding power. Also, for the same proportion of bismuth oxychloride, the supported pigment exhibits a somewhat greater brightness.

Deposition of bismuth oxychloride on a refractory substrate may be accomplished by adding a base to an aqueous suspension of the refractory material containing a soluble bismuth salt and an excess of chloride ions to precipitate bismuth oxychloride on the refractory surface. Thus the particulate refractory material may be suspended in a solution of mixed nitric and hydrochloric acid (optionally containing bismuth nitrate), after which another solution of bismuth nitrate in the aforesaid mixed acids and a third solution containing sodium hydroxide are simultaneously added thereto. Such a process is disclosed, for example, in Rands et al. U.S. patent 3,597,250 which is expressly incorporated herein by reference.

The refractory material component of the pigment should typically have an average particle size range of 2 to 100 microns. Preferably 75% by weight of the particulate refractory has a particle size of less than 44 microns and 100% is smaller than 85 microns. Where a blend is prepared, the bismuth oxychloride component should typically have an average particle size range of 2 to 40 microns, with 100% of the bismuth oxychloride being smaller than 44 microns.

In both the case of supported bismuth oxychloride and that of blends, the bismuth oxychloride content of the pigment should be in the range of 10 to 90% by weight. For equivalent brightness, a somewhat higher proportion of bismuth oxychloride is required for the blend than for the supported pigment. Generally, the pigment produced in the method of invention has a low degree of agglomeration, high coverage, high brightness, and excellent ultraviolet light stability.

The following examples illustrate the invention.

Example 1 A pigment consisting of bismuth oxychloride deposited on muscovite and containing approximately 40% by weight bismuth oxychloride was prepared by precipitation of bismuth oxychloride on the muscovite in the manner described below.

The following solutions were prepared: Solution A Bismuth nitrate liquor 51 Baume 1085.3 gm HNO3 52.9 gm HCI 95.2 gm H2O 0.26 liters Solution B H2O 1.7 liters NaOH 333.9 gm Solution C H2O 1.0 liters Mica 417.4 gm HCI 14.2 gm HNO3 24.9 gm Solution C was introduced into a glass vessel and heated to reflux. Thereafter addition of solution A was commenced and continued at a constant rate so that addition thereof was completed in 1 80 minutes. Fifteen minutes after the beginning of the addition of solution A, addition of Solution B was initiated at a constant rate so that addition of the latter solution was completed in the 1 80 minutes.

The reaction mixture was stirred an additional 1 5 minutes and then cooled to 45"C and the product collected by filtration. The product filter cake was washed with water and dried. The pigment produced was of the type that is sold under the trade designation Bi-Lite 20 by Mallinckrodt, Inc. Separate portions of this pigment, each weighing 50 grams, were heated in air in an oven under controlled conditions of temperature and time.

After removal from the oven the reflective properties of each portion of pigment were measured using a standard compressed powder test. Each portion was then exposed to ultraviolet light for 1 6 hours and the reflective properties measured again.

In the compressed powder test, the dry powdered pigment is packed into a 3" compression sample holder equipped with a quartz lens. Measurement of the reflective properties of the compressed powder is carried out using a commercially available reflectance spectrophotometer.

The spectrophotomer is equipped with an 18" reflective integrating sphere and is calibrated with a standard reflecting surface so that the standard gives a tristimulus Y value of 100% under illumination of a standard CIE (Commission Internationale de I'Eclairage) illuminant-C light source.

The tristimulus value Y of each sample was measured on a white background before and after exposure of the dried lacquer to an ultraviolet light source (General Electric F-1 5T8/BLB Black Light) for a period of 1 6 hours at a distance of 6 1/2". The tritimulus Y value is a direct measure of the luminous reflectance relative to the standard reflecting surface. The greater the change in percent Y (t%Y) the greater is the color deterioration of the sample.

Using the methods described above, several additional bismuth oxychloride on mica support pigments were heated for ultraviolet light stablization and tested for the effect of ultraviolet light exposure. The additional pigments included other lots of Bi-Lite 20, a pigment containing 10% bismuth oxychloride on mica sold under the trade designation Ultralite by Mallinckrodt, Inc., a pigment containing 38% by weight bismuth oxychloride and 4% titanium dioxide bonded with calcium stearate on a mica substrate sold under the trade designation Ultrawhite by Mallinckrodt, Inc., a pigment containing 40% by weight bismuth oxychloride and 1% calcium stearate on a mica support sold under the trade designation Ultrapress by Mallinckrodt, Inc. and a pigment containing 40% by weight bismuth oxychloride on a talc support sold under the trade designation Bital by Rona Corporation (Division of E-Merck Darmstadt). The heat treatment conditions and results of the optical tests of this example are set forth in Table 1.

