The adherence of microorganisms on surfaces is unwanted, particularly in the case of pathogenic microorganisms. Adhering microorganisms frequently lead to infections or to reinfections in humans, animals, and plants.
Moreover, delicate textiles, such as silk microfibers, are more frequently used in clothing, and may be washed only at 30 or 40° C. Consequently, fungi, such as the human pathogen Candida albicans, are not destroyed during the washing procedure.
In addition to the lower washing temperatures, liquid washing agents generally free of bleaching agents are also commonly used. For 60° C. washing conditions, as was previously considered typical, nearly all germs were reliably killed off, firstly by the higher temperature, secondly by the bleaching agent typically found in washing agents.
As a consequence of the modified washing conditions more commonly found today, textiles contaminated with viruses, bacteria, mold fungi or yeast fungi cannot be made germ-free to the point where re-infection of the consumer from renewed contact of the with the supposedly clean laundry is prevented.
In addition, problems with bad odors can occur because residual germs proliferate on the washing in the course of drying, wearing or storing and produce malodorous metabolites. Moreover, biofilms that adhere to the interior of a washing machine can cause unpleasant odors.
Antimicrobially active compositions and their use in washing, cleaning, after treatment or auxiliary washing agents are known from the prior art. The added disinfectants frequently involve halogen-containing substances or phenol derivatives or other aromatic hydrocarbons that may be a problem for environmental sustainability. Other more compatible microbiocides have only a limited activity spectrum, or are only effective under certain physical conditions. For domestic applications, however, there is a great need for antimicrobial compositions effective against a broad spectrum of microorganisms and are environmentally friendly and preferably of natural origin.
Silver or silver ions possess antimicrobial efficacy and perform, inter alia, blocking of thiol enzymes in microorganisms resulting in high bactericidal, germicidal, and fungicidal action. Germ-reducing washing, cleaning, after treatment, and auxiliary washing agents comprising silver and/or silver ions are known in the prior art, for example as disclosed in EP 1 670 885 A1.
However, compositions that comprise silver and/or silver ions are often unstable since the silver ions comprised in the agents can react with impurities such as chloride ions to form light-sensitive silver chloride salts or with sulfide to form poorly soluble silver sulfide salts. In a (strongly) alkaline medium, soluble silver ions initially react to form AgOH and then react further to form sparingly soluble Ag2O. In addition to the poor solubility of these silver salts, the silver oxides and silver sulfides, in spite of their trace quantities, lead to considerable color changes, in particular a brown or black coloration, of the composition.
Accordingly, it is desirable to provide a stable, antibacterial auxiliary washing agent based on silver or silver ions.