Composition and method for bleaching a substrate
View Patent ↗The invention relates to catalytically bleaching substrates, especially laundry fabrics, with atmospheric oxygen and a peroxyl species. A method of bleaching a substrate is provided that comprises applying to the substrate, in an aqueous medium, a specified organic substance which forms a complex with a transition metal, the complex catalysing bleaching of the substrate by atmospheric oxygen and a peroxyl species. Also provided is a bleaching composition comprising, in an aqueous medium, atmospheric oxygen and an organic substance which forms a complex with a transition metal, the complex catalysing bleaching of the substrate by the atmospheric oxygen, wherein the aqueous medium is provided with a peroxygen bleach or a peroxy-based or peroxy-generating bleach system.
1. A method of bleaching a substrate in an aqueous solution during a wash which comprises the steps of:
providing a concentration of a peroxyl species in the aqueous solution for bleaching tea type stains optionally with a transition metal catalyst that further activates hydrogen peroxide;
providing an amount of oxygen bleaching catalyst to the wash together with oxygen dissolved in the aqueous solution;
reducing the concentration of peroxyl species in the aqueous solution for increasing the amount of oxygen bleaching catalyst available for oxygen bleaching in the wash.
2. A method of bleaching a substrate in an aqueous solution according to claim 1 , wherein in the aqueous medium the [(oxygen species-complex]/[peroxyl species-complex] is between 10 and 0.1 at a point in time during the wash.
3. A method of bleaching a substrate in an aqueous solution according to claim 1 , wherein in the aqueous medium the [O 2 ]/[total peroxyl present] is in the range 10 and 0.1 at a point in time during the wash.
4. A method of bleaching a substrate in an aqueous solution according to claim 1 , wherein that wash is at a temperature of between 10° C. and 45° C.