TABLE 1 Heat Treatment Conditions and Compressed Powder Test Results for supported BiOCl Test Conditions Compressed Powder Test Results Before U.V. Exposure After U.V. exposure Table Chromaticity Brightness Chromaticity Brightness Entry Number of Hours No. Material Runs Temp. in Oven x y %Y x y %Y # %Y Bilite 20 1070D-18 Not Fired .3144 .3204 87.2 .3132 .3192 77.8 9.4 368-37 Bilite 20 1070D-18 1 255 C 16 .3165 .3223 83.74 .3154 .3215 80.20 3.54 368-17 Bilite 20 1070D-18 4 525 C 16 .3189 .3256 81.44 .3163 .3233 74.63 6.81 368-29 Bilite 20 1070D-18 1 820 C 16 .3251 .3379 86.2 .3270 .3371 84.4 1.8 Bilite 20 1070D-31 Not Fired .3140 .3201 84.52 368-98 Bilite 20 1070D-31 1 225 C 16 .3171 .3223 82.60 .3147 .3209 78.06 4.54 368-100 Bilite 20 1070D-31 2 525 C 16 .3180 .3254 78.34 .3176 .3249 76.22 2.12 Bilite 20 1070E-9 Not Fired .3137 .3203 83.71 368-98 Bilite 20 1070E-9 2 225 C 16 .3154 .3200 80.67 .3144 .3197 78.36 2.11 368-100 Bilite 20 1070E-9 1 525 C 16 .3186 .3267 79.76 .3187 .3266 78.32 1.44 Bilite 20 1070E-10 Not Fired .3132 .3194 84.6 Ultrawhite EEB Not Fired .3109 .3174 86.06 .3239 .3353 82.36 11.37 368-105 Ultrawhite EEB 1 525 C 16 .3107 .3172 74.68 .3232 .3341 81.12 1.24 Ultrapress DGR Not Fired .3113 .3183 85.65 .3066 .3139 55.33 30.32 368-41 Ultrapress DGR 2 525 C 16 .3223 .3332 80.08 .3213 .3314 77.27 2.81 Ultralite EAY Not Fired .3165 .3229 80.1 .3147 .3209 76.21 3.9 368-41 Ultralite EAY 1 525 C 16 .3219 .3287 72.23 .3218 .3287 71.88 .35 Bital 3181 Not Fired .3125 .3190 88.46 .3115 .3182 75.74 12.72 368-43 Bital 3181 2 525 C 16 .3172 .3256 85.39 .3171 .3244 80.28 5.11 Example 2 A variety of bismuth oxychloride on mica support pigments and also several pigments comprising a blend of bismuth oxychloride and mica containing 40% by weight bismuth oxychloride were heated for ultraviolet light stabilization, exposed to ultraviolet light, and subjected to optical tests. The methods used for ultraviolet light stabilization and ultraviolet light exposure were as described in Example 1. However, the optical tests utilized in the demonstration runs in this example were lacquer drawdown tests rather than compressed powder tests.

In the lacquer drawdown test a lacquer suspension is prepared containing 10% by weight of the pigment in a conventional nail lacquer solution comprising nitrocellulose, resins and plasticizers, and a solvent comprising acetone, dibutyl phthalate, toluene and butyl alcohol. The lacquer is then applied to a standard test card. One portion of the card surface is white and another portion is black so that measurements of the properties of the lacquer can be obtained on both types of background.

In the runs of this example, measurement of the reflective properties was carried out using another commercially available reflectance spectrophotometer which was equipped with an 8" reflective integrating sphere and was also calibrated with a standard reflecting surface so that the standard gave a tristimulus Y value of 100% under illumination of a standard CIE illuminant-C light source.

