Spray-dried dye compositions, process for the production and use thereof

Abstract

The invention relates to spray-dried, washfast dye compositions (preferably in the form of pigment powders) having a bleeding rate of ≤0.5% and consisting of water-soluble functional dyes, preferably food dyes, which are firmly incorporated in a silica matrix. Apart from low bleeding of dye, these compositions are remarkable for their high stability to pH changes and/or ascorbic acid. The invention is also directed to the production of the dye compositions and the use thereof. The dye compositions are preferably employed in coloring foods, cosmetics, pharmaceutical products, but also in other uses.

1 . Spray-dried dye compositions consisting of water-soluble functional dyes incorporated in an organosilane-based silicon dioxide matrix with bleeding rates of ≤1.5%. 
     
     
         2 . The spray-dried dye compositions according to  claim 1 , produced by the following steps:
 a) producing a silicon dioxide sol by weak acid hydrolysis of alkoxysilanes (organosilanes) in an aqueous organic solvent mixture at a pH of 5 to 6.5;   b) adding a water-soluble dye;   c) spray-drying the dyed sol to cause condensation of the SiO x  sol particles and encapsulation of the dye molecules;   d) optionally subsequent temperature treatment for several hours at temperatures above 50° C. over a time period of at least 2 hours.   
     
     
         3 . The dye compositions according to  claim 1 , characterized in that the incorporated dyes are stable to pH and/or ascorbic acid. 
     
     
         4 . The dye compositions according to  claim 1  or  2 , characterized in that the particle size thereof is 0.01 to 100 μm. 
     
     
         5 . A process for the production of spray-dried dye compositions according to any of  claims 1  to  4 , comprising the steps of
 a) producing a silicon dioxide sol by weak acid hydrolysis of alkoxysilanes (organosilanes) in an aqueous organic solvent mixture at a pH of 5 to 6.5; 
 b) adding a water-soluble dye; 
 c) gelling by spray-drying the dyed sol. 
 
     
     
         6 . The process according to  claim 5 , characterized in that the resulting compositions after the spray-drying process are subjected to
 d) a temperature treatment for several hours, at least 2 hours, at a temperature above 50° C.   
     
     
         7 . The process according to any of  claim 5  or  6 , characterized in that the temperature treatment is carried out at temperatures of from 50° C. to 300° C., preferably at temperatures of from 70° C. to 150° C. 
     
     
         8 . The process according to  claim 6  or  7 , characterized in that the temperature treatment is carried out for a time period of 2 to 120 hours, preferably is for a time period of 5 to 48 hours. 
     
     
         9 . The process according to any of  claims 5  to  8 , characterized in that hydrolysis is effected by heterogeneous catalysis, preferably with addition of acidic ion exchangers. 
     
     
         10 . The process according to any of  claims 5  to  9 , characterized in that the mixture fed into the spray-drying process contains no further additives. 
     
     
         11 . The process according to any of  claims 5  to  10 , characterized in that the water-soluble functional dyes are natural or synthetic food dyes used in food products, oral pharmaceutical preparations or cosmetics. 
     
     
         12 . Use of the dye particles according to any of  claims 1  to  11  in foods, in pharmaceutical applications and beauty culture.