GB850449A - Colored nacreous materials and method for production thereof - Google Patents

Abstract

Nacreous particulate material such as pearl essence lead sub-carbonate, bismuth oxychloride, &c., is coloured by suspending individual particles of the material in a liquid medium and precipitating colouring matter on them in situ, the rate of precipitation being controlled so that precipitated colouring matter is deposited directly on the individual particles without destroying their characteristic geometry. Precipitation may be effected by the addition to the liquid suspension of dilute solutions e.g. of approximately 0,1% to 10% concentration, of two chemical reagents or a second reagent may be added continuously or incrementally, after the first. The coloured nacreous material may be included in surface coating compositions such as paints, nitrocellulose lacquers, fingernail polishes in the proportion of up to 10% of the total weight, in plastics by addition to the ingredients prior to polymerization thereof, and may be employed in the manufacture of leather wearing apparel. According to an example, crystals of natural pearl essence were suspended in 10 c.c. ethyl acetate and the suspension was then stirred into a solution of 1,13 g. thioacetamide in 65 c.c. ethyl acetate. A solution of 1,1g. chlorauric acid tri-hydrate in 40 c.c. ethyl acetate was added dropwise with stirring to the suspension of pearl essence containing the dissolved thioacetamide, the rate of dropwise addition being regulated so that substantially all of the aurous thioacetamide precipitate deposited on the suspended pearl essence as it was formed. 25 c.c. pyridine was added to the stirred suspension and the reaction mixture was heated on a water bath at 90 DEG C. for about 10 minutes. The reaction mixture was centrifuged, the precipitate was washed first with methanol and then with ethyl acetate. The washed product imparted an attractive greenish-gold colour, exhibiting the characteristic pearly lustre of the original pearl essence, to a fingernail lacquer in which it was suspended. A further example is directed to making a silvery-grey coloured nacreous product by precipitating on to nacreous particles, at a pH of about 7,5, metallic gold by reaction between hydroxylamine and chlorauric acid both in methanolic solution. In other examples, the following substances respectively were precipitated on to the nacreous particles: cadmium, manganese, antimony and iron sulphides; mixed antimony and iron sulphides; mixed antimony, iron and tin sulphides; mixed tin and cadmium sulphides; mixed tin and iron sulphides; nickel dimethyl glyoxime; palladiumdimethyl glyoxime; palladium furil dioxime; silver; and phosphomolybdate-dye complexes.ALSO:Nacreous particulate material such as pearl essence, lead subcarbonate, bismuth oxychloride, mercurous chloride, talc, brucite, stilbite &c., is coloured by suspending individual particles of the material in a liquid medium and precipitating colouring matter on them in situ, the rate of precipitation being controlled so that precipitated colouring matter is deposited directly on the individual particles without destroying their characteristic geometry. Precipitation may be effected by the addition to the liquid suspension of dilute solutions e.g. of approximately 0.1% to 10% concentration, of two chemical reagents or a second reagent may be added continuously or incrementally after the first. According to an example, a bright yellow coloured nacreous product was made by precipitating on to nacreous particles palladium dimethyl glyoxime by adding dropwise to a suspension of the nacreous particles containing a methanolic solution of dimethyl glyoxime and 2-amino-2-methyl-1-propanol, palladium chloride in a solution of hydrochloric acid and methanol. Examples of other metal compounds which may be precipitated on the nacreous materials relate to aurous thioacetamide by reaction between thioacetamide and chlorauric acid trihydrate, cadmium, manganese, antimony, iron and tin sulphides and mixed sulphides, nickel dimethyl glyoxime by reaction between nickel chloride and dimethyl glyoxime, and palladium furil dioxime.