Abstract: The present invention is concerned with a dye system for application to a substrate, the dye system comprising: (a) at least one dye precursor; (b) an oxidizing agent; and (c) a catalyst, wherein the catalyst is a homogeneous catalyst or a heterogeneous catalyst. Preferably, the catalyst comprises at least one metal-containing compound. The invention also envisages a method for the coloration of a substrate, the method comprising treating the substrate with the dye system of the invention. In preferred embodiments of the invention, the substrate comprises human hair, natural or synthetic polymers, or textile fibers. In further preferred embodiments, the at least one dye precursor is an organic precursor, the at least one metal derivative for use as a catalyst comprises at least one inorganic metal compound or at least one metal complex comprising at least one organic ligand, and the oxidizing agent is hydrogen peroxide.

Abstract: The present invention is concerned with a dye system for application to a substrate, the dye system comprising: (a) at least one dye precursor; (b) an oxidising agent; and (c) a catalyst, wherein the catalyst is a homogeneous catalyst or a heterogeneous catalyst. Preferably, the catalyst comprises at least one metal-containing compound. The invention also envisages a method for the coloration of a substrate, the method comprising treating the substrate with the dye system of the invention. In preferred embodiments of the invention, the substrate comprises human hair, natural or synthetic polymers, or textile fibres. In further preferred embodiments, the at least one dye precursor is an organic precursor, the at least one metal derivative for use as a catalyst comprises at least one inorganic metal compound or at least one metal complex comprising at least one organic ligand, and the oxidising agent is hydrogen peroxide.

Abstract: The present invention provides a catalyst for use in the preparation of a coloured polymeric material, said catalyst comprising a coloured organometallic compound. Preferably, said catalyst comprises a metal such as aluminium and at least one organic chromophore, such as an azo chromophore, said chromophore being either directly bonded to said metal, or indirectly bonded to said metal through a ligand. The invention also envisages a method for the preparation of a coloured polymer, the method comprising performing a polymerisation reaction in the presence of such a catalyst. The method is particularly applicable to the preparation of poly(lactic acid), and offers significant benefits over the processes of the prior art, both economically and environmentally.