Heat treatment conditions and results of the tests of this example are set forth in Table 2. TABLE II Heat Treatment Conditions and Lacquer Drawdown Test Results for Supported BiOCl Test Conditions Lacquer Drawdown Test Results Before U.V. Exposure After U.V. exposure Table Chromaticity Brightness Chromaticity Brightness Entry Number of Hours No.Material Runs Temp. in Oven x y %Y x y %Y # %Y %Y# Bilite 20 1070E-10 Not Fired .3234 .3304 81.90 .3085 .3165 29.90 52.06 32.96 368-34 Bilite 20 1070D-18 3 425 C 4 .3237 .3308 80.71 .3073 .3155 29.10 51.61 33.99 368-34 Bilite 20 1070D-18 4 425 C 16 .3240 .3311 80.08 .3070 .3153 27.63 52.43 34.78 368-34 Bilite 20 1070D-18 1 425 C 64 .3246 .3321 80.26 .3158 .3239 46.40 33.78 34.47 368-34 Bilite 20 1070D-18 2 425 C 8 .3239 .3309 80.41 .3059 .3140 26.71 53.70 33.78 368-17 Bilite 20 1070D-18 3 525 C 4 .3244 .3317 80.30 .3167 .3247 54.24 26.06 32.75 368-17 Bilite 20 1070D-18 2 525 C 8 .3249 .3325 80.47 .3204 .3283 63.61 17.13 32.58 368-17 Bilite 20 1070D-18 4 525 C 16 .3257 .3337 81.42 .3222 .3302 67.21 14.21 32.71 368-175 Bilite 20 1070E-10 1 550 C 16 .3251 .3330 80.73 .3241 .3318 72.56 8.17 25.29 368-17 Bilite 20 1070D-18 6 650 C 4 .3252 .3335 82.03 .3218 .3304 65.53 16.50 24.75 368-27 Bilite 20 1070D-18 3 725 C 4 .3274 .3378 81.45 .3288 .3392 78.64 2.81 11.78 368-27 Bilite 20 1070D-18 2 725 C 8 .3285 .3398 81.38 .3305 .3416 79.61 1.77 11.30 368-164 Bilite 20 1070E-10 1 850 C 1/2 hr. .3262 .3344 81.17 .3254 .3338 70.59 10.58 14.32 368-164 Bilite 20 1070E-10 2 850 C 1 .3284 .3375 80.48 .3289 .3380 77.20 3.28 12.34 368-165 Bilite 20 1070E-10 1 900 C 1/4 hr. .3280 .3369 80.59 .3270 .3362 70.42 10.17 12.88 368-165 Bilite 20 1070E-10 2 900 C 1/2 hr. .3294 .3389 80.11 .3303 .3398 77.23 2.88 11.82 368-171 Bilite 20 1070E-10 1 950 C 1/4 hr. .3316 .3409 79.31 .3328 .3423 77.55 1.75 12.11 368-168 Blend Not Fired .3265 .3339 80.06 .3148 .3232 32.98 47.08 20.14 368-175 Blend 368-168 2 550 C 16 .3334 3407 75.94 .3341 .3414 71.67 4.27 19.12 368-169 Blend 368-168 850 C 1 .3322 .3417 79.22 .3335 .3431 77.61 1.61 16.78 368-170 Blend 368-168 900 C 1/2 hr..3320 .3416 79.29 .3332 .3426 77.66 1.63 11.03 368-171 Blend 368-168 2 950 C 1/4 hr. .3289 .3383 80.97 .3295 .3389 77.51 3.46 10.52 Ultrapress DGR Not Fired .3203 .3273 82.26 .3118 .3194 41.34 40.92 25.86 368-41 Ultrapress DGR 2 525 C 16 .3267 .3367 80.59 .3269 .3369 77.24 3.31 33.48 Bital 3181 Not Fired .3212 .3286 82.79 .3182 .3259 55.42 27.37 26.18 368-43 Bital 3181 2 525 C 16 .3231 .3309 81.86 .3246 .3323 77.71 4.15 16.50 #Information obtained by reading black section of 10% drawdowns not exposed.

As indicated in Table 2, the optical tests of this example included measurements of %Y on a black surface before exposure to ultraviolet light. Lacquer drawdown tests and measurements of %Y on the black surface provide both quantitative and observational data relating to the extent of sintering and agglomeration. From visual observation, the sintering encountered was minimal in all cases. This was confirmed by the quantitative tests which showed that reflectance was consistently greater than 10% on a black surface, a degree of reflectance which is generally not achievable where there is significant agglomeration of pigment particles.

In the view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above methods and products without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

Claims (9)

1. A method for the preparation of nacreous ultraviolet light stable bismuth oxychloride with minimal sintering thereof comprising heating a pearlescent pigment comprising both nacreous bismuth oxychloride and a particulate refractory material selected from the group consisting of a mica and talc at a temperature of at least about 350"C for a period of time sufficient to stabilize the bismuth oxychloride against ultraviolet light.

2. A method as set forth in claim 1 wherein said pigment is heated at a temperature of between about 800"C and about 950"C.

3. A method as set forth in claim 1 wherein said pigment is heated at a temperature sufficient so that the bismuth oxychloride is stabilized against ultraviolet light after less than about one hour of heating.

4. A method as set forth in claim 1 wherein said pigment comprises bismuth oxychloride deposited on a support comprising said particulate refractory material.

5. A method as set forth in claim 4 wherein said support comprises mica.

6. A method as set forth in claim 5 wherein said pigment comprises between about 10% by 90% weight of said bismuth oxychloride.

7. A method as set forth in claim 6 wherein said pigment has an average particle size of between about 2 and about 100 microns both before and after heating of said pigment.

8. A method as set for in claim 7 wherein, after heating, at least 75% by weight of said pigment has a particle size of less than about 44 microns.

9. A method as set forth in claim 1 wherein said support comprises talc.