Tungsten Oxide-Mica Photochromic Pearlescent Pigments

Pearlescent pigments consist of metal oxide coated mica. Because of their excellent chemical corrosion resistance and high temperature resistance, pearlescent pigments have been widely used in building decoration, ink, automotive paint, textile printing and other fields. So far, the mature pearlescent pigments are titanium oxide (titanium dioxide) / tin oxide (SnO₂) / iron oxide (Fe₂O₃) - mica pearlescent pigments.

At present, tungsten oxide photoluminescent materials generally have some problems, such as slow light response, low photochromic efficiency, poor reversibility and the need to use ultraviolet light source, which greatly affect their practical application prospects. In order to overcome the shortcomings in the application of tungsten oxide photoluminescent materials in the existing technology, a preparation method of tungsten oxide-mica photochromic pearlescent pigments was proposed.

1)The soluble sodium tungstate is weighed and added into deionized water. The water solution of sodium tungstate is obtained by stirring for 50-70 minutes at 400-1500 rpm. The molar concentration of the water solution of sodium tungstate is 0.001-1.0M.

2)Mica base of micron scale was added to the aqueous solution of sodium tungstate, and suspension A was obtained by stirring for 25-35 minutes at 400-1500 rpm. The molar concentration of the mica base in suspension A was 0.001-1.0M.

3)The water-soluble organic matter was added into suspension A and stirred for 2-26 hours at 400-800 rpm to obtain suspension B. The molar concentration of the water-soluble organic matter in suspension B was 0.005-0.100M.

4)Inorganic acids are slowly added to suspension B drop by drop under stirring condition, and the pH of suspension B is adjusted to 0.1-2. Suspension C is obtained by stirring for 4 hours at 400-800 rpm. The molar concentration of the inorganic acids in suspension C is 0.010-5.0M.

5)After the reaction, suspension C was centrifuged for solid-liquid separation, and the lower solids were collected and added to alcohol for ultrasonic cleaning. The lower solids were collected by centrifugation and repeated for 3-5 times. The lower solids were collected by ultrasonic cleaning with deionized water once and centrifugation. Tungsten oxide-mica photochromic pearlescent pigments could be obtained by drying the products in a constant temperature environment.

Mica has good stability and low price. The combination of tungsten oxide and mica not only improves the added value of traditional pigments, but also provides a good carrier for the application of tungsten oxide photochromic materials. The photochromic materials are organically combined with traditional pigments to synthesize micron tungsten oxide-mica photochromic pearlescent pigments. The photochromic effect is very good. It is irradiated by ultraviolet lamp for a few minutes. Photochromic reaction appeared in the clock, which was much better than the traditional tungsten oxide powder. At the same time, the photochromism has good reversibility, and the original color can be restored within a short time after evacuation of the ultraviolet lamp.